Role of Schizosaccharomyces pombe Methionine Sulfoxide Reductase (msr) Genes in Oxidative Stress Resistance

Thesis advisor: Clare O'ConnorAs organisms get older, the proteins in their cells also age, and as this happens, the amino acids that make up these proteins may become chemically modified and begin to lose their integrity. One example of an age-related modification occurs when the amino acid residue methionine is oxidized by a reactive oxygen species to methionine sulfoxide. Methionine sulfoxide reductase is an enzyme that repairs this damage to the protein by catalyzing a reaction that reduces methionine sulfoxide back to methionine. The fission yeast Schizosachharomyces pombe was used as the experimental model to study methionine sulfoxide reductase in vivo, taking advantage of the variety of tools available with which to study the organism. In S. pombe there are two genes encoding methionine reductase activities, msrA and msrB. The first goal of this project was to construct yeast strains in which the endogenous msrA and msrB genes had been inactivated. This was accomplished via homologous recombination reactions in which the msr genes were replaced with a selectable marker for biosynthesis of uracil (ura4+). After the construction and verification of the two knockout strains, the sensitivities of the strains to reactive oxygen species were tested. Both strains showed reduced resistance to oxidative stress. Future experiments will include more detailed analyses of the abilities of the strains to survive oxidative stress. Finally, the two knockout strains of yeast will be mated with one another in order to produce a double msr knockout, in order to examine the effects of a complete lack of methionine sulfoxide reductase activity on the organism.Thesis (BS) — Boston College, 2005.Submitted to: Boston College. College of Arts and Sciences.Discipline: Biology.Discipline: College Honors Program