ADENOVIRUS E1B-19K BCL-2 INTERACTING PROTEIN BNIP3 CONTAINS A BH3 DOMAIN AND A MITOCHONDRIAL TARGETING SEQUENCE/

Adenovirus E1B-19K and BCL-2 anti-apoptosis proteins interact with cer tain BCL-2 family pro-apoptotic proteins. A conserved domain, BH3, pre sent in these proteins is essential for their pro-apoptotic activity a nd for heterodimerization with anti-apoptosis proteins. Cellular prote in BNIP3 (previously NIP3) interacts with E1B-19K, BCL-2, BCL-x(L), an d EBV-BHRF1. BNIP3 contains a motif similar to the BH3 domain. Deletio n of the BH3-like motif in BNIP3 abrogates its ability to heterodimeri ze with E1B-19K and BCL-x(L). Substitution of the BH3 domain of BNIP3 for the corresponding sequences of BAX functionally restores the pro-a poptotic and protein heterodimerization activities of BAX. BNIP3 exhib its a delayed cell death activity that is partially relieved by deleti on of the BH3 domain. BNIP3 suppresses the anti-apoptosis activity of BCL-x(L) in a BH3-dependent manner. BNIP3 contains a C-terminal trans- membrane (TM) domain similar to other BCL-8 family proteins and BNIP1 (previously NIP1). The TM domains of BNIP3 and BNIP1 can functionally substitute for the TM domain of a BCL-2 family member EBV-BHRF1. The B NIP3 TM domain exclusively targets the heterologous green fluorescent protein (GFP) to mitochondria. These results suggest that BNIP3 is a m ember of the BH3-contaning BCL-2 family of pro-apoptotic proteins and functions in mitochondria.