Porcine reproductive and respiratory syndrome virus nsp1-beta protein interacts with nucleoporin 62 (Nup62) to promote viral replication and immune evasion.

Ke, Hanzhong; Han, Mingyuan; Kim, Jineui; Gustin, Kurt E; Yoo, Dongwan

Porcine reproductive and respiratory syndrome virus (PRRSV) blocks host mRNA nuclear export to the cytoplasm, and nonstructural protein (nsp) 1-beta of PRRSV has been identified as the protein disintegrating the nuclear pore complex. In the present study, the molecular basis for the inhibition of host mRNA nuclear export was investigated. Nucleoporin 62 (Nup62) was found to bind to nsp1-beta, and the region representing the C-terminal 328-522 residues of Nup62 was determined as the binding domain to nsp1-beta. The nsp1-beta L126A mutant in the SAP domain did not bind to Nup62, and in L126A-expressing cells, the host mRNA nuclear export occurred normally. The vL126A mutant PRRSV generated by reverse genetics replicated at a slower rate, and the titer was lower than wild-type virus. In nsp1-beta overexpressing cells or siRNA-mediated Nup62 knock-down cells, the viral protein synthesis increased. Notably, the production of type I interferons (IFNs-α/β), IFN-stimulated genes (PKR, OAS, Mx1, ISG15), IFN-induced proteins with tetratricopeptide repeats (IFITs) 1 and 2, and IFN regulatory factor 3 decreased in these cells. As consequence, the growth of vL126A mutant PRRSV was rescued to the level of wild-type PRRSV. These findings are attributed to the NPC disintegration by nsp1-beta, resulting in increased viral protein production and decreased host protein production including antiviral proteins in the cytoplasm. Our study reveals a new strategy of PRRSV for immune evasion and enhanced replication during infection.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) causes PRRS and is known to effectively suppress host innate immunity. The PRRSV nsp1-beta protein blocks host mRNA nuclear export, which has been shown as one of the viral mechanisms for inhibition of antiviral protein production. The nsp1-beta binds to the cellular protein nucleoporin 62 (Nup62), and as consequence, the nuclear pore complex (NPC) is disintegrated and the nucleocytoplasmic trafficking of host mRNAs and host proteins are blocked. We show the dual benefits of Nup62 and nsp1-beta binding for PRRSV replication; the inhibition of host antiviral protein expression and the exclusive usage of host translation machinery by the virus. Our study unveils a novel strategy of PRRSV for immune evasion and enhanced replication during infection.