| Signaling pathways respond to environmental cues by initiating a signal transduction cascade that changes the proteomic and transcriptional profile of the cell to make optimum use of available resources. To understand how mutations in signaling pathways affect cellular processes and to design effective drugs to treat diseases while minimizing harmful side effects, it is important to understand how the protein functions in a signaling network. In this study, we have used the budding yeast, Saccharomyces cerevisiae, as a model system, to establish the use of genomic tools to dissect signaling networks, specifically, the glucose signaling network.; S. cerevisiae uses glucose as the primary source of carbon for growth and cell division. Many components of the glucose signaling pathways have been identified. To dissect out how each of the glucose signaling pathways mediate gene expression changes in response to glucose addition, we have made used of in/activating mutations that can be selectively regulated and followed gene expression changes following in/activation of specific pathways. Our studies have shown that the Ras/PKA pathway mediates most of the glucose dependent gene expression changes in yeast. The Sch9 pathway works in parallel to Ras/PKA to induce changes in gene expression in response to glucose. However, Ras/PKA and Sch9 pathways contribute differentially to gene expression with Ras/PKA playing the primary role during growth in glucose. Gpr1-Gpa2 pathway also functions in parallel to Ras/PKA to affect a relatively reduced level of induction/repression in a subset of glucose regulated genes. Finally, we have shown that selective inhibition of the Snf1 pathway effects the expression of a few genes involved in carboxylic acid metabolism and fatty acid oxidation. Clustering and motif analysis of the gene expression dataset lead to the identification of novel motifs and the results from the functional studies on the motifs will be presented. Data will also be presented on a novel role of GPR1 and SCH9 in ergosterol gene regulation.; In chapter 3, we present studies on identification of targets of a glucose regulated transcription factor, Mig1. We were unsuccessful in identifying Migl targets. The insight from these studies will be discussed. |
