p21 promotes error-free replication-coupled DNA double-strand break repair.

Journal article

p21 is a well-established regulator of cell cycle progression. The role of p21 in DNA repair, however, remains poorly characterized. Here, we describe a critical role of p21 in a replication-coupled DNA double-strand break (DSB) repair that is mechanistically distinct from its cell cycle checkpoint function. We demonstrate that p21-deficient cells exhibit elevated chromatid-type aberrations, including gaps and breaks, dicentrics and radial formations, following exposure to several DSB-inducing agents. p21-/- cells also exhibit an increased DNA damage-inducible DNA-PKCS S2056 phosphorylation, indicative of elevated non-homologous DNA end joining. Concomitantly, p21-/- cells are defective in replication-coupled homologous recombination (HR), exhibiting decreased sister chromatid exchanges and HR-dependent repair as determined using a crosslinked GFP reporter assay. Importantly, we establish that the DSB hypersensitivity of p21-/- cells is associated with increased cyclin-dependent kinase (CDK)-dependent BRCA2 S3291 phosphorylation and MRE11 nuclear foci formation and can be rescued by inhibition of CDK or MRE11 nuclease activity. Collectively, our results uncover a novel mechanism by which p21 regulates the fidelity of replication-coupled DSB repair and the maintenance of chromosome stability distinct from its role in the G1-S phase checkpoint.

Authors: Mauro, M; Rego, M; Boisvert, R; Esashi, F; Cavallo, F

• Publication status: Published
• Journal: Nucleic acids research
• Volume: 40
• Issue: 17
• Pages: 8348-8360
• Publication date: 2012-09-01
• DOI: 10.1093/nar/gks612
• EISSN: 1362-4962
• ISSN: 0305-1048
• Language: English
• Keywords: BRCA2 Protein; Camptothecin; DNA Breaks, Double-Stranded; Mitomycin; Phosphorylation; DNA-Binding Proteins; Chromosomal Instability; HCT116 Cells; Animals; DNA End-Joining Repair; Cross-Linking Reagents; DNA Repair; Cyclin-Dependent Kinase Inhibitor p21; Recombinational DNA Repair; Mice; Humans; Hela Cells; Topoisomerase Inhibitors; DNA Repair Enzymes; DNA Replication; Etoposide; G1 Phase Cell Cycle Checkpoints