Enhancers located within two introns of the vitamin D receptor gene mediate transcriptional autoregulation by 1,25-dihydroxyvitamin D3
Enhancers located within two introns of the vitamin D receptor gene mediate transcriptional autoregulation by 1,25-dihydroxyvitamin D3
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DOI：
10.1210/me.2006-0015
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发表时间：
2006-06-01
影响因子：
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通讯作者：
Pike, J. Wesley
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文献类型：
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作者：
Zella, Lee A.;Kim, Sungtae;Pike, J. Wesley
1，25-(OH)(2)D-3的生物学作用是由维生素D受体(VDR)介导的，VDR是一种与靶基因结合并改变其表达的蛋白质。1，25-(OH)(2)D-3也能诱导VDR基因本身的转录。在本研究中，我们探索了1，25-(OH)(2)D-3诱导VDR基因在骨细胞中表达的能力及其上调的机制。在建立了1，25-(OH)(2)D-3在活体骨骼和成骨细胞中刺激VDR基因表达上调的能力后，我们利用染色质免疫沉淀-DNA微阵列(CHIP-CHIP)分析从转录起始点(TSS)上游的20kb到最终外显子下游的10kb的小鼠VDR基因位点来确定VDR结合部位。在TSS下游发现了3个保守区，分别为20、27和29kb。芯片分析证实VDR与1，25-(OH)(2)D-3结合，并伴随着维甲酸X受体的差异定位、组蛋白乙酰化和RNA聚合酶II的募集。其中一个区域能够赋予下游启动子1，25-(OH)(2)D-3调控，从而允许鉴定和鉴定位于其中的调控元件。重要的是，人类VDR基因中的一个高度保守的区域与在小鼠中发现的类似，也能够介导1，25-(OH)(2)D-3反应。我们的结果表明，1，25-(OH)(2)D-3及其受体对VDR基因的表达具有自我调节作用。这些调控区域的位置和它们与TSS的明显距离与新的发现相一致，这表明远距离增强子正在出现相关性。
The biological actions of 1,25-(OH)(2)D-3 are mediated by the vitamin D receptor (VDR), a protein that binds to target genes and alters their expression. 1,25-(OH)(2)D-3 is also capable of inducing transcription of the VDR gene itself. In the present study, we explored both the capacity of 1,25-(OH)(2)D-3 to induce VDR gene expression in bone cells and the mechanism instrumental to this up-regulation. After establishing the ability of 1,25-(OH)(2)D-3 to stimulate VDR mRNA up-regulation both in bone in vivo and in osteoblastic cells, we screened the mouse VDR gene locus from 20 kb upstream of the gene's transcriptional start site (TSS) to 10 kb downstream of the final exon to identify VDR binding sites using chromatin immunoprecipitation-DNA microarray (ChIP- chip) analysis. Three conserved regions were identified 20, 27, and 29 kb downstream of the TSS. VDR binding to these sites in response to 1,25-(OH)(2)D-3 was confirmed by ChIP analysis and was accompanied by differential localization of retinoid X receptor, histone acetylation, and RNA polymerase II recruitment. One of these regions was able to confer 1,25-( OH)(2)D-3 regulation to downstream promoters, thereby permitting identification and characterization of the regulatory element located within. Importantly, a highly conserved region within the human VDR gene analogous to that discovered in the mouse was also capable of mediating 1,25-(OH)(2)D-3 response. Our results demonstrate that 1,25-(OH)(2)D-3 and its receptor autoregulate the expression of the VDR gene. The location of these regulatory regions and their apparent distances from the TSS are consistent with new findings suggesting the emerging relevance of distant enhancers.