染色质重塑复合体NuRD的结构及功能研究

Dependent on ATP hydrolysis, chromatin remodelers alter the positions of nucleosomes in the genome or the structures of nucleosome itself to expose DNA, by which the following processes such as DNA replication, DNA repair and gene transcription would able to progress successfully without steric hindrance. ..The nucleosome remodeling and histone deacetylase (NuRD) complex represents a major type of four classes of chromatin remodelers. The NuRD complex consists of six family subunits. It has a unique dual enzymatic activity, containing an ATPase and a histone deacetylase among its subunits, as well as several modules that recognize epigenetic signals. It plays a vital role in transcription regulation and maintaining genome stability, whose dysfunction would lead to various kinds of cellular abnormalities including tumorigenesis，but the structure of NuRD complex and substrate interacting mechanism remain elusive...Here we propose to solve the three-dimensional structure of NuRD complex in its apo form and mono-nucleosome binding form, through which, we uncover the complex assembly mechanism, intramolecular interactions and relationship between these two enzyme activity. Further, we investigate how does NuRD complex integrate epigenetic signals and remodel chromatin structure. We believe that these studies would facilitate our understanding of chromatin remodeling as a fundamental biological process, as well as provide therapeutic avenues.

染色质重塑复合体（chromatin remodeler）通过水解ATP调节基因组上核小体的分布或构型，使暴露的DNA得以实现DNA复制、损伤修复、基因转录等功能。NuRD复合体是四大类染色质重塑复合体中的一类，特点包括：多亚基（6种），双活性（ATP水解酶和组蛋白去乙酰化酶）和信号整合（识别多个表观遗传信号）。NuRD调控基因转录和基因组稳定性等细胞功能，在发育等生理过程和肿瘤等病理过程发挥关键作用，但其结构及与核小体相互作用机制长期未能解决。本项目拟解析NuRD复合体及其与底物核小体复合物的三维结构，揭示复合物组装规律和各亚基相互作用关系，两种酶活性的相互关系，研究其整合染色质表观遗传信号、发挥染色质重塑功能的机制，为深入理解染色质重塑这一重要生命活动过程和相关疾病诊疗奠定基础。

染色质重塑复合体(chromatin remodeler)通过水解ATP调节基因组上核小体的分布或构型，使暴露的DNA得以实现DNA复制、损伤修复、基因转录等功能。NuRD复合体是四大类染色质重塑复合体中的一类，特点包括:多亚基(6种)，双活性(ATP水解酶和组蛋白去乙酰化酶 )和信号整合(识别多个表观遗传信号)。NuRD调控基因转录和基因组稳定性等细胞功能，在发育等生理过程和肿瘤等病理过程发挥关键作用，但其结构及与核小体相互作用机制长期未能解决。本项目拟解析NuRD复合体及其与底物核小体复合物的三维结构，揭示复合物组装规律和各亚基相互作用关系，两种酶活性的相互关系，研究其整合染色质表观遗传信号、发挥染色质重塑功能的机制，为深入理解染色质重塑这一重要生命活动过程和相关疾病诊疗奠定基础。在项目进行过程中，我们成功的制备了NuRD蛋白复合体和其底物单核小体，并组装了NuRD蛋白复合体-单核小体复合物，并对这些样品进行多轮的性质优化。随后，我们将这些样品应用于冷冻电镜结构研究。我们获得了NuRD复合体8 Å分辨率的初步冷冻电镜密度，该密度显示出较为清晰的复合体模块化分布形式。我们还获得了NuRD及其与底物单核小体复合物的初步冷冻电镜三维重构结果。该复合体密度较NuRD单体密度显示出明显的构型区别和多出的密度，提示核小体在复合物中的存在，以及核小体加入带来的复合物整体的构象变化。