Transcriptional regulation of the mouse IL-7 receptor a promoter by glucocorticoid receptor
Transcriptional regulation of the mouse IL-7 receptor a promoter by glucocorticoid receptor
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DOI：
10.4049/jimmunol.174.12.7800
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发表时间：
2005-06-15
影响因子：
4.4
通讯作者：
Ikuta, K
中科院分区：
文献类型：
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作者：
Lee, HC;Shibata, H;Ikuta, K
IL-7Rα链(IL-7Rα)的表达在淋巴细胞发育和成熟过程中受到严格调控。糖皮质激素(GC)对淋巴细胞的生长和功能有多种影响。虽然已有研究报道GC可诱导人T细胞IL-7ra基因转录，但其分子机制尚不清楚。在这项研究中，我们发现GC上调了小鼠T细胞中IL-7Rα的mRNA和蛋白水平。这种作用不需要蛋白质合成从头开始，因为蛋白质合成抑制剂不会阻止这一过程。小鼠IL-7Rα启动子与人和大鼠有惊人的同源性，包含Ikaros、PU.1和RUNX1转录因子的共同基序。此外，在启动子上游还发现了一个约270kb的保守非编码序列，命名为CNS-1。在CNS-1区存在一个GC受体(GR)基序。重要的是，我们通过报告实验证明了IL-7Rα启动子在T细胞中具有特异的转录活性。这一活动高度依赖于PU1基序。此外，GC处理通过CNS-1区域的GR基序增强转录活性。我们还通过EMSA证明了GR与GR基序结合。此外，通过染色质免疫沉淀实验，我们发现GR在GC刺激后迅速募集到内源性CNS-1染色质中。这些结果表明，GR在GC刺激后与CNS-1区的GR基序结合，进而激活IL-7Ra启动子的转录。因此，本研究确定IL-7Ra CNS-1区域为GC反应元件。
Expression of the IL-7R alpha-chain (IL-7R alpha) is strictly regulated during the development and maturation of lymphocytes. Glucocorticoids (GC) have pleiotypic effects on the growth and function of lymphocytes. Although GC have been reported to induce the transcription of IL-7Ra gene in human T cells, its molecular mechanism is largely unknown. In this study, we show that GC up-regulate the levels of IL-7R alpha mRNA and protein in mouse T cells. This effect does not require protein synthesis de novo, because protein synthesis inhibitors do not block the process. Mouse IL-7R alpha promoter has striking homology with human and rat, containing consensus motifs of Ikaros, PU.1, and Runx1 transcription factors. In addition, a conserved noncoding sequence (CNS) of similar to 270 bp was found 3.6-kb upstream of the promoter, which was designated as CNS-1. A GC receptor (GR) motif is present in the CNS-1 region. Importantly, we show by reporter assay that the IL-7R alpha promoter has specific transcription activity in T cells. This activity highly depends on the PU.1 motif. Furthermore, GC treatment augments the transcriptional activity through the GR motif in the CNS-1 region. We also demonstrate that GR binds to the GR motif by EMSA. In addition, by chromatin immunoprecipitation assay, we show that GR is rapidly recruited to endogenous CNS-1 chromatin after GC stimulation. These results demonstrate that GR binds to the GR motif in the CNS-1 region after GC stimulation and then activates the transcription of the IL-7Ra promoter. Thus, this study identifies the IL-7Ra CNS-1 region as a GC-responsive element.