Loss of the BH3-only protein Puma protects mast cells from apoptosis induced by treatment with etoposide, a p53-dependent death stimulus. Survival of mast cells treated with 1 μg/mL of etoposide was measured by staining with PI plus annexin V-FITC. (A) MLMCs, where ◇ indicates wt; ρ, Noxa^−/−; ×, Bad^−/−; and ○, Bid^−/−. N = 2-6. (B) CTLMCs, where ◇ indicates wt; ▵, Noxa^−/−; ×, Bad^−/−; ○, Bid^−/−; and □, Bmf^−/−. N = 2-4. (C) MLMCs, where ◇ indicates wt; −, vav-Bcl2; ●, Puma^−/−; ▴, Puma^+/−. N = 6. (D) CTLMCs, where ◇ indicates wt; −, vav-Bcl2; ●, Puma^−/−; ▴, Puma^+/−. N = 3-4, and results are presented as mean (± SD). (E, top) MLMCs, where ◇ indicates wt and ◆, p53^−/−. N = 6, and results are presented as mean (± SD). (E, bottom) Expression of Puma was determined by Western blotting of lysates from wt and p53^−/− MLMCs following etoposide treatment for 10 hours. The results shown are representative of at least 3 independent experiments. (F, top) CTLMCs, where ◇ indicates wt and ◆, p53^−/−. N = 3-4 and results are presented as mean (± SD). (F, bottom) Expression of Puma was determined by Western blotting of lysates from wt and p53^−/− CTLMCs following etoposide treatment for 10 hours. The results shown are representative of at least 3 independent experiments.