染色质重构复合物SRCAP/SWR1介导的H2A.Z染色质组装机制研究

The nucleosome core particle is composed of four core histone proteins or their variants. H2A.Z is an essential histone variant in higher eukaryotes and plays important roles in gene transcription, genome stability and DNA damage response. H2A.Z is incorporated in chromatin by SRCAP(SWR1), an ATP-dependent, multi-component chromatin remodelling complex via a process called SRCAP(SWR1)-catalyzed histone H2A.Z replacement. In mammals, The SRCAP(SWR1) chromatin remodelling subunits YL1 and SRCAP play essential roles in recognition of H2A.Z-H2B and H2A nucleosome, but how they achieves this has been unclear. Recently, the author revealed the structural basis of H2A.Z recognition by YL1 subunit. Here, by applying a combination of structural, biophysical, biochemical and genetic approaches, we would address the functional roles of other YL1 domains in recognition of nucleosome, and reveal the recognition mechanism of H2A.Z-H2B by human SRCAP subunit. The knowledge we gain in this study is critical to understanding not only the mechanism by which H2A.Z incorporates into the chromatin, but also the complex rules which govern epigenetic regulation and human diseases development.

核小体核心颗粒由四种常规组蛋白或组蛋白变体组成。H2A.Z是高等真核生物必需的组蛋白变体，在基因转录调控等生命进程中发挥重要作用。染色质重构复合物SRCAP/SWR1催化H2A.Z-H2B替换染色质中的H2A-H2B，实现H2A.Z的染色质组装。YL1和SRCAP亚基是哺乳动物SRCAP复合物行使功能的必需因子，两者识别底物H2A.Z和H2A核小体并介导H2A.Z的交换反应。申请人的前期研究阐明了YL1的N末端结构域（YL1-Z）特异识别H2A.Z-H2B的结构与分子机制。在本项目中，申请人拟采用结构生物学、生物化学、高通量测序、酵母遗传学等多种方法研究YL1亚基的多个结构域进行H2A核小体特异识别的结构和分子机制；并通过研究SRCAP亚基识别H2A.Z-H2B的机制，揭示SRCAP亚基与YL1的相互关系。本项目对于阐明H2A.Z的染色质组装机制，揭示其表观遗传调控方式具有重要意义。

H2A.Z是高等真核生物必需的组蛋白变体。H2A.Z与肿瘤和发育相关等人类疾病关系密切，在DNA转录、复制、修复、以及基因组稳定性维持等生命活动中发挥重要作用。染色质重构复合物SRCAP/SWR1 催化H2A.Z-H2B替换染色质中的H2A-H2B，实现H2A.Z的染色质组装，该过程受到特定组蛋白伴侣的调控。本项目对SRCAP/SWR1的功能亚基YL1、Swc5、以及Chz1等组蛋白伴侣在H2A.Z交换反应中的功能和作用机制开展了研究。本项目采用X射线衍射晶体学、生物化学、基因组学等多种方法揭示了YL1、Swc5、Chz1特异识别H2A.Z-H2B的全新模式，发现Swc5和Chz1通过促进H2A的移除和H2A.Z的传递这两种新的模式调控H2A.Z交换，从而揭示了Swc5、Chz1在H2A.Z交换反应中的功能,拓展了对H2A.Z特异识别机制的理解。本项目采用冷冻电镜、溶液核磁共振、单分子磁镊等多种方法测定了组蛋白变体H2A.B形成的开放核小体结构，阐明了YL1特异识别H2A核小体的分子机制，从而揭示了组蛋白变体调控染色质结构和动态变化的新方式。综上所述，本项目的开展为阐明H2A.Z进行染色质组装的机制，理解H2A.Z的重要生物学功能奠定了基础，具有重要的理论意义和潜在的应用价值。