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Coupling of T161 and T14 phosphorylations protects cyclin B-CDK1 from premature activation

Katia Coulonval1, Hugues Kooken, Pierre P Roger

  • 1Institute of Interdisciplinary Research, Université Libre de Bruxelles, Campus Erasme, B-1070 Brussels, Belgium.

Molecular Biology of the Cell
|September 9, 2011
PubMed

Insights

Mitosis regulation involves cyclin B1-CDK1 phosphorylation. Activating T161 phosphorylation is unexpectedly coupled to inhibitory T14 phosphorylation, preventing premature cell cycle activation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitosis initiation depends on cyclin B1-CDK1 activation.
  • CDK1 phosphorylation at T14, Y15 (inhibitory), and T161 (activating) regulates activity.
  • The precise sequence and interplay of these phosphorylations remain incompletely understood.

Purpose of the Study:

  • To investigate the co-occurrence and interdependence of CDK1 phosphorylation sites (T14, Y15, T161) on cyclin B1-CDK1 complexes.
  • To elucidate the regulatory mechanisms governing the activation of cyclin B1-CDK1 during mitosis.
  • To understand the role of Myt1 and Wee1 in regulating CDK1 phosphorylation and cell cycle progression.

Main Methods:

  • Utilized two-dimensional gel electrophoresis to analyze phosphorylation patterns of cyclin B1-CDK1.
  • Employed Myt1 knockdown and leptomycin B treatment to manipulate CDK1 phosphorylation and complex localization.
  • Examined the physiological occurrence of seven distinct phosphorylation combinations on CDK1.

Main Results:

  • Found that T161 (activating) phosphorylation of cyclin B1-CDK1 never occurred without T14 (inhibitory) phosphorylation.
  • Demonstrated that this T14-T161 coupling is dependent on the cytoplasmic accumulation of cyclin B1-CDK1 complexes.
  • Showed that Myt1 knockdown, under specific conditions, could uncouple T14 and T161 phosphorylation, while Wee1 knockdown led to catastrophic mitoses.

Conclusions:

  • The activating phosphorylation of cyclin B1-CDK1 is tightly coupled to its T14 inhibitory phosphorylation, suggesting a novel regulatory mechanism.
  • This coupling mechanism, dependent on complex traffic, likely prevents premature CDK1 activation by inhibiting kinases.
  • Differential regulation by Myt1 and Wee1 highlights their distinct roles in controlling mitotic entry and progression.

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