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Updated: Apr 17, 2026
Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations
Published on: September 20, 2019
Model scenarios for switch-like mitotic transitions
1OCISB, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Abstract:
To facilitate rapid accumulation of Cdk1-phosphorylated substrate proteins, the Cdk1 counter-acting phosphatase, PP2A-B55 is inhibited during M phase by stoichiometric inhibitors (ENSA and Arpp19). These inhibitors are activated when phosphorylated by Cdk1-activated Greatwall-kinase. Recent experiments show that ENSA is dephosphorylated and inactivated by the PP2A-B55 itself, and acts as an unfair substrate inhibiting PP2A-B55 activity towards other Cdk1 substrates. Mathematical modelling shows that this mutual antagonism between the phosphatase and its inhibitor is insufficient to explain the switch-like characteristics of mitotic entry and exit. We show that the feedback regulation of Greatwall activating kinase and/or inactivating phosphatase can explain the abruptness of these cell cycle transitions.
Insights
Cell cycle transitions are abrupt due to feedback regulation. This involves the Greatwall kinase pathway, counteracting the PP2A-B55 phosphatase and its inhibitors like ENSA, ensuring precise mitotic entry and exit.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mitotic entry and exit require precise regulation of Cdk1-phosphorylated proteins.
- The PP2A-B55 phosphatase is inhibited by ENSA and Arpp19 during M phase.
- These inhibitors are activated by the Greatwall kinase.
Purpose of the Study:
- To investigate the regulatory mechanisms governing the abruptness of cell cycle transitions.
- To understand the role of feedback regulation in mitotic entry and exit.
- To explain the switch-like characteristics of cell cycle progression.
Main Methods:
- Mathematical modeling of biochemical pathways.
- Analysis of feedback regulation in the Cdk1-PP2A-B55-ENSA axis.
- Investigating the role of Greatwall kinase and its regulatory partners.
Main Results:
- Mutual antagonism between PP2A-B55 and its inhibitor ENSA is insufficient to explain switch-like cell cycle transitions.
- Feedback regulation of the Greatwall activating kinase and/or inactivating phosphatase explains the abruptness of mitotic entry and exit.
- ENSA acts as an unfair substrate, inhibiting PP2A-B55 activity.
Conclusions:
- Feedback mechanisms involving the Greatwall kinase pathway are crucial for the switch-like nature of cell cycle transitions.
- This regulation ensures precise control over mitotic entry and exit.
- The study provides a model for understanding rapid cell cycle progression.
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