The mengovirus leader protein blocks interferon-α/β gene transcription and inhibits activation of interferon regulatory factor 3

Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands.
Cellular Microbiology (Impact Factor: 4.82). 01/2008; 9(12):2921-30. DOI: 10.1111/j.1462-5822.2007.01006.x
Source: PubMed

ABSTRACT Viral infection of mammalian cells triggers the synthesis and secretion of type I interferons (i.e. IFN-alpha/beta), which induce the transcription of genes that cause cells to adopt an antiviral state. Many viruses have adapted mechanisms to evade IFN-alpha/beta-mediated responses. The leader protein of mengovirus, a picornavirus, has been implicated as an IFN-alpha/beta antagonist. Here, we show that the leader inhibits the transcription of IFN-alpha/beta and that both the presence of a zinc finger motif in its N-terminus and phosphorylation of threonine-47 are required for this function. Transcription of IFN-alpha/beta genes relies on the activity of a number of transcription factors, including interferon regulatory factor 3 (IRF-3). We show that the leader interferes with the transactivation activity of IRF-3 by interfering with its dimerization. Accordingly, mutant viruses with a disturbed leader function were impaired in their ability to suppress IFN-alpha/beta transcription in vivo. By consequence, the leader mutant viruses had an impaired ability to replicate and spread in normal mice but not in IFNAR-KO mice, which are incapable of mounting an IFN-alpha/beta-dependent antiviral response. These results suggest that the leader, by suppressing IRF3-mediated IFN-alpha/beta production, plays an important role in replication and dissemination of mengovirus in its host.

Download full-text


Available from: Kjerstin H W Lanke, Jun 11, 2015
  • Source
    • "Upon infection with WT EMCV, induction of Ifit1 and Ifnb1 was limited (Figure 6A,B). It was markedly greater in response to infection with EMCV Zn C19AC22A , which encodes the non-functional mutant L protein (Figure 6A,B), consistent with the fact that the L protein inhibits IFN induction (Hato et al., 2007). In contrast, infection with EMCVΔL lacking both L protein and EMCV L region RNA induced lower levels of Ifnb1 or Ifit1 than infection with EMCV Zn C19AC22A at two different multiplicities of infection (MOI) (Figure 6A,B). "
    [Show abstract] [Hide abstract]
    ABSTRACT: eLife digest A virus is basically molecules of DNA or RNA inside a protein shell, and in order to reproduce, it must infect a living cell and take control of it. However, the attacked cell will fight back and try to eliminate the invader. Activation of this so-called innate immune response requires the host cells to recognize that they have been infected, which they do by detecting the tell-tale molecules that indicate the presence of the virus. When an RNA virus infects a cell, the tell-tale molecules are often atypical RNA molecules carried by the virus or produced as the virus replicates. Recognition of this ‘foreign’ material by receptor proteins inside the cell triggers the production of molecules called interferons, which activate the innate defence systems that eliminate the virus. Different receptor proteins recognize different RNA viruses. For example, a receptor called MDA5 is known to respond to the picornaviruses, some of which can cause inflammation of the brain and heart muscle. However, the identities of the specific RNA molecules that are recognized by the MDA5 receptor have not been known. Deddouche et al. have now identified one such RNA molecule with the help of a second receptor protein, called LGP2. The LGP2 receptor is not able to give the signal to produce interferons, so it is thought to work by binding to the RNA molecule to form a complex that is then relayed to MDA5 to give this signal. By isolating the complexes of LGP2 receptor from picornavirus-infected cells and sequencing the associated RNA, it was possible to identify the mystery RNA trigger. Deddouche et al. then tested picornaviruses in which this piece of RNA had been deleted from the genome, and found that the mutant viruses triggered a much weaker interferon response. By providing insight into the ways that some viruses are detected by the innate immune system, this research may inform future work on the development of new treatments to control viral infection. DOI:
    eLife Sciences 02/2014; 3:e01535. DOI:10.7554/eLife.01535 · 8.52 Impact Factor
  • Source
    • "Figure 1A shows IFN-b responses in WT and knockout MEFs triggered by transfection of vRNA of WT mengovirus (a strain of EMCV) or infection of a mutant mengovirus (mengo-Zn). This virus generates high levels of IFN-b because its IFN antagonist has been compromised (Hato et al., 2007). Both methods resulted in a MDA5- and MAVS-dependent, but RIG-I-independent, IFN-b induction, demonstrating the suitability of the transfection method to identify the RLR(s) responsible for detecting picornaviruses. "
    [Show abstract] [Hide abstract]
    ABSTRACT: RIG-I and MDA5 are cytosolic RNA sensors that play a critical role in innate antiviral responses. Major advances have been made in identifying RIG-I ligands, but our knowledge of the ligands for MDA5 remains restricted to data from transfection experiments mostly using poly(I:C), a synthetic dsRNA mimic. Here, we dissected the IFN-α/β-stimulatory activity of different viral RNA species produced during picornavirus infection, both by RNA transfection and in infected cells in which specific steps of viral RNA replication were inhibited. Our results show that the incoming genomic plus-strand RNA does not activate MDA5, but minus-strand RNA synthesis and production of the 7.5 kbp replicative form trigger a strong IFN-α/β response. IFN-α/β production does not rely on plus-strand RNA synthesis and thus generation of the partially double-stranded replicative intermediate. This study reports MDA5 activation by a natural RNA ligand under physiological conditions.
    Cell Reports 11/2012; 2(5). DOI:10.1016/j.celrep.2012.10.005 · 7.21 Impact Factor
  • Source
    • "RNA was treated with DNase I prior to reverse transcription and amplification by PCR. Primer sequences have been described (Hato et al., 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Picornaviruses encompass a large family of RNA viruses. Some picornaviruses possess a leader (L) protein at the N-terminus of their polyprotein. The L proteins of encephalomyocarditis virus, a cardiovirus, and foot-and-mouth disease virus (FMDV), an aphthovirus, are both dispensable for replication and their major function seems to be the suppression of antiviral host cell responses. Previously, we showed that the L protein of mengovirus, a strain of encephalomyocarditis virus, inhibits antiviral responses by inhibiting type I interferon (IFN-alpha/beta) gene transcription. The L protein of the FMDV is a protease (L(pro)) that cleaves cellular factors to reduce cytokine and chemokine mRNA production and to inhibit cap-dependent cellular host mRNA translation, thereby limiting the production of proteins with antiviral activity. In this study, we constructed a viable chimeric mengovirus that expresses FMDV L(pro) in place of the authentic L protein in order to compare the efficiency of the immune evasion mechanisms mediated by L and L(pro) respectively. We show that in this mengovirus background the L protein is more potent than FMDV L(pro) in suppressing IFN-alpha/beta responses. Yet, FMDV L(pro) is important to antagonize infection-limiting responses both in vitro and in vivo.
    Cellular Microbiology 10/2009; 12(3):310-7. DOI:10.1111/j.1462-5822.2009.01395.x · 4.82 Impact Factor
Show more