title: Substitution of NS5 N-terminal domain of dengue virus type 2 RNA with type 4 domain caused impaired replication and emergence of adaptive mutants with enhanced fitness.
abstract: Flavivirus NS3 and NS5 are required in viral replication and 5'-capping. NS3 has NS2B-dependent protease, RNA helicase, and 5'-RNA triphosphatase activities. NS5 has 5'-RNA methyltransferase (MT)/guanylyltransferase (GT) activities within the N-terminal 270 amino acids and the RNA-dependent RNA polymerase (POL) activity within amino acids 271-900. A chimeric NS5 containing the D4MT/D4GT and the D2POL domains in the context of wild-type (WT) D2 RNA was constructed. RNAs synthesized in vitro were transfected into baby hamster kidney cells. The viral replication was analyzed by an indirect immunofluorescence assay to monitor NS1 expression and by quantitative real-time PCR. WT D2 RNA-transfected cells were NS1- positive by day 5, whereas the chimeric RNA-transfected cells became NS1-positive ∼30 days post-transfection in three independent experiments. Sequence analysis covering the entire genome revealed the appearance of a single K74I mutation within the D4MT domain ∼16 days post-transfection in two experiments. In the third, D290N mutation in the conserved NS3 Walker B motif appeared ≥16 days post-transfection. A time course study of serial passages revealed that the 30-day supernatant had gradually evolved to gain replication fitness. Trans-complementation by co-expression of WT D2 NS5 accelerated viral replication of chimeric RNA without changing the K74I mutation. However, the MT and POL activities of NS5 WT D2 and the chimeric NS5 proteins with or without the K74I mutation are similar. Taken together, our results suggest that evolution of the functional interactions involving the chimeric NS5 protein encoded by the viral genome species is essential for gain of viral replication fitness.
authors.affiliation: From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and.
authors.forename: Tadahisa
authors.initials: T
authors.lastname: Teramoto
authors.affiliation: From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and.
authors.forename: Siwaporn
authors.initials: S
authors.lastname: Boonyasuppayakorn
authors.affiliation: From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and.
authors.forename: Misty
authors.initials: M
authors.lastname: Handley
authors.affiliation: the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555-0156.
authors.forename: Kyung H
authors.initials: KH
authors.lastname: Choi
authors.affiliation: From the Department of Microbiology and Immunology, Georgetown University School of Medicine, Washington, D. C. 20057 and rp55@georgetown.edu.
authors.forename: Radhakrishnan
authors.initials: R
authors.lastname: Padmanabhan
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D006224:Cricetinae; D003716:Dengue Virus / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D056084:Genetic Fitness; D016679:Genome, Viral; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012703:Serotyping; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D014774:Virulence / Q000235:genetics / Q000502:physiology; D014779:Virus Replication / Q000235:genetics
chemical_list: C582223:NS5 protein, dengue virus; D012367:RNA, Viral; C039919:RNA, recombinant; D017361:Viral Nonstructural Proteins; D012313:RNA
keywords: Flavivirus; Infectious Disease; Molecular Evolution; Protein-Protein Interaction; RNA Virus