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CDC25B phosphorylation by Aurora-A occurs at the G2/M transition and is inhibited by DNA damage

Martine Cazales1, Estelle Schmitt, Emilie Montembault

  • 1LBCMCP-CNRS UMR5088-IFR109, Institut d'Exploration Fonctionnelle des Génomes, Université Paul Sabatier, Toulouse, France.

Cell Cycle (Georgetown, Tex.)
|August 6, 2005
PubMed

Insights

Aurora-A kinase phosphorylates CDC25B at the centrosome, promoting mitosis entry. This phosphorylation is blocked by DNA damage checkpoints but can bypass them when Aurora-A is activated.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • CDC25B is a human dual-specificity phosphatase crucial for cell division cycle progression.
  • It activates cyclin-dependent kinases (CDKs), specifically CDK1-cyclin B1, essential for mitosis.
  • CDC25B activity is regulated by phosphorylation, particularly at serine 353 by STK15/Aurora-A kinase at the centrosome.

Purpose of the Study:

  • To investigate the cell cycle regulation of CDC25B phosphorylation at serine 353 by Aurora-A.
  • To determine the role of this phosphorylation in response to G2 DNA damage checkpoint activation.
  • To elucidate the upstream events linking Aurora-A activity, CDC25B phosphorylation, and mitosis induction.

Main Methods:

  • Cell cycle analysis of CDC25B phosphorylation at serine 353.
  • Investigating the impact of DNA damage on Aurora-A and CDC25B.
  • Assessing checkpoint bypass using ectopic Aurora-A expression and CDC25B mutants.
  • Utilizing the CHK1 kinase inhibitor UCN-01 to study G2/M checkpoint override.

Main Results:

  • Serine 353 phosphorylation of CDC25B at the centrosome correlates with cyclin B1 nuclear relocalization and CDK1 activation at mitosis entry.
  • DNA damage activates the G2/M checkpoint, inhibiting Aurora-A activation and subsequent CDC25B phosphorylation.
  • Ectopic Aurora-A expression partially bypasses the checkpoint, an effect enhanced by a CDC25B S353A mutant.
  • Inhibition of CHK1 with UCN-01 activates Aurora-A and phosphorylates CDC25B at serine 353, bypassing the G2/M checkpoint.

Conclusions:

  • Aurora-A-mediated phosphorylation of CDC25B at the centrosome is a key event initiating mitosis.
  • This phosphorylation occurs upstream of CDK1-cyclin B1 activation.
  • The G2 DNA damage checkpoint prevents Aurora-A activation, thereby inhibiting CDC25B phosphorylation and delaying mitosis.

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