Dynamical remodeling of the transcriptome during short-term anaerobiosis in Saccharomyces cerevisiae: differential response and role of Msn2 and/or Msn4 and other factors in galactose and glucose media.
ABSTRACT: In contrast to previous steady-state analyses of the O(2)-responsive transcriptome, here we examined the dynamics of the response to short-term anaerobiosis (2 generations) in both catabolite-repressed (glucose) and derepressed (galactose) cells, assessed the specific role that Msn2 and Msn4 play in mediating the response, and identified gene networks using a novel clustering approach. Upon shifting cells to anaerobic conditions in galactose medium, there was an acute ( approximately 10 min) yet transient (<45 min) induction of Msn2- and/or Msn4-regulated genes associated with the remodeling of reserve energy and catabolic pathways during the switch from mixed respiro-fermentative to strictly fermentative growth. Concomitantly, MCB- and SCB-regulated networks associated with the G(1)/S transition of the cell cycle were transiently down-regulated along with rRNA processing genes containing PAC and RRPE motifs. Remarkably, none of these gene networks were differentially expressed when cells were shifted in glucose, suggesting that a metabolically derived signal arising from the abrupt cessation of respiration, rather than O(2) deprivation per se, elicits this "stress response." By approximately 0.2 generation of anaerobiosis in both media, more chronic, heme-dependent effects were observed, including the down-regulation of Hap1-regulated networks, derepression of Rox1-regulated networks, and activation of Upc2-regulated ones. Changes in these networks result in the functional remodeling of the cell wall, sterol and sphingolipid metabolism, and dissimilatory pathways required for long-term anaerobiosis. Overall, this study reveals that the acute withdrawal of oxygen can invoke a metabolic state-dependent "stress response" but that acclimatization to oxygen deprivation is a relatively slow process involving complex changes primarily in heme-regulated gene networks.
Project description:We conducted a comprehensive genomic analysis of the temporal response of yeast to anaerobiosis (six generations) and subsequent aerobic recovery ( approximately 2 generations) to reveal metabolic-state (galactose versus glucose)-dependent differences in gene network activity and function. Analysis of variance showed that far fewer genes responded (raw P value of <or=10(-8)) to the O(2) shifts in glucose (1,603 genes) than in galactose (2,388 genes). Gene network analysis reveals that this difference is due largely to the failure of "stress"-activated networks controlled by Msn2/4, Fhl1, MCB, SCB, PAC, and RRPE to transiently respond to the shift to anaerobiosis in glucose as they did in galactose. After approximately 1 generation of anaerobiosis, the response was similar in both media, beginning with the deactivation of Hap1 and Hap2/3/4/5 networks involved in mitochondrial functions and the concomitant derepression of Rox1-regulated networks for carbohydrate catabolism and redox regulation and ending (>or=2 generations) with the activation of Upc2- and Mot3-regulated networks involved in sterol and cell wall homeostasis. The response to reoxygenation was rapid (<5 min) and similar in both media, dominated by Yap1 networks involved in oxidative stress/redox regulation and the concomitant activation of heme-regulated ones. Our analyses revealed extensive networks of genes subject to combinatorial regulation by both heme-dependent (e.g., Hap1, Hap2/3/4/5, Rox1, Mot3, and Upc2) and heme-independent (e.g., Yap1, Skn7, and Puf3) factors under these conditions. We also uncover novel functions for several cis-regulatory sites and trans-acting factors and define functional regulons involved in the physiological acclimatization to changes in oxygen availability.
Project description:Transcriptional profiling of Saccharomyces cerevisiae cells comparing the W303-1A wildtype with the W303-1A double mutant for MSN2 and MSN4 during zinc deficient conditions Keywords: Genetic modification with zinc limitation Two condition experiment, W303-1A vs W303-1A delta MSN2, MSN4. Biological replicates: 2 wildtype, 2 knock-out, independently grown and harvested.
Project description:The yeast PP2A-Cdc55 Serine/Threonine phosphatase regulates transcription under certain conditions. It is required for full activation of the environmental stress response mediated by the transcription factors Msn2 and Msn4. PP2A-Cdc55 contributes to sustained nuclear accumulation of Msn2 and Msn4 and extended chromatin recruitment under stress conditions such as hyperosmolarity stress. Transcript profiles of Msn2 and Msn4 double mutants are similar to cdc55 and the corresponding triple mutants. This argues for a Msn2/4 specific function of PP2A-Cdc55. Time course of 10 20 and 30 minutes hyperosmolarity treated yeast cells of wild type (W303), msn2msn4, cdc55, msn2msn5cdc55 genetic background.
Project description:The yeast PP2A-Cdc55 Serine/Threonine phosphatase regulates transcription under certain conditions. It is required for full activation of the environmental stress response mediated by the transcription factors Msn2 and Msn4. PP2A-Cdc55 contributes to sustained nuclear accumulation of Msn2 and Msn4 and extended chromatin recruitment under stress conditions such as hyperosmolarity stress. Transcript profiles of Msn2 and Msn4 double mutants are similar to cdc55 and the corresponding triple mutants. This argues for a Msn2/4 specific function of PP2A-Cdc55. Time course of 0, 10 20 and 30 minutes hyperosmolarity treated yeast cells of msn2msn4 or msn2msn4cdc55 genetic background, both carrying plasmid pMsn2pMsn2DNES; reference hybridization: untreated W303 msn2msn4 pMsn2pMsn2DNES labelled with Cy3
Project description:We have identified Cdc55, a regulatory B subunit of protein phosphatase 2A (PP2A), as an essential activating factor for stress gene transcription in Saccharomyces cerevisiae. The presence of PP2A-Cdc55 is required for full activation of the environmental stress response mediated by the transcription factors Msn2 and Msn4. We show that PP2A-Cdc55 contributes to sustained nuclear accumulation of Msn2 and Msn4 during hyperosmolarity stress. PP2A-Cdc55 also enhances Msn2-dependent transactivation, required for extended chromatin recruitment of the transcription factor. We analyzed a possible direct regulatory role for PP2A-Cdc55 on the phosphorylation status of Msn2. Detailed mass spectrometric and genetic analysis of Msn2 showed that stress exposure causes immediate transient dephosphorylation of Msn2 which is not dependent on PP2A-Cdc55 activity. Furthermore, the Hog1 mitogen-activated protein kinase pathway activity is not influenced by PP2A-Cdc55. We therefore propose that the PP2A-Cdc55 phosphatase is not involved in cytosolic stress signal perception but is involved in a specific intranuclear mechanism to regulate Msn2 and Msn4 nuclear accumulation and chromatin association under stress conditions.
Project description:This SuperSeries is composed of the following subset Series: GSE38565: The yeast PP2A-CDC55 phosphatase regulates the transcriptional response to hyperosmolarity stress by regulating Msn2 and Msn4 [Time course 1] GSE42033: The yeast PP2A-CDC55 phosphatase regulates the transcriptional response to hyperosmolarity stress by regulating Msn2 and Msn4 [Time course 2] Refer to individual Series
Project description:Acute changes in environmental parameters (e.g., O2, pH, UV, osmolarity, nutrients, etc.) evoke a common transcriptomic response in yeast referred to as the "environmental stress response" (ESR) or "common environmental response" (CER). Why such a diverse array of insults should elicit a common transcriptional response remains enigmatic. Previous functional analyses of the networks involved have found that, in addition to up-regulating those for mitigating the specific stressor, the majority appear to be involved in balancing energetic supply and demand and modulating progression through the cell cycle. Here we compared functional and regulatory aspects of the stress responses elicited by the acute inhibition of respiration with antimycin A and oxygen deprivation under catabolite non-repressed (galactose) conditions.Gene network analyses of the transcriptomic responses revealed both treatments result in the transient (10 - 60 min) down-regulation of MBF- and SBF-regulated networks involved in the G1/S transition of the cell cycle as well as Fhl1 and PAC/RRPE-associated networks involved in energetically costly programs of ribosomal biogenesis and protein synthesis. Simultaneously, Msn2/4 networks involved in hexose import/dissimilation, reserve energy regulation, and autophagy were transiently up-regulated. Interestingly, when cells were treated with antimycin A well before experiencing anaerobiosis these networks subsequently failed to respond to oxygen deprivation. These results suggest the transient stress response is elicited by the acute inhibition of respiration and, we postulate, changes in cellular energetics and/or the instantaneous growth rate, not oxygen deprivation per se. After a considerable delay (> or = 1 generation) under anoxia, predictable changes in heme-regulated gene networks (e.g., Hap1, Hap2/3/4/5, Mot3, Rox1 and Upc2) were observed both in the presence and absence of antimycin A.This study not only differentiates between the gene networks that respond to respiratory inhibition and those that respond to oxygen deprivation but suggests the function of the ESR or CER is to balance energetic supply/demand and coordinate growth with the cell cycle, whether in response to perturbations that disrupt catabolic pathways or those that require rapidly up-regulating energetically costly programs for combating specific stressors.
Project description:Macroautophagy/autophagy is a starvation and stress-induced catabolic process critical for cellular homeostasis and adaptation. Several Atg proteins are involved in the formation of the autophagosome and subsequent degradation of cytoplasmic components, a process termed autophagy flux. Additionally, the expression of several Atg proteins, in particular Atg8, is modulated transcriptionally, yet the regulatory mechanisms involved remain poorly understood. Here we demonstrate that the AGC kinase Ypk1, target of the rapamycin-insensitive TORC2 signaling pathway, controls ATG8 expression by repressing the heterodimeric Zinc-finger transcription factors Msn2 and Msn4. We find that Msn2 and Msn4 promote ATG8 expression downstream of the histone deacetylase complex (HDAC) subunit Ume6, a previously identified negative regulator of ATG8 expression. Moreover, we demonstrate that TORC2-Ypk1 signaling is functionally linked to distinct mitochondrial respiratory complexes. Surprisingly, we find that autophagy flux during amino acid starvation is also dependent upon Msn2-Msn4 activity, revealing a broad role for these transcription factors in the autophagy response.
Project description:Exposure of Saccharomyces cerevisiae to alkaline pH represents a stress condition that generates a compensatory reaction. Here we examine a possible role of the protein kinase-A (PKA) pathway in this response. The phenotypic analysis reveals that mutations that activate the PKA pathway (ira1 ira2, bcy1) tend to cause sensitivity to alkaline pH, whereas its deactivation develops tolerance to this stress. We observe that alkalinization causes a transient decrease in cAMP, the main regulator of the pathway. Alkaline pH causes rapid nuclear localization of the PKA-regulated Msn2 transcription factor which, together with Msn4, mediates a general stress response by binding to STRE sequences in many promoters. Consequently, a synthetic STRE-LacZ reporter shows a rapid induction in response to alkaline stress. An msn2 msn4 mutant is sensitive to alkaline pH, and transcriptomic analysis reveals that after 10 minutes of alkaline stress, the expression of many induced genes (47%) depends, at least in part, on the presence of Msn2 and Msn4. Taken together, these results demonstrate that inhibition of the PKA pathway by alkaline pH represents a substantial part of the adaptive response to this kind of stress and that this response involves Msn2/Msn4-mediated gene remodeling. However, the relevance of attenuation of PKA in high pH tolerance is not restricted to regulation of Msn2 function. Eight samples were analyzed: WT and the MCY5278 mutant strain, lacking both Msn2 and Msn4, in the presence of 20 mM KOH (pH 8) and in the presence of 20 mM KCl (non-induced conditions) for 10 and 30 min of stress. 2 biological replicates were analyzed for each condition, and dye-swapping was carried out for each comparison of samples. We compared the expression profiles of: 1) WT +KOH vs. WT +KCl after 10 min 2) msn2 msn4 mutant +KOH vs. msn2 msn4 +KCl after 10 min 3)WT +KOH vs. WT +KCl after 30 min 4) msn2 msn4 mutant +KOH vs. msn2 msn4 +KCl after 30 min Total number of chips analyzed: 16.
Project description:The yeast PP2A-Cdc55 Serine/Threonine phosphatase regulates transcription under certain conditions. It is required for full activation of the environmental stress response mediated by the transcription factors Msn2 and Msn4. PP2A-Cdc55 contributes to sustained nuclear accumulation of Msn2 and Msn4 and extended chromatin recruitment under stress conditions such as hyperosmolarity stress. Transcript profiles of Msn2 and Msn4 double mutants are similar to cdc55 and the corresponding triple mutants. This argues for a Msn2/4 specific function of PP2A-Cdc55.