title: Role of estrogen receptor ligand and estrogen response element sequence on interaction with chicken ovalbumin upstream promoter transcription factor (COUP-TF).
abstract: Estrogen-responsive genes are regulated by altering the balance of estrogen receptor (ER) interaction with transcription activators and inhibitors. Here we examined the role of ER ligand on ER interaction with the Chicken Ovalbumin Upstream Promoter Transcription Factor (COUP-TF) orphan nuclear receptor. COUP-TF binding to half-site estrogen response elements (EREs) was increased by the addition of estradiol (E2) -liganded ER (E2-ER), but not by ER liganded with the antiestrogens 4-hydroxytamoxifen (4-OHT-ER) or tamoxifen aziridine (TAz-ER). ER did not bind to single half-sites. Conversely, COUP-TF enhanced the ERE binding of purified E2-ER, but did not affect TAz-ER-ERE binding. In contrast, only antiestrogens enhanced direct interaction between ER and COUP-TF as assessed by GST pull-down assays. Identical results were obtained using either purified bovine or recombinant human ERalpha. Co-immunoprecipitation assays showed that ER and COUP-TF interact in extracts from MCF-7 and ERalpha-transfected MDA-MB-231 cells. Here we document that ER ligand impacts COUP-TF-ER interaction. COUP-TF interaction is mediated by the DNA binding and ligand-binding domains of ER. We suggest that changes in ER conformation induced by DNA binding reduce ER-COUP-TF interaction. Transient transfection of human MCF-7 breast cancer cells with a COUP-TFI expression vector repressed E2-induced luciferase reporter gene expression from single or multiple tandem copies of a consensus ERE. COUP-TFI stimulated 4-OHT-induced luciferase activity from a minimal ERE. Alone, COUP-TFI increased transcription from ERE half-sites or a single ERE in a sequence-dependent manner. These data provide evidence that the ERE sequence and its immediate flanking regions influence whether COUP-TF enhances, inhibits, or has no effect on ER ligand-induced ERE reporter gene expression and that COUP-TFI activates gene transcription from ERE half-sites. We suggest that COUP-TFI plays a role in mitigating estrogen-responsive gene expression.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, KY 40292, USA. carolyn.klinge@louisville.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Klinge
mesh_terms: D000818:Animals; D001665:Binding Sites; D001943:Breast Neoplasms; D051838:COUP Transcription Factor I; D002417:Cattle; D002645:Chickens; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000378:metabolism / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008024:Ligands; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D056985:Nuclear Receptor Co-Repressor 2; D010047:Ovalbumin; D011233:Precipitin Tests; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D000071163:Trefoil Factor-1; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D000097983:ERRalpha Estrogen-Related Receptor
chemical_list: D051838:COUP Transcription Factor I; D004268:DNA-Binding Proteins; D004958:Estradiol; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D008024:Ligands; D008156:Luciferases; D056985:Nuclear Receptor Co-Repressor 2; D010047:Ovalbumin; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D012097:Repressor Proteins; D013629:Tamoxifen; D014157:Transcription Factors; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D000097983:ERRalpha Estrogen-Related Receptor; C539130:NCOR2 protein, human; C497589:NR2F1 protein, human; C051838:TFF1 protein, human; C016601:afimoxifene; C031859:tamoxifen aziridine