Regulatory Mechanisms in Transcription Activation by BRCA1

BRCA1 is involved in two fundamental cellular processes: DNA repair and transcriptional regulation. BRCAl C-terminus acts as a transactivation domain and introduction of germ-line mutations, but not benign polymorphisms, abolishes transcriptional activation, suggesting a critical role for this function of BRCAl in cancer development. Our hypothesis is that BRCA1 transactivation function is regulated by an intramolecular interaction. During the past year we focused on three specific aims: 1) map the interaction sites; 2) define the in vivo dominant negative activity of truncations in BRCAl that retain the inhibitory domain but disrupt the transactivation domain; 3) To analyze which mutations abolish transcriptional activation. We performed immunoprecipitations with FLAG-tagged constructs which revealed an in vivo interaction of the C-terminal region with aa 1366-1559, consistent with our hypothesis. We optimized transfection conditions for breast and ovarian cancer cells and are now currently determining if the trans-inhibition is differentially regulated in these cells. In addition, we provided validation for our functional assay, a required step before testing the effect of mutations located in the putative interaction region.
Original contains color plates: All DTIC reproductions will be in black and white.