Egr-1 induction in rat granulosa cells by follicle-stimulating hormone and luteinizing hormone: combinatorial regulation by transcription factors cyclic adenosine 3',5'-monophosphate regulatory element binding protein, serum response factor, sp1, and early growth response factor-1.
Early growth response factor (Egr-1) is an inducible zinc finger transcription factor that binds specific GC-rich enhancer elements and impacts female reproduction. These studies document for the first time that FSH rapidly induces Egr-1 expression in granulosa cells of small growing follicles. This response is transient but is reinitiated in preovulatory follicles exposed to the LH analog, human chorionic gonadotropin. Immunohistochemical analysis also showed gonadotropin induced Egr-1 in theca cells. The Egr-1 gene regulatory region responsive to gonadotropin signaling was localized within -164 bp of the transcription initiation site. Binding of Sp1/Sp3 to a proximal GC-box at -64/-46 bp was enhanced by FSH in immature granulosa cells but reduced after human chorionic gonadotropin stimulation of preovulatory follicles despite constant protein expression. This dynamic regulation of Sp1 binding was dependent on gonadotropin-regulated mechanisms that modulate Sp1/3-DNA binding activity. Serum response factor was active in granulosa cells and bound a consensus CArG-box/serum response element site, whereas two putative cAMP response elements within the -164-bp region bound cAMP regulatory element (CRE) binding protein (CREB) and a second cAMP-inducible protein immunologically related to CREB. Transient transfection analyses using Egr-1 promoter-luciferase constructs and site-specific mutations show that the serum response element, GC-box, and CRE-131 are involved in gonadotropin regulation of Egr-1 expression in granulosa cells. Specific kinase inhibitors of Erk or protein kinase A antagonized this induction while exogenously expressed Egr-1 enhanced reporter expression. These observations indicate that the Egr-1 gene is a target of both FSH and LH action that may mediate molecular programs of proliferation and/or differentiation during follicle growth, ovulation, and luteinization.
Russell
Darryl L
DL
Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
Doyle
Kari M H
KM
Gonzales-Robayna
Ignacio
I
Pipaon
Carlos
C
Richards
Joanne S
JS
D000818:Animals; D001665:Binding Sites; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology*; D007016:Hypophysectomy; D017874:Immediate-Early Proteins; D007986:Luteinizing Hormone / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008817:Mice, Mutant Strains; D010053:Ovary / Q000187:drug effects / Q000502:physiology; D011401:Promoter Regions, Genetic; D051381:Rats; D020218:Response Elements; D026362:Serum Response Factor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051705:Sp3 Transcription Factor; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D026362:Serum Response Factor; D016329:Sp1 Transcription Factor; C497122:Sp3 protein, mouse; C497123:Sp3 protein, rat; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate