Figure 4

Combined silencing of eIF4G1 and DAP5 accelerated radiation-induced apoptosis. Jurkat cells were transfected with 500 nM eif4g1 siRNA or 500 nM dap5 siRNA alone, or with both, 500 nM eif4g1 and 500 nM dap5 siRNA. 1 μM non-targeting (nt) siRNA was electroporated into control cells. (A) 48 h later, cells were lysed and analyzed by Western blot. Protein levels were analyzed by densitometry and normalized to the respective levels in control cells transfected with non-targeting siRNA. Silencing of eIF4G1 resulted in Mcl-1 decrease suggesting that Mcl-1 translation in non-irradiated cells was eIF4G1-dependent but DAP5-independent. (B-D) 48 h after electroporation, cells were irradiated with 10 Gy. (B) Cells were lysed 24 h after IR. Silencing of eIF4G1 or DAP5 had no effect on radiation-induced Mcl-1 decline. Dissipation of the mitochondrial membrane potential (ΔΨm low, C) and DNA fragmentation (sub G1, D) were analyzed by flow cytometry 24 h and 48 h after IR, respectively. Slightly enhanced ΔΨm dissipation and DNA fragmentation was observed when both, eIF4G1 and DAP5, were silenced at the same time. Flow cytometric data shows mean values ± S.D. (n = 3), *** indicates p < 0.001.