Project description:microarray experiment to test the gene expression in long term lines of mutator and non-mutator yeast. Here we use an experimental evolution approach to investigate the conditions required for evolution of a reduction in mutation rate and the mechanisms by which populations tolerate the accumulation of deleterious mutations. We find that after ~6700 generations four out of eight experimental mutator lines had evolved a decreased mutation rate.
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.
Project description:Aneuploidy, the state in which an organism’s genome contains one or more missing or additional chromosomes, often causes widespread genotypic and phenotypic effects. Most often, aneuploidies are deleterious; the most common examples in humans being Down’s syndrome (Trisomy 21) and Turner’s syndrome (monosomy X). However, aneuploidy is surprisingly common in wild yeast populations. In recent years, there has been debate as to whether yeast contain an innate dosage compensation response on the whole-genome level, or if these natural isolates are robust to aneuploidy without such a mechanism. In this study, we tested for differential gene expression in 20 aneuploid and 18 euploid lines of yeast from two previous mutation accumulation experiments, where selection was low and therefore aneuploidies arose spontaneously. We found no evidence for whole-chromosome dosage compensation in aneuploid yeast but did find some evidence for attenuation of expression on a gene-by-gene basis. We additionally found that aneuploidy has no effect on the expression of the rest of the genome (i.e. “trans” genes), and that very few mutually exclusive aneuploid lines shared differentially expressed genes. However, we found a small common differential expression response in the euploid lines, suggesting an effect of mutation accumulation on gene expression. Our findings contribute to our understanding of aneuploidy in yeast and support the hypothesis that there is no innate dosage compensation mechanism at the whole-chromosome level.
Project description:Yeast is a powerful model system for studying the action of small molecule therapeutics. An important limitation has been low efficacy of many small molecules in yeast due to limited intracellular drug accumulation. We used the DNA binding domain of the pleiotropic drug resistance regulator Pdr1 fused in-frame to transcription repressors to repress Pdr1 regulated genes. Expression of these regulators conferred dominant enhancement of drug sensitivity and led to greatly diminished levels of Pdr1p regulated transcripts, including the yeast p-glycoprotein homologue Pdr5. Enhanced sensitivity was seen for a wide range of small molecules. Biochemical measurements demonstrated enhanced accumulation of rhodamine in yeast cells carrying the chimeras. These repressors of Pdr1p regulated transcripts can be introduced into large collections of strains such as the S. cerevisiae deletion set, and enhance the utility of yeast for studying drug action and for mechanism-based drug discovery. Keywords: Comparison of genetic variants