Brn-3b promoter activity is strongly stimulated by 17β-estradiol via activation of oestrogen receptor α (ERα). (a) Brn-3b promoter activity following treatment of transfected MCF-7 cells with different concentration of 17β-estradiol. Values have been adjusted with internal control, Renilla luciferase and represent means ± SD of three independent experiments ***indicate statistical significance of p < 0.0001 compared with control. (b) Effect of different oestrogen receptors, ERα or ERβ on Brn-3b (BSX) promoter activity are shown after cotransfection into sensitised MCF-7 cells (grown in stripped serum medium for 48 hours). Promoter activity is adjusted to internal Renilla control and expressed as percentage of levels seen with empty vector only (set at 100%). Values represent data from three independent experiments, expressed as means ± SD. (c) Activation of Brn-3b promoter by ERα can be blocked by the receptor antagonist tamoxifen. Promoter activity is shown after cotransfection of Brn-3b promoter with ERα into sensitised MCF-7 cells (grown in oestrogen-depleted medium for 48 hours) in the presence of 1 μM 4 hydroxy tamoxifen (TAM) compared with untreated control. Promoter activity is adjusted to internal Renilla control and expressed as percentages of levels seen with untreated controls (set at 100%). (d) Brn-3b promoter activity in ER-negative Cos-7 cells treated with estradiol and either transfected ERα or control vector. Data shows luciferase activity in cells transfection of Brn-3b promoter and treatment with either vehicle (-E2) or 10 nM estradiol (+E2) in the absence or presence of ERα.