Structure and Mechanism of the SET1/COMPASS H3K4 Methyltransferase Complex

项目概要 组蛋白 H3 赖氨酸 4 (H3K4) 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。早期研究 酵母模型系统 S. cerevisiae 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、二甲基化和三甲基化的酶，而且还揭示了一种酵母 以 Set1 为中心的蛋白质复合物，称为 COMPASS，可稳定酶并赋予酶催化活性。 H3K4 甲基转移酶的 SET1/MLL 家族在动物体内经历了显着的扩展。哺乳动物 总共进化出了六个不同且功能上非冗余的家庭成员，每个成员也都具有功能 在 COMPASS 或类似 COMPASS 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心理障碍有关 疾病，包括精神分裂症、自闭症和智力障碍。其中一些故障 家庭成员与混合谱系白血病和先天性心脏病等其他人类疾病也有进一步的联系 疾病。尽管它们具有重要的生物学作用并且与人类健康高度相关，但分子和 由于尺寸较大，对 SET1/MLL H3K4 甲基转移酶的机制了解很大程度上缺乏 大多数 SET1/MLL 酶以及与其组装和调节相关的复杂性。迄今为止，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上 人类 SET1/MLL 酶和 COMPASS 亚基。许多问题，例如 SET1/MLL 酶如何 结合并受到四个常见催化模块亚基的调节，即 RBBP5/Swd1、WDR5/Swd3、 ASH2L/Bre2 和 DPY30/Sdc1（人类/酵母直系同源物），所得复合物如何识别 H3K4 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 COMPASS 类复合物受 H2B 单泛素化等上游信号调节 仍不清楚。结合使用结构、化学和生化方法以及酵母细胞- 基于功能测定，我们建议剖析酵母 Set1 的结构和功能关系 COMPASS 复合体作为模型系统，并将这项工作扩展到临床相关的人类 SET1/MLL 复合物。我们提出的研究有望建立理解缺失的框架 SET1/MLL H3K4 甲基转移酶功能和真核生物学调控的结构基础 揭示各种人类疾病与其功能障碍相关的分子机制。

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.