ATM release at resected double-strand breaks provides heterochromatin reconstitution to facilitate homologous recombination.
Non-homologous end-joining (NHEJ) and homologous recombination (HR) represent the two main pathways for repairing DNA double-strand breaks (DSBs). During the G2 phase of the mammalian cell cycle, both processes can operate and chromatin structure is one important factor which determines DSB repair pathway choice. ATM facilitates the repair of heterochromatic DSBs by phosphorylating and inactivating the heterochromatin building factor KAP-1, leading to local chromatin relaxation. Here, we show that ATM accumulation and activity is strongly diminished at DSBs undergoing end-resection during HR. Such DSBs remain unrepaired in cells devoid of the HR factors BRCA2, XRCC3 or RAD51. Strikingly, depletion of KAP-1 or expression of phospho-mimic KAP-1 allows repair of resected DSBs in the absence of BRCA2, XRCC3 or RAD51 by an erroneous PARP-dependent alt-NHEJ process. We suggest that DSBs in heterochromatin elicit initial local heterochromatin relaxation which is reversed during HR due to the release of ATM from resection break ends. The restored heterochromatic structure facilitates HR and prevents usage of error-prone alternative processes.
Darmstadt University of Technology, Radiation Biology and DNA Repair, Darmstadt, Germany.
Verena
V
Geuting
Christian
C
Reul
Markus
M
Löbrich
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics* / Q000378:metabolism; D024682:BRCA2 Protein / Q000235:genetics; D016466:CHO Cells; D003412:Cricetulus; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D006367:HeLa Cells; D006570:Heterochromatin / Q000235:genetics*; D059765:Homologous Recombination / Q000235:genetics*; D006801:Humans; D012097:Repressor Proteins / Q000235:genetics; D000076183:Tripartite Motif-Containing Protein 28
D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D004268:DNA-Binding Proteins; D006570:Heterochromatin; C112629:RAD51D protein, human; D012097:Repressor Proteins; C110901:X-ray repair cross complementing protein 3; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins