Introduction

    Oxidative stress occurs in all organisms and can cause cell damage by breaking apart DNA, destroying proteins and the cell membrane.  Oxidative stress occurs when an excess reactive O2 species such as H2O2, superoxide anion and hydroxyl radicals become reduced by stealing electrons from cellular molecules. By removing electrons from cellular molecules, reactive oxygen molecules can oxidize amino acid chains, form protein-protein cross linkages, and oxidize peptide backbones, causing protein instability (Berlett, 1997). In humans, oxidative stress is in involved in many human diseases including Alzheimer’s disease, respiratory distress syndrome, muscular dystrophy, cancer, neurodegenerative and cardivascular diseases (Sun 2004). Cells, however, have ways of combating oxidative stress with cellular anti-oxidant factors such as superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase (G6PD) (Slekar 2009).  Succinate semialdehyde dehydrogenase (SSADH) is also involved in oxidative stress tolerance in the glutamate catabolic pathway (Coleman 2001).

     In the glutamate catabolic pathway, gamma aminobutyric acid (GABA) is converted to succinate semialdhyde and then succinate.  SSADH is the catalyst for the conversion of succinate semialdhyde to succinate and also reduces NADP to NADPH (Coleman 2001).  Under oxidative stress conditions,  NADPH acts as an oxidizing agent of harmful free radicals. 

    Common yeast, or Sachromyces cerevisiae is used as a model in studying oxidative stress because it is a single celled eukaryote that can be grown easily, can be manipulated and therefore studied, has a completely sequenced genome, and can be in haploid or diploid form.  Yeast also contains anti-oxidant genes found in all eukaryotes making it a great model for the study of oxidative stress.
   

    G6PD is produced by the zwfl gene.  Prior research done by Sleker et al. (unpublished data) found that ΔZwfl was sensitive to O2, exhibited methionine auxotrophy, and were incredibly sensitive to oxidizing agents (Slekar 2009). In a genetic study of anti-oxidant factors in Yeast. Slekar et al. also found that ZMS1 and ZMS2 genes are suppressors of the zwf1 mutant phenotype (unpublished data).  These genes suppressed the mutant zwf1 phenotype by allowing the cells to grow without methionine in the media, under aerobic conditions and in the presence of H2O2.  It was discovered that ZMS1 and ZMS2 potentially encode zinc-finger transcription factors.  We are using microarrays to study expression differences and test the hypothesis that ZMS1 and ZMS2 increase the activity of stress response genes, which in turn suppress mutant zwf1 and thus prevent oxidative stres.

    Microarrays can be utilized to study and compare gene expression in organisms.  Therefore, a knockout yeast strain containing a deletion mutant in the gene ZMS1 or ZMS2 was compared to a wildtype yeast strain.  Both the mutant strains and the wild type were grown under the same conditions in order to determine the mutant's effect on gene expression.

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