Abstract
Pheromone signalling in Saccharomyces cerevisiae is mediated by the STE4-STE18 G-protein beta gamma subunits. A possible target for the subunits is Ste20p, whose structural homolog, the serine/threonine kinase PAK, is activated by GTP-binding p21s Cdc42 and Rac1. The putative Cdc42p-binding domain of Ste20p, expressed as a fusion protein, binds human and yeast GTP-binding Cdc42p. Cdc42p is required for alpha-factor-induced activation of FUS1.cdc24ts strains defective for Cdc42p GDP/GTP exchange show no pheromone induction at restrictive temperatures but are partially rescued by overexpression of Cdc42p, which is potentiated by Cdc42p12V mutants. Epistatic analysis indicates that CDC24 and CDC42 lie between STE4 and STE20 in the pathway. The two-hybrid system revealed that Ste4p interacts with Cdc24p. We propose that Cdc42p plays a pivotal role both in polarization of the cytoskeleton and in pheromone signalling.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Base Sequence
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Cell Cycle Proteins / metabolism*
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Epistasis, Genetic
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Fungal Proteins / genetics
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GTP-Binding Protein beta Subunits*
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism*
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Genes, Fungal
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Guanine Nucleotide Exchange Factors*
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Heterotrimeric GTP-Binding Proteins*
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Humans
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Intracellular Signaling Peptides and Proteins
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MAP Kinase Kinase Kinases
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Mating Factor
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Membrane Proteins
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Molecular Sequence Data
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Peptides / metabolism
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Peptides / pharmacology
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Pheromones / metabolism*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism
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Proto-Oncogene Proteins / metabolism*
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Recombinant Fusion Proteins / biosynthesis
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Saccharomyces cerevisiae / physiology*
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Saccharomyces cerevisiae Proteins*
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Sequence Alignment
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Signal Transduction / physiology*
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Transcriptional Activation / drug effects
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cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
Substances
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CDC24 protein, S cerevisiae
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Cell Cycle Proteins
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FUS1 protein, S cerevisiae
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Fungal Proteins
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GTP-Binding Protein beta Subunits
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Guanine Nucleotide Exchange Factors
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Intracellular Signaling Peptides and Proteins
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Membrane Proteins
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Peptides
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Pheromones
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Proto-Oncogene Proteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Ste4 protein, S cerevisiae
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Mating Factor
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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MAP Kinase Kinase Kinases
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STE20 protein, S cerevisiae
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GTP-Binding Proteins
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Heterotrimeric GTP-Binding Proteins
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cdc42 GTP-Binding Protein, Saccharomyces cerevisiae