ERα regulates E2F1 expression in MDA-MB-231 cells. (A) The In vivo binding of ERα protein to the E2F1 promoter. ChIP assays using untreated MDA-MB-231 cells (control; CN) or those treated for 3 days with 1 μM 4OHT. Immunoprecipitation using anti-ERα or IgG was performed in triplicate. The results are presented as the percentage of the input DNA. *indicates that P < 0.05 when compared to the untreated controls. (B) PCR was used to detect E2F1 mRNA in untreated MDA-MB-231 cells or MDA-MB-231 cells treated for 3 days with 1 μM 4OHT. The data shown here are from a representative experiment repeated four times with similar results. (C) MDA-MB- cells 231 transfected with siCN or siE2F1 were treated for 3 days with 1 μM 4OHT when indicated, and cell growth was monitored 4 days after transfection (3 days after 4OHT treatment). The expression of E2F1 protein was monitored by western blot (WB), and β-actin was used as a loading control. The statistical values represent data from four replicate samples.