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Title
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A novel ubiquitin-like modification modulates the partitioning of the Ran-GTPase-activating protein RanGAP1 between the cytosol and the nuclear pore complex.
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Authors
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M.J.Matunis,
E.Coutavas,
G.Blobel.
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Ref.
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J Cell Biol, 1996,
135,
1457-1470.
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PubMed id
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Abstract
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Ran is a nuclear Ras-like GTPase that is required for the bidirectional
transport of proteins and ribnucleoproteins across the nuclear pore complex
(NPC). A key regulator of the Ran GTP/GDP cycle is the 70-kD
Ran-GTPase-activating protein RanGAP1. Here, we report the identification and
localization of a novel form of RanGAP1. Using peptide sequence analysis and
specific mAbs, RanGAP1 was found to be modified by conjugation to a
ubiquitin-like protein. Immunoblot analysis and immunolocalization by light and
EM demonstrated that the 70-kD unmodified from of RanGAP1 is exclusively
cytoplasmic, whereas the 90-kD modified form of RanGAP1 is associated with the
cytoplasmic fibers of the NPC. The modified form of RanGAP1 also appeared to
associated with the mitotic spindle apparatus during mitosis. These findings
have specific implications for Ran function and broad implications for protein
regulation by ubiquitin-like modifications. Moreover, the variety and function
of ubiquitin-like protein modifications in the cell may be more diverse than
previously realized.
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