Abstract
The guanosine triphosphatase Ran stimulates assembly of microtubule asters and spindles in mitotic Xenopus egg extracts. A carboxyl-terminal region of the nuclear-mitotic apparatus protein (NuMA), a nuclear protein required for organizing mitotic spindle poles, mimics Ran's ability to induce asters. This NuMA fragment also specifically interacted with the nuclear transport factor, importin-beta. We show that importin-beta is an inhibitor of microtubule aster assembly in Xenopus egg extracts and that Ran regulates the interaction between importin-beta and NuMA. Importin-beta therefore links NuMA to regulation by Ran. This suggests that similar mechanisms regulate nuclear import during interphase and spindle assembly during mitosis.
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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Cell Extracts
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Cell Nucleus / metabolism
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Guanosine Triphosphate / metabolism
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Interphase
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Karyopherins
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Microtubules / drug effects
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Microtubules / metabolism*
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Mitosis
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Models, Biological
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Nuclear Proteins / metabolism*
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Nuclear Proteins / pharmacology
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Ovum
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Paclitaxel / pharmacology
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Recombinant Fusion Proteins / metabolism
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Spindle Apparatus / drug effects
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Spindle Apparatus / metabolism*
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Xenopus
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Xenopus Proteins*
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ran GTP-Binding Protein / metabolism*
Substances
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Cell Extracts
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Karyopherins
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NUMA1 protein, Xenopus
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Nuclear Proteins
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Recombinant Fusion Proteins
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Xenopus Proteins
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Guanosine Triphosphate
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ran GTP-Binding Protein
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Paclitaxel