Cloning and characterization of a new BRCA1 variant: A role for BRCT domains in apoptosis

BRCA1 is a tumor-suppressor gene responsible for hereditary breast and ovarian cancers. Characterization of alternately spliced forms of BRCA1 may identify the region of the gene responsible for its function. Here, we cloned and characterized a new BRCA1 splicing variant from the breast cancer cell line ZR-75-30. This transcript, named BRCA1-E1aA-Delta2-17, lacks most exons found in full-length BRCA1, but maintains the original reading frame. We detected expression of the BRCA1-E1aA-Delta2-17 transcript in several human cell lines and tumor tissues, and the fusion protein GFP-BRCA1-E1aA-Delta2-17 localized to the nucleus. Likewise, overexpression of the BRCA1-E1aA-Delta2-17 transcript resulted in cell death as measured by the MTT assay, and fluorescence activated cell sorting (FACS) assays confirmed that this was caused by cellular apoptosis. Our data imply that BRCT domains of the BRCA1 play a role in the cellular apoptosis we observed, and suggest that elucidating the specific function of each of the domains could aid in understanding the exact role of the BRCA1 tumor suppressor.