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How tyrosine 15 phosphorylation inhibits the activity of cyclin-dependent kinase 2-cyclin A

Julie P I Welburn1, Julie A Tucker, Tim Johnson

  • 1AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, Cheshire SK10 4TF, United Kingdom.

The Journal of Biological Chemistry
|November 11, 2006
PubMed

Insights

Inhibiting cyclin-dependent kinase 1 (CDK1) via Tyr-15 phosphorylation controls cell cycle entry into mitosis. Unlike CDK1, Tyr-15 phosphorylated CDK2 retains kinase activity, impacting cell cycle models.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinases (CDKs) are crucial regulators of the eukaryotic cell cycle.
  • Inhibitory phosphorylation, particularly at Tyr-15, is a key mechanism for controlling CDK activity and cell cycle progression.
  • Understanding these regulatory mechanisms is fundamental for comprehending cell cycle control and potential disruptions.

Purpose of the Study:

  • To investigate the mechanistic basis of inhibitory Tyr-15 phosphorylation in cyclin-dependent kinases.
  • To compare the effects of Tyr-15 phosphorylation on CDK1 and CDK2 activity.
  • To assess the implications of these findings for cell cycle regulation models.

Main Methods:

  • Kinetic analyses of CDK2-cyclin A complexes.
  • Crystallographic studies of CDK2-cyclin A complexes.
  • Biochemical assays to measure kinase and ATPase activity.

Main Results:

  • Tyr-15 phosphorylation of CDK1 inhibits its activity, regulating entry into mitosis and cell cycle progression.
  • Inhibition by Tyr-15 phosphorylation in CDK1 functions via steric hindrance of substrate binding and unfavorable ATP conformation.
  • Unlike CDK1, Tyr-15 phosphorylation of CDK2 does not significantly alter its ATP binding kinetics (Km) or intrinsic ATPase activity.
  • Tyr-15 phosphorylated CDK2 retains residual protein phosphorylation activity.

Conclusions:

  • The mechanism of cell cycle regulation by inhibitory Tyr-15 phosphorylation differs between CDK1 and CDK2.
  • Residual activity of Tyr-15 phosphorylated CDK2 necessitates its consideration in quantitative and qualitative cell cycle models.
  • These findings refine our understanding of CDK regulation and its role in cell cycle control.

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