Egr-1 binds the GnRH promoter to mediate the increase in gene expression by insulin.
Insulin increases gonadotropin-releasing hormone (GnRH) gene expression in in vitro models of GnRH neurons. Early growth response-1 (Egr-1) is a transcription factor that mediates the effect of insulin on target genes. In the GN11 cell line--an immortalized GnRH-secreting neuronal cell line--insulin maximally increases Egr-1 mRNA after 30min of treatment and Egr-1 protein and GnRH mRNA after 60min of treatment. Egr-1 small interfering RNA blocks the insulin-induced increase in GnRH promoter activity, measured as luciferase expression. Chromatin immunoprecipitation using Egr-1 antibody precipitates DNA in a proximal region of the GnRH promoter but not DNA in a distal region. Mutagenesis of a putative Egr-1 binding site within the proximal region blocks the insulin-induced increase in GnRH promoter activity. Thus, Egr-1 binds the GnRH promoter at a site between -67 and -76bp from the transcriptional start site to mediate the insulin-induced increase in GnRH gene transcription.
DiVall
Sara A
SA
Division of Endocrinology, Department of Pediatrics, Johns Hopkins University, 600 N. Wolfe Street, Park 211, Baltimore, MD 21287, United States. sdivall1@jhmi.edu <sdivall1@jhmi.edu>
Radovick
Sally
S
Wolfe
Andrew
A
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1 / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors
D051766:Early Growth Response Protein 1; D007328:Insulin; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D007987:Gonadotropin-Releasing Hormone; D020928:Mitogen-Activated Protein Kinases