Mutations within Bfl-1's C-terminal region dramatically alter its half-life. (A) Schematic representation of GFP-Bfl-1 and of C-terminal deletion and point mutants. The BH1-3 domains and putative BH4 domain are shown. The C-terminal domain deleted in Bfl-1ΔC is underlined. Enlarged amino acids were substituted by mutagenesis with arginine (KKK/RRR), aspartic acid (ST/DD), or alanine (ST/AA). (B) Half-life of Bfl-1 mutants in FL5.12 cells treated with cycloheximide and collected at time intervals followed by Western blot with anti-GFP or actin as control. Protein amounts were quantified with the Alphaimager 2200 program.