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Mutant influenza viruses with a defective NS1 protein cannot block the activation of PKR in infected cells

E Hatada1, S Saito, R Fukuda

  • 1Department of Biochemistry, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-0934, Japan.

Journal of Virology
|February 11, 1999
PubMed

Insights

Influenza A virus NS1 protein binds viral RNA, preventing activation of the protein kinase PKR. Mutants show impaired RNA binding, leading to PKR activation and reduced viral protein synthesis.

Area of Science:

  • Virology
  • Molecular Biology
  • Immunology

Background:

  • Interferon-induced double-stranded RNA-dependent protein kinase (PKR) plays a crucial role in antiviral defense.
  • Influenza A virus employs mechanisms to evade the host immune response, including PKR inhibition.

Purpose of the Study:

  • To investigate the role of the influenza A virus NS1 protein in PKR activation and inhibition.
  • To characterize the impact of NS1 mutations on RNA binding, PKR activity, and viral protein synthesis.

Main Methods:

  • In vitro activation of PKR by viral RNA.
  • Assessing NS1 protein's ability to bind viral RNA.
  • Analyzing phosphorylation of PKR and eukaryotic translation initiation factor 2 alpha (eIF2alpha) in cells infected with wild-type and mutant viruses.
  • Evaluating viral protein synthesis at different temperatures.

Main Results:

  • Viral genome RNA activated PKR, leading to eIF2alpha phosphorylation.
  • The NS1 protein inhibited PKR activation by binding to viral RNA.
  • Mutant NS1 proteins with temperature-sensitive RNA binding failed to repress PKR autophosphorylation.
  • This resulted in elevated eIF2alpha phosphorylation and temperature-sensitive viral protein synthesis.

Conclusions:

  • The NS1 protein's RNA-binding activity is essential for suppressing PKR-mediated antiviral responses.
  • Impaired NS1 function leads to increased PKR and eIF2alpha phosphorylation, consequently hindering viral replication.

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