Induction of mPer1

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• 作者：H.E. Sikes Resuehr ; D. Resuehr ; J. Olcese
• 关键词：Egr-1 ; GnRH ; Gonadotropes ; Period1
• 刊名：Molecular and Cellular Endocrinology
• 出版年：2009
• 出版时间：13 November 2009
• 年：2009
• 卷：311
• 期：1-2
• 页码：120-125
• 全文大小：449 K

文摘

We reported earlier that gonadotropin-releasing hormone (GnRH) activates period1 (mPer1) gene expression in immortalized gonadotropes through protein kinase C and p42/44 mitogen-activated protein kinase pathways. GnRH stimulation also leads to the upregulation of early growth response protein 1 (EGR-1), a critical transcription factor for GnRH-induced luteinizing hormone beta (LHβ) synthesis. The parallels between the GnRH–LHβ and the GnRH–mPer1 pathways led us to explore whether EGR-1 is involved in the regulation of mPer1 expression in gonadotropes. Of particular interest was the presence of an EGR-1 binding site in the proximal promoter of the mPer1 gene. Stimulation of LβT2 gonadotrope cells with a GnRH agonist caused the rapid induction of Egr-1 mRNA, which was rapidly followed by mPer1 expression. Chromatin immunoprecipitation revealed that the mPer1 promoter can bind EGR-1, while site-directed mutagenesis experiments confirmed the involvement of Egr-1 sequences in maintaining basal and allowing GnRH-stimulated mPer1 transcription. By means of RNA interference experiments, it could also be demonstrated that silencing of Egr-1 expression resulted in markedly lower mPer1 transcript levels. This silencing effect of the Egr-1 siRNA could be rescued by transfecting the cells with an EGR-1 overexpression vector. In summary, these results all point to a role for the EGR-1 protein in transactivating both the LHβ as well as the mPer1 gene in pituitary gonadotrope cells.