Effects of the C-Terminal Truncation in NS1 Protein of the 2009 Pandemic H1N1 Influenza Virus on Host Gene Expression

Jiagang Tu,Meilin Jin,Zongzheng Zhao,Wenting Zhang,Jing Guo,Anding Zhang,Hongbo Zhou,Cheng Liu,Huanchun Chen,Andrew Pekosz

doi:10.1371/journal.pone.0026175

Jiagang Tu, Meilin Jin + Show 8 more

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https://doi.org/10.1371/journal.pone.0026175

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Journal: PloS one	Publication Date: Oct 12, 2011
Citations: 35	License type: CC BY 4.0

Affiliation: Huazhong Agricultural University

Abstract

The 2009 pandemic H1N1 influenza virus encodes an NS1 protein with 11 amino acids (aa) truncation at the C-terminus. The C-terminal tail of influenza virus NS1 protein constitutes a nucleolar localization signal (NoLS) and is the binding domain of the cellular pre-mRNA processing protein, poly(A)-binding protein II (PABII). Here, our studies showed that the C-terminal-truncated NS1 of the 2009 pandemic virus was inefficient at blocking host gene expression, extension of the truncated NS1 to its full length increased the inhibition of host gene expression. Mechanistically, this increased inhibition of host gene expression by the full-length NS1 was not associated with nucleolar localization, but was due to the restoration of NS1's binding capacity to PABII. Furthermore, in vitro and in vivo characterization of two recombinant viruses encoding either the C-terminal 11-aa truncated or full-length NS1 of the 2009 pandemic virus showed that the C-terminal 11-aa truncation in NS1 did not significantly alter virus replication, but increased virus pathogenicity in mice.

Highlights

A novel swine-origin H1N1 influenza virus emerged in Mexico in April 2009 [1,2] and had spread globally prompting the World Health Organization (WHO) to raise this global pandemic to phase 6
We meassured the antiviral gene IFN-b mRNA production in A549 cells infected with recombinant virus rPR8-Mexico/4486/2009 H1N1 (Mex) NS1/219 or rPR8-Mex NS1/230 by quantitative real-time PCR (qRT-PCR)
Viral M gene mRNA production was similar at each time point, while the antiviral gene IFN-b mRNA production was higher when cells were infected with virus rPR8-Mex NS1/219 than with virus rPR8-Mex NS1/ 230 (Figure 1C)

Summary

Introduction

A novel swine-origin H1N1 influenza virus emerged in Mexico in April 2009 [1,2] and had spread globally prompting the World Health Organization (WHO) to raise this global pandemic to phase 6. It caused mild disease in the majority of people, the 2009 pandemic virus was more pathogenic and induced higher amounts of pro-inflammatory cytokines and chemokines in mammalian models than human seasonal H1N1 influenza viruses [3]. NS1 protein inhibits host antiviral gene expression by both pre-transcriptional and post-transcriptional processes. NS1 can block the function of two antiviral proteins including 29-59oligoadenylate synthetase (OAS) [11] and serine/threonine protein kinase R (PKR) [12], stimulate phosphoinositide 3-kinase signaling (PI3K) by binding to p85b and/or CrkL [13,14,15,16], and limit host antiviral gene translation by binding to eIF4GI [17]

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