African swine fever virus pCP312R interacts with host RPS27A to shut off host protein translation and promotes viral replication.

African swine fever virus (ASFV) severely threatens the global economy and food security. ASFV encodes >150 genes, but the functions of most of them have yet to be characterized in detail. Here we explored the function of the ASFV CP312R gene and found that CP312R plays an essential role in ASFV replication. Knockout of the CP312R gene terminated viral replication and CP312R knockdown substantially suppressed ASFV infection in vitro. Furthermore, we resolved the crystal structure of pCP312R to 2.3 Å resolution and found that pCP312R has the potential to bind nucleic acids. LC-MS analysis and co-immunoprecipitation assay revealed that pCP312R interacts with RPS27A, a component of the 40S ribosomal subunit. Confocal microscopy showed the interaction between pCP312R and RPS27A leaded to a modification in the subcellular localization of this host protein, which suppresses host protein translation. Renilla-Glo luciferase assay and Ribopuromycylation analysis evidenced that knockout of RPS27A completely aborted the shutoff activity of pCP312R, and trans-complementation of RPS27A recovered pCP312R shutoff activity in RPS27A-knockout cells. Our findings shed light on the function of ASFV CP312R gene in virus infection, which triggers inhibition of host protein synthesis.