RAP80 Antibody: RAP80 was initially identified as zinc-finger containing nuclear protein that is highly expressed in testis and interacts with the retinoid-related testis-associated receptor (RTR). Later experiments revealed that RAP80 is recruited by the Coiled-coil domain 98 (CCDC98) protein to the breast cancer-1 protein BRCA1, allowing the formation of BRCA1 foci in response to DNA damage caused by ionizing radiation. Both RAP80 and CCDC98 are required for DNA damage resistance, G2-M checkpoint control, and DNA repair. Cells depleted of either RAP80 or CCDC98 exhibited increased sensitivity to ionizing radiation, although not as much as in BRCA1-depleted cells, suggesting that RAP80 and CCDC98 control only part of the DNA damage response role of BRCA1. At least four isoforms of RAP80 are known to exist.