Presents a study which demonstrated that breast cancer susceptibility gene BRCA1 transactivates the cyclin-dependent kinase inhibitor p27[supKip1]. Correlation between the expression of p27[supKip1] and the breast cancer susceptibility gene BRCA1; Role of BRCA1 in the transcriptional activation of specific genes; Identification of a putative BRCA1-responsive element in the p27[Kip1] promoter.