Glucose regulation of insulin gene transcription and pre-mRNA processing in human islets
Glucose regulation of insulin gene transcription and pre-mRNA processing in human islets
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DOI：
10.2337/db06-1440
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发表时间：
2007-03-01
期刊：
影响因子：
7.7
通讯作者：
Mirmira, Raghavendra G.
中科院分区：
文献类型：
--
作者：
Evans-Molina, Carmella;Garmey, James C.;Mirmira, Raghavendra G.
葡萄糖是胰岛释放胰岛素颗粒的主要调节剂。在啮齿动物胰岛中，葡萄糖在胰岛素基因转录的急性调节中的作用仍然不清楚，主要是因为胰岛素mRNA的丰度和长半衰期使通过测量稳态mRNA水平的传统方法进行的转录分析变得混乱。为了研究人胰岛中葡萄糖调节的胰岛素基因转录的性质，我们首先定量了加入放线菌素D（以终止转录）后胰岛素mRNA和前mRNA的丰度和半衰期。我们的研究结果表明，内含子1和内含子2的前mRNA的丰度分别比成熟mRNA低150倍和2,000倍。含有5'内含子2的前mRNA显示仅类似于60分钟的半衰期，而所有其他转录物显示更长的寿命。在葡萄糖升高的反应中，前mRNA种类在60分钟内增加，而成熟mRNA的增加直到48小时才发生，这表明成熟mRNA种类的测量不能准确反映胰岛素基因对葡萄糖的急性转录反应。前mRNA种类的急剧增加之前，组蛋白H4乙酰化增加了6倍，胰岛素启动子RNA聚合酶II的招募增加了两倍。总之，我们的数据表明，前体mRNA的种类可能是一个更可靠的反映急性变化的人胰岛素基因转录率和葡萄糖急剧增强胰岛素转录的机制，提高染色质的可及性，并导致招聘的基础转录机器。
Glucose is the primary regulator of insulin granule release from pancreatic islets. In rodent islets, the role of glucose in the acute regulation of insulin gene transcription has remained unclear, primarily because the abundance and long half-life of insulin mRNA confounds analysis of transcription by traditional methods that measure steady-state rnRNA levels. To investigate the nature of glucose-regulated insulin gene transcription in human islets, we first quantitated the abundance and half-lives of insulin mRNA and pre-mRNAs after addition of actinomycin D (to stop transcription). Our results indicated that intron 1 and intron 2-containing pre-mRNAs were similar to 150- and 2,000-fold less abundant, respectively, than mature mRNA. 5' intron 2-containing pre-mRNAs displayed half-lives of only similar to 60 min, whereas all other transcripts displayed more extended lifetimes. In response to elevated glucose, pre-mRNA species increased within 60 min, whereas increases in mature mRNA did not occur until 48 h, suggesting that measurement of mature mRNA species does not accurately reflect the acute transcriptional response of the insulin gene to glucose. The acute increase in pre-mRNA species was preceded by a sixfold increase in histone H4 acetylation and a twofold increase in RNA polymerase II recruitment at the insulin promoter. Taken together, our data suggest that pre-mRNA species may be a more reliable reflection of acute changes to human insulin gene transcriptional rates and that glucose acutely enhances insulin transcription by a mechanism that enhances chromatin accessibility and leads to recruitment of basal transcriptional machinery.