| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1998: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
CRM1, an evolutionarily conserved protein, is shown to be a receptor for leucine-rich nuclear export signal (NES)-dependent protein transport, but its role in mRNA export has not been established in higher eukaryotes. We have found that treatment of mammalian cells with leptomycin B (LMB), a specific inhibitor of CRM1, induces nuclear accumulation of endogenous mRNA probably due to the inhibition of its export. In fission yeast, 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 wheat germ agglutinin or at 40C. Importantly, this mRNA export was inhibited by LMB or by an excess amount of the NES peptideconjugates. These results suggest that CRM1 is involved in mRNA export in eukaryotic cells.
We previously demonstrated that MAPKK(MAPK kinase),a direct activator for MAPK, as an NES and acts as a cytoplasmic anchor of MAPK. In this project, we revealed the regulatory mechanisms of the dissociation and/or the association of the MAPKK/MAPK complex. Tyrosine(Tyr190 in Xenopus MAPK)phosphorylation of MAPK by MAPKK is necessary and sufficient for the dissociation of the complex.
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