title: Severe acute respiratory syndrome coronavirus nsp1 facilitates efficient propagation in cells through a specific translational shutoff of host mRNA.
abstract: Severe acute respiratory syndrome (SARS) coronavirus (SCoV) is an enveloped virus containing a single-stranded, positive-sense RNA genome. Nine mRNAs carrying a set of common 5' and 3' untranslated regions (UTR) are synthesized from the incoming viral genomic RNA in cells infected with SCoV. A nonstructural SCoV nsp1 protein causes a severe translational shutoff by binding to the 40S ribosomal subunits. The nsp1-40S ribosome complex further induces an endonucleolytic cleavage near the 5'UTR of host mRNA. However, the mechanism by which SCoV viral proteins are efficiently produced in infected cells in which host protein synthesis is impaired by nsp1 is unknown. In this study, we investigated the role of the viral UTRs in evasion of the nsp1-mediated shutoff. Luciferase activities were significantly suppressed in cells expressing nsp1 together with the mRNA carrying a luciferase gene, while nsp1 failed to suppress luciferase activities of the mRNA flanked by the 5'UTR of SCoV. An RNA-protein binding assay and RNA decay assay revealed that nsp1 bound to stem-loop 1 (SL1) in the 5'UTR of SCoV RNA and that the specific interaction with nsp1 stabilized the mRNA carrying SL1. Furthermore, experiments using an SCoV replicon system showed that the specific interaction enhanced the SCoV replication. The specific interaction of nsp1 with SL1 is an important strategy to facilitate efficient viral gene expression in infected cells, in which nsp1 suppresses host gene expression. Our data indicate a novel mechanism of viral gene expression control by nsp1 and give new insight into understanding the pathogenesis of SARS.
authors.affiliation: Global COE Program, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Tanaka
authors.forename: Wataru
authors.initials: W
authors.lastname: Kamitani
authors.forename: Marta L
authors.initials: ML
authors.lastname: DeDiego
authors.forename: Luis
authors.initials: L
authors.lastname: Enjuanes
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Matsuura
mesh_terms: D020121:5' Untranslated Regions; D002460:Cell Line; D015967:Gene Expression Regulation, Viral; D057809:HEK293 Cells; D006801:Humans; D055029:Inverted Repeat Sequences; D010441:Peptide Chain Elongation, Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000378:metabolism*; D045169:Severe Acute Respiratory Syndrome / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication / Q000235:genetics
chemical_list: D020121:5' Untranslated Regions; D012333:RNA, Messenger; D022661:RNA, Untranslated; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins; C521592:Nsp1 protein, SARS coronavirus; D012324:RNA-Dependent RNA Polymerase