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. 2016 Mar 14;113(13):3609–3614. doi: 10.1073/pnas.1523686113

Fig. 4.

Fig. 4.

SPR inhibits virus production at a lytic replicative stage after DNA replication. (A) Antiviral effect of SPR is not due to inhibition of viral DNA replication. EBV-positive AGS gastric carcinoma cells were transduced with a lentivirus expressing EBV transactivator ZTA protein under control of a doxycycline-inducible promoter to generate a cell line in which EBV replicates robustly when treated with doxycycline (AGSiZ). The AGSiZ cell line was either mock treated (–) or treated (+) with doxycycline to induce lytic DNA replication (ind.) and also treated with SPR or EPR at concentrations shown. DNA copy number was measured by qPCR of cell pellets 70 h postinduction. RQ, relative quantity of intracellular viral DNA. (B) SPR but not EPR specifically inhibits infectious virus production. Serial dilutions of virus-containing supernatant were used to infect 293 cells, and the number of GFP-positive cells representing infectious viral particles was measured by flow cytometry. (C) SPR does not affect expression of IE or E EBV proteins. Protein cell lysates from cells treated with SPR (S) or EPR (E) were immunoblotted using anti-SM, EA-D, RTA, ZTA, or actin antibodies at 24 and 48 h after induction of replication. (D) SPR but not EPR inhibits production of extracellular EBV. Extracellular EBV DNA was measured by DNA qPCR in cell supernatants harvested 5 d after SPR (S) or EPR (E) treatment. RQ, relative quantity of DNA.