A role for Rad51C in homologous recombination and genetic stability in human cells
aDept Human Genetics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan, bMazda Hospital, Hiroshima, Japan
AIMS: Rad51 has a central role in homologous recombination repair. Five paralogs of Rad51 have been identified in vertebrates. To investigate the molecular mechanism of homologous recombination in human cells, we disrupted the Rad51C gene via gene targeting. METHODS: We generated Rad51C-deficient cells from the human colon cancer cell line HCT116 using promoterless targeting constructs. RESULTS: The growth rate of Rad51C-deficient cells was significantly lower than that of wild-type cells. The mutants showed mild sensitivity to DNA cross-linking agents. Chromosome aberrations such as gaps and breaks were significantly increased in Rad51C-deficient cells. A reduction of mitomycin C-induced sister chromatid exchange levels was observed in these mutants. These phenotypes were restored by expression of the transfected Rad51C cDNA but not by expression of the XRCC3 cDNA. Rad51C has been shown to be stably associated with XRCC3. CONCLUSIONS: These findings suggest that Rad51C plays a role in homologous recombination repair and genetic stability in human cells, which is consistent with biochemical properties of Rad51C. Since Rad51C mutants in hamster cells exhibited similar phenotypes, functions of Rad51C appear to be well conserved in mammals.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in poster session 796 (Genetic instability).