Saccharomyces cerevisiae Homologs of Mammalian B and B′ Subunits of Protein Phosphatase 2A Direct the Enzyme to Distinct Cellular Functions

Protein phosphatase 2A (PP2A) is a major cellular serine/threonine protein phosphatase, present in the cell in a variety of heterotrimeric forms that differ in their associated regulatory B-subunit. Cloning of the mammalian B′ subunit has allowed the identification of a highly homologous Saccharomyc...

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Bibliographic Details
Published in:The Journal of biological chemistry 1997-03, Vol.272 (13), p.8256-8262
Main Authors: Zhao, Yu, Boguslawski, George, Zitomer, Richard S., DePaoli-Roach, Anna A.
Format: Article
Language:English
Subjects:
Animals
Blotting, Western
DNA, Complementary - chemistry
Electrophoresis, Polyacrylamide Gel
Mutagenesis
Phenotype
Phosphoprotein Phosphatases - chemistry
Phosphoprotein Phosphatases - genetics
Phosphoprotein Phosphatases - metabolism
Protein Conformation
Protein Phosphatase 2
Rabbits
Saccharomyces cerevisiae - enzymology
Saccharomyces cerevisiae - genetics
Temperature
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Summary:Protein phosphatase 2A (PP2A) is a major cellular serine/threonine protein phosphatase, present in the cell in a variety of heterotrimeric forms that differ in their associated regulatory B-subunit. Cloning of the mammalian B′ subunit has allowed the identification of a highly homologous Saccharomyces cerevisiae gene, RTS1. Disruption of the gene results in a temperature-sensitive growth defect that can be suppressed by expression of rabbit B′α or B′γ isoforms. The B′α subunit is much more effective in restoring normal growth at 37 °C than B′γ. Immunoprecipitated Rts1p was found associated with type 2A-specific protein phosphatase activity that is sensitive to 2 nM okadaic acid, but not to 100 nM phosphatase inhibitor-2, and to be phosphorylated in vivo. However, overexpression of RTS1 was unable to suppress the cold sensitivity, defective cytokinesis, and abnormal cell morphology resulting from defects in the CDC55 gene, which encodes the yeast homolog of a different B subunit of another form of 2A phosphatase, PP2A1. These results indicate that Rts1p is a yeast homolog of the mammalian B′ subunit and that the various regulatory B-subunits of PP2A are not functionally redundant but direct the enzyme to distinct cellular functions.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.272.13.8256