Abstract
The two N-terminal cleavage products, nsp1α and nsp1β, of the replicase polyproteins of porcine reproductive and respiratory syndrome virus (PRRSV) each contain a papain-like autoproteinase domain, which have been named PCPα and PCPβ, respectively. To assess their role in the PRRSV life cycle, substitutions and deletions of the presumed catalytic cysteine and histidine residues of PCPα and PCPβ were introduced into a PRRSV infectious cDNA clone. Mutations that inactivated PCPα activity completely blocked subgenomic mRNA synthesis, but did not affect genome replication. In contrast, mutants in which PCPβ activity was blocked proved to be non-viable and no sign of viral RNA synthesis could be detected, indicating that the correct processing of the nsp1β/nsp2 cleavage site is essential for PRRSV genome replication. In conclusion, the data presented here show that a productive PRRSV life cycle depends on the correct processing of both the nsp1α/nsp1β and nsp1β/nsp2 junctions.
†Present address: Genmab, PO Box 85199, 3508 AD Utrecht, The Netherlands.
‡Present address: Wageningen UR, Central Institute for Animal Disease Control Lelystad, CIDC-Lelystad, PO Box 2004, 8203 AA Lelystad, The Netherlands.
Present address: Amsterdam Molecular Therapeutics, PO Box 22506, 1100 DA Amsterdam, The Netherlands.