Figure 5.

Bcl-2 blocks cell death and promotes cell-cycle arrest in E2A-deficient lymphoma lines transduced with E47. (A) Inhibition of E47-mediated death by Bcl-2. The 1.F9 E2A-deficient lymphoma line was transduced with retrovirus encoding Bcl-2 or ‘empty vector' retrovirus, cultured for 2 days, and then infected with retrovirus encoding E47 or a mutant form of E12 that does not bind DNA (E12BM). Cells were harvested 7, 24 or 48 h after transduction with E2A and the percentage of viable cells was determined by flow cytometry on the basis of forward and side scatter. The relative viability of each cell population (normalized to the viability of the BM-transduced population at 7 h post-transduction) is plotted against the time of harvest. Transduction efficiency was 90% or greater in all populations tested (data not shown). (B) Size reduction induced by E47 transduction into Bcl-2-expressing, E2A-deficient lymphoma lines. 1.F9 cells sequentially transduced with Bcl-2 and either E47 or E12BM retrovirus were fixed and permeabilized 48 h after E2A transduction, stained for ectopic E2A protein, and analyzed by flow cytometry. Plotted are the forward scatter profiles of the E2A⁺, live-gated cells within each population. (C) G₀ or G₁ arrest induced by transduction of both Bcl-2 and E47 into E2A-deficient lymphomas. 1.F9 cells treated as described in Figure 5B were analyzed for DNA content. Also included are cells sequentially transduced with empty vector and E12BM. Plots depict the DNA content profiles of the E2A-expressing cells within each population.