title: Oxygen metabolism causes chromosome breaks and is associated with the neuronal apoptosis observed in DNA double-strand break repair mutants.
abstract: Cells deficient in a major DNA double-strand break repair pathway (nonhomologous DNA end joining [NHEJ]) have increased spontaneous chromosome breaks; however, the source of these chromosome breaks has remained undefined. Here, we show that the observed spontaneous chromosome breaks are partially suppressed by reducing the cellular oxygen tension. Conversely, elevating the level of reactive oxygen species by overexpressing the antioxidant enzyme superoxide dismutase 1 (SOD1), in a transgenic mouse, increases chromosome breakage. The effect of SOD1 can also be modulated by cellular oxygen tension. The elevated chromosome breakage correlates histologically with a significant increase in the amount of neuronal cell death in Ku86(-/-) SOD1 transgenic embryos over that seen in Ku86(-/-) embryos. Therefore, oxygen metabolism is a major source of the genomic instability observed in NHEJ-deficient cells and, presumably, in all cells.
authors.affiliation: Department of Pathology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles 90089-9176, USA.
authors.forename: Zarir E
authors.initials: ZE
authors.lastname: Karanjawala
authors.forename: Niamh
authors.initials: N
authors.lastname: Murphy
authors.forename: David R
authors.initials: DR
authors.lastname: Hinton
authors.forename: Chih Lin
authors.initials: CL
authors.lastname: Hsieh
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lieber
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear; D017209:Apoptosis; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D019457:Chromosome Breakage; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D005314:Embryonic and Fetal Development / Q000235:genetics; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009154:Mutation; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics; D010100:Oxygen / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D017382:Reactive Oxygen Species; C000606290:SOD1 protein, human; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606512:Xrcc5 protein, mouse; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen; D010100:Oxygen