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Title: The repair of DNA damage in Saccharomyces cerevisiae
Author: Yu, Y.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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In this thesis, the contribution of components of BER and NER to the repair of oxidative DNA damage in Saccharomyces cerevisiae was examined. Deletion of OGG1 does not result in a hypersensitivity of yeast cells to a treatment with Ro 19-8022 plus light which is acknowledged to induce oxidative damage to DNA, with a majority of that being 8-oxoguanine, while both single mutants of ntg1 or ntg2 showed a moderate sensitivity to Ro 19-8022 plus light, and the double mutant of ntg1ntg2 was more sensitive to the treatment than either single mutant. A strain defective in both BER and NER (rad1ogg1ntg1ntg2 mutant) showed the highest sensitivity to Ro 19-8022 plus light among all strains tested. Both spontaneous and induced mutation frequencies (CanR and Lys+) were elevated in a BER defective strain (ogg1ntg1ntg2) compared to the wild type, and further deletion of RAD1 in the BER defective background (rad1ogglntg1ntg2) incurred a further increase of these mutation frequencies. A GC to TA mutation in a tRNASer gene was found in a portion of Lys+ mutants, which allows the suppression of the lys1-1 ochre allele. To assess how DNA repair operates in a chromatin environment, photoreactivation of UV-induced CPDs was examined in the repressed MFA2 gene, and the repair was found to be quicker in the linker regions than in nucleosome-bound regions. In the active MFA2, positioned nucleosomes are disrupted and PR of the whole region became faster. Deletion of a histone acetyltransferase, Gcn5 does not impair the expression of the PHR1 gene (a gene responsible for the PR in S. cerevisiae), nor the total PR capability. However, the PR of both the transcribed and non-transcribed strands of the active MFA2 gene was markedly impaired, so was that of the RPB2 gene, but to a less extent. Hence, it appeared that a local Gcn5-dependent chromatin modification is able to modulate the access of photolyase to its targets in chromatin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available