Dephosphorylation of Human Cyclin-dependent Kinases by Protein Phosphatase Type 2Cα and β2 Isoforms*

By A. Cheng, Philipp Kaldis, M. Solomon. Journal of Biological Chemistry, 2000

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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 PP2Cβ2, a novel PP2Cβ isoform, and to PP2Cα. PP2Cα and PP2Cβ2 co-purified with Mg2+-dependent Cdk2/Cdk6 phosphatase activity in DEAE-Sepharose, Superdex-200, and Mono Q chromatographies. Moreover, purified recombinant PP2Cα and PP2Cβ2 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 PP2Cα and PP2Cβ2 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.

Subfields: Cell Biology, Molecular Biology, Oncology

View Paper: https://www.semanticscholar.org/paper/1cab4bc59641e66fa9a821124451d16aecdd3ef7