Suppression of TRIM19 by arterivirus nonstructural protein 1 promotes viral replication.

Tripartite motif (TRIM)-containing proteins are a family of regulatory proteins that can participate in the induction of antiviral cytokines and antagonize viral replication. Promyelocytic leukemia (PML) protein is known as TRIM19 and is a major scaffold protein organizing the PML nuclear bodies (NBs). PML NBs are membrane-less organelles in the nucleus and play a diverse role in maintaining cellular homeostasis including antiviral response. Porcine reproductive and respiratory syndrome virus (PRRSV), a member virus of the family Arteriviridae, inhibits type I interferon (IFN) response during infection, and nonstructural protein 1 (nsp1) of the virus has been identified as a potent IFN antagonist. We report that the numbers of PML NBs per nucleus were significantly downregulated during infection of PRRSV. The overexpression of all six isoforms of PML suppressed the PRRSV replication, and conversely, the silencing of PML gene expression enhanced the PRRSV replication. The suppression of PML NBs by the nsp1 protein was common in other member viruses of the family, represented by equine arteritis virus, lactate dehydrogenase elevating virus of mice, and simian hemorrhagic fever virus. Our study unveils a conserved viral strategy in arteriviruses for innate immune evasion.