Michael Kastan

Altered cellular responses to DNA damage can contribute to cancer development, progression, and therapeutic resistance. Mutations in key DNA damage response factors occur across many cancer types, and the DNA damage-responsive gene, TP53, is frequently mutated in a high percentage of cancers. We recently reported that an alternative splicing pathway induced by DNA damage regulates alternative splicing of TP53 RNA and further modulates cellular stress responses. Through damage-induced inhibition of the SMG1 kinase, TP53 pre-mRNA is alternatively spliced to generate TP53b mRNA and p53b protein is required for optimal induction of cellular senescence after ionizing radiation-induced DNA damage. Herein, we confirmed and extended these observations by demonstrating that the ATM protein kinase is required for repression of SMG1 kinase activity after ionizing radiation. We found that the RNA helicase and splicing factor, DDX5, interacts with SMG1, is required for alternative splicing of TP53 pre-mRNA to TP53b and TP53c mRNAs after DNA damage, and contributes to radiation-induced cellular senescence. Interestingly, the role of SMG1 in alternative splicing of p53 appears to be distinguishable from its role in regulating nonsense-mediated RNA decay. Thus, ATM, SMG1, and DDX5 participate in a DNA damage-induced alternative splicing pathway that regulates TP53 splicing and modulates radiation-induced cellular senescence.

Multiple members of the cohesin complex are involved in the regulation of DNA replication and transcription in the vicinity of DNA double-strand breaks and their role(s) are regulated by the ATM kinase.

DNA repair and the cellular response to DNA damage are critical for maintaining genomic stability. Defects in DNA repair or the response to DNA damage encountered from endogenous or external sources results in an increased rate of genetic mutations, often leading to the development of cancer. Inherited mutations in DNA damage response pathway genes often result in cancer susceptibility. The major active pathways for DNA repair in humans are nucleotide excision repair, base excision repair, mismatch DNA repair, translesional DNA synthesis, and homologous recombination or nonhomologous end joining processes for double-strand break repair.

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