ETP1/YHL010c is a novel gene needed for the adaptation of Saccharomyces cerevisiae to ethanol.

Saccharomyces cerevisiae has the ability to use a variety of different carbon sources to support its growth. Abundant fermentable sugars such as glucose and fructose are metabolized to ethanol that accumulates in the environment. Upon glucose depletion, nonfermentable carbon sources, such as ethanol and glycerol, are sufficient to support growth. However, high ethanol concentrations inhibit yeast growth and can become toxic to the cell. Here we show that YHL010c, a previously uncharacterized gene of S. cerevisiae, is needed by the yeast to adapt to ethanol, either as a sole carbon source or as a stressor. We named the gene ETP1 (Ethanol Tolerance Protein 1) and show that the etp1Delta strain has a growth defect in the presence of ethanol, ETP1 is needed for the ethanol-induced transcriptional activation of the ENA1 promoter and heat shock protein genes (HSP12 and HSP26), and plays a role in ethanol-induced turnover of the low-affinity hexose transporter Hxt3p. In addition, the hypersensitivity of etp1Delta to ethanol stress is partly due to the inability of the mutant to control the level of the cation/H(+) antiporter Nha1p in the cell.

Nsf1/Ypl230w participates in transcriptional activation during non-fermentative growth and in response to salt stress in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, fermentable carbon sources such as glucose and fructose are preferred and elicit glucose repression of genes needed to metabolize non-fermentable carbon sources such as glycerol, ethanol and acetate. Different sets of transcription factors are needed to adjust to specific carbon conditions. For example, Mig1 and Mig2 repress the transcription of gluconeogenic and respiratory genes in the presence of abundant glucose, while the transcriptional activation of these genes depends on transcription factors such as Adr1 and Cat8. Here we show that Ypl230w, which we renamed to Nsf1 (nutrient and stress factor 1), is expressed and localizes to the nucleus under non-fermentable carbon conditions to activate gene transcription. Specifically, the transcriptional activation of ACS1, CIT2 and IDH1 is shown to be partially dependent on intact NSF1. Similarly, the transcriptional activation of ENA1 is impaired in the nsf1Delta mutant in response to high concentrations of NaCl, implying that NSF1 is also needed for the yeast response to sodium stress. The carbon- and NaCl-mediated transcriptional activation of ENA1 is dependent on Nsf1. This finding implies that the yeast response to non-fermentable carbon and salt stress is at least partially dependent on NSF1.