Molecular chaperone Jiv promotes the RNA replication of classical swine fever virus

The nonstructural protein 2 (NS2) of classical swine fever virus (CSFV) is a self-splicing ribozyme wherein the precursor protein NS2-3 is cleaved, and the cleavage efficiency of NS2-3 is crucial to the replication of viral RNA. However, the proteolytic activity of NS2 autoprotease may be achieved through a cellular chaperone called J-domain protein interacting with viral protein (Jiv) or its fragment Jiv90, as evidence suggests that Jiv is required for the proper functioning of the NS2 protein of bovine viral diarrhea virus. Hence, the expression of Jiv may be correlated with the replication efficiency of CSFV RNA. We investigated the expression levels of Jiv and viral RNA in CSFV-infected cells and tissues using Real-time RT-PCR or Western blot analysis. The obtained results show that Jiv90 possibly plays an important role in the lifecycle of CSFV because the distribution of Jiv90 protein shows a positive correlation with the viral load of CSFV. Furthermore, the overexpression or knockdown of Jiv90 in swine cells can also significantly promote or decrease the viral load, respectively. The detection of Flow cytometry shows that the overexpression of Jiv90 prolongs the G1 phase of cell cycles but has no effect on apoptosis. These findings are likely to be of benefit in clarifying the pathogenesis of the CSFV.