Mutation of the C-terminal leucine residue of PP2Ac inhibits PR55/B subunit binding and confers supersensitivity to microtubule destabilization in Saccharomyces cerevisiae.
Protein phosphatase 2A is ubiquitous among eukaryotes and exists as a family of holoenzymes in which the catalytic subunit. PP2Ac, binds a variety of regulatory subunits. Using the yeast Saccharomyces cerevisia, we have investigated the role of the phylogenetically invariant C-terminal leucine residue of PP2Ac, which, in mammalian cells, undergoes reversible methylation and modulates binding of the PR55/B subunit. In S. cerevisiae, the C-terminal Leu-377 residue of Pph22p (equivalent to human PP2Ac Leu-309) was dispensable for cell growth under optimum conditions and its removal, or substitution by alanine, did not inhibit PP2A activity in vitro. However, Leu-377 is required for binding of the yeast PR55/B subunit, Cdc55p, by Pph22p, though apparently not for the binding of Rts1p, the yeast PR61/B' subunit. Furthermore, mutation of this leucine enhanced the sensitivity of cells to microtubule destabilization, a defect characteristic of cdc55delta mutant cells, which are impaired for spindle checkpoint function. These results demonstrate that the regulation of PP2A, mediated by PR55/B binding to the highly conserved PP2Ac C-terminus, is critical for cell viability under conditions of microtubule damage and support a role for PP2A in exit from mitosis.
Evans
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DR
Program in Molecular Pharmacology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. drhevans@fhcrc.org
Hemmings
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BA
D001542:Benomyl / Q000633:toxicity; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D006801:Humans; D066298:In Vitro Techniques; D007930:Leucine / Q000737:chemistry; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D015739:Nocodazole / Q000633:toxicity; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D054648:Protein Phosphatase 2; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins
C071246:CDC55 protein, S cerevisiae; D018797:Cell Cycle Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D007930:Leucine; D015739:Nocodazole; D001542:Benomyl