Dynamics of nucleosome assembly/disassembly affected by chromatin modifications

描述（由申请人提供）：核小体是真核生物染色质的基本DNA包装单位。核小体中DNA与组蛋白的动态相互作用在控制染色质结构和基因的可及性方面起着重要作用，是基因调控的重要组成部分。染色质修饰如DNA甲基化和组蛋白乙酰化是基因调控机制中的关键因素。DNA甲基化水平异常或组蛋白乙酰化缺陷导致各种发育/增殖性疾病，包括各种类型的癌症、白血病和鲁宾斯坦-泰比综合征。本研究的长期目标是阐明核小体动力学如何通过染色质修饰促进基因调控机制。这个项目的目标是揭示核小体动力学和染色质修饰之间的联系。目的是验证DNA甲基化和组蛋白乙酰化可能改变核小体组装/拆卸过程中DNA包裹/解开组蛋白的动力学，从而控制核小体组装/拆卸的效率的主要假设。由于基于整体平均测量和静态结构工具监测核小体动态结构变化的困难，染色质修饰对核小体动力学的影响从未得到明确解决。为了实现这些目标，我们将采用单分子多色荧光共振能量转移技术，在单分子水平上以时间分辨的方式监测核小体在有修饰和没有修饰的情况下组装/拆卸过程中DNA包裹/解开的实时动态。在DNA甲基化或组蛋白乙酰化的核小体组装/拆卸过程中，DNA包裹/打开的动力学速率的变化将被检验，以检验这一假设。如果成功地实现这些目标，将极大地促进我们从动力学角度理解DNA甲基化和组蛋白乙酰化的基因调控机制。该项目的研究结果将为DNA甲基化异常和组蛋白乙酰化缺陷引起的疾病的诊断和治疗提供新的和独特的基础。

DESCRIPTION (provided by applicant): Nucleosomes are the fundamental DNA packaging units of eukaryotic chromatin. Dynamic interaction between DNA and histones in the nucleosome play important roles in controlling the structure of chromatin and subsequently the accessibility of genes, which is an essential part of gene regulation. Chromatin modification such as DNA methylation and histone acetylation is a crucial element in the mechanisms of gene regulation. Abnormal levels of DNA methylation or defective histone acetylation lead to various developmental/proliferative disorders including various types of cancer, leukemia and Rubinstein-Taybi syndrome. The long-term objective of this research is to elucidate how nucleosome dynamics contribute to the mechanisms of gene regulation through chromatin modification. The goal of this project is to reveal the link between nucleosome dynamics and chromatin modification. The aims are to test the main hypothesis that DNA methylation and histone acetylation may alter the dynamics of DNA wrapping/unwrapping around histones during nucleosome assembly/disassembly and consequently control the efficiency of nucleosome assembly/disassembly. Due to the difficulty associated with monitoring dynamic structural changes of a nucleosome based on ensemble-averaging measurements and static structural tools, the effects of chromatin modification on the nucleosome dynamics have never been clearly addressed. In order to accomplish these aims, we will employ single molecule multi-color fluorescence resonance energy transfer to monitor the real-time dynamics of DNA wrapping/unwrapping during nucleosome assembly/disassembly with and without the modifications in a single molecule level in a time resolved manner. Changes in the kinetic rates of DNA wrapping/unwrapping during nucleosome assembly/disassembly upon DNA methylation or histone acetylation will be examined in order to test the hypothesis. The proposed aims, when successfully accomplished, will greatly facilitate our understanding of the mechanisms of gene regulation by DNA methylation and histone acetylation from a dynamics perspective. Results from the project will provide a novel and unique basis for the development of diagnoses and treatments of the diseases and disorders originated from abnormal DNA methylation and defective histone acetylation.