调控甲基化酶Set2及其介导的组蛋白H3K36甲基化修饰的分子机制

Set2-mediated H3Lys36 (H3K36) methylation is one of the most important epigenetic marks. It has been demonstrated that this mark plays critical roles in many chromatin-based processes, including gene transcription, DNA repair and RNA splicing. Dysregulation of H3K36 methylation is closely associated with cancers and many other human diseases. H3K36 can be mono-, di-, and tri-methylated, and each distinct methylation state seems to be regulated and function differently. It has been reported that some regulators modulate the levels of H3K36 methylation, however, the regulatory mechanisms are still obscure. In this proposal, we plan to 1) study how different state of H3K36 methylation is regulated and how H3K36 monomethylation plays a role in DNA replication; 2) study how Bur1/Bur2 kinase, as one of those key regulators, alters Set2 protein levels and regulates H3K36 methylation; 3) identify novel nucleosomal residues on each histones that affect H3K36 methylation levels, and attempt to set up the genetic or physical interaction between these residues with Set2-associated regulators. Taken together, studying Set2 enzyme itself and investigating the molecular mechanism of Set2-mediated H3K36 methylation will provide the epigenetic basis of diagnosis and treatment of its associated human diseases.

甲基化酶Set2介导的组蛋白H3K36甲基化是重要的表观遗传修饰标记之一，已经被发现参与基因转录调控、DNA修复以及RNA剪接等多种以染色质为基础的生命过程，并且跟癌症及其他人类疾病紧密相关。H3K36存在单、双、三甲基化三种修饰形式，每种形式的调控机理和生理功能各不相同。目前已经报道一些调控蛋白质可以影响H3K36的甲基化修饰水平，但其调控机理尚不清楚。因此，本项目将重点研究：1) H3K36不同甲基化修饰的调控机制及单甲基化修饰在DNA复制中的作用; 2) 以细胞周期激酶Bur1/Bur2为例，研究该激酶是如何调控Set2蛋白稳定性及H3K36甲基化水平的；3) 筛选新的与H3K36甲基化相关的组蛋白氨基酸位点，建立这些氨基酸与Set2相关的调控蛋白质之间的直接联系。研究调控甲基化酶Set2及其介导的H3K36甲基化的分子机制将为相关人类疾病的诊断与治疗提供表观遗传学的理论依据。

甲基化酶Set2介导的组蛋白H3K36甲基化是重要的表观遗传修饰标记之一，已经被发现参与基因转录调控、DNA损伤修复以及RNA剪接等多种以染色质为基础的生命过程，并且跟癌症及其他人类疾病紧密相关。目前已经报道一些调控蛋白质可以影响H3K36的甲基化修饰水平，但其调控机理尚不清楚。本项目主要研究了以下三方面的内容：1)发现细胞周期激酶Bur1/Bur2通过直接磷酸化Set2蛋白，既可以调控Set2蛋白稳定性；又可以帮助Set2蛋白招募到染色质上，促进H3K36me2/me3甲基化水平；2)通过构建组蛋白氨基酸定点突变的H2A/H2B文库，建立并筛选出了13个影响H3K36me3修饰的氨基酸位点和5个影响H3K36me2的氨基酸位点，发现这些位点可能在介导Set2蛋白与核小体的相互作用以及组蛋白修饰之间的crosstalk中发挥作用。3)发现组蛋白去甲基化酶Rph1在正常生长条件下可以负调控DNA修复基因的表达。在DNA损伤发生时，Rph1需要通过Gcn5介导的乙酰化修饰与核孔复合物结合后转运出核，最后通过细胞质中的自噬途径进行蛋白质降解，从而维持细胞的稳态。过多Rph1蛋白的存在将造成细胞非正常死亡的发生，破坏细胞的正常生命活动。以上三方面研究结果为我们进一步理解H3K36甲基化修饰的动态调控机制提供帮助。研究甲基化酶Set2或去甲基化酶Rph1及其介导的H3K36 甲基化的分子机制将为相关人类疾病的诊断与治疗提供表观遗传学的理论依据。