Articles de revues : « Saccharomyces cerevisiae Signal Transduction »

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Portela, P., et Silvia Rossi. « cAMP-PKA signal transduction specificity in Saccharomyces cerevisiae ». Current Genetics 66, n^o 6 (15 septembre 2020) : 1093–99. http://dx.doi.org/10.1007/s00294-020-01107-6.

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Oehlen, Bert, et Frederick R. Cross. « Signal transduction in the budding yeast Saccharomyces cerevisiae ». Current Opinion in Cell Biology 6, n^o 6 (décembre 1994) : 836–41. http://dx.doi.org/10.1016/0955-0674(94)90053-1.

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Pan, Xuewen, Toshiaki Harashima et Joseph Heitman. « Signal transduction cascades regulating pseudohyphal differentiation of Saccharomyces cerevisiae ». Current Opinion in Microbiology 3, n^o 6 (décembre 2000) : 567–72. http://dx.doi.org/10.1016/s1369-5274(00)00142-9.

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Magasanik, B. « The transduction of the nitrogen regulation signal in Saccharomyces cerevisiae ». Proceedings of the National Academy of Sciences 102, n^o 46 (7 novembre 2005) : 16537–38. http://dx.doi.org/10.1073/pnas.0507116102.

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Kaniak, Aneta, Zhixiong Xue, Daniel Macool, Jeong-Ho Kim et Mark Johnston. « Regulatory Network Connecting Two Glucose Signal Transduction Pathways in Saccharomyces cerevisiae ». Eukaryotic Cell 3, n^o 1 (février 2004) : 221–31. http://dx.doi.org/10.1128/ec.3.1.221-231.2004.

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ABSTRACT The yeast Saccharomyces cerevisiae senses glucose, its preferred carbon source, through multiple signal transduction pathways. In one pathway, glucose represses the expression of many genes through the Mig1 transcriptional repressor, which is regulated by the Snf1 protein kinase. In another pathway, glucose induces the expression of HXT genes encoding glucose transporters through two glucose sensors on the cell surface that generate an intracellular signal that affects function of the Rgt1 transcription factor. We profiled the yeast transcriptome to determine the range of genes targeted by this second pathway. Candidate target genes were verified by testing for Rgt1 binding to their promoters by chromatin immunoprecipitation and by measuring the regulation of the expression of promoter lacZ fusions. Relatively few genes could be validated as targets of this pathway, suggesting that this pathway is primarily dedicated to regulating the expression of HXT genes. Among the genes regulated by this glucose signaling pathway are several genes involved in the glucose induction and glucose repression pathways. The Snf3/Rgt2-Rgt1 glucose induction pathway contributes to glucose repression by inducing the transcription of MIG2, which encodes a repressor of glucose-repressed genes, and regulates itself by inducing the expression of STD1, which encodes a regulator of the Rgt1 transcription factor. The Snf1-Mig1 glucose repression pathway contributes to glucose induction by repressing the expression of SNF3 and MTH1, which encodes another regulator of Rgt1, and also regulates itself by repressing the transcription of MIG1. Thus, these two glucose signaling pathways are intertwined in a regulatory network that serves to integrate the different glucose signals operating in these two pathways.

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Choi, You-Jeong, Sun-Hong Kim, Ki-Sook Park et Kang-Yell Choi. « Differential transmission of G1 cell cycle arrest and mating signals by Saccharomyces cerevisiae Ste5 mutants in the pheromone pathway ». Biochemistry and Cell Biology 77, n^o 5 (1 octobre 1999) : 459–68. http://dx.doi.org/10.1139/o99-054.

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Saccharomyces cerevisiae Ste5 is a scaffold protein that recruits many pheromone signaling molecules to sequester the pheromone pathway from other homologous mitogen-activated protein kinase pathways. G1 cell cycle arrest and mating are two different physiological consequences of pheromone signal transduction and Ste5 is required for both processes. However, the roles of Ste5 in G1 arrest and mating are not fully understood. To understand the roles of Ste5 better, we isolated 150 G1 cell cycle arrest defective STE5 mutants by chemical mutagenesis of the gene. Here, we found that two G1 cell cycle arrest defective STE5 mutants (ste5MD248V and ste5delta-776) retained mating capacity. When overproduced in a wild-type strain, several ste5 mutants also showed different dominant phenotypes for G1 arrest and mating. Isolation and characterization of the mutants suggested separable roles of Ste5 in G1 arrest and mating of S. cerevisiae. In addition, the roles of Asp-248 and Tyr-421, which are important for pheromone signal transduction were further characterized by site-directed mutagenesis studies.Key words: Ste5, Saccharomyces cerevisiae, signal transduction, mating, G1 cell cycle arrest.

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Moskow, John J., Amy S. Gladfelter, Rachel E. Lamson, Peter M. Pryciak et Daniel J. Lew. « Role of Cdc42p in Pheromone-Stimulated Signal Transduction in Saccharomyces cerevisiae ». Molecular and Cellular Biology 20, n^o 20 (15 octobre 2000) : 7559–71. http://dx.doi.org/10.1128/mcb.20.20.7559-7571.2000.

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ABSTRACT CDC42 encodes a highly conserved GTPase of the Rho family that is best known for its role in regulating cell polarity and actin organization. In addition, various studies of both yeast and mammalian cells have suggested that Cdc42p, through its interaction with p21-activated kinases (PAKs), plays a role in signaling pathways that regulate target gene transcription. However, recent studies of the yeast pheromone response pathway suggested that prior results with temperature-sensitive cdc42 mutants were misleading and that Cdc42p and the Cdc42p-PAK interaction are not involved in signaling. To clarify this issue, we have identified and characterized novel viable pheromone-resistant cdc42 alleles that retain the ability to perform polarity-related functions. Mutation of the Cdc42p residue Val36 or Tyr40 caused defects in pheromone signaling and in the localization of the Ste20p PAK in vivo and affected binding to the Ste20p Cdc42p-Rac interactive binding (CRIB) domain in vitro. Epistasis analysis suggested that they affect the signaling step at which Ste20p acts, and overproduction of Ste20p rescued the defect. These results suggest that Cdc42p is in fact required for pheromone response and that interaction with the PAK Ste20p is critical for that role. Furthermore, the ste20ΔCRIB allele, previously used to disrupt the Cdc42p-Ste20p interaction, behaved as an activated allele, largely bypassing the signaling defect of thecdc42 mutants. Additional observations lead us to suggest that Cdc42p collaborates with the SH3-domain protein Bem1p to facilitate signal transduction, possibly by providing a cell surface scaffold that aids in the local concentration of signaling kinases, thus promoting activation of a mitogen-activated protein kinase cascade by Ste20p.

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Santangelo, George M. « Glucose Signaling in Saccharomyces cerevisiae ». Microbiology and Molecular Biology Reviews 70, n^o 1 (mars 2006) : 253–82. http://dx.doi.org/10.1128/mmbr.70.1.253-282.2006.

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SUMMARY Eukaryotic cells possess an exquisitely interwoven and fine-tuned series of signal transduction mechanisms with which to sense and respond to the ubiquitous fermentable carbon source glucose. The budding yeast Saccharomyces cerevisiae has proven to be a fertile model system with which to identify glucose signaling factors, determine the relevant functional and physical interrelationships, and characterize the corresponding metabolic, transcriptomic, and proteomic readouts. The early events in glucose signaling appear to require both extracellular sensing by transmembrane proteins and intracellular sensing by G proteins. Intermediate steps involve cAMP-dependent stimulation of protein kinase A (PKA) as well as one or more redundant PKA-independent pathways. The final steps are mediated by a relatively small collection of transcriptional regulators that collaborate closely to maximize the cellular rates of energy generation and growth. Understanding the nuclear events in this process may necessitate the further elaboration of a new model for eukaryotic gene regulation, called “reverse recruitment.” An essential feature of this idea is that fine-structure mapping of nuclear architecture will be required to understand the reception of regulatory signals that emanate from the plasma membrane and cytoplasm. Completion of this task should result in a much improved understanding of eukaryotic growth, differentiation, and carcinogenesis.

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Lengeler, Klaus B., Robert C. Davidson, Cletus D'souza, Toshiaki Harashima, Wei-Chiang Shen, Ping Wang, Xuewen Pan, Michael Waugh et Joseph Heitman. « Signal Transduction Cascades Regulating Fungal Development and Virulence ». Microbiology and Molecular Biology Reviews 64, n^o 4 (1 décembre 2000) : 746–85. http://dx.doi.org/10.1128/mmbr.64.4.746-785.2000.

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SUMMARY Cellular differentiation, mating, and filamentous growth are regulated in many fungi by environmental and nutritional signals. For example, in response to nitrogen limitation, diploid cells of the yeast Saccharomyces cerevisiae undergo a dimorphic transition to filamentous growth referred to as pseudohyphal differentiation. Yeast filamentous growth is regulated, in part, by two conserved signal transduction cascades: a mitogen-activated protein kinase cascade and a G-protein regulated cyclic AMP signaling pathway. Related signaling cascades play an analogous role in regulating mating and virulence in the plant fungal pathogen Ustilago maydis and the human fungal pathogens Cryptococcus neoformans and Candida albicans. We review here studies on the signaling cascades that regulate development of these and other fungi. This analysis illustrates both how the model yeast S. cerevisiae can serve as a paradigm for signaling in other organisms and also how studies in other fungi provide insights into conserved signaling pathways that operate in many divergent organisms.

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Xu, Gang, Gregor Jansen, David Y. Thomas, Cornelis P. Hollenberg et Massoud Ramezani Rad. « Ste50p sustains mating pheromone-induced signal transduction in the yeast Saccharomyces cerevisiae ». Molecular Microbiology 20, n^o 4 (mai 1996) : 773–83. http://dx.doi.org/10.1111/j.1365-2958.1996.tb02516.x.

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BROACH, J. « RAS genes in Saccharomyces cerevisiae : signal transduction in search of a pathway ». Trends in Genetics 7, n^o 1 (janvier 1991) : 28–33. http://dx.doi.org/10.1016/0168-9525(91)90018-l.

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Loomis, W. F., G. Shaulsky et N. Wang. « Histidine kinases in signal transduction pathways of eukaryotes ». Journal of Cell Science 110, n^o 10 (15 mai 1997) : 1141–45. http://dx.doi.org/10.1242/jcs.110.10.1141.

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Autophosphorylating histidine kinases are an ancient conserved family of enzymes that are found in eubacteria, archaebacteria and eukaryotes. They are activated by a wide range of extracellular signals and transfer phosphate moieties to aspartates found in response regulators. Recent studies have shown that such two-component signal transduction pathways mediate osmoregulation in Saccharomyces cerevisiae, Dictyostelium discoideum and Neurospora crassa. Moreover, they play pivotal roles in responses of Arabidopsis thaliana to ethylene and cytokinin. A transmembrane histidine kinase encoded by dhkA accumulates when Dictyostelium cells aggregate during development. Activation of DhkA results in the inhibition of its response regulator, RegA, which is a cAMP phosphodiesterase that regulates the cAMP dependent protein kinase PKA. When PKA is activated late in the differentiation of prespore cells, they encapsulate into spores. There is evidence that this two-component system participates in a feedback loop linked to PKA in prestalk cells such that the signal to initiate encapsulation is rapidly amplified. Such signal transduction pathways can be expected to be found in a variety of eukaryotic differentiations since they are rapidly reversible and can integrate disparate signals.

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Alepuz, Paula M., Dina Matheos, Kyle W. Cunningham et Francisco Estruch. « The Saccharomyces cerevisiae RanGTP-Binding Protein Msn5p Is Involved in Different Signal Transduction Pathways ». Genetics 153, n^o 3 (1 novembre 1999) : 1219–31. http://dx.doi.org/10.1093/genetics/153.3.1219.

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Abstract In eukaryotes, control of transcription by extracellular signals involves the translocation to the nucleus of at least one component of the signal transduction pathway. Transport through the nuclear envelope requires the activity of an import or export receptor that interacts with the small GTPase Ran. We have cloned the MSN5 gene of the yeast Saccharomyces cerevisiae that is postulated to encode one of these receptors. Msn5p belongs to a family of proteins with a conserved N-terminal sequence that acts as a RanGTP-binding domain. The results presented here provide genetic data supporting Msn5p involvement in several different signal transduction pathways. All of these pathways include changes in gene expression, and regulated nucleocytoplasmic redistribution of a component in response to external conditions has already been described in some of them. We have cloned MSN5 following two different strategies. Msn5p was constitutively localized in the nucleus. Phenotypic analysis of the msn5 mutant demonstrated that this protein participates in processes such as catabolite repression, calcium signaling, mating, and cell proliferation, as well as being involved in previously characterized phosphate utilization. Therefore, Msn5p could be a receptor for several proteins involved in different signaling pathways.

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Gomez, Shawn M., Shaw-Hwa Lo et Andrey Rzhetsky. « Probabilistic Prediction of Unknown Metabolic and Signal-Transduction Networks ». Genetics 159, n^o 3 (1 novembre 2001) : 1291–98. http://dx.doi.org/10.1093/genetics/159.3.1291.

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Abstract Regulatory networks provide control over complex cell behavior in all kingdoms of life. Here we describe a statistical model, based on representing proteins as collections of domains or motifs, which predicts unknown molecular interactions within these biological networks. Using known protein-protein interactions of Saccharomyces cerevisiae as training data, we were able to predict the links within this network with only 7% false-negative and 10% false-positive error rates. We also use Markov chain Monte Carlo simulation for the prediction of networks with maximum probability under our model. This model can be applied across species, where interaction data from one (or several) species can be used to infer interactions in another. In addition, the model is extensible and can be analogously applied to other molecular data (e.g., DNA sequences).

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Brill, J. A., E. A. Elion et G. R. Fink. « A role for autophosphorylation revealed by activated alleles of FUS3, the yeast MAP kinase homolog. » Molecular Biology of the Cell 5, n^o 3 (mars 1994) : 297–312. http://dx.doi.org/10.1091/mbc.5.3.297.

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We have isolated dominant gain-of-function (gf) mutations in FUS3, a Saccharomyces cerevisiae mitogen-activated protein (MAP) kinase homolog, that constitutively activate the yeast mating signal transduction pathway and confer hypersensitivity to mating pheromone. Surprisingly, the phenotypes of dominant FUS3gf mutations require the two protein kinases, STE7 and STE11. FUS3gf kinases are hyperphosphorylated in yeast independently of STE7. Consistent with this, FUS3gf kinases expressed in Escherichia coli exhibit an increased ability to autophosphorylate on tyrosine in vivo. FUS3gf mutations suppress the signal transduction defect of a severely catalytically impaired allele of STE7. This finding suggests that the tyrosine-phosphorylated form of FUS3 is a better substrate for activation by STE7. Furthermore, these results imply that the degree of autophosphorylation of a MAP kinase determines its threshold of sensitivity to upstream signals.

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Levin, David E. « Cell Wall Integrity Signaling in Saccharomyces cerevisiae ». Microbiology and Molecular Biology Reviews 69, n^o 2 (juin 2005) : 262–91. http://dx.doi.org/10.1128/mmbr.69.2.262-291.2005.

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SUMMARY The yeast cell wall is a highly dynamic structure that is responsible for protecting the cell from rapid changes in external osmotic potential. The wall is also critical for cell expansion during growth and morphogenesis. This review discusses recent advances in understanding the various signal transduction pathways that allow cells to monitor the state of the cell wall and respond to environmental challenges to this structure. The cell wall integrity signaling pathway controlled by the small G-protein Rho1 is principally responsible for orchestrating changes to the cell wall periodically through the cell cycle and in response to various forms of cell wall stress. This signaling pathway acts through direct control of wall biosynthetic enzymes, transcriptional regulation of cell wall-related genes, and polarization of the actin cytoskeleton. However, additional signaling pathways interface both with the cell wall integrity signaling pathway and with the actin cytoskeleton to coordinate polarized secretion with cell wall expansion. These include Ca2+ signaling, phosphatidylinositide signaling at the plasma membrane, sphingoid base signaling through the Pkh1 and -2 protein kinases, Tor kinase signaling, and pathways controlled by the Rho3, Rho4, and Cdc42 G-proteins.

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Lu, Jade Mei-Yeh, Robert J. Deschenes et Jan S. Fassler. « Role for the Ran Binding Protein, Mog1p, in Saccharomyces cerevisiae SLN1-SKN7 Signal Transduction ». Eukaryotic Cell 3, n^o 6 (décembre 2004) : 1544–56. http://dx.doi.org/10.1128/ec.3.6.1544-1556.2004.

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ABSTRACT Yeast Sln1p is an osmotic stress sensor with histidine kinase activity. Modulation of Sln1 kinase activity in response to changes in the osmotic environment regulates the activity of the osmotic response mitogen-activated protein kinase pathway and the activity of the Skn7p transcription factor, both important for adaptation to changing osmotic stress conditions. Many aspects of Sln1 function, such as how kinase activity is regulated to allow a rapid response to the continually changing osmotic environment, are not understood. To gain insight into Sln1p function, we conducted a two-hybrid screen to identify interactors. Mog1p, a protein that interacts with the yeast Ran1 homolog, Gsp1p, was identified in this screen. The interaction with Mog1p was characterized in vitro, and its importance was assessed in vivo. mog1 mutants exhibit defects in SLN1-SKN7 signal transduction and mislocalization of the Skn7p transcription factor. The requirement for Mog1p in normal localization of Skn7p to the nucleus does not fully account for the mog1-related defects in SLN1-SKN7 signal transduction, raising the possibility that Mog1p may play a role in Skn7 binding and activation of osmotic response genes.

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Cole, G. M., D. E. Stone et S. I. Reed. « Stoichiometry of G protein subunits affects the Saccharomyces cerevisiae mating pheromone signal transduction pathway. » Molecular and Cellular Biology 10, n^o 2 (février 1990) : 510–17. http://dx.doi.org/10.1128/mcb.10.2.510.

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The Saccharomyces cerevisiae GPA1, STE4, and STE18 genes encode products homologous to mammalian G-protein alpha, beta, and gamma subunits, respectively. All three genes function in the transduction of the signal generated by mating pheromone in haploid cells. To characterize more completely the role of these genes in mating, we have conditionally overexpressed GPA1, STE4, and STE18, using the galactose-inducible GAL1 promoter. Overexpression of STE4 alone, or STE4 together with STE18, generated a response in haploid cells suggestive of pheromone signal transduction: arrest in G1 of the cell cycle, formation of cellular projections, and induction of the pheromone-inducible transcript FUS1 25- to 70-fold. High-level STE18 expression alone had none of these effects, nor did overexpression of STE4 in a MATa/alpha diploid. However, STE18 was essential for the response, since overexpression of STE4 was unable to activate a response in a ste18 null strain. GPA1 hyperexpression suppressed the phenotype of STE4 overexpression. In addition, cells that overexpressed GPA1 were more resistant to pheromone and recovered more quickly from pheromone than did wild-type cells, which suggests that GPA1 may function in an adaptation response to pheromone.

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Cole, G. M., D. E. Stone et S. I. Reed. « Stoichiometry of G protein subunits affects the Saccharomyces cerevisiae mating pheromone signal transduction pathway ». Molecular and Cellular Biology 10, n^o 2 (février 1990) : 510–17. http://dx.doi.org/10.1128/mcb.10.2.510-517.1990.

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The Saccharomyces cerevisiae GPA1, STE4, and STE18 genes encode products homologous to mammalian G-protein alpha, beta, and gamma subunits, respectively. All three genes function in the transduction of the signal generated by mating pheromone in haploid cells. To characterize more completely the role of these genes in mating, we have conditionally overexpressed GPA1, STE4, and STE18, using the galactose-inducible GAL1 promoter. Overexpression of STE4 alone, or STE4 together with STE18, generated a response in haploid cells suggestive of pheromone signal transduction: arrest in G1 of the cell cycle, formation of cellular projections, and induction of the pheromone-inducible transcript FUS1 25- to 70-fold. High-level STE18 expression alone had none of these effects, nor did overexpression of STE4 in a MATa/alpha diploid. However, STE18 was essential for the response, since overexpression of STE4 was unable to activate a response in a ste18 null strain. GPA1 hyperexpression suppressed the phenotype of STE4 overexpression. In addition, cells that overexpressed GPA1 were more resistant to pheromone and recovered more quickly from pheromone than did wild-type cells, which suggests that GPA1 may function in an adaptation response to pheromone.

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Costa, V. « Oxidative stress and signal transduction in Saccharomyces cerevisiae : insights into ageing, apoptosis and diseases ». Molecular Aspects of Medicine 22, n^o 4-5 (octobre 2001) : 217–46. http://dx.doi.org/10.1016/s0098-2997(01)00012-7.

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Gartner, A., K. Nasmyth et G. Ammerer. « Signal transduction in Saccharomyces cerevisiae requires tyrosine and threonine phosphorylation of FUS3 and KSS1. » Genes & ; Development 6, n^o 7 (1 juillet 1992) : 1280–92. http://dx.doi.org/10.1101/gad.6.7.1280.

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Vaseghi, Sam, Franz Macherhammer, Susanne Zibek et Matthias Reuss. « Signal Transduction Dynamics of the Protein Kinase-A/Phosphofructokinase-2 System in Saccharomyces cerevisiae ». Metabolic Engineering 3, n^o 2 (avril 2001) : 163–72. http://dx.doi.org/10.1006/mben.2000.0179.

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Sitcheran, Raquel, Roger Emter, Anastasia Kralli et Keith R. Yamamoto. « A Genetic Analysis of Glucocorticoid Receptor Signaling : Identification and Characterization of Ligand-Effect Modulators in Saccharomyces cerevisiae ». Genetics 156, n^o 3 (1 novembre 2000) : 963–72. http://dx.doi.org/10.1093/genetics/156.3.963.

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Abstract To find novel components in the glucocorticoid signal transduction pathway, we performed a yeast genetic screen to identify ligand-effect modulators (LEMs), proteins that modulate the cellular response to hormone. We isolated several mutants that conferred increased glucocorticoid receptor (GR) activity in response to dexamethasone and analyzed two of them in detail. These studies identify two genes, LEM3 and LEM4, which correspond to YNL323w and ERG6, respectively. LEM3 is a putative transmembrane protein of unknown function, and ERG6 is a methyltransferase in the ergosterol biosynthetic pathway. Analysis of null mutants indicates that LEM3 and ERG6 act at different steps in the GR signal transduction pathway.

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Johnston, M., et J. H. Kim. « Glucose as a hormone : receptor-mediated glucose sensing in the yeast Saccharomyces cerevisiae ». Biochemical Society Transactions 33, n^o 1 (1 février 2005) : 247–52. http://dx.doi.org/10.1042/bst0330247.

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Because glucose is the principal carbon and energy source for most cells, most organisms have evolved numerous and sophisticated mechanisms for sensing glucose and responding to it appropriately. This is especially apparent in the yeast Saccharomyces cerevisiae, where these regulatory mechanisms determine the distinctive fermentative metabolism of yeast, a lifestyle it shares with many kinds of tumour cells. Because energy generation by fermentation of glucose is inefficient, yeast cells must vigorously metabolize glucose. They do this, in part, by carefully regulating the first, rate-limiting step of glucose utilization: its transport. Yeast cells have learned how to sense the amount of glucose that is available and respond by expressing the most appropriate of its 17 glucose transporters. They do this through a signal transduction pathway that begins at the cell surface with the Snf3 and Rgt2 glucose sensors and ends in the nucleus with the Rgt1 transcription factor that regulates expression of genes encoding glucose transporters. We explain this glucose signal transduction pathway, and describe how it fits into a highly interconnected regulatory network of glucose sensing pathways that probably evolved to ensure rapid and sensitive response of the cell to changing levels of glucose.

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Lau, W.-T. Walter, Ken R. Schneider et Erin K. O’Shea. « A Genetic Study of Signaling Processes for Repression of PHO5 Transcription in Saccharomyces cerevisiae ». Genetics 150, n^o 4 (1 décembre 1998) : 1349–59. http://dx.doi.org/10.1093/genetics/150.4.1349.

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Abstract In the yeast Saccharomyces cerevisiae, transcription of a secreted acid phosphatase, PHO5, is repressed in response to high concentrations of extracellular inorganic phosphate. To investigate the signal transduction pathway leading to transcriptional regulation of PHO5, we carried out a genetic selection for mutants that express PHO5 constitutively. We then screened for mutants whose phenotypes are also dependent on the function of PHO81, which encodes an inhibitor of the Pho80p-Pho85p cyclin/cyclin-dependent kinase complex. These mutations are therefore likely to impair upstream functions in the signaling pathway, and they define five complementation groups. Mutations were found in a gene encoding a plasma membrane ATPase (PMA1), in genes required for the in vivo function of the phosphate transport system (PHO84 and PHO86), in a gene involved in the fatty acid synthesis pathway (ACC1), and in a novel, nonessential gene (PHO23). These mutants can be classified into two groups: pho84, pho86, and pma1 are defective in high-affinity phosphate uptake, whereas acc1 and pho23 are not, indicating that the two groups of mutations cause constitutive expression of PHO5 by distinct mechanisms. Our observations suggest that these gene products affect different aspects of the signal transduction pathway for PHO5 repression.

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Kim, Jeong-Ho, Valérie Brachet, Hisao Moriya et Mark Johnston. « Integration of Transcriptional and Posttranslational Regulation in a Glucose Signal Transduction Pathway in Saccharomyces cerevisiae ». Eukaryotic Cell 5, n^o 1 (janvier 2006) : 167–73. http://dx.doi.org/10.1128/ec.5.1.167-173.2006.

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ABSTRACT Expression of the HXT genes encoding glucose transporters in the budding yeast Saccharomyces cerevisiae is regulated by two interconnected glucose-signaling pathways: the Snf3/Rgt2-Rgt1 glucose induction pathway and the Snf1-Mig1 glucose repression pathway. The Snf3 and Rgt2 glucose sensors in the membrane generate a signal in the presence of glucose that inhibits the functions of Std1 and Mth1, paralogous proteins that regulate the function of the Rgt1 transcription factor, which binds to the HXT promoters. It is well established that glucose induces degradation of Mth1, but the fate of its paralogue Std1 has been less clear. We present evidence that glucose-induced degradation of Std1 via the SCFGrr1 ubiquitin-protein ligase and the 26S proteasome is obscured by feedback regulation of STD1 expression. Disappearance of Std1 in response to glucose is accelerated when glucose induction of STD1 expression due to feedback regulation by Rgt1 is prevented. The consequence of relieving feedback regulation of STD1 expression is that reestablishment of repression of HXT1 expression upon removal of glucose is delayed. In contrast, degradation of Mth1 is reinforced by glucose repression of MTH1 expression: disappearance of Mth1 is slowed when glucose repression of MTH1 expression is prevented, and this results in a delay in induction of HXT3 expression in response to glucose. Thus, the cellular levels of Std1 and Mth1, and, as a consequence, the kinetics of induction and repression of HXT gene expression, are closely regulated by interwoven transcriptional and posttranslational controls mediated by two different glucose-sensing pathways.

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Whiteway, M., L. Hougan, D. Dignard, L. BELL, G. Saari, F. Grant, P. O'Hara, V. L. MacKay et D. Y. Thomas. « Function of the STE4 and STE18 Genes in Mating Pheromone Signal Transduction in Saccharomyces cerevisiae ». Cold Spring Harbor Symposia on Quantitative Biology 53 (1 janvier 1988) : 585–90. http://dx.doi.org/10.1101/sqb.1988.053.01.067.

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Nishimura, Hiroshi, Yuko Kawasaki, Kazuto Nosaka et Yoshinobu Kaneko. « Mutation thi81 causing a deficiency in the signal transduction of thiamine pyrophosphate in Saccharomyces cerevisiae ». FEMS Microbiology Letters 156, n^o 2 (17 janvier 2006) : 245–49. http://dx.doi.org/10.1111/j.1574-6968.1997.tb12735.x.

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Suzuki-Fujimoto, T., M. Fukuma, K. I. Yano, H. Sakurai, A. Vonika, S. A. Johnston et T. Fukasawa. « Analysis of the galactose signal transduction pathway in Saccharomyces cerevisiae : interaction between Gal3p and Gal80p. » Molecular and Cellular Biology 16, n^o 5 (mai 1996) : 2504–8. http://dx.doi.org/10.1128/mcb.16.5.2504.

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The GAL3 gene plays a critical role in galactose induction of the GAL genes that encode galactose- metabolizing enzymes in Saccharomyces cerevisiae. Defects in GAL3 result in a long delay in GAL gene induction, and overproduction of Gal3p causes constitutive expression of GAL. Here we demonstrate that concomitant overproduction of the negative regulator, Gal80p, and Gal3p suppresses this constitutive GAL expression. This interplay between Gal80p and Gal3p is direct, as tagged Gal3p coimmunoprecipitated with Gal80p. The amount of coprecipitated Gal80p increased when GAL80 yeast cells were grown in the presence of galactose. When both GAL80 and GAL3 were overexpressed, the amount of coprecipitated Gal80p was not affected by galactose. Tagged gal3 mutant proteins bound to purified Gal80p, but only poorly in comparison with the wild type, suggesting that formation of the Gal80p-Gal3p complex depends on the normal function of Gal3p. Gal3p appeared larger in Western blots (immunoblots) than predicted by the published nucleic acid sequence. Reexamination of the DNA sequence of GAL3 revealed several mistakes, including an extension at the 3' end of another predicted 97 amino acids.

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Liang, H., et R. F. Gaber. « A novel signal transduction pathway in Saccharomyces cerevisiae defined by Snf3-regulated expression of HXT6. » Molecular Biology of the Cell 7, n^o 12 (décembre 1996) : 1953–66. http://dx.doi.org/10.1091/mbc.7.12.1953.

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We show that cells deleted for SNF3, HXT1, HXT2, HXT3, HXT4, HXT6, and HXT7 do not take up glucose and cannot grow on media containing glucose as a sole carbon source. The expression of Hxt1, Hxt2, Hxt3, Hxt6, or Gal2 in these cells resulted in glucose transport and allowed growth on glucose media. In contrast, the expression of Snf3 failed to confer glucose uptake or growth on glucose. HXT6 is highly expressed on raffinose, low glucose, or nonfermentable carbon sources but is repressed in the presence of high concentrations of glucose. The maintenance of HXT6 glucose repression is strictly dependent on Snf3 and not on intracellular glucose. In snf3 delta cells expression of HXT6 is constitutive even when the entire repertoire of HXT genes is present and glucose uptake is abundant. In addition, glucose repression of HXT6 does not require glucose uptake by HXT1, HXT2, HXT3 or HXT4. We show that a signal transduction pathway defined by the Snf3-dependent hexose regulation of HXT6 is distinct from but also overlaps with general glucose regulation pathways in Saccharomyces cerevisiae. Finally, glucose repression of ADH2 and SUC2 is intact in snf3 delta hxt1 delta hxt2 delta hxt3 delta hxt4 delta hxt6 delta hxt7 delta gal2 cells, suggesting that the sensing and signaling mechanism for general glucose repression is independent from glucose uptake.

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Zhou, Z., A. Gartner, R. Cade, G. Ammerer et B. Errede. « Pheromone-induced signal transduction in Saccharomyces cerevisiae requires the sequential function of three protein kinases. » Molecular and Cellular Biology 13, n^o 4 (avril 1993) : 2069–80. http://dx.doi.org/10.1128/mcb.13.4.2069.

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Protein phosphorylation plays an important role in pheromone-induced differentiation processes of haploid yeast cells. Among the components necessary for signal transduction are the STE7 and STE11 kinases and either one of the redundant FUS3 and KSS1 kinases. FUS3 and presumably KSS1 are phosphorylated and activated during pheromone induction by a STE7-dependent mechanism. Pheromone also induces the accumulation of STE7 in a hyperphosphorylated form. This modification of STE7 requires the STE11 kinase, which is proposed to act before STE7 during signal transmission. Surprisingly, STE7 hyperphosphorylation also requires a functional FUS3 (or KSS1) kinase. Using in vitro assays for FUS3 phosphorylation, we show that pheromone activates STE7 even in the absence of FUS3 and KSS1. Therefore, STE7 activation must precede modification of FUS3 (and KSS1). These findings suggest that STE7 hyperphosphorylation is a consequence of its activation but not the determining event.

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Bhat, P. J., D. Oh et J. E. Hopper. « Analysis of the GAL3 signal transduction pathway activating GAL4 protein-dependent transcription in Saccharomyces cerevisiae. » Genetics 125, n^o 2 (1 juin 1990) : 281–91. http://dx.doi.org/10.1093/genetics/125.2.281.

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Abstract The Saccharomyces cerevisiae GAL/MEL regulon genes are normally induced within minutes of galactose addition, but gal3 mutants exhibit a 3-5-day induction lag. We have discovered that this long-term adaptation (LTA) phenotype conferred by gal3 is complemented by multiple copies of the GAL1 gene. Based on this result and the striking similarity between the GAL3 and GAL1 protein sequences we attempted to detect galactokinase activity that might be associated with the GAL3 protein. By both in vivo and in vitro tests the GAL3 gene product does not appear to catalyze a galactokinase-like reaction. In complementary experiments, Escherichia coli galactokinase expressed in yeast was shown to complement the gal1 but not the gal3 mutation. Thus, the complementation activity provided by GAL1 is not likely due to galactokinase activity, but rather due to a distinct GAL3-like activity. Overall, the results indicate that GAL1 encodes a bifunctional protein. In related experiments we tested for function of the LTA induction pathway in gal3 cells deficient for other gene functions. It has been known for some time that gal3gal1, gal3gal7, gal3gal10, and gal3 rho- are incapable of induction. We constructed isogenic haploid strains bearing the gal3 mutation in combination with either gal15 or pgi1 mutations: the gal15 and pgi1 blocks are not specific for the galactose pathway in contrast to the gal1, gal7 and gal10 blocks. The gal3gal5 and gal3pgi1 double mutants were not inducible, whereas both the gal5 and pgi1 single mutants were inducible. We conclude that, in addition to the GAL3-like activity of GAL1, functions beyond the galactose-specific GAL1, GAL7 and GAL10 enzymes are required for the LTA induction pathway.

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Zhou, Z., A. Gartner, R. Cade, G. Ammerer et B. Errede. « Pheromone-induced signal transduction in Saccharomyces cerevisiae requires the sequential function of three protein kinases ». Molecular and Cellular Biology 13, n^o 4 (avril 1993) : 2069–80. http://dx.doi.org/10.1128/mcb.13.4.2069-2080.1993.

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Protein phosphorylation plays an important role in pheromone-induced differentiation processes of haploid yeast cells. Among the components necessary for signal transduction are the STE7 and STE11 kinases and either one of the redundant FUS3 and KSS1 kinases. FUS3 and presumably KSS1 are phosphorylated and activated during pheromone induction by a STE7-dependent mechanism. Pheromone also induces the accumulation of STE7 in a hyperphosphorylated form. This modification of STE7 requires the STE11 kinase, which is proposed to act before STE7 during signal transmission. Surprisingly, STE7 hyperphosphorylation also requires a functional FUS3 (or KSS1) kinase. Using in vitro assays for FUS3 phosphorylation, we show that pheromone activates STE7 even in the absence of FUS3 and KSS1. Therefore, STE7 activation must precede modification of FUS3 (and KSS1). These findings suggest that STE7 hyperphosphorylation is a consequence of its activation but not the determining event.

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Holley, S. J., et K. R. Yamamoto. « A role for Hsp90 in retinoid receptor signal transduction. » Molecular Biology of the Cell 6, n^o 12 (décembre 1995) : 1833–42. http://dx.doi.org/10.1091/mbc.6.12.1833.

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The ubiquitous heat shock protein Hsp90 appears to participate directly in the function of a broad range of cellular signal transduction components, including steroid hormone receptors; however, an evolutionarily related subclass of intracellular receptors, exemplified by the retinoid receptors RAR and RXR, had been inferred from biochemical studies to function independently of Hsp90. To examine this issue genetically, we measured mammalian and avian retinoid receptor activity in a Saccharomyces cerevisiae strain in which the expression of the yeast Hsp90 homologue could be conditionally repressed approximately 20-fold relative to wild type. We tested transcriptional activation by RAR or RXR-RAR, from two types of retinoic acid response elements, triggered by three different agonist ligands. In every condition, we found that activation was severely compromised under conditions of low Hsp90 expression. We showed that the defect was in signal transduction rather than transcription activation per se, and that high affinity hormone binding was abolished in extracts of cells producing low levels of Hsp90. We suggest that Hsp90 may function in at least one step of signal transduction by all members of the intracellular receptor superfamily.

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Whiteway, Malcolm, Daniel Dignard et David Y. Thomas. « Mutagenesis of Ste18, a putative Gγ subunit in the Saccharomyces cerevisiae pheromone response pathway ». Biochemistry and Cell Biology 70, n^o 10-11 (1 octobre 1992) : 1230–37. http://dx.doi.org/10.1139/o92-169.

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The yeast STE18 gene product has sequence and functional similarity to the γ subunits of G proteins. The cloned STE18 gene was subjected to a saturation mutagenesis using doped oligonucleotides. The populations of mutant genes were screened for two classes of STE18 mutations, those that allowed for increased mating of a strain containing a defective STE4 gene (compensators) and those that inhibited mating even in the presence of a functional STE18 gene (dominant negatives). Three amino acid substitutions that enhanced mating in a specific STE4 (Gβ) point mutant background were identified. These compensatory mutations were allele specific and had no detectable phenotype of their own; they may define residues that mediate an association between the Gβ and Gγ subunits or in the association of the Gβγ subunit with other components of the signalling pathway. Several dominant negative mutations were also identified, including two C terminal truncations. These mutant proteins were unable to function in signal transduction by themselves, but they prevented signal transduction mediated by pheromone, as well as the constitutive signalling which is present in cells defective in the GPAI (Gα) gene. These mutant proteins may sequester Gβ or some other component of the signalling machinery in a nonfunctional complex. Key wordsi yeast, G protein, STE18, mutagenesis, pheromone response.

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Cutler, N. Shane, Xuewen Pan, Joseph Heitman et Maria E. Cardenas. « The TOR Signal Transduction Cascade Controls Cellular Differentiation in Response to Nutrients ». Molecular Biology of the Cell 12, n^o 12 (décembre 2001) : 4103–13. http://dx.doi.org/10.1091/mbc.12.12.4103.

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Rapamycin binds and inhibits the Tor protein kinases, which function in a nutrient-sensing signal transduction pathway that has been conserved from the yeast Saccharomyces cerevisiaeto humans. In yeast cells, the Tor pathway has been implicated in regulating cellular responses to nutrients, including proliferation, translation, transcription, autophagy, and ribosome biogenesis. We report here that rapamycin inhibits pseudohyphal filamentous differentiation of S. cerevisiae in response to nitrogen limitation. Overexpression of Tap42, a protein phosphatase regulatory subunit, restored pseudohyphal growth in cells exposed to rapamycin. The tap42-11 mutation compromised pseudohyphal differentiation and rendered it resistant to rapamycin. Cells lacking the Tap42-regulated protein phosphatase Sit4 exhibited a pseudohyphal growth defect and were markedly hypersensitive to rapamycin. Mutations in other Tap42-regulated phosphatases had no effect on pseudohyphal differentiation. Our findings support a model in which pseudohyphal differentiation is controlled by a nutrient-sensing pathway involving the Tor protein kinases and the Tap42–Sit4 protein phosphatase. Activation of the MAP kinase or cAMP pathways, or mutation of the Sok2 repressor, restored filamentation in rapamycin treated cells, supporting models in which the Tor pathway acts in parallel with these known pathways. Filamentous differentiation of diverse fungi was also blocked by rapamycin, demonstrating that the Tor signaling cascade plays a conserved role in regulating filamentous differentiation in response to nutrients.

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Gerst, J. E., K. Ferguson, A. Vojtek, M. Wigler et J. Field. « CAP is a bifunctional component of the Saccharomyces cerevisiae adenylyl cyclase complex. » Molecular and Cellular Biology 11, n^o 3 (mars 1991) : 1248–57. http://dx.doi.org/10.1128/mcb.11.3.1248.

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CAP, a protein from Saccharomyces cerevisiae that copurifies with adenylyl cyclase, appears to be required for yeast cells to be fully responsive to RAS proteins. CAP also appears to be required for normal cell morphology and responsiveness to nutrient deprivation and excess. We describe here a molecular and phenotypic analysis of the CAP protein. The N-terminal domain is necessary and sufficient for cellular response to activated RAS protein, while the C-terminal domain is necessary and sufficient for normal cellular morphology and responses to nutrient extremes. Thus, CAP is a novel example of a bifunctional component involved in the regulation of diverse signal transduction pathways.

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Gerst, J. E., K. Ferguson, A. Vojtek, M. Wigler et J. Field. « CAP is a bifunctional component of the Saccharomyces cerevisiae adenylyl cyclase complex ». Molecular and Cellular Biology 11, n^o 3 (mars 1991) : 1248–57. http://dx.doi.org/10.1128/mcb.11.3.1248-1257.1991.

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CAP, a protein from Saccharomyces cerevisiae that copurifies with adenylyl cyclase, appears to be required for yeast cells to be fully responsive to RAS proteins. CAP also appears to be required for normal cell morphology and responsiveness to nutrient deprivation and excess. We describe here a molecular and phenotypic analysis of the CAP protein. The N-terminal domain is necessary and sufficient for cellular response to activated RAS protein, while the C-terminal domain is necessary and sufficient for normal cellular morphology and responses to nutrient extremes. Thus, CAP is a novel example of a bifunctional component involved in the regulation of diverse signal transduction pathways.

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Yashar, B., K. Irie, J. A. Printen, B. J. Stevenson, G. F. Sprague, K. Matsumoto et B. Errede. « Yeast MEK-dependent signal transduction : response thresholds and parameters affecting fidelity. » Molecular and Cellular Biology 15, n^o 12 (décembre 1995) : 6545–53. http://dx.doi.org/10.1128/mcb.15.12.6545.

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Ste7p and Mkk1p are MEK (MAPK/ERK kinase) family members that function in the mating and cell integrity signal transduction pathways in Saccharomyces cerevisiae. We selected STE7 and MKK1 mutations that stimulated their respective pathways in the absence of an inductive signal. Strikingly, serine-to-proline substitutions at analogous positions in Ste7p (position 368) and Mkk1p (position 386) were recovered by independent genetic screens. Such an outcome suggests that this substitution in other MEKs would exhibit similar properties. The Ste7p-P368 variant has higher basal enzymatic activity than Ste7p but still requires induction to reach full activation. The higher activity associated with Ste7p-P368 allows it to compensate for defects in the cell integrity pathway, but it does so only when it is overproduced or when Ste5p is missing. This behavior suggests that Ste5p, which has been proposed to be a tether for the kinases in the mating pathway, contributes to Ste7p specificity.

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Neiman, A. M., B. J. Stevenson, H. P. Xu, G. F. Sprague, I. Herskowitz, M. Wigler et S. Marcus. « Functional homology of protein kinases required for sexual differentiation in Schizosaccharomyces pombe and Saccharomyces cerevisiae suggests a conserved signal transduction module in eukaryotic organisms. » Molecular Biology of the Cell 4, n^o 1 (janvier 1993) : 107–20. http://dx.doi.org/10.1091/mbc.4.1.107.

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We present genetic evidence that three presumptive protein kinases of Schizosaccharomyces pombe, byr2, byr1, and spk1 that are structurally related to protein kinases of Saccharomyces cerevisiae, STE11, STE7, and FUS3, respectively, are also functionally related. In some cases, introduction of the heterologous protein kinase into a mutant was sufficient for complementation. In other cases (as in a ste11- mutant of S. cerevisiae), expression of two S. pombe protein kinases (byr2 and byr1) was required to observe complementation, suggesting that byr2 and byr1 act cooperatively. Complementation in S. pombe mutants is observed as restoration of sporulation and conjugation and in S. cerevisiae as restoration of conjugation, pheromone-induced cell cycle arrest, and pheromone-induced transcription of the FUS1 gene. We also show that the S. pombe kinases bear a similar relationship to the mating pheromone receptor apparatus as do their S. cerevisiae counterparts. Our results indicate that pheromone-induced signal transduction employs a conserved set of kinases in these two evolutionarily distant yeasts despite an apparently significant difference in function of the heterotrimeric G proteins. We suggest that the STE11/byr2, STE7/byr1, and FUS3/spk1 kinases comprise a signal transduction module that may be conserved in higher eukaryotes. Consistent with this hypothesis, we show that a mammalian mitogen-activated protein (MAP) kinase, ERK2, can partially replace spk1 function in S. pombe.

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Fujimura, H. A. « The yeast G-protein homolog is involved in the mating pheromone signal transduction system. » Molecular and Cellular Biology 9, n^o 1 (janvier 1989) : 152–58. http://dx.doi.org/10.1128/mcb.9.1.152.

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I have isolated a new type of sterile mutant of Saccharomyces cerevisiae, carrying a single mutant allele, designated dac1, which was mapped near the centromere on chromosome VIII. The dac1 mutation caused specific defects in the pheromone responsiveness of both a and alpha cells and did not seem to be associated with any pleiotropic phenotypes. Thus, in contrast to the ste4, ste5, ste7, ste11, and ste12 mutations, the dac1 mutation had no significant effect on such constitutive functions of haploid cells as pheromone production and alpha-factor destruction. The characteristics of this phenotype suggest that the DAC1 gene encodes a component of the pheromone response pathway common to both a and alpha cells. Introduction of the GPA1 gene encoding an S. cerevisiae homolog of the alpha subunit of mammalian guanine nucleotide-binding regulatory proteins (G proteins) into sterile dac1 mutants resulted in restoration of pheromone responsiveness and mating competence to both a and alpha cells. These results suggest that the dac1 mutation is an allele of the GPA1 gene and thus provide genetic evidence that the yeast G protein homolog is directly involved in the mating pheromone signal transduction pathway.

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Fujimura, H. A. « The yeast G-protein homolog is involved in the mating pheromone signal transduction system ». Molecular and Cellular Biology 9, n^o 1 (janvier 1989) : 152–58. http://dx.doi.org/10.1128/mcb.9.1.152-158.1989.

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I have isolated a new type of sterile mutant of Saccharomyces cerevisiae, carrying a single mutant allele, designated dac1, which was mapped near the centromere on chromosome VIII. The dac1 mutation caused specific defects in the pheromone responsiveness of both a and alpha cells and did not seem to be associated with any pleiotropic phenotypes. Thus, in contrast to the ste4, ste5, ste7, ste11, and ste12 mutations, the dac1 mutation had no significant effect on such constitutive functions of haploid cells as pheromone production and alpha-factor destruction. The characteristics of this phenotype suggest that the DAC1 gene encodes a component of the pheromone response pathway common to both a and alpha cells. Introduction of the GPA1 gene encoding an S. cerevisiae homolog of the alpha subunit of mammalian guanine nucleotide-binding regulatory proteins (G proteins) into sterile dac1 mutants resulted in restoration of pheromone responsiveness and mating competence to both a and alpha cells. These results suggest that the dac1 mutation is an allele of the GPA1 gene and thus provide genetic evidence that the yeast G protein homolog is directly involved in the mating pheromone signal transduction pathway.

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Henry, Theresa C., Juliette E. Power, Christine L. Kerwin, Aishat Mohammed, Jonathan S. Weissman, Dale M. Cameron et Dennis D. Wykoff. « Systematic Screen of Schizosaccharomyces pombe Deletion Collection Uncovers Parallel Evolution of the Phosphate Signal Transduction Pathway in Yeasts ». Eukaryotic Cell 10, n^o 2 (17 décembre 2010) : 198–206. http://dx.doi.org/10.1128/ec.00216-10.

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ABSTRACT The phosphate signal transduction (PHO) pathway, which regulates genes in response to phosphate starvation, is well defined in Saccharomyces cerevisiae . We asked whether the PHO pathway was the same in the distantly related fission yeast Schizosaccharomyces pombe . We screened a deletion collection for mutants aberrant in phosphatase activity, which is primarily a consequence of pho1 + transcription. We identified a novel zinc finger-containing protein (encoded by spbc27b12.11c + ), which we have named pho7 + , that is essential for pho1 + transcriptional induction during phosphate starvation. Few of the S. cerevisiae genes involved in the PHO pathway appear to be involved in the regulation of the phosphate starvation response in S. pombe . Only the most upstream genes in the PHO pathway in S. cerevisiae ( ADO1 , DDP1 , and PPN1 ) share a similar role in both yeasts. Because ADO1 and DDP1 regulate ATP and IP 7 levels, we hypothesize that the ancestor of these yeasts must have sensed similar metabolites in response to phosphate starvation but have evolved distinct mechanisms in parallel to sense these metabolites and induce phosphate starvation genes.

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Horecka, Joe, et George F. Sprague. « Identification and Characterization of FAR3, a Gene Required for Pheromone-Mediated G1 Arrest in Saccharomyces cerevisiae ». Genetics 144, n^o 3 (1 novembre 1996) : 905–21. http://dx.doi.org/10.1093/genetics/144.3.905.

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Abstract In haploid Saccharomyces cerevisiae cells, mating pheromones activate a signal transduction pathway that leads to cell cycle arrest in the G1 phase and to transcription induction of genes that promote conjugation. To identify genes that link the signal transduction pathway and the cell cycle machinery, we developed a selection strategy to isolate yeast mutants specifically defective for G1 arrest. Several of these mutants identified previously known genes, including CLN3, FUS3, and FAR1. In addition, a new gene, FAR3, was identified and characterized. FAR3 encodes a novel protein of 204 amino acid residues that is dispensable for viability. Northern blot experiments indicated that FAR3 expression is constitutive with respect to cell type, pheromone treatment, and cell cycle position. As a first step toward elucidating the mechanism by which Far3 promotes pheromone-mediated G1 arrest, we performed genetic and molecular experiments to test the possibility that Far3 participates in one of the heretofore characterized mechanisms, namely Fus3/Farl-mediated inhibition of Cdc28-Cln kinase activity, G1 cyclin gene repression, and G1, cyclin protein turnover. Our data indicate that Far3 effects G1 arrest by a mechanism distinct from those previously known.

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Styrkársdóttir, Unnur, Richard Egel et Olaf Nielsen. « Functional conservation between Schizosaccharomyces pombe ste8 and Saccharomyces cerevisiae STE11 protein kinases in yeast signal transduction ». Molecular and General Genetics MGG 235, n^o 1 (octobre 1992) : 122–30. http://dx.doi.org/10.1007/bf00286189.

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Sadhu, C., D. Hoekstra, M. J. McEachern, S. I. Reed et J. B. Hicks. « A G-protein alpha subunit from asexual Candida albicans functions in the mating signal transduction pathway of Saccharomyces cerevisiae and is regulated by the a1-alpha 2 repressor. » Molecular and Cellular Biology 12, n^o 5 (mai 1992) : 1977–85. http://dx.doi.org/10.1128/mcb.12.5.1977.

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We have isolated a gene, designated CAG1, from Candida albicans by using the G-protein alpha-subunit clone SCG1 of Saccharomyces cerevisiae as a probe. Amino acid sequence comparison revealed that CAG1 is more homologous to SCG1 than to any other G protein reported so far. Homology between CAG1 and SCG1 not only includes the conserved guanine nucleotide binding domains but also spans the normally variable regions which are thought to be involved in interaction with the components of the specific signal transduction pathway. Furthermore, CAG1 contains a central domain, previously found only in SCG1. cag1 null mutants of C. albicans created by gene disruption produced no readily detectable phenotype. The C. albicans CAG1 gene complemented both the growth and mating defects of S. cerevisiae scg1 null mutants when carried on either a low- or high-copy-number plasmid. In diploid C. albicans, the CAG1 transcript was readily detectable in mycelial and yeast cells of both the white and opaque forms. However, the CAG1-specific transcript in S. cerevisiae transformants containing the C. albicans CAG1 gene was observed only in haploid cells. This transcription pattern matches that of SCG1 in S. cerevisiae and is caused by a1-alpha 2 mediated repression in diploid cells. That is, CAG1 behaves as a haploid-specific gene in S. cerevisiae, subject to control by the a1-alpha 2 mating-type regulation pathway. We infer from these results that C. albicans may have a signal transduction system analogous to that controlling mating type in S. cerevisiae or possibly even a sexual pathway that has so far remained undetected.

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Sadhu, C., D. Hoekstra, M. J. McEachern, S. I. Reed et J. B. Hicks. « A G-protein alpha subunit from asexual Candida albicans functions in the mating signal transduction pathway of Saccharomyces cerevisiae and is regulated by the a1-alpha 2 repressor ». Molecular and Cellular Biology 12, n^o 5 (mai 1992) : 1977–85. http://dx.doi.org/10.1128/mcb.12.5.1977-1985.1992.

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We have isolated a gene, designated CAG1, from Candida albicans by using the G-protein alpha-subunit clone SCG1 of Saccharomyces cerevisiae as a probe. Amino acid sequence comparison revealed that CAG1 is more homologous to SCG1 than to any other G protein reported so far. Homology between CAG1 and SCG1 not only includes the conserved guanine nucleotide binding domains but also spans the normally variable regions which are thought to be involved in interaction with the components of the specific signal transduction pathway. Furthermore, CAG1 contains a central domain, previously found only in SCG1. cag1 null mutants of C. albicans created by gene disruption produced no readily detectable phenotype. The C. albicans CAG1 gene complemented both the growth and mating defects of S. cerevisiae scg1 null mutants when carried on either a low- or high-copy-number plasmid. In diploid C. albicans, the CAG1 transcript was readily detectable in mycelial and yeast cells of both the white and opaque forms. However, the CAG1-specific transcript in S. cerevisiae transformants containing the C. albicans CAG1 gene was observed only in haploid cells. This transcription pattern matches that of SCG1 in S. cerevisiae and is caused by a1-alpha 2 mediated repression in diploid cells. That is, CAG1 behaves as a haploid-specific gene in S. cerevisiae, subject to control by the a1-alpha 2 mating-type regulation pathway. We infer from these results that C. albicans may have a signal transduction system analogous to that controlling mating type in S. cerevisiae or possibly even a sexual pathway that has so far remained undetected.

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Biswas, Subhrajit, Patrick Van Dijck et Asis Datta. « Environmental Sensing and Signal Transduction Pathways Regulating Morphopathogenic Determinants of Candida albicans ». Microbiology and Molecular Biology Reviews 71, n^o 2 (juin 2007) : 348–76. http://dx.doi.org/10.1128/mmbr.00009-06.

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SUMMARY Candida albicans is an opportunistic fungal pathogen that is found in the normal gastrointestinal flora of most healthy humans. However, under certain environmental conditions, it can become a life-threatening pathogen. The shift from commensal organism to pathogen is often correlated with the capacity to undergo morphogenesis. Indeed, under certain conditions, including growth at ambient temperature, the presence of serum or N-acetylglucosamine, neutral pH, and nutrient starvation, C. albicans can undergo reversible transitions from the yeast form to the mycelial form. This morphological plasticity reflects the interplay of various signal transduction pathways, either stimulating or repressing hyphal formation. In this review, we provide an overview of the different sensing and signaling pathways involved in the morphogenesis and pathogenesis of C. albicans. Where appropriate, we compare the analogous pathways/genes in Saccharomyces cerevisiae in an attempt to highlight the evolution of the different components of the two organisms. The downstream components of these pathways, some of which may be interesting antifungal targets, are also discussed.

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CHEN, AIMIN, JIAJUN ZHANG, ZHANJIANG YUAN et TIANSHOU ZHOU. « NOISE-INDUCED ALTERNATIVE RESPONSE IN MAP KINASE PATHWAYS WITH MUTUAL INHIBITION ». Journal of Biological Systems 17, n^o 01 (mars 2009) : 125–40. http://dx.doi.org/10.1142/s021833900900282x.

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All organisms have the ability to detect and respond to changes in the environment for survival, and as a result, specific cellular signaling pathways have evolved by which organisms sense their environment and respond to signals that they detect. However, an important unsolved problem in cell biology is to understand how specificity from signal to cellular response is maintained between different signal transduction pathways that share similar or identical components. Here, we show, using mathematical and computational modeling, that two typical signaling pathways in a single cell, hyperosmolar and pheromone motigen-avtivated protein kinase in the yeast Saccharomyces cerevisiae with mutual inhibition, can respond alternatively to two costimulated signals in a stochastically fluctuated environment. Within a bistable region over two input signals, noise plays an essential role in achieving specificity of response, while outside it, these pathways achieve specificity by filtering out spurious crosstalk through mutual inhibition.

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Schrick, Kathrin, Barbara Garvik et Leland H. Hartwell. « Mating in Saccharomyces cerevisiae : The Role of the Pheromone Signal Transduction Pathway in the Chemotropic Response to Pheromone ». Genetics 147, n^o 1 (1 septembre 1997) : 19–32. http://dx.doi.org/10.1093/genetics/147.1.19.

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Abstract The mating process in yeast has two distinct aspects. One is the induction and activation of proteins required for cell fusion in response to a pheromone signal; the other is chemotropism, i.e., detection of a pheromone gradient and construction of a fusion site available to the signaling cell. To determine whether components of the signal transduction pathway necessary for transcriptional activation also play a role in chemotropism, we examined strains with null mutations in components of the signal transduction pathway for diploid formation, prezygote formation and the chemotropic process of mating partner discrimination when transcription was induced downstream of the mutation. Cells mutant for components of the mitogen-activated protein (MAP) kinase cascade (ste5, ste20, ste11, ste7 or fus3 kss1) formed diploids at a frequency 1% that of the wild-type control, but formed prezygotes as efficiently as the wild-type control and showed good mating partner discrimination, suggesting that the MAP kinase cascade is not essential for chemotropism. In contrast, cells mutant for the receptor (ste2) or the β or γ subunit (ste4 and stel8) of the G protein were extremely defective in both diploid and prezygote formation and discriminated poorly between signaling and nonsignaling mating partners, implying that these components are important for chemotropism.

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