Histone Eviction and Mediator Function in Transcriptional Activation in Yeast

Health Research Incorporated/New York State Department Of Health, Menands NY

Investigators

Abstract

Intellectual merit: The long term goal of this project is to gain new understanding into mechanisms of transcriptional control in eukaryotes. Regulation of gene transcription is central to growth, development, and response to environment in all cells; thus, understanding transcriptional control is a central goal in genetics. The specific goals of this project are to gain new insight into chromatin remodeling during gene activation, and into the role of the Mediator complex in gene regulation. DNA in higher organisms, including humans, is packaged into nucleosomes by wrapping around an octamer of histone proteins. This creates a potential impediment to protein-DNA interactions needed for transcription of DNA into RNA, and so at many genes these nucleosomes must be remodeled to allow transcription to occur. This project will focus on chromatin remodeling at the CHA1 gene in the yeast Saccharomyces cerevisiae. Genetic and biochemical approaches will be used to examine the mechanism by which remodeling leads to histone eviction at CHA1 and at additional inducible promoters. Studies will also be conducted to investigate the role of the Mediator complex in transcriptional regulation in yeast. Mediator is a large, multi-subunit complex, comprising tail, middle, and head modules that bridges activators, whose binding is the initial step in gene activation, and the general transcription machinery. Mediator is highly conserved across the eukaryotic kingdom, and serves as a conduit for many regulatory signals, but the mechanism by which it controls gene expression is not well understood. Research will be carried out to determine whether one specific part of the Mediator complex, called the tail module, has specific functions aside from its requirement for recruitment of the middle and head modules, and to determine the role of the tail module of Mediator in CHA1 activation, in genome-wide recruitment of Mediator, and in transcriptional repression. Overall, this project will provide new information on fundamental aspects of transcriptional activation which at present is poorly understood. Transcriptional mechanisms are well conserved across eukaryotes. Hence, the information gained from this work will be broadly applicable. Broader impact This research will include training of a graduate student and postdoctoral fellow. In addition, undergraduates will be recruited to participate in this project as summer interns, to be funded by REU supplements. The project will also result in generation of large data sets from microarray studies, and these will be made publicly available, both by providing raw data files to a public repository (GEO), and by making more user-friendly, processed data files available for download from the principal investigator's web site.