Transient-replicon analysis of WT NS5B and C-terminal domain mutants. Huh-7 cells were transfected with 10 μg replicon RNA by electroporation. After 4, 24, 48, 72, and 96 h, cells were lysed, and luciferase activities were determined. Values are corrected for transfection efficiency, as determined by measuring the luciferase activity 4 h after transfection.