Stress-induced production, processing and stability of a seripauperin protein, Pau5p, in Saccharomyces cerevisiae.

PAU genes comprise the largest multiple gene family in Saccharomyces cerevisiae with 24 members whose sequence homology ranges from 82% to 100%. Although transcriptional regulation for some of the PAU genes has been reported, none of the Pau proteins has been characterized. We constructed yeast strains encoding a C-terminal tandem affinity purification-tagged Pau5 in the PAU5 locus to study Pau5 production and properties in vivo. Pau5 is highly induced by low temperature, low oxygen and wine fermentation conditions. It is unstable in cells grown under laboratory conditions and is temporarily stabilized by low oxygen, osmotic and ethanol stresses. Pau5 degradation is accompanied by an unknown modification with a gradual increase in molecular mass by 3 kDa. Furthermore, Pau5 is O-mannosylated mainly by Pmt1; mannosylation enhances stability of the protein. The mannosylated Pau5 is soluble whereas the nonmannosylated proform Pau5 is an integral membrane protein. Our findings suggest that the intracellular concentration of Pau5 is regulated by wine making stress both at transcriptional and posttranslational levels; Pau5 might play a role in adaptation of yeast cells during alcoholic fermentations.