| Summary: | Thesis advisor: Anthony T. Annunziato === The histone acetyltransferase Hat1 is an enzyme that specifically acetylates newly synthesized histone H4 at positions K5 and K12 (or their homologous positions) in all eukaryotes. In Schizosaccharomyces pombe, the deletion of hat1 presents a mutant phenotype. The telomeres in a hat1-del strain become permissive for transcription, as analyzed by a telomeric ura4 marker gene. In this study, we evaluate the efficacy of high copy suppression of this hat1 deletion. Due to high-frequency recombination events in the telomere, it became necessary to create a hat1-rad52 double deletion strain that also contains a telomeric ura4 reporter. High copy suppressor screens for recovery of telomeric silencing yielded several promising transformants. Multiple rounds of testing were performed to assess the recovery of transcriptional repression at the telomere. It was found that despite the anti-recombination effect of deleting rad52, the ura4 reporter was still lost from the telomere through recombination. Additional observation of the hat1-del rad52-del ura4-tel strain revealed a significant synthetic slow-growth phenotype. The double mutant displays a greatly decreased growth rate compared to hat1-del, as well as increased cellular length. Further study showed unique phenotypes on various media, and gene expression studies showed unique patterns of regulation in this double mutant when compared to both a wild- type and its single mutant counterparts (hat1-del, rad52-del). In summary, the telomeric ura4 marker in a hat1-del strain of S. pombe is not stable and is lost by recombination at a high frequency. This has led to the discovery of a double mutant (hat1-del rad52-del) that displays a severe synthetically sick phenotype. === Thesis (MS) — Boston College, 2014. === Submitted to: Boston College. Graduate School of Arts and Sciences. === Discipline: Biology.
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