p21 promotes error-free replication-coupled DNA double-strand break repair.
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.
Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881, USA.
Maurizio
M
Mauro
Meghan A
MA
Rego
Rebecca A
RA
Boisvert
Fumiko
F
Esashi
Francesca
F
Cavallo
Maria
M
Jasin
Niall G
NG
Howlett
D000818:Animals; D024682:BRCA2 Protein / Q000378:metabolism; D002166:Camptothecin / Q000633:toxicity; D043171:Chromosomal Instability; D003432:Cross-Linking Reagents / Q000633:toxicity; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000502:physiology*; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D005047:Etoposide / Q000633:toxicity; D059585:G1 Phase Cell Cycle Checkpoints; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D000076228:MRE11 Homologue Protein; D051379:Mice; D016685:Mitomycin / Q000633:toxicity; D010766:Phosphorylation; D059767:Recombinational DNA Repair; D059003:Topoisomerase Inhibitors / Q000633:toxicity
D024682:BRCA2 Protein; D003432:Cross-Linking Reagents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; C512689:Mre11a protein, mouse; D059003:Topoisomerase Inhibitors; D016685:Mitomycin; D005047:Etoposide; D000076228:MRE11 Homologue Protein; D045643:DNA Repair Enzymes; D002166:Camptothecin