RNA Polymerase III Transcription Factor Complexes as Chromatin Boundary Elements

Louisiana State University, Baton Rouge LA

Investigators

Abstract

Intellectual merit: Within the nuclei of eukaryotic cells, the genomic DNA is associated with a diverse array of proteins to form chromatin. The type and form of these proteins can affect the structure of chromatin by creating "domains" that are permissive to transcription into RNA (euchromatin) or refractory to such processes (heterochromatin). The research described here focuses on one of the mechanisms through which chromosomal domains are established and regulated. 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. 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 serve as general genomic boundaries will be further tested and the molecular basis determined. Recent data suggests that, in addition to preventing the spread of repressive chromatin, Pol III complexes also act as insulators, in that they can prevent activation of a promoter by an enhancer. This project will also test hypotheses to explain the mechanism that allows Pol III complexes to function as boundary elements. Specifically, effects on positioning of nucleosomes and on sub-nuclear localization of the chromatin bound to Pol III will be examined. 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 tDNAs have a general extra-transcriptional function as insulators 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.