Article Abstract:
The activation of trehalase, repression of CTT1 and SSA3, and induction of ribosomal protein genes in Saccharomyces cerevisiae is regulated by 2 glucose-dependent signalling pathways. Yeast cells, grown on a glucose-containing medium and starved of nitrogen, accumulate high trehalose levels. Rapid mobilization of trehalose occurs on readdition of nitrogen. This nitrogen-induced activation is dependent on the presence of fructose or glucose but independent of phosphorylation of the sugar as is the repression of CTT1 and SSA3 and upshift of ribosomal protein synthesis.
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Article Abstract:
Saccharomyces cerevisiae does not relay the signal indicating the presence of a high osmolarity environment, directly to the transcriptional mechanism but rather to a regulator of the mitogen-activated protein kinase (MAPK). Cascades of MAPK are utilized to signal different kinds of stress. These cascades may react to growth-related stimuli, such as nutrients or growth factors. There is an overlap between growth-related cellular mechanisms and response to stress. Protein kinase A is mainly involved in signal integration.
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Article Abstract:
Yeast cells respond to an elevation in osmolarity through the increase in the cellular content of the osmolyte glycerol. This reaction is accompanied by the stimulation of the expression of genes encoding enzymes in the glycerol production pathway. The osmotic induction of one of these genes, GPD1, which encodes glycerol-3-phosphate dehydrogenase, was studied. Findings showed that osmotic regulation of GPD1 expression is due to an interaction between various signalling pathways.
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