A Cytoplasmic RNA Virus Alters the Function of the Cell Splicing Protein SRSF2

Abstract

To replicate efficiently, viruses must create favorable cell conditions and overcome cell antiviral responses. We previously reported that the reovirus protein 2 from strain T1L, but not strain T3D, represses one antiviral response: alpha/beta interferon signaling. We report here that T1L, but not T3D, 2 localizes to nuclear speckles, where it forms a complex with the mRNA splicing factor SRSF2 and alters its subnuclear localization. Reovirus replicates in cytoplasmic viral factories, and there is no evidence that reovirus genomic or messenger RNAs are spliced, suggesting that T1L 2 might target splicing of cell RNAs. Indeed, RNA sequencing revealed that reovirus T1L, but not T3D, infection alters the splicing of transcripts for host genes involved in mRNA posttranscriptional modifications. Moreover, depletion of SRSF2 enhanced reovirus replication and cytopathic effect, suggesting that T1L 2 modulation of splicing benefits the virus. This provides the first report of viral antagonism of the splicing factor SRSF2 and identifies the viral protein that determines strain-specific differences in cell RNA splicing.IMPORTANCE Efficient viral replication requires that the virus create favorable cell conditions. Many viruses accomplish this by repressing specific antiviral responses. We demonstrate here that some mammalian reoviruses, RNA viruses that replicate strictly in the cytoplasm, express a protein variant that localizes to nuclear speckles, where it targets a cell mRNA splicing factor. Infection with a reovirus strain that targets this splicing factor alters splicing of cell mRNAs involved in the maturation of many other cell mRNAs. Depletion of this cell splicing factor enhances reovirus replication and cytopathic effect. Our results provide the first evidence of viral antagonism of this splicing factor and suggest that downstream consequences to the cell are global and benefit the virus.KEYWORDS RNA processing, SRSF, reovirus, splicing V iruses are obligatory intracellular pathogens that require a hospitable cell environment for their replication. However, viral infection induces cell innate responses that are antiviral. Accordingly, viruses have evolved numerous strategies to evade these responses. For example, viral infection of virtually any cell type induces a protective type I interferon (IFN-␣/␤) response, and many viruses use at least one mechanism to suppress this antiviral system (1, 2). Viral proteins that inhibit cell antiviral responses have been identified for most viruses, as have the cell proteins they target (1, 3). Not surprisingly, the most commonly identified targets are cell proteins involved in the IFN-␣/␤ response (1, 2).Mammalian reoviruses are double-stranded RNA nonenveloped viruses that replicate in membrane-associated cytoplasmic viral factories (VFs) (4, 5). Reovirus strain type 1 Lang (T1L) represses IFN-␤ signaling, while type 3 Dearing (T3D) does not (6), and this

Cellular localisation of the proteins of region 3 of feline enteric coronavirus

“…The localisation of the protein in multiple cellular compartments and the presence of predicted DNA binding and activator domains indicate pleiotropic functions of 3a that most probably involve the reprogramming of the transcriptional regulation of the infected cells. Viral proteins with similar multiple (cytosolic and nuclear) localisations were identified in several different viruses (e. g. 7ap of PRRSV, X protein of hepatitis B virus, μ2 of reovirus T1L (Mbisa et al, 2000;Henkler et al, 2001;Ma et al, 2011;Olasz et al, 2016Olasz et al, , 2017aRivera-Serrano et al, 2017) with proven nucleic acid binding and/or transcription regulating capabilities. Acta Veterinaria Hungarica 66, 2018 Protein 3b was found to localise in the mitochondrion and the nucleolus (Fig.…”

Rotavirus NSP1 localizes in the nucleus to disrupt PML nuclear bodies during infection

“…Some viruses with RNA genomes that replicate in the nucleus of infected cells have been shown to manipulate other types of nuclear bodies to enhance viral replication. There is now a growing appreciation for the manipulation of nuclear processes by cytoplasmically replicating viruses (37–40). Here we report that in addition to its known cytoplasmic localization, the rotavirus IFN antagonist protein NSP1 is also found in the nucleus of infected cells.…”

“…Other cytoplasmically replicating dsRNA viruses have also been shown to express proteins that localize to the nucleus. The reovirus μ2 protein, which interferes with the type I IFN response in a strain-specific manner (58, 59), has been shown to localize to nuclear speckles and alter host cell splicing (40). Orbiviruses including bluetongue virus (BTV) and African horse sickness virus express a nonstructural protein NS4 that has been shown to localize to the cytoplasm and nucleus of infected cells (60–62).…”

Viral modulation of cellular RNA alternative splicing: A new key player in virus–host interactions?

“…The main strength of this study is that both AS‐PCR and mass spectrometry were used to validate the results, giving additional weight to the findings. In contrast, a later study by another group showed a limited effect of the T3D virus compared to the reovirus serotype 1‐Lang strain (T1L) (Rivera‐Serrano et al, ). This apparent discrepancy is likely attributable to variations in the actual amino acid sequences of the T3D strain used in different laboratories (Sandekian & Lemay, ).…”