title: Genetic interaction of flavivirus nonstructural proteins NS1 and NS4A as a determinant of replicase function.
abstract: Nonstructural protein 1 (NS1) of yellow fever virus (YF) is a glycoprotein localized to extracytoplasmic compartments within infected cells. We have previously shown that NS1 can be supplied in trans and is required for viral RNA replication, a process thought to occur in membrane-bound cytoplasmic complexes. Here we report that the NS1 gene from a related virus, dengue virus (DEN), is unable to function in the process of YF RNA replication. This virus-specific incompatibility leads to a lack of initial minus-strand accumulation, suggesting that DEN NS1 is unable to productively interact with the YF replicase. Based on a YF deletion mutant that requires NS1 in trans, a genetic screen for suppressor mutants was used to select virus variants able to utilize DEN NS1. In three independent selections, a single mutation was mapped to the NS4A gene, which encodes a putative transmembrane replicase component. This mutation, as well as several additional mutations, was engineered into the NS1-deficient genome and confirmed a genetic interaction between NS1 and NS4A. These findings suggest a potential mechanism for integrating NS1 into the cytoplasmic process of RNA replication.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Lindenbach
authors.forename: C M
authors.initials: CM
authors.lastname: Rice
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D008969:Molecular Sequence Data; D012367:RNA, Viral / Q000096:biosynthesis*; D012324:RNA-Dependent RNA Polymerase / Q000502:physiology*; D017361:Viral Nonstructural Proteins / Q000502:physiology*; D015005:Yellow fever virus / Q000235:genetics*
chemical_list: C100315:NS1 protein, Flavivirus; C080106:NS4A protein, flavivirus; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; D012324:RNA-Dependent RNA Polymerase