Abstract
ABSTRACTDuring viral infection, the dynamic virus-host relationship is constantly in play. Many cellular proteins, such as RNA-binding proteins (RBPs), have been shown to mediate antiviral responses during viral infection. Here, we report that the RBP FUS/TLS (fused in sarcoma/translocated in liposarcoma) acts as a host-restricting factor against infection with coxsackievirus B3 (CVB3). Mechanistically, we found that deletion of FUS leads to increased viral RNA transcription and enhanced internal ribosome entry site (IRES)-driven translation, with no apparent impact on viral RNA stability. We further demonstrated that FUS physically interacts with the viral genome, which may contribute to direct inhibition of viral RNA transcription/translation. Moreover, we identified a novel function for FUS in regulating host innate immune response. We show that in the absence of FUS, gene expression of type I interferons and proinflammatory cytokines elicited by viral or bacterial infection is significantly impaired. Emerging evidence suggests a role for stress granules (SGs) in antiviral innate immunity. We further reveal that knockout of FUS abolishes the ability to form SGs upon CVB3 infection or poly(I·C) treatment. Finally, we show that, to avoid FUS-mediated antiviral response and innate immunity, CVB3 infection results in cytoplasmic mislocalization and cleavage of FUS through the enzymatic activity of viral proteases. Together, our findings in this study identify FUS as a novel host antiviral factor which restricts CVB3 replication through direct inhibition of viral RNA transcription and protein translation and through regulation of host antiviral innate immunity.IMPORTANCE Enteroviruses are common human pathogens, including those that cause myocarditis (coxsackievirus B3 [CVB3]), poliomyelitis (poliovirus), and hand, foot, and mouth disease (enterovirus 71). Understanding the virus-host interaction is crucial for developing means of treating and preventing diseases caused by these pathogens. In this study, we explored the interplay between the host RNA-binding protein FUS/TLS and CVB3 and found that FUS/TLS restricts CVB3 replication through direct inhibition of viral RNA transcription/translation and through regulation of cellular antiviral innate immunity. To impede the antiviral role of FUS, CVB3 targets FUS for mislocalization and cleavage. Findings from this study provide novel insights into interactions between CVB3 and FUS, which may lead to novel therapeutic interventions against enterovirus-induced diseases.
Highlights
During viral infection, the dynamic virus-host relationship is constantly in play
TAR DNA-binding protein 43 (TDP-43) and ARE/poly(U)-binding/degradation factor 1 (AUF1/hnRNP D) have both been shown to play an antiviral role against various enteroviruses, and to overcome this effect, viruses have adopted different strategies to disrupt the function of these RNA-binding proteins (RBPs) [3,4,5,6,7,8]
We found that after infection with coxsackievirus B3 (CVB3), a neurotrophic virus, FUS was mislocalized from its normal nuclear location to the cytoplasm starting at 3 h postinfection in HeLa cells, NSC-34 cells, and SH-SY5Y cells (Fig. 1A and B)
Summary
The dynamic virus-host relationship is constantly in play. Many cellular proteins, such as RNA-binding proteins (RBPs), have been shown to mediate antiviral responses during viral infection. We explored the interplay between the host RNA-binding protein FUS/TLS and CVB3 and found that FUS/TLS restricts CVB3 replication through direct inhibition of viral RNA transcription/translation and through regulation of cellular antiviral innate immunity. TAR DNA-binding protein 43 (TDP-43) and ARE/poly(U)-binding/degradation factor 1 (AUF1/hnRNP D) have both been shown to play an antiviral role against various enteroviruses, and to overcome this effect, viruses have adopted different strategies to disrupt the function of these RBPs [3,4,5,6,7,8] Another functionally and structurally relevant RBP is FUS/TLS (fused in sarcoma/translocated in liposarcoma); the role of FUS in viral infection and the interplay between FUS and enteroviruses have not been explored [9]. FUS has been linked to many important cellular functions, such as transcription, RNA splicing, translation, and DNA repair [10,11,12]
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