The N-terminus of histone H3 is required for de novo DNA methylation in chromatin
The N-terminus of histone H3 is required for de novo DNA methylation in chromatin
复制标题
组蛋白 H3 的 N 末端是染色质中 DNA 从头甲基化所必需的
DOI：
10.1073/pnas.0905767106
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发表时间：
2009-12-29
影响因子：
11.1
通讯作者：
Xu, Guo-Liang
中科院分区：
文献类型：
--
作者：
Hu, Jia-Lei;Zhou, Bo O.;Xu, Guo-Liang
DNA甲基化和组蛋白修饰是两种主要的表观遗传途径，它们相互作用调节转录活性和其他基因组功能。Dnmt3L是从头DNA甲基转移酶Dnmt3a和Dnmt3b的调节因子。虽然最近的生化研究表明，Dnmt 3L结合到尾部的组蛋白H3与未甲基化的赖氨酸4在体外，染色质成分的DNA甲基化的要求还没有检查，和功能的证据，组蛋白尾部连接到DNA甲基化仍然缺乏。在这里，我们使用芽殖酵母酿酒酵母作为模型系统，通过小鼠Dnmt3a和Dnmt3L的异位表达来研究DNA甲基化的染色质决定因素。我们发现组蛋白H3尾的N端是从头甲基化所必需的，而包含赖氨酸9和27的中心部分以及H4尾是甲基化的。DNA甲基化主要发生在缺乏H3K4甲基化的异染色质区域。在缺失H3K4甲基化的突变株中，DNA甲基化水平增加了5倍。Dnmt3a的甲基化活性很大程度上取决于Dnmt3L的PHD结构域识别具有未甲基化赖氨酸4的组蛋白H3尾。Dnmt3L在小鼠ES细胞中的功能分析证实，Dnmt3L的PHD结构域的染色质识别能力确实是内源性Dnmt3L基因启动子处的有效甲基化所必需的。这些发现建立了组蛋白H3尾的N末端与未甲基化的赖氨酸4作为DNA甲基化的染色质决定簇。
DNA methylation and histone modification are two major epigenetic pathways that interplay to regulate transcriptional activity and other genome functions. Dnmt3L is a regulatory factor for the de novo DNA methyltransferases Dnmt3a and Dnmt3b. Although recent biochemical studies have revealed that Dnmt3L binds to the tail of histone H3 with unmethylated lysine 4 in vitro, the requirement of chromatin components for DNA methylation has not been examined, and functional evidence for the connection of histone tails to DNA methylation is still lacking. Here, we used the budding yeast Saccharomyces cerevisiae as a model system to investigate the chromatin determinants of DNA methylation through ectopic expression of murine Dnmt3a and Dnmt3L. We found that the N terminus of histone H3 tail is required for de novo methylation, while the central part encompassing lysines 9 and 27, as well as the H4 tail are dispensable. DNA methylation occurs predominantly in heterochromatin regions lacking H3K4 methylation. In mutant strains depleted of H3K4 methylation, the DNA methylation level increased 5-fold. The methylation activity of Dnmt3a largely depends on the Dnmt3L's PHD domain recognizing the histone H3 tail with unmethylated lysine 4. Functional analysis of Dnmt3L in mouse ES cells confirmed that the chromatin-recognition ability of Dnmt3L's PHD domain is indeed required for efficient methylation at the promoter of the endogenous Dnmt3L gene. These findings establish the N terminus of histone H3 tail with an unmethylated lysine 4 as a chromatin determinant for DNA methylation.