title: The aryl hydrocarbon receptor interacts with estrogen receptor alpha and orphan receptors COUP-TFI and ERRalpha1.
abstract: The molecular mechanisms underlying the apparent "cross-talk" between estrogen receptor (ER)- and arylhydrocarbon receptor (AHR)-mediated activities are unknown. To determine how AHR ligand 2, 3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may inhibit ER action and, conversely, to examine how 17-beta-estradiol (E(2)) affects AHR activity, we examined discrete activities of each receptor, i.e., protein-protein interactions, DNA binding, and transcriptional activation. We report that AHR interacts directly with ERalpha, COUP-TF, and ERRalpha1, in a ligand-specific manner in vitro. Unoccupied or beta-napthoflavone (beta-NF)-occupied AHR showed stronger interaction with ERalpha, COUP-TF, and ERRalpha1 than when AHR was occupied by the partial antagonist alpha-naphthoflavone (alpha-NF), indicating a role for ligand in AHR interaction with these proteins. We also report that AHR interacts with COUP-TF in transfected CV-1 cells. In contrast, the AHR nuclear translocator protein (ARNT) did not interact with COUP-TF, ERRalpha1, or ERalpha. We next examined the interaction of either ERalpha or COUP-TF with a consensus xenobiotic response element (XRE). Purified ERalpha did not bind the consensus XRE, but COUP-TFI bound the consensus XRE, suggesting a role for COUP-TF as a AHR/ARNT competitor for XRE binding. In transiently transfected MCF-7 human breast cancer cells, overexpression of COUP-TFI inhibited TCDD-activated reporter gene activity from the CYP1A1 promoter. TCDD inhibited estradiol (E(2))-activated reporter gene activity from a consensus ERE and from the EREs in the pS2 and Fos genes, and COUP-TFI did not block the antiestrogenic activity of TCDD. The specific interaction of COUP-TF with XREs and AHR together with the inhibition of TCDD-induced gene expression by COUP-TF suggests that COUP-TF may regulate AHR action both by direct DNA binding competition and through protein-protein interactions.
authors.affiliation: Department of Biochemistry, University of Louisville School of Medicine, Louisville, Kentucky, 40292, USA. carolyn.klinge@louisville.edu
authors.forename: C M
authors.initials: CM
authors.lastname: Klinge
authors.forename: K
authors.initials: K
authors.lastname: Kaur
authors.forename: H I
authors.initials: HI
authors.lastname: Swanson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D051838:COUP Transcription Factor I; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D020239:Receptor Cross-Talk / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000097983:ERRalpha Estrogen-Related Receptor
chemical_list: D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D051838:COUP Transcription Factor I; D019363:Cytochrome P-450 CYP1A1; D017931:DNA Primers; D004268:DNA-Binding Proteins; D004958:Estradiol; D047628:Estrogen Receptor alpha; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C497396:ARNT protein, human; C497589:NR2F1 protein, human