The Antiviral Activity And Mechanisms Of RNA-binding Protein RBM47

Viruses,the highly parasitic tiny particles without intact cell structures,exist widely in nature.Viruses must utilize the host energy metabolism system and protein translation machinery to support their replication.They also evolved a series of strategies to evade the host immune responses.During the long term combating with the viruses,host developed the highly complicated and precise immune system to clear the invaded pathogens efficiently.In previous RNA-seq screening,we identified that the expression of RBM47 is upregulated in Dengue virus infected cells.Further study suggested that RBM47 can be induced in various kinds of cells upon infection with different viruses or stimulation of interferons(IFNs).RBM47 contains two RNA binding motifs which bind specifically to RNAs but not single strand DNA.Recent studies suggest that RBM47 is the key regulator of the post transcriptional modulation during the embryo development and tumorigenesis.The roles of RBM47 during virus infection remain unclear.In this study,we found that overexpression of RBM47 significantly suppressed the infection of RNA viruses such as VSV,DENV,ZIKV and H1N1,as well as DNA virus HSV-1.On the contrary,if RBM47 is silenced by RNAi,the viral replications were significantly increased.These data suggests that RBM47 displays antiviral activities inside the cells.Next,we obtained the RBM47-KO heterozygous mice,and infected them with VSV or HSV-1.The RBM47-KO heterozygous mice were more susceptible to VSV and HSV-1 infection when compared with wide type controls.This suggests that RBM47 has antiviral activity in vivo.By using the dual luciferase reporter gene assay,we found that RBM47 has no obvious impact on interferon production in cells,but significantly activates the IFN stimulated element ISRE and enhances the expression of interferon stimulated genes(ISGs).The RNA-protein coprecipitation and RNA-seq results suggested that RBM47 specifically binds to the 3'UTR of IFNAR1 mRNA,and increases its stability.This further enhanced the antiviral efficiency of type one IFNs and stimulated the expressions of ISGs.To analyze the proteins that interact with RBM47,the co-immunoprecipitation followed by protein mass spectrometry(IP-MS)were performed and PCBP2 was identified to interact with RBM47 specifically.PCBP2 is also reported as an RNA binding protein that stabilizes the mRNAs of STAT1 and STAT2 and stimulates ISG expression.By RIP and qPCR analysis,we found that RBM47 and PCBP2 synergistically stabilize the mRNA of IFNAR1,thus stimulate the expressions of ISGs and enhance the host antiviral responses.In summary,this study suggests that RNA binding protein RBM47 plays an important role in enhancing host IFN downstream signaling pathway.This is also the first time to report a role of distinct member from RBM family in antiviral innate immunity.This study also provides a novel target for the development of antiviral drugs.