Breast cancer 1, early onset (BRCA1) is a well-known tumor suppressor gene that was originally discovered due to its link with early-onset breast and ovarian cancer in women. The BRCA1 protein contains the following domains: RING finger, RAD51-interaction, and BRCT (BRCA1 C-terminus). The N-terminus RING domain enables binding to several proteins - including BARD1 (BRCA1-associated RING domain protein) - allowing the formation of heterodimers. The RING finger is important for tumor suppressor activity. The RAD51-interaction domain is involved in DNA double-stranded break (DSB) repair.