scholarly journals The HOG Pathway Dictates the Short-Term Translational Response after Hyperosmotic Shock

2010 ◽  
Vol 21 (17) ◽  
pp. 3080-3092 ◽  
Author(s):  
Jonas Warringer ◽  
Malin Hult ◽  
Sergi Regot ◽  
Francesc Posas ◽  
Per Sunnerhagen
Keyword(s):  
Translational Control ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Environmental Changes ◽  
Transcriptional Response ◽  
Fine Tuning ◽  
Yeast Cells ◽  
Adaptive Responses ◽  
Hog Pathway ◽  
Hyperosmotic Shock

Cellular responses to environmental changes occur on different levels. We investigated the translational response of yeast cells after mild hyperosmotic shock by isolating mRNA associated with multiple ribosomes (polysomes) followed by array analysis. Globally, recruitment of preexisting mRNAs to ribosomes (translational response) is faster than the transcriptional response. Specific functional groups of mRNAs are recruited to ribosomes without any corresponding increase in total mRNA. Among mRNAs under strong translational up-regulation upon shock, transcripts encoding membrane-bound proteins including hexose transporters were enriched. Similarly, numerous mRNAs encoding cytoplasmic ribosomal proteins run counter to the overall trend of down-regulation and are instead translationally mobilized late in the response. Surprisingly, certain transcriptionally induced mRNAs were excluded from ribosomal association after shock. Importantly, we verify, using constructs with intact 5′ and 3′ untranslated regions, that the observed changes in polysomal mRNA are reflected in protein levels, including cases with only translational up-regulation. Interestingly, the translational regulation of the most highly osmostress-regulated mRNAs was more strongly dependent on the stress-activated protein kinases Hog1 and Rck2 than the transcriptional regulation. Our results show the importance of translational control for fine tuning of the adaptive responses.

scholarly journals Cytosolic aspartate aminotransferase moonlights as a ribosome binding modulator of Gcn2 activity during oxidative stress

2021 ◽  
Author(s):  
Robert A. Crawford ◽  
Mark P. Ashe ◽  
Simon J. Hubbard ◽  
Graham D. Pavitt
Keyword(s):  
Oxidative Stress ◽  
Translational Control ◽  
Aspartate Aminotransferase ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Cellular Response ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Stress Sensitivity ◽  
Yeast Cells

AbstractRegulation of translation is a fundamental facet of the cellular response to rapidly changing external conditions. Specific RNA-binding proteins (RBPs) co-ordinate the translational regulation of distinct mRNA cohorts during stress. To identify RBPs with previously under-appreciated roles in translational control, we used polysome profiling and mass spectrometry to identify and quantify proteins associated with translating ribosomes in unstressed yeast cells and during oxidative stress and amino acid starvation, which both induce the integrated stress response (ISR). Over 800 proteins were identified across polysome gradient fractions, including ribosomal proteins, translation factors and many others without previously described translation-related roles, including numerous metabolic enzymes. We identified variations in patterns of polysome enrichment in both unstressed and stressed cells and identified proteins enriched in heavy polysomes during stress. Genetic screening of polysome-enriched RBPs identified the cytosolic aspartate aminotransferase, Aat2, as a ribosome-associated protein whose deletion conferred growth sensitivity to oxidative stress. Loss of Aat2 caused aberrantly high activation of the ISR via enhanced eIF2α phosphorylation and GCN4 activation. Importantly, non-catalytic AAT2 mutants retained polysome association and did not show heightened stress sensitivity. Aat2 therefore has a separate ribosome-associated translational regulatory or ‘moonlighting’ function that modulates the ISR independent of its aspartate aminotransferase activity.

scholarly journals Osmotic Stress Signaling and Osmoadaptation in Yeasts

2002 ◽  
Vol 66 (2) ◽  
pp. 300-372 ◽  
Author(s):  
Stefan Hohmann
Keyword(s):  
Cell Surface ◽  
Map Kinase ◽  
Surface Properties ◽  
Transcriptional Response ◽  
Yeast Cells ◽  
Hog Pathway ◽  
Cell Surface Properties ◽  
High Osmolarity ◽  
Map Kinase Cascade ◽  
Kinase Cascade

SUMMARY The ability to adapt to altered availability of free water is a fundamental property of living cells. The principles underlying osmoadaptation are well conserved. The yeast Saccharomyces cerevisiae is an excellent model system with which to study the molecular biology and physiology of osmoadaptation. Upon a shift to high osmolarity, yeast cells rapidly stimulate a mitogen-activated protein (MAP) kinase cascade, the high-osmolarity glycerol (HOG) pathway, which orchestrates part of the transcriptional response. The dynamic operation of the HOG pathway has been well studied, and similar osmosensing pathways exist in other eukaryotes. Protein kinase A, which seems to mediate a response to diverse stress conditions, is also involved in the transcriptional response program. Expression changes after a shift to high osmolarity aim at adjusting metabolism and the production of cellular protectants. Accumulation of the osmolyte glycerol, which is also controlled by altering transmembrane glycerol transport, is of central importance. Upon a shift from high to low osmolarity, yeast cells stimulate a different MAP kinase cascade, the cell integrity pathway. The transcriptional program upon hypo-osmotic shock seems to aim at adjusting cell surface properties. Rapid export of glycerol is an important event in adaptation to low osmolarity. Osmoadaptation, adjustment of cell surface properties, and the control of cell morphogenesis, growth, and proliferation are highly coordinated processes. The Skn7p response regulator may be involved in coordinating these events. An integrated understanding of osmoadaptation requires not only knowledge of the function of many uncharacterized genes but also further insight into the time line of events, their interdependence, their dynamics, and their spatial organization as well as the importance of subtle effects.

scholarly journals Novel Translational Control through an Iron-Responsive Element by Interaction of Multifunctional Protein YB-1 and IRP2

2002 ◽  
Vol 22 (18) ◽  
pp. 6375-6383 ◽  
Author(s):  
Megumi Ashizuka ◽  
Takao Fukuda ◽  
Takanori Nakamura ◽  
Kanemitsu Shirasuna ◽  
Kazuhiro Iwai ◽  
...  
Keyword(s):  
Translational Control ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Regulatory Protein ◽  
Direct Interaction ◽  
In Vitro Translation ◽  
High Concentration ◽  
Iron Responsive Element ◽  
Responsive Element

ABSTRACT The eukaryotic Y-box-binding protein YB-1 functions in various biological processes, including DNA repair, cell proliferation, and transcriptional and translational controls. To gain further insight into how human YB-1 plays its role in pleiotropic functions, we here used two-hybrid screenings to identify partners of this protein; the results showed that YB-1 itself, iron-regulatory protein 2 (IRP2), and five ribosomal proteins each served as partners to YB-1. We then examined the biological effect of the interaction of YB-1 and IRP2 on translational regulation. Both in vitro binding and coimmunoprecipitation assays showed the direct interaction of YB-1 and IRP2 in the presence of a high concentration of iron. RNA gel shift assays showed that YB-1 reduced the formation of the IRP2-mRNA complex when the iron-responsive element of the ferritin mRNA 5′ untranslated region (UTR) was used as a probe. By using an in vitro translation assay using luciferase mRNA ligated to the ferritin mRNA 5′UTR as a reporter construct, we showed that both YB-1 and IRP2 inhibited the translation of the mRNA. However, coadministration of YB-1 and IRP2 proteins abrogated the inhibition of protein synthesis by each protein. An In vivo coimmunoprecipitation assay showed that IRP2 bound to YB-1 in the presence of iron and a proteasome inhibitor. The direct interaction of YB-1 and IRP2 provides the first evidence of the involvement of YB-1 in the translational regulation of an iron-related protein.

scholarly journals Ribosomal protein S7 ubiquitination during ER stress in yeast is associated with selective mRNA translation and stress outcome

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yasuko Matsuki ◽  
Yoshitaka Matsuo ◽  
Yu Nakano ◽  
Shintaro Iwasaki ◽  
Hideyuki Yoko ◽  
...  
Keyword(s):  
Er Stress ◽  
Ribosomal Protein ◽  
Translational Control ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Mrna Translation ◽  
Ribosome Profiling ◽  
Independent Manner ◽  
Eif2α Phosphorylation ◽  
The Unfolded Protein Response

AbstracteIF2α phosphorylation-mediated translational regulation is crucial for global translation repression by various stresses, including the unfolded protein response (UPR). However, translational control during UPR has not been demonstrated in yeast. This study investigated ribosome ubiquitination-mediated translational controls during UPR. Tunicamycin-induced ER stress enhanced the levels of ubiquitination of the ribosomal proteins uS10, uS3 and eS7. Not4-mediated monoubiquitination of eS7A was required for resistance to tunicamycin, whereas E3 ligase Hel2-mediated ubiquitination of uS10 was not. Ribosome profiling showed that the monoubiquitination of eS7A was crucial for translational regulation, including the upregulation of the spliced form of HAC1 (HAC1i) mRNA and the downregulation of Histidine triad NucleoTide-binding 1 (HNT1) mRNA. Downregulation of the deubiquitinating enzyme complex Upb3-Bre5 increased the levels of ubiquitinated eS7A during UPR in an Ire1-independent manner. These findings suggest that the monoubiquitination of ribosomal protein eS7A plays a crucial role in translational controls during the ER stress response in yeast.

scholarly journals Genomic Expression Programs in the Response of Yeast Cells to Environmental Changes

2000 ◽  
Vol 11 (12) ◽  
pp. 4241-4257 ◽  
Author(s):  
Audrey P. Gasch ◽  
Paul T. Spellman ◽  
Camilla M. Kao ◽  
Orna Carmel-Harel ◽  
Michael B. Eisen ◽  
...  
Keyword(s):  
Dna Microarrays ◽  
Environmental Changes ◽  
Osmotic Shock ◽  
Expression Patterns ◽  
Transcriptional Response ◽  
Yeast Cells ◽  
Large Set ◽  
Genomic Expression ◽  
Sequence Elements ◽  
Almost All

We explored genomic expression patterns in the yeastSaccharomyces cerevisiae responding to diverse environmental transitions. DNA microarrays were used to measure changes in transcript levels over time for almost every yeast gene, as cells responded to temperature shocks, hydrogen peroxide, the superoxide-generating drug menadione, the sulfhydryl-oxidizing agent diamide, the disulfide-reducing agent dithiothreitol, hyper- and hypo-osmotic shock, amino acid starvation, nitrogen source depletion, and progression into stationary phase. A large set of genes (∼ 900) showed a similar drastic response to almost all of these environmental changes. Additional features of the genomic responses were specialized for specific conditions. Promoter analysis and subsequent characterization of the responses of mutant strains implicated the transcription factors Yap1p, as well as Msn2p and Msn4p, in mediating specific features of the transcriptional response, while the identification of novel sequence elements provided clues to novel regulators. Physiological themes in the genomic responses to specific environmental stresses provided insights into the effects of those stresses on the cell.

scholarly journals Ribosomal protein S7 ubiquitination during ER stress in yeast is associated with selective mRNA translation and stress outcome

2020 ◽  
Author(s):  
Yasuko Matsuki ◽  
Yoshitaka Matsuo ◽  
Yu Nakano ◽  
Shintaro Iwasaki ◽  
Hideyuki Yoko ◽  
...  
Keyword(s):  
Er Stress ◽  
Ribosomal Protein ◽  
Translational Control ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Mrna Translation ◽  
Ribosome Profiling ◽  
Independent Manner ◽  
Eif2α Phosphorylation ◽  
The Unfolded Protein Response

ABSTRACTeIF2α phosphorylation-mediated translational regulation is crucial for global translation repression by various stresses, including the unfolded protein response (UPR). However, translational control during UPR has not been demonstrated in yeast. This study investigated ribosome ubiquitination-mediated translational controls during UPR. Tunicamycin-induced ER stress enhanced the levels of ubiquitination of the ribosomal proteins uS10, uS3 and eS7. Not4-mediated monoubiquitination of eS7A was required for resistance to tunicamycin, whereas E3 ligase Hel2-mediated ubiquitination of uS10 was not. Ribosome profiling showed that the monoubiquitination of eS7A was crucial for translational regulation, including the upregulation of the spliced form of HAC1 (HAC1i) mRNA and the downregulation of Histidine triad NucleoTide-binding 1 (HNT1) mRNA. Downregulation of the deubiquitinating enzyme complex Upb3-Bre5 increased the levels of ubiquitinated eS7A during UPR in an Ire1-independent manner. These findings suggest that the monoubiquitination of ribosomal protein eS7A plays a crucial role in translational controls during the ER stress response in yeast.

scholarly journals The Role of the Universally Conserved ATPase YchF/Ola1 in Translation Regulation during Cellular Stress

2021 ◽  
Vol 10 (1) ◽  
pp. 14
Author(s):  
Victoria Landwehr ◽  
Martin Milanov ◽  
Jiang Hong ◽  
Hans-Georg Koch
Keyword(s):  
Translation Initiation ◽  
Translational Control ◽  
Translational Regulation ◽  
Molecular Mechanisms ◽  
Environmental Changes ◽  
Essential Feature ◽  
Translation Regulation ◽  
Interacting Proteins ◽  
Translational Regulators

The ability to respond to metabolic or environmental changes is an essential feature in all cells and involves both transcriptional and translational regulators that adjust the metabolic activity to fluctuating conditions. While transcriptional regulation has been studied in detail, the important role of the ribosome as an additional player in regulating gene expression is only beginning to emerge. Ribosome-interacting proteins are central to this translational regulation and include universally conserved ribosome interacting proteins, such as the ATPase YchF (Ola1 in eukaryotes). In both eukaryotes and bacteria, the cellular concentrations of YchF/Ola1 determine the ability to cope with different stress conditions and are linked to several pathologies in humans. The available data indicate that YchF/Ola1 regulates the stress response via controlling non-canonical translation initiation and via protein degradation. Although the molecular mechanisms appear to be different between bacteria and eukaryotes, increased non-canonical translation initiation is a common consequence of YchF/Ola1 regulated translational control in E. coli and H. sapiens. In this review, we summarize recent insights into the role of the universally conserved ATPase YchF/Ola1 in adapting translation to unfavourable conditions.

scholarly journals Visualization of Chromatin in the Yeast Nucleus and Nucleolus Using Hyperosmotic Shock

2021 ◽  
Vol 22 (3) ◽  
pp. 1132
Author(s):  
Nicolas Thelen ◽  
Jean Defourny ◽  
Denis L. J. Lafontaine ◽  
Marc Thiry
Keyword(s):  
Osmotic Shock ◽  
Size Composition ◽  
Yeast Cells ◽  
Exponential Growth Phase ◽  
Cell Nuclei ◽  
Hyperosmotic Shock ◽  
Christmas Trees ◽  
Transmission Electron ◽  
Active Transcription ◽  
Decondensed Chromatin

Unlike in most eukaryotic cells, the genetic information of budding yeast in the exponential growth phase is only present in the form of decondensed chromatin, a configuration that does not allow its visualization in cell nuclei conventionally prepared for transmission electron microscopy. In this work, we studied the distribution of chromatin and its relationships to the nucleolus using different cytochemical and immunocytological approaches applied to yeast cells subjected to hyperosmotic shock. Our results show that osmotic shock induces the formation of heterochromatin patches in the nucleoplasm and intranucleolar regions of the yeast nucleus. In the nucleolus, we further revealed the presence of osmotic shock-resistant DNA in the fibrillar cords which, in places, take on a pinnate appearance reminiscent of ribosomal genes in active transcription as observed after molecular spreading (“Christmas trees”). We also identified chromatin-associated granules whose size, composition and behaviour after osmotic shock are reminiscent of that of mammalian perichromatin granules. Altogether, these data reveal that it is possible to visualize heterochromatin in yeast and suggest that the yeast nucleus displays a less-effective compartmentalized organization than that of mammals.

scholarly journals Specific Functional Features of the Cell Integrity MAP Kinase Pathway in the Dimorphic Fission Yeast Schizosaccharomyces japonicus

2021 ◽  
Vol 7 (6) ◽  
pp. 482
Author(s):  
Elisa Gómez-Gil ◽  
Alejandro Franco ◽  
Beatriz Vázquez-Marín ◽  
Francisco Prieto-Ruiz ◽  
Armando Pérez-Díaz ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Environmental Changes ◽  
Yeast Species ◽  
Mapk Signaling ◽  
Fine Tuning ◽  
Mitogen Activated Protein Kinase ◽  
Major Influence ◽  
Cell Integrity ◽  
Mitogen Activated Protein ◽  
Functional Features

Mitogen activated protein kinase (MAPK) signaling pathways execute essential functions in eukaryotic organisms by transducing extracellular stimuli into adaptive cellular responses. In the fission yeast model Schizosaccharomyces pombe the cell integrity pathway (CIP) and its core effector, MAPK Pmk1, play a key role during regulation of cell integrity, cytokinesis, and ionic homeostasis. Schizosaccharomyces japonicus, another fission yeast species, shows remarkable differences with respect to S. pombe, including a robust yeast to hyphae dimorphism in response to environmental changes. We show that the CIP MAPK module architecture and its upstream regulators, PKC orthologs Pck1 and Pck2, are conserved in both fission yeast species. However, some of S. pombe’s CIP-related functions, such as cytokinetic control and response to glucose availability, are regulated differently in S. japonicus. Moreover, Pck1 and Pck2 antagonistically regulate S. japonicus hyphal differentiation through fine-tuning of Pmk1 activity. Chimeric MAPK-swapping experiments revealed that S. japonicus Pmk1 is fully functional in S. pombe, whereas S. pombe Pmk1 shows a limited ability to execute CIP functions and promote S. japonicus mycelial development. Our findings also suggest that a modified N-lobe domain secondary structure within S. japonicus Pmk1 has a major influence on the CIP signaling features of this evolutionarily diverged fission yeast.

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