The SAP, a new family of proteins, associate and function positively with the SIT4 phosphatase

Luke, M. M., Della Seta, F., Di Como, C. J., Sugimoto, H., Kobayashi, R., Arndt, K. T. (June 1996) The SAP, a new family of proteins, associate and function positively with the SIT4 phosphatase. Molecular and Cellular Biology, 16 (6). pp. 2744-55. ISSN 0270-7306



SIT4 is the catalytic subunit of a type 2A-related protein phosphatase in Saccharomyces cerevisiae that is required for G1 cyclin transcription and for bud formation. SIT4 associates with several high-molecular-mass proteins in a cell cycle-dependent fashion. We purified two SIT4-associated proteins, SAP155 and SAP190, and cloned the corresponding genes. By sequence homology, we isolated two additional SAP genes, SAP185 and SAP4. Through such an association is not yet proven for SAP4, each of SAP155, SAP185, and SAP190 physically associates with SIT4 in separate complexes. The SAPs function positively with SIT4, and by several criteria, the loss of all four SAPs is equivalent to the loss of SIT4. The data suggest that the SAPs are not functional in the absence of SIT4 and likewise that SIT4 is not functional in the absence of the SAPs. The SAPs are hyperphoshorylated in cells lacking SIT4, raising the possibility that the SAPs are substrates of SIT4. By sequence similarity, the SAPs fall into two groups, the SAP4/SAP155 group and the SAP185/SAP190 group. Overexpression of a SAP from one group does not suppress the defects due to the loss of the other group. These findings and others indicate that the SAPs have distinct functions.

Item Type: Paper
Uncontrolled Keywords: Amino Acid Sequence Base Sequence Cell Cycle/genetics/physiology Cloning, Molecular DNA Primers/genetics DNA, Fungal/genetics Fungal Proteins/chemistry/genetics/ metabolism Gene Deletion Gene Expression Genes, Fungal Models, Biological Molecular Sequence Data Phenotype Phosphoprotein Phosphatase/chemistry/genetics/ metabolism Protein Conformation Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Saccharomyces cerevisiae/cytology/genetics/metabolism Sequence Homology, Amino Acid Substrate Specificity Temperature
Subjects: organism description > yeast > Saccharomyces
organs, tissues, organelles, cell types and functions > cell types and functions > cell functions > cell cycle
Investigative techniques and equipment > cloning
Investigative techniques and equipment > assays > cloning
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > genes, structure and function > gene expression
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > enzymes > protein phosphatase
CSHL Authors:
Communities: CSHL labs > Kobayashi lab
Depositing User: Kathleen Darby
Date: June 1996
Date Deposited: 13 May 2014 16:20
Last Modified: 13 May 2014 16:20
PMCID: PMC231265
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