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 minibelix 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.
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.
Journal of Biological Chemistry
2003-02-21 / vol 278 / pages 5505-5508