TY - JOUR

T1 - Alleles A and B of non-structural protein 1 of avian influenza A viruses differentially inhibit beta interferon production in human and mink lung cells

AU - Munir, Muhammad

AU - Zohari, Siamak

AU - Metreveli, Giorgi

AU - Baule, Claudia

AU - Belák, Sándor

AU - Berg, Mikael

PY - 2011/9/1

Y1 - 2011/9/1

N2 - Non-structural protein 1 (NS1) counteracts the production of host type I interferons (IFN-α/β) for the efficient replication and pathogenicity of influenza A viruses. Here, we reveal another dimension of the NS1 protein of avian influenza A viruses in suppressing IFN-β production in cultured cell lines. We found that allele A NS1 proteins of H6N8 and H4N6 have a strong capacity to inhibit the activation of IFN-β production, compared with allele B from corresponding subtypes, as measured by IFN stimulatory response element (ISRE) promoter activation, IFN-β mRNA transcription and IFN-β protein expression. Furthermore, the ability to suppress IFN-β promoter activation was mapped to the C-terminal effector domain (ED), while the RNA-binding domain (RBD) alone was unable to suppress IFN-β promoter activation. Chimeric studies indicated that when the RBD of allele A was fused to the ED of allele B, it was a strong inhibitor of IFN-β promoter activity. This shows that well-matched ED and RBD are crucial for the function of the NS1 protein and that the RBD could be one possible cause for this differential IFN-β inhibition. Notably, mutagenesis studies indicated that the F103Y and Y103F substitutions in alleles A and B, respectively, do not influence the ISRE promoter activation. Apart from dsRNA signalling, differences were observed in the expression pattern of NS1 in transfected human and mink lung cells. This study therefore expands the versatile nature of the NS1 protein in inhibiting IFN responses at multiple levels, by demonstrating for the first time that it occurs in a manner dependent on allele type.

AB - Non-structural protein 1 (NS1) counteracts the production of host type I interferons (IFN-α/β) for the efficient replication and pathogenicity of influenza A viruses. Here, we reveal another dimension of the NS1 protein of avian influenza A viruses in suppressing IFN-β production in cultured cell lines. We found that allele A NS1 proteins of H6N8 and H4N6 have a strong capacity to inhibit the activation of IFN-β production, compared with allele B from corresponding subtypes, as measured by IFN stimulatory response element (ISRE) promoter activation, IFN-β mRNA transcription and IFN-β protein expression. Furthermore, the ability to suppress IFN-β promoter activation was mapped to the C-terminal effector domain (ED), while the RNA-binding domain (RBD) alone was unable to suppress IFN-β promoter activation. Chimeric studies indicated that when the RBD of allele A was fused to the ED of allele B, it was a strong inhibitor of IFN-β promoter activity. This shows that well-matched ED and RBD are crucial for the function of the NS1 protein and that the RBD could be one possible cause for this differential IFN-β inhibition. Notably, mutagenesis studies indicated that the F103Y and Y103F substitutions in alleles A and B, respectively, do not influence the ISRE promoter activation. Apart from dsRNA signalling, differences were observed in the expression pattern of NS1 in transfected human and mink lung cells. This study therefore expands the versatile nature of the NS1 protein in inhibiting IFN responses at multiple levels, by demonstrating for the first time that it occurs in a manner dependent on allele type.

KW - Alleles

KW - Animals

KW - Cell Line

KW - Epithelial Cells

KW - Humans

KW - Influenza A virus

KW - Interferon-beta

KW - Lung

KW - Mink

KW - Mutagenesis, Site-Directed

KW - Mutant Proteins

KW - Recombinant Proteins

KW - Recombination, Genetic

KW - Viral Nonstructural Proteins

KW - Virulence Factors

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1099/vir.0.031716-0

DO - 10.1099/vir.0.031716-0

M3 - Journal article

C2 - 21632557

VL - 92

SP - 2111

EP - 2121

JO - Journal of General Virology

JF - Journal of General Virology

SN - 0022-1317

IS - 9

ER -