A truncated splice variant of human BARD1 that lacks the RING finger and ankyrin repeats.

BARD1 is a crucial partner of the breast and ovarian tumor suppressor BRCA1 required for ubiquitin ligase activity and for reciprocal stabilization in cells. We report here an alternatively spliced human BARD1 mRNA variant (BARD1DeltaRIN) isolated from a HeLa cell cDNA library. It is characterized by deletion of exons 2-6 that encode most of the RING finger domain and the entire span of ankyrin repeats. DeltaRIN transcript was detected in all breast cancer-cell lines studied although its protein expression level was low. DeltaRIN does not interact with BRCA1, whereas it interacts with and colocalizes with CstF-50 to cytoplasmic dots. Hence, a deletion variant of BARD1 occurs in cells and may play a distinct role with CstF-50.