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CRM1 is responsible for intracellular transport mediated by the nuclear export signal


The discovery of nuclear export signals (NESs) in a number of proteins revealed the occurrence of signal-dependent transport of proteins from the nucleus to the cytoplasm1,2,3,4,5,6,7,8,9,10,11,12,13,14. Although the consensus motif of the NESs has been shown to be a leucine-rich, short amino-acid sequence2,6,7, its receptor has not been identified. A cytotoxin leptomycin B (LMB) has recently been suggested to inhibit the NES-mediated transport of Rev protein15. Here we show that LMB is a potent and specific inhibitor of the NES-dependent nuclear export of proteins. Moreover, we have found a protein of relative molecular mass 110K (p110) in Xenopus oocyte extracts that binds to the intact NES but not to the mutated, non-functional NES. The binding of p110 to NES is inhibited by LMB. We show that p110 is CRM1, which is an evolutionarily conserved protein16,17,18 originally found as an essential nuclear protein in fission yeast16 and known as a likely target of LMB19. We also show that nuclear export of a fission yeast protein, Dsk1, which has a leucine-rich NES, is disrupted in wild-type yeast treated with LMB or in the crm1 mutant. These results indicate that CRM1 is an essential mediator of the NES-dependent nuclear export of proteins in eukaryotic cells.

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Figure 1: LMB is an inhibitor of the NES-dependent nuclear export of proteins.
Figure 2: The p110 protein binds specifically to NES in an LMB-sensitive manner.
Figure 3: Disruption of cytoplasmic localization and nuclear exclusion of Dsk1 in a fission-yeast crm1 mutant.


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We thank K. Kumada for comments and discussion, and M. Watanabe for preparation of Dsk1-NES-OVA. This work was supported by grants from the Ministry of Education, Science and Culture of Japan (E.N.) and the Japan Science Technology Corporation (M. Yanagida).

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Correspondence to Eisuke Nishida.

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Fukuda, M., Asano, S., Nakamura, T. et al. CRM1 is responsible for intracellular transport mediated by the nuclear export signal. Nature 390, 308–311 (1997).

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