Structure and Mechanism of the SET1/COMPASS H3K4 Methyltransferase Complex

项目摘要 组蛋白H3赖氨酸4（H3 K4）的甲基翻译后修饰是进化上保守的， 表观遗传标记，通常与所有真核细胞中的转录激活相关。的早期研究 酵母模型系统、S.酿酒酵母，不仅确定了SET 1/MLL家族的原型， 甲基转移酶是负责H3 K4单甲基化、双甲基化和三甲基化的酶，但也揭示了酵母 以Set 1为中心的蛋白质复合物，称为COMPASS，可稳定酶并赋予其催化活性。 H3 K4甲基转移酶的SET 1/MLL家族在动物中经历了显著的扩增。哺乳动物 已经进化出了总共六个不同的和功能上非冗余的家庭成员，每个成员也发挥作用， 在COMPASS或类似COMPASS的复合物中。值得注意的是，最近的研究表明，突变或 六种人类SET 1/MLL甲基转移酶的失调与一系列精神疾病相关。 疾病，包括精神分裂症，自闭症和智力障碍。其中一些出现故障 家族成员还与其他人类疾病如混合系白血病和先天性心脏病有关。 疾病尽管它们具有重要的生物学作用和它们与人类健康的高度相关性， SET 1/MLL H3 K4甲基转移酶的机制的理解是很大程度上缺乏，由于大的尺寸 大多数SET 1/MLL酶及其组装和调控相关的复杂性。迄今为止， 结构和生物化学研究集中在酵母的单个结构域和小片段上， 人SET 1/MLL酶和COMPASS亚基。许多问题，例如SET 1/MLL酶如何 结合并受到四种常见催化模块亚基的调节，即RBBP 5/Swd 1，WDR 5/Swd 3， ASH 2L/Bre 2和DPY 30/Sdc 1（人/酵母直系同源物），所得复合物如何识别H3 K4， 核小体和差异催化单与多H3 K4甲基化的背景下，以及如何活动， COMPASS和COMPASS样复合物受上游信号如H2 B单泛素化的调节 仍然不清楚。使用结构，化学和生物化学方法的组合，以及酵母细胞- 基于功能分析，我们拟对酵母Set 1的结构和功能关系进行剖析 COMPASS复合物作为模型系统，并将这项工作扩展到临床相关的人SET 1/MLL 配合物我们提出的研究有希望建立一个缺失的框架来理解 真核生物学中SET 1/MLL H3 K4甲基转移酶功能和调节的结构基础， 揭示与其功能障碍相关的各种人类疾病的分子机制。

Project Summary The post-translational modification of histone H3 lysine 4 (H3K4) by methyl groups is an evolutionarily conserved epigenetic mark that is generally associated with transcription activation in all eukaryotic cells. Early studies of the yeast model system, S. cerevisiae, have not only identified the prototype of the SET1/MLL family of methyltransferases as the enzyme responsible for H3K4 mono-, di-, and trimethylation, but also revealed a yeast Set1-centric protein complex, known as COMPASS, that stabilizes and confers catalytic activity to the enzyme. The SET1/MLL family of H3K4 methyltransferases has undergone a significant expansion in animals. Mammals have evolved a total of six distinct and functionally non-redundant family members, each of which also functions within a COMPASS or COMPASS-like complex. Remarkably, recent studies have shown that mutations or dysregulation of the six human SET1/MLL methyltransferases are associated with a spectrum of mental illnesses, including schizophrenia, autism, and intellectual disability disorders. Malfunctions of some of these family members are further linked to other human diseases such as mixed lineage leukemia and congenital heart disease. Despite their important biological roles and their high relevance to human health, a molecular and mechanistic understanding of the SET1/MLL H3K4 methyltransferases is largely lacking due to the large sizes of most SET1/MLL enzymes and the complexity associated with their assemblies and regulation. To date, most structural and biochemical studies have been focused on single domains and small fragments of the yeast and human SET1/MLL enzymes and COMPASS subunits. Many questions, such as how the SET1/MLL enzymes bind and become regulated by four common catalytic module subunits, namely RBBP5/Swd1, WDR5/Swd3, ASH2L/Bre2, and DPY30/Sdc1 (human/yeast ortholog), how the resulting complexes recognize H3K4 in the context of nucleosome and differentially catalyze mono- vs. multi-H3K4 methylation, and how the activities of COMPASS and COMPASS-like complexes are regulated by upstream signals such as H2B mono-ubiquitination remain unclear. Using a combination of structural, chemical and biochemical approaches, as well as yeast cell- based functional assays, we propose to dissect the structure and function relationship of the yeast Set1 COMPASS complex as a model system and extend this work to the clinically relevant human SET1/MLL complexes. Our proposed studies hold the promise to establish the missing framework for understanding the structural basis of the SET1/MLL H3K4 methyltransferase function and regulation in eukaryotic biology and unmasking the molecular mechanisms of various human diseases associated with their malfunction.