Zeng, Miao, Chen, Shun, Zhang, Wei, Duan, Yanping, Jiang, Bowen, Pan, Xin, Wang, Mingshu, Jia, Renyong, Zhu, Dekang, Liu, Mafeng, Zhao, Xinxin, Yang, Qiao, Wu, Ying, Zhang, Shaqiu, Huang, Juan, Ou, Xumin, Mao, Sai, Tian, Bin, Gao, Qun, and Cheng, Anchun
• TMUV NS5 contains a suboptimal NLS and does not appreciably accumulate in the nucleus. • Two arginine mutations N390R and Q392R of the NS5 bipartite nuclear localization sequence (α/βNLS) are sufficient to transport NS5 into the nucleus. • Nuclear localization of NS5 strongly reduces virus replication and production in vitro but exhibits no obvious pathogenicity in vivo. • A small subset of NS5 NLSmut showed to interact with NS3 under transfection and infection conditions. • NS5 NLSmut didn't not compromise interferon production mediated by RIG-I detection of the viral RNA polymerase activity. Duck Tembusu virus (TMUV) belongs to the flavivirus genus whose genome replication involved in capping and RNA synthesis dominating by nonstructural protein 5 (NS5). Flaviviral replication has been well documented to occur in the cytoplasm, but the effect of NS5 to gain access to the nucleus remains controversial. Here, TMUV NS5 was observed to localize within the cytoplasm of transfected and infected cells and co-localized with the endoplasmic reticulum. We introduced two arginine mutations into the N390 and Q392 (N390R and Q392R) of the NS5 bipartite nuclear localization sequence (α/βNLS) and designated that mutagenesis as NS5 NLSmut , which has shown the ability to access the nucleus and hence attenuates viral replication and production in vitro. Additionally, there was no significant difference between the recovered wild-type TMUV (rTMUV-WT) and engineered mutant (rTMUV-NS5 NLSmut) on plaque morphology, survival rate of infected duck embryos or virus copies in tissues. Considering that NS5 NLSmut is mainly located in the cytoplasm of rTMUV-NS5 NLSmut infected cells at the early stage of infection. We further confirmed that NS5 NLSmut attenuated its interaction with nonstructural NS2B-NS3 (NS2B3) following transfection and infection. Meanwhile, the rTMUV-NS5 NLSmut tended to stimulate more interferon beta (IFNβ) than rTMUV-WT. However, preliminary study on transient NS5 and NS5 NLSmut detected the same levels of IFNβ mRNA mediated by RIG-I detection of NS5 RNA polymerase activity in cell. In summary, these results provide further insights into the relationship between the viral property and subcellular localization of flavivirus NS5 in terms of the NS5-NS2B3 interaction. [ABSTRACT FROM AUTHOR]