Project description:A crucial step towards understanding the mechanisms underlying aging is to obtain an integrated account of the molecular changes during aging. To address this, we mapped the yeast (S. cerevisiae) transcriptome during the replicative lifespan of budding yeast using novel culture and computational methods.
Project description:Protein synthesis is strictly regulated during replicative aging in yeast, but global translational regulation during replicative aging is poorly characterized. To conduct ribosomal profiling during replicative aging, we collected a large number of dividing aged cells using a miniature chemostat aging device. Translational efficiency, defined as the number of ribosome footprints normalized to transcript abundance, was compared between young and aged cells for each gene. We identified more than 700 genes with changes greater than twofold during replicative aging. Increased translational efficiency was observed in genes involved in DNA repair and chromosome organization. Decreased translational efficiency was observed in genes encoding ribosome components, transposon Ty1 and Ty2 genes, transcription factor HAC1 genes associated with the unfolded protein response, genes involved in cell wall synthesis and assembly, and ammonium permease genes. Our results provide a global view of translational regulation during replicative aging, in which the pathways involved in various cell functions are translationally regulated and cause diverse phenotypic changes.
Project description:Here we show that an unrestricted galactose diet in early life minimises pathology during replicative ageing in budding yeast, irrespective of diet later in life. Lifespan and average mother cell division rate are comparable between glucose and galactose diets, but markers of senescence and the progressive dysregulation of gene expression observed on glucose are minimal on galactose, showing these to be facets of ageing pathology rather than intrinsic parts of the replicative ageing process. Respiration on galactose is critical for minimising ageing pathology, and forced respiration during ageing on glucose by over-expression of Hap4 also has the same effect though only in a fraction of cells. This fraction maintains Hap4 activity to advanced age with low senescence and a youthful gene expression profile, whereas other cells in the same population that lose Hap4 activity undergo dramatic dysregulation of gene expression and accumulate aneuploid fragments of chromosome XII aneuploidy (ChrXIIr), which are tightly associated with ageing pathology.
Project description:Here we analyzed the widespread disruption of gene expression that accompanies yeast ageing, and surprisingly observed that this is completely independent of ERCs. Furthermore, we could not find subsets of genes that are differentially regulated in the presence of ERCs. High throughput imaging showed that the accumulation of Tom70-GFP which accompanies the onset of cell division defects at the Senescence Entry Point (SEP) also correlated poorly to ERC abundance, but allowed determination of a gene expression signature for the SEP. This signature included overexpression of mRNA from the chromosome XII region between the rDNA and the telomere (ChrXIIr), which has been previously noted to amplify during ageing.
Project description:Here we analysed the widespread disruption of gene expression that accompanies yeast ageing, and surprisingly observed that this is completely independent of ERCs. Furthermore, we could not find subsets of genes that are differentially regulated in the presence of ERCs. High throughput imaging showed that the accumulation of Tom70-GFP which accompanies the onset of cell division defects at the Senescence Entry Point (SEP) also correlated poorly to ERC abundance, but allowed determination of a gene expression signature for the SEP. This signature included overexpression of mRNA from the chromosome XII region between the rDNA and the telomere (ChrXIIr), which has been previously noted to amplify during ageing.
Project description:Here we analysed the widespread disruption of gene expression that accompanies yeast ageing, and surprisingly observed that this is completely independent of ERCs. Furthermore, we could not find subsets of genes that are differentially regulated in the presence of ERCs. High throughput imaging showed that the accumulation of Tom70-GFP which accompanies the onset of cell division defects at the Senescence Entry Point (SEP) also correlated poorly to ERC abundance, but allowed determination of a gene expression signature for the SEP. This signature included overexpression of mRNA from the chromosome XII region between the rDNA and the telomere (ChrXIIr), which has been previously noted to amplify during ageing.
Project description:All eukaryotic cells divide a finite number of times, termed replicative aging, but the reason for this is not clear. Consistent with the decreased total histone protein levels in aged Saccharomyces cerevisiae, which is a cause of aging (1), we find that nucleosome occupancy decreases 50% across the whole genome during replicative aging by spike-in controlled MNase sequencing. Nucleosomes become fuzzier or move to sequences predicted to better accommodate histone octamers. All yeast genes are induced during aging. Genes that are repressed in young cells are most induced, accompanied by nucleosome loss from their promoters that have unique chromatin organization. Contrary to the loss of mitochondrial function during aging, mitochondrial DNA content increases and unprecedented levels of large-scale chromosomal alterations and increased retrotransposition are observed. Mnase-Seq experiments were carried out for young yeast, old yeast, and old yeast with histone over expression, 3 replicates were done for each category. RNA-Seq were carried out for the same categories of yeast cells but with 2 replicates for each. Genome-Seq were done for the young and old yeast with 2 replicates for each.