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Updated: May 30, 2026
Co-immunoprecipitation of the Mouse Mx1 Protein with the Influenza A Virus Nucleoprotein
Published on: April 21, 2015
Interferon-induced antiviral protein MxA interacts with the cellular RNA helicases UAP56 and URH49
Christian Wisskirchen1, Thomas H Ludersdorfer, Dominik A Müller
1Institute of Medical Virology, University of Zurich, 8057 Zürich, Switzerland.
Abstract:
Mx proteins are a family of large GTPases that are induced exclusively by interferon-α/β and have a broad antiviral activity against several viruses, including influenza A virus (IAV). Although the antiviral activities of mouse Mx1 and human MxA have been studied extensively, the molecular mechanism of action remains largely unsolved. Because no direct interaction between Mx proteins and IAV proteins or RNA had been demonstrated so far, we addressed the question of whether Mx protein would interact with cellular proteins required for efficient replication of IAV. Immunoprecipitation of MxA revealed its association with two closely related RNA helicases, UAP56 and URH49. UAP56 and its paralog URH49 play an important role in IAV replication and are involved in nuclear export of IAV mRNAs and prevention of dsRNA accumulation in infected cells. In vitro binding assays with purified recombinant proteins revealed that MxA formed a direct complex with the RNA helicases. In addition, recombinant mouse Mx1 was also able to bind to UAP56 or URH49. Furthermore, the complex formation between cytoplasmic MxA and UAP56 or URH49 occurred in the perinuclear region, whereas nuclear Mx1 interacted with UAP56 or URH49 in distinct dots in the nucleus. Taken together, our data reveal that Mx proteins exerting antiviral activity can directly bind to the two cellular DExD/H box RNA helicases UAP56 and URH49. Moreover, the observed subcellular localization of the Mx-RNA helicase complexes coincides with the subcellular localization, where human MxA and mouse Mx1 proteins act antivirally. On the basis of these data, we propose that Mx proteins exert their antiviral activity against IAV by interfering with the function of the RNA helicases UAP56 and URH49.
Insights
Mx proteins, induced by interferon, directly bind to cellular RNA helicases UAP56 and URH49, revealing a novel antiviral mechanism against influenza A virus (IAV). This interaction interferes with viral replication by targeting key host factors.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Mx proteins are interferon-induced GTPases with broad antiviral activity, notably against influenza A virus (IAV).
- The precise molecular mechanisms underlying Mx protein antiviral functions, particularly interactions with host factors, remain largely unelucidated.
- Previous studies lacked evidence of direct interactions between Mx proteins and viral components or essential host factors.
Purpose of the Study:
- To investigate potential interactions between Mx proteins and cellular factors crucial for influenza A virus (IAV) replication.
- To elucidate the molecular mechanism by which Mx proteins exert their antiviral effects against IAV.
- To determine if Mx proteins directly bind to host cell proteins involved in IAV lifecycle.
Main Methods:
- Immunoprecipitation assays to identify cellular binding partners of MxA (human Mx protein).
- In vitro binding assays using purified recombinant MxA and Mx1 (mouse Mx protein) with UAP56 and URH49.
- Subcellular localization studies of Mx-RNA helicase complexes in infected cells.
Main Results:
- MxA was found to associate with UAP56 and URH49, two RNA helicases vital for IAV replication.
- Direct binding between MxA and UAP56/URH49 was confirmed using purified recombinant proteins.
- Recombinant mouse Mx1 also demonstrated binding to UAP56 and URH49.
- Complex formation occurred in the perinuclear region for MxA and in nuclear dots for Mx1, correlating with their known antiviral sites.
Conclusions:
- Mx proteins (human MxA and mouse Mx1) directly bind to cellular RNA helicases UAP56 and URH49.
- The subcellular localization of these Mx-RNA helicase complexes aligns with the sites of antiviral activity.
- Mx proteins likely exert antiviral activity against IAV by disrupting the function of UAP56 and URH49.
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