All cells were similarly sensitive to acetic acid-induced death, regardless of genotype, indicating that genetic Meth-R does not also confer acetic acid tolerance. Our data are therefore consistent with genetic Meth-R extending yeast chronological lifespan primarily by reducing acid accumulation. As methionine-restricted growth resulted in reduced acidification of yeast culture media, we hypothesized that Meth-R might alter the expression of factors involved in cellular metabolism. Because the so-called retrograde response pathway regulates nuclear gene expression in response to nutritional stress and mitochondrial dysfunction, we considered the possibility that this pathway might be upregulated in methionine-restricted cells. The key mediator of retrograde signaling is the translocation of the Rtg1/3 transcription factor complex to the nucleus, where it alters expression of a number of genes, enriched for factors involved in metabolism, chromatin remodeling and genome stability. Activation of retrograde signaling has been shown to extend the GSK J1 replicative lifespan of yeast mother cells. Furthermore, it is known that TOR signaling inhibits the retrograde response, and that inhibition of TOR extends both replicative and chronological lifespan. To explore putative connections between Meth-R and the retrograde response, we asked whether the altered transcriptional program of methionine restricted cells Nexturastat A required RTG3. Data from two published studies suggested to us a putative mechanism by which Meth-R might alter tRNA metabolism to promote longevity. First, a recent study in mice has shown that tRNA binds to cytochrome C and inhibits its ability to activate caspase. Second, activation of the retrograde response in yeast is induced by mitochondrial dysfunction, nutritional stress and defects in metabolism. As cytochrome C supports oxidative phosphorylation and functions in mitochondria, we were intrigued by the possibility that elevated tRNA levels in methionine-restricted yeast might inhibit some aspect of cytochrome C function, thereby activating the retrograde response.