title: Regulation of human estrogen receptor alpha-mediated gene transactivation in Saccharomyces cerevisiae by human coactivator and corepressor proteins.
abstract: Human estrogen receptor alpha (ERalpha)-mediated transcription activation was evaluated in the yeast Saccharomyces cerevisiae using both the native ERalpha and a G400V variant. A previous study demonstrated that coexpression of human SRC-1, a potent stimulator of ERalpha function in mammalian cells, potentiated ERalpha-mediated gene expression in yeast over five-fold in an E(2)-dependent manner. In the present study, two additional human coactivator proteins were shown to potentiate ERalpha-mediated gene expression in yeast. SRC2 potentiated transactivation two- to three-fold while SRC3 potentiated transactivation five- to eight-fold. Both human coactivators potentiated both the native ERalpha and the G400V variant in an E(2)-dependent manner. The effect of a human corepressor protein was also evaluated in yeast. Repressor of estrogen receptor activity (REA) did not affect E(2)-induced transactivation by ERalpha (either isoform). However, in a strain that coexpressed human SRC1, REA reduced E(2)-induced transactivation to that observed with ERalpha alone. Furthermore, repression of SRC1 potentiation was specific for the native ERalpha since REA had no effect on SRC1 potentiation of the G400V variant. Additionally, REA repression was specific for SRC1 since potentiation of ERalpha (either isoform) transactivation by SRC2 and SRC3 was unaffected by coexpression of REA. These results support previous observations in mammalian cells that REA does not prevent ERalpha from binding to DNA but does inhibit potentiation of ERalpha-mediated transactivation by SRC1. The results in the present study further characterize REA-mediated repression, and demonstrate the utility of this yeast system for dissecting molecular mechanisms involved in regulating gene transactivation by human ERalpha.
authors.affiliation: BitTech, Inc., Westlake Village, CA 91361, USA. gab@bittech.net
authors.forename: Grant A
authors.initials: GA
authors.lastname: Bitter
mesh_terms: D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter / Q000187:drug effects; D051548:Histone Acetyltransferases / Q000502:physiology*; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism; D056920:Nuclear Receptor Coactivator 1; D051958:Nuclear Receptor Coactivator 2 / Q000502:physiology*; D056921:Nuclear Receptor Coactivator 3; D000091402:Prohibitins; D011485:Protein Binding; D012097:Repressor Proteins / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D047628:Estrogen Receptor alpha; D050505:Mutant Proteins; D051958:Nuclear Receptor Coactivator 2; C000717331:PHB2 protein, human; D000091402:Prohibitins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D004958:Estradiol; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538866:NCOA3 protein, human; D056920:Nuclear Receptor Coactivator 1; D056921:Nuclear Receptor Coactivator 3