title: GATA2-induced silencing and LIM-homeodomain protein-induced activation are mediated by a bi-functional response element in the rat GnRH receptor gene.
abstract: GATA2 transcription factor and LIM homeodomain proteins Islet1 (ISL1) and LIM homeobox 3 (LHX3) are suspected to be involved in gonadotrope cell fate and maintenance. The GnRH receptor gene (Gnrhr), crucial for gonadotrope function, is expressed in the pituitary gland from embryonic day 13.5 onward, well before LH and FSH β-subunits. This expression pattern together with the presence of WGATAR and TAAT motifs in Gnrhr promoter sequences suggests the involvement of early transcription factors in promoter activation. In this study, using a well-characterized transgenic mouse model, GATA2 was found colocalized with Gnrhr promoter activity in the pituitary. Transient transfection of Gnrhr promoter luciferase fusion constructs together with either GATA2 expression vectors or small interfering RNA in gonadotrope cell lines indicated that GATA2, which typically acts as a trans-activator, unexpectedly repressed Gnrhr promoter activity. Using DNA chromatography affinity and EMSA, we demonstrated that GATA2 operates via a response element containing a peculiar palindromic GATA motif that overlaps a critical TAAT motif involved in LHX3/ISL1 trans-activation. Indeed, despite the inhibitory action of GATA2, this element displayed a clear-cut enhancer activity in gonadotrope cells. Chromatin immunoprecipitation assays indicated that GATA2, LHX3, and ISL1 interact with a Gnrhr promoter fragment encompassing this element. The trans-repressive action of GATA2 on Gnrhr promoter activity is likely balanced or even hindered by trans-activating effects of LIM homeodomain proteins via this novel bifunctional LIM/GATA response element. Such a hierarchical interplay may contribute to finely adjust Gnrhr gene expression in gonadotrope cell lineage during pituitary development as well as in the adult animal.
authors.affiliation: University of Paris Diderot Paris 7, Sorbonne Paris Cité, Biologie Fonctionnelle et Adaptative, Centre National de la Recherche Scientifique Equipe d'Accueil Conventionnée 4413, Physiologie de l'Axe Gonadotrope, Bâtiment Buffon, Case Courrier 7007, 75205 Paris Cedex 13, France.
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Schang
authors.forename: Anne
authors.initials: A
authors.lastname: Granger
authors.forename: Bruno
authors.initials: B
authors.lastname: Quérat
authors.forename: Christian
authors.initials: C
authors.lastname: Bleux
authors.forename: Joëlle
authors.initials: J
authors.lastname: Cohen-Tannoudji
authors.forename: Jean-Noël
authors.initials: JN
authors.lastname: Laverrière
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D050989:GATA2 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D017930:Genes, Reporter; D052681:Gonadotrophs / Q000378:metabolism; D060850:LIM-Homeodomain Proteins / Q000378:metabolism*; D049409:Luciferases, Firefly / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D011966:Receptors, LHRH / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements; D015533:Transcriptional Activation
chemical_list: D050989:GATA2 Transcription Factor; C494713:Gata2 protein, rat; D060850:LIM-Homeodomain Proteins; D011966:Receptors, LHRH; D049409:Luciferases, Firefly