Role of the blm5 -1 mutation of Saccharomyces cerevisiae in DNA repair and meiosis and a potential requirement of vacuolar metabolism in the repair of bleomycin-induced double -strand breaks.
Item
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Title
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Role of the blm5 -1 mutation of Saccharomyces cerevisiae in DNA repair and meiosis and a potential requirement of vacuolar metabolism in the repair of bleomycin-induced double -strand breaks.
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Identifier
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AAI9946195
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identifier
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9946195
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Creator
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Martinez, Marcia Teresa Cheryl.
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Contributor
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Adviser: Carol Wood Moore
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Biology, Genetics | Biology, Cell
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Abstract
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Mutational alteration of the BLM5 gene of the model eukaryote, Saccharomyces cerevisiae, confers extreme hypersensitivity to lethal effects of ionizing radiation and anticancer bleomycins. Since bleomycin hypersensitivities in blm5-1 mutant strains were unrelated to drug accumulations in the cells, a possible role in the repair of radiomimetic damage was proposed for the Bhn5p. This hypothesis was examined in two parts: The global repair of chromosomal doublestrand breaks (DSBs) and the isolation of genes that functionally complemented the bleomycin hypersensitivity conferred by the blm5-1 mutation.;Pulsed field gel electrophoresis (PFGE) was used to examine the induction and repair of chromosomal DSBs in BLM5/BLM5, BLM5/blm5-1 and blm5-1/ blm5-1 strains before and after bleomycin treatments and during post-treatment incubation in phosphate buffer. Analyses showed that DSBs were processed in cycles of chromosomal degradation and rejoining. Spontaneous DSBs accumulated and were repaired in the BLM5/BLM5 and BLM5/blm5-1 cells, but did not accumulate in blm5-l/blm5-1 cells. Bleomycin-induced DSBs occurred in a dose-dependent manner and were repaired in all strains. However, repair was slowest in blm5-1/blm5-1 cells, suggesting rates of repair induction influenced bleomycin hypersensitivity. In addition to genotype, numbers of breaks and the temperature of post-treatment incubation affected repair rates.;The VPS8 gene was shown to functionally complement the blm5-1 mutation and the VPS3 and PEP7 genes were identified on two additional plasmids with blm5-1 complementing activity. This result, together with the observation that blm5-1 mutants display the reduced mitotic growth rate and sporulative abilities associated with vacuolar mutants, suggest that the BLM5 gene could be either VPS8, VPS3, PEP7 or another gene involved in vacuolar metabolism. The Vps8p, Vps3p and Pep7p function with other gene products to mediate vesicular docking and fusion onto the endosome at the intersection of the endocytic and the vacuolar biogenesis pathways in yeast. If a relationship is uncovered in the future between Blm5p and one or more of the gene products of vacuolar metabolism it would suggest an important relationship between vacuolar metabolism and the rate of repair of bleomycin-induced DSBs.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
