Effect of Ku80 Deficiency on Mutation Frequencies and Spectra at a LacZ Reporter Locus in Mouse Tissues and Cells

Journal Article · Mon Oct 20 00:00:00 EDT 2008 · PLoS ONE

DOI:https://doi.org/10.1371/journal.pone.0003458· OSTI ID:1627359

Busuttil, Rita A. ^[1]; Muñoz, Denise P. ^[1]; Garcia, Ana Maria ^[2]; Rodier, Francis ^[3]; Kim, Woo Ho ^[4]; Suh, Yousin ^[5]; Hasty, Paul ^[2]; Campisi, Judith ^[1]; Vijg, Jan ^[1]

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1. Buck Institute for Age Research, Novato, CA (United States)
2. University of Texas at San Antonio, TX (United States)
3. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
4. Seoul National University (Korea, Republic of)
5. Albert Einstein College of Medicine, Bronx, NY (United States)

Non-homologous end joining (NHEJ) is thought to be an important mechanism for preventing the adverse effects of DNA double strand breaks (DSBs) and its absence has been associated with premature aging. To investigate the effect of inactivated NHEJ on spontaneous mutation frequencies and spectra in vivo and in cultured cells, we crossed a Ku80- deficient mouse with mice harboring a lacZ-plasmid-based mutation reporter. We analyzed various organs and tissues, as well as cultured embryonic fibroblasts, for mutations at the lacZ locus. When comparing mutant with wild-type mice, we observed a significantly higher number of genome rearrangements in liver and spleen and a significantly lower number of point mutations in liver and brain. The reduced point mutation frequency was not due to a decrease in small deletion mutations thought to be a hallmark of NHEJ, but could be a consequence of increased cellular responses to unrepaired DSBs. Indeed, we found a substantial increase in persistent 53BP1 and cH2AX DNA damage foci in Ku80^-/- as compared to wild-type liver. Treatment of cultured Ku80-deficient or wild-type embryonic fibroblasts, either proliferating or quiescent, with hydrogen peroxide or bleomycin showed no differences in the number or type of induced genome rearrangements. However, after such treatment, Ku80-deficient cells did show an increased number of persistent DNA damage foci. These results indicate that Ku80-dependent repair of DNA damage is predominantly error-free with the effect of alternative more error-prone pathways creating genome rearrangements only detectable after extended periods of time, i.e., in young adult animals. The observed premature aging likely results from a combination of increased cellular senescence and an increased load of stable, genome rearrangements.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Institutes of Health (NIH)
• Grant/Contract Number: AC02-05CH11231; AG17242
• OSTI ID: 1627359
• Journal Information: PLoS ONE, Vol. 3, Issue 10; ISSN 1932-6203
• Publisher: Public Library of Science
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
point mutation
mammalian genomics
non-homologous end joining
DNA damage
deletion mutation
apoptosis
aging and cancer
liver