Dissecting The Role Of Porcine Reproductive And Respiratory Syndrome Virus Internal Region Of Nucleocapsid Protein In Virus Replication

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a singlestrand positive sense RNA virus. The PRRSV genome is about15kb in length, andthe coding region is flanked by untranslated regions (UTRs) at each end (the5′and3′UTR, respectively). The genome contains at least ten open reading frames (ORFs),ORF1a,ORF1b,ORF2a,ORF2b,ORF3,ORF4,ORF5,ORF5a,ORF6,ORF7. N protein, encoded by ORF7, is the most abundant component of the virionand plays acrucial role in virus assembly. In previous study, in N-and C-terminaldeletion mutation virus we found second site mutation in the internal region in Nprotein, and the internal deletion without the original C-terminal deletion weredispensable for type2PRRSV viability. In order to define the non-essential domain ofthe interal part of N protein, we further deletion mutation amino acid at the basic ofprovious study. In this study, serial internal trun cations of N protein were per-formedin the context of type2PRRSV infectious cDNA clone, and our results revealed that astretch of inter-genotypic variable N internal residues aa37-45and aa45-52weredispensable for type2PRRSV infectivity. Immunofluorescence assay and RT-PCRanalysis indicated that the conserved53aa in N protein internal region is essential forvirus replication.PRRSV replicates in the cytoplasm, during infection, the N protein is specificallylocalized to the nucleus and nucleolus in addition to its normal cytoplasmicdistribution. There were 'pat4' and 'pat7' motif in N protein named NLS-1and NLS-2(KKNKK) respectively. Previous study demonstrated that N protein nuclearlocalization is indeed associated with viral pathogenesis and host response to PRRS.Our internal deletion mutation virus around NLS-2are effected its nuclearlocalization, the rescued viruses could be the candidates for marker vaccine.