Radiation Enhances Caspase 3 Cleavage of Rad51 in BRCA2-Defective Cells

Brown, E. T., Robinson-Benion, C. and Holt, J. T. Radiation Enhances Caspase 3 Cleavage of Rad51 in BRCA2-Defective Cells. Radiat. Res. 169, 595–601 (2008). After DNA damage, caspases cleave and activate proteins involved in cell death by apoptosis but also cleave and inactivate proteins implicated in DNA repair. Here we report a rapid onset of Rad51 cleavage by caspase 3 in BRCA2-defective mouse and human cells. This rapid cleavage was reduced markedly by transfer of full-length human BRCA2 into BRCA2-defective mouse or human cells, which also blocked the association of caspase 3 and Rad51 proteins. Overall caspase 3 activity was increased in BRCA2-defective cells, but the time course was much slower than that for Rad51 cleavage. We further showed that caspase 3 cleavage of Rad51 resulted in a functional decrease in Rad51 strand exchange activity and that inhibition of caspase 3 activity increased Rad51 protein levels and Rad51 foci. These findings indicate that BRCA2 inhibits Rad51 cleavage and subsequent apoptosis.