Contribution of signal transduction pathways to cell viability during exposure of Raji cells to EBV lytic cycle activators. (A) Cells were pretreated for 15 min with the specific inhibitors of p38 (SB), ERK (PD), JNK (SP), PI3K (W) or NFkB (Bay) and then exposed to P(BU)2, sodium butyrate and TGFβ as described in the Methods. After 48 hours, cells were fixed and PI stained for cytofluorymetric determination of sub-G1 events; (B) cells were incubated with P(BU)2, sodium butyrate and TGFβ. At the indicated times (hours), cell lysates were prepared and the phosphorylation pattern of p38, ERK and JNK evaluated by Western blot analysis with the specific antibodies for each protein and its phosphorylated (P-) form; (C) cells were treated as in B. At the indicated times, cell extracts were incubated with a consensus NFkB binding site oligonucleotide (oligo) to evaluate NFkB activity by EMSA (see Methods).