Estrogen regulates KiSS1 gene expression through estrogen receptor α and SP protein complexes

Kisspeptins are natural ligands of G protein-coupled receptor-54. Activation of KiSS1/G protein-coupled receptor-54 signaling pathways results in potent activation of the hypothalamus-pituitary-gonadal axis and initiates puberty. Recent data have shown that in female mice, KiSS1 is positively regulated by estradiol (E₂) in the anteroventral periventricular nucleus, an important reproductive neuroendocrine brain region, but negatively regulated in the arcuate nucleus. However, little is known about the molecular mechanisms governing E₂-modulated KiSS1 expression. Here, we demonstrate that the expression level of the KiSS1 gene was up-regulated with the administration of E₂ in estrogen receptor α (ERα)-positive hypothalamic GT1-7 cells. Using transient transfection of human KiSS1 gene promoter coupled to a luciferase reporter, E₂ increases promoter activity in the presence of ERα. Deletion analysis of KiSS1 promoter indicates that the E₂-regulated increase in promoter activity depends on the Sp1 sites of the proximal promoter region. Using both EMSAs and chromatin immunoprecipitation analysis, we determined that both Sp1 and Sp3 proteins constitutively associate with the four putative Sp1 sites in vitro, whereas the association of ERα with the KiSS1 promoter is dependent on E₂ exposure. Sp1 and ERα form a complex in vivo to mediate the E₂-induced activation of KiSS1 promoter. Interestingly, Sp1 transactivates KiSS1 promoter activity, whereas Sp3 functions as a transcriptional repressor. Together, these results demonstrate that E ₂-dependent transcriptional activation of KiSS1 gene is mediated by ERα through the interaction of Sp1/Sp3 proteins with the GC-rich motifs of KiSS1 promoter, providing a molecular mechanism of how steroid hormone feedback regulates KiSS1 expression.