We have focused on the role of RNF168 during HR in BRCA1 deficient cells because of the relevance of BRCA1 loss to cancer etiology, and also since RNF168 has a much more substantial effect on HR in BRCA1-deficient cells (8), as has been found with 53BP1 (9,10,24). The gene discussed is BRCA1; the disease is cancer.