Complex alternative splicing of the GH-V gene in the human testis.
The human growth hormone variant (GH-V) gene is expressed during pregnancy in the syncytiotrophoblast and, as shown recently, in the normal human testis. In addition to the classical transcript encoding for the 22 K major form, intron D-retaining processed mRNAs (GH-V2) have also been described in both tissues. In the present study we analyzed testicular GH-V RNA alternative splicing patterns, a major source of GH variability. We observed three types of GH-V-derived mRNAs by reverse transcription-polymerase chain reaction amplification of GH/placental lactogen mRNA, subsequent cloning into appropriate vectors, vector amplification, restriction-endonuclease map-analysis and double-strand sequencing of GH-V clones. Apart from the conventional splice product encoding classical hGH-V (22K, 191 amino acids (aa)) and intron D-retaining mRNA GH-V2 (230aa), we detected an additional GH-V mRNA variant, GH-Vdelta4, utilizing a competitive splice-donor site 4 bp 5'of the conventional exon 4/intron D splice-donor site, but retaining the genuine intron D/exon 5 splice-acceptor site. This mRNA encodes a putative 25 K protein of 219 amino acids in length, having the first 124 amino acids and, thus, two and a half structural alpha-helices in common with hGH-V.hGH-Vdelta4 has lost the N-glycosylation site at Asn 140 of hGH-V, but acquires a novel site at position 148 as well as a cystein-rich domain in the 65 carboxyl-terminal amino acids, potentially involved in multiple disulfide-bridge formation. Tissue specificity and possible functions for testicular physiology remain to be investigated.
Untergasser
G
G
Institute for Biomedical Aging Research of the Austrian Academy of Sciences, Innsbruck.
Hermann
M
M
Rumpold
H
H
Berger
P
P
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D005091:Exons; D014644:Genetic Variation; D019382:Human Growth Hormone / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012333:RNA, Messenger / Q000032:analysis / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000737:chemistry*
D012333:RNA, Messenger; D019382:Human Growth Hormone