Division of Theoretical Nursing and Genetics, Yamagata University School of Medicine, 2-2-2 Iida-nishi, Yamagata 990-9585, Japan.
Biochem Biophys Res Commun. 2011 Nov 4;414(4):767-72. doi: 10.1016/j.bbrc.2011.09.155. Epub 2011 Oct 7.
Vimentin exhibits a complex pattern of tissue-specific and developmentally regulated expression, but the mechanisms underlying the complex transcriptional regulation remain poorly understood. Here we examined whether vimentin expression can be regulated by CpG methylation of the vimentin promoter. Two subclones of the rat C6 glioma cells were established with (C6vim+) and without (C6vim-) vimentin. Bisulfite genomic sequencing revealed that the vicinity of the transcription start site within the vimentin promoter is highly methylated in C6vim- cells but not in C6vim+ cells. Treatment of C6vim- cells with a demethylating agent, 5-aza-2'-deoxycytidine, restored vimentin expression, indicating that hypermethylation of the promoter region correlates with transcriptional silencing of the vimentin gene. Electrophoretic mobility shift assay (EMSA) and transient transfection experiments demonstrated that YY1 is a key transcriptional activator regulating vimentin expression and that CpG methylation is sufficient to prevent the binding of YY1 to the vimentin promoter. These data suggest that the inability of YY1 to access the hypermethylated promoter may be one of the mechanisms that mediate vimentin downregulation.
波形蛋白表现出复杂的组织特异性和发育调控表达模式，但复杂的转录调控机制仍知之甚少。在这里，我们研究了波形蛋白表达是否可以通过波形蛋白启动子的 CpG 甲基化来调节。建立了两个具有（C6vim+）和没有（C6vim-）波形蛋白的大鼠 C6 神经胶质瘤细胞亚克隆。亚硫酸氢盐基因组测序显示，在 C6vim-细胞中，转录起始位点附近的波形蛋白启动子高度甲基化，但在 C6vim+细胞中则不然。用去甲基化剂 5-氮杂-2'-脱氧胞苷处理 C6vim-细胞可恢复波形蛋白表达，表明启动子区域的高甲基化与波形蛋白基因的转录沉默相关。电泳迁移率变动分析（EMSA）和瞬时转染实验表明，YY1 是调节波形蛋白表达的关键转录激活因子，CpG 甲基化足以阻止 YY1 与波形蛋白启动子结合。这些数据表明，YY1 无法访问超甲基化的启动子可能是介导波形蛋白下调的机制之一。
