Within the nuclei of eukaryotic cells, genomic DNA is associated with numerous different proteins to form a structure referred to as chromatin. These proteins can be either directly bound to DNA, or bound via interactions with other proteins. These proteins can have a variety of influences on which genes are expressed in different cells, and also govern the amount of gene expression under different environmental conditions. The research described here focuses on how proteins of the RNA Polymerase III (Pol III) system affect expression of other genes that are transcribed by other eukaryotic RNA polymerases. Previous work established that tRNA genes (tDNAs), with their assembled RNA Polymerase III (Pol III) protein complexes, function as barriers to the spread of repressive chromatin in yeast, and as insulators to gene activation. These results indicated that Pol III complexes are involved in demarcating the boundaries of chromosomal domains. In this project, the idea that Pol III genes exhibit additional 'extra-transcriptional' functions beyond their role in synthesizing small RNA molecules will be further examined. Recent data suggests that Pol III complexes can have direct effects on the level of Pol II transcription, and that Pol III complexes also prevent inappropriate elongation by Pol II. This project will also test hypotheses to explain the mechanism that allows Pol III complexes to function in these capacities. Finally, the research will evaluate which proteins of the Pol III complex are necessary and sufficient for such functions.
Broader impacts: From a scientific perspective, the significance of this study is to determine whether Pol III complex proteins have general extra-transcriptional functions in yeast, which may have far-reaching implications in the regulation of gene expression in other eukaryotes. In addition to direct scientific advancement, the research will have a significant impact in education, allowing the training of graduate students, and the nurturing of research interests of promising undergraduates.