Expression of the Estrogen-Regulated pS2 Gene in MCF-7 Human Breast Cancer Cells

In vivo footprinting was utilized to examine the estrogen-responsive pS2 gene in MCF-7 human breast cancer cells. Estrogen treatment resulted in an extensive region of protection within and adjacent to the pS2 estrogen response element ERE . The ERE was also strongly protected after addition of either 4-hydroxytamoxifen and ICI 182,780, but the pattern of protection was distinct with each of these antiestrogens. Protein-DNA interactions in several other regions of the pS2 promoter were also differentially affected by estrogen and antiestrogen treatment. The TATA and CAAT sequences in the proximal promoter were protected in MCF-7 cells in the presence and in the absence of hormone, but were flanked by hypersensitive sites, which were unaffected by hormone treatment.