FIG 5.

Suppression of IBV-induced cFOS upregulation and increased induction of apoptosis in ERK1/2 knockdown cells infected with IBV. (a) H1299 cells were transfected with siEGFP and siERK1/2 before being infected with IBV at an MOI of ∼2. Cell lysates were harvested at the indicated time points and subjected to Western blot analysis using PARP, ERK1/2, cFOS, cJUN, and IBV N antibodies. Beta-tubulin was included as the loading control. Sizes of protein ladders in kilodaltons are indicated on the left. Significance levels are presented by the P value (**, P < 0.01; ***, P < 0.001; ****, P < 0.0001). (b) H1299 cells were transfected and infected as described above for panel a. Cell lysates were harvested at the indicated time points for RNA extraction. Equal amounts of total RNA were reverse transcribed, and the mRNA levels of ERK1/2, cFOS, and cJUN were determined by qPCR. The IBV gRNA levels were determined as an indicator of IBV replication efficiency. Significance levels are presented by the P value (*, P < 0.05; ***, P < 0.001). M, mock.