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
Mol. Cell. Biol.
Date: Apr. 01, 1991
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