title: Persistently bound Ku at DNA ends attenuates DNA end resection and homologous recombination.
abstract: DNA double strand breaks (DSBs) are repaired by non-homologous end joining (NHEJ) or homologous recombination (HR). The DNA cell cycle stage and resection of the DSB ends are two key mechanisms which are believed to push DSB repair to the HR pathway. Here, we show that the NHEJ factor Ku80 associates with DSBs in S phase, when HR is thought to be the preferred repair pathway, and its dynamics/kinetics at DSBs is similar to those observed for Ku80 in non-S phase in mammalian cells. A Ku homolog from Mycobacterium tuberculosis binds to and is retained at DSBs in S phase and was used as a tool to determine if blocking DNA ends affects end resection and HR in mammalian cells. A decrease in DNA end resection, as marked by IR-induced RPA, BrdU, and Rad51 focus formation, and HR are observed when Ku deficient rodent cells are complemented with Mt-Ku. Together, this data suggests that Ku70/80 binds to DSBs in all cell cycle stages and is likely actively displaced from DSB ends to free the DNA ends for DNA end resection and thus HR to occur.
authors.affiliation: Division of Molecular Radiation Biology, Department of Radiation Oncology, The University of Texas Southwestern Medical Center, 2201 Inwood Rd, Dallas, TX 75390, USA.
authors.forename: Zhengping
authors.initials: Z
authors.lastname: Shao
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Davis
authors.forename: Kazi R
authors.initials: KR
authors.lastname: Fattah
authors.forename: Sairei
authors.initials: S
authors.lastname: So
authors.forename: Jingxin
authors.initials: J
authors.lastname: Sun
authors.forename: Kyung-Jong
authors.initials: KJ
authors.lastname: Lee
authors.forename: Lynn
authors.initials: L
authors.lastname: Harrison
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D059765:Homologous Recombination / Q000235:genetics*; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D051135:Rad51 Recombinase / Q000378:metabolism; D016196:S Phase
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D004247:DNA; D051135:Rad51 Recombinase; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen