Deficiency in BRCA2 leads to increase in non-conservative homologous recombination.
The BRCA2 tumor suppressor has been implicated in the maintenance of genomic integrity through a function in cellular responses to DNA damage. The BRCA2 protein directly associates with Rad51, that is essential for repair of double-strand breaks (DSBs) by homologous recombination (HR). In this report, we study the BRCA2-defective Chinese hamster cell mutant V-C8 for its ability to perform homology-directed repair (HDR) between repeated sequences. V-C8 cells were recently shown to be defective in Rad51 foci formation in response to DNA damage. Strikingly, we find that these BRCA2 mutant cells exhibit a strong stimulation of HDR activity compared to the V79 parental cells, which harbor a wild-type BRCA2. Furthermore, molecular characterization of the HDR products shows that loss of BRCA2 in V-C8 cells leads to significant reduction in Rad51-dependent gene conversion but strong enhancement of Rad51-independent single-strand annealing (SSA) events frequency. These data imply that, when HDR by conservative gene conversion is impaired, DSBs usually repaired by this pathway are instead resolved by other non-conservative HDR subpathways. Therefore, high chromosomal instability in BRCA2-deficient cells presumably results from enhancement of error-prone repair mechanisms, such as SSA.
Institut de Pharmacologie et de Biologie Structurale, UMR 5089, C.N.R.S., 205, Route de Narbonne, 31077 Toulouse Cedex 4, France. flol@ipbs.fr
Florence
F
Larminat
Maryse
M
Germanier
Efterpi
E
Papouli
Martine
M
Defais
D000818:Animals; D024682:BRCA2 Protein / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D004351:Drug Resistance / Q000235:genetics; D005785:Gene Conversion / Q000235:genetics; D005839:Gentamicins / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D051135:Rad51 Recombinase; D011995:Recombination, Genetic / Q000235:genetics*
D024682:BRCA2 Protein; D004268:DNA-Binding Proteins; D005839:Gentamicins; C010680:antibiotic G 418; D051135:Rad51 Recombinase