FIG. 5.

Effects of emetine and actinomycin D posttreatments on the dsRNA-induced phosphorylation of SEK/MKK4, JNK, and p38 MAPK in RNase L^+/+ PKR^+/+, RNase L^−/− PKR^+/+, and RNase L^−/− PKR^−/− cells determined by immunoblot analyses. The cells were grown and treated with pI · pC for 4 h as for Fig. 4A. Where indicated, emetine (E; 100 μg/ml) or actinomycin D (AD; 25 μg/ml) was added either 1 h after (emetine) or 15 min after (actinomycin D) the treatment with pI · pC. Note the lack of effect of both emetine and actinomycin D on dsRNA-induced phosphorylation of p38 MAPK. The mechanism of actinomycin D-induced p38 MAPK phosphorylation in RNase L^−/− PKR^−/− cells (B, bottom panel, lane 2) is unknown. LF, lipofectin.