BRCA1 and neoplasm: While BRCA1/BARD1 has been implicated as the E3 for a range of substrates at DNA damage sites, including histone H2A and CtIP [153], several studies suggest that the ligase activity of BRCA1 is not critical for its tumour suppressive functions and role in promoting HR, although its ability to interact with BARD1 through the RING domain and other proteins in the BRCA1-A complex is important [154–156].