Figure 6

The MEK-1 inhibitor reduces the E2-induced binding of Sp1 and ER-α to the BRCA1 promoter. Nuclear protein extracts (200 μg) were obtained from MCF-7 cells cultured for 1.5 hours in Dulbecco's modified Eagle's medium containing 5% charcoal dextran-stripped fetal bovine serum containing vehicle (DMEM), or DMEM plus 10 nmol/l 17β-estradiol (E2), the MEK-1 (mitogen-activated protein kinase kinase-1) inhibitor PD98059, or E2 plus PD98059. DNA:protein complexes were generated by coincubation of nuclear extracts with the wild-type specificity protein (Sp)1/activator protein (AP)-1 oligonucleotide and separated by SDS-PAGE. The recruitment of Sp1, total ER-α, or phosphorylated ER-α was visualized by Western blotting with specific antibodies. Panels are representative of two independent experiments. Numbers indicate molecular weight markers (kDa).