Abstract
Previous studies have shown that DEAD (Asp-Glu-Ala-Asp)-box RNA helicases play important roles in viral infection, either as cytosolic sensors of pathogenic molecules or as essential host factors against viral infection. In the current study, we found that DDX6, an RNA helicase belonging to the DEAD-box family of helicase, exhibited anti-Enterovirus 71 activity through augmenting RIG-I-mediated type-I IFN response. Moreover, DDX6 binds viral RNA to form an RNA-protein complex to positively regulate the RIG-I-mediated interferon response; however, EV71 has evolved a strategy to antagonize the antiviral effect of DDX6 by proteolytic degradation of the molecule through its non-structural protein 2A, a virus-encoded protease.
Highlights
Enterovirus 71 (EV71) is a positive-stranded RNA virus that contains a single open reading frame and is non-encapsulated (Wang and Li, 2019)
To determine whether DDX6 protein was affected by EV71, lysates from EV71 infected-HeLa or HT-29 cells were analyzed by western blot, respectively, and the results indicated that EV71 infection reduced DDX6 protein expression by about 40% as compared with that in the uninfected cells (Figures 1A, B)
We found that EV71 replication substantially increased when endogenous DDX6 was knockdown in HeLa cells (Figure 2)
Summary
Enterovirus 71 (EV71) is a positive-stranded RNA virus that contains a single open reading frame and is non-encapsulated (Wang and Li, 2019). Interferons are important to antiviral therapy as the first line of the host immune response to viruses. Because of the important role of RIG-I signaling in the antiviral immune responses, it is crucial to investigate the function of proteins regulating RIG-I. It is supported that DDX6 has pro- and antiviral roles in viral infections. DDX6 modulates replication and the stability of HCV RNA through interaction with miR-122 and the viral-5′ UTR (Biegel et al, 2017). Bunyaviruses snatch mRNA caps from P-body component DDX6, promoting the decapping of host mRNAs and decreasing the capped RNAs in P bodies to reduce virus infection (Hopkins et al, 2013). Ward et al have demonstrated that DDX6 and other SG components bind dengue virus 3’ UTR RNA to facilitate virus replication (Ward et al, 2011). Given the important roles of DDX6 in viral infection, we investigated the role of DDX6 in EV71 infection
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