scholarly journals Repressors and Upstream Repressing Sequences of the Stress-Regulated ENA1 Gene in Saccharomyces cerevisiae: bZIP Protein Sko1p Confers HOG-Dependent Osmotic Regulation

1999 ◽  
Vol 19 (1) ◽  
pp. 537-546 ◽  
Author(s):  
Markus Proft ◽  
Ramón Serrano
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Salt Stress ◽  
Osmotic Stress ◽  
Transcriptional Repression ◽  
Glucose Repression ◽  
Osmotic Shock ◽  
Mitogen Activated Protein Kinase ◽  
Deletion Strain ◽  
Binding Motif ◽  
Hog Pathway

ABSTRACT The yeast ENA1/PMR2A gene encodes a cation extrusion ATPase in Saccharomyces cerevisiae which is essential for survival under salt stress conditions. One important mechanism ofENA1 transcriptional regulation is based on repression under normal growth conditions, which is relieved by either osmotic induction or glucose starvation. Analysis of the ENA1promoter revealed a Mig1p-binding motif (−533 to −544) which was characterized as an upstream repressing sequence (URSMIG-ENA1 ) regulated by carbon source. Its function was abolished in a mig1 mig2 double-deletion strain as well as in either ssn6 or tup1 single mutants. A second URS at −502 to −513 is responsible for transcriptional repression regulated by osmotic stress and is similar to mammalian cyclic AMP response elements (CREs) that are recognized by CREB proteins. This URSCRE-ENA1 element requires for its repression function the yeast CREB homolog Sko1p (Acr1p) as well as the integrity of the Ssn6p-Tup1p corepressor complex. When targeted to the GAL1 promoter by fusing with the Gal4p DNA-binding domain, Sko1p acts as an Ssn6/Tup1p-dependent repressor regulated by osmotic stress. A glutathione S -transferase–Sko1 fusion protein binds specifically to the URSCRE-ENA1 element. Furthermore, ahog1 mitogen-activated protein kinase deletion strain could not counteract repression on URSCRE-ENA1 during osmotic shock. The loss of SKO1 completely restoredENA1 expression in a hog1 mutant and partially suppressed the osmotic stress sensitivity, qualifying Sko1p as a downstream effector of the HOG pathway. Our results indicate that different signalling pathways (HOG osmotic pathway and glucose repression pathway) use distinct promoter elements of ENA1(URSCRE-ENA1 and URSMIG-ENA1 ) via specific transcriptional repressors (Sko1p and Mig1/2p) and via the general Ssn6p-Tup1p complex. The physiological importance of the relief from repression during salt stress was also demonstrated by the increased tolerance ofsko1 or ssn6 mutants to Na+ or Li+ stress.

scholarly journals Osmotic Stress-Induced Gene Expression in Saccharomyces cerevisiae Requires Msn1p and the Novel Nuclear Factor Hot1p

1999 ◽  
Vol 19 (8) ◽  
pp. 5474-5485 ◽  
Author(s):  
Martijn Rep ◽  
Vladimír Reiser ◽  
Ulrike Gartner ◽  
Johan M. Thevelein ◽  
Stefan Hohmann ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Osmotic Stress ◽  
Transcriptional Response ◽  
Mitogen Activated Protein Kinase ◽  
The Novel ◽  
Hog Pathway ◽  
High Osmolarity ◽  
Nuclear Factors ◽  
Mitogen Activated Protein ◽  
Protective Genes

ABSTRACT After a sudden shift to high osmolarity, Saccharomyces cerevisiae cells respond by transiently inducing the expression of stress-protective genes. Msn2p and Msn4p have been described as two transcription factors that determine the extent of this response. Inmsn2 msn4 mutants, however, many promoters still show a distinct rise in transcriptional activity upon osmotic stress. Here we describe two structurally related nuclear factors, Msn1p and a newly identified protein, Hot1p (for high-osmolarity-induced transcription), which are also involved in osmotic stress-induced transcription.hot1 single mutants are specifically compromised in the transient induction of GPD1 and GPP2, which encode enzymes involved in glycerol biosynthesis, and exhibit delayed glycerol accumulation after stress exposure. Similar to agpd1 mutation, a hot1 defect can rescue cells from inappropriately high HOG pathway activity. In contrast, Hot1p has little influence on the osmotic stress induction of CTT1, where Msn1p appears to play a more prominent role. Cells lacking Msn1p, Msn2p, Msn4p, and Hot1p are almost devoid of the short-term transcriptional response of the genes GPD1,GPP2, CTT1, and HSP12 to osmotic stress. Such cells also show a distinct reduction in the nuclear residence of the mitogen-activated protein kinase Hog1p upon osmotic stress. Thus, Hot1p and Msn1p may define an additional tier of transcriptional regulators that control responses to high-osmolarity stress.

scholarly journals Activation of the Saccharomyces cerevisiae Filamentation/Invasion Pathway by Osmotic Stress in High-Osmolarity Glycogen Pathway Mutants

Genetics ◽  
1999 ◽  
Vol 153 (3) ◽  
pp. 1091-1103 ◽  
Author(s):  
K D Davenport ◽  
K E Williams ◽  
B D Ullmann ◽  
M C Gustin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Osmotic Stress ◽  
Mitogen Activated Protein Kinase ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Hog Pathway ◽  
High Osmolarity ◽  
Hypertonic Stress ◽  
Mapk Cascades ◽  
Invasion Pathway

Abstract Mitogen-activated protein kinase (MAPK) cascades are frequently used signal transduction mechanisms in eukaryotes. Of the five MAPK cascades in Saccharomyces cerevisiae, the high-osmolarity glycerol response (HOG) pathway functions to sense and respond to hypertonic stress. We utilized a partial loss-of-function mutant in the HOG pathway, pbs2-3, in a high-copy suppressor screen to identify proteins that modulate growth on high-osmolarity media. Three high-copy suppressors of pbs2-3 osmosensitivity were identified: MSG5, CAK1, and TRX1. Msg5p is a dual-specificity phosphatase that was previously demonstrated to dephosphorylate MAPKs in yeast. Deletions of the putative MAPK targets of Msg5p revealed that kss1Δ could suppress the osmosensitivity of pbs2-3. Kss1p is phosphorylated in response to hyperosmotic shock in a pbs2-3 strain, but not in a wild-type strain nor in a pbs2-3 strain overexpressing MSG5. Both TEC1 and FRE::lacZ expressions are activated in strains lacking a functional HOG pathway during osmotic stress in a filamentation/invasion-pathway-dependent manner. Additionally, the cellular projections formed by a pbs2-3 mutant on high osmolarity are absent in strains lacking KSS1 or STE7. These data suggest that the loss of filamentation/invasion pathway repression contributes to the HOG mutant phenotype.

scholarly journals Glucose derepression of gluconeogenic enzymes in Saccharomyces cerevisiae correlates with phosphorylation of the gene activator Cat8p.

1997 ◽  
Vol 17 (5) ◽  
pp. 2502-2510 ◽  
Author(s):  
F Randez-Gil ◽  
N Bojunga ◽  
M Proft ◽  
K D Entian
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Transcriptional Activation ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Repression ◽  
Sodium Dodecyl ◽  
Binding Motif ◽  
Gluconeogenic Enzymes ◽  
Zinc Cluster ◽  
Activating Function

The Cat8p zinc cluster protein is essential for growth of Saccharomyces cerevisiae with nonfermentable carbon sources. Expression of the CAT8 gene is subject to glucose repression mainly caused by Mig1p. Unexpectedly, the deletion of the Mig1p-binding motif within the CAT8 promoter did not increase CAT8 transcription; moreover, it resulted in a loss of CAT8 promoter activation. Insertion experiments with a promoter test plasmid confirmed that this regulatory 20-bp element influences glucose repression and derepression as well. This finding suggests an upstream activating function of this promoter region, which is Mig1p independent, as delta mig1 mutants are still able to derepress the CAT8 promoter. No other putative binding sites such as a Hap2/3/4/5p site and an Abf1p consensus site were functional with respect to glucose-regulated CAT8 expression. Fusions of Cat8p with the Gal4p DNA-binding domain mediated transcriptional activation. This activation capacity was still carbon source regulated and depended on the Cat1p (Snf1p) protein kinase, which indicated that Cat8p needs posttranslational modification to reveal its gene-activating function. Indeed, Western blot analysis on sodium dodecyl sulfate-gels revealed a single band (Cat8pI) with crude extracts from glucose-grown cells, whereas three bands (Cat8pI, -II, and -III) were identified in derepressed cells. Derepression-specific Cat8pII and -III resulted from differential phosphorylation, as shown by phosphatase treatment. Only the most extensively phosphorylated modification (Cat8pIII) depended on the Cat1p (Snf1p) kinase, indicating that another protein kinase is responsible for modification form Cat8pII. The occurrence of Cat8pIII was strongly correlated with the derepression of gluconeogenic enzymes (phosphoenolpyruvate carboxykinase and fructose-1,6-bisphosphatase) and gluconeogenic PCK1 mRNA. Furthermore, glucose triggered the dephosphorylation of Cat8pIII, but this did not depend on the Glc7p (Cid1p) phosphatase previously described as being involved in invertase repression. These results confirm our current model that glucose derepression of gluconeogenic genes needs Cat8p phosphorylation and additionally show that a still unknown transcriptional activator is also involved.

GPD1, which encodes glycerol-3-phosphate dehydrogenase, is essential for growth under osmotic stress in Saccharomyces cerevisiae, and its expression is regulated by the high-osmolarity glycerol response pathway

1994 ◽  
Vol 14 (6) ◽  
pp. 4135-4144
Author(s):  
J Albertyn ◽  
S Hohmann ◽  
J M Thevelein ◽  
B A Prior
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Osmotic Stress ◽  
Yeast Cells ◽  
Mrna Levels ◽  
Hog Pathway ◽  
Hypertonic Medium ◽  
High Osmolarity ◽  
High Osmolarity Glycerol ◽  
Enhanced Production ◽  
Glycerol 3 Phosphate Dehydrogenase

The yeast Saccharomyces cerevisiae responds to osmotic stress, i.e., an increase in osmolarity of the growth medium, by enhanced production and intracellular accumulation of glycerol as a compatible solute. We have cloned a gene encoding the key enzyme of glycerol synthesis, the NADH-dependent cytosolic glycerol-3-phosphate dehydrogenase, and we named it GPD1. gpd1 delta mutants produced very little glycerol, and they were sensitive to osmotic stress. Thus, glycerol production is indeed essential for the growth of yeast cells during reduced water availability. hog1 delta mutants lacking a protein kinase involved in osmostress-induced signal transduction (the high-osmolarity glycerol response [HOG] pathway) failed to increase glycerol-3-phosphate dehydrogenase activity and mRNA levels when osmotic stress was imposed. Thus, expression of GPD1 is regulated through the HOG pathway. However, there may be Hog1-independent mechanisms mediating osmostress-induced glycerol accumulation, since a hog1 delta strain could still enhance its glycerol content, although less than the wild type. hog1 delta mutants are more sensitive to osmotic stress than isogenic gpd1 delta strains, and gpd1 delta hog1 delta double mutants are even more sensitive than either single mutant. Thus, the HOG pathway most probably has additional targets in the mechanism of adaptation to hypertonic medium.

scholarly journals Steady-state analysis of glucose repression reveals hierarchical expression of proteins under Mig1p control in Saccharomyces cerevisiae

2005 ◽  
Vol 388 (3) ◽  
pp. 843-849 ◽  
Author(s):  
Malkhey VERMA ◽  
Paike J. BHAT ◽  
K. V. VENKATESH
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Steady State ◽  
Glucose Repression ◽  
Transcriptional Response ◽  
Mitogen Activated Protein Kinase ◽  
Critical Feature ◽  
Steady State Analysis ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
State Analysis

Glucose repression is a global transcriptional regulatory mechanism commonly observed in micro-organisms for the repression of enzymes that are not essential for glucose metabolism. In Saccharomyces cerevisiae, Mig1p, a homologue of Wilms' tumour protein, is a global repressor protein dedicated to glucose repression. Mig1p represses genes either by binding directly to the upstream repression sequence of structural genes or by indirectly repressing a transcriptional activator, such as Gal4p. In addition, some genes are repressed by both of the above mechanisms. This raises a fundamental question regarding the physiological relevance of the varied mechanisms of repression that exist involving Mig1p. We address this issue by comparing two well-known glucose-repression systems, that is, SUC2 and GAL gene expression systems, which encompass all the above three mechanisms. We demonstrate using steady-state analysis that these mechanisms lead to a hierarchical glucose repression profile of different family of genes. This switch over from one carbon source to another is well-calibrated as a function of glucose concentration through this hierarchical transcriptional response. The mechanisms prevailing in this repression system can achieve amplification and sensitivity, as observed in the well-characterized MAPK (mitogen-activated protein kinase) cascade system, albeit through a different structure. A critical feature of repression predicted by our steady-state model for the mutant strain of S. cerevisiae lacking Gal80p agrees well with the data reported here as well as that available in the literature.

scholarly journals Rgt1, a glucose sensing transcription factor, is required for transcriptional repression of the HXK2 gene in Saccharomyces cerevisiae

2005 ◽  
Vol 388 (2) ◽  
pp. 697-703 ◽  
Author(s):  
Aaron PALOMINO ◽  
Pilar HERRERO ◽  
Fernando MORENO
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Transcriptional Repression ◽  
Glucose Repression ◽  
Fold Increase ◽  
Glucose Sensing ◽  
Start Codon ◽  
Dependent Manner ◽  
Gene Encoding ◽  
Regulatory Functions

Expression of HXK2, a gene encoding a Saccharomyces cerevisiae bifunctional protein with catalytic and regulatory functions, is controlled by glucose availability, being activated in the presence of glucose and inhibited when the levels of the sugar are low. In the present study, we identified Rgt1 as a transcription factor that, together with the Med8 protein, is essential for repression of the HXK2 gene in the absence of glucose. Rgt1 represses HXK2 expression by binding specifically to the motif (CGGAAAA) located at −395 bp relative to the ATG translation start codon in the HXK2 promoter. Disruption of the RGT1 gene causes an 18-fold increase in the level of HXK2 transcript in the absence of glucose. Rgt1 binds to the RGT1 element of HXK2 promoter in a glucose-dependent manner, and the repression of target gene depends on binding of Rgt1 to DNA. The physiological significance of the connection between two glucose-signalling pathways, the Snf3/Rgt2 that causes glucose induction and the Mig1/Hxk2 that causes glucose repression, was also analysed.

scholarly journals Msb2 Signaling Mucin Controls Activation of Cek1 Mitogen-Activated Protein Kinase in Candida albicans

2009 ◽  
Vol 8 (8) ◽  
pp. 1235-1249 ◽  
Author(s):  
Elvira Román ◽  
Fabien Cottier ◽  
Joachim F. Ernst ◽  
Jesús Pla
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Protein Kinase ◽  
Osmotic Shock ◽  
Mitogen Activated Protein Kinase ◽  
Hog Pathway ◽  
High Osmolarity ◽  
Cell Wall Biogenesis ◽  
Solid Media ◽  
Mitogen Activated Protein

ABSTRACT We have characterized the role that the Msb2 protein plays in the fungal pathogen Candida albicans by the use of mutants defective in the putative upstream components of the HOG pathway. Msb2, in cooperation with Sho1, controls the activation of the Cek1 mitogen-activated protein kinase under conditions that damage the cell wall, thus defining Msb2 as a signaling element of this pathway in the fungus. msb2 mutants display altered sensitivity to Congo red, caspofungin, zymolyase, or tunicamycin, indicating that this protein is involved in cell wall biogenesis. Msb2 (as well as Sho1 and Hst7) is involved in the transmission of the signal toward Cek1 mediated by the Cdc42 GTPase, as revealed by the use of activated alleles (Cdc42G12V) of this protein. msb2 mutants have a stronger defective invasion phenotype than sho1 mutants when tested on certain solid media that use mannitol or sucrose as a carbon source or under hypoxia. Interestingly, Msb2 contributes to growth under conditions of high osmolarity when both branches of the HOG pathway are altered, as triple ssk1 msb2 sho1 mutants (but not any single or double mutant) are osmosensitive. However, this phenomenon is independent of the presence of Hog1, as Hog1 phosphorylation, Hog1 translocation to the nucleus, and glycerol accumulation are not affected in this mutant following an osmotic shock. These results reveal essential functions in morphogenesis, invasion, cell wall biogenesis, and growth under conditions of high osmolarity for Msb2 in C. albicans and suggest the divergence and specialization of this signaling pathway in filamentous fungi.

scholarly journals Altered Phosphotransfer in an Activated Mutant of the Saccharomyces cerevisiae Two-Component Osmosensor Sln1p

2002 ◽  
Vol 1 (2) ◽  
pp. 174-180 ◽  
Author(s):  
A. D. Ault ◽  
J. S. Fassler ◽  
R. J. Deschenes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Osmotic Stress ◽  
Stress Responses ◽  
Mitogen Activated Protein Kinase ◽  
Phosphoryl Group ◽  
Response Regulators ◽  
Two Component ◽  
Mitogen Activated Protein ◽  
Receiver Module ◽  
Kinase Pathway

ABSTRACT The SLN1 two-component signaling pathway of Saccharomyces cerevisiae utilizes a multistep phosphorelay mechanism to control osmotic stress responses via the HOG1 mitogen-activated protein kinase pathway and the transcription factor Skn7p. Sln1p consists of a sensor kinase module that undergoes histidine autophosphorylation and a receiver module that autocatalytically transfers the phosphoryl group from histidine to aspartate. The Sln1p aspartyl phosphate is then transferred to Ypd1p, which in turn transfers the phosphoryl group to a conserved aspartate on one of two response regulators, Ssk1p and Skn7p. Activated alleles of SLN1 (sln1*) were previously identified that appear to increase the level of phosphorylation of downstream targets Ssk1p and Skn7p. In principle, the phenotype of sln1* alleles could arise from an increase in autophosphorylation or phosphotransfer activities or a decrease in an intrinsic or extrinsic dephosphorylation activity. Genetic analysis of the activated mutants has been unable to distinguish between these possibilities. In this report, we address this issue by analyzing phosphorelay and phosphohydrolysis reactions involving the Sln1p-associated receiver. The results are consistent with a model in which the activated phenotype of the sln1* allele, sln1-22, arises from a shift in the phosphotransfer equilibrium from Sln1p to Ypd1p, rather than from impaired dephosphorylation of the system in response to osmotic stress.

scholarly journals Ineffective Phosphorylation of Mitogen-Activated Protein Kinase Hog1p in Response to High Osmotic Stress in the Yeast Kluyveromyces lactis

2015 ◽  
Vol 14 (9) ◽  
pp. 922-930 ◽  
Author(s):  
Nancy Velázquez-Zavala ◽  
Miriam Rodríguez-González ◽  
Rocío Navarro-Olmos ◽  
Laura Ongay-Larios ◽  
Laura Kawasaki ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Osmotic Stress ◽  
Kluyveromyces Lactis ◽  
Chimeric Protein ◽  
High Sensitivity ◽  
Hyperosmotic Stress ◽  
Mitogen Activated Protein Kinase ◽  
Hog Pathway ◽  
Content Type ◽  
Mitogen Activated Protein

ABSTRACT When treated with a hyperosmotic stimulus, Kluyveromyces lactis cells respond by activating the mitogen-activated protein kinase (MAPK) K. lactis Hog1 (KlHog1) protein via two conserved branches, SLN1 and SHO1. Mutants affected in only one branch can cope with external hyperosmolarity by activating KlHog1p by phosphorylation, except for single Δ Klste11 and Δ Klste50 mutants, which showed high sensitivity to osmotic stress, even though the other branch (SLN1) was intact. Inactivation of both branches by deletion of KlSHO1 and KlSSK2 also produced sensitivity to high salt. Interestingly, we have observed that in Δ Klste11 and Δ Klsho1 Δ Klssk2 mutants, which exhibit sensitivity to hyperosmotic stress, and contrary to what would be expected, KlHog1p becomes phosphorylated. Additionally, in mutants lacking both MAPK kinase kinases (MAPKKKs) present in K. lactis (KlSte11p and KlSsk2p), the hyperosmotic stress induced the phosphorylation and nuclear internalization of KlHog1p, but it failed to induce the transcriptional expression of KlSTL1 and the cell was unable to grow in high-osmolarity medium. KlHog1p phosphorylation via the canonical HOG pathway or in mutants where the SHO1 and SLN1 branches have been inactivated requires not only the presence of KlPbs2p but also its kinase activity. This indicates that when the SHO1 and SLN1 branches are inactivated, high-osmotic-stress conditions activate an independent input that yields active KlPbs2p, which, in turn, renders KlHog1p phosphorylation ineffective. Finally, we found that KlSte11p can alleviate the sensitivity to hyperosmotic stress displayed by a Δ Klsho1 Δ Klssk2 mutant when it is anchored to the plasma membrane by adding the KlSho1p transmembrane segments, indicating that this chimeric protein can substitute for KlSho1p and KlSsk2p.

Response to high osmotic conditions and elevated temperature in Saccharomyces cerevisiae is controlled by intracellular glycerol and involves coordinate activity of MAP kinase pathways

Microbiology ◽  
2003 ◽  
Vol 149 (5) ◽  
pp. 1193-1204 ◽  
Author(s):  
Iwona Wojda ◽  
Rebeca Alonso-Monge ◽  
Jan-Paul Bebelman ◽  
Willem H. Mager ◽  
Marco Siderius
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Osmotic Stress ◽  
Map Kinase ◽  
Growth Temperature ◽  
Wild Type ◽  
Hog Pathway ◽  
Map Kinase Pathway ◽  
Kinase Pathway ◽  
Intracellular Glycerol

In the yeast Saccharomyces cerevisiae, response to an increase in external osmolarity is mediated by the HOG (high osmolarity glycerol) MAP kinase pathway. HOG pathway mutant strains display osmosensitive phenotypes. Recently evidence has been obtained that the osmosensitivity of HOG pathway mutants is reduced during growth at elevated temperature (37 °C). A notable exception is the ste11ssk2ssk22 mutant, which displays hypersensitivity to osmotic stress at 37 °C. This paper reports that overexpression of FPS1 or GPD1 (encoding the glycerol transport facilitator and glycerol-3-phosphate dehydrogenase, respectively, and both affecting intracellular glycerol levels) reduces the hypersensitivity to osmotic stress of ste11ssk2ssk22 at 37 °C. Although in this particular HOG pathway mutant a correlation between suppression of the phenotype and glycerol content could be demonstrated, the absolute level of intracellular glycerol per se does not determine whether a strain is osmosensitive or not. Rather, evidence was obtained that the glycerol level may have an indirect effect, viz. by influencing signalling through the PKC (protein kinase C) MAP kinase pathway, which plays an important role in maintenance of cellular integrity. In order to validate the data obtained with a HOG pathway mutant strain for wild-type yeast cells, MAP kinase signalling under different growth conditions was examined in wild-type strains. PKC pathway signalling, which is manifest at elevated growth temperature by phosphorylation of MAP kinase Mpk1p, is rapidly lost when cells are shifted to high external osmolarity conditions. Expression of bck1-20 or overexpression of WSC3 in wild-type cells resulted in restoration of PKC signalling. Both PKC and HOG signalling, cell wall phenotypes and high osmotic stress responses in wild-type cells were found to be influenced by the growth temperature. The data taken together indicate the intricate interdependence of growth temperature, intracellular glycerol, cell wall structure and MAP kinase signalling in the hyperosmotic stress response of yeast.

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