Molecular Mechanisms of Eukaryotic Transcriptional Regulation

Myers lab - January 2009

My laboratory's research is designed to reveal the fundamental mechanisms that facilitate positive and negative eukaryotic gene regulation on the molecular level. We primarily use a biochemical approach to dissect and then reconstitute these processes from purified proteins and nucleic acids as a starting point for mechanistic studies. Studying transcription in the yeast Saccharomyces cerevisiae allows us to utilize a combination of genetic, genomic, biochemical, chemical and structural techniques to understand exactly how transcriptional activators and repressors work in eukaryotic cells. Currently our research is focussed on two novel aspects of gene regulation.

1. How are epigenetic transcriptional states maintained in S. cerevisiae and pathogenic fungi?

An epigenetic change in gene expression is a alteration in the state of expression of a gene that does not involve a mutation, but that is nevertheless inherited in the absence of the signal (or event) that initiated the change. There are many examples of epigenetic regulation from bacteria to mammals. We are particularly interested in epigenetic phenotypic switching mechanisms in pathogenic fungi that are critical for their infectivity in immunocompromised patients in the clinic. In eukaryotic cells, many epigenetic transcriptional states are associated with changes in the structure and post-translational modification of chromatin. The two major questions in this field are: How are epigenetic transcriptional states inherited? and once established how do these states confer a state of expression or silencing on particular genes? Our current research is focused on investigating an unexpected mechanism of epigenetic transcriptional silencing involving protein-chromatin interactions. We have recently shown that a specific post-translational modification of histones plays a critical role in this process. We are investigating this phenomena in both S. cerevisiae and pathogenic fungi.

2. How does the sequence and chromatin structure of core promoters influence the mechanism of transcriptional initiation and its regulation?

Recent bioinformatic and genomic analysis has revealed that the regulation of eukaryotic genes is not simply controlled by 'transcription factors' binding to specific sites upstream of a core promoter. The sequence of the core promoter itself, as well as the position and post-translational modification, state of nucleosomes surrounding the core promoter, vary widely and make a critical contribution to differential gene regulation. These differences lead to the assembly of transcription initiation complexes that can differ from the canonical view of RNA Pol II transcription. Using our unique purified transcription system, it is our goal to characterize these novel transcription initiation complexes and discover the mechanisms used to facilitate basal and activated transcription at different core promoter sequences.