Abstract
The cyclin-dependent kinase (Cdk) enzymes, when associated with the G1 cyclins D and E, are rate-limiting for entry into the S phase of the cell cycle. During T-cell mitogenesis, antigen-receptor signalling promotes synthesis of cyclin E and its catalytic partner, Cdk2, and interleukin-2 (IL-2) signalling activates cyclin E/Cdk2 complexes. Rapamycin is a potent immunosuppressant which specifically inhibits G1-to-S-phase progression, leading to cell-cycle arrest in yeast and mammals. Here we report that IL-2 allows Cdk activation by causing the elimination of the Cdk inhibitor protein p27Kip1, and that this is prevented by rapamycin. By contrast, the Cdk inhibitor p21 is induced by IL-2 and this induction is blocked by rapamycin. Our results show that p27Kip1 governs Cdk activity during the transition from quiescence to S phase in T lymphocytes and that p21 function may be restricted to cycling cells.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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CDC2-CDC28 Kinases*
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Cell Cycle / physiology
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Cell Cycle Proteins*
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Cell Line
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclin-Dependent Kinase Inhibitor p27
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Cyclin-Dependent Kinases / antagonists & inhibitors
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Cyclin-Dependent Kinases / metabolism*
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Cyclins / metabolism
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Enzyme Activation
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Fungal Proteins / metabolism*
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Immunosuppressive Agents / pharmacology*
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Interleukin-2 / antagonists & inhibitors
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Interleukin-2 / physiology*
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Mice
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Microtubule-Associated Proteins / metabolism*
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Polyenes / pharmacology*
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / metabolism*
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Sirolimus
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T-Lymphocytes / cytology
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T-Lymphocytes / drug effects
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T-Lymphocytes / enzymology
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Tumor Suppressor Proteins*
Substances
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Cdkn1a protein, mouse
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Cdkn1b protein, mouse
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Cell Cycle Proteins
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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Fungal Proteins
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Immunosuppressive Agents
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Interleukin-2
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Microtubule-Associated Proteins
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Polyenes
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Tumor Suppressor Proteins
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Cyclin-Dependent Kinase Inhibitor p27
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Protein Serine-Threonine Kinases
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CDC2-CDC28 Kinases
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Cdk2 protein, mouse
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases
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Sirolimus