Signaling Patterns in the Saccharomyces cerevisiae Phosphoproteome under Oxidative Stress

A central question in biology is how cells adapt to environmental changes. Such changes are typically sensed and signaled through the cell to elicit a different proteomic composition that is optimal to survive in the new conditions. Protein phosphorylation plays a central role in the process of signal transduction and stress response. To date, most of the studies on stress response have focused on measuring mRNA levels, dismissing the effects on protein levels and post-translational modifications, which are crucial components to understanding the functional regulation in a cellular system. We are investigating the mechanisms and proteomic effects of oxidative stress by menadione in the model eukaryote Saccharomyces cerevisiae. We used labeling with stable isotopes (SILAC) to encode proteins in the control and stress conditions, and mass spectrometry to identify and quantify relative abundances (stress vs. control) of proteins and phosphorylation sites on a global scale. We are exploring which phosphorylation events drive a major stress response and how the proteome adapts to the new oxidative conditions. Further, we are correlating these changes to transcriptional dynamics. Our studies will reveal both insights on how cellular systems respond under oxidative stress at the protein level, and pathways signaling for stress response.