Histone Modifiers, YY1 and p300, Regulate the Expression of Cartilage-specific Gene, Chondromodulin-I, in Mesenchymal Stem Cells
Histone Modifiers, YY1 and p300, Regulate the Expression of Cartilage-specific Gene, Chondromodulin-I, in Mesenchymal Stem Cells
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DOI：
10.1074/jbc.m110.116319
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发表时间：
2010-09-24
影响因子：
4.8
通讯作者：
Toguchida, Junya
中科院分区：
文献类型：
--
作者：
Aoyama, Tomoki;Okamoto, Takeshi;Toguchida, Junya
阐明组织特异性基因表达的调控机制是理解分化过程的关键。软骨调节蛋白-I 基因 (ChM-I) 是一种软骨特异性基因，其表达受转录因子 Sp3 调节。正如我们之前报道的，Sp3 与核心启动子区域的结合受到 Sp3 结合基序的甲基化状态的调节。在本研究中，我们研究了间充质干细胞（MSC）和软骨以外的正常间充质组织中 ChM-I 表达下调的分子机制。骨和周围神经组织细胞的核心启动子区高度甲基化，而包括间充质干细胞在内的其他组织细胞的甲基化状态与软骨细胞的甲基化状态没有差异，表明存在除DNA甲基化之外的抑制机制。我们发现转录阻遏蛋白 YY1 通过招募组蛋白脱乙酰酶从而诱导相关组蛋白脱乙酰化来负向调节 ChM-I 的表达。至于正调节因子，我们发现转录辅激活因子p300与Sp3结合到核心启动子区域，诱导组蛋白乙酰化。 YY1 的抑制与 p300 和 Sp3 的强制表达相结合可恢复具有低甲基化启动子区域的细胞中 ChM-I 的表达，但不能恢复具有高甲基化的细胞中的 ChM-I 表达。这些结果表明组织特异性基因的表达分两个步骤进行调节；通过转录抑制复合物进行可逆下调，并通过 DNA 甲基化进行严格下调。
Elucidating the regulatory mechanism for tissue-specific gene expression is key to understanding the differentiation process. The chondromodulin-I gene (ChM-I) is a cartilage-specific gene, the expression of which is regulated by the transcription factor, Sp3. The binding of Sp3 to the core-promoter region is regulated by the methylation status of the Sp3-binding motif as we reported previously. In this study, we have investigated the molecular mechanisms of the down-regulation of ChM-I expression in mesenchymal stem cells (MSCs) and normal mesenchymal tissues other than cartilage. The core-promoter region of cells in bone and peripheral nerve tissues was hypermethylated, whereas the methylation status in cells of other tissues including MSCs did not differ from that in cells of cartilage, suggesting the presence of inhibitory mechanisms other than DNA methylation. We found that a transcriptional repressor, YY1, negatively regulated the expression of ChM-I by recruiting histone deacetylase and thus inducing the deacetylation of associated histones. As for a positive regulator, we found that a transcriptional co-activator, p300, bound to the core-promoter region with Sp3, inducing the acetylation of histone. Inhibition of YY1 in combination with forced expression of p300 and Sp3 restored the expression of ChM-I in cells with a hypomethylated promoter region, but not in cells with hypermethylation. These results suggested that the expression of tissue-specific genes is regulated in two steps; reversible down-regulation by transcriptional repressor complex and tight down-regulation via DNA methylation.