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Sullivan, Beth Ann

Overview:

Research in the Sullivan Lab is focused on chromosome organization, with a specific emphasis on the genomics and epigenetics of the chromosomal locus called the centromere and the formation and fate of chromosome abnormalities that are associated with birth defects, reproductive abnormalities, and cancer. The centromere is a specialized chromosomal site involved in chromosome architecture and movement, kinetochore function, heterochromatin assembly, and sister chromatid cohesion. Our experiments have uncovered a unique type of chromatin (CEN chromatin) formed exclusively at the centromere by replacement of core histone H3 by the centromeric histone variant CENP-A. We are exploring the composition of CEN chromatin, its relationship to the underlying alpha satellite DNA at the centromere, and the dynamics of CENP-A loading and distribution during mitosis. Recently, we discovered that the amount of genomic variation within alpha satellite DNA correlates with where a centromere is formed and affects how stable the chromosome is. Variation within the repetitive portion of the human genome has not been well studied, primarily because alpha satellite DNA is part of the 10% of the human genome that has been excluded from the contiguous genome assembly. We are currently using endogenous chromosomes and human artificial chromosomes (HACs) to investigate how alpha satellite variation affects centromeric transcription, recruitment of centromere proteins, de novo centromere assembly, kinetochore architecture, and ultimately, chromosome stability. Finally, the lab studies human chromosomal abnormalities with two centromeres, called dicentric chromosomes. Originally described by Barbara McClintock in the 1930s, dicentrics have been considered inherently unstable chromosomes that trigger genome instability. However, dicentric chromosomes in humans are very stable and are often transmitted through multigenerational families. We have observed that some dicentrics undergo inactivation of one centromere while other dicentrics retain two active centromeres without a loss in chromosome stability. Using several approaches to experimentally produce dicentric chromosome rearrangements in human cells, we are exploring dicentric formation and fate, including the molecular basis of centromere inactivation, by using genome engineering (CRISPR), live cell imaging, and quantitative microscopy.

Positions:

Associate Professor of Molecular Genetics and Microbiology

Molecular Genetics and Microbiology
School of Medicine

Member of the Duke Cancer Institute

Duke Cancer Institute
School of Medicine

Education:

Ph.D. 1995

Ph.D. — University of Maryland - Baltimore

News:

Grants:

Dicentric chromosome formation and stability in humans

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
May 01, 2012
End Date
February 28, 2017

Genomic and Epigenetic Mechanisms of Human Centromere Assembly and Chromosome Stability

Administered By
Molecular Genetics and Microbiology
AwardedBy
March of Dimes
Role
Principal Investigator
Start Date
June 01, 2013
End Date
May 31, 2016

Mechanisms of Centromere Function

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
August 11, 2010
End Date
August 10, 2013

Mechanisms of Human Chromosome Rearrangement and Stability

Administered By
Molecular Genetics and Microbiology
AwardedBy
March of Dimes
Role
Principal Investigator
Start Date
June 01, 2010
End Date
May 31, 2013

Organization and Regulation of Eukaryotic Centromeres

Administered By
Molecular Genetics and Microbiology
AwardedBy
National Institutes of Health
Role
Principal Investigator
Start Date
September 01, 2005
End Date
January 31, 2010

Epigenetic Determinants of Centromere Function and Stability in Human Dicentric Chromosomes

Administered By
Molecular Genetics and Microbiology
AwardedBy
March of Dimes
Role
Principal Investigator
Start Date
June 01, 2006
End Date
May 31, 2009

Organization and Stability of Centromeric Chromatin

Administered By
Molecular Genetics and Microbiology
AwardedBy
March of Dimes Birth Defects Foundation
Role
Principal Investigator
Start Date
September 01, 2005
End Date
July 31, 2006
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Publications:

Human centromere repositioning within euchromatin after partial chromosome deletion.

Centromeres are defined by a specialized chromatin organization that includes nucleosomes that contain the centromeric histone variant centromere protein A (CENP-A) instead of canonical histone H3. Studies in various organisms have shown that centromeric chromatin (i.e., CENP-A chromatin or centrochromatin) exhibits plasticity, in that it can assemble on different types of DNA sequences. However, once established on a chromosome, the centromere is maintained at the same position. In humans, this location is the highly homogeneous repetitive DNA alpha satellite. Mislocalization of centromeric chromatin to atypical locations can lead to genome instability, indicating that restriction of centromeres to a distinct genomic position is important for cell and organism viability. Here, we describe a rearrangement of Homo sapiens chromosome 17 (HSA17) that has placed alpha satellite DNA next to euchromatin. We show that on this mutant chromosome, CENP-A chromatin has spread from the alpha satellite into the short arm of HSA17, establishing a ∼700 kb hybrid centromeric domain that spans both repetitive and unique sequences and changes the expression of at least one gene over which it spreads. Our results illustrate the plasticity of human centromeric chromatin and suggest that heterochromatin normally constrains CENP-A chromatin onto alpha satellite DNA. This work highlights that chromosome rearrangements, particularly those that remove the pericentromere, create opportunities for centromeric nucleosomes to move into non-traditional genomic locations, potentially changing the surrounding chromatin environment and altering gene expression.

Authors
Sullivan, LL; Maloney, KA; Towers, AJ; Gregory, SG; Sullivan, BA
MLA Citation
Sullivan, LL, Maloney, KA, Towers, AJ, Gregory, SG, and Sullivan, BA. "Human centromere repositioning within euchromatin after partial chromosome deletion." Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology 24.4 (December 2016): 451-466.
PMID
27581771
Source
epmc
Published In
Chromosome Research
Volume
24
Issue
4
Publish Date
2016
Start Page
451
End Page
466

Genomic variation within alpha satellite DNA influences centromere location on human chromosomes with metastable epialleles.

Alpha satellite is a tandemly organized type of repetitive DNA that comprises 5% of the genome and is found at all human centromeres. A defined number of 171-bp monomers are organized into chromosome-specific higher-order repeats (HORs) that are reiterated thousands of times. At least half of all human chromosomes have two or more distinct HOR alpha satellite arrays within their centromere regions. We previously showed that the two alpha satellite arrays of Homo sapiens Chromosome 17 (HSA17), D17Z1 and D17Z1-B, behave as centromeric epialleles, that is, the centromere, defined by chromatin containing the centromeric histone variant CENPA and recruitment of other centromere proteins, can form at either D17Z1 or D17Z1-B. Some individuals in the human population are functional heterozygotes in that D17Z1 is the active centromere on one homolog and D17Z1-B is active on the other. In this study, we aimed to understand the molecular basis for how centromere location is determined on HSA17. Specifically, we focused on D17Z1 genomic variation as a driver of epiallele formation. We found that D17Z1 arrays that are predominantly composed of HOR size and sequence variants were functionally less competent. They either recruited decreased amounts of the centromere-specific histone variant CENPA and the HSA17 was mitotically unstable, or alternatively, the centromere was assembled at D17Z1-B and the HSA17 was stable. Our study demonstrates that genomic variation within highly repetitive, noncoding DNA of human centromere regions has a pronounced impact on genome stability and basic chromosomal function.

Authors
Aldrup-MacDonald, ME; Kuo, ME; Sullivan, LL; Chew, K; Sullivan, BA
MLA Citation
Aldrup-MacDonald, ME, Kuo, ME, Sullivan, LL, Chew, K, and Sullivan, BA. "Genomic variation within alpha satellite DNA influences centromere location on human chromosomes with metastable epialleles." Genome research 26.10 (October 2016): 1301-1311.
PMID
27510565
Source
epmc
Published In
Genome research
Volume
26
Issue
10
Publish Date
2016
Start Page
1301
End Page
1311

Inheritance of the CENP-A chromatin domain is spatially and temporally constrained at human centromeres.

Chromatin containing the histone variant CENP-A (CEN chromatin) exists as an essential domain at every centromere and heritably marks the location of kinetochore assembly. The size of the CEN chromatin domain on alpha satellite DNA in humans has been shown to vary according to underlying array size. However, the average amount of CENP-A reported at human centromeres is largely consistent, implying the genomic extent of CENP-A chromatin domains more likely reflects variations in the number of CENP-A subdomains and/or the density of CENP-A nucleosomes within individual subdomains. Defining the organizational and spatial properties of CEN chromatin would provide insight into centromere inheritance via CENP-A loading in G1 and the dynamics of its distribution between mother and daughter strands during replication.Using a multi-color protein strategy to detect distinct pools of CENP-A over several cell cycles, we show that nascent CENP-A is equally distributed to sister centromeres. CENP-A distribution is independent of previous or subsequent cell cycles in that centromeres showing disproportionately distributed CENP-A in one cycle can equally divide CENP-A nucleosomes in the next cycle. Furthermore, we show using extended chromatin fibers that maintenance of the CENP-A chromatin domain is achieved by a cycle-specific oscillating pattern of new CENP-A nucleosomes next to existing CENP-A nucleosomes over multiple cell cycles. Finally, we demonstrate that the size of the CENP-A domain does not change throughout the cell cycle and is spatially fixed to a similar location within a given alpha satellite DNA array.We demonstrate that most human chromosomes share similar patterns of CENP-A loading and distribution and that centromere inheritance is achieved through specific placement of new CENP-A near existing CENP-A as assembly occurs each cell cycle. The loading pattern fixes the location and size of the CENP-A domain on individual chromosomes. These results suggest that spatial and temporal dynamics of CENP-A are important for maintaining centromere identity and genome stability.

Authors
Ross, JE; Woodlief, KS; Sullivan, BA
MLA Citation
Ross, JE, Woodlief, KS, and Sullivan, BA. "Inheritance of the CENP-A chromatin domain is spatially and temporally constrained at human centromeres." Epigenetics & chromatin 9 (January 2016): 20-.
Website
http://hdl.handle.net/10161/12389
PMID
27252782
Source
epmc
Published In
Epigenetics and Chromatin
Volume
9
Publish Date
2016
Start Page
20
DOI
10.1186/s13072-016-0071-7

Neocentromeres: a place for everything and everything in its place.

Centromeres are essential for chromosome inheritance and genome stability. Centromeric proteins, including the centromeric histone centromere protein A (CENP-A), define the site of centromeric chromatin and kinetochore assembly. In many organisms, centromeres are located in or near regions of repetitive DNA. However, some atypical centromeres spontaneously form on unique sequences. These neocentromeres, or new centromeres, were first identified in humans, but have since been described in other organisms. Neocentromeres are functionally and structurally similar to endogenous centromeres, but lack the added complication of underlying repetitive sequences. Here, we discuss recent studies in chicken and fungal systems where genomic engineering can promote neocentromere formation. These studies reveal key genomic and epigenetic factors that support de novo centromere formation in eukaryotes.

Authors
Scott, KC; Sullivan, BA
MLA Citation
Scott, KC, and Sullivan, BA. "Neocentromeres: a place for everything and everything in its place." Trends Genet 30.2 (February 2014): 66-74. (Review)
PMID
24342629
Source
pubmed
Published In
Trends in Genetics
Volume
30
Issue
2
Publish Date
2014
Start Page
66
End Page
74
DOI
10.1016/j.tig.2013.11.003

The past, present, and future of human centromere genomics.

The centromere is the chromosomal locus essential for chromosome inheritance and genome stability. Human centromeres are located at repetitive alpha satellite DNA arrays that compose approximately 5% of the genome. Contiguous alpha satellite DNA sequence is absent from the assembled reference genome, limiting current understanding of centromere organization and function. Here, we review the progress in centromere genomics spanning the discovery of the sequence to its molecular characterization and the work done during the Human Genome Project era to elucidate alpha satellite structure and sequence variation. We discuss exciting recent advances in alpha satellite sequence assembly that have provided important insight into the abundance and complex organization of this sequence on human chromosomes. In light of these new findings, we offer perspectives for future studies of human centromere assembly and function.

Authors
Aldrup-Macdonald, ME; Sullivan, BA
MLA Citation
Aldrup-Macdonald, ME, and Sullivan, BA. "The past, present, and future of human centromere genomics." Genes 5.1 (January 2014): 33-50.
Website
http://hdl.handle.net/10161/9508
PMID
24683489
Source
epmc
Published In
Genes
Volume
5
Issue
1
Publish Date
2014
Start Page
33
End Page
50
DOI
10.3390/genes5010033

Nucleolar organization, ribosomal DNA array stability, and acrocentric chromosome integrity are linked to telomere function.

The short arms of the ten acrocentric human chromosomes share several repetitive DNAs, including ribosomal RNA genes (rDNA). The rDNA arrays correspond to nucleolar organizing regions that coalesce each cell cycle to form the nucleolus. Telomere disruption by expressing a mutant version of telomere binding protein TRF2 (dnTRF2) causes non-random acrocentric fusions, as well as large-scale nucleolar defects. The mechanisms responsible for acrocentric chromosome sensitivity to dysfunctional telomeres are unclear. In this study, we show that TRF2 normally associates with the nucleolus and rDNA. However, when telomeres are crippled by dnTRF2 or RNAi knockdown of TRF2, gross nucleolar and chromosomal changes occur. We used the controllable dnTRF2 system to precisely dissect the timing and progression of nucleolar and chromosomal instability induced by telomere dysfunction, demonstrating that nucleolar changes precede the DNA damage and morphological changes that occur at acrocentric short arms. The rDNA repeat arrays on the short arms decondense, and are coated by RNA polymerase I transcription binding factor UBF, physically linking acrocentrics to one another as they become fusogenic. These results highlight the importance of telomere function in nucleolar stability and structural integrity of acrocentric chromosomes, particularly the rDNA arrays. Telomeric stress is widely accepted to cause DNA damage at chromosome ends, but our findings suggest that it also disrupts chromosome structure beyond the telomere region, specifically within the rDNA arrays located on acrocentric chromosomes. These results have relevance for Robertsonian translocation formation in humans and mechanisms by which acrocentric-acrocentric fusions are promoted by DNA damage and repair.

Authors
Stimpson, KM; Sullivan, LL; Kuo, ME; Sullivan, BA
MLA Citation
Stimpson, KM, Sullivan, LL, Kuo, ME, and Sullivan, BA. "Nucleolar organization, ribosomal DNA array stability, and acrocentric chromosome integrity are linked to telomere function." PloS one 9.3 (January 2014): e92432-.
Website
http://hdl.handle.net/10161/9507
PMID
24662969
Source
epmc
Published In
PloS one
Volume
9
Issue
3
Publish Date
2014
Start Page
e92432
DOI
10.1371/journal.pone.0092432

Using Chromosome Engineering to Study Centromere Identity and Chromosome Function

Authors
Sullivan, BA
MLA Citation
Sullivan, BA. "Using Chromosome Engineering to Study Centromere Identity and Chromosome Function." 2014.
Source
wos-lite
Published In
Cytogenetic and genome research
Volume
142
Issue
3
Publish Date
2014

Esperanto for histones: CENP-A, not CenH3, is the centromeric histone H3 variant

Authors
Earnshaw, WC; Allshire, RC; Black, BE; Bloom, K; Brinkley, BR; Brown, W; Cheeseman, IM; Choo, KHA; Copenhaver, GP; DeLuca, JG; Desai, A; Diekmann, S; Erhardt, S; Fitzgerald-Hayes, M; Foltz, D; Fukagawa, T; Gassmann, R; Gerlich, DW; Glover, DM; Gorbsky, GJ; Harrison, SC; Heun, P; Hirota, T; Jansen, LET; Karpen, G; Kops, GJPL; Lampson, MA; Lens, SM; Losada, A; Luger, K; Maiato, H; Maddox, PS; Margolis, RL; Masumoto, H; McAinsh, AD; Mellone, BG; Meraldi, P; Musacchio, A; Oegema, K; O'Neill, RJ et al.
MLA Citation
Earnshaw, WC, Allshire, RC, Black, BE, Bloom, K, Brinkley, BR, Brown, W, Cheeseman, IM, Choo, KHA, Copenhaver, GP, DeLuca, JG, Desai, A, Diekmann, S, Erhardt, S, Fitzgerald-Hayes, M, Foltz, D, Fukagawa, T, Gassmann, R, Gerlich, DW, Glover, DM, Gorbsky, GJ, Harrison, SC, Heun, P, Hirota, T, Jansen, LET, Karpen, G, Kops, GJPL, Lampson, MA, Lens, SM, Losada, A, Luger, K, Maiato, H, Maddox, PS, Margolis, RL, Masumoto, H, McAinsh, AD, Mellone, BG, Meraldi, P, Musacchio, A, Oegema, K, and O'Neill, RJ et al. "Esperanto for histones: CENP-A, not CenH3, is the centromeric histone H3 variant." CHROMOSOME RESEARCH 21.2 (April 2013): 101-106.
PMID
23580138
Source
wos-lite
Published In
Chromosome Research
Volume
21
Issue
2
Publish Date
2013
Start Page
101
End Page
106
DOI
10.1007/s10577-013-9347-y

Functional epialleles at an endogenous human centromere.

Human centromeres are defined by megabases of homogenous alpha-satellite DNA arrays that are packaged into specialized chromatin marked by the centromeric histone variant, centromeric protein A (CENP-A). Although most human chromosomes have a single higher-order repeat (HOR) array of alpha satellites, several chromosomes have more than one HOR array. Homo sapiens chromosome 17 (HSA17) has two juxtaposed HOR arrays, D17Z1 and D17Z1-B. Only D17Z1 has been linked to CENP-A chromatin assembly. Here, we use human artificial chromosome assembly assays to show that both D17Z1 and D17Z1-B can support de novo centromere assembly independently. We extend these in vitro studies and demonstrate, using immunostaining and chromatin analyses, that in human cells the centromere can be assembled at D17Z1 or D17Z1-B. Intriguingly, some humans are functional heterozygotes, meaning that CENP-A is located at a different HOR array on the two HSA17 homologs. The site of CENP-A assembly on HSA17 is stable and is transmitted through meiosis, as evidenced by inheritance of CENP-A location through multigenerational families. Differences in histone modifications are not linked clearly with active and inactive D17Z1 and D17Z1-B arrays; however, we detect a correlation between the presence of variant repeat units of D17Z1 and CENP-A assembly at the opposite array, D17Z1-B. Our studies reveal the presence of centromeric epialleles on an endogenous human chromosome and suggest genomic complexities underlying the mechanisms that determine centromere identity in humans.

Authors
Maloney, KA; Sullivan, LL; Matheny, JE; Strome, ED; Merrett, SL; Ferris, A; Sullivan, BA
MLA Citation
Maloney, KA, Sullivan, LL, Matheny, JE, Strome, ED, Merrett, SL, Ferris, A, and Sullivan, BA. "Functional epialleles at an endogenous human centromere." Proc Natl Acad Sci U S A 109.34 (August 21, 2012): 13704-13709.
Website
http://hdl.handle.net/10161/12802
PMID
22847449
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
109
Issue
34
Publish Date
2012
Start Page
13704
End Page
13709
DOI
10.1073/pnas.1203126109

Dicentric chromosomes: unique models to study centromere function and inactivation.

Dicentric chromosomes are products of genome rearrangement that place two centromeres on the same chromosome. Depending on the organism, dicentric stability varies after formation. In humans, dicentrics occur naturally in a substantial portion of the population and usually segregate successfully in mitosis and meiosis. Their stability has been attributed to inactivation of one of the two centromeres, creating a functionally monocentric chromosome that can segregate normally during cell division. The molecular basis for centromere inactivation is not well understood, although studies in model organisms and in humans suggest that genomic and epigenetic mechanisms can be involved. Furthermore, constitutional dicentric chromosomes ascertained in patients presumably represent the most stable chromosomes, so the spectrum of dicentric fates, if it exists, is not entirely clear. Studies of engineered or induced dicentrics in budding yeast and plants have provided significant insight into the fate of dicentric chromosomes. And, more recently, studies have shown that dicentrics in humans can also undergo multiple fates after formation. Here, we discuss current experimental evidence from various organisms that has deepened our understanding of dicentric behavior and the intriguingly complex process of centromere inactivation.

Authors
Stimpson, KM; Matheny, JE; Sullivan, BA
MLA Citation
Stimpson, KM, Matheny, JE, and Sullivan, BA. "Dicentric chromosomes: unique models to study centromere function and inactivation." Chromosome Res 20.5 (July 2012): 595-605. (Review)
PMID
22801777
Source
pubmed
Published In
Chromosome Research
Volume
20
Issue
5
Publish Date
2012
Start Page
595
End Page
605
DOI
10.1007/s10577-012-9302-3

Centromeres poised en pointe: CDKs put a hold on CENP-A assembly.

Eukaryotic centromeres are propagated by incorporation of the centromere-specific histone CENP-A into centromeric chromatin. Silva et al. (2012) now show that cyclin-dependent kinases (CDKs) hold the CENP-A assembly machinery in an inactive state until mitotic exit and entry into G1, at which time new CENP-A is loaded.

Authors
Stimpson, KM; Sullivan, BA
MLA Citation
Stimpson, KM, and Sullivan, BA. "Centromeres poised en pointe: CDKs put a hold on CENP-A assembly." Dev Cell 22.1 (January 17, 2012): 1-2.
PMID
22264723
Source
pubmed
Published In
Developmental Cell
Volume
22
Issue
1
Publish Date
2012
Start Page
1
End Page
2
DOI
10.1016/j.devcel.2011.12.013

Foreword: The centromere and kinetochore in creatures great and small

Authors
O'Neill, RJ; Sullivan, BA
MLA Citation
O'Neill, RJ, and Sullivan, BA. "Foreword: The centromere and kinetochore in creatures great and small." Chromosome Research 20.5 (2012): 461-463.
PMID
22801778
Source
scival
Published In
Chromosome Research
Volume
20
Issue
5
Publish Date
2012
Start Page
461
End Page
463
DOI
10.1007/s10577-012-9303-2

Genomic size of CENP-A domain is proportional to total alpha satellite array size at human centromeres and expands in cancer cells.

Human centromeres contain multi-megabase-sized arrays of alpha satellite DNA, a family of satellite DNA repeats based on a tandemly arranged 171 bp monomer. The centromere-specific histone protein CENP-A is assembled on alpha satellite DNA within the primary constriction, but does not extend along its entire length. CENP-A domains have been estimated to extend over 2,500 kb of alpha satellite DNA. However, these estimates do not take into account inter-individual variation in alpha satellite array sizes on homologous chromosomes and among different chromosomes. We defined the genomic distance of CENP-A chromatin on human chromosomes X and Y from different individuals. CENP-A chromatin occupied different genomic intervals on different chromosomes, but despite inter-chromosomal and inter-individual array size variation, the ratio of CENP-A to total alpha satellite DNA size remained consistent. Changes in the ratio of alpha satellite array size to CENP-A domain size were observed when CENP-A was overexpressed and when primary cells were transformed by disrupting interactions between the tumor suppressor protein Rb and chromatin. Our data support a model for centromeric domain organization in which the genomic limits of CENP-A chromatin varies on different human chromosomes, and imply that alpha satellite array size may be a more prominent predictor of CENP-A incorporation than chromosome size. In addition, our results also suggest that cancer transformation and amounts of centromeric heterochromatin have notable effects on the amount of alpha satellite that is associated with CENP-A chromatin.

Authors
Sullivan, LL; Boivin, CD; Mravinac, B; Song, IY; Sullivan, BA
MLA Citation
Sullivan, LL, Boivin, CD, Mravinac, B, Song, IY, and Sullivan, BA. "Genomic size of CENP-A domain is proportional to total alpha satellite array size at human centromeres and expands in cancer cells." Chromosome Res 19.4 (May 2011): 457-470.
Website
http://hdl.handle.net/10161/12806
PMID
21484447
Source
pubmed
Published In
Chromosome Research
Volume
19
Issue
4
Publish Date
2011
Start Page
457
End Page
470
DOI
10.1007/s10577-011-9208-5

Histone H3K4 methylation keeps centromeres open for business.

Authors
Stimpson, KM; Sullivan, BA
MLA Citation
Stimpson, KM, and Sullivan, BA. "Histone H3K4 methylation keeps centromeres open for business." EMBO J 30.2 (January 19, 2011): 233-234.
PMID
21245889
Source
pubmed
Published In
EMBO Journal
Volume
30
Issue
2
Publish Date
2011
Start Page
233
End Page
234
DOI
10.1038/emboj.2010.339

Epigenomics of centromere assembly and function.

The centromere is a complex chromosomal locus where the kinetochore is formed and microtubules attach during cell division. Centromere identity involves both genomic and sequence-independent (epigenetic) mechanisms. Current models for how centromeres are formed and, conversely, turned off have emerged from studies of unusual or engineered chromosomes, such as neocentromeres, artificial chromosomes, and dicentric chromosomes. Recent studies have highlighted the importance of unique chromatin marked by the histone H3 variant CENP-A, classical chromatin (heterochromatin and euchromatin), and transcription during centromere activation and inactivation. These advances have deepened our view of what defines a centromere and how it behaves in various genomic and chromatin contexts.

Authors
Stimpson, KM; Sullivan, BA
MLA Citation
Stimpson, KM, and Sullivan, BA. "Epigenomics of centromere assembly and function." Curr Opin Cell Biol 22.6 (December 2010): 772-780. (Review)
PMID
20675111
Source
pubmed
Published In
Current Opinion in Cell Biology
Volume
22
Issue
6
Publish Date
2010
Start Page
772
End Page
780
DOI
10.1016/j.ceb.2010.07.002

Telomere disruption results in non-random formation of de novo dicentric chromosomes involving acrocentric human chromosomes.

Genome rearrangement often produces chromosomes with two centromeres (dicentrics) that are inherently unstable because of bridge formation and breakage during cell division. However, mammalian dicentrics, and particularly those in humans, can be quite stable, usually because one centromere is functionally silenced. Molecular mechanisms of centromere inactivation are poorly understood since there are few systems to experimentally create dicentric human chromosomes. Here, we describe a human cell culture model that enriches for de novo dicentrics. We demonstrate that transient disruption of human telomere structure non-randomly produces dicentric fusions involving acrocentric chromosomes. The induced dicentrics vary in structure near fusion breakpoints and like naturally-occurring dicentrics, exhibit various inter-centromeric distances. Many functional dicentrics persist for months after formation. Even those with distantly spaced centromeres remain functionally dicentric for 20 cell generations. Other dicentrics within the population reflect centromere inactivation. In some cases, centromere inactivation occurs by an apparently epigenetic mechanism. In other dicentrics, the size of the alpha-satellite DNA array associated with CENP-A is reduced compared to the same array before dicentric formation. Extra-chromosomal fragments that contained CENP-A often appear in the same cells as dicentrics. Some of these fragments are derived from the same alpha-satellite DNA array as inactivated centromeres. Our results indicate that dicentric human chromosomes undergo alternative fates after formation. Many retain two active centromeres and are stable through multiple cell divisions. Others undergo centromere inactivation. This event occurs within a broad temporal window and can involve deletion of chromatin that marks the locus as a site for CENP-A maintenance/replenishment.

Authors
Stimpson, KM; Song, IY; Jauch, A; Holtgreve-Grez, H; Hayden, KE; Bridger, JM; Sullivan, BA
MLA Citation
Stimpson, KM, Song, IY, Jauch, A, Holtgreve-Grez, H, Hayden, KE, Bridger, JM, and Sullivan, BA. "Telomere disruption results in non-random formation of de novo dicentric chromosomes involving acrocentric human chromosomes. (Published online)" PLoS Genet 6.8 (August 12, 2010).
Website
http://hdl.handle.net/10161/4476
PMID
20711355
Source
pubmed
Published In
PLoS genetics
Volume
6
Issue
8
Publish Date
2010
DOI
10.1371/journal.pgen.1001061

Optical mapping of protein-DNA complexes on chromatin fibers.

Immunofluorescence (IF) and Fluorescence in situ Hybridization (FISH) are conventional methods used to study the structure and organization of metaphase chromosomes and interphase nuclei. Using these techniques, the locations of whole chromosome territories, chromatin subdomains, and specific DNA sequences can be evaluated at kilobase or megabase resolution. Even higher resolution of the spatial relationships of proteins and DNA can be achieved using combined IF-FISH on extended chromatin fibers. This method of optical mapping is a powerful system for localizing molecular probes along released chromatin fibers and visualizing small (<20 kb) or large (20-5,000 kb) chromosomal domains. Chromatin fiber analysis can fill the gaps in resolution between classical chromosome studies and molecular analyses, such as chromatin immunoprecipitation (ChIP) that evaluates chromatin organization at the level of single or multiple nucleosomes. In this chapter, the conceptual and technical aspects of chromatin fiber IF-FISH are presented, along with examples of successful applications.

Authors
Sullivan, BA
MLA Citation
Sullivan, BA. "Optical mapping of protein-DNA complexes on chromatin fibers." Methods Mol Biol 659 (2010): 99-115.
PMID
20809306
Source
pubmed
Published In
Methods in molecular biology (Clifton, N.J.)
Volume
659
Publish Date
2010
Start Page
99
End Page
115
DOI
10.1007/978-1-60761-789-1_7

The centromere

Centromeres are chromosomal loci that assemble the proteinaceous kinetochore, maintain sister chromatid cohesion, regulate chromosome attachment to the spindle, and direct chromosome movement during cell division. Although the function of centromeres and proteins that contribute to their complex structure are conserved in eukaryotes, centromeric DNAs are strikingly divergent. In this chapter, I review centromere organization in a range of organisms, including unicellular eukaryotes, fruit flies, plants, and mammals. Sequence features and epigenetic mechanisms of centromere identity and regulation, including DNA-protein interactions, post-translational modifications, RNA, and protein dosage that influence centromere-specific chromatin architecture are discussed. Understanding the assembly and organization of centromeres and the contributions of sequence and epigenetic features in centromere identity and diversity remain important areas of study in chromosome biology. © 2009 Springer Science+Business Media, LLC.

Authors
Sullivan, BA
MLA Citation
Sullivan, BA. "The centromere." (December 1, 2009): 45-76. (Chapter)
Source
scopus
Publish Date
2009
Start Page
45
End Page
76
DOI
10.1007/978-0-387-69076-6_3

MYC activity mitigates response to rapamycin in prostate cancer through eukaryotic initiation factor 4E-binding protein 1-mediated inhibition of autophagy.

Loss of PTEN and activation of phosphoinositide 3-kinase are commonly observed in advanced prostate cancer. Inhibition of mammalian target of rapamycin (mTOR), a downstream target of phosphoinositide 3-kinase signaling, results in cell cycle arrest and apoptosis in multiple in vitro and in vivo models of prostate cancer. However, single-agent use of mTOR inhibition has limited clinical success, and the identification of molecular events mitigating tumor response to mTOR inhibition remains a critical question. Here, using genetically engineered human prostate epithelial cells (PrEC), we show that MYC, a frequent target of genetic gain in prostate cancers, abrogates sensitivity to rapamycin by decreasing rapamycin-induced cytostasis and autophagy. Analysis of MYC and the mTOR pathway in human prostate tumors and PrEC showed selective increased expression of eukaryotic initiation factor 4E-binding protein 1 (4EBP1) with gain in MYC copy number or forced MYC expression, respectively. We have also found that MYC binds to regulatory regions of the 4EBP1 gene. Suppression of 4EBP1 expression resulted in resensitization of MYC-expressing PrEC to rapamycin and increased autophagy. Taken together, our findings suggest that MYC expression abrogates sensitivity to rapamycin through increased expression of 4EBP1 and reduced autophagy.

Authors
Balakumaran, BS; Porrello, A; Hsu, DS; Glover, W; Foye, A; Leung, JY; Sullivan, BA; Hahn, WC; Loda, M; Febbo, PG
MLA Citation
Balakumaran, BS, Porrello, A, Hsu, DS, Glover, W, Foye, A, Leung, JY, Sullivan, BA, Hahn, WC, Loda, M, and Febbo, PG. "MYC activity mitigates response to rapamycin in prostate cancer through eukaryotic initiation factor 4E-binding protein 1-mediated inhibition of autophagy." Cancer Res 69.19 (October 1, 2009): 7803-7810.
Website
http://hdl.handle.net/10161/4170
PMID
19773438
Source
pubmed
Published In
Cancer Research
Volume
69
Issue
19
Publish Date
2009
Start Page
7803
End Page
7810
DOI
10.1158/0008-5472.CAN-09-0910

DNMT3B interacts with constitutive centromere protein CENP-C to modulate DNA methylation and the histone code at centromeric regions.

DNA methylation is an epigenetically imposed mark of transcriptional repression that is essential for maintenance of chromatin structure and genomic stability. Genome-wide methylation patterns are mediated by the combined action of three DNA methyltransferases: DNMT1, DNMT3A and DNMT3B. Compelling links exist between DNMT3B and chromosome stability as emphasized by the mitotic defects that are a hallmark of ICF syndrome, a disease arising from germline mutations in DNMT3B. Centromeric and pericentromeric regions are essential for chromosome condensation and the fidelity of segregation. Centromere regions contain distinct epigenetic marks, including dense DNA hypermethylation, yet the mechanisms by which DNA methylation is targeted to these regions remains largely unknown. In the present study, we used a yeast two-hybrid screen and identified a novel interaction between DNMT3B and constitutive centromere protein CENP-C. CENP-C is itself essential for mitosis. We confirm this interaction in mammalian cells and map the domains responsible. Using siRNA knock downs, bisulfite genomic sequencing and ChIP, we demonstrate for the first time that CENP-C recruits DNA methylation and DNMT3B to both centromeric and pericentromeric satellite repeats and that CENP-C and DNMT3B regulate the histone code in these regions, including marks characteristic of centromeric chromatin. Finally, we demonstrate that loss of CENP-C or DNMT3B leads to elevated chromosome misalignment and segregation defects during mitosis and increased transcription of centromeric repeats. Taken together, our data reveal a novel mechanism by which DNA methylation is targeted to discrete regions of the genome and contributes to chromosomal stability.

Authors
Gopalakrishnan, S; Sullivan, BA; Trazzi, S; Della Valle, G; Robertson, KD
MLA Citation
Gopalakrishnan, S, Sullivan, BA, Trazzi, S, Della Valle, G, and Robertson, KD. "DNMT3B interacts with constitutive centromere protein CENP-C to modulate DNA methylation and the histone code at centromeric regions." Hum Mol Genet 18.17 (September 1, 2009): 3178-3193.
PMID
19482874
Source
pubmed
Published In
Human Molecular Genetics
Volume
18
Issue
17
Publish Date
2009
Start Page
3178
End Page
3193
DOI
10.1093/hmg/ddp256

Histone modifications within the human X centromere region.

Human centromeres are multi-megabase regions of highly ordered arrays of alpha satellite DNA that are separated from chromosome arms by unordered alpha satellite monomers and other repetitive elements. Complexities in assembling such large repetitive regions have limited detailed studies of centromeric chromatin organization. However, a genomic map of the human X centromere has provided new opportunities to explore genomic architecture of a complex locus. We used ChIP to examine the distribution of modified histones within centromere regions of multiple X chromosomes. Methylation of H3 at lysine 4 coincided with DXZ1 higher order alpha satellite, the site of CENP-A localization. Heterochromatic histone modifications were distributed across the 400-500 kb pericentromeric regions. The large arrays of alpha satellite and gamma satellite DNA were enriched for both euchromatic and heterochromatic modifications, implying that some pericentromeric repeats have multiple chromatin characteristics. Partial truncation of the X centromere resulted in reduction in the size of the CENP-A/Cenp-A domain and increased heterochromatic modifications in the flanking pericentromere. Although the deletion removed approximately 1/3 of centromeric DNA, the ratio of CENP-A to alpha satellite array size was maintained in the same proportion, suggesting that a limited, but defined linear region of the centromeric DNA is necessary for kinetochore assembly. Our results indicate that the human X centromere contains multiple types of chromatin, is organized similarly to smaller eukaryotic centromeres, and responds to structural changes by expanding or contracting domains.

Authors
Mravinac, B; Sullivan, LL; Reeves, JW; Yan, CM; Kopf, KS; Farr, CJ; Schueler, MG; Sullivan, BA
MLA Citation
Mravinac, B, Sullivan, LL, Reeves, JW, Yan, CM, Kopf, KS, Farr, CJ, Schueler, MG, and Sullivan, BA. "Histone modifications within the human X centromere region. (Published online)" PLoS One 4.8 (August 12, 2009): e6602-.
Website
http://hdl.handle.net/10161/4514
PMID
19672304
Source
pubmed
Published In
PloS one
Volume
4
Issue
8
Publish Date
2009
Start Page
e6602
DOI
10.1371/journal.pone.0006602

Non-random chromosome fusions occur after transient telomere destabilization

Authors
Stimpson, KM; Jauch, A; Sullivan, BA
MLA Citation
Stimpson, KM, Jauch, A, and Sullivan, BA. "Non-random chromosome fusions occur after transient telomere destabilization." CHROMOSOME RESEARCH 17.4 (May 2009): 557-557.
Source
wos-lite
Published In
Chromosome Research
Volume
17
Issue
4
Publish Date
2009
Start Page
557
End Page
557

hBub1 negatively regulates p53 mediated early cell death upon mitotic checkpoint activation.

Our previous studies showed that the depletion of the outer kinetochore protein hBub1 upon activation of spindle assembly checkpoint (SAC) primarily triggers early cell death mediated by p53 rather than aneuploidy. Here, we report that phosphorylation of p53 at Ser37 is critical for proapoptotic activity upon SAC activation. Furthermore, we show that p53 physically interacts with hBub1 at kinetochores in response to mitotic spindle damage suggesting a direct role for hBub1 in the suppression of p53 mediated cell death. This observation is further substantiated by the inhibition of p53 mediated transactivation of the proapoptotic target genes, PUMA and BAX, by hBub1 in SAC activated cells. In summary, our data from these and our previous studies strongly suggest that in response to SAC activation, hBub1 acts as a negative regulator of p53 mediated early cell death in a novel checkpoint pathway. On the translational medicine front, it is tempting to speculate that by disabling hBub1 in p53 proficient cancer cells, apoptosis may be induced as a therapeutic approach to eradicate the tumor cells.

Authors
Gao, F; Ponte, JF; Levy, M; Papageorgis, P; Cook, NM; Ozturk, S; Lambert, AW; Thiagalingam, A; Abdolmaleky, HM; Sullivan, BA; Thiagalingam, S
MLA Citation
Gao, F, Ponte, JF, Levy, M, Papageorgis, P, Cook, NM, Ozturk, S, Lambert, AW, Thiagalingam, A, Abdolmaleky, HM, Sullivan, BA, and Thiagalingam, S. "hBub1 negatively regulates p53 mediated early cell death upon mitotic checkpoint activation." Cancer Biol Ther 8.7 (April 2009): 548-556.
PMID
19252416
Source
pubmed
Published In
Cancer Biology and Therapy
Volume
8
Issue
7
Publish Date
2009
Start Page
548
End Page
556

Human gamma-satellite DNA maintains open chromatin structure and protects a transgene from epigenetic silencing.

The role of repetitive DNA sequences in pericentromeric regions with respect to kinetochore/heterochromatin structure and function is poorly understood. Here, we use a mouse erythroleukemia cell (MEL) system for studying how repetitive DNA assumes or is assembled into different chromatin structures. We show that human gamma-satellite DNA arrays allow a transcriptionally permissive chromatin conformation in an adjacent transgene and efficiently protect it from epigenetic silencing. These arrays contain CTCF and Ikaros binding sites. In MEL cells, this gamma-satellite DNA activity depends on binding of Ikaros proteins involved in differentiation along the hematopoietic pathway. Given our discovery of gamma-satellite DNA in pericentromeric regions of most human chromosomes and a dynamic chromatin state of gamma-satellite arrays in their natural location, we suggest that gamma-satellite DNA represents a unique region of the functional centromere with a possible role in preventing heterochromatin spreading beyond the pericentromeric region.

Authors
Kim, J-H; Ebersole, T; Kouprina, N; Noskov, VN; Ohzeki, J-I; Masumoto, H; Mravinac, B; Sullivan, BA; Pavlicek, A; Dovat, S; Pack, SD; Kwon, Y-W; Flanagan, PT; Loukinov, D; Lobanenkov, V; Larionov, V
MLA Citation
Kim, J-H, Ebersole, T, Kouprina, N, Noskov, VN, Ohzeki, J-I, Masumoto, H, Mravinac, B, Sullivan, BA, Pavlicek, A, Dovat, S, Pack, SD, Kwon, Y-W, Flanagan, PT, Loukinov, D, Lobanenkov, V, and Larionov, V. "Human gamma-satellite DNA maintains open chromatin structure and protects a transgene from epigenetic silencing." Genome Res 19.4 (April 2009): 533-544.
PMID
19141594
Source
pubmed
Published In
Genome research
Volume
19
Issue
4
Publish Date
2009
Start Page
533
End Page
544
DOI
10.1101/gr.086496.108

Regulation of mitotic chromosome cohesion by Haspin and Aurora B.

In vertebrate mitosis, cohesion between sister chromatids is lost in two stages. In prophase and prometaphase, cohesin release from chromosome arms occurs under the control of Polo-like kinase 1 and Aurora B, while Shugoshin is thought to prevent removal of centromeric cohesin until anaphase. The regulatory enzymes that act to sustain centromeric cohesion are incompletely described, however. Haspin/Gsg2 is a histone H3 threonine-3 kinase required for normal mitosis. We report here that both H3 threonine-3 phosphorylation and cohesin are located at inner centromeres. Haspin depletion disrupts cohesin binding and sister chromatid association in mitosis, preventing normal chromosome alignment and activating the spindle assembly checkpoint, leading to arrest in a prometaphase-like state. Overexpression of Haspin hinders cohesin release and stabilizes arm cohesion. We conclude that Haspin is required to maintain centromeric cohesion during mitosis. We also suggest that Aurora B regulates cohesin removal through its effect on the localization of Shugoshin.

Authors
Dai, J; Sullivan, BA; Higgins, JMG
MLA Citation
Dai, J, Sullivan, BA, and Higgins, JMG. "Regulation of mitotic chromosome cohesion by Haspin and Aurora B." Dev Cell 11.5 (November 2006): 741-750.
PMID
17084365
Source
pubmed
Published In
Developmental Cell
Volume
11
Issue
5
Publish Date
2006
Start Page
741
End Page
750
DOI
10.1016/j.devcel.2006.09.018

Human centromeric chromatin is a dynamic chromosomal domain that can spread over noncentromeric DNA.

Human centromeres are specialized chromatin domains containing the centromeric histone H3 variant CENP-A. CENP-A nucleosomes are interspersed with nucleosomes containing histone H3 dimethylated at lysine 4, distinguishing centromeric chromatin (CEN chromatin) from flanking heterochromatin that is defined by H3 lysine 9 methylation. To understand the relationship between chromatin organization and the genomic structure of human centromeres, we compared molecular profiles of three endogenous human centromeres, defined by uninterrupted higher-order alpha-satellite DNA, with human artificial chromosomes that contain discontinuous blocks of higher-order alpha-satellite DNA and noncentromeric DNA. The underlying sequence did not correlate with chromatin states, because both higher-order alpha-satellite DNA and noncentromeric DNA were enriched for modifications that define CEN chromatin, euchromatin, and heterochromatin. Human artificial chromosomes were also organized into distinct domains. CENP-A and heterochromatin were assembled over noncentromeric DNA, including the gene blasticidin, into nonoverlapping domains. Blasticidin transcripts were enriched at sites of CENP-A binding but not at H3 methylated at lysine 9, indicating that formation of CEN chromatin within a repetitive DNA environment does not preclude gene expression. Finally, we tested the role of centric heterochromatin as a centromeric boundary by increasing CENP-A dosage to expand the CEN domain. In response, H3 lysine 9 dimethylation, but not trimethylation, was markedly decreased at all centromeres examined. We propose that human centromere regions normally exist in a dynamic state in which a regional boundary, defined by H3 lysine 9 dimethylation, separates CEN chromatin from constitutive heterochromatin.

Authors
Lam, AL; Boivin, CD; Bonney, CF; Rudd, MK; Sullivan, BA
MLA Citation
Lam, AL, Boivin, CD, Bonney, CF, Rudd, MK, and Sullivan, BA. "Human centromeric chromatin is a dynamic chromosomal domain that can spread over noncentromeric DNA." Proc Natl Acad Sci U S A 103.11 (March 14, 2006): 4186-4191.
PMID
16537506
Source
pubmed
Published In
Proceedings of the National Academy of Sciences of USA
Volume
103
Issue
11
Publish Date
2006
Start Page
4186
End Page
4191
DOI
10.1073/pnas.0507947103

Structural and functional dynamics of human centromeric chromatin.

Centromeres are the elements of chromosomes that assemble the proteinaceous kinetochore, maintain sister chromatid cohesion, regulate chromosome attachment to the spindle, and direct chromosome movement during cell division. Although the functions of centromeres and the proteins that contribute to their complex structure and function are conserved in eukaryotes, centromeric DNA diverges rapidly. Human centromeres are particularly complicated. Here, we review studies on the organization of homogeneous arrays of chromosome-specific alpha-satellite repeats and evolutionary links among eukaryotic centromeric sequences. We also discuss epigenetic mechanisms of centromere identity that confer structural and functional features of the centromere through DNA-protein interactions and post-translational modifications, producing centromere-specific chromatin signatures. The assembly and organization of human centromeres, the contributions of satellite DNA to centromere identity and diversity, and the mechanism whereby centromeres are distinguished from the rest of the genome reflect ongoing puzzles in chromosome biology.

Authors
Schueler, MG; Sullivan, BA
MLA Citation
Schueler, MG, and Sullivan, BA. "Structural and functional dynamics of human centromeric chromatin." Annu Rev Genomics Hum Genet 7 (2006): 301-313. (Review)
PMID
16756479
Source
pubmed
Published In
Annual Review of Genomics and Human Genetics
Volume
7
Publish Date
2006
Start Page
301
End Page
313
DOI
10.1146/annurev.genom.7.080505.115613

Erratum: Human centromeric chromatin is a dynamic chromosomal domain that can spread over noncentromeric DNA (Proceedings of the National Academy of Sciences of the United States of America (March 14, 2006) 103, 11 (4186-4191): 10.1073/pnas.0507947103)

Authors
Lam, AL; Boivin, CD; Bonney, CF; Rudd, MK; Sullivan, BA
MLA Citation
Lam, AL, Boivin, CD, Bonney, CF, Rudd, MK, and Sullivan, BA. "Erratum: Human centromeric chromatin is a dynamic chromosomal domain that can spread over noncentromeric DNA (Proceedings of the National Academy of Sciences of the United States of America (March 14, 2006) 103, 11 (4186-4191): 10.1073/pnas.0507947103)." Proceedings of the National Academy of Sciences of the United States of America 103.16 (2006): 6410--.
Source
scival
Published In
Proceedings of the National Academy of Sciences of USA
Volume
103
Issue
16
Publish Date
2006
Start Page
6410-
DOI
10.1073/pnas.0602078103

Regulation of nuclear Prointerleukin-16 and p27(Kip1) in primary human T lymphocytes.

Prointerleukin-16 (Pro-IL-16) is an abundant, PDZ domain-containing protein expressed in the nucleus and cytoplasm of resting human T lymphocytes. We have previously shown that ectopic expression of Pro-IL-16 in Pro-IL-16-negative human Jurkat cells represses transcription of the F-box protein, Skp2, resulting in accumulation of the cyclin-dependent kinase inhibitor, p27(Kip1), and G0/G1 cell cycle arrest. The current studies demonstrate the kinetics of Pro-IL-16 and p27(Kip1) expression in activated normal human T lymphocytes. We correlate nuclear Pro-IL-16 loss with decreased p27(Kip1) expression, increased cell cycle progression, and proliferation. Conversely, we show that constitutive expression of Pro-IL-16 by retroviral infection of activated human T lymphocytes induces G0/G1 cell cycle arrest, inhibits proliferation, and is associated with increased levels of p27(Kip1). These findings implicate nuclear Pro-IL-16 as a cell cycle regulatory protein for human T lymphocytes.

Authors
Wilson, KC; Cattel, DJ; Wan, Z; Rahangdale, S; Ren, F; Kornfeld, H; Sullivan, BA; Cruikshank, WW; Center, DM
MLA Citation
Wilson, KC, Cattel, DJ, Wan, Z, Rahangdale, S, Ren, F, Kornfeld, H, Sullivan, BA, Cruikshank, WW, and Center, DM. "Regulation of nuclear Prointerleukin-16 and p27(Kip1) in primary human T lymphocytes." Cell Immunol 237.1 (September 2005): 17-27.
PMID
16289056
Source
pubmed
Published In
Cellular Immunology
Volume
237
Issue
1
Publish Date
2005
Start Page
17
End Page
27
DOI
10.1016/j.cellimm.2005.09.003

Control of gene expression and assembly of chromosomal subdomains by chromatin regulators with antagonistic functions.

Epigenetic regulation of higher-order chromatin structure controls gene expression and the assembly of chromosomal domains during cell division, differentiation, and development. The proposed "histone code" integrates a complex system of histone modifications and chromosomal proteins that establish and maintain distinctive types of chromatin, such as euchromatin, heterochromatin, and centromeric (CEN) chromatin. The reversible nature of histone acetylation, phosphorylation, and (most recently discovered) methylation are mechanisms for controlling gene expression and partitioning the genome into functional domains. Many different regions of the genome contain similar epigenetic marks (histone modifications), raising the question as to how they are independently specified and regulated. In this review, we will focus on several recent discoveries in chromatin and chromosome biology: (1) identification of long-elusive histone "de-methylating" enzymes that affect chromatin structure, and (2) assembly and maintenance of chromatin domains, specifically heterochromatin and euchromatin, through a dynamic equilibrium of modifying enzymes, histone modifications, and histone variants identified biochemically and genetically.

Authors
Lam, AL; Pazin, DE; Sullivan, BA
MLA Citation
Lam, AL, Pazin, DE, and Sullivan, BA. "Control of gene expression and assembly of chromosomal subdomains by chromatin regulators with antagonistic functions." Chromosoma 114.4 (September 2005): 242-251. (Review)
PMID
16012860
Source
pubmed
Published In
Chromosoma
Volume
114
Issue
4
Publish Date
2005
Start Page
242
End Page
251
DOI
10.1007/s00412-005-0001-0

Centromeric chromatin exhibits a histone modification pattern that is distinct from both euchromatin and heterochromatin.

Post-translational histone modifications regulate epigenetic switching between different chromatin states. Distinct histone modifications, such as acetylation, methylation and phosphorylation, define different functional chromatin domains, and often do so in a combinatorial fashion. The centromere is a unique chromosomal locus that mediates multiple segregation functions, including kinetochore formation, spindle-mediated movements, sister cohesion and a mitotic checkpoint. Centromeric (CEN) chromatin is embedded in heterochromatin and contains blocks of histone H3 nucleosomes interspersed with blocks of CENP-A nucleosomes, the histone H3 variant that provides a structural and functional foundation for the kinetochore. Here, we demonstrate that the spectrum of histone modifications present in human and Drosophila melanogaster CEN chromatin is distinct from that of both euchromatin and flanking heterochromatin. We speculate that this distinct modification pattern contributes to the unique domain organization and three-dimensional structure of centromeric regions, and/or to the epigenetic information that determines centromere identity.

Authors
Sullivan, BA; Karpen, GH
MLA Citation
Sullivan, BA, and Karpen, GH. "Centromeric chromatin exhibits a histone modification pattern that is distinct from both euchromatin and heterochromatin." Nat Struct Mol Biol 11.11 (November 2004): 1076-1083.
PMID
15475964
Source
pubmed
Published In
Nature Structural & Molecular Biology
Volume
11
Issue
11
Publish Date
2004
Start Page
1076
End Page
1083
DOI
10.1038/nsmb845

Centromere round-up at the heterochromatin corral.

Authors
Sullivan, BA
MLA Citation
Sullivan, BA. "Centromere round-up at the heterochromatin corral." Trends Biotechnol 20.3 (March 2002): 89-92.
PMID
11841851
Source
pubmed
Published In
Trends in Biotechnology
Volume
20
Issue
3
Publish Date
2002
Start Page
89
End Page
92

Conserved organization of centromeric chromatin in flies and humans.

Recent studies have highlighted the importance of centromere-specific histone H3-like (CENP-A) proteins in centromere function. We show that Drosophila CID and human CENP-A appear at metaphase as a three-dimensional structure that lacks histone H3. However, blocks of CID/CENP-A and H3 nucleosomes are linearly interspersed on extended chromatin fibers, and CID is close to H3 nucleosomes in polynucleosomal preparations. When CID is depleted by RNAi, it is replaced by H3, demonstrating flexibility of centromeric chromatin organization. Finally, contrary to models proposing that H3 and CID/CENP-A nucleosomes are replicated at different times in S phase, we show that interspersed H3 and CID/CENP-A chromatin are replicated concurrently during S phase in humans and flies. We propose that the unique structural arrangement of CID/CENP-A and H3 nucleosomes presents centromeric chromatin to the poleward face of the condensing mitotic chromosome.

Authors
Blower, MD; Sullivan, BA; Karpen, GH
MLA Citation
Blower, MD, Sullivan, BA, and Karpen, GH. "Conserved organization of centromeric chromatin in flies and humans." Dev Cell 2.3 (March 2002): 319-330.
PMID
11879637
Source
pubmed
Published In
Developmental Cell
Volume
2
Issue
3
Publish Date
2002
Start Page
319
End Page
330

Heterochromatic sequences in a Drosophila whole-genome shotgun assembly.

BACKGROUND: Most eukaryotic genomes include a substantial repeat-rich fraction termed heterochromatin, which is concentrated in centric and telomeric regions. The repetitive nature of heterochromatic sequence makes it difficult to assemble and analyze. To better understand the heterochromatic component of the Drosophila melanogaster genome, we characterized and annotated portions of a whole-genome shotgun sequence assembly. RESULTS: WGS3, an improved whole-genome shotgun assembly, includes 20.7 Mb of draft-quality sequence not represented in the Release 3 sequence spanning the euchromatin. We annotated this sequence using the methods employed in the re-annotation of the Release 3 euchromatic sequence. This analysis predicted 297 protein-coding genes and six non-protein-coding genes, including known heterochromatic genes, and regions of similarity to known transposable elements. Bacterial artificial chromosome (BAC)-based fluorescence in situ hybridization analysis was used to correlate the genomic sequence with the cytogenetic map in order to refine the genomic definition of the centric heterochromatin; on the basis of our cytological definition, the annotated Release 3 euchromatic sequence extends into the centric heterochromatin on each chromosome arm. CONCLUSIONS: Whole-genome shotgun assembly produced a reliable draft-quality sequence of a significant part of the Drosophila heterochromatin. Annotation of this sequence defined the intron-exon structures of 30 known protein-coding genes and 267 protein-coding gene models. The cytogenetic mapping suggests that an additional 150 predicted genes are located in heterochromatin at the base of the Release 3 euchromatic sequence. Our analysis suggests strategies for improving the sequence and annotation of the heterochromatic portions of the Drosophila and other complex genomes.

Authors
Hoskins, RA; Smith, CD; Carlson, JW; Carvalho, AB; Halpern, A; Kaminker, JS; Kennedy, C; Mungall, CJ; Sullivan, BA; Sutton, GG; Yasuhara, JC; Wakimoto, BT; Myers, EW; Celniker, SE; Rubin, GM; Karpen, GH
MLA Citation
Hoskins, RA, Smith, CD, Carlson, JW, Carvalho, AB, Halpern, A, Kaminker, JS, Kennedy, C, Mungall, CJ, Sullivan, BA, Sutton, GG, Yasuhara, JC, Wakimoto, BT, Myers, EW, Celniker, SE, Rubin, GM, and Karpen, GH. "Heterochromatic sequences in a Drosophila whole-genome shotgun assembly." Genome Biol 3.12 (2002): RESEARCH0085-.
PMID
12537574
Source
pubmed
Published In
Genome Biology
Volume
3
Issue
12
Publish Date
2002
Start Page
RESEARCH0085

LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development.

In humans, low peak bone mass is a significant risk factor for osteoporosis. We report that LRP5, encoding the low-density lipoprotein receptor-related protein 5, affects bone mass accrual during growth. Mutations in LRP5 cause the autosomal recessive disorder osteoporosis-pseudoglioma syndrome (OPPG). We find that OPPG carriers have reduced bone mass when compared to age- and gender-matched controls. We demonstrate LRP5 expression by osteoblasts in situ and show that LRP5 can transduce Wnt signaling in vitro via the canonical pathway. We further show that a mutant-secreted form of LRP5 can reduce bone thickness in mouse calvarial explant cultures. These data indicate that Wnt-mediated signaling via LRP5 affects bone accrual during growth and is important for the establishment of peak bone mass.

Authors
Gong, Y; Slee, RB; Fukai, N; Rawadi, G; Roman-Roman, S; Reginato, AM; Wang, H; Cundy, T; Glorieux, FH; Lev, D; Zacharin, M; Oexle, K; Marcelino, J; Suwairi, W; Heeger, S; Sabatakos, G; Apte, S; Adkins, WN; Allgrove, J; Arslan-Kirchner, M; Batch, JA; Beighton, P; Black, GC; Boles, RG; Boon, LM; Borrone, C; Brunner, HG; Carle, GF; Dallapiccola, B; De Paepe, A; Floege, B; Halfhide, ML; Hall, B; Hennekam, RC; Hirose, T; Jans, A; Jüppner, H; Kim, CA; Keppler-Noreuil, K; Kohlschuetter, A; LaCombe, D et al.
MLA Citation
Gong, Y, Slee, RB, Fukai, N, Rawadi, G, Roman-Roman, S, Reginato, AM, Wang, H, Cundy, T, Glorieux, FH, Lev, D, Zacharin, M, Oexle, K, Marcelino, J, Suwairi, W, Heeger, S, Sabatakos, G, Apte, S, Adkins, WN, Allgrove, J, Arslan-Kirchner, M, Batch, JA, Beighton, P, Black, GC, Boles, RG, Boon, LM, Borrone, C, Brunner, HG, Carle, GF, Dallapiccola, B, De Paepe, A, Floege, B, Halfhide, ML, Hall, B, Hennekam, RC, Hirose, T, Jans, A, Jüppner, H, Kim, CA, Keppler-Noreuil, K, Kohlschuetter, A, and LaCombe, D et al. "LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development." Cell 107.4 (November 16, 2001): 513-523.
PMID
11719191
Source
pubmed
Published In
Cell
Volume
107
Issue
4
Publish Date
2001
Start Page
513
End Page
523

Centromere identity in Drosophila is not determined in vivo by replication timing.

Centromeric chromatin is uniquely marked by the centromere-specific histone CENP-A. For assembly of CENP-A into nucleosomes to occur without competition from H3 deposition, it was proposed that centromeres are among the first or last sequences to be replicated. In this study, centromere replication in Drosophila was studied in cell lines and in larval tissues that contain minichromosomes that have structurally defined centromeres. Two different nucleotide incorporation methods were used to evaluate replication timing of chromatin containing CID, a Drosophila homologue of CENP-A. Centromeres in Drosophila cell lines were replicated throughout S phase but primarily in mid S phase. However, endogenous centromeres and X-derived minichromosome centromeres in vivo were replicated asynchronously in mid to late S phase. Minichromosomes with structurally intact centromeres were replicated in late S phase, and those in which centric and surrounding heterochromatin were partially or fully deleted were replicated earlier in mid S phase. We provide the first in vivo evidence that centromeric chromatin is replicated at different times in S phase. These studies indicate that incorporation of CID/CENP-A into newly duplicated centromeres is independent of replication timing and argue against determination of centromere identity by temporal sequestration of centromeric chromatin replication relative to bulk genomic chromatin.

Authors
Sullivan, B; Karpen, G
MLA Citation
Sullivan, B, and Karpen, G. "Centromere identity in Drosophila is not determined in vivo by replication timing." J Cell Biol 154.4 (August 20, 2001): 683-690.
PMID
11514585
Source
pubmed
Published In
The Journal of Cell Biology
Volume
154
Issue
4
Publish Date
2001
Start Page
683
End Page
690
DOI
10.1083/jcb.200103001

Determining centromere identity: cyclical stories and forking paths.

The centromere is the genetic locus required for chromosome segregation. It is the site of spindle attachment to the chromosomes and is crucial for the transfer of genetic information between cell and organismal generations. Although the centromere was first recognized more than 120 years ago, little is known about what determines its site(s) of activity, and how it contributes to kinetochore formation and spindle attachment. Recent work in this field has supported the hypothesis that most eukaryotic centromeres are determined epigenetically rather than by primary DNA sequence. Here, we review recent studies that have elucidated the organization and functions of centromeric chromatin, and evaluate present-day models for how centromere identity and propagation are determined.

Authors
Sullivan, BA; Blower, MD; Karpen, GH
MLA Citation
Sullivan, BA, Blower, MD, and Karpen, GH. "Determining centromere identity: cyclical stories and forking paths." Nat Rev Genet 2.8 (August 2001): 584-596. (Review)
PMID
11483983
Source
pubmed
Published In
Nature Reviews Genetics
Volume
2
Issue
8
Publish Date
2001
Start Page
584
End Page
596
DOI
10.1038/35084512

Unusual chromosome architecture and behaviour at an HSR.

Amplification of sequences within mammalian chromosomes is often accompanied by the formation of homogeneously staining regions (HSRs). The arrangement of DNA sequences within such amplicons has been investigated, but little is known about the chromosome structure or behaviour of these unusual regions. We have analysed the metaphase chromosome structure of the dihydrofolate reductase (DHFR) amplicon of CHOC400 cells. The chromatin in this region contains hyperacetylated nucleosomes yet, at the same time, appears to be densely packed like heterochromatin. The region does not bind heterochromatin proteins. We show that the dense packing of the region is restricted to DNA located close to the chromosome core/scaffold. In contrast, levels of the chromosome scaffold protein topoisomerase II at HSRs are the same as those found at other euchromatic locations. Metaphase chromosome condensation of the HSR is shown to be sensitive to topoisomerase II inhibitors, and sister chromatids often appear to remain attached within the HSRs at metaphase. We suggest that these features underlie anaphase bridging and the aberrant interphase structure of the HSR. The DHFR amplicon is widely used as a model system to study mammalian DNA replication. We conclude that the higher-order chromosome structure of this amplicon is unusual and suggest that caution needs to be exercised in extrapolating data from HSRs to normal chromosomal loci.

Authors
Sullivan, BA; Bickmore, WA
MLA Citation
Sullivan, BA, and Bickmore, WA. "Unusual chromosome architecture and behaviour at an HSR." Chromosoma 109.3 (June 2000): 181-189.
PMID
10929196
Source
pubmed
Published In
Chromosoma
Volume
109
Issue
3
Publish Date
2000
Start Page
181
End Page
189

Stable dicentric X chromosomes with two functional centromeres.

Authors
Sullivan, BA; Willard, HF
MLA Citation
Sullivan, BA, and Willard, HF. "Stable dicentric X chromosomes with two functional centromeres." Nat Genet 20.3 (November 1998): 227-228. (Letter)
PMID
9806536
Source
pubmed
Published In
Nature Genetics
Volume
20
Issue
3
Publish Date
1998
Start Page
227
End Page
228
DOI
10.1038/3024

Variegated aneuploidy in two siblings: Phenotype, genotype, CENP-E analysis, and literature review

Cytogenetic studies of 2 sisters with mild microcephaly, growth deficiency, and mild errors of morphogenesis demonstrated a unique combination of multiple trisomies, most often involving chromosomes 8 and 18 either together as sole trisomies or in combination with other chromosomes. Since neither sib has phenotypic anomalies associated with trisomy 8 or 18 mosaicism, the trisomies likely did not occur during embryogenesis, but later possibly due to a predisposition for mitotic instability. To determine if the observed chromosome instability may be related to centromere function, metaphase cells were characterized by immunofluorescence of the centromere protein, CENP-E. Hybridization of CENP-E antibodies, in combination with in situ hybridization of a chromosome 8 or 18 α-satellite probe, showed hybridization to chromosomes 8 and 18 in both normal and aneuploid cells from each patient. These data indicate that the chromosomes in each child contain functional and active centromeres. The clinical and cytogenetic findings in these 2 individuals are compared with 7 other previously reported individuals, each of whom have similar findings. Together, these studies support the notion that a recessive mitotic mutant may be responsible for the chromosomal mosaicism and for the resulting clinical phenotype.

Authors
Flejter, WL; Issa, B; Sullivan, BA; Carey, JC; Brothman, AR
MLA Citation
Flejter, WL, Issa, B, Sullivan, BA, Carey, JC, and Brothman, AR. "Variegated aneuploidy in two siblings: Phenotype, genotype, CENP-E analysis, and literature review." American Journal of Medical Genetics 75.1 (January 6, 1998): 45-51.
Source
scopus
Published In
American Journal of Medical Genetics Part A
Volume
75
Issue
1
Publish Date
1998
Start Page
45
End Page
51
DOI
10.1002/(SICI)1096-8628(19980106)75:1<45::AID-AJMG10>3.0.CO;2-S

Variegated aneuploidy in two siblings: phenotype, genotype, CENP-E analysis, and literature review.

Cytogenetic studies of 2 sisters with mild microcephaly, growth deficiency, and mild errors of morphogenesis demonstrated a unique combination of multiple trisomies, most often involving chromosomes 8 and 18 either together as sole trisomies or in combination with other chromosomes. Since neither sib has phenotypic anomalies associated with trisomy 8 or 18 mosaicism, the trisomies likely did not occur during embryogenesis, but later possibly due to a predisposition for mitotic instability. To determine if the observed chromosome instability may be related to centromere function, metaphase cells were characterized by immunofluorescence of the centromere protein, CENP-E. Hybridization of CENP-E antibodies, in combination with in situ hybridization of a chromosome 8 or 18 alpha-satellite probe, showed hybridization to chromosomes 8 and 18 in both normal and aneuploid cells from each patient. These data indicate that the chromosomes in each child contain functional and active centromeres. The clinical and cytogenetic findings in these 2 individuals are compared with 7 other previously reported individuals, each of whom have similar findings. Together, these studies support the notion that a recessive mitotic mutant may be responsible for the chromosomal mosaicism and for the resulting clinical phenotype.

Authors
Flejter, WL; Issa, B; Sullivan, BA; Carey, JC; Brothman, AR
MLA Citation
Flejter, WL, Issa, B, Sullivan, BA, Carey, JC, and Brothman, AR. "Variegated aneuploidy in two siblings: phenotype, genotype, CENP-E analysis, and literature review." Am J Med Genet 75.1 (January 6, 1998): 45-51. (Review)
PMID
9450856
Source
pubmed
Published In
American Journal of Medical Genetics Part A
Volume
75
Issue
1
Publish Date
1998
Start Page
45
End Page
51

Immunolocalization of CENP-A suggests a distinct nucleosome structure at the inner kinetochore plate of active centromeres.

The trilaminar kinetochore directs the segregation of chromosomes in mitosis and meiosis. Despite its importance, the molecular architecture of this structure remains poorly understood [1]. The best known component of the kinetochore plates is CENP-C, a protein that is required for kinetochore assembly [2], but whose molecular role in kinetochore structure and function is unknown. Here we have raised for the first time monospecific antisera to CENP-A [3], a 17 kD centromere-specific histone variant that is 62% identical to the carboxy-terminal domain of histone H3 [4,5] and that resembles the yeast centromeric component CSE4 [6]. We have found by simultaneous immunofluorescence with centromere antigens of known ultrastructural location that CENP-A is concentrated in the region of the inner kinetochore plate at active centromeres. Because CENP-A was previously shown to co-purify with nucleosomes [7], our data suggest a specific nucleosomal substructure for the kinetochore. In human cells, these kinetochore-specific nucleosomes are enriched in alpha-satellite DNA [8]. However, the association of CENP-A with neocentromeres lacking detectable alpha-satellite DNA, and the lack of CENP-A association with alpha-satellite-rich inactive centromeres of dicentric chromosomes together suggest that CENP-A association with kinetochores is unlikely to be determined solely by DNA sequence recognition. We speculate that CENP-A binding could be a consequence of epigenetic tagging of mammalian centromeres.

Authors
Warburton, PE; Cooke, CA; Bourassa, S; Vafa, O; Sullivan, BA; Stetten, G; Gimelli, G; Warburton, D; Tyler-Smith, C; Sullivan, KF; Poirier, GG; Earnshaw, WC
MLA Citation
Warburton, PE, Cooke, CA, Bourassa, S, Vafa, O, Sullivan, BA, Stetten, G, Gimelli, G, Warburton, D, Tyler-Smith, C, Sullivan, KF, Poirier, GG, and Earnshaw, WC. "Immunolocalization of CENP-A suggests a distinct nucleosome structure at the inner kinetochore plate of active centromeres." Curr Biol 7.11 (November 1, 1997): 901-904.
PMID
9382805
Source
pubmed
Published In
Current Biology
Volume
7
Issue
11
Publish Date
1997
Start Page
901
End Page
904

Characterization of neo-centromeres in marker chromosomes lacking detectable alpha-satellite DNA.

Recent studies have implicated alpha-satellite DNA as an integral part of the centromere, important for the normal segregation of human chromosomes. To explore the relationship between the normal functioning centromere and alpha-satellite DNA, we have studied eight accessory marker chromosomes in which fluorescence in-situ hybridization could detect neither pancentromeric nor chromosome-specific alpha-satellite DNA. These accessory marker chromosomes were present in the majority of or all cells analyzed and appeared mitotically stable, thereby indicating the presence of a functional centromere. FISH analysis with both chromosome-specific libraries and single-copy YACs, together with microsatellite DNA studies, allowed unequivocal identification of both the origin and structure of these chromosomes. All but one of the marker chromosomes were linear mirror image duplications, and they were present along with either two additional normal chromosomes or with one normal and one deleted chromosome. Indirect immunofluorescence analysis revealed that the centromere protein CENP-B was not present on these markers; however, both CENP-C and CENP-E were present at a position defining a 'neo-centromere'. These studies provide insight into a newly defined class of marker chromosomes that lack detectable alpha-satellite DNA. At least for such marker chromosomes, alpha-satellite DNA at levels detectable by FISH appears unnecessary for chromosome segregation or for the association of CENP-C and CENP-E at a functional centromere.

Authors
Depinet, TW; Zackowski, JL; Earnshaw, WC; Kaffe, S; Sekhon, GS; Stallard, R; Sullivan, BA; Vance, GH; Van Dyke, DL; Willard, HF; Zinn, AB; Schwartz, S
MLA Citation
Depinet, TW, Zackowski, JL, Earnshaw, WC, Kaffe, S, Sekhon, GS, Stallard, R, Sullivan, BA, Vance, GH, Van Dyke, DL, Willard, HF, Zinn, AB, and Schwartz, S. "Characterization of neo-centromeres in marker chromosomes lacking detectable alpha-satellite DNA." Hum Mol Genet 6.8 (August 1997): 1195-1204.
PMID
9259264
Source
pubmed
Published In
Human Molecular Genetics
Volume
6
Issue
8
Publish Date
1997
Start Page
1195
End Page
1204

Centromeres of the human chromosomes

The centromere, recognized cytologically as the primary constriction, is essential for chromosomal attachment to the spindle and for proper segregation of mitotic and meiotic chromosomes. Considerable progress has been made in identifying both DNA and protein components of the centromere and kinetochore complex in mammalian chromosomes, including definition of specific motor proteins with demonstrable functions in chromosome movement. Searches for possible environmental influences on chromosome disjunction might logically be based on known components of the segregation apparatus, both intrinsic and extrinsic to the chromosomes themselves. This article reviews available information on both DNA and protein components of the centromere of mammalian, particularly human, chromosomes and summarizes our current understanding of their role(s) in facilitating normal chromosome behavior in mitosis and meiosis.

Authors
Sullivan, BA; Schwartz, S; Willard, HF
MLA Citation
Sullivan, BA, Schwartz, S, and Willard, HF. "Centromeres of the human chromosomes." Environmental and Molecular Mutagenesis 28.3 (November 23, 1996): 182-191.
Source
scopus
Published In
Environmental and Molecular Mutagenesis
Volume
28
Issue
3
Publish Date
1996
Start Page
182
End Page
191
DOI
10.1002/(SICI)1098-2280(1996)28:3<182::AID-EM4>3.0.CO;2-G

Evidence for structural heterogeneity from molecular cytogenetic analysis of dicentric Robertsonian translocations.

Most Robertsonian translocations are dicentric, suggesting that the location of chromosomal breaks leading to their formation occur in the acrocentric short arm. Previous cytogenetic and molecular cytogenetic studies have shown that few Robertsonian translocations retain ribosomal genes or beta-satellite DNA. Breakpoints in satellite III DNA, specifically between two chromosome 14-specific subfamilies, pTRS-47 and pTRS-63, have been indicated for most of the dicentric 14q21q and 13q14q translocations that have been studied. We have analyzed the structure of 36 dicentric translocations, using several repetitive DNA probes that localize to the acrocentric short arm. The majority of the translocations retained satellite III DNA, while others proved variable in structure. Of 10 14q21q translocations analyzed, satellite III DNA was undetected in 1; 6 retained one satellite III DNA subfamily, pTRS-47; and 3 appeared to contain two 14-specific satellite III DNA sub-families, pTRS-47 and pTRS-63. In 10/11 translocations involving chromosome 15, the presence of satellite III DNA was observed. Our results show that various regions of the acrocentric short arm, and, particularly, satellite III DNA sequences, are involved in the formation of Robertsonian translocations.

Authors
Sullivan, BA; Jenkins, LS; Karson, EM; Leana-Cox, J; Schwartz, S
MLA Citation
Sullivan, BA, Jenkins, LS, Karson, EM, Leana-Cox, J, and Schwartz, S. "Evidence for structural heterogeneity from molecular cytogenetic analysis of dicentric Robertsonian translocations." Am J Hum Genet 59.1 (July 1996): 167-175.
PMID
8659523
Source
pubmed
Published In
The American Journal of Human Genetics
Volume
59
Issue
1
Publish Date
1996
Start Page
167
End Page
175

Centromeres of human chromosomes.

The centromere, recognized cytologically as the primary constriction, is essential for chromosomal attachment to the spindle and for proper segregation of mitotic and meiotic chromosomes. Considerable progress has been made in identifying both DNA and protein components of the centromere and kinetochore complex in mammalian chromosomes, including definition of specific motor proteins with demonstrable functions in chromosome movement. Searches for possible environmental influences on chromosome disjunction might logically be based on known components of the segregation apparatus, both intrinsic and extrinsic to the chromosomes themselves. This article reviews available information on both DNA and protein components of the centromere of mammalian, particularly human, chromosomes and summarizes our current understanding of their role(s) in facilitating normal chromosome behavior in mitosis and meiosis.

Authors
Sullivan, BA; Schwartz, S; Willard, HF
MLA Citation
Sullivan, BA, Schwartz, S, and Willard, HF. "Centromeres of human chromosomes." Environ Mol Mutagen 28.3 (1996): 182-191. (Review)
PMID
8908179
Source
pubmed
Published In
Environmental and Molecular Mutagenesis
Volume
28
Issue
3
Publish Date
1996
Start Page
182
End Page
191
DOI
10.1002/(SICI)1098-2280(1996)28:3<182::AID-EM4>3.0.CO;2-G

Identification of centromeric antigens in dicentric Robertsonian translocations: CENP-C and CENP-E are necessary components of functional centromeres.

Robertsonian translocations are the most common structural dicentric rearrangements in humans. The stability of these dicentrics is attributed to the inactivation of one centromere by mechanisms which are currently unknown. The presence and amounts of centromeric proteins (CENPs) differ between the centromeres of the few dicentrics which have been studied, providing a limited understanding of the protein components necessary for centromeric function. However, CENP-C previously has been observed only at the active centromeres in two dicentric chromosomes. In the present investigation, the presence and localizations of several centromeric antigens, CENP-B, -C and -E, have been determined in 12 dicentric Robertsonian translocations. Each translocation was studied initially using in situ hybridization with alpha-satellite DNA probes to determine the active centromere. Subsequent immunofluorescence of monoclonal and polyclonal antibodies generated to various centromeric antigens demonstrated that the protein composition differs at the two centromeres of these dicentric translocations. While CENP-B was present at both active and inactive centromeres, CENP-C and -E were located at active centromeres only in the majority of translocations. These results confirm previous observations of CENP-C at active centromeres and provide the first evidence that CENP-E correlates with active centromeres as well, demonstrating that at least two specific centromeric proteins are required for human centromeric function.

Authors
Sullivan, BA; Schwartz, S
MLA Citation
Sullivan, BA, and Schwartz, S. "Identification of centromeric antigens in dicentric Robertsonian translocations: CENP-C and CENP-E are necessary components of functional centromeres." Hum Mol Genet 4.12 (December 1995): 2189-2197.
PMID
8634687
Source
pubmed
Published In
Human Molecular Genetics
Volume
4
Issue
12
Publish Date
1995
Start Page
2189
End Page
2197

Application of FISH to complex chromosomal rearrangements associated with chronic myelogenous leukemia.

Identification of complex chromosomal rearrangements can be difficult, due either to the limited number and sometimes poor quality of metaphases in bone marrow preparations or to the nature of the rearrangements. Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries in conjunction with a cosmid probe for the c-ABL oncogene was performed to substantiate the preliminary G-banded karyotypes of six patients with chronic myelogenous leukemia (CML). Our results indicate that FISH is sufficiently sensitive to detect complex and subtle rearrangements, even in bone marrow preparations with suboptimal metaphases, and can provide valuable corroborative information.

Authors
Sullivan, BA; Schiffer, CA; Patil, SR; Hulseberg, D; Leana-Cox, J; Schwartz, S
MLA Citation
Sullivan, BA, Schiffer, CA, Patil, SR, Hulseberg, D, Leana-Cox, J, and Schwartz, S. "Application of FISH to complex chromosomal rearrangements associated with chronic myelogenous leukemia." Cancer Genet Cytogenet 82.2 (July 15, 1995): 93-99.
PMID
7664251
Source
pubmed
Published In
Cancer Genetics and Cytogenetics
Volume
82
Issue
2
Publish Date
1995
Start Page
93
End Page
99

Analysis of centromeric activity in Robertsonian translocations: implications for a functional acrocentric hierarchy.

Approximately 90% of human Robertsonian translocations occur between nonhomologous acrocentric chromosomes, producing dicentric elements which are stable in meiosis and mitosis, implying that one centromere is functionally inactivated or suppressed. To determine if this suppression is random, centromeric activity in 48 human dicentric Robertsonian translocations was assigned by assessment of the primary constrictions using dual color fluorescence in situ hybridization (FISH). Preferential activity/constriction of one centromere was observed in all except three different rearrangements. The activity is meiotically stable since intrafamilial consistency of a preferentially active centromere existed in members of six families. These results support evidence for nonrandom centromeric activity in humans and, more importantly, suggest a functional hierarchy in Robertsonian translocations with the chromosome 14 centromere most often active and the chromosome 15 centromere least often active.

Authors
Sullivan, BA; Wolff, DJ; Schwartz, S
MLA Citation
Sullivan, BA, Wolff, DJ, and Schwartz, S. "Analysis of centromeric activity in Robertsonian translocations: implications for a functional acrocentric hierarchy." Chromosoma 103.7 (December 1994): 459-467.
PMID
7720412
Source
pubmed
Published In
Chromosoma
Volume
103
Issue
7
Publish Date
1994
Start Page
459
End Page
467

Clarification of subtle reciprocal rearrangements using fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries as painting probes was applied in the analysis of six subtle, balanced chromosome rearrangements. Both fresh and older slides, some of which had been previously G-banded, were used to determine if FISH could identify unambiguously very small amounts of translocated material. Our results indicate that this procedure can clearly and precisely distinguish the specific components of extremely subtle translocations, in different cell types, such as leukocytes, aminocytes, and chorionic villus, and irregardless of preparation age. This ability makes FISH a valuable tool in clinical cytogenetics for the confirmation of preliminary G-banded karyotypes.

Authors
Sullivan, BA; Leana-Cox, J; Schwartz, S
MLA Citation
Sullivan, BA, Leana-Cox, J, and Schwartz, S. "Clarification of subtle reciprocal rearrangements using fluorescence in situ hybridization." Am J Med Genet 47.2 (August 15, 1993): 223-230.
PMID
8213910
Source
pubmed
Published In
American Journal of Medical Genetics Part A
Volume
47
Issue
2
Publish Date
1993
Start Page
223
End Page
230
DOI
10.1002/ajmg.1320470217

Characterization of de novo duplications in eight patients by using fluorescence in situ hybridization with chromosome-specific DNA libraries.

Fluorescence in situ hybridization (FISH) with chromosome-specific DNA libraries was performed on samples from eight patients with de novo chromosomal duplications. In five cases, the clinical phenotype and/or cytogenetic evaluations suggested a likely origin of the duplicated material. In the remaining three cases, careful examination of the GTG-banding pattern indicated multiple possible origins; hybridization with more than one chromosome-specific library was performed on two of these cases. In all cases, FISH conclusively identified the chromosomal origin of the duplicated material. In addition, the hybridization pattern was useful in quantitatively delineating the duplication in two cases.

Authors
Leana-Cox, J; Levin, S; Surana, R; Wulfsberg, E; Keene, CL; Raffel, LJ; Sullivan, B; Schwartz, S
MLA Citation
Leana-Cox, J, Levin, S, Surana, R, Wulfsberg, E, Keene, CL, Raffel, LJ, Sullivan, B, and Schwartz, S. "Characterization of de novo duplications in eight patients by using fluorescence in situ hybridization with chromosome-specific DNA libraries." Am J Hum Genet 52.6 (June 1993): 1067-1073.
PMID
8503441
Source
pubmed
Published In
The American Journal of Human Genetics
Volume
52
Issue
6
Publish Date
1993
Start Page
1067
End Page
1073
Show More

Research Areas:

  • Aneuploidy
  • Cell Cycle
  • Centromere
  • Centromere Protein B
  • Chromatids
  • Chromatin
  • Chromatin Immunoprecipitation
  • Chromosomal Instability
  • Chromosomal Proteins, Non-Histone
  • Chromosome Aberrations
  • Chromosome Deletion
  • Chromosome Disorders
  • Chromosome Segregation
  • Chromosomes
  • Chromosomes, Human
  • DNA
  • DNA Damage
  • DNA Methylation
  • DNA Repair
  • DNA Replication
  • DNA, Ribosomal
  • DNA, Satellite
  • DNA-Binding Proteins
  • Epigenesis, Genetic
  • Epigenomics
  • Eukaryota
  • Fluorescent Antibody Technique
  • Gene Expression Regulation
  • Gene Silencing
  • Genome
  • Heterochromatin
  • Histone Code
  • Histones
  • Immunofluorescence
  • Microscopy, Fluorescence
  • Mitosis
  • Molecular Probe Techniques
  • Polymorphism, Genetic
  • Telomere
  • Transcription
  • Translocation, Genetic