Fig. 2. Induction of p100 processing by Tax. (A) Jurkat cells were either not infected or infected with retroviral vectors encoding GFP or Tax. The cells were either not treated (–) or stimulated for 8 h with PMA plus ionomycin (+) followed by extract preparation and IB analysis using anti-p100 (upper panel) or anti-actin (lower panel). In lane 6, IB was performed using an extract isolated from a Tax-transformed T-cell line, Tax1. Non-specific bands are indicated by ns. (B) Jurkat cells (5 × 10⁶) were transfected with p100 (1 µg) together with either an empty vector or Tax (1 µg) followed by mitogen treatment as indicated. Exogenous p100/p52 and Tax were analyzed by IB using anti-p100 (upper panel) and anti-Tax (lower panel). (C) Induction of p100 processing by Tax in 293 cells. 293 cells were transfected with p100 (0.5 µg) together with either an empty vector or Tax (1 µg) followed by IB assays.