Abstract 1446 A novel link between mitochondrial energy metabolism and ubiquitin conjugase Rad6

Oxidative stress, where cells accumulate reactive oxygen species (ROS), is a harmful phenomenon known to damage biomolecules, foster cell death, and contribute to neurodegeneration. In response to stress, we found that deletion of yeast RAD6 (rad6Δ) results in reduced cellular growth, ROS accumulation, and increased mitochondrial gene expression. Here, I hypothesize that in the absence of Rad6, compensatory mechanisms at the mitochondria are employed to sustain cell viability. We first showed that rad6Δ has greater levels of the mitochondrial protein porin than the WT strain, suggesting that rad6Δ has more mitochondria. To further explore mitochondrial biology, we used gene expression analysis to show that rad6Δ displays higher expression of respiratory and glucose transporter genes. Because yeast cells primarily derive their energy from fermentation, which does not require mitochondrial activity, these results suggest that Rad6's absence reprograms energy metabolism. To explore mitochondrial activity, we performed fluorescent microscopy and found that RAD6 deletion increases active and ROS-producing mitochondria, suggesting that rad6Δ relies on mitochondria for energy. To test this, we incubated WT and rad6Δ with mitochondrial-inhibitors, CCCP and antimycin, and found that rad6Δ growth was more susceptible to both, suggesting that rad6Δ is more reliant on mitochondrial energy production for growth. We then hypothesized that increased ROS accumulation could lead to increased mitochondrial degradation, or mitophagy. Using a mitophagy reporter, we observed higher levels of mitochondrial protein degradation in rad6Δ. My model suggests a role for Rad6 in energy metabolism and mitochondria biology and my future investigation will explore Rad6's regulation of respiratory gene expression through histone modification. Further investigation of Rad6's role in yeast energy metabolism will yield novel insights into fundamental processes of cellular adaptation to dynamic environments. Funding was provided by the Duke University Trinity College of Arts and Sciences and the Duke Undergraduate Research Support Office.