title: Paradoxical decrease in mutant frequencies and chromosomal rearrangements in a transgenic lacZ reporter gene in Ku80 null mice deficient in DNA double strand break repair.
abstract: Repair of DNA double strand breaks (DSB), either by homologous recombination (HR) or nonhomologous end-joining (NHEJ), is essential to maintain genomic stability. To examine the impact of NHEJ deficiency on genomic integrity in Ku80 null (Ku-) mice, the chromosomally integrated shuttle vector pUR288, which includes a lacZ reporter gene, was used to measure mutations in vivo. Unexpectedly, a significant decrease was found in mutant frequencies of Ku- liver (5.04x10(-5)) and brain (4.55x10(-5)) compared to tissues obtained from normal (Ku+) littermates (7.92x10(-5)and 7.30x10(-5), respectively). No significant difference was found in mutant frequencies in spleen from Ku- (7.21x10(-5)) and Ku+ mice (8.16x10(-5)). The determination of the mutant spectrum in lacZ revealed the almost complete absence of chromosomal rearrangements (R) in Ku- tissues (0.5%, 3/616), a notable distinction from Ku+ controls (16.7%, 104/621). These findings suggest that accurate repair of DSB by HR and elimination of cells with unrepaired DNA damage by apoptosis are capable of maintaining genomic stability of the lacZ reporter in Ku- mice.
authors.affiliation: Laboratory of Genetics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, NCI, Room 2B10, Building 37, Bethesda, MD 20892-4256, USA.
authors.forename: Lynne D
authors.initials: LD
authors.lastname: Rockwood
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
authors.forename: Siegfried
authors.initials: S
authors.lastname: Janz
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics* / Q000378:metabolism; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism; D001921:Brain / Q000201:enzymology; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004265:DNA Helicases; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D015321:Gene Rearrangement / Q000235:genetics*; D017930:Genes, Reporter; D000072200:Ku Autoantigen; D008099:Liver / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D013154:Spleen / Q000201:enzymology; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D034961:Antigens, Nuclear; D001324:Autoantigens; D004268:DNA-Binding Proteins; D001616:beta-Galactosidase; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen