FIG. 4.

Disappearance of intact eIF4GI during cell death. (A) SKW B-lymphoma cells were treated with anti-Fas agonistic antibodies for 0, 2, and 5 h. The fate of eIF4GI was assessed by Western blotting (WB) with polyclonal antibodies generated against eIF4GI N terminus (left panel) or C terminus (two right panels). The position of full-length eIF4GI is indicated by an arrow. Bands exclusively recognized by either anti-eIF4G antibody in the Fas-treated cells are marked by their approximated molecular sizes (in kilodaltons) (p110, p76, p50, and p40). The asterisks mark nonspecific bands lightened by the anti-eIF4GI antibodies. (B) SKW B-lymphoma cells, either nontreated or pretreated for 2 h with CHX or with anti-Fas agonistic antibodies, were incubated in methionine-free medium for 1 h, labeled with [³⁵S]Met for 1.5 h, and harvested thereafter (the treatment with CHX or with anti-Fas continued during the methionine starvation and the radioactive pulse). The level of insoluble radioactivity incorporated per microgram of protein extract was set as 100% in control cells. The results represent the average of four independent experiments.