title: Inhibition of the specific DNA binding activity of the dioxin receptor by phosphatase treatment.
abstract: The dioxin receptor stimulates transcription of the cytochrome P-450IA1 gene in response to dioxin. Exposure of the intracellular dioxin receptor to dioxin leads to a rapid conversion of the receptor from a latent form to a DNA binding species which specifically recognizes dioxin-responsive positive control elements in vitro. In this report, we show that treatment of in vivo or in vitro ligand-activated receptor with potato acid phosphatase significantly reduced or abolished its specific DNA binding activity. This effect was inhibited in the presence of sodium phosphate. In control experiments, the ligand-activated glucocorticoid receptor was not inactivated by phosphatase treatment. Moreover, phosphatase treatment did not induce any detectable degradation of covalently labeled dioxin receptor, arguing against protease contamination as a cause for receptor inactivation. Finally, phosphatase-inactivated dioxin receptor exhibited bona fide levels of ligand binding activity. Taken together, these data suggest that phosphorylation may regulate the DNA binding activity of the ligand-occupied dioxin receptor.
authors.affiliation: Department of Medical Nutrition, Karolinska Institutet, Huddinge University Hospital, Sweden.
authors.forename: I
authors.initials: I
authors.lastname: Pongratz
authors.forename: P E
authors.initials: PE
authors.lastname: Strömstedt
authors.forename: G G
authors.initials: GG
authors.lastname: Mason
authors.forename: L
authors.initials: L
authors.lastname: Poellinger
mesh_terms: D000135:Acid Phosphatase / Q000494:pharmacology*; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D004147:Dioxins / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D010766:Phosphorylation; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D004147:Dioxins; D008024:Ligands; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D014157:Transcription Factors; D004247:DNA; D000135:Acid Phosphatase