Chicken ovalbumin upstream promoter-transcription factor interacts with estrogen receptor, binds to estrogen response elements and half-sites, and inhibits estrogen-induced gene expression.
Chicken ovalbumin upstream promoter-transcription factor (COUP-TF) was identified as a low abundance protein in bovine uterus that co-purified with estrogen receptor (ER) in a ligand-independent manner and was separated from the ER by its lower retention on estrogen response element (ERE)-Sepharose. In gel mobility shift assays, COUP-TF bound as an apparent dimer to ERE and ERE half-sites. COUP-TF bound to an ERE half-site with high affinity, Kd = 1.24 nM. In contrast, ER did not bind a single ERE half-site. None of the class II nuclear receptors analyzed, i.e. retinoic acid receptor, retinoid X receptor, thyroid receptor, peroxisome proliferator-activated receptor, or vitamin D receptor, were constituents of the COUP-TF.DNA binding complex detected in gel mobility shift assays. Direct interaction of COUP-TF with ER was indicated by GST "pull-down" and co-immunoprecipitation assays. The nature of the ER ligand influenced COUP-TF-ERE half-site binding. When ER was liganded by the antiestrogen 4-hydroxytamoxifen (4-OHT), COUP-TF-half-site interaction decreased. Conversely, COUP-TF transcribed and translated in vitro enhanced the ERE binding of purified estradiol (E2)-liganded ER but not 4-OHT-liganded ER. Co-transfection of ER-expressing MCF-7 human breast cancer cells with an expression vector for COUP-TFI resulted in a dose-dependent inhibition of E2-induced expression of a luciferase reporter gene under the control of three tandem copies of EREc38. The ability of COUP-TF to bind specifically to EREs and half-sites, to interact with ER, and to inhibit E2-induced gene expression suggests COUP-TF regulates ER action by both direct DNA binding competition and through protein-protein interactions.
Klinge
C M
CM
Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40292, USA. cmklin01@ulkyvm.louisville.edu
Silver
B F
BF
Driscoll
M D
MD
Sathya
G
G
Bambara
R A
RA
Hilf
R
R
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D051838:COUP Transcription Factor I; D002417:Cattle; D002645:Chickens; D016384:Consensus Sequence; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D017930:Genes, Reporter; D006801:Humans; D007700:Kinetics; D010047:Ovalbumin / Q000235:genetics*; D018160:Receptors, Cytoplasmic and Nuclear / Q000276:immunology / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism* / Q000528:radiation effects; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D000097983:ERRalpha Estrogen-Related Receptor
D000911:Antibodies, Monoclonal; D051838:COUP Transcription Factor I; D004247:DNA; D004268:DNA-Binding Proteins; D004967:Estrogens; D010047:Ovalbumin; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D011994:Recombinant Proteins; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C497589:NR2F1 protein, human