Eos1 involvement in zinc homeostasis

EOS1 is required for tolerance to oxidative stress in Saccharomyces cerevisiae; mutants are defective in the gene sensitive to hydrogen peroxide and tolerant to tunicamycin. To clarify the function of Eos1, we screened yeast genomic DNA libraries for heterologous genes that, when overexpressed from a plasmid, can suppress the hydrogen peroxide-sensitive eos1 mutation. We identified such a gene as IZH2, which has previously been reported to be a Zap1-regulated gene. However, the EOS1 and IZH2 genes do not themselves appear to be functionally interchangeable. Double disruption of the EOS1 and IZH2 genes yielded a slow-growth phenotype, suggesting that the two proteins are involved in related cellular processes. DNA microarray analysis revealed decreased expression of Zap1-regulated genes in the eos1-deletion mutant (delta eos1). Thus, it is likely that Eos1 is involved in zinc homeostasis. Yeast cells were cultivated in YPD at 30 oC with shaking at 150 rpm, and then the cells were harvested at the log phase (OD600=1.0). Affymetrix Yeast Genome 2.0 arrays (Affymetrix, Santa Clara, CA, USA) were used as the DNA microarrays. Statistical analysis of the expression data were performed using GeneSpring ver. 7.3.1 (Agilent Technologies, Palo Alto, CA, USA) based on the gene expression data from two independent experiments.