Genome-scale CRISPR screen identifies TMEM198 driving double membrane vesicle formation in swine alphacoronavirus and murine betacoronavirus infected cells.

COVID-19 pandemic caused by the SARS-CoV-2 which is well-publicized cross-species transmissibility. SARS-CoV-2 belongs to genus Betacoronavirus, several pathogenic alphacoronaviruses have shown similar patterns of emergence. Much less attention paid to host factors required for alphacoronavirus replication compared to those of betacoronaviruses. Here, we utilized a genome-wide CRISPR-Cas9-based screen to identify TMEM198 as a critical host protein for double-membrane vesicle (DMVs) formation during the replication of swine alphacoronavirus. Gene deletion of TMEM198 led to a reduction in the levels of viral infection in cells, whereas the ectopic expression of TMEM198 correspondingly resulted in an increase in infection levels. At the mechanistic level, TMEM198 directly binds to the C-terminal of nonstructural protein 3 (nsp3c) and nonstructural protein 4 (nsp4) to participate in the formation of DMVs. The first 35 amino acids at the N-terminal of TMEM198 are critical for the formation of DMVs and viral replication. Moreover, mice with a gene deletion of TMEM198 exhibit reduced susceptibility to the Betacoronavirus MHV. These results identify the function of TMEM198 in the formation of DMVs during the replication of swine alphacoronavirus and murine betacoronavirus.