Rivera-Serrano Efraín E, Fritch Ethan J, Scholl Elizabeth H, Sherry Barbara
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
Comparative Medicine Institute, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
J Virol. 2017 Mar 13;91(7). doi: 10.1128/JVI.02488-16. Print 2017 Apr 1.
To replicate efficiently, viruses must create favorable cell conditions and overcome cell antiviral responses. We previously reported that the reovirus protein μ2 from strain T1L, but not strain T3D, represses one antiviral response: alpha/beta interferon signaling. We report here that T1L, but not T3D, μ2 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 μ2 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 μ2 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. 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.
为了高效复制，病毒必须创造有利的细胞条件并克服细胞的抗病毒反应。我们之前报道过，来自T1L株的呼肠孤病毒蛋白μ2，而非T3D株的该蛋白，可抑制一种抗病毒反应：α/β干扰素信号传导。我们在此报告，T1L株而非T3D株的μ2定位于核斑点，在那里它与mRNA剪接因子SRSF2形成复合物并改变其亚核定位。呼肠孤病毒在细胞质中的病毒工厂中复制，且没有证据表明呼肠孤病毒基因组或信使RNA会被剪接，这表明T1L株的μ2可能靶向细胞RNA的剪接。事实上，RNA测序显示，呼肠孤病毒T1L株而非T3D株的感染会改变参与mRNA转录后修饰的宿主基因转录本的剪接。此外，SRSF2的缺失增强了呼肠孤病毒的复制和细胞病变效应，这表明T1L株μ2对剪接的调节有利于病毒。这是关于病毒对剪接因子SRSF2的拮抗作用的首次报道，并鉴定出了决定细胞RNA剪接中菌株特异性差异的病毒蛋白。高效的病毒复制要求病毒创造有利的细胞条件。许多病毒通过抑制特定的抗病毒反应来实现这一点。我们在此证明，一些严格在细胞质中复制的哺乳动物呼肠孤病毒会表达一种定位于核斑点的蛋白变体，在那里它靶向一种细胞mRNA剪接因子。感染靶向这种剪接因子的呼肠孤病毒株会改变参与许多其他细胞mRNA成熟的细胞mRNA的剪接。这种细胞剪接因子的缺失增强了呼肠孤病毒的复制和细胞病变效应。我们的结果提供了病毒对这种剪接因子拮抗作用的首个证据，并表明对细胞的下游影响是全局性的且有利于病毒。
