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Title: Contributions of nucleotide and base excision repair to the repair of DNA oxidative base damage in Saccharomyces cerevisiae
Author: Neishabury, M.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1998
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In order to further investigate the contribution of NER to the repair of oxidative base lesions in Saccharomyces cerevisiae, a series of mutant strains were constructed that were deficient in NER, or in both NER and BER by disruption of the RAD14 gene via transformation in the wile type and OGG1 deficient strains respectively. In addition, another set of mutants was created by transforming the cells with a high copy number plasmid that over-expresses the OGG1 gene. The frequency of spontaneous forward mutation to canavanine resistance (CanR) was determined in these strains. The ogg1 mutant, the NER defective rad14, and the ogg1rad14 double mutant all showed similar significant increases in the frequency of spontaneous mutation to CanR relative to the wild type. The over-expression of the OGG1 gene only suppressed the frequency of spontaneous mutation to CanR in the ogg1 strain but not in the rad14, or ogg1rad14 mutants. These results suggested that NER also has a role in the removal of oxidative base damages, possibly via a DNA-protein or a protein-protein interaction between the BER and NER enzymes. In the canavanine forward mutation assay, the nature and position of the lesions in the gene are not known and this limits our ability to interpret the results. A more specific approach was undertaken by studying the role of NER in removal of 8-oxoG by determining the frequency of spontaneous GC to TA mutations using a specific tester system which detects a GC to TA base substitution event as a Cyc+ reversion mutation. These experiments did not show a significant increase in the frequency of Cyc+ reversion in the rad14 single mutant relative to the wild type, but there was a significant increase in reversion to Cyc+ in the ogg1 and ogg1rad14, with the latter showing an additional increase in Cyc+ reversion relative to the single ogg1 mutant.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available