This entry includes animal BRCA1 (BREAST CANCER SUSCEPTIBILITY 1) proteins and their homologues from plants.The aimal BRCA1 protein is a E3 ubiquitin-protein ligase that specifically mediates the formation of 'Lys-6'-linked polyubiquitin chains and plays a central role in DNA repair by facilitating cellular responses to DNA damage. It contains an N-terminal zinc-finger domain. It also contains a BRCT C-terminal domain, an approximately 100 amino acid tandem repeat, which appears to act as a phospho-protein binding domain. Arabidopsis BRCA1-related proteins includes AtBRCA1(AT4G21070) and AtBARD1 (AT1G04020). Both are involved in DNA repair in plants. AtBRCA1 can be induced by gamma-rays. AtBARD1, also known as Row1, functions mainly as a REPRESSOR OF WUSCHEL1, which is a transcription repressor required to regulate the maintenance of stem cell populations in shoot meristems.