scholarly journals NS1-Binding Protein (NS1-BP): a Novel Human Protein That Interacts with the Influenza A Virus Nonstructural NS1 Protein Is Relocalized in the Nuclei of Infected Cells

1998 ◽  
Vol 72 (9) ◽  
pp. 7170-7180 ◽  
Author(s):  
Thorsten Wolff ◽  
Robert E. O’Neill ◽  
Peter Palese
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Genetic Interaction ◽  
Binding Protein ◽  
Mrna Splicing ◽  
Mutant Protein ◽  
Dominant Negative Effect ◽  
Ns1 Protein ◽  
Spliceosome Assembly ◽  
Infected Cells

ABSTRACT We used the yeast interaction trap system to identify a novel human 70-kDa protein, termed NS1-binding protein (NS1-BP), which interacts with the nonstructural NS1 protein of the influenza A virus. The genetic interaction was confirmed by the specific coprecipitation of the NS1 protein from solution by a glutathioneS-transferase–NS1-BP fusion protein and glutathione-Sepharose. NS1-BP contains an N-terminal BTB/POZ domain and five kelch-like tandem repeat elements of ∼50 amino acids. In noninfected cells, affinity-purified antibodies localized NS1-BP in nuclear regions enriched with the spliceosome assembly factor SC35, suggesting an association of NS1-BP with the cellular splicing apparatus. In influenza A virus-infected cells, NS1-BP relocalized throughout the nucleoplasm and appeared distinct from the SC35 domains, which suggests that NS1-BP function may be disturbed or altered. The addition of a truncated NS1-BP mutant protein to a HeLa cell nuclear extract efficiently inhibited pre-mRNA splicing but not spliceosome assembly. This result could be explained by a possible dominant-negative effect of the NS1-BP mutant protein and suggests a role of the wild-type NS1-BP in promoting pre-mRNA splicing. These data suggest that the inhibition of splicing by the NS1 protein may be mediated by binding to NS1-BP.

scholarly journals Influenza C Virus NS1 Protein Upregulates the Splicing of Viral mRNAs

2009 ◽  
Vol 84 (4) ◽  
pp. 1957-1966 ◽  
Author(s):  
Yasushi Muraki ◽  
Takatoshi Furukawa ◽  
Yoshihiko Kohno ◽  
Yoko Matsuzaki ◽  
Emi Takashita ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Influenza A ◽  
Mrna Splicing ◽  
Viral Mrna ◽  
Ns1 Protein ◽  
M Gene ◽  
Transfected Cells ◽  
Ns Gene ◽  
Influenza C Virus ◽  
Infected Cells

ABSTRACT Pre-mRNAs of the influenza A virus M and NS genes are poorly spliced in virus-infected cells. By contrast, in influenza C virus-infected cells, the predominant transcript from the M gene is spliced mRNA. The present study was performed to investigate the mechanism by which influenza C virus M gene-specific mRNA (M mRNA) is readily spliced. The ratio of M1 encoded by a spliced M mRNA to CM2 encoded by an unspliced M mRNA in influenza C virus-infected cells was about 10 times larger than that in M gene-transfected cells, suggesting that a viral protein(s) other than M gene translational products facilitates viral mRNA splicing. RNase protection assays showed that the splicing of M mRNA in infected cells was much higher than that in M gene-transfected cells. The unspliced and spliced mRNAs of the influenza C virus NS gene encode two nonstructural (NS) proteins, NS1(C/NS1) and NS2(C/NS2), respectively. The introduction of premature translational termination into the NS gene, which blocked the synthesis of the C/NS1 and C/NS2 proteins, drastically reduced the splicing of NS mRNA, raising the possibility that C/NS1 or C/NS2 enhances viral mRNA splicing. The splicing of influenza C virus M mRNA was increased by coexpression of C/NS1, whereas it was reduced by coexpression of the influenza A virus NS1 protein (A/NS1). The splicing of influenza A virus M mRNA was also increased by coexpression of C/NS1, though it was inhibited by that of A/NS1. These results suggest that influenza C virus NS1, but not A/NS1, can upregulate viral mRNA splicing.

scholarly journals The NS1 Protein of Influenza A Virus Blocks RIG-I-Mediated Activation of the Noncanonical NF-κB Pathway and p52/RelB-Dependent Gene Expression in Lung Epithelial Cells

2012 ◽  
Vol 86 (18) ◽  
pp. 10211-10217 ◽  
Author(s):  
Andrea Rückle ◽  
Emanuel Haasbach ◽  
Ilkka Julkunen ◽  
Oliver Planz ◽  
Christina Ehrhardt ◽  
...  
Keyword(s):  
Gene Expression ◽  
Epithelial Cells ◽  
Influenza A Virus ◽  
Influenza A ◽  
Target Gene ◽  
Lung Epithelial Cells ◽  
Ns1 Protein ◽  
Antiviral Immune Response ◽  
Lung Epithelial ◽  
Infected Cells

Influenza A virus (IAV) infection of epithelial cells activates NF-κB transcription factors via the canonical NF-κB signaling pathway, which modulates both the antiviral immune response and viral replication. Since almost nothing is known so far about a function of noncanonical NF-κB signaling after IAV infection, we tested infected cells for activation of p52 and RelB. We show that the viral NS1 protein strongly inhibits RIG-I-mediated noncanonical NF-κB activation and expression of the noncanonical target gene CCL19.

scholarly journals The accumulation of influenza A virus segment 7 spliced mRNAs is regulated by the NS1 protein

2012 ◽  
Vol 93 (1) ◽  
pp. 113-118 ◽  
Author(s):  
Nicole C. Robb ◽  
Ervin Fodor
Keyword(s):  
Influenza Virus ◽  
Viral Infection ◽  
Influenza A Virus ◽  
Influenza A ◽  
Rna Binding ◽  
Mrna Splicing ◽  
Ns1 Protein ◽  
Binding Ability ◽  
Alternatively Spliced ◽  
Transcription And Replication

The influenza A virus M1 mRNA is alternatively spliced to produce M2 mRNA, mRNA3, and in some cases, M4 mRNA. Splicing of influenza mRNAs is carried out by the cellular splicing machinery and is thought to be regulated, as both spliced and unspliced mRNAs encode proteins. In this study, we used radioactively labelled primers to investigate the accumulation of spliced and unspliced M segment mRNAs in viral infection and ribonucleoprotein (RNP) reconstitution assays in which only the minimal components required for transcription and replication to occur were expressed. We found that co-expression of the viral NS1 protein in an RNP reconstitution assay altered the accumulation of spliced mRNAs compared with when it was absent, and that this activity was dependent on the RNA-binding ability of NS1. These findings suggest that the NS1 protein plays a role in the regulation of splicing of influenza virus M1 mRNA.

scholarly journals ISG15 conjugation system targets the viral NS1 protein in influenza A virus–infected cells

2010 ◽  
Vol 107 (5) ◽  
pp. 2253-2258 ◽  
Author(s):  
Chen Zhao ◽  
Tien-Ying Hsiang ◽  
Rei-Lin Kuo ◽  
Robert M. Krug
Keyword(s):  
Antiviral Activity ◽  
Influenza A Virus ◽  
Viral Protein ◽  
Influenza A ◽  
Rna Binding ◽  
Acceptor Site ◽  
Ns1 Protein ◽  
Conjugation System ◽  
Infected Cells ◽  
Ns1a Protein

ISG15 is an IFN-α/β–induced, ubiquitin-like protein that is conjugated to a wide array of cellular proteins through the sequential action of three conjugation enzymes that are also induced by IFN-α/β. Recent studies showed that ISG15 and/or its conjugates play an important role in protecting cells from infection by several viruses, including influenza A virus. However, the mechanism by which ISG15 modification exerts antiviral activity has not been established. Here we extend the repertoire of ISG15 targets to a viral protein by demonstrating that the NS1 protein of influenza A virus (NS1A protein), an essential, multifunctional protein, is ISG15 modified in virus-infected cells. We demonstrate that the major ISG15 acceptor site in the NS1A protein in infected cells is a critical lysine residue (K41) in the N-terminal RNA-binding domain (RBD). ISG15 modification of K41 disrupts the association of the NS1A RBD domain with importin-α, the protein that mediates nuclear import of the NS1A protein, whereas the RBD retains its double-stranded RNA-binding activity. Most significantly, we show that ISG15 modification of K41 inhibits influenza A virus replication and thus contributes to the antiviral action of IFN-β. We also show that the NS1A protein directly and specifically binds to Herc5, the major E3 ligase for ISG15 conjugation in human cells. These results establish a “loss of function” mechanism for the antiviral activity of the IFN-induced ISG15 conjugation system, namely, that it inhibits viral replication by conjugating ISG15 to a specific viral protein, thereby inhibiting its function.

scholarly journals Immunologic studies on the influenza A virus nonstructural protein NS1.

1982 ◽  
Vol 156 (1) ◽  
pp. 243-254 ◽  
Author(s):  
M W Shaw ◽  
E W Lamon ◽  
R W Compans
Keyword(s):  
Influenza Virus ◽  
Influenza A Virus ◽  
Influenza A ◽  
Nonstructural Protein ◽  
Antigenic Drift ◽  
Ns1 Protein ◽  
Influenza A Viruses ◽  
Cytoplasmic Inclusions ◽  
Infected Cells ◽  
Virus Isolates

We purified the major influenza virus nonstructural protein, designated NS1, from cytoplasmic inclusions that were solubilized and used to raise antisera in rabbits. One of the antisera was found to be specific for NS1 by complement fixation tests and analyses of immune precipitates. Antiserum to NS1 isolated from cells infected with A/WSN/33 virus specifically precipitated NS1 from extracts of cells infected with seven distinct isolates of influenza A virus representing five different antigenic subtypes. These included A/WSN/33, A/PR/8/34, A/FW/5/50, A/USSR/90/77, A/RI/5+/57, A/Victoria/3/75, and A/Swine /1977/31; however, NS1 from cells infected with B/Lee/40 virus was not precipitated. Radioimmunoassays using radioiodinated NS1 protein from A/WSN virus-infected cells and unlabeled cytoplasmic extracts of cells infected with various strains of influenza virus as competitors indicated significant antigenic cross-reactivities for the NS1 proteins of all influenza A viruses tested. The results suggest a gradual antigenic drift over the 45 yr separating the earliest and most recent virus isolates examined. Thus, compared with the virion neuraminidase and hemagglutinin antigens, NS1 appears to be highly conserved in different influenza A virus isolates.

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