The cytoplasmic location of chicken mx is not the determining factor for its lack of antiviral activity

• Published in: PloS one 2010-08, Vol.5 (8), p.e12151-e12151
• Main Authors: Benfield, Camilla T O, Lyall, Jon W, Tiley, Laurence S
• Format: Article
• Language: English
• Subjects: Alleles; Amino acids; Animals; Antigen T (large); Antiviral activity; Antiviral Agents - metabolism; Antiviral Agents - pharmacology; Avian flu; Biological response modifiers; Cell culture; Cell Line; Cell Nucleus - metabolism; Chickens; Cloning; Cytokines; Cytoplasm - metabolism; Dynamin; Endoplasmic reticulum; Flow cytometry; G proteins; Gene expression; Genes; Genetic aspects; Genomes; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; GTP-Binding Proteins - pharmacology; Health aspects; Humans; Infections; Influenza; Influenza A; Influenza A Virus, H5N1 Subtype - drug effects; Influenza A Virus, H5N1 Subtype - physiology; Inhibition; Interferon; Medical research; Mice; Myxovirus Resistance Proteins; N-Terminus; Newcastle disease; Newcastle disease virus; Newcastle disease virus - drug effects; Nuclei; Nuclei (cytology); Orthomyxovirus; Phosphatase; Plasmids; Polymorphism; Polymorphism, Genetic - genetics; Position (location); Poultry; Protein Transport; Proteins; Ribonucleic acid; RNA; RNA viruses; Simian virus 40; T cells; Thogoto virus; Thogotovirus - drug effects; Ultraviolet radiation; Vesiculovirus - drug effects; Veterinary medicine; Virology; Virology/Host Antiviral Responses; Virology/Mechanisms of Resistance and Susceptibility, including Host Genetics; Virus replication; Virus Replication - drug effects; Viruses
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0012151

Chicken Mx belongs to the Mx family of interferon-induced dynamin-like GTPases, which in some species possess potent antiviral properties. Conflicting data exist for the antiviral capability of chicken Mx. Reports of anti-influenza activity of alleles encoding an Asn631 polymorphism have not been supported by subsequent studies. The normal cytoplasmic localisation of chicken Mx may influence its antiviral capacity. Here we report further studies to determine the antiviral potential of chicken Mx against Newcastle disease virus (NDV), an economically important cytoplasmic RNA virus of chickens, and Thogoto virus, an orthomyxovirus known to be exquisitely sensitive to the cytoplasmic MxA protein from humans. We also report the consequences of re-locating chicken Mx to the nucleus. Chicken Mx was tested in virus infection assays using NDV. Neither the Asn631 nor Ser631 Mx alleles (when transfected into 293T cells) showed inhibition of virus-directed gene expression when the cells were subsequently infected with NDV. Human MxA however did show significant inhibition of NDV-directed gene expression. Chicken Mx failed to inhibit a Thogoto virus (THOV) minireplicon system in which the cytoplasmic human MxA protein showed potent and specific inhibition. Relocalisation of chicken Mx to the nucleus was achieved by inserting the Simian Virus 40 large T antigen nuclear localisation sequence (SV40 NLS) at the N-terminus of chicken Mx. Nuclear re-localised chicken Mx did not inhibit influenza (A/PR/8/34) gene expression during virus infection in cell culture or influenza polymerase activity in A/PR/8/34 or A/Turkey/50-92/91 minireplicon systems. The chicken Mx protein (Asn631) lacks inhibitory effects against THOV and NDV, and is unable to suppress influenza replication when artificially re-localised to the cell nucleus. Thus, the natural cytoplasmic localisation of the chicken Mx protein does not account for its lack of antiviral activity.