The SIT4 protein phosphatase functions in late G1 for progression into S phase.
Saccharomyces cerevisiae strains containing temperature-sensitive mutations in the SIT4 protein phosphatase arrest in late G1 at the nonpermissive temperature. Order-of-function analysis shows that SIT4 is required in late G1 for progression into S phase. While the levels of SIT4 do not change in the cell cycle, SIT4 associates with two ... high-molecular-weight phosphoproteins in a cell-cycle-dependent fashion. In addition, we have identified a polymorphic gene, SSD1, that in some versions can suppress the lethality due to a deletion of SIT4 and can also partially suppress the phenotypic defects due to a null mutation in BCY1. The SSD1 protein is implicated in G1 control and has a region of similarity to the dis3 protein of Schizosaccharomyces pombe. We have also identified a gene, PPH2alpha, that in high copy number can partially suppress the growth defect of sit4 strains. The PPH2 alpha gene encodes a predicted protein that is 80% identical to the catalytic domain of mammalian type 2A protein phosphatases but also has an acidic amino-terminal extension not present in other phosphatases.
Mesh Terms:
Amino Acid Sequence, Base Sequence, Cytoplasm, Fluorescent Antibody Technique, G1 Phase, Genes, Molecular Sequence Data, Molecular Weight, Mutation, Phenotype, Phosphoprotein Phosphatases, Polymorphism, Genetic, Precipitin Tests, Protein Phosphatase 2, S Phase, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Nucleic Acid, Temperature
Amino Acid Sequence, Base Sequence, Cytoplasm, Fluorescent Antibody Technique, G1 Phase, Genes, Molecular Sequence Data, Molecular Weight, Mutation, Phenotype, Phosphoprotein Phosphatases, Polymorphism, Genetic, Precipitin Tests, Protein Phosphatase 2, S Phase, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Homology, Nucleic Acid, Temperature
Mol. Cell. Biol.
Date: Apr. 01, 1991
PubMed ID: 1848673
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