FAIM-L interacts with XIAP through its BIR2 domain. A, Schematic representation of FLAG-tagged XIAP deletion and point mutants. B, HEK293T cells were transfected with FLAG-tagged XIAP and its deletion mutants as indicated together with a 3xHA-FAIM-L expression plasmid, and FLAG-tagged XIAP was immunoprecipitated before immunoblotting with HA and FLAG antibodies. C, HEK293T cells were transfected with FLAG-tagged XIAP and its point mutants as indicated together with a 3xHA-FAIM-L expression plasmid. Immunoprecipitation and Western blotting were performed as in B. D, PC12 cells were transfected with FLAG-tagged XIAP and its point mutants with or without the coexpression of the 3xHA-FAIM-L plasmid. Immunoprecipitation was performed as in B before immunoblotting with Smac, HA, and FLAG antibodies.