Proteomic And Transcriptomic Analyses Reveal Novel Aspects Of Post-Transcriptional Regulation In Saccharomyces cerevisiae

Abstract

Although gene expression begins with transcription, there are a variety of mechanisms that cells use to control and tune expression post-transcriptionally. Many post-transcriptional regulatory functions including translational regulation, transcript surveillance, intracellular RNA localization, and RNA decay occur in organelles known as RNA granules. RNA granules, such as processing (P)-bodies, are cytoplasmic accumulations of translationally repressed mRNA and associated proteins that are ubiquitous among eukaryotes. Much of what is known about RNA granule biology has been observed through genetic and cytological experimentation and very few biochemical enrichments of these structures have been reported. In this work I present an affinity enrichment strategy for Dhh1, a conserved core component of P-bodies, from the budding yeast <italic>Saccharomyces cerevisiae</italic>. We identify proteins co-enriching with Dhh1 using tandem mass spectrometry and show that many known RNA granule proteins are enriched by this approach. We go on to compare the association of proteins with the complex across two environmental conditions to examine the effect of stress induction on RNA granule assemblies. We find that metabolic enzymes and molecular chaperones are typically more abundant in the stress-induced P-body complex and demonstrate that one chaperone, YDJ1, is involved in the stress-induced aggregation of several P-body proteins into cytoplasmic foci. We also identify RNA co-enriching with Dhh1 and detect several classes of catalytic RNA as well as a strong enrichment for the mRNA encoding the P-body protein PAT1. Finally, I present and discuss the characterization of a yeast strain that exhibits sensitivity to the drug puromycin. The puromycin-sensitive strain incorporates the drug into nascent proteins <italic>in vivo</italic> and I discuss how this is a unique and useful approach for the detection of protein biosynthesis. The techniques developed and employed in this dissertation provide novel perspectives on post-transcriptional regulatory processes and enable further investigations into how these regulatory programs are executed within the cell.