A small region of the dengue virus-encoded RNA-dependent RNA polymerase, NS5, confers interaction with both the nuclear transport receptor importin-ss and the viral helicase, NS3

The dengue virus RNA-dependent RNA polymerase, NS5, and the protease/helica se, NS3, are multidomain proteins that have been shown to interact both in vivo and in vitro, A hyperphosphorylated form of NS5 that does not interact with NS3 has been detected in the nuclei of virus-infected cells, presumab ly as the result of the action of a functional nuclear localization sequenc e within the interdomain region of NS5 (residues 369-405), In this study, i t is shown by using the yeast two-hybrid system that the C-terminal region of NS3 (residues 303-618) interacts with the N-terminal region of NS5 (resi dues 320-368), Further, it is shown that this same region of NS5 is also re cognized by the cellular nuclear import receptor importin-beta, The interac tion between NS5 and importin-beta and competition by NS3 with the latter f or the same binding site on NS5 were confirmed by pull-down assays, The dir ect interaction of importin-beta with NS5 has implications for the mechanis m by which this normally cytoplasmic protein may be targetted to the nucleu s.