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A conserved cyclin-binding domain determines functional interplay between anaphase-promoting complex-Cdh1 and cyclin
C S Sørensen1, C Lukas, E R Kramer
1Institute of Cancer Biology, Danish Cancer Society, DK-2100 Copenhagen Ø, Denmark.
Molecular and Cellular Biology
|May 8, 2001
Summary
The anaphase-promoting complex (APC) controls cell cycle progression. This study shows cyclin A-Cdk2 binds Cdh1, preventing premature APC reactivation during S phase and ensuring proper cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The anaphase-promoting complex (APC) ubiquitin ligase regulates cell cycle transitions by degrading key proteins.
- APC inhibition at the G1/S transition, mediated by Cdh1 subunit phosphorylation, is crucial for cell cycle progression.
- The specific cyclin-dependent kinase (CDK) complexes responsible for Cdh1 phosphorylation and their interaction mechanisms with APC subunits have been debated.
Purpose of the Study:
- To elucidate the role of mammalian cyclin A-Cdk2 in regulating APC activity during S phase.
- To identify the mechanism by which cyclin-CDKs interact with the APC Cdh1 subunit.
- To investigate the functional consequences of disrupting the Cdh1-cyclin A-Cdk2 interaction.
Main Methods:
- Demonstration of periodic interaction between endogenous cyclin A-Cdk2 and Cdh1.
- Identification and disruption of a conserved cyclin-binding motif in the Cdh1 WD-40 domain.
- In vitro and in vivo assays to assess Cdh1 phosphorylation and APC-Cdh1 complex stability.
- Analysis of APC-dependent proteolysis of various substrates upon expression of cyclin-binding deficient Cdh1.
Main Results:
- Cyclin A-Cdk2 periodically interacts with Cdh1, preventing premature APC reactivation during S phase.
- Disruption of the Cdh1 cyclin-binding motif abolished cyclin A-Cdk2 interaction, Cdh1 kinase activity, and Cdh1 phosphorylation.
- Overexpression of cyclin-binding deficient Cdh1 led to prolonged G1/S arrest and impaired proteolysis of cyclin A, but not cyclin B or securin.
- Evidence suggests Cdh1 may activate the APC through substrate binding.
Conclusions:
- Cyclin A-Cdk2 and APC-Cdh1 exhibit a mutual functional interplay crucial for cell cycle regulation.
- A conserved motif in Cdh1 mediates interaction with cyclin A-Cdk2, impacting APC activity.
- This study provides mechanistic insights into APC-Cdh1 regulation and suggests a novel role for Cdh1 in APC activation.