FIG. 7.

Brn-3a and Brn-3b modulate the activity of an ERE-containing promoter. The CAT assay results show the effect of cotransfection of a reporter construct containing the ERE sequence derived from the vitellogenin gene promoter with Brn-3 expression vectors. Studies were carried out with MCF7 cells, which were grown in medium containing no phenol red and supplemented with dextran-coated charcoal-stripped serum. Cells were either untreated (−) or were stimulated with 10⁻⁸ M 17β-estradiol (+) after transfection. (A) Representative assay showing CAT activity after transfection and the treatments indicated. (B) Results of at least three independent CAT assays showing activity resulting from cotransfection with Brn-3a or Brn-3b with the reporter construct expressed as a percentage of the activity of the empty vector (bar 1). Bar 2 shows the basal activity of the empty vector in stimulated cells, while the effects of overexpression of Brn-3a (bars 3 and 4) or Brn-3b (bars 5 and 6) in untreated or stimulated cells are shown by bars 3 to 6.