Interaction With Staufen1,a Host Cell RNA-binding Protein,Regulates Infectious Bursal Disease Virus Replication By Viral Genomic DsRNA

Infectious bursal disease virus(IBDV)is an Avibirnavirus belonging to the Birnaviridae family.IBDV is the causative agent of infectious bursal disease,which is an acute and highly contagious disease of young chickens manifested by inflammation and subsequent atrophy of the bursa of fabricius and immunosuppression.Host cell protein Staufen1(Stau1),a member of RNA-binding proteins(RBPs),plays a central role in the regulation of mRNA transport,translational control,and decay.In addition to its conserved role as an RNA regulator,Stau1 is also involved in regulation of the life cycles of many RNA viruses.This study has investigated whether the host RNA regulator Stau1 can also bind to the non-self viral genome dsRNA of IBDV and whether this contributes to the regulation of IBDV productive infection,and dissected the molecular mechanisms underlying the regulation.In order to study the relationship between the chicken Stau1 and the IBDV genomic dsRNA,in this study,we firstly cloned the chicken Stau1(chStau1)and constructed the eukaryotic expression vector and related prokaryotic expression vector.Firstly the IBDV dsRNA pull-down assay,gel shift assay and mass spectrometry analysis were performed to investigate the interaction of Stau1 with the IBDV genomic dsRNA and to map the region in Stau1 responsible for the dsRNA binding.Then the indirect immunofluorescence was conducted to examine the co-localization between the IBDV dsRNA and chStau1.In order to study the effect of Stau1 on the IBDV replication,we performed the RNA interference,the plaque assay and RT-PCR analysis.The dsRNA pull-down assays were carried out to assess the reciprocal effect of Stau1,MDA5 and VP3 on their dsRNA binding.The dual-luciferase assay was performed to analyze the effect of Stau1 on the IBDV dsRNA induced IFN-? production.Result:(1)the host Stau1 co-localizes with and directly interacts with the genomic dsRNA of IBDV in vivo and in vitro and the region responsible for IBDV dsRNA binding was mapped to the N-terminal moiety of Stau1(amino acids 1-468);(2)Down-regulation of Stau1 impairs and overexpression of Stau1 promotes the IBDV replication;(3)The Stau1 down-regulation selectively targets IFN-? rather than IFN-? induction responsive to IBDV dsRNA stimulation;(4)The Stau1 suppresses the IFN-? induction responsive to IBDV infection by recognition of the viral genomic dsRNA;(5)The host Stau1 synergizes with VP3 while competes with MDA5 for the viral dsRNA binding to down-regulate the IBDV-mediated induction of IFN-?.Conclusion: In summary,this study provides the first demonstration that the chicken Stau1 interacts with IBDV dsRNA and Stau1 is a positive factor for IBDV replication.The underlying mechanism is Stau1 synergizes with VP3 while competes with MDA5 for the dsRNA binding to inhibit the IBDV-mediated induction of IFN-?.These findings contribute to a further understanding of pathogenesis and immunological mechanism of IBDV and provide a new method for the prevention and control of IBD.