The NS1 protein of influenza B virus binds 5'-triphosphorylated dsRNA to suppress RIG-I activation and the antiviral innate immune response

Woltz, R.; Schweibenz, B.; Tsutakawa, S. E.; Zhao, C.; Ma, L.-C.; Shurina, B.; Hura, G. L.; John, R.; Vorobiev, S.; Gurla, S.; Solotchi, M.; Tainer, J. A.; Krug, R. M.; Patel, S. S.; Montelione, G. T.

doi:10.1101/2023.09.25.559316

bioRxiv · 10.1101/2023.09.25.559316

The NS1 protein of influenza B virus binds 5'-triphosphorylated dsRNA to suppress RIG-I activation and the antiviral innate immune response

Woltz, R.·Schweibenz, B.·Tsutakawa, S. E.·Zhao, C.·Ma, L.-C.·Shurina, B.·Hura, G. L.·John, R.·Vorobiev, S.·Gurla, S.·Solotchi, M.·Tainer, J. A.·Krug, R. M.·Patel, S. S.·Montelione, G. T.

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Abstract

Influenza A and B viruses overcome the host antiviral response to cause a contagious and often severe human respiratory disease. Here, integrative structural biology and biochemistry studies on non- structural protein 1 of influenza B virus (NS1B) reveal a previously unrecognized viral mechanism for innate immune evasion. Conserved basic groups of its C-terminal domain (NS1B-CTD) bind 5- triphosphorylated double-stranded RNA (5ppp-dsRNA), the primary pathogen-associated feature that activates the host retinoic acid-inducible gene I protein (RIG-I) to initiate interferon synthesis and the cellular antiviral response. Like RIG-I, NS1B-CTD preferentially binds blunt-end 5ppp-dsRNA. NS1B-CTD also competes with RIG-I for binding 5ppp-dsRNA, and thus suppresses activation of RIG-Is ATPase activity. Although the NS1B N-terminal domain also binds dsRNA, it utilizes a different binding mode and lacks 5ppp-dsRNA end preferences. In cells infected with wild-type influenza B virus, RIG-I activation is inhibited. In contrast, RIG-I activation and the resulting phosphorylation of transcription factor IRF-3 are not inhibited in cells infected with a mutant virus encoding NS1B with a R208A substitution it its CTD that eliminates its 5ppp-dsRNA binding activity. These results reveal a novel mechanism in which NS1B binds 5ppp-dsRNA to inhibit the RIG-I antiviral response during influenza B virus infection, and open the door to new avenues for antiviral drug discovery.

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Woltz, R., Schweibenz, B., Tsutakawa, S. E., Zhao, C., Ma, L.-C., Shurina, B., Hura, G. L., John, R., Vorobiev, S., Gurla, S., Solotchi, M., Tainer, J. A., Krug, R. M., Patel, S. S., Montelione, G. T.. 2023-09-25. The NS1 protein of influenza B virus binds 5'-triphosphorylated dsRNA to suppress RIG-I activation and the antiviral innate immune response. https://doi.org/10.1101/2023.09.25.559316

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