Coordinated activities of wild-type plus mutant EZH2 drive tumor-associated hypertrimethylation of lysine 27 on histone H3 (H3K27) in human B-cell lymphomas
Coordinated activities of wild-type plus mutant EZH2 drive tumor-associated hypertrimethylation of lysine 27 on histone H3 (H3K27) in human B-cell lymphomas
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DOI：
10.1073/pnas.1012525107
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发表时间：
2010-12-07
影响因子：
11.1
通讯作者：
Copeland, Robert A.
中科院分区：
文献类型：
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作者：
Sneeringer, Christopher J.;Scott, Margaret Porter;Copeland, Robert A.
PRC 2复合物的催化亚基EZH 2催化组蛋白H3（H3 K27）上赖氨酸27的单-三甲基化。组蛋白H3 K27三甲基化是一种抑制组蛋白修饰位点附近特定基因转录的机制。据报道，EZH 2基因（Tyr 641）的点突变与人类B细胞淋巴瘤的亚群有关。在疾病细胞中总是发现突变等位基因与野生型等位基因（杂合）相关，并且据报道突变消除了PRC 2复合物用于甲基化未修饰的肽底物的酶活性。在此，我们证明WT酶对于H3 K27的零至单甲基化反应显示出最大的催化效率（k（cat）/K），并且对于随后的（单至二和二至三甲基化）反应显示出降低的效率。与此形成鲜明对比的是，疾病相关的Y 641突变显示出非常有限的进行第一次甲基化反应的能力，但相对于WT酶，对后续反应具有增强的催化效率。这些结果意味着疾病的恶性表型需要H3 K27单甲基化酶（含有WT EZH 2或EZH 1的PRC 2）与突变体PRC 2的组合活性，以增强H3 K27向三甲基化形式的转化。据我们所知，这是第一个依赖于正常和疾病相关突变酶功能协调活动的人类疾病的例子。
EZH2, the catalytic subunit of the PRC2 complex, catalyzes the mono-through trimethylation of lysine 27 on histone H3 (H3K27). Histone H3K27 trimethylation is a mechanism for suppressing transcription of specific genes that are proximal to the site of histone modification. Point mutations of the EZH2 gene (Tyr641) have been reported to be linked to subsets of human B-cell lymphoma. The mutant allele is always found associated with a wild-type allele (heterozygous) in disease cells, and the mutations were reported to ablate the enzymatic activity of the PRC2 complex for methylating an unmodified peptide substrate. Here we demonstrate that the WT enzyme displays greatest catalytic efficiency (k(cat)/K) for the zero to monomethylation reaction of H3K27 and diminished efficiency for subsequent (mono-to di- and di- to trimethylation) reactions. In stark contrast, the disease-associated Y641 mutations display very limited ability to perform the first methylation reaction, but have enhanced catalytic efficiency for the subsequent reactions, relative to the WT enzyme. These results imply that the malignant phenotype of disease requires the combined activities of a H3K27 monomethylating enzyme (PRC2 containing WT EZH2 or EZH1) together with the mutant PRC2s for augmented conversion of H3K27 to the trimethylated form. To our knowledge, this is the first example of a human disease that is dependent on the coordinated activities of normal and disease-associated mutant enzymatic function.