Brooks, Andrew J., Johansson, Magnus, Johns, Anna V., Xu, Yibin, Jans, David A., and Vasudevan, Subhash G. (2002) The interdomain region of dengue NS5 protein that binds to the viral helicase NS3 contains independently functional importin β1 and importin α/β-recognized nuclear localization signals. Journal of Biological Chemistry, 277 (39). pp. 36399-36407.

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Abstract

Dengue virus NS5 protein is a multifunctional RNA-dependent RNA polymerase that is essential for virus replication. We have shown previously that the 37- amino acid interdomain spacer sequence (residues369 X 2KKX 14KKKX 11RKX 3 405) of Dengue2 NS5 contains a functional nuclear localization signal (NLS). In this study, β-galactosidase fusion proteins carrying point mutations of the positively charged residues or truncations of the interdomain linker region (residues 369–389 or residues 386–405) were analyzed for nuclear import and importin binding activities to show that the N-terminal part of the linker region (residues 369–389, a/bNLS) is critical for nuclear localization and is recognized with high affinity by the conventional NLS-binding importin α/β heterodimeric nuclear import receptor. We also show that the importin β-binding site (residues 320–368, bNLS) adjacent to the a/bNLS, previously identified by yeast two-hybrid analysis, is functional as an NLS, recognized with high affinity by importin β, and able to target β-galactosidase to the nucleus. Intriguingly, the bNLS is highly conserved among Dengue and related flaviviruses, implying a general role for the region and importin β in the infectious cycle.

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