Hannemann, Holger, Sung, Po-Yu, Bird, Jim, Lim, Siew Pheng and Davidson, Andrew (2013) Serotype Specific Differences in Dengue Virus Non-Structural Protein 5 Nuclear Localisation. Journal of Biological Chemistry.

Abstract

The four serotypes of dengue virus (DENV-1 to 4) have emerged to cause the most important arthropod-borne viral disease of humans. The DENV non-structural protein 5 (NS5) contains multiple enzymatic activities required for capping and replication of the viral RNA genome and has been shown to be involved in evasion of the host immune response. Previous studies have shown that the DENV-2 NS5 is nuclear localized and binds to an importin-/importin-β heterodimer, suggesting that nuclear import occurs via the classical nuclear import pathway and is common to all DENV serotypes. However in this study we demonstrate that there are serotypic differences in NS5 nuclear localization. Whilst the DENV-2 and -3 proteins are predominantly nuclear localized, DENV-1 and -4 NS5 are predominantly if not exclusively localized to the cytoplasm. These findings were shown both by transient expression of GFP or FLAG tagged NS5 or by examination of NS5 produced during virus infection. More detailed comparative studies on the localization of the DENV-2 and -4 NS5 proteins, revealed that the difference in DENV-4 NS5 nuclear localization was not due to rapid nuclear export but rather was due to the lack of a nuclear localisation sequence (NLS) corresponding to the well characterized DENV-2 NS5 a/bNLS. Accordingly, the DENV-2 NS5 but not -4 NS5 interacted specifically with the human importin- isoform KPNA2 but not other importin- isoforms. Surprisingly, siRNA knockdown of KPNA2 in cells either infected with DENV-2 or expressing NS5 alone did not substantially effect NS5 nuclear localization, whereas siRNA knockdown of importin-β dramatically decreased NS5 nuclear localization. The serotypic differences in NS5 nuclear localization were found not to correlate with differences in IL-8 gene expression. The results suggest that NS5 nuclear localization is not strictly required for virus replication but is more likely to have an auxiliary function in the lifecycle of specific DENV serotypes.

Item Type:	Article
Date Deposited:	13 Oct 2015 13:14
Last Modified:	13 Oct 2015 13:14
URI:	https://oak.novartis.com/id/eprint/8181