The role of nuclear NS1 protein in highly pathogenic H5N1 influenza viruses

Microbes Infect. 2017 Dec;19(12):587-596. doi: 10.1016/j.micinf.2017.08.011. Epub 2017 Sep 10.


The non-structural protein (NS1) of influenza A viruses (IAV) performs multiple functions during viral infection. NS1 contains two nuclear localization signals (NLS): NLS1 and NLS2. The NS1 protein is located predominantly in the nucleus during the early stages of infection and subsequently exported to the cytoplasm. A nonsense mutation that results in a large deletion in the carboxy-terminal region of the NS1 protein that contains the NLS2 domain was found in some IAV subtypes, including highly pathogenic avian influenza (HPAI) H7N9 and H5N1 viruses. We introduced different mutations into the NLS domains of NS1 proteins in various strains of IAV, and demonstrated that mutation of the NLS2 region in the NS1 protein of HPAI H5N1 viruses severely affects its nuclear localization pattern. H5N1 viruses expressing NS1 protein that is unable to localize to the nucleus are less potent in antagonizing cellular antiviral responses than viruses expressing wild-type NS1. However, no significant difference was observed with respect to viral replication and pathogenesis. In contrast, the replication and antiviral defenses of H1N1 viruses are greatly attenuated when nuclear localization of the NS1 protein is blocked. Our data reveals a novel functional plasticity for NS1 proteins among different IAV subtypes.

Keywords: H5N1; HPAI; Influenza virus; NS1; Nuclear localization signal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Animals
  • Cell Line, Tumor
  • Cell Nucleus / pathology*
  • Cell Nucleus / virology
  • Dogs
  • Female
  • Host-Pathogen Interactions / immunology
  • Humans
  • Influenza A Virus, H1N1 Subtype / genetics
  • Influenza A Virus, H5N1 Subtype / genetics*
  • Influenza A Virus, H5N1 Subtype / pathogenicity*
  • Influenza A Virus, H7N9 Subtype / genetics
  • Influenza, Human / pathology*
  • Influenza, Human / virology
  • Madin Darby Canine Kidney Cells
  • Mice
  • Mice, Inbred BALB C
  • Mutation / genetics
  • Nuclear Localization Signals / physiology
  • Orthomyxoviridae Infections / pathology*
  • Orthomyxoviridae Infections / virology
  • Protein Domains / genetics
  • Viral Nonstructural Proteins / genetics*
  • Viral Nonstructural Proteins / metabolism
  • Virus Replication / genetics*


  • INS1 protein, influenza virus
  • Nuclear Localization Signals
  • Viral Nonstructural Proteins