Fig. 2. A model for the role of BRCA2 in DSB repair based on Davies et al. (Davies et al., 2001). As discussed in the text, an ‘inactive’ complex between BRCA2 and RAD51 in the nucleus undergoes transition to a form in which RAD51 is ‘active’ in forming nucleoprotein filaments at the sites of DNA damage. The transition may be induced after phosphorylation by kinases such as ATM or ATR activated by DNA damage. The precise role of BRCA1 in these events is unclear, but it is likely to have multiple functions in DNA damage responses. A single RAD51 molecule is shown bound to a single BRCA2 molecule for simplicity. Modified from Venkitaraman, with permission from Elsevier Science (Venkitaraman, 2001).