Abstract
In eukaryotes, tRNAs are synthesized in the nucleus and after several maturation steps exported to the cytoplasm. Here, we identify exportin-t as a specific mediator of tRNA export. It is a RanGTP-binding, importin beta-related factor with predominantly nuclear localization. It shuttles rapidly between nucleus and cytoplasm and interacts with nuclear pore complexes. Exportin-t binds tRNA directly and with high affinity. Its cellular concentration in Xenopus oocytes was found to be rate-limiting for export of all tRNAs tested, as judged by microinjection experiments. RanGTP regulates the substrate-exportin-t interaction such that tRNA can be preferentially bound in the nucleus and released in the cytoplasm.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Carrier Proteins / genetics*
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Carrier Proteins / metabolism
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Cell Nucleus / chemistry*
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Cell Nucleus / metabolism*
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Cloning, Molecular
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Cytoplasm / metabolism
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GTP-Binding Proteins / metabolism
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GTPase-Activating Proteins*
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HeLa Cells
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Humans
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Molecular Sequence Data
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Nucleocytoplasmic Transport Proteins*
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Oocytes / physiology
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Protein Binding / physiology
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RNA, Messenger / analysis
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RNA, Transfer / metabolism*
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RNA, Transfer, Amino Acid-Specific / metabolism
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RNA, Transfer, Leu / metabolism
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RNA, Transfer, Ser / metabolism
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Xenopus
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Xenopus Proteins
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beta Karyopherins
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ran GTP-Binding Protein
Substances
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Carrier Proteins
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GTPase-Activating Proteins
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Nuclear Proteins
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Nucleocytoplasmic Transport Proteins
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RANGAP1 protein, human
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RNA, Messenger
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RNA, Transfer, Amino Acid-Specific
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RNA, Transfer, Leu
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RNA, Transfer, Ser
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RanGAP1 protein, Xenopus
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XPOT protein, human
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Xenopus Proteins
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beta Karyopherins
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ran-binding protein 1
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tRNA, selenocysteine-
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RNA, Transfer
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GTP-Binding Proteins
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ran GTP-Binding Protein