The CP312R protein of African swine fever virus inhibits host protein translation via the BiP/PERK/eIF2α pathway.

African swine fever is a highly contagious, febrile, hemorrhagic, and often fatal disease of domestic pigs and wild boar, caused by African swine fever virus (ASFV). ASFV has evolved multiple strategies to suppress host antiviral responses, including the regulation of host translation shutoff for immune evasion. However, the intricate mechanisms of translation shutoff regulated by viral proteins remain largely unexplored. A previous study has shown that pCP312R-a structural protein of ASFV with 312 amino acids (aa)-inhibits host protein translation by binding to the ribosomal protein S27A (RPS27A). Here, we demonstrated that the RNA polymerase-like domain (aa 59-163) of pCP312R was essential for inhibiting protein synthesis. However, the RNA polymerase-like domain of pCP312R did not interact with RPS27A, implying the existence of a novel inhibitory mechanism. In this study, we showed that pCP312R specifically inhibited cellular protein synthesis at the stage of translation. Notably, overexpression of pCP312R reduced the expression of heavy-chain-binding protein (BiP). Furthermore, pCP312R induced the protein translation shutoff by promoting the phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) and eukaryotic initiation factor 2α (eIF2α). Taken together, our study reveals that ASFV pCP312R inhibits cellular protein synthesis via the BiP/PERK/eIF2α pathway.