Figure 3.
REA is an ER-selective coregulator, suppressing transcriptional activation of ERα and ERβ, but not that of PR, RAR, or Gal4-VP16. CHO cells (A and B and D–F) were transfected with 5 ng of the expression vector for various activators and 2 μg of the reporter construct indicated. (A) ERα/(ERE)2-TATA-CAT. (B) ERβ/(ERE)2-TATA-CAT. (D) PR/MMTV-CAT. (E) RAR/DR-5-CAT. (F) Gal4-VP-16/G5-E1-CAT. In C, MDA-MB-231 breast cancer cells were transfected with 100 ng of the expression vector for ERα and 6 μg of the (ERE)2-pS2-CAT reporter. The cells were cotransfected with increasing concentrations of an expression vector for REA as indicated and with a β-galactosidase internal control reporter to correct for transfection efficiency. Cells then were treated for 24 h with 10−8 M ligands (ER, E2; PR, R5020; RAR, all-trans retinoic acid). Cell extracts were prepared, and CAT activity, normalized for β-galactosidase activity, is shown. Values are the means ± SD from three separate experiments. Numbers at the top of the leftmost bar show the fold induction in CAT activity by hormone (receptor-transfected, plus vs. minus hormone) in the absence of added REA.