PSMB4 and infection: We then silenced each of the top four upregulated PSMBs (PSMB1, PSMB4, PSMB8 and PSMB9, fold change >1.5) using shRNA in HEK293T cells and examined the viral replication in PSMB-silenced cells after VSV-expressing GFP (VSV-GFP) infection.