Figure 5.

Repression of Brg1 or Brm blocks E2F transcriptional repression induced by estrogen antagonists. (A) MCF7 and ZR75-1 cells were transfected with an E2F-responsive promoter-driven reporter, E2Luc (12 μg/10 cm dish), producing a basal level of luciferase activity (lane 1). Basal luciferase activity was dramatically repressed by treatment of the cells with estrogen antagonists, as indicated (lanes 2 and 5), while treatment with the ethanol vehicle showed no such effect (lane 10). This repression of luciferase activity by estrogen antagonists was reversed by knockdown of Brg1 or Brm using SiRNA (lanes 3, 4, 7 and 8). A 1 μg portion of βGal vector was included in all transfections as a control. βGal values are comparable in all samples. (B) Immunoblot analysis of Brg1, Brm, and tubulin levels in MCF-7 cells or the cells transfected with control SiRNA, or Brg1 or Brm SiRNA.