Calorie restriction increases life span in many organisms, including the budding yeast Saccharomyces cerevisiae. From a large-scale analysis of 564 single-gene-deletion strains of yeast, we identified 10 gene deletions that increase replicative life span. Six of these correspond to genes encoding components of the nutrient-responsive TOR and Sch9 pathways. Calorie restriction of tor1D or sch9D cells failed to further increase life span and, like calorie restriction, deletion of either SCH9 or TOR1 increased life span independent of the Sir2 histone deacetylase. We propose that the TOR and Sch9 kinases define a primary conduit through which excess nutrient intake limits longevity in yeast.

Calorie restriction slows aging and increases life span in many organisms. In yeast, a mechanistic explanation has been proposed whereby calorie restriction slows aging by activating Sir2. Here we report the identification of a Sir2-independent pathway responsible for a majority of the longevity benefit associated with calorie restriction. Deletion of FOB1 and overexpression of SIR2 have been previously found to increase life span by reducing the levels of toxic rDNA circles in aged mother cells. We find that combining calorie restriction with either of these genetic interventions dramatically enhances longevity, resulting in the longest-lived yeast strain reported thus far. Further, calorie restriction results in a greater life span extension in cells lacking both Sir2 and Fob1 than in cells where Sir2 is present. These findings indicate that Sir2 and calorie restriction act in parallel pathways to promote longevity in yeast and, perhaps, higher eukaryotes.

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Common methods to identify yeast cells containing the prion form of the