title: Genetic dissection of vertebrate 53BP1: a major role in non-homologous end joining of DNA double strand breaks.
abstract: 53BP1 (p53 binding protein) is a BRCT domain-containing protein that is rapidly recruited to DNA double strand breaks (DSBs). To investigate the role of 53BP1 in the DNA damage response, we generated 53BP1(-/-) cells from the chicken DT40 cell line. As in mammalian cells, mutation of 53BP1 increased cellular sensitivity to ionizing radiation. Although depletion of 53BP1 resulted in checkpoint defects in mammalian cells, DT40 53BP1(-/-) cells had normal intra S phase and G2/M checkpoints. G1 specific radiosensitivity and a higher sensitivity to topoisomerase II suggested defective non-homologous end joining (NHEJ) defects in DT40 53BP1(-/-) cells. Genetic analyses confirm this suggestion as we have demonstrated an epistatic relationship between 53BP1 and the NHEJ genes, Ku70 and Artemis, but not with Rad54, a gene essential for repair of DSBs by homologous recombination. We conclude that the major role of 53BP1 in supporting survival of DT40 cells that have suffered DNA DSBs is in facilitating repair by NHEJ.
authors.affiliation: Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshidakonoe, Sakyo-ku 606-8501, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nakamura
authors.forename: Wataru
authors.initials: W
authors.lastname: Sakai
authors.forename: Takuo
authors.initials: T
authors.lastname: Kawamoto
authors.forename: Ronan T
authors.initials: RT
authors.lastname: Bree
authors.forename: Noel F
authors.initials: NF
authors.lastname: Lowndes
authors.forename: Shunichi
authors.initials: S
authors.lastname: Takeda
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Taniguchi
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000096:biosynthesis; D002453:Cell Cycle; D002645:Chickens; D004247:DNA / Q000737:chemistry*; D004249:DNA Damage; D004265:DNA Helicases; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004720:Endonucleases; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis; D017434:Protein Structure, Tertiary; D011839:Radiation, Ionizing; D011995:Recombination, Genetic; D019076:Transgenes
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D004247:DNA; C426344:DCLRE1C protein, human; D004720:Endonucleases; D004265:DNA Helicases; C103532:RAD54L protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen