Involvement of CRM1, a nuclear export receptor, in mRNA export in mammalian cells and fission yeast.
BACKGROUND
CRM1, an evolutionarily conserved protein, was shown to be a receptor for leucine-rich nuclear export signal (NES)-dependent protein transport. In lower eukaryotes CRM1 is reported to be required for the export of mRNA, however, involvement of the NES-dependent transport pathway in mRNA export in higher eukaryotes has not been established.


RESULTS
We have found that treatment of mammalian cells with leptomycin B (LMB), a specific inhibitor of CRM1, induces the nuclear accumulation of endogenous mRNA, probably due to the inhibition of its export. In fission yeasts, the nuclear accumulation of mRNA also occurred in cells treated with LMB or in a temperature-sensitive crm1 mutant at a restrictive temperature. A synthetic mRNA that was injected into the nucleus of mammalian cultured cells was exported from the nucleus within 5 h. This export was inhibited by both wheat germ agglutinin and a temperature of 4 degrees C. Importantly, this mRNA export was inhibited by LMB or by an excess amount of the NES peptide-conjugates. LMB treatment, on the other hand, rapidly induced the nuclear entry of RanBP1, a factor involved in the active nucleocytoplasmic transport, although the treatment did not interfere with a nuclear localization signal-dependent transport system within 7 h.


CONCLUSIONS
These results suggest that CRM1 is involved in mRNA export in eukaryotic cells.
Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
M
M
Watanabe
M
M
Fukuda
M
M
Yoshida
M
M
Yanagida
E
E
Nishida
D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005456:Fluorescent Dyes; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D028884:Karyopherins; D008845:Microinjections; D009154:Mutation; D019913:Nuclear Localization Signals / Q000187:drug effects; D009687:Nuclear Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010047:Ovalbumin / Q000378:metabolism; D012333:RNA, Messenger / Q000008:administration & dosage / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear; D012261:Ribonucleoproteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013696:Temperature; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein
D000935:Antifungal Agents; D002352:Carrier Proteins; D005231:Fatty Acids, Unsaturated; D005456:Fluorescent Dyes; D019204:GTP-Binding Proteins; D028884:Karyopherins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010047:Ovalbumin; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D012261:Ribonucleoproteins; D012710:Serum Albumin, Bovine; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C091775:ran-binding protein 1; C038753:leptomycin B