Characterization and regulation of the rat and human ghrelin promoters.
Characterization and regulation of the rat and human ghrelin promoters.
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DOI：
10.1210/en.2004-1306
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发表时间：
2005-03
期刊：
影响因子：
4.8
通讯作者：
Wei Wei-Wei;Guiyun Wang;Xiang Qi;E. Englander;G. Greeley
中科院分区：
文献类型：
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作者：
Wei Wei-Wei;Guiyun Wang;Xiang Qi;E. Englander;G. Greeley
Ghrelin 是最近发现的一种胃激素和 GH 促分泌素受体的内源性配体。这些研究的目的是阐明生长素释放肽基因调控的分子机制。存在远端和近端转录起始位点。短转录本是近端位点的产物，显示出更广泛的分布。克隆并测序了大鼠和人生长素释放肽基因的两组5'上游片段。在瞬时转染测定中，远端位点上游的大鼠启动子片段在肾 (COS-7) 和胃 (AGS) 细胞中显示出最高活性，而近端位点上游的人启动子片段在 AGS 和垂体 (GH3) 细胞中显示出最高活性。对于人类，核心启动子跨越-667至-468 bp，包括非编码外显子1和内含子1的短5'序列。对于大鼠，核心启动子跨越-581至-469 bp，包含外显子1和内含子1的短5'序列使活性降低67%。大鼠中类引发剂元件的突变使活性降低了 20-50%，而在人类中，所有活性均被消除。上游刺激因子的过度表达增加了 ghrelin 核心启动子的活性。禁食会增加胃部生长素释放肽的表达、胰高血糖素（一种禁食诱导的激素）、大鼠体内生长素释放肽的表达增加以及启动子活性约 25-50%。总之，这些发现表明大鼠和人类生长素释放肽核心启动子之间的结构差异可能部分解释了它们转录调控的差异。尽管如此，上游刺激因子和胰高血糖素对大鼠和人类生长素释放肽启动子的调节具有相似的作用。
Ghrelin is a recently discovered stomach hormone and endogenous ligand for the GH secretagogue receptor. The aim of these studies is to elucidate molecular mechanisms underlying regulation of the ghrelin gene. Distal and proximal transcription initiation sites are present. A short transcript, a product of the proximal site, showed a more widespread distribution. Two sets of 5'-upstream segments of the rat and human ghrelin genes were cloned and sequenced. Rat promoter segments upstream of the distal site showed highest activity in kidney (COS-7) and stomach (AGS) cells, whereas human promoter segments upstream of the proximal site showed highest activity in AGS and pituitary (GH3) cells in transient transfection assays. For the human, the core promoter spanned -667 to -468 bp, including the noncoding exon 1 and a short 5' sequence of intron 1. For the rat, the core promoter spanned -581 to -469 bp, and inclusion of exon 1 and a short 5'-sequence of intron 1 reduced activity by 67%. Mutation of initiator-like elements in the rat lowered activity by 20-50%, whereas in the human, all activity was abolished. Overexpression of upstream stimulatory factors increased ghrelin core promoter activity. Fasting increases stomach ghrelin expression, glucagon-a fasting-induced hormone, increased ghrelin expression in vivo in rats, and promoter activity by approximately 25-50%. Together, these findings indicate that structural differences between the rat and human ghrelin core promoters may account in part for the differences in their transcriptional regulation. Nonetheless, upstream stimulatory factor and glucagon exert similar effects on regulation of rat and human ghrelin promoters.