Restoration of replication-defective dengue type 1 virus bearing mutations in the N-terminal cytoplasmic portion of NS4A by additional mutations in NS4B.
Flavivirus NS4A has an N-terminal hydrophilic cytoplasmic portion; however, the role of this portion remains poorly understood. In this study, we show that a recombinant dengue type 1 virus (DENV-1) in which a subportion (amino acids 27-34) of the N-terminal portion of NS4A is replaced by the corresponding region from Japanese encephalitis virus (JEV) is defective in replication. Using the defective mutant clone NS4A(27-34(JEV)), we recovered suppressor mutant viruses that carry various non-synonymous mutations. Site-directed mutational analysis indicated that a single non-synonymous mutation in NS4B that is found in the suppressor viruses is sufficient to restore NS4A(27-34(JEV)). Recombinant DENV-1 with single mutations in NS4B had increased growth properties as compared to the wild-type virus and NS4A(27-34(JEV)) virus bearing the same NS4B mutation. Collectively, our results suggest that the NS4B mutation enhanced the growth of DENV-1, irrespective of the sequence of the 27-34 subportion NS4A.
Tajima
Shigeru
S
Department of Virology, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan. stajima@nih.go.jp
Takasaki
Tomohiko
T
Kurane
Ichiro
I
D000818:Animals; D002522:Chlorocebus aethiops; D003716:Dengue Virus / Q000235:genetics* / Q000502:physiology*; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication / Q000235:genetics* / Q000502:physiology
C080106:NS4A protein, flavivirus; C080107:NS4B protein, flavivirus; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins