Nuclear MxA proteins form a complex with influenza virus NP and inhibit the transcription of the engineered influenza virus genome

Abstract

Mx proteins belong to the dynamin superfamily of high molecular weight GTPases and interfere with multiplication of a wide variety of viruses. Earlier studies show that nuclear mouse Mx1 and human MxA designed to be localized in the nucleus inhibit the transcription step of the influenza virus genome. Here we set a transient influenza virus transcription system using luciferase as a reporter gene and cells expressing the three RNA polymerase subunits, PB1, PB2 and PA, and NP. We used this reporter assay system and nuclear-localized MxA proteins to get clues for elucidating the anti-influenza virus activity of MxA. Nuclear-localized VP16-MxA and MxA-TAg NLS strongly interfered with the influenza virus transcription. Over-expression of PB2 led to a slight resumption of the transcription inhibition by nuclear MxA, whereas over-expression of PB1 and PA did not affect the MxA activity. Of interest is that the inhibitory activity of the nuclear MxA was markedly neutralized by over-expression of NP. An NP devoid of its C-terminal region, but containing the N-terminal RNA binding domain, also neutralized the VP16-MxA activity in a dose-dependent manner, whereas an NP lacking the N-terminal region did not affect the VP16-MxA activity. Further, not only VP16-MxA but also the wild-type MxA was found to interact with NP in influenza virus-infected cells. This indicates that the nuclear MxA suppresses the influenza virus transcription by interacting with not only PB2 but also NP.

Interferon-Induced Expression of MxA in the Respiratory Tract of Rhesus Macaques Is Suppressed by Influenza Virus Replication

“…These results suggest that, in mouse 3T3 cells, MxA interferes with either intracytoplasmic transport of viral mRNAs, viral protein synthesis, or translocation of newly synthesized viral proteins to the cell nucleus (33). More recent studies have shown that if MxA is artificially made to translocate into the nucleus of 3T3 cells, it binds newly synthesized influenza virus nucleoprotein, preventing viral transcription (4,31,33). There is only one report of MxA-mediated antiviral activity in human cells; it has been demonstrated that MxA inhibits cytoplasmic LaCrosse virus genome replication (34).…”

“…Viral protein synthesis and genome amplification is strongly inhibited in these cells, although viral mRNAs direct viral protein synthesis in vitro and appear to be efficiently transported to the cell cytoplasm. These results suggest that, in mouse 3T3 cells, MxA interferes with either intracytoplasmic transport of viral mRNAs, viral protein synthesis, or translocation of newly synthesized viral proteins to the cell nucleus (33). More recent studies have shown that if MxA is artificially made to translocate into the nucleus of 3T3 cells, it binds newly synthesized influenza virus nucleoprotein, preventing viral transcription (4,31,33).…”

Reconstitution of human rRNA gene transcription in mouse cells by complete SL1 complex

“…Although pmPolI was originally called as pHMP1 in a previous report (Turan et al, 2004), we redesignated this plasmid pmPolI because it makes it easy to distinguish plasmids carrying the human or mouse rDNA promoter. As shown in the human reporter system, we constructed three reporter plasmids carrying mutations in the mouse rDNA promoter that abrogate activity (Fig.…”

Oligomerization and GTP-binding Requirements of MxA for Viral Target Recognition and Antiviral Activity against Influenza A Virus

“…Adaptive mutations in a surface-exposed cluster of amino acids have been identified to counteract the restriction by MxA (19,20). So far, there is only little evidence for a physical interaction between NP of IAV and MxA (21). We have shown recently that MxA binds to UAP56, a DEAD-box helicase.…”