Molecular structure of the human gonadotropin-releasing hormone receptor gene

Abstract

GnRH receptors belong to the family of G protein-coupled receptor proteins and have been localized to the anterior pituitary, brain and reproductive organs as well as many steroid-dependent tumor tissues. Recently, cDNAs for the GnRH receptors of several species including the human have been cloned. To determine the structure of the gene encoding the human GnRH receptor, we isolated the receptor gene clones from the human genomic libraries. Comparison of the genomic and cDNA sequences revealed that the human GnRH receptor gene is composed of three exons and two introns and spans over 20 kb in size. Exon 1 encodes the 5 0 untranslated sequence and nucleotide þ 1 to þ 522 in the open reading frame, exon 2 encodes nucleotide þ 523 to þ 742 and exon 3 encodes nucleotide þ 743 to þ 987 in the open reading frame as well as the 3 0 untranslated sequence. Southern blot analysis of genomic DNA and localization of the GnRH receptor gene to a single site on human chromosome 4 (4q13) indicate the presence of a single copy of the gene in the human genome. Several regulatory sequences for various hormones and other regulatory factors were identified, including PEA-3, AP-1, AP-2, and Pit-1 sites. In addition, glucocorticoid/progesterone response element, thyroid hormone response element, and cAMP response element sequences were identified. Reverse transcriptase-primer extension and 5 0 RACE analysis of the human pituitary RNA demonstrated the presence of multiple transcriptional start sites upstream of the translational start site. Analysis of the 5 0 flanking region of the gene also revealed the presence of multiple TATA and CAAT sequences. The finding of multiple transcriptional start sites raises the possibility of tissue-specific regulation and the existence of variable size transcripts. Chimeras containing 1.26 kb (¹534 to 728) of the 5 0 flanking region of the receptor gene and the luciferase (Luc) gene expressed a significant luciferase activity when transfected into a human endometrial tumor cell line (HEC-1A) and a breast tumor cell line (MCF-7) but not in a mouse pituitary gonadotrope cell line (aT3-1), suggesting the existence of multiple promoter elements in the gene. These findings indicate a multiplicity of regulation of expression of the GnRH receptor and provide the substrate for detailed investigation in the reproductive system.

Tissue-specific pattern of variant transcripts of the human gonadotropin-releasing hormone receptor gene

“…cDNAs encoding a functional pituitary GnRHR have been obtained in mice (1,2), rats (3), humans (4,5) and sheep (6), and predicted amino acid sequences were highly conserved among the species. The coding region is distributed among three exons separated by two large introns (7,8). The human gene has been mapped to chromosome 4 (9), between the markers D4S312 and D4S409 (10).…”

“…Primers were chosen to bridge each of the introns described (7,8): F2/R3 spans from exon 1 to exon 2 and F3/R2 spans from exon 2 to exon 3. Manufacturers' recommendations were followed, with adapted modifications.…”

Expression of mRNA for human type-I LHRH receptor transcript forms in human benign prostatic hyperplasia

“…Three LHRH receptors or receptor-like genes were demonstrated earlier (2)(3)(4)(5)(6). The well-established type-I LHRH receptor (LHRH-R-I) gene has been identified as a single copy on chromosome 4q21.2 (4,5) and is composed of three exons separated by two introns (6). A vast literature indicates that the LHRH-I is expressed not only in the hypothalamus but also in peripherial tissues, both normal and tumoral (7)(8)(9)(10)(11)(12)(13)(14)(15)(16).…”

“…The human LHRH-I gene is composed of four exons separated by three introns and is present as a single gene copy on chromosome 8p11.2-p21 (2,3). Three LHRH receptors or receptor-like genes were demonstrated earlier (2)(3)(4)(5)(6). The well-established type-I LHRH receptor (LHRH-R-I) gene has been identified as a single copy on chromosome 4q21.2 (4,5) and is composed of three exons separated by two introns (6).…”

Multiple regulatory elements in the human GnRH receptor gene

“…In this issue, Kakar provides information on the structural organisation of the human GnRH receptor gene and identifies a diversity of putative regulatory elements (12).…”