title: 53BP1 contributes to survival of cells irradiated with X-ray during G1 without Ku70 or Artemis.
abstract: Ionizing radiation (IR) induces a variety of DNA lesions. The most significant lesion is a DNA double-strand break (DSB), which is repaired by homologous recombination or nonhomologous end joining (NHEJ) pathway. Since we previously demonstrated that IR-responsive protein 53BP1 specifically enhances activity of DNA ligase IV, a DNA ligase required for NHEJ, we investigated responses of 53BP1-deficient chicken DT40 cells to IR. 53BP1-deficient cells showed increased sensitivity to X-rays during G1 phase. Although intra-S and G2/M checkpoints were intact, the frequency of isochromatid-type chromosomal aberrations was elevated after irradiation in 53BP1-deficient cells. Furthermore, the disappearance of X-ray-induced gamma-H2AX foci, a marker of DNA DSBs, was prolonged in 53BP1-deficient cells. Thus, the elevated X-ray sensitivity in G1 phase cells was attributable to repair defect for IR-induced DNA-damage. Epistasis analysis revealed that 53BP1 plays a role in a pathway distinct from the Ku-dependent and Artemis-dependent NHEJ pathways, but requires DNA ligase IV. Strikingly, disruption of the 53BP1 gene together with inhibition of phosphatidylinositol 3-kinase family by wortmannin completely abolished colony formation by cells irradiated during G1 phase. These results demonstrate that the 53BP1-dependent repair pathway is important for survival of cells irradiated with IR during the G1 phase of the cell cycle.
authors.affiliation: Department of Biochemistry, Kanazawa Medical University, Daigaku 1-1, Uchinada, Kahoku-gun, Ishikawa 920-0293, Japan. kuni-kmu@kanazawa-med.ac.jp
authors.forename: Kuniyoshi
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Tadashi
authors.initials: T
authors.lastname: Matsui
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kurihara
authors.forename: Hiroko
authors.initials: H
authors.lastname: Shimizu
authors.forename: Noritaka
authors.initials: N
authors.lastname: Adachi
authors.forename: Masamichi
authors.initials: M
authors.lastname: Ishiai
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tauchi
authors.forename: Minoru
authors.initials: M
authors.lastname: Takata
authors.forename: Hideki
authors.initials: H
authors.lastname: Koyama
authors.forename: Takayasu
authors.initials: T
authors.lastname: Date
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D034961:Antigens, Nuclear; D002453:Cell Cycle / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects*; D002645:Chickens; D002869:Chromosome Aberrations / Q000528:radiation effects; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000502:physiology; D004260:DNA Repair / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000172:deficiency*; D004307:Dose-Response Relationship, Radiation; D004351:Drug Resistance; D004720:Endonucleases; D016193:G1 Phase / Q000528:radiation effects*; D016195:G2 Phase / Q000528:radiation effects; D018816:Genes, cdc / Q000528:radiation effects; D006657:Histones / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000502:physiology*; D000072200:Ku Autoantigen; D008954:Models, Biological; D009687:Nuclear Proteins / Q000172:deficiency*; D010750:Phosphoproteins / Q000172:deficiency / Q000502:physiology*; D011836:Radiation Tolerance; D011995:Recombination, Genetic / Q000528:radiation effects; D016196:S Phase / Q000528:radiation effects; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction / Q000187:drug effects; D000071857:Tumor Suppressor p53-Binding Protein 1; D000077191:Wortmannin; D014965:X-Rays
chemical_list: D000730:Androstadienes; D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; C000607893:LIG4 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1; C426344:DCLRE1C protein, human; D004720:Endonucleases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D011088:DNA Ligases; D000072481:DNA Ligase ATP; D000077191:Wortmannin