Fig 5.

The CoV 3CLpro inhibitor CE-5 blocks MERS-CoV 3CLpro activity. (A) MERS-CoV 3CLpro activity is inhibited by CE-5. HEK293T cells were transfected with wild-type (WT) or catalytic-mutant (CA) pMERS-pp3CLpro and pGlo-VRLQS DNA, incubated for 14 h, and then treated with 6.25, 12.5, 25, or 50 μM CE-5 or DMSO for 6 h. Cells were lysed and assayed for dual-luciferase activity. The experiment was performed in triplicate, with error bars representing the standard deviations of the means. *, P < 0.005, as determined with Student's t test between DMSO- and drug-treated cells. (B) MERS-CoV 3CLpro activity was inhibited by CE-5 in the live-cell assay. HEK293T cells were transfected with wild-type (WT) or catalytic-mutant (CA) pMERS-pp3CLpro and pGlo-VRLQS for 13 h, incubated with GloSensor reagent for 1 h, and then treated with 50 μM CE-5 or DMSO. Luciferase activity was assayed in live cells every hour using a luminometer. The experiment was performed in triplicate, with error bars representing the standard deviations of the means. *, P < 0.005, as determined with Student's t test between DMSO- and drug-treated cells.