Genetic requirements for executing SUMO stress signals and achieving stress tolerance

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Project Summary/Abstract: Temperature, radiation, oxidizing reagents, as well as shear and osmotic stress are environmental, extrinsic stressors that cause tissue and cellular damage. There is good evidence that organisms as diverse as yeast and humans utilize SUMO modification as part of their cellular stress response. SUMO is a small proteinaceous modifier that can be covalently linked to specific target proteins, affecting their activity, localization, interactions, and half-life. This project focuses on the SUMO Stress Response (SSR), the rapid increase of protein sumoylation after cells experience acute proteotoxic stress. The SSR is believed to play a cyto- protective role for normal cells, but it may also enhances the robustness of cancerous cells and some eukaryotic pathogens. Stress-induced sumoylation has profound effects on transcriptional reprogramming and protein complex integrity in the nucleus. However, there is little or no knowledge how the SSR affects cytoplasmic processes including cytoskeletal rearrangements, mitochondrial inheritance, vesicle sorting, and translation. Here we use the genetically tractable yeast Sacharomyces cerevisiae to address our hypothesis that cross-talk between protein sumoylation and ubiquitination in the cytoplasm plays a central role in cytoprotective effects initiated by dynamic stress-induced sumoylation. The specific aims of this project are 1) to use cell biological and genetic approaches, and an innovative yeast SUMO Stress Reporter strain, to dissect the choreography of the SSR. Specifically, to investigate evidence of stress-induced cooperativity of the SUMO E3 ligase Siz1 and the NEDD4/Rsp5 E3 ubiquitin ligase in the cytoplasm that may exert stress-induced control over cytoskeleton organization, mitochondrial inheritance, vesicle sorting, and translation. 2) To analyze a group of potential cytoplasmic SSR effector proteins we identified and to examine the functional consequences of genetic defects that result in their dysfunction. 3) To use innovative methods to identify variant SUMO pathway components that promote stress tolerance with the goal to ultimately test clinically-relevant alleles of SUMO pathway genes that may affect stress tolerance and the likelihood of cancer development. Our project is well-aligned with AREA program goals and will expose undergraduate students to meritorious research that is biomedically relevant.