Dynamics of nucleosome assembly/disassembly affected by chromatin modifications

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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. PUBLIC HEALTH RELEVANCE: Defects in DNA methylation or histone acetylation lead to lethal diseases and various developmental and proliferative abnormalities including various types of cancer, leukemia and Rubinstein-Taybi syndrome. The proposed project will make a novel and unique contribution to the development of diagnoses and treatments of the diseases and disorders associated with abnormal DNA methylation and defective histone acetylation.