Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis

<p>Abstract</p> <p>Background</p> <p>Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the <it>Reoviridae</it> family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (R...

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Main Authors: Boyce Mark, Celma Cristina C P, Roy Polly
Format: Article
Language:English
Published: BMC 2012-08-01
Series:Virology Journal
Subjects:
NS1
Online Access:http://www.virologyj.com/content/9/1/178
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spelling doaj-aba3e781b0e541bdbef94b82f6982aa32020-11-24T21:44:57ZengBMCVirology Journal1743-422X2012-08-019117810.1186/1743-422X-9-178Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesisBoyce MarkCelma Cristina C PRoy Polly<p>Abstract</p> <p>Background</p> <p>Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the <it>Reoviridae</it> family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the <it>Orbivirus</it> genus has not been investigated.</p> <p>Results</p> <p>Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3<sup>′</sup> poly(A) sequence identifying the 3<sup>′</sup> end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA.</p> <p>Conclusions</p> <p>NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein synthesis during infection.</p> http://www.virologyj.com/content/9/1/178BluetongueNS1TranslationProtein synthesis
collection DOAJ
language English
format Article
sources DOAJ
author Boyce Mark
Celma Cristina C P
Roy Polly
spellingShingle Boyce Mark
Celma Cristina C P
Roy Polly
Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
Virology Journal
Bluetongue
NS1
Translation
Protein synthesis
author_facet Boyce Mark
Celma Cristina C P
Roy Polly
author_sort Boyce Mark
title Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
title_short Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
title_full Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
title_fullStr Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
title_full_unstemmed Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
title_sort bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis
publisher BMC
series Virology Journal
issn 1743-422X
publishDate 2012-08-01
description <p>Abstract</p> <p>Background</p> <p>Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the <it>Reoviridae</it> family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the <it>Orbivirus</it> genus has not been investigated.</p> <p>Results</p> <p>Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3<sup>′</sup> poly(A) sequence identifying the 3<sup>′</sup> end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA.</p> <p>Conclusions</p> <p>NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein synthesis during infection.</p>
topic Bluetongue
NS1
Translation
Protein synthesis
url http://www.virologyj.com/content/9/1/178
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