Synergistic pro-apoptotic effects of both knockdown of IFIT3 and DV infection.
A549 cells transfected with control siRNA (si-Ctl) or IFIT3 siRNA (siIFIT3) for 24 h were infected with mock or DV at M.O.I. = 0.5 or 5 for an additional 48 h. Cell viability was determined by MTT assays. Mock-infected cells treated with control siRNA transfection were taken as 100%, and OD values from individual conditions were normalized by the value of the control (% of control; A). DNA content was determined by sub-G1 analysis (left panel in B), and the synergistic effects were calculated (right panel in B). Determination and visualization of cell apoptosis were also performed by TUNEL assays using flow cytometry and immunofluorescent staining (C). Data show representative results and analysis pooled from at least 3 independent experiments. The analysis was performed by ANOVA as described in Materials and Methods. *P < 0.05, **P < 0.01, ***P < 0.001. Ctl stands for control.