Saccharomyces cerevisiae homologs of mammalian B and B' subunits of protein phosphatase 2A direct the enzyme to distinct cellular functions

Yu Zhao, George Boguslawski, Richard S. Zitomer, Anna A. DePaoli-Roach

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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.

Original languageEnglish (US)
Pages (from-to)8256-8262
Number of pages7
JournalJournal of Biological Chemistry
Issue number13
StatePublished - Mar 28 1997


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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