Abstract
Cyclins A and E and their partner cyclin-dependent kinases (Cdks) are key regulators of DNA synthesis and of mitosis. Immunofluorescence studies have shown that both cyclins are nuclear and that a proportion of cyclin A is localized to sites of DNA replication. However, recently, both cyclin A and cyclin E have been implicated as regulators of centrosome replication, and it is unclear when and where these cyclin-Cdks can interact with cytoplasmic substrates. We have used live cell imaging to study the behavior of cyclin/Cdk complexes. We found that cyclin A and cyclin E are able to regulate both nuclear and cytoplasmic events because they both shuttle between the nucleus and the cytoplasm. However, we found that there are marked differences in their shuttling behavior, which raises the possibility that cyclin/Cdk function could be regulated at the level of nuclear import and export. In the course of these experiments, we have also found that, contrary to published results, mutations in the hydrophobic patch of cyclin A do affect Cdk binding and nuclear import. This has implications for the role of the hydrophobic patch as a substrate selection motif.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Active Transport, Cell Nucleus / physiology*
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Antifungal Agents / pharmacology
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CDC2-CDC28 Kinases*
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Cell Nucleus / metabolism*
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Cyclin A / genetics
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Cyclin A / metabolism*
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Cyclin B / metabolism
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Cyclin B1
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Cyclin E / genetics
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Cyclin E / metabolism*
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases / genetics
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Cyclin-Dependent Kinases / metabolism*
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Cytoplasm / metabolism*
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Exportin 1 Protein
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Fatty Acids, Unsaturated / pharmacology
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Green Fluorescent Proteins
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HeLa Cells / cytology
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HeLa Cells / drug effects
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HeLa Cells / metabolism
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Humans
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Indicators and Reagents / metabolism
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Karyopherins / metabolism
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Macromolecular Substances
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Nuclear Proteins / metabolism
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Nucleoplasmins
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Phosphoproteins / metabolism
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Protein Binding
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Receptors, Cytoplasmic and Nuclear*
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
Substances
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Antifungal Agents
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CCNB1 protein, human
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Cyclin A
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Cyclin B
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Cyclin B1
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Cyclin E
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Fatty Acids, Unsaturated
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Indicators and Reagents
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Karyopherins
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Luminescent Proteins
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Macromolecular Substances
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Nuclear Proteins
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Nucleoplasmins
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Phosphoproteins
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Receptors, Cytoplasmic and Nuclear
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Recombinant Fusion Proteins
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Green Fluorescent Proteins
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Protein Serine-Threonine Kinases
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CDC2-CDC28 Kinases
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CDK2 protein, human
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases
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leptomycin B