UC San Diego

Protein dynamics during cellular responses to extracellular stimuli has been widely studied to understand how cells respond to change. Here, we employ two distinct techniques to look at two separate aspects of cellular response in Saccharomyces cerevisiae. First, we use a transcriptomics and proteomics approach to examine the pheromone response of yeast, using RNA-sequencing and mass spectrometry, respectively. We find that in general, mRNA abundance is not sufficient as a predictor of protein levels during dynamic responses such as pheromone response, but by using a mass-action kinetics model, we can reconcile these discrepancies. Performing this experiment in both a lab strain and the clinical isolate, YJM145, allows us to further identify possible genes where post-transcriptional regulation is affected by polymorphisms, allowing possible mechanisms of post-transcriptional regulation to be further explored. Second, we used an extreme bulk segregant analysis approach to map alleles in wild yeast strains, L-1374 and YPS606, which cause a difference in molecular response during the yeast’s response to hyper-osmotic shock by tracking the protein, STL1p. We find that many alleles have transient effects on STL1p levels during the osmotic stress response, but only a few have an impact on the cellular state after adaptation to the new environment. In addition, we found that alleles in the wild strain affect STL1p levels in both directions, suggesting possible compensatory mutations. Most genes were not found to be in the known osmotic stress response pathway suggesting regulation mechanisms of STL1p that were previously unknown.