The budding yeast Saccharomyces cerevisiae has been used in the fermentation of various kinds of alcoholic beverages. But the effect of ethanol on the cell growth of this yeast is poorly understood. This study shows that the addition of ethanol causes a cell-cycle delay associated with a transient dispersion of F-actin cytoskeleton, resulting in an increase in cell size. We found that the tyrosine kinase Swe1, the negative regulator of Cdc28-Clb kinase, is related to the regulation of cell growth in the presence of ethanol. Indeed, the increase in cell size due to ethanol was partially abolished in the SWE1-deleted cells, and the amount of Swe1 protein increased transiently in the presence of ethanol. These results indicated that Swe1 is involved in cell size control in the presence of ethanol, and that a signal produced by ethanol causes a transient up-regulation of Swe1. Further we investigated comprehensively the ethanol-sensitive strains in the complete set of 4847 non-essential gene deletions and identified at least 256 genes that are important for cell growth in the presence of ethanol.

Summary: The nematode worm Caenorhabditis elegans provides a powerful system for elucidating how genetic, metabolic, nutritional, and environmental factors influence aging. The mechanistic target of rapamycin (mTOR) kinase is important in growth, disease, and aging and is present in the mTORC1 and mTORC2 complexes. In diverse eukaryotes, lifespan can be increased by inhibition of mTORC1, which transduces anabolic signals to stimulate protein synthesis and inhibit autophagy. Less is understood about mTORC2, which affects C. elegans lifespan in a complex manner that is influenced by the bacterial food source. mTORC2 regulates C. elegans growth, reproduction, and lipid metabolism by activating the SGK‐1 kinase, but current data on SGK‐1 and lifespan seem to be conflicting. Here, by analyzing the mTORC2 component Rictor (RICT‐1), we show that mTORC2 modulates longevity by activating SGK‐1 in two pathways that affect lifespan oppositely. RICT‐1/mTORC2 limits longevity by directing SGK‐1 to inhibit the stress‐response transcription factor SKN‐1/Nrf in the intestine. Signals produced by the bacterial food source determine how this pathway affects SKN‐1 and lifespan. In addition, RICT‐1/mTORC2 functions in neurons in an SGK‐1‐mediated pathway that increases lifespan at lower temperatures. RICT‐1/mTORC2 and SGK‐1 therefore oppose or accelerate aging depending upon the context in which they are active. Our findings reconcile data on SGK‐1 and aging, show that the bacterial microenvironment influences SKN‐1/Nrf, mTORC2 functions, and aging, and identify two longevity‐related mTORC2 functions that involve SGK‐regulated responses to environmental cues.

Identification of biologically active natural compounds that promote health and longevity and understanding how they act, will provide insights into aging and metabolism and strategies for developing agents that prevent chronic disease. The garlic-derived thioallyl compounds S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) have been shown to have multiple biological activities. Here we show that SAC and SAMC increase lifespan and stress resistance in Caenorhabditis elegans and reduce accumulation of reactive oxygen species (ROS). These compounds do not appear to activate DAF-16 (FOXO orthologue) or mimic dietary restriction (DR) effects, but selectively induce SKN-1 (Nrf1/2/3 orthologue) targets involved in oxidative stress defense. Interestingly, their treatments do not facilitate SKN-1 nuclear accumulation, but slightly increased intracellular SKN-1 levels. Our data also indicate that thioallyl structure and the number of sulfur atoms are important for SKN-1 target induction. Our results indicate that SAC and SAMC may serve as potential agents that slow aging.

To dissect the action mechanism of reveromycin A (RM-A), a G₁-specific inhibitor, aSaccharomyces cerevisiae dominant mutant specifically resistant to RM-A, was isolated from a strain in which the genes implicated in nonspecific multidrug resistance had been deleted. The mutant gene (YRR2–1) responsible for the resistance was identified as an allele of the ILS1 gene encoding tRNA^Ile synthetase (IleRS). The activity of IleRS, but not several other aminoacyl-tRNA synthetases examined in wild type cell extract, was highly sensitive to RM-A (IC₅₀ = 8 ng/ml). The IleRS activity of the YRR2–1 mutant was 4-fold more resistant to the inhibitor compared with that of wild type. The mutation IleRS^N660D, near the KMSKS consensus sequence commonly found in the class I aminoacyl transferases, was found to be responsible for RM-A resistance. Moreover, overexpression of theILS1 gene from a high-copy plasmid conferred RM-A resistance. These results indicated that IleRS is a target of RM-Ain vivo. A defect of the GCN2 gene led to decreased RM-A resistance. IleRS inhibition by RM-A led to transcriptional activation of the ILS1 gene viathe Gcn2-Gcn4 general amino acid control pathway, and this autoregulation seemed to contribute to RM-A resistance.