title: Factors determining DNA double-strand break repair pathway choice in G2 phase.
abstract: DNA non-homologous end joining (NHEJ) and homologous recombination (HR) function to repair DNA double-strand breaks (DSBs) in G2 phase with HR preferentially repairing heterochromatin-associated DSBs (HC-DSBs). Here, we examine the regulation of repair pathway usage at two-ended DSBs in G2. We identify the speed of DSB repair as a major component influencing repair pathway usage showing that DNA damage and chromatin complexity are factors influencing DSB repair rate and pathway choice. Loss of NHEJ proteins also slows DSB repair allowing increased resection. However, expression of an autophosphorylation-defective DNA-PKcs mutant, which binds DSBs but precludes the completion of NHEJ, dramatically reduces DSB end resection at all DSBs. In contrast, loss of HR does not impair repair by NHEJ although CtIP-dependent end resection precludes NHEJ usage. We propose that NHEJ initially attempts to repair DSBs and, if rapid rejoining does not ensue, then resection occurs promoting repair by HR. Finally, we identify novel roles for ATM in regulating DSB end resection; an indirect role in promoting KAP-1-dependent chromatin relaxation and a direct role in phosphorylating and activating CtIP.
authors.affiliation: Genome Damage and Stability Centre, University of Sussex, East Sussex, UK.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shibata
authors.forename: Sandro
authors.initials: S
authors.lastname: Conrad
authors.forename: Julie
authors.initials: J
authors.lastname: Birraux
authors.forename: Verena
authors.initials: V
authors.lastname: Geuting
authors.forename: Olivia
authors.initials: O
authors.lastname: Barton
authors.forename: Amani
authors.initials: A
authors.lastname: Ismail
authors.forename: Andreas
authors.initials: A
authors.lastname: Kakarougkas
authors.forename: Katheryn
authors.initials: K
authors.lastname: Meek
authors.forename: Gisela
authors.initials: G
authors.lastname: Taucher-Scholz
authors.forename: Markus
authors.initials: M
authors.lastname: Löbrich
authors.forename: Penny A
authors.initials: PA
authors.lastname: Jeggo
mesh_terms: D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D016195:G2 Phase; D006570:Heterochromatin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D053858:Metabolic Networks and Pathways; D011995:Recombination, Genetic
chemical_list: D006570:Heterochromatin