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.

Project Report

The genetic information all living organisms harbor in their DNA is controlled at many different levels. This information is first copied into smaller molecules of RNA (ribonucleic acid), molecules that can either have a direct biological function on their own, or have their information translated into specific functional protein molecules. These molecules, along with others, determine how our individual cells behave, such as what makes skin cells different from blood cells and brain cells. If the production of these molecules is not controlled properly, problems can arise for any living organism, even causing diseases. Different genes are normally controlled by particular regions of DNA that are either near or within a gene. Many research studies may be too limiting in studying how genes function, as they often focus on looking at DNA controlling one particular gene. My lab has found that the proteins that bind to and control small RNA coding genes also have effects on nearby protein coding genes. Our work suggests that proper control of some genes directly depends on DNA previously thought to only control other neighboring genes. These studies are important, as some levels of gene regulation may not have been fully appreciated in past research, and may have implications in the control of many genes that may be important for normal biological functions and overall human and animal health. On a broader scale, my lab frequently employs undergraduate students to encourage their interests in scientific research, and I have a strong history of employing both women and minorities to help close the diversity gap of participants in scientific research. My lab also has hosted and mentored several high school students for both research and science fair project assistance.

National Science Foundation (NSF)
Division of Molecular and Cellular Biosciences (MCB)
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Roy Welch
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Louisiana State University & Agricultural and Mechanical College
Baton Rouge
United States
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