Differential protein expression in new1 knock-out yeast
Ontology highlight
ABSTRACT: A label-free quantitative proteomics experiment was performed to study the impact of new1 knock-out on differential protein expression in S. cerevisiae (baker’s yeast).
Project description:The pattern of gene transcription in Saccharomyces cerevisiae is strongly affected by the presence of glucose. An increased activity of protein kinase A (PKA), triggered by a rise in the intracellular concentration of cAMP, can account for many of the effects of glucose on transcription. To investigate the requirement of PKA for glucose control of gene expression, we have analyzed global transcription in strains devoid of PKA activity. In S. cerevisiae three genes, TPK1, TPK2, TPK3, encode catalytic subunits of PKA and the triple mutant tpk1 tpk2 tpk3 is unviable. We have worked, therefore, with two strains, tpk1 tpk2 tpk3 yak1 and tpk1 tpk2 tpk3 msn2 msn4, that bear suppressor mutations,. We have identified different classes of genes that can be induced, or repressed, by glucose in the absence of PKA. Among these genes, some are also controlled by a redundant signalling pathway involving PKA activation, while others do not respond to an increase in cAMP concentration. On the other hand, among genes which do not respond to glucose in the absence of PKA, some show a full response to increased cAMP levels, even in the absence of glucose, while others appear to require the cooperation of different signalling pathways. The goal of the present study was to investigate the occurrence of PKA-independent glucose signalling in S. cerevisiae. To this end, we have used global transcription analysis to study the effects of glucose on yeast strains completely devoid of PKA activity. In S. cerevisiae three genes TPK1, TPK2,and TPK3 encode catalytic subunits of PKA. While strains expressing only one of these genes grow normally, a triple null mutant (tpk1 tpk2 tpk3) is not viable (Toda et al 1987). Identification of different mutations able to suppress the growth defect of the triple mutant (Garrett and Broach 1989, Reinders et al 1998, Smith et al 1998) has allowed to determine what is the crucial function of PKA. As shown in Fig.1, PKA is needed to counteract the negative effect of the protein kinase Yak1 on yeast growth (Hartley et al 1994, Moriya et al 2001). In the presence of PKA the protein kinase Rim15 (Reinders et al 1998) and the transcription factors Msn2 and Msn4 (Görner et al 1998) can be phosphorylated and exported to the cytoplasm, transcription of the YAK1 gene, which is activated by Msn2/Msn4 (Smith et al 1998), is reduced, Yak1 levels remain low and growth is not hindered. In the absence of PKA, Rim15 remains in the nucleus where it can activate Msn2/Msn4 (Cameroni et al 2004) that turn on YAK1 transcription, thus blocking growth. This explains why strains lacking Rim15, Msn2/Msn4 or Yak1 no longer require PKA for growth. In this work we have used two isogenic strains lacking PKA and carrying the suppressor mutations msn2 msn4 or yak1. Two different suppressor mutants were used with the aim to enable a dissection of effects of the lack of PKA and effects of the suppressor mutations themselves.
Project description:Data was pre-processed array-wise using expresso (R/Bioconductor) with the RMA background correction method. We created our own probe annotation environment (cdf), which excludes probes in probesets that show cross-hybridization between Sc and Sp. 8708 annotated Sc probes and 13,317 annotated Sp probes out of a total of 120,855 probes showed cross-hybridization when a conservative intensity cut-off of 4.5 (log intensity values after preprocessing) was used. Cross-hybridizing probes were excluded from further analysis. This included 16 whole probe sets. Note that the standard GC-RMA method is not suitable for our purposes, since its bias model cannot handle bimodal intensity distributions, as caused by the simultaneous hybridization of Sc and Sp transcripts with global differences in RNA abundance. Labeling bias estimation and correction was done as described (Miller et al. 2011). Between-array normalization of arrays containing mixed Sc and Sp total RNA was done by proportional rescaling, such that the median Sp gene expression level was 1. Accordingly, between-array normalization of arrays containing mixed Sc and Sp labeled RNA was done by proportionally scaling the array to a median labeled Sp gene expression level of c. The constant c scales the median half-life of all experiments. We calibrated c in a way that the resulting median Sc wild-type mRNA half-life equaled that observed previously (Miller et al. 2011). Now, all Sc RNA levels, no matter if total or labeled, no matter from which experiment, can be compared on an absolute level. Decay rates and synthesis rates were obtained as described (Miller et al. 2011). The whole analysis workflow has been carried out using the open source R/Bioconductor package DTA
Project description:To better understand the pathophysiology of galactose-1-phosphate uridyltransferase (GALT) deficiency in humans, we studied the mechanisms by which a GALT-deficient yeast survived on galactose medium. Under normal conditions, GALT-deficient yeast cannot grow in medium that contains 0.2% galactose as the sole carbohydrate, a phenotype of Gal(-). We isolated revertants from a GALT-deficient yeast by direct selection for growth in galactose, a phenotype of Gal(+). Comparison of gene expression profiles among wild-type and revertant strains on galactose medium revealed that the revertant down-regulated genes encoding enzymes including galactokinase, galactose permease, and UDP-galactose-4-epimerase (the GAL regulon). By contrast, the revertant strain up-regulated the gene for UDP-glucose pyrophosphorylase, UGP1. There was reduced accumulation of galactose-1-phosphate in the galactose-grown revertant cells when compared to the GALT-deficient parent cells.
Project description:Protein aggregation is the abnormal association of misfolded proteins into larger, often insoluble structures that can be toxic during ageing and in protein aggregation-associated diseases. This RNA-seq study in Saccharomyces cerevisiae investigated the role of Tsa1, which is a member of the highly conserved 2-Cys peroxiredoxin (Prx) enzyme family, on protein aggregation.
Project description:The nonrandom distribution of meiotic recombination shapes patterns of inheritance and genome evolution, but chromosomal features governing this distribution are poorly understood. Formation of the DNA double-strand breaks (DSBs) that initiate recombination results in accumulation of Spo11 protein covalently bound to small DNA fragments. We show here that sequencing these fragments provides a genome-wide DSB map of unprecedented resolution and sensitivity. We use this map to explore the influence of large-scale chromosome structures, chromatin, transcription factors, and local sequence composition on DSB distributions. Our analysis supports the view that the recombination terrain is molded by combinatorial and hierarchical interaction of factors that work on widely different size scales. Mechanistic aspects of DSB formation and early processing steps are also uncovered. This map illuminates the occurrence of DSBs in repetitive DNA elements, repair of which can lead to chromosomal rearrangements. We discuss implications for evolutionary dynamics of recombination hotspots. We deep sequenced 4 samples of Spo11 oligos on Roche 454 platform. Three samples are technical replicates of Spo11 oligo products prepared from one meiotic culture and the fourth sample was prepared from an independent culture.
Project description:We assess the prevalence of polygenic evolution in pathways between the yeasts S. cerevisiae and S. bayanus. We first established short-read sequencing methods to detect cis-regulatory variation in a diploid hybrid between the species. We then formulated an analytic strategy to test for the scenario in which selective pressure in one species, to increase or decrease the activity of a pathway, has driven the accumulation of cis-regulatory variants that act in the same direction on gene expression. Application of this test revealed a variety of yeast pathways with evidence for directional regulatory evolution. Measurement of allele-specific expression of each ortholog in a diploid hybrid between Saccharomyces species
Project description:Effect of gene-length modification on Nucleosome periodicity in G1 synchronized cells, treated or untreated with 10-phenanthroline.
Project description:Mitochondrial DNA (mtDNA) in budding yeast is biparentally inherited, but colonies rapidly lose one type of parental mtDNA, becoming homoplasmic. Therefore, hybrids between different yeast species possess two homologous nuclear genomes, but only one type of mitochondrial DNA. We hypothesise that the choice of mtDNA retention is influenced by its contribution to hybrid fitness in different environments, and that the allelic expression of the two nuclear sub-genomes is affected by the presence of different mtDNAs in hybrids. Here, we crossed Saccharomyces cerevisiae with S. uvarum under different environmental conditions and examined the plasticity of the retention of mtDNA in each hybrid.
Project description:In Saccharomyces cerevisiae, a single double-strand break (DSB) triggers extensive phosphorylation of histone H2A (known as gammaH2AX) over 50 kb on either side of the DSB. This modification is carried out by either of yeastM-^Rs checkpoint kinases, the ATM homolog, Tel1, or the ATR homolog, Mec1. In G1-arrested cells, where there is very little 5M-^R to 3M-^R processing of DSB ends, only Tel1 promotes this modification. We have recently described a second modification gammaH2B - the phosphorylation of the C terminal T129 locus of histone H2B which is also carried out by both Mec1 and Tel1 kinases. To understand in detail how gamma-H2AX and gamma-H2B spread along the chromosome from a DSB we have undertaken a high-density analysis of their occupancy where there is a DSB on three different chromosomes. gamma-H2AX and gamma-H2B modifications are similar, but there is a marked absence of gamma-H2B near telomeres. We find that there is reduced gamma-H2AX and gamma-H2B modification over strongly transcribed regions, even taking into account the reduced histone occupancy of these genes. When transcription of the galactose-regulated genes GAL1, GAL10, GAL7 are turned off by the addition of glucose, gamma-H2AX is restored within 5 min; when these genes are again induced, gamma-H2AX is rapidly lost. Regions more distal to the GAL genes have markedly reduced gamma-H2AX levels that rise rapidly when transcription is repressed, suggesting that transcription acts as a barrier to the propagation of gamma-H2AX away from the DSB. The restoration of gamma-H2AX in transcribed regions can be carried out by either Mec1 or Tel1, even 7 h after break induction, suggesting that Tel1 remains associated with damaged chromosomes for an extended time. In addition, we show that gamma-H2AX can be transferred in trans, to regions unlinked to the DSB that lie in close proximity the DSB. Specifically, if a DSB is generated 14 kb from CEN2, gamma-H2AX is transferred to regions around all the other centromeres, in keeping with observed close proximity of all centromere-adjacent chromosome arms. This transfer can be observed even in the absence of formaldehyde crosslinking of the samples.
Project description:Global restriction of protein synthesis is a hallmark of cellular stress. Using hydrogen peroxide, we monitor the transcript level and also the translation status for each RNA using cycloheximide to freeze elongating ribosomes. Polyribosome fractionation of cell extracts was used to separate highly translated and poorly translated mRNAs that were then separately analysed.