Species differences in GnRH activation of the LHbeta promoter: role of Egr1 and Sp1.
Activation of the luteinizing hormone beta (LHbeta) promoter by gonadotropin-releasing hormone (GnRH) via the transcription factor early growth response protein-1 (Egr1) has been well characterized. To determine the mechanisms affecting Egr1 regulation of LHbeta, we analyzed five different species of LHbeta promoters (equine, mouse, rat, bovine and human). Electrophoretic mobility shift assays (EMSAs) identified multiple transcription factors binding to the Egr regions on the LHbeta promoter. Species-specific differences existed in the binding affinity for Sp1, Sp3, steroidogenic factor-1 (SF-1) and Egr1. Upon mutation of the Egr elements, competition for the binding of all zinc finger proteins was lost, suggesting that the Sp proteins compete for binding to the same site that Egr1 occupies. In addition, the promoters from species that had the highest affinity for Sp1 also had the lowest activation by Egr1 and GnRH. Thus we hypothesize that Sp1 competes for Egr1 binding to the Egr elements on the LHbeta promoter and thus inhibits the ability of GnRH and Egr1 to activate the LHbeta promoter.
Call
Gerald B
GB
Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Blvd, Kansas City, KS 66160-7401, USA.
Wolfe
Michael W
MW
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D017930:Genes, Reporter; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000378:metabolism*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; C515057:NR5A1 protein, human; D016329:Sp1 Transcription Factor; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse; C515060:steroidogenic factor 1, rat; D007987:Gonadotropin-Releasing Hormone