Regulation of gonadotropin-releasing hormone-1 gene transcription by members of the purine-rich element-binding protein family

Zhao S, Kelm RJ Jr, Fernald RD. Regulation of gonadotropin-releasing hormone-1 gene transcription by members of the purinerich element-binding protein family. Am J Physiol Endocrinol Metab 298: E524-E533, 2010. First published December 8, 2009; doi:10.1152/ajpendo.00597.2009.-Gonadotropin-releasing hormone-1 (GnRH1) controls reproduction by stimulating the release of gonadotropins from the pituitary. To characterize regulatory factors governing GnRH1 gene expression, we employed biochemical and bioinformatics techniques to identify novel GnRH1 promoter-binding proteins from the brain of the cichlid fish, Astatotilapia burtoni (A. burtoni). Using an in vitro DNA-binding assay followed by mass spectrometric peptide mapping, we identified two members of the purine-rich element-binding (Pur) protein family, Pur alpha and Pur beta, as candidates for GnRH1 promoter binding and regulation. We found that transcripts for both Pur alpha and Pur beta colocalize in GnRH1-expressing neurons in the preoptic area of the hypothalamus in A. burtoni brain. Furthermore, we confirmed in vivo binding of endogenous Pur alpha and Pur beta to the upstream region of the GnRH1 gene in A. burtoni brain and mouse neuronal GT1-7 cells. Consistent with the relative promoter occupancy exhibited by endogenous Pur proteins, overexpression of Pur beta, but not Pur alpha, significantly downregulated GnRH1 mRNA levels in transiently transfected GT1-7 cells, suggesting that Pur beta acts as a repressor of GnRH1 gene transcription.