Background
The breast cancer-associated antigen BRCAA1, also designated ARID domaincontaining protein 4B (ARID4B), Sin3-associated polypeptide p180 (SAP180),or Retinoblastoma-binding protein 1-like 1 (RBBP1L1 or RBP1L1), shares 37% amino acid identity and an identical antigen epitope, SSKKQKRSHK, with Rb binding protein 1. High expression of BRCAA1 mRNA has been found in human breast, lung, colon, pancreatic and ovarian cancers, as well as in normal testis. This expression pattern indicates that BRCAA1 can be uses as a molecular marker for a broad range of human malignancies. BRCAA1 also interacts with RBBP1/ARID4A and regulates genomic imprinting at the Prader-WIlli syndrome (PWS)/Angelman syndrome (AS) domain.