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Dephosphorylation of human cyclin-dependent kinases by protein phosphatase type 2C alpha and beta 2 isoforms.

We previously reported that the activating phosphorylation on cyclin-dependent kinases in yeast (Cdc28p) and in humans (Cdk2) is removed by type 2C protein phosphatases. In this study, we characterize this PP2C-like activity in HeLa cell extract and determine that it is due to PP2C beta 2, a novel PP2C beta isoform, and to PP2C alpha. PP2C alpha and PP2C beta 2 co-purified with Mg(2+)-dependent Cdk2/Cdk6 phosphatase activity in DEAE-Sepharose, Superdex-200, and Mono Q chromatographies. Moreover, purified recombinant PP2C alpha and PP2C beta 2 proteins efficiently dephosphorylated monomeric Cdk2/Cdk6 in vitro. The dephosphorylation of Cdk2 and Cdk6 by PP2C isoforms was inhibited by the binding of cyclins. We found that the PP2C-like activity in HeLa cell extract, partially purified HeLa PP2C alpha and PP2C beta 2 isoforms, and the recombinant PP2Cs exhibited a comparable substrate preference for a phosphothreonine containing substrate, consistent with the conservation of threonine residues at the site of activating phosphorylation in CDKs.

Pubmed ID: 10934208


  • Cheng A
  • Kaldis P
  • Solomon MJ


The Journal of biological chemistry

Publication Data

November 3, 2000

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM47830

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Chromatography, Ion Exchange
  • Cyclin-Dependent Kinases
  • Cyclins
  • HeLa Cells
  • Humans
  • Isoenzymes
  • Mice
  • Molecular Sequence Data
  • Phosphoprotein Phosphatases
  • Phosphorylation
  • Protein Phosphatase 2
  • Rats
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Substrate Specificity