[Source: Journal of Virology, full page: (LINK). Abstract, edited.]
NS5 from Dengue virus serotype 2 can adopt a conformation analogous to its ZIKV and JEV homologues.
Abbas El Sahili, Tingjin Sherryl Soh, Jonas Schiltz, Aïcha Gharbi-Ayachi, Cheah Chen Seh, Pei-Yong Shi, Siew Pheng Lim, Julien Lescar
Flavivirus non-structural protein 5 (NS5) contains a N-terminal methyltransferase domain (MTase) and a C-terminal polymerase domain (RdRp) fused through a nine-amino acid linker. While the individual NS5 domains are structurally conserved, in the full-length protein, their relative orientations fall into two classes: NS5 from JEV and ZIKV adopt one conformation, while NS5 from DENV3 another. Here, we report a crystallographic structure of NS5 from DENV2 in a conformation similar to the extended one seen in JEV and ZIKV NS5 crystal structures, albeit looser. Substituting DENV2 NS5 linker with DENV1, -3, -4, JEV and ZIKV NS5 linkers had modest or minimal effects on in vitro DENV2 MTase and RdRp activities. Heterotypic DENV NS5 linkers attenuated DENV2 replicon growth in cells, whilst JEV and ZIKV NS5 linkers abolished replication. Thus, JEV and ZIKV linkers likely hindered essential DENV2 NS5 interactions with other viral or host proteins within the virus replicative complex. Overall, this work sheds light on the dynamics of the multifunctional flavivirus NS5 protein and its interdomain linker. Targeting the NS5 linker is a possible strategy for producing attenuated flavivirus strains for vaccine design.
Flaviviruses include important human pathogens such as dengue or Zika virus. NS5 is a non-structural protein essential for flavivirus RNA replication, with dual MTase and RdRp enzyme activity and thus constitutes a major drug target. Insights into NS5 structure, dynamics and evolution should inform the development of antiviral inhibitors and vaccine design. We found that NS5 from DENV2 can adopt a conformation resembling NS5 from JEV and ZIKV. Substitution of DENV2 NS5 linker with JEV and ZIKV NS5 linkers abolished DENV2 replication in cells, without significantly impacting in vitro DENV2 NS5 enzymatic activities. We propose that heterotypic Flavivirus NS5 linkers impeded DENV2 NS5 protein-protein interactions that are essential for virus replication.
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Keywords: Flavivirus; Dengue fever; Zika Virus; Japanese Encephalitis virus.