Most importantly, the binding with the E2 ubiquitin-conjugating enzyme UbcH5a (MIM# 602961) enables the BRCA1-BARD1 complex to acquire an ubiquitin ligase activity, linked to BRCA1 tumor suppression function by regulating transcription and double stand break (DSB) repair [26,27,28]. This evidence concerns the gene BRCA1 and neoplasm.