BRCA1 and breast cancer: In support of this notion, we found that both RAD51 and BARD1, a component of the BRCA1 breast cancer susceptibility HDR protein complex, readily accumulate at telomeres in Rap1−/− MEFs expressing TRF2ΔB and in WT MEFs expressing TRF2ΔB; L286R (Fig. 3a–c and Supplementary Fig. 3a).