title: Novel glucocorticoid receptor complex with DNA element of the hormone-repressed POMC gene.
abstract: Previous studies defined a DNA element necessary for glucocorticoid repression of the pro-opiomelanocortin (POMC) gene. The glucocorticoid receptor (GR) binds this negative glucocorticoid response element (nGRE) with an in vitro affinity similar to that of GR for positive GREs. However, whereas GR binds GREs as homodimers, a novel GR complex which forms with nGRE appears to contain three GR molecules. Biochemical characterization of this complex as well as equilibrium binding studies suggest that it is formed by sequential binding of a GR homodimer followed by binding of a GR monomer on the opposite side of the double helix. The DNA-binding domain (DBD) of GR is sufficient for differential binding of GRE and nGRE, as bacterially-expressed DBD formed unique nGRE complexes that contain three GR polypeptides. Thus, the POMC nGRE provides the first example of an interaction between GR and DNA in which GR binds otherwise than as a homodimer. Despite its high affinity for GR, the nGRE differs significantly from GREs in that it does not activate transcription in any context. As the nGRE appears insufficient on its own to confer hormone responsiveness, other POMC promoter elements are likely to be required to mediate glucocorticoid repression.
authors.affiliation: Institut de Recherches Cliniques de Montréal, Québec, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Drouin
authors.forename: Y L
authors.initials: YL
authors.lastname: Sun
authors.forename: M
authors.initials: M
authors.lastname: Chamberland
authors.forename: Y
authors.initials: Y
authors.lastname: Gauthier
authors.forename: A
authors.initials: A
authors.lastname: De Léan
authors.forename: M
authors.initials: M
authors.lastname: Nemer
authors.forename: T J
authors.initials: TJ
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D046911:Macromolecular Substances; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009838:Oligodeoxyribonucleotides; D011965:Receptors, Glucocorticoid; D011333:Pro-Opiomelanocortin; D003907:Dexamethasone; D004247:DNA; D008156:Luciferases