Les Erickson

National Conferences on Undergraduate Research, Memphis, TN

The ubiquitin proteasome pathway is a well-known regulator of protein concentrations and activities in the eukaryotic cell. Ubiquitin is added to proteins by ubiquitinases, most commonly signaling degradation via the proteasome. In contrast, deubiquitinases (DUBs) cleave the bond between ubiquitin and a protein, saving the protein from degradation and restoring its function. Ubiquitinases and DUB’s play a regulatory role during periods of cell stress, when signaling proteins are regulated to enhance survival of the cell. They are involved in programmed cell death pathways, when damage due to stressors is too advanced for repair. Apoptosis, the most common programmed cell death in yeast, is triggered when reactive oxygen species cause cytochrome C to be released from the mitochondria to activate cell death proteins. Duf1, a ubiquitin-binding protein in the yeast Saccharomyces cerevisiae, binds to and activates two related DUBs, UBP13 and UBP9. To better understand Duf1’s regulation of these DUBs, we exposed a DUF1 knockout yeast strain to different stressors and analyzed their responses. Interestingly, when exposed to hydrogen peroxide the knockout strain showed significantly less death and could withstand more highly concentrated hydrogen peroxide than the wild type strain. This oxidative stress resistance seen with the DUF1 knockout strain suggests Duf1 is involved in apoptosis signaling pathways. We therefore hypothesize that Duf1 activates DUBs that protect signaling proteins involved in the activation of apoptotic pathways. Further analyses under different growth conditions are currently being performed to test this hypothesis.