The scientific goals of this application are to 1- understand signaling interactions connecting myosin II functions in cytokinesis, cell wall biogenesis, and cell growth 2- understand the relation between myosin II function and cell wall integrity and 3- identify new potential targets for antifungal drugs. We will accomplish this by identifying what metabolic processes are affected by the interruption of cytokinesis by actomyosindependent and actomyosin-independent mutations, what signaling pathways are necessary for cell survival under these conditions, and the biochemical components linking these pathways in these genetic mutants. Myosin ll-deficient Saccharomyces cerevisiae cells (myolA) exhibit multiple phenotypes with characteristics of both cytokinesis and cell wall mutants. To determine if these phenotypes were related to changes in gene expression, we determined the global transcription profile of myol A strains. These studies corroborated that the PKC1-dependent signaling pathway coordinately activates the transcription of cell wall stress genes in these strains. Coordinated down-regulation of ribosomal protein genes also occurs and it was observed that over expression of ribosomal protein genes RPL30 and RPS31 partially restored cell wall function in a myol A strain. Our main hypothesis is that transcriptional activation of cell wall stress genes and the down-regulation of ribosomal protein genes in myol A strains represent separate phenotypes for cell wall and cytokinesis mutants, respectively;each employing distinct essential signaling pathways that are interconnected. To test this hypothesis our specific aims are to: 1- conduct mRNA transcription analysis of the cytokinesis mutant chs2A and the cell wall mutant fksl A for subsequent comparison with myolA strains, 2-conduct analysis of mRNA translational regulation in cytokinesis mutants, 3- determine the status of the PKC1, TOR1, and TOR2 signaling pathways in cytokinesis mutant strains and test their requirement for cell viability, and 4- identify common regulators of the PKC1 and TOR signaling pathways in cytokinesis and cell wall mutants. The significance of this study lies in the discovery of new regulatory connections that coordinate actomyosin function and cell wall biogenesis in fungal cells. The proposed study will also increase our understanding about how loss of myosin II contributes to the stress response in yeast cells. Knowledge of the interaction between myosin II and stress signaling can lead to identification of potential targets for new antifungal drugs.
