Dynamics of Higher Order Chromatin Structure

In the last several years chromatin structure has been shown to be a highly dynamic entity, one through which DNA-centered processes such as transcription, replication, repair, and recombination are carefully controlled. A vast multitude of protein complexes alter chromatin structure through the exertion of mechanical work (ATP hydrolysis) or chemical modification (acetylation, methylation, and so on). Yet little is known about the higher-order structure of chromatin or how these many complexes perturb it, and it is therefore imperative that better approaches for examining higher-order chromatin structure be developed. In this project the investigator will engineer nucleosomes such that chemical modification and site-directed cross-linking can be used to monitor (1) the accessibility of a series of specific sites throughout the nucleosome and (2) their proximity to other regions. With this monitoring ability, the investigator will be able to identify the nucleosomal regions involved in the compaction of chromatin fibers, and to model the structure of the higher-order chromatin. The investigator will focus particularly on the structural changes that occur as the chromatin fiber transitions from a 10 nm fiber to a 30 nm fiber, and then to self-associated arrays. Currently it is extremely difficult to probe the structure of higher-order chromatin due to its inherent complexity (size, heterogeneity, and protein composition). So far most of the information available on higher-order structure has been derived from low resolution structures obtained by techniques such as electron and atomic force microscopy. Successful completion of this project will provide key missing structural information that will complement that obtained by these conventional methods and will also address fundamental questions concerning cell development and the organization and regulation of the genome.

This project will provide an enhanced learning experience for the undergraduate and graduate students involved in the project. As part of an undergraduate research class, students will be organized into small teams to make histone mutants and to participate in the large-scale purification of the engineered histones. Those in this project will meet weekly to present their own research, discuss recent publications on chromatin structure and function, and solve technical challenges. This research will augment Southern Illinois University's tradition of providing research opportunities to those from groups underrepresented in science and engineering.