特异性组蛋白H3K36甲基化产物对基因转录和DNA损伤修复调控的研究

The mis-regulation of histone H3K36 methylation has been shown to be highly correlated with human tumorogenesis. As other histone lysines, H3K36 can exist in a mono-,di-or tri-methylated state (H3K36me1/2/3), which has been shown to regulate multiple processes including transcriptional regulation and DNA damage repair. However the detailed mechanism has not been fully understood. Meanwhile, 8 H3K36 specific methyltransferases are encoded in human cells with non-redundant functions, suggesting the complexity of human H3K36 methylation system. Our earlier study demonstrated the molecular mechanism of the product specificity control of yeast Set2 protein by using two F/Y switch mutants. We found that the different methyl-states on H3K36 (H3K36me1/2 and H3K36me3) played distinct roles in several functional pathways. We plan to modify human H3K36 mono-/di- methyltransferase NSD family proteins and tri-methyltransferase SETD2 to manipulate their product specificities. Moreover, by using these mutants we can study the impacts of the specific H3K36 methyl-state on transcription regulation of human immune response genes and genome stability maintenance. The significance of the above study is to unveil the detailed regulatory mechanism of H3K36 state-specific methylation and its downstream signaling pathways; to understand how epigenetic factors accurately regulate tumorogenesis and to direct the drug design for manipulating state-specific methylation of H3K36.

组蛋白H3K36甲基化修饰异常与人类恶性肿瘤的发生高度相关。其三种状态---H3K36me1/2/3参与调控基因转录及DNA损伤修复等生物学行为，但详尽的酶学调控机制和信号通路尚未完全阐明。人体多达8种H3K36甲基转移酶提示了人H3K36甲基化修饰和信号传导存在极复杂的调控与功能分化。本课题前期研究揭示酵母唯一的H3K36甲基转移酶Set2精细操纵H3K36me1/2/3的分子机制，发现不同状态的甲基化信号对基因转录等功能产生截然不同的影响。现拟采用前期研究掌握的改造Set2调控组蛋白甲基化的成熟技术，对人H3K36甲基转移酶进行改造，进而对免疫应答基因转录和DNA损伤修复调控进行研究。其意义在于：帮助阐释人组蛋白甲基化修饰及下游分子行为的精细调控机制；理解肿瘤等重大疾病发生的表观遗传学基础；并为研发以特异状态的H3K36甲基化为靶点的药物做出准确的指导。

组蛋白H3K36甲基化修饰的三种状态（H3K36me1/2/3）参与调控基因转录及DNA损伤修复等生物学行为，但详尽的酶学调控机制和信号通路尚未完全阐明。本项目通过对酵母和人H3K36甲基转移酶催化中心的“苯丙氨酸/酪氨酸”开关(F/Y) 的关键氨基酸进行改造，分别鉴定出特异的酵母和人H3K36me1/2,H3K36me3甲基转移酶突变体。随后应用这些突变体在酵母和人源细胞中对特定信号通路进行了深入研究。本项目发现在不同物种细胞中H3K36me1/2 和H3K36me3甲基化修饰信号承担着共同或差异的功能，这些发现有助于我们厘清同一位点不同状态的组蛋白甲基化修饰信号的特定生物学功能和意义。同时，本项目对识别组蛋白乙酰化修饰的溴结构域家族蛋白 (BET 家族) 在绿脓菌素介导巨噬细胞功能损伤和死亡过程中的表观调控机制进行了研究，并发现调控BET家族成员在脓菌素刺激下引起的氧化应激反应基因的转录可以抑制巨噬细胞死亡和功能损伤，从而维持巨噬细胞的天然免疫防御功能并提高机体对抗铜绿假单胞菌感染的能力。