Histone tails regulate DNA methylation by allosterically activating de novo methyltransferase
Histone tails regulate DNA methylation by allosterically activating de novo methyltransferase
复制标题
组蛋白尾部通过变构激活从头甲基转移酶来调节 DNA 甲基化
DOI：
10.1038/cr.2011.92
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发表时间：
2011-08-01
期刊：
影响因子：
44.1
通讯作者：
Xu, Guo-Liang
中科院分区：
文献类型：
--
作者：
Li, Bin-Zhong;Huang, Zheng;Xu, Guo-Liang
基因组DNA的胞嘧啶甲基化控制基因表达并维持基因组稳定性。甲基转移酶如何靶向特定的DNA序列进行甲基化在很大程度上是未知的。在这里，我们表明，组蛋白H3尾巴缺乏赖氨酸4（K4）甲基化的功能作为一个变构激活剂甲基转移酶Dnmt3a结合到其植物同源结构域（PHD）。在体外，组蛋白H3肽刺激Dnmt3a的甲基化活性高达8倍，与K4甲基化水平呈负相关。变构调节的生物学意义通过分子建模和鉴定Dnmt3a的PHD和催化结构域中的关键残基来体现，其突变损害H3肽对甲基化活性的刺激，但不损害H3肽的结合。值得注意的是，这些突变的Dnmt3a蛋白在小鼠胚胎干细胞中表达时，在DNA甲基化中几乎是无活性的，而它们对基因组靶标的募集没有改变。因此，我们提出了一个两步机制从头DNA甲基化的第一次招聘的甲基转移酶可能协助染色质或DNA结合因子，然后变构激活依赖于Dnmt 3a和组蛋白尾部之间的相互作用，后者可能作为一个检查点的甲基化活性。
Cytosine methylation of genomic DNA controls gene expression and maintains genome stability. How a specific DNA sequence is targeted for methylation by a methyltransferase is largely unknown. Here, we show that histone H3 tails lacking lysine 4 (K4) methylation function as an allosteric activator for methyltransferase Dnmt3a by binding to its plant homeodomain (PHD). In vitro, histone H3 peptides stimulated the methylation activity of Dnmt3a up to 8-fold, in a manner reversely correlated with the level of K4 methylation. The biological significance of allosteric regulation was manifested by molecular modeling and identification of key residues in both the PHD and the catalytic domain of Dnmt3a whose mutations impaired the stimulation of methylation activity by H3 peptides but not the binding of H3 peptides. Significantly, these mutant Dnmt3a proteins were almost inactive in DNA methylation when expressed in mouse embryonic stem cells while their recruitment to genomic targets was unaltered. We therefore propose a two-step mechanism for de novo DNA methylation–first recruitment of the methyltransferase probably assisted by a chromatin-or DNA-binding factor, and then allosteric activation depending on the interaction between Dnmt3a and the histone tails–the latter might serve as a checkpoint for the methylation activity.