Protein expression in induced PK knockout and revertant cell lines. (A) Viral reactivation in PK/KO and revertant cell lines was induced with EBV BZLF1 for 48 h. Total lysates were immunoblotted with antibodies against BGLF4, RR1, and BMRF1. The faint bands in the BGLF4 panel are likely nonspecific. (B) Cell viability assays of 293 EBV WT cells. Cells were treated with indicated amounts of MBV for 48 h, and viable cells were counted. Results indicate no loss in viability with MBV concentrations less than 80 μM. (C) Immunofluorescence staining of induced PK knockout and revertant cell lines. Cell lines containing green fluorescent protein (GFP)-labeled EBV genome are shown in green. BMRF1 staining is visualized in red. BMRF1 is not detected in uninduced samples, but efficient induction, reflected by BMRF1 expression, is observed at 48 h postinduction and is unaffected by MBV.