NSF Award
0549246
The goal of this project is to gain new understanding into the mechanisms that are involved in facilitating transcription through nucleosomes. The DNA of eukaryotes is packaged into ordered arrays of nucleosomes. Each nucleosome consists of 145 bp of DNA that is wrapped around a complex of eight proteins that are referred to as 'histones'. These histones are highly basic in nature and strongly bind DNA. While these high binding energies are required to facilitate packaging of the DNA, they also extensively restrict nuclear functions such as transcription, replication and DNA repair. It is therefore of importance to understand the cellular mechanisms that alleviate these interactions and facilitate these nuclear functions. A defined in vitro system has been established which can substantially reproduce three important aspects of in vivo transcription: 1. the topological stress that is produced by the polymerase; 2. the unique metabolic modifications that are present on the nucleosomal histones of active genes; 3. the histone chaperones that can potentially modulate the interactions of histones with DNA. Previous results from this laboratory have indicated that specific subsets of the histones displace from the DNA in unique ways as a result of variable use of these three conditions. As a result transcription is greatly facilitated. This project will apply site-specific mutagenesis to key residues within the sequences of these histones to ascertain the specific nature of the structural transitions within them and therein define why a particular cellular condition promotes access to the DNA. Specific aspects of this project are also designed to promote the educational experience of high school, undergraduate and graduate students.
