Project description:In Saccharomyces cerevisiae, deletion of genes encoding proteins of the large ribosomal subunit (RPLs) increases the replicative lifespan in a Gcn4-dependent manner. However, how Gcn4, a key transcriptional activator of amino acid biosynthesis genes, increases lifespan, is unknown. Here we show that Gcn4 acts as a repressor of protein synthesis. By analyzing the mRNA and protein abundance, the ribosome occupancy and protein synthesis rate in various yeast strains, we demonstrate that Gcn4 is sufficient to reduce protein synthesis and to increase yeast lifespan. Chromatin immunoprecipitation reveals Gcn4 binding not only at genes that are activated, but also at genes that are repressed upon Gcn4 overexpression. The promoters of repressed genes contain Rap1 binding motifs. Our data suggest that Gcn4 is a central regulator of protein synthesis under multiple perturbations - including ribosomal protein (RP) gene deletions, calorie restriction, rapamycin treatment - and provide an explanation for its role in longevity and stress response. This SuperSeries is composed of the SubSeries listed below.
Project description:In Saccharomyces cerevisiae, deletion of genes encoding proteins of the large ribosomal subunit (RPLs) increases the replicative lifespan in a Gcn4-dependent manner. However, how Gcn4, a key transcriptional activator of amino acid biosynthesis genes, increases lifespan, is unknown. Here we show that Gcn4 acts as a repressor of protein synthesis. By analyzing the mRNA and protein abundance, the ribosome occupancy and protein synthesis rate in various yeast strains, we demonstrate that Gcn4 is sufficient to reduce protein synthesis and to increase yeast lifespan. Chromatin immunoprecipitation reveals Gcn4 binding not only at genes that are activated, but also at genes that are repressed upon Gcn4 overexpression. The promoters of repressed genes contain Rap1 binding motifs. Our data suggest that Gcn4 is a central regulator of protein synthesis under multiple perturbations - including ribosomal protein (RP) gene deletions, calorie restriction, rapamycin treatment - and provide an explanation for its role in longevity and stress response.
Project description:In Saccharomyces cerevisiae, deletion of genes encoding proteins of the large ribosomal subunit (RPLs) increases the replicative lifespan in a Gcn4-dependent manner. However, how Gcn4, a key transcriptional activator of amino acid biosynthesis genes, increases lifespan, is unknown. Here we show that Gcn4 acts as a repressor of protein synthesis. By analyzing the mRNA and protein abundance, the ribosome occupancy and protein synthesis rate in various yeast strains, we demonstrate that Gcn4 is sufficient to reduce protein synthesis and to increase yeast lifespan. Chromatin immunoprecipitation reveals Gcn4 binding not only at genes that are activated, but also at genes that are repressed upon Gcn4 overexpression. The promoters of repressed genes contain Rap1 binding motifs. Our data suggest that Gcn4 is a central regulator of protein synthesis under multiple perturbations - including ribosomal protein (RP) gene deletions, calorie restriction, rapamycin treatment - and provide an explanation for its role in longevity and stress response.
Project description:We have shown that multiple tRNA synthetase inhibitors can increase lifespan in both the nematode C. elegans and the budding yeast S. cerevisiae by acting through the conserved transcription factor Gcn4 (yeast) / ATF-4 (worms). To further understand the biology downstream of this conserved transcription factor in the yeast model system, we looked at two different yeast models known to have both upregulated Gcn4, and GCN4-dependent increased replicative lifespan. These two models are rpl31aΔ yeast, and yeast treated with the tRNA synthetase inhibitor borrelidin. We used both proteomic and RNAseq analysis of a block experimental design that included both of these models, to identify GCN4-dependent changes in these two longlived strains of yeast. Proteomic analysis of these yeast indicate that the longlived yeast have increased abundance of proteins involved in amino acid biosynthesis. RNASeq of these same yeast uncovered further regulation of protein turnover, identifying the differential expression of genes associated with both autophagy and with the ubiquitin proteasome system. The data presented here further underscore the important role that GCN4 and its orthologs play in the maintenance of protein homeostasis, which is itself an important hallmark of aging. Importantly, these changes could also have wider-ranging implications in the understanding and treatment of diseases of aging characterized by protein aggregation.
Project description:Deletion of several ribosomal proteins genes (RPKOs) has been shown to extend the lifespan of Saccharomyces cerevisiae in a Gcn4-dependent manner. To characterize the underlying mechanisms, we systematically analyzed the gene expression of both short- and long-lived RPKO strains at multiple levels. We found that up-regulation of amino acid biosynthesis and global down-regulation of protein synthesis are hallmarks of long-lived strains. We provide direct evidence that gene expression changes observed in long-lived strains result from translational up-regulation of GCN4 mRNA via skipping of upstream open reading frames (uORFs), in turn due to slow/defective ribosome assembly. We further demonstrate that Gcn4 acts as a transcriptional repressor on promoters of translation-related genes, thereby globally reducing protein synthesis. Our data suggest that the Gcn4-dependent increase in lifespan can be attributed partially to its ability to dampen the translation capacity of the cell, thereby engaging a well known mechanism of longevity.
Project description:Using ribosome profiling, we find globally reduced translation efficiency during mitotic / replicative aging in budding yeast. Two mechanisms contribute to this: Firstly, the mRNA binding protein Ssd1 is induced during aging, sequestering mRNAs to P-bodies and stress granules that are abundant in old cells. Indeed, overexpression of Ssd1 reduced protein synthesis in young cells and extended lifespan, while loss of Ssd1 reduced the translational deficit of old cells and shortened lifespan. Secondly, the Gcn2 kinase is activated in old cells, phosphorylating and inactivating the translational initiation factor eIF2α. Accordingly, deletion of GCN2 reduced the translational defect of old cells. Furthermore, overexpressing an uncharged tRNA to fully activate Gcn2, or overexpression of its downstream mediator, Gcn4, extended replicative lifespan in a manner that was mostly dependent on autophagy without inhibiting the TOR pathway. As such, Ssd1 induction, activation of the integrated stress response or autophagy are favorable TOR-independent therapeutic targets for lifespan extension.
Project description:Investigation of whole genome gene expression changes at short (2 hours) and extended (24 hours) timepoints in wild-type Saccharomyces cerevisiae treated with 50 μM menadione during exponential growth compared to an rph1Δ strain Transient treatment with 50 μM menadione elevates mitochondrial ROS and extends chronological lifespan in yeast. Deletion of RPH1, a H3K36me3 histone demethylase, block chronological lifespan extension. This study aimed to identify Rph1p-dependent gene expression changes induced by menadione treatment that may support chronological lifespan extension. Reference: Bonawitz, N.D., Chatenay-Lapointe, M., Wearn, C.M., and Shadel, G.S. (2008). Expression of the rDNA-encoded mitochondrial protein Tar1p is stringently controlled and responds differentially to mitochondrial respiratory demand and dysfunction. Curr Genet 54, 83-94.
Project description:Aneuploidy and aging are correlated; however, a causal link between these two phenomena has remained elusive. Here we show that yeast disomic for a single native yeast chromosome generally have a decreased replicative lifespan. In addition, the extent of this lifespan deficit correlates with the size of the extra chromosome. We identified a mutation in BUL1 that rescues both the lifespan deficit and a protein trafficking defect in yeast disomic for chromosome 5. Bul1 is an E4 ubiquitin ligase adaptor involved in a protein quality-control pathway that targets membrane proteins for endocytosis and destruction in the lysosomal vacuole thereby maintaining protein homeostasis. Concurrent suppression of the aging and trafficking phenotypes suggests that disrupted membrane protein homeostasis in aneuploid yeast may contribute to their accelerated aging. The data reported here demonstrate that aneuploidy can impair protein homeostasis, shorten lifespan, and may contribute to age-associated phenotypes.