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The mitotic cell cycle can be described as an alternation between two states. During mitosis, MPF (mitosis promoting factor) is high and keeps inactive its numerous molecular antagonists. In interphase, MPF is inactivated, and the antagonists prevail. The transition between the two states is ensured by 'helper' molecules that favor one state over the other. It has long been assumed that active MPF (a dimer of cyclin B and cyclin-dependent kinase 1) induces exit from mitosis by activating APC:Cdc20, a ubiquitin ligase responsible for cyclin B degradation. The molecular details have not been fully worked out yet, but recent results show that MPF and the ubiquitin ligase are not involved in a simple negative feedback loop. While it is proven that MPF activates APC, new data suggest that MPF inhibits Cdc20, i.e., that MPF and Cdc20 are antagonists. We introduce this new idea into a published model for cell cycle regulation in Xenopus laevis, and study its dynamical behavior. We show that the new wiring permits oscillations with a simpler and smaller network than previously envisaged and that the antagonism between MPF and Cdc20 suggests a new interpretation of the spindle checkpoint.

Type

Journal article

Journal

Cell Cycle

Publication Date

2005

Volume

4

Pages

1107 - 1112

Keywords

Animals Cell Cycle Cell Cycle Proteins/metabolism/physiology Cell Nucleus/metabolism Cyclin B/metabolism Dimerization Kinetics Maturation-Promoting Factor/*metabolism *Mitosis Mitotic Spindle Apparatus Models, Biological Models, Chemical Models, Theoretical Oscillometry Phosphates/chemistry Phosphorylation Protein Binding Time Factors Ubiquitin-Protein Ligase Complexes/metabolism Ubiquitin-Protein Ligases/chemistry Xenopus Xenopus Proteins/physiology Xenopus laevis/metabolism