Involvement of NF‐κB subunit p65 and retinoic acid receptors, RARα and RXRα, in transcriptional regulation of the human GnRH II gene

Abstract

In humans, the genes for gonadotropin-releasing hormones (GnRH I and GnRH II) have the same modular structure, harboring three introns and four exons. The exons encode a precursor polypeptide consisting of a signaling peptide, the GnRH decapeptide, and the GnRH-associated peptide (GAP) with unknown function [1]. The promoter region of the human (h)GnRH II gene is located at the 5¢ flanking region, the untranslated exon 1, intron 1, and exon 2. The locations of exon 1, intron 1 and exon 2 are )793 ⁄ )750 (relative to the +1 translation start codon ATG), )749 ⁄ )8 and )7 to +154, respectively.Despite Gonadotropin-releasing hormone (GnRH) I and II are hypothalamic decapeptides with pivotal roles in the development of reproductive competence and regulation of reproductive events. In this study, transcriptional regulation of the human GnRH II gene was investigated. By scanning mutation analysis coupled with transient promoter assays, the motif at )641 ⁄ )636 (CATGCC, designated GII-Sil) was identified as a repressor element. Mutation of this motif led to full restoration of promoter activity in TE671 medulloblastoma and JEG-3 placenta choriocarcinoma cells. Supershift and chromatin immunoprecipitation assays showed in vitro and in vivo binding of NF-jB subunit p65 and the retinoic acid receptors, RARa and RXRa, to the promoter sequences. Over-expression of these protein factors indicated that p65 is a potent repressor, and the RARa ⁄ RXRa heterodimer is involved in the differential regulation of the GnRH II gene in neuronal and placental cells. This was confirmed by quantitative real-time PCR. Treatment of cells with the RARa ⁄ RXRa ligands, all-trans retinoic acid and 9-cis-retinoic acid, reduced and increased GnRH II gene expression in TE671 and JEG-3 cells, respectively. Taken together, these data demonstrate the differential roles of NF-jB p65 and RARa ⁄ RXRa, interacting with the same sequence in the promoter of the human GnRH II gene to influence gene expression in a cell-specific manner.

An essential set of basic DNA response elements is required for receptor-dependent transcription of the lecithin:retinol acyltransferase (Lrat) gene

“…The presence of RAREs of the DR2 and DR5 types in the promoter region of retinoid-responsive genes are often a signature for those genes that respond directly, and often very rapidly, to RA or to other retinoid receptor agonists [20, 29]. However, RA -activated RAR receptors may also interact with other nuclear receptors such as AP1 [30–33], NFκB [34, 35], SP1 [36–40], and Nrf2 [41], and these may also regulate the expression of genes containing DNA sequences for these proteins. Balmer and Blomhoff [19] reported that whereas about 530 genes are known to be regulated by RA, only a few dozen of have definitively been shown to be directly regulated by RA.…”

Bexarotene via CBP/p300 Induces Suppression of NF-κB–Dependent Cell Growth and Invasion in Thyroid Cancer

“…Furthermore, competition for DNA NF-kB response elements between NF-kB and other transcription factors may occur. This was shown for the same sequence in the promoter of the human GnRH II gene for p65 and RARa/RXRa (47). However in FTC cells, neither could we detect RXR in the p65 transcriptional complex by ChIP nor RXR/p65 interaction by coimmunoprecipitation.…”

Single-Cell Gene Profiling Reveals Social Status-Dependent Modulation of Nuclear Hormone Receptors in GnRH Neurons in a Male Cichlid Fish

“…Therefore, xenobiotic chemicals could affect GnRH neural functions through xenobiotic receptors. However, transcriptional regulation of GnRH genes via xenobiotic nuclear receptors has only been demonstrated in vitro in neuronal culture cells [30][31][32], but not in vivo in the brain.…”