Positive regulation of the BRCA1 promoter.

Inherited mutations in the BRCA1 gene, presumably leading to loss of function, confer susceptibility to breast and ovarian neoplasms and are thought to be responsible for approximately 2.5-5% of all breast cancers. It has been suggested that alternative mechanisms, such as disruption of transcription, may also be involved in the suppression of BRCA1 gene expression/function in breast cancers. Therefore, we initiated studies on the BRCA1 transcriptional promoter. Utilizing systematic promoter deletions and transient transfection assays, a 36-base pair region was determined to be important for the positive regulation of BRCA1 transcription. Deletion of this positive regulatory region resulted in a significant loss of promoter activity. Utilizing DNA binding assays, proteins with specific affinities for the positive regulatory region were detected. Disruption of the DNA-protein complexes could affect normal BRCA1 transcription and may contribute to breast cancer susceptibility.