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Cyclin/Cdk complexes: their involvement in cell cycle progression and mitotic division
1Plant Cell Biology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia.
Protoplasma
|December 6, 2001
Summary
Cyclin-dependent kinases (CDKs) regulate DNA replication and mitosis. Cyclins bind CDKs, directing them to substrates, with their changing levels controlling cell cycle progression and substrate specificity, including in plants.
Area of Science:
- Cell Biology
- Molecular Biology
- Plant Biology
Background:
- Cell cycle progression, including DNA replication and mitosis, relies on cyclin-dependent protein kinase (CDK) activity.
- CDKs are heterodimers of catalytic and cyclin subunits, with cyclin binding determining substrate specificity.
- Cyclin abundance, regulated by transcription and proteolysis, modulates CDK activity and substrate targeting throughout the cell cycle.
Purpose of the Study:
- To assess the mechanisms and biological significance of cyclin protein binding to CDKs.
- To investigate the role of cyclin/CDK complexes in cell cycle regulation across diverse organisms.
- To examine the distribution and function of cyclins and CDKs in plant cell division, specifically in maize root tips.
Main Methods:
- Analysis of substrate specificity in animal CDK enzymes (D-, A-, and B-type cyclins).
- Extensive cyclin gene manipulations in yeasts.
- Microscopic observation of cyclin and CDK distribution in maize root tip cells during mitosis and cytokinesis.
Main Results:
- Cyclin binding extends the range of CDK substrates, influencing cell cycle regulation.
- Overlapping functions of cyclins were identified through gene deletions, suggesting functional redundancy.
- In maize root tips, specific cyclins (CycB1zm;2, CycA1;zm;1) and CDK1 (Cdc2a) localize to key structures like the preprophase band, chromosomes, nuclear envelope, and phragmoplast, correlating with cell cycle events.
- Mitotic cyclins persist after anaphase in plants, a potentially unique phenomenon.
Conclusions:
- Cyclins spatially focus CDK activity, mediating its effects on cellular structures.
- Changing cyclin levels are crucial for cell cycle progression, particularly in initiating DNA replication.
- Plant cells utilize similar mechanisms for cell cycle control involving cyclins and CDKs, with unique aspects in mitotic cyclin behavior and cytokinesis.
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