Structure and Mechanism of the SET1/COMPASS H3K4 Methyltransferase Complex

项目摘要 组蛋白H3赖氨酸4(H3K4)被甲基基团翻译后修饰是一种进化保守的 表观遗传标记，通常与所有真核细胞中的转录激活有关。早期的研究 酵母模型系统，酿酒酵母，不仅鉴定了SET1/MLL家族的原型 甲基转移酶作为负责H3K4单甲基化、双甲基化和三甲基化的酶，还揭示了一种酵母 以SET1为中心的蛋白质复合体，称为COMPASS，它稳定并赋予酶催化活性。 H3K4甲基转移酶的SET1/MLL家族在动物中经历了显著的扩增。哺乳动物 总共进化了六个不同的、在功能上不多余的家庭成员，每个成员也都有 在指南针或类似指南针的复合体内。值得注意的是，最近的研究表明突变或 六种人类SET1/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、自闭症和智力残疾障碍。其中一些设备出现故障 家庭成员还与其他人类疾病有关，如混合血统白血病和先天性心脏病 疾病。尽管它们具有重要的生物学作用，而且与人类健康高度相关，但一种分子和 由于SET1/MLL H3K4甲基转移酶的大小，很大程度上缺乏对其机制的了解 大多数SET1/MLL酶以及与其组装和调控相关的复杂性。到目前为止，大多数 结构和生化研究主要集中在酵母的单个结构域和小片段以及 人SET1/MLL酶和COMPASS亚基。很多问题，比如SET1/MLL酶是如何 结合并受四个共同的催化模块亚基调节，即RBBP5/Swd1，WDR5/Swd3， ASH2L/Bre2和DPY30/Sdc1(人/酵母同源基因)，得到的复合体是如何识别H3K4的 核小体的背景和差异催化单H3K4甲基化与多H3K4甲基化，以及 COMPASS和类COMPASS复合体受上游信号的调控，如H_2B单泛素化 目前仍不清楚。使用结构、化学和生化方法的组合，以及酵母细胞- 在功能分析的基础上，我们建议剖析酵母Set1的结构和功能关系 Compass Complex作为模型系统，并将这项工作扩展到临床相关的人类SET1/MLL 复合体。我们提议的研究有望为理解 真核生物中SET1/MLL H3K4甲基转移酶功能及其调控的结构基础 揭开各种人类疾病与其故障相关的分子机制。

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.