Organization and Evolution of the Human Growth Hormone Receptor Gene 5′-Flanking Region*

Abstract

Previous studies have identified eight variant human GH receptor (hGHR) messenger RNA (mRNAs; V1-V8), that differ in their 5'-untranslated regions (5'UTRs) but splice into the same site just upstream of the translation start site in exon 2; thus, they encode the same protein. Here we report a novel variant, V9, and describe the mapping of all nine 5'UTR sequences within 40 kb upstream of exon 2. A cluster of three sequences, V2-V9-V3 (termed module A), lies furthest 5', and approximately 16 kb downstream is a second cluster of four exons, V7-V1-V4-V8 (module B). V6 is midway between modules A and B. Module B is about 18 kb upstream of V5, which lies adjacent to exon 2. hGHR expression is under developmental- and tissue-specific regulation, and expression of the variant mRNAs is related to their position within the 5'-flanking region; whereas module A (V2,V9,V3) and V5 variants are widely expressed, module B (V7,V1,V4,V8) and V6 variant mRNAs are detectable only in postnatal liver. Transcriptional start sites for V1 and V9 (representing the two different modules) were identified, showing that postnatal liver-specific expression of V1 is driven from two TATA boxes, whereas the ubiquitous V9 transcript has a single start site and a TATA-less promoter. V9 promoter activity was shown by in vivo and in vitro transfection assays, and an NF-Y binding site was demonstrated by electromobility shift assay. Thus, the regulatory regions of the hGHR gene are complex, and the clustering of seven 5'UTR exons within two modules with distinctly different mRNA expression patterns is the most striking feature.

Mouse Prostasin Gene Structure, Promoter Analysis, and Restricted Expression in Lung and Kidney

“…Variations in 5Ј UTR may regulate gene expression in specific cell types by altering translational efficiency and mRNA stability. An archetype for studying this phenomenon is the human growth hormone receptor gene, for which at least nine 5Ј UTR variants with specific expression patterns have been described (49). Whether these splice variants of prostasin are involved in translational regulation and are cell-specific remains to be determined.…”

Characterization of the growth hormone receptor in human dermal fibroblasts and liver during development

“…The hGHR, a single-chain (620 amino acid) polypeptide member of the hGH/human prolactin/cytokine receptor superfamily, dimerizes in the presence of one molecule of hGH, activating specific intracellular signal transduction pathways and leading to gene regulation (14,21,35). The hGHR is encoded by a single gene spanning Ͼ150 kb on chromosome 5p13.1-12 (5,17,19,41). The coding region is defined by exons 2-10, with exon 2 contributing the translation start site and signal sequence.…”

“…Plasma levels of immunoreactive hGH are markedly elevated in the fetus relative to the normal adult, up to 150 ng/ml at midgestation (34). We (19,54,66,67) and others (26,62) have identified hGH receptors (hGHR) at the mRNA and peptide level in fetal tissues as early as the first trimester. hGH stimulated proliferation and IGF production in cultured fetal hepatocytes but had a variable effect on insulin and IGF production by islets and no effect on fetal myoblasts, fibroblasts, or cartilage explants (13,24,46,56,57).…”

Gαs Transcripts Are Biallelically Expressed in the Human Kidney Cortex: Implications for Pseudohypoparathyroidism Type 1b

“…DNA and RNA were extracted as described previously (23). A transcribed, silent T to C polymorphism in exon 5, creating a FokI site, was used to distinguish two copies of the gene (24).…”