An investigation of the role of the Vid30c in salt stress response in the yeast Saccharomyces cerevisiae

Maintaining intracellular ion homeostasis is crucial for cellular survival and function. In the yeast Saccharomyces cerevisiae, exposure to high NaCl concentrations results in an accumulation of Na+ ions intracellularly leading to a disruption in ion homeostasis. To combat this accumulation of Na+ ions the yeast activates the transcription of the gene ENA1 encoding a Na+-ATPase that extrudes Na+ ions from the cell. The protein Nha1p is also required to extrude Na+ ions out of the cell. Research presented in this thesis indicates that components of the Vid30c protein complex play an important role in the yeast's tolerance to NaCl stress with Vid28p playing a more central and dominant role. The VID28 and VID24 genes are required for growth during exposure to high concentrations of NaCl. Many components that are a part of or are linked to the Vid30c are required for the NaCl induced activation of the ENA1 promoter with Vid28p being of particular importance. Down-regulation of the ENA1 promoter in the vid28Delta mutant is due to improper activation of ENA1 transcription most likely through Crz1p. In addition, components of the Vid30c are also required to regulate the intracellular levels of Na+ and K+ ions during sodium stress, however this is unlikely due to the regulation of Nha1p. This thesis presents novel functions of components of the Vid30c that are required for the yeast to adapt to NaCl stress.