Fig. 3.
Bax D68R is constitutively active in the absence of Bcl-xL. (A) Bax D68R kills MEF lacking Bcl-xL. The viability of MEF lacking the indicated prosurvival proteins was determined by propidium iodide exclusion 24 h after infection with retroviruses expressing either WT or D68R Bax. (B) Bax D68R prevents colony formation by Bcl-xL-deficient MEF. The bcl-x−/− MEF or a subclone stably expressing Bcl-xL were infected with retroviruses expressing Bax, Bax D68R, or an empty control vector and colony formation assessed 6 d later. (C) Only Bcl-xL counters apoptosis induced by Bax D68R in MEF lacking Bcl-xL. The viability of bcl-x−/− MEF stably expressing the indicated prosurvival proteins was determined 24 h after reinfection with a Bax or Bax D68R retrovirus. Data in A and C (except for Bcl-xL mt1) represent means ± 1 SEM of 3 or more independent experiments.