Cdc25M2 activation of cyclin-dependent kinases by dephosphorylation of threonine-14 and tyrosine-15

Proc Natl Acad Sci U S A. 1993 Apr 15;90(8):3521-4. doi: 10.1073/pnas.90.8.3521.


Recent evidence has suggested that human cyclin-dependent kinase 2 (CDK2) is an essential regulator of cell cycle progression through S phase. CDK2 is known to complex with at least two distinct human cyclins, E and A. The kinase activity of these complexes peaks in G1 and S phase, respectively. The vertebrate CDC2/cyclin B1 complex is an essential regulator of the onset of mitosis and is inhibited by phosphorylation of CDC2 on Thr-14 and Tyr-15. In vitro, CDC2/cyclin B1 is activated by treatment with the members of the Cdc25 family of phosphatases. We found that, like CDC2, CDK2 is also phosphorylated on Thr-14 and Tyr-15 and that treatment of cyclin A or cyclin E immunoprecipitates with bacterially expressed Cdc25M2 (the mouse homolog of human CDC25B) increased the histone H1 kinase activity of these immune complexes 5- to 10-fold. Tryptic peptide mapping demonstrated that Cdc25M2 treatment of cyclin A or cyclin B1 immune complexes resulted in the specific dephosphorylation of Thr-14 and Tyr-15 on CDK2 or CDC2, respectively. Thus, we have confirmed that Cdc25 family members comprise a class of dual-specificity phosphatases. Furthermore, our data suggest that the phosphorylation and dephosphorylation of CDKs on Thr-14 and Tyr-15 may regulate not only the G2/M transition but also other transitions in the cell cycle and that individual cdc25 family members may regulate distinct cell cycle checkpoints.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • CDC2-CDC28 Kinases*
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases*
  • Enzyme Activation
  • Glutathione Transferase / metabolism
  • HeLa Cells
  • Humans
  • Mice
  • Peptide Mapping
  • Phosphates / metabolism
  • Phosphopeptides / isolation & purification
  • Phosphorylation
  • Protein Kinases / isolation & purification
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases*
  • Proteins / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Threonine*
  • Trypsin
  • Tyrosine*
  • cdc25 Phosphatases


  • Phosphates
  • Phosphopeptides
  • Proteins
  • Recombinant Fusion Proteins
  • Threonine
  • Tyrosine
  • Glutathione Transferase
  • Protein Kinases
  • Protein-Serine-Threonine Kinases
  • CDC2-CDC28 Kinases
  • CDK2 protein, human
  • Cdk2 protein, mouse
  • Cyclin-Dependent Kinase 2
  • Cyclin-Dependent Kinases
  • cdc25 Phosphatases
  • Trypsin