PMID:12388751

Citation	Gentry, MS and Hallberg, RL (2002) Localization of Saccharomyces cerevisiae protein phosphatase 2A subunits throughout mitotic cell cycle. Mol. Biol. Cell 13:3477-92
Abstract	Protein phosphatase 2A (PP2A) regulates a broad spectrum of cellular processes. This enzyme is a collection of varied heterotrimeric complexes, each composed of a catalytic (C) and regulatory (B) subunit bound together by a structural (A) subunit. To understand the cell cycle dynamics of this enzyme population, we carried out quantitative and qualitative analyses of the PP2A subunits of Saccharomyces cerevisiae. We found the following: the level of each subunit remained constant throughout the cell cycle; there is at least 10 times more of one of the regulatory subunits (Rts1p) than the other (Cdc55p); Tpd3p, the structural subunit, is limiting for both catalytic and regulatory subunit binding. Using green fluorescent protein-tagged forms of each subunit, we monitored the sites of significant accumulation of each protein throughout the cell cycle. The two regulatory subunits displayed distinctly different dynamic localization patterns that overlap with the A and C subunits at the bud tip, kinetochore, bud neck, and nucleus. Using strains null for single subunit genes, we confirmed the hypothesis that regulatory subunits determine sites of PP2A accumulation. Although Rts1p and Tpd3p required heterotrimer formation to achieve normal localization, Cdc55p achieved its normal localization in the absence of either an A or C subunit.
Links	PubMed PMC129960 Online version:10.1091/mbc.02-05-0065
Keywords	Cell Cycle/physiology; Cell Cycle Proteins/genetics; Cell Cycle Proteins/metabolism; Cell Nucleus/metabolism; Genotype; Green Fluorescent Proteins; Indicators and Reagents/metabolism; Luminescent Proteins/genetics; Luminescent Proteins/metabolism; Microscopy, Fluorescence; Phosphoprotein Phosphatases/genetics; Phosphoprotein Phosphatases/metabolism; Protein Phosphatase 2; Protein Subunits/genetics; Protein Subunits/metabolism; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Saccharomyces cerevisiae/cytology; Saccharomyces cerevisiae/physiology; Saccharomyces cerevisiae Proteins/genetics; Saccharomyces cerevisiae Proteins/metabolism; Time Factors
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