MECHANISMS OF GNRH RECEPTOR GENE EXPRESSION

点击翻译按钮获取中文摘要

The relationship between GnRH release, GnRH receptor numbers, and the synthesis and secretion of LH and FSH in gonadotropes is well established. While relatively little is known about GnRH receptor gene expression in gonadotropes, the promoter of the common alpha-glycoprotein subunit gene appears to be activated by cooperative binding of multiple trans-acting factors including the orphan-nuclear receptor, steroidogenic factor-1(SF- 1). Disruption of the SF-1 gene in transgenic mice resulted in, among other things, decreased expression of the genes encoding the common alpha and unique beta subunits of LH and FSH, and the GnRH receptor. Recently, we have shown that 500 basepairs of proximal promoter from the GnRH receptor gene are sufficient to drive luciferase expression in transient transfections of the gonadotrope-derived alphaT3 cell line. This same vector was also activated by overexpression of SF-1, minus its ligand binding domain, in non-gonadotrope cells. Furthermore, transient transfections of alphaT3 cells with reporter constructs containing serial 5' deletions from -500 to -400 revealed a stepwise decrease in promoter activity indicative of binding by several trans-acting factors. In light of these data, we hypothesize that SF-1 binding is necessary, but not sufficient for gonadotrope expression of the GnRH receptor gene. Therefore, the aims of this research proposal are: 1) to determine if SF-1 is necessary for full basal activity of the GnRH receptor promoter; and 2) to identify the other components necessary for full basal activity in gonadotropes. These studies will contribute to our understanding of gonadotrope gene expression and the interactions of multiple cis-acting elements to confer cell-specific gene expression.