Avian Double RNA Virus Protein VP2 Inhibits DsRNA Degradation

Suppressing the host's innate immunity is an important part of the animal's virus replication cycle,because its efficiency determines not only whether the virus will begin to replicate,but also the level of viral components and the accumulation of progeny virus particles in the cell.RNA silencing is a eukaryotic surveillance mechanism that detects and eliminates double-stranded RNA(dsRNA)to protect against invasive nucleic acids such as viruses,transposons and transgenes.Infectious bursal disease virus belongs to the avian double-stranded RNA virus of the double-stranded RNA virus family,which releases its genome during the replication process of the virus-infected host cell,but the genome is not degraded in the cell,and then successfully assembled to form a mature Virus particles,which indicates that there are certain factors in the process of virus replication that can inhibit the degradation of the genome and promote the replication and proliferation of the virus.This study found that the avian double-RNA virus protein VP2 can inhibit genome degradation.After preliminary screening of VP2 in host cells to inhibit dsRNA degradation,we continued to construct a cell line that overexpressed the viral protein VP2 for verification.At the same time,after purifying VP2 protein in vitro,it was found that it can inhibit the cleavage effect of cleavage protein Dicer on dsRNA in the RNA interference pathway.The results of in vitro and in vivo experiments show that VP2 acts as a protective factor to inhibit the degradation of the genome during virus replication.Since VP2 can inhibit the degradation of dsRNA,does it also have RNA binding ability?So we explored the binding ability of VP2 to dsRNA.The results of intracellular co-immunoprecipitation experiments show that in the case of viral infection and eukaryotic expression of VP2 protein,they can bind to dsRNA and are independent of other proteins.Pull down experiments showed that VP2 can directly bind to dsRNA.The above evidence shows that the avian double RNA virus protein VP2 is an RNA binding protein.In order to verify whether the binding of VP2 protein to dsRNA is specific,the binding region of VP2 to dsRNA was further identified.The results of co-immunoprecipitation experiments show that the binding of VP2 to dsRNA is mainly in the non-coding region of the genome,and the double-stranded RNA binding ability of VP2 is nucleic acid sequence dependent.Finally,by comparing the VP2 protein's inhibitory effect on the degradation of dsRNA of different gene sequences,it is shown that the non-coding region of the genome is essential for VP2 to inhibit the degradation of double-stranded RNA.In this paper,we found for the first time that VP2 of avian double-stranded RNA virus is a dsRNA binding protein,which can inhibit dsRNA degradation and promote virus replication during virus replication.As an important antiviral mechanism in cells,enhancing the activity of the RNAi pathway or the "protective factor" that directly targets dsRNA may be an effective way to develop new antiviral drugs.