title: Mechanism of repression of the inhibin alpha-subunit gene by inducible 3',5'-cyclic adenosine monophosphate early repressor.
abstract: The rodent ovary is regulated throughout the reproductive cycle to maintain normal cyclicity. Ovarian follicular development is controlled by changes in gene expression in response to the gonadotropins FSH and LH. The inhibin alpha-subunit gene belongs to a group of genes that is positively regulated by FSH and negatively regulated by LH. Previous studies established an important role for inducible cAMP early repressor (ICER) in repression of alpha-inhibin. These current studies investigate the mechanisms of repression by ICER. It is not clear whether all four ICER isoforms expressed in the ovary can act as repressors of the inhibin alpha-subunit gene. EMSAs demonstrate binding of all isoforms to the inhibin alpha-subunit CRE (cAMP response element), and transfection studies demonstrate that all isoforms can repress the inhibin alpha-subunit gene. Repression by ICER is dependent on its binding to DNA as demonstrated by mutations to ICER's DNA-binding domain. These mutational studies also demonstrate that repression by ICER is not dependent on heterodimerization with CREB (CRE-binding protein). Competitive EMSAs show that ICER effectively competes with CREB for binding to the inhibin alpha CRE in vitro. Chromatin immunoprecipitation assays demonstrate a replacement of CREB dimers bound to the inhibin alpha CRE by ICER dimers in ovarian granulosa cells in response to LH signaling. Thus, there is a temporal association of transcription factors bound to the inhibin alpha-CRE controlling inhibin alpha-subunit gene expression.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, and Center for Reproductive Science, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Anna D
authors.initials: AD
authors.lastname: Burkart
authors.forename: Abir
authors.initials: A
authors.lastname: Mukherjee
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Mayo
mesh_terms: D000818:Animals; D001665:Binding Sites; D051786:Cyclic AMP Response Element Modulator / Q000235:genetics / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D015536:Down-Regulation; D005260:Female; D005786:Gene Expression Regulation; D006062:Gonadotropins / Q000494:pharmacology; D006107:Granulosa Cells / Q000378:metabolism; D006801:Humans; D007265:Inhibins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism / Q000494:pharmacology; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D020033:Protein Isoforms; D051381:Rats; D017207:Rats, Sprague-Dawley; D020218:Response Elements
chemical_list: C497410:CREM protein, human; C497412:Crem protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D006062:Gonadotropins; D020033:Protein Isoforms; C094377:inhibin-alpha subunit; D051786:Cyclic AMP Response Element Modulator; D007265:Inhibins; D007986:Luteinizing Hormone; D004247:DNA