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Oncogenic Ras suppresses Cdk1 in a complex manner during the incubation of activated Xenopus egg extracts

Tun-Lan Huang1, Jerry P Pian, Bin-Tao Pan

  • 1Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA.

Archives of Biochemistry and Biophysics
|February 5, 2013
PubMed

Insights

Oncogenic Ras suppresses Cdk1 activation by maintaining inhibitory phosphorylation and causing continuous cyclin B2 accumulation in Xenopus egg extracts, revealing a complex regulatory mechanism.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinase 1 (Cdk1) activation drives M-phase entry in the cell cycle.
  • Cdk1 activation depends on cyclin B synthesis, binding, and removal of inhibitory Tyr15 phosphorylation.
  • Oncogenic Ras is known to suppress Cdk1 activation, but the mechanism remains unclear.

Purpose of the Study:

  • To elucidate the mechanism by which oncogenic Ras suppresses Cdk1 activation.
  • To investigate the effects of oncogenic Ras on cyclin B2 levels and Tyr15-Cdk1 phosphorylation.

Main Methods:

  • Utilized Xenopus egg extracts for cell-free experiments.
  • Employed histone H1 kinase assays to measure Cdk1 activity.
  • Performed Western blot analysis to quantify cyclin B2 and phosphorylated Tyr15-Cdk1 levels.

Main Results:

  • Oncogenic Ras induces persistent inhibitory phosphorylation of Tyr15-Cdk1.
  • Oncogenic Ras leads to continuous accumulation of cyclin B2, unlike the transient accumulation in controls.
  • Cyclin B2 stabilization, mediated by the Raf-Mek-Erk-p90(rsk) pathway, underlies its continuous accumulation.

Conclusions:

  • Oncogenic Ras suppresses Cdk1 through a dual mechanism: persistent inhibitory phosphorylation and continuous cyclin B2 accumulation.
  • The Raf-Mek-Erk-p90(rsk) pathway is crucial for oncogenic Ras-induced cyclin B2 stabilization.
  • This study reveals a complex interplay between oncogenic signaling and cell cycle regulation.

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