Institute of Immunology, CRP-Santé/Laboratoire National de Santé, 20A rue Auguste Lumière, Luxembourg, Grand Duchy of Luxembourg.
Hum Genet. 2011 May;129(5):533-43. doi: 10.1007/s00439-011-0949-1. Epub 2011 Jan 15.
Glucocorticoid receptor levels are thought to be controlled by multiple alternative first exons. Seven of these exons are located in an upstream CpG island. In this study, we investigated the promoter activity of the intronic regions between these exons, and their susceptibility to CpG methylation and sequence variability. The seven promoters were cloned into luciferase reporter genes, and their activity measured in ten cell lines. CpG islands of 221 donors were genotyped and the effects of these SNPs were investigated in a reporter gene assay. We showed that each of the first exons was independently controlled by a unique promoter located directly upstream. Promoter activities were cell type-specific, and varied considerably between cell types. Irrespective of the cell type, in vitro methylation effectively silenced all reporter constructs. Eleven SNPs were observed within the CpG island of 221 donors, and a new promoter-specific haplotype was revealed. Four of the minor alleles reduced the reporter gene activity, with cell type specific effects. This complexity within the CpG island helps to explain the variable, tissue-specific transcriptional control of the GR, and provides insight into the mechanisms underlying tissue specific deregulation of GR levels.
糖皮质激素受体水平被认为受多个替代的第一外显子控制。其中七个外显子位于上游 CpG 岛。在本研究中，我们研究了这些外显子之间内含子区域的启动子活性及其对 CpG 甲基化和序列变异的易感性。这七个启动子被克隆到荧光素酶报告基因中，并在十种细胞系中测量其活性。对 221 名供体的 CpG 岛进行了基因分型，并在报告基因测定中研究了这些 SNP 的影响。我们表明，每个第一外显子都由位于其上游的独特启动子独立控制。启动子活性具有细胞类型特异性，并且在细胞类型之间差异很大。无论细胞类型如何，体外甲基化均可有效沉默所有报告基因构建体。在 221 名供体的 CpG 岛内观察到 11 个 SNP，并揭示了一个新的启动子特异性单倍型。四个次要等位基因降低了报告基因的活性，且具有细胞类型特异性效应。CpG 岛内的这种复杂性有助于解释 GR 的可变、组织特异性转录控制，并深入了解 GR 水平组织特异性失调的机制。
