BRCA1  is a human gene, some mutations of which are associated with a significant increase in the risk of breast cancer, as well as other cancers. BRCA1 belongs to a class of genes known as tumor suppressors, which maintains genomic integrity to prevent dangerous genetic changes. The multifactorial BRCA1 protein product is involved in DNA damage repair especially error-free repair of DNA double strand breaks, ubiquitination, transcriptional regulation as well as other functions.The BRCA1 protein is directly involved in the repair of damaged DNA. In the nucleus of many types of normal cells, the BRCA1 protein is thought to interact indirectly with RAD51 during repair of DNA double-strand breaks, though the details and significance of this interaction is the subject of debate.