The conserved Paf1 complex is important for proper gene expression in both yeast and humans. The Paf1 complex has been shown to repress the transcription of numerous genes. However, the mechanism by which the Paf1 complex mediates transcriptional repression remains largely unstudied. Here I use ARG1 as a model gene to investigate transcriptional repression by the Paf1 complex in Saccharomyces cerevisiae. Interestingly, I found that Paf1 complex-dependent histone modifications that are normally associated with active transcription are enriched on the ARG1 coding region and contribute to repression. The Rtf1 subunit of the Paf1 complex appears to mediate ARG1 repression primarily through histone H2B ubiquitylation and histone H3 K4 methylation. However, Paf1 has repressive functions aside from these histone modifications. Interestingly, occupancy of the activator Gcn4 is increased at the ARG1 promoter in paf1Δ cells, resulting in ARG1 derepression that is dependent on the histone acetyltransferase Gcn5 and histone H3 acetylation sites. Together my results suggest that Paf1 mediates ARG1 repression by preventing Gcn4 recruitment to the ARG1 promoter and subsequent histone H3 acetylation. I found that Paf1 does not alter nucleosome occupancy at the ARG1 promoter. However, I detect antisense transcription in the ARG1 promoter that positively correlates with ARG1 sense transcription. Interestingly, Paf1 prevents antisense transcription from traversing the ARG1 promoter, representing a potential mechanism by which the Paf1 complex controls promoter accessibility and ultimately ARG1 expression. Given these results, I hypothesize that the Paf1 complex mediates ARG1 repression partially by facilitating histone modifications that are refractory to ARG1 transcription and partially by inhibiting antisense transcription which controls promoter accessibility. Importantly, events that I observed at my model gene, ARG1, are demonstrated at other Paf1 complex-repressed genes.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08092011-234909 |
| Date | 16 September 2011 |
| Creators | Crisucci, Elia Marie |
| Contributors | Jeffrey Brodsky, Paula Grabowski, Martin Schmidt, Joseph Martens, Karen Arndt |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-08092011-234909/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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