title: Analysis of expression and structure of the rat GH-secretagogue/ghrelin receptor (Ghsr) gene: roles of epigenetic modifications in transcriptional regulation.
abstract: In the current study, to elucidate the molecular basis of cell type-specific expression of the GH-secretagogue/ghrelin receptor type 1A (GHSR1A), we characterized the structure and putative promoter region of the rat Ghsr gene. We identified an alternative 5'-untranslated first exon that contains multiple transcription start sites, and confirmed a 200-bp sequence proximal to this exon to be sufficient for basal promoter activity. A promoter-associated CpG island conserved across different species was found to be hypomethylated in Ghsr1a-expressing cell lines, while being heavily methylated in non-expressing cells. In cells with low or absent Ghsr1a expression, treatment with demethylating agents activated Ghsr1a transcription. Chromatin immunoprecipitation assays demonstrated Ghsr1a-expressing cells to display active histone modifications, whereas repressive modifications were present exclusively in other cell types. These results suggest epigenetic modifications at GHSR to play important roles in determining GHSR1A expression and abundance, and therefore the consequent sensitivity of cells to ghrelin.
authors.affiliation: Diabetes Therapeutics and Research Center, The University of Tokushima, Japan. hinoue@genome.tokushima-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kangawa
authors.forename: Chizuko
authors.initials: C
authors.lastname: Kimura
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Ogata
authors.forename: Kenji
authors.initials: K
authors.lastname: Fujieda
authors.forename: Zhi Rong
authors.initials: ZR
authors.lastname: Qian
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sano
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Itakura
mesh_terms: D024506:5' Flanking Region / Q000235:genetics; D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D002460:Cell Line; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D016678:Genome / Q000235:genetics; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D051379:Mice; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D054440:Receptors, Ghrelin / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: C571124:Ghsr1a protein, rat; D006657:Histones; D006877:Hydroxamic Acids; D012333:RNA, Messenger; D054440:Receptors, Ghrelin; C012589:trichostatin A; D001374:Azacitidine