Phosphorylation Modification Mechanism Of IBDV Polymerase

Infectious bursal disease(IBD)is an extremely contagious immunosuppressive disease in 3-6-week-old chickens caused by infectious bursal virus(IBDV).IBD often poses a major hazard to the poultry industry.The IBDV rescue system based on the characteristics of IBDV genome and the principle of reverse genetics has become an important tool for virological research.In this study,The IBDV bidirectional promoter virus rescue system was established by using the combination of RNA polymerase type I and RNA polymerase type II promoters.The method of cotransformation of p CMV-m A and p CMV-m B double plasmids is adopted to obtain IBDV with high efficiency.Based on this,a method for evaluating the activity of VP1 polymerase was established,which provides a tool for further study of the biological function of VP1.IBDV VP1 protein called RNA-dependent RNA polymerase(Rd Rp),which are essential for viral RNA transcription,genome replication and viral multiplication.The post-translational modification of VP1 is very important for virus proliferation,but little information is available regarding the exact mechanism of phosphorylation of IBDV VP1 and its significance in the viral life cycle.We show that the CDK1-Cyclin B1 specifically interacts with VP1 and phosphorylates VP1.Additionally,IBDV infection drives the cytoplas-mic accumulation of CDK1-Cyclin B1,which co-localizes with VP1,supporting the kinase activity of CDK1-Cyclin B1.Mass spectrometric analysis showed that serine 7(Ser7)of VP1 is the phosphorylation site mediated by CDK1-Cyclin B1.Treatment with CDK1 inhibitor RO3306 and knockdown of CDK1-Cyclin B1 severely disrupts the polymerase activity of VP1,resulting in diminished viral replication.Moreover,the replication of S7 A mutant recombinant IBDV was signifi-cantly decreased compared to that of wild-type(WT)IBDV.In this study,a new IBDV virus rescue method and VP1 polymerase activity evaluation system were established,and It was systematically proved that CDK1-Cyclin B1 complex promotes IBDV replication by phosphorylating the seventh serine at the end of VP1 N.