title: Mutations of the TATA-binding protein confer enhanced tolerance to hyperosmotic stress in Saccharomyces cerevisiae.
abstract: Previously, it was shown that overexpression of either of two SPT15 mutant alleles, SPT15-M2 and SPT15-M3, which encode mutant TATA-binding proteins, confer enhanced ethanol tolerance in Saccharomyces cerevisiae. In this study, we demonstrated that strains overexpressing SPT15-M2 or SPT15-M3 were tolerant to hyperosmotic stress caused by high concentrations of glucose, salt, and sorbitol. The enhanced tolerance to high glucose concentrations in particular improved ethanol production from very high gravity (VHG) ethanol fermentations. The strains displayed constitutive and sustained activation of Hog1, a central kinase in the high osmolarity glycerol (HOG) signal transduction pathway of S. cerevisiae. However, the cell growth defect known to be caused by constitutive and sustained activation of Hog1 was not observed. We also found that reactive oxygen species (ROS) were accumulated to a less extent upon exposure to high glucose concentration in our osmotolerant strains. We identified six new genes (GPH1, HSP12, AIM17, SSA4, USV1, and IGD1), the individual deletion of which renders cells sensitive to 50 % glucose. In spite of the presence of multiple copies of stress response element in their promoters, it was apparent that those genes were not controlled at the transcriptional level by the HOG pathway under the high glucose conditions. Combined with previously published results, overexpression of SPT15-M2 or SPT15-M3 clearly provides a basis for improved tolerance to ethanol and osmotic stress, which enables construction of strains of any genetic background that need enhanced tolerance to high concentrations of ethanol and glucose, promoting the feasibility for VHG ethanol fermentation.
authors.affiliation: Department of Life Sciences, Ewha Womans University, Seoul, Republic of Korea.
authors.forename: Na-Rae
authors.initials: NR
authors.lastname: Kim
authors.forename: Jungwoo
authors.initials: J
authors.lastname: Yang
authors.forename: Hyeji
authors.initials: H
authors.lastname: Kwon
authors.forename: Jieun
authors.initials: J
authors.lastname: An
authors.forename: Wonja
authors.initials: W
authors.lastname: Choi
authors.forename: Wankee
authors.initials: W
authors.lastname: Kim
mesh_terms: D000483:Alleles; D000431:Ethanol / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D035181:TATA-Box Binding Protein / Q000235:genetics* / Q000378:metabolism*
chemical_list: C115017:SPT15 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035181:TATA-Box Binding Protein; D000431:Ethanol; D005947:Glucose; D005990:Glycerol