Ghrelin is a growth hormone-releasing peptide recently discovered in the stomach of rat and human as an endogenous ligand for growth hormone-secretagogue receptor. In the present study, a full-length cDNA for mouse ghrelin has been cloned from the stomach using the oligo-capping and rapid amplification methods, and the organization of its gene and promoter has been analyzed. The mouse ghrelin cDNA was 521 bp long, consisting of 44 bp 5'-noncoding region, 354 bp coding region encoding a pre-proghrelin composed of 117 amino acid residues and 123 bp 3'-noncoding region. The genomic sequence analysis has revealed that the mouse ghrelin gene consists of 5 exons and 4 introns. The first exon was revealed to be only 19 bp long presented at the noncoding region of cDNA. The identical 19 bp sequence was also found as the first exon at the 5'-end of full-length rat ghrelin cDNA obtained from the stomach. A TATA box-like sequence, TATATAA was localized 24 bp upstream of the transcription start site of the mouse ghrelin gene. The sequence of the 5'-promoter region of mouse ghrelin gene including the TATA-like sequence and short exon 1 was highly homologous to that of reported human ghrelin gene. These findings suggest that the structure of the promoter region including the short noncoding first exon and its transcriptional regulation are conserved among the mammalian ghrelin genes.
A novel first exon, E1(4), whose sequence was distinct from those of the three known first exons, E1(1), E1(2), and E1(3), of the rat PRL receptor (PRL-R) gene was identified by cDNA cloning for the 5'-end region of PRL-R mRNA expressed in the rat brain. Sequence analysis revealed the presence of two different length E1(4) cDNAs. The longer cDNA contained the 243-bp E1(4) sequence, and the shorter cDNA lacked the 139-bp sequence at the 5'-end of the longer one. Neither E1(4) cDNA has a second exon sequence, indicating that the E1(4) first exon is extensively spliced to the third exon. E1(4)-containing PRL-R mRNAs were detected only in the brain by RT-PCR and ribonuclease protection assay. The longer E1(4) mRNA was expressed as the major PRL-R mRNA species in the brain and was greatly increased in pregnant (d 18) and lactating (d 5) rats. A genomic clone containing the E1(4) first exon together with its 5'- and 3'-flanking regions was isolated from a rat kidney genomic library. Ribonuclease protection assay revealed that the position corresponding to the 5'-end of the shorter E1(4) cDNA is the major transcription start point for the E1(4) exon. The 5'-flanking region of E1(4) contained a TATA box-like element 23 bp upstream of the major transcription start point. Other putative transcription factor-binding sites, such as CCAAT, Sp1, and glucocorticoid-responsive elements, were observed at further upstream regions. These results suggest that PRL-R gene expression in rat brain is controlled by the promoter for the E1(4) first exon.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.