Browsing by Author "Mager, Peter"
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- Osmostress response of the yeast SaccharomycesPublication . Mager, Peter; Varela, J.Exposure of yeast cells to high osmolarities leads to dehydration, collapse of ion gradients over the plasma membrane and decrease in cell viability. The response of yeast cells to high external osmolarities is designated osmostress response. It is likely that both osmoregulatory and general stress reactions are involved in this so far poorly understood process. Part of the response aims at raising the internal osmotic potential, i.e. the production of osmolytes such as glycerol, and exclusion of toxic solutes. In addition, heat-shock proteins and trehalose are synthesized, probably to protect cellular components and to facilitate repair and recovery. Recent analyses of osmosensitive yeast mutants strongly suggest the involvement of protein kinase-mediated signal-transduction pathways in the maintenance of the osmotic integrity of the cell. This has stimulated interesting hypotheses as to the actual osmosensing mechanism.
- Osmostress-induced changes in yeast gene expressionPublication . Varela, J.; Van Beekvelt, Catelijne; Planta, Rudi; Mager, PeterWhen Saccharomyces cerevisiae cells are exposed to high concentrations of NaCI, they show reduced viability, methionine uptake and protein biosynthesis. Cells can acquire tolerance against a severe salt shock (up to 1.4 M NaCI) by a previous treatment with 0.7 M NaCI, but not by a previous heat shock. Two-dimensional analysis of [3H]-leucine-labelled proteins from salt-shocked cells (0.7 M NaCt) revealed the elevated rate of synthesis of nine proteins, among which were the heat-shock proteins hsp12 and hsp26. Northern analysis using gene-specific probes confirmed the identity of the latter proteins and, in addition, demonstrated the induction of glycerol-3-phos-phate dehydrogenase gene expression. The synthesis of the same set of proteins is induced or enhanced upon exposure of cells to 0.8 M sucrose, although not as dramatically as in an iso-osmolar NaCI concentration (0.7 M).