THE HUMAN GONADOTROPIN-RELEASING-HORMONE RECEPTOR GENE - COMPLETE STRUCTURE INCLUDING MULTIPLE PROMOTERS, TRANSCRIPTION INITIATION SITES, AND POLYADENYLATION SIGNALS

The interaction of gonadotropin-releasing hormone and its receptor is a critical event in the endocrine regulation of reproduction. We have recently cloned the gene encoding for the human gonadotropin-releasing hormone receptor (hGnRHR). Partial sequence analysis revealed a structural organization consisting of three exons and two introns. Exon II contains only 219 bp and the remainder of the approximately 5 kb transcript is distributed between exons I and III. The complete coding region for the hGnRHR represented only 987 bp leaving an extensive 5' and 3' non-translated region and potentially additional exons unaccounted for. This report provides the complete sequence of exon I and III and demonstrates that further exons are unlikely to be contained within this gene. Sequencing of the 5' end of the gene revealed the presence of five consensus TATA sequences distributed within a 700 nucleotide region. Primer extension analysis detected multiple transcription initiation sites associated with this cluster of TATA sequences. Transcription of this region up to the most 5' initiation site was demonstrated by the reverse transcription-polymerase chain reaction (RT-PCR) method. The 5' non-translated region stretches between 703 and 1393 bp, depending on which initiation site is used. Several consensus cis-acting regulatory sequences were identified within the 5' end. These include, among others, sites for PEA-3, AP-1, and Pit-1. In addition, cAMP response element (CRE)-like and glucocorticoid/progesterone response element (GRE/PRE)-like sequences were found. The 3' end of the gene was also sequenced and five classical polyadenylation signals were found scattered over a region of 800 nucleotides. RT-PCR conducted on the 3' non-translated region confirmed transcription up to the fifth polyadenlyation signal. Factoring in the location of the most 5' initiation site and the most 3' polyadenylation signal, the total transcript covers a region of 5499 bp. The finding of multiple transcription initiation sites and polyadenylation signals raises the possibility of tissue-specific regulation and the existence of variable transcripts for the hGnRHR. The presence of a CRE-like sequence, Pit-1 binding site, and a GRE/PRE-like sequence is consistent with the notion that cAMP, Pit-1, and progesterone are candidates for controlling the expression of this key receptor in reproductive physiology.