Exportin-5 mediates nuclear export of minihelix-containing RNAs.
The adenovirus VA1 RNA (VA1), a 160-nucleotide (nt)-long RNA transcribed by RNA polymerase III, is efficiently exported from the nucleus to the cytoplasm of infected cells, where it antagonizes the interferon-induced antiviral defense system. We recently reported that nuclear export of VA1 is mediated by a cis-acting RNA export motif, called minihelix, that comprises a double-stranded stem (>14 nt) with a base-paired 5' end and a 3-8-nt protruding 3' end. RNA export mediated by the minihelix motif is Ran-dependent, which indicates the involvement of a karyopherin-related factor (exportin) that remained to be determined. Here we show using microinjection in Xenopus laevis oocytes that VA1 is transported to the cytoplasm by exportin-5, a nuclear transport factor for double-stranded RNA binding proteins. Gel retardation assays revealed that exportin-5 directly interacts with VA1 RNA in a RanGTP-dependent manner. More generally, in vivo and in vitro competition experiments using various VA1-derived, but also artificial and cellular, RNAs lead to the conclusion that exportin-5 preferentially recognizes and transports minihelix motif-containing RNAs.[1]References
- Exportin-5 mediates nuclear export of minihelix-containing RNAs. Gwizdek, C., Ossareh-Nazari, B., Brownawell, A.M., Doglio, A., Bertrand, E., Macara, I.G., Dargemont, C. J. Biol. Chem. (2003) [Pubmed]
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