RT Journal Article SR Electronic(1) A1 Han, Kang Rok A1 Lee, Ji-Hye A1 Kotiguda, Giri Gowda A1 Jung, Kyoung Ho A1 Chung, Mi Sook A1 Kang, Soowon A1 Hwang, Seungmin A1 Kim, Kyung HyunYR 2018 T1 Nucleotide triphosphatase and RNA chaperone activities of murine norovirus NS3 JF Journal of General Virology, VO 99 IS 11 SP 1482 OP 1493 DO https://doi.org/10.1099/jgv.0.001151 PB Microbiology Society, SN 1465-2099, AB Modulation of RNA structure is essential in the life cycle of RNA viruses. Immediate replication upon infection requires RNA unwinding to ensure that RNA templates are not in intra- or intermolecular duplex forms. The calicivirus NS3, one of the highly conserved nonstructural (NS) proteins, has conserved motifs common to helicase superfamily 3 among six genogroups. However, its biological functions are not fully understood. In this study we report the oligomeric state and the nucleotide triphosphatase (NTPase) and RNA chaperone activities of the recombinant full-length NS3 derived from murine norovirus (MNV). The MNV NS3 has an Mg2+-dependent NTPase activity, and site-directed mutagenesis of the conserved NTPase motifs blocked enzyme activity and viral replication in cells. Further, the NS3 was found via fluorescence resonance energy transfer (FRET)-based assays to destabilize double-stranded RNA in the presence of Mg2+ or Mn2+ in an NTP-independent manner. However, the RNA destabilization activity was not affected by mutagenesis of the conserved motifs of NTPase. These results reveal that the MNV NS3 has an NTPase-independent RNA chaperone-like activity, and that a FRET-based RNA destabilization assay has the potential to identify new antiviral drugs targeting NS3., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.001151