BNIP3L (BCL2/adenovirus E1B 19kDa interacting protein 3-like)

	Organization of the human BNIP3L gene. The boxes represent exons, the line introns (not drawn to scale). Black areas represent coding sequence.
Description	The gene spans 30122 bp and has 6 exons. The cytogenetic location of the gene is 8p21.2. The genomic coordinates are 8: 26240522 - 26270643.
Transcription	The mRNA is 3505 bp, and has a 657 bp open reading frame.

	Functional domains of BNIP3L protein. LIR: LC3-interaction region (WVEL) (Schwarten et al., 2009; Novak et al., 2010); MER: minimal essential region (DMEKILLDAQHE) (Zhang et al., 2012); BH3-like: BCL2 homology 3-like domain (LKKSADWVSDW) (Yasuda et al., 1999); TM: transmembrane domain.
Description	The protein is 219 amino acids, with a predicted MW of 23,8 kDa. The carboxy-terminal transmembrane domain of BNIP3L has been characterized by nuclear magnetic resonance and shown to form a kinked α-helix (Bocharov et al., 2007). Structural bioinformatics analysis indicates that the rest of the protein is mostly disordered. The LIR and the MER are predicted to form secondary structure (β-strand and α-helix, respectively) (Zhang et al., 2012).
Expression	BNIP3L is ubiquitously expressed. Northern blot hybridization reveals two transcripts of 1,6 kb and 3,9 kb. These are expressed in heart, brain, placenta, lung, liver, skeletal muscle, kidney, and pancreas (Yasuda et al., 1999). In another study, transcripts were identified in heart, brain, placenta, lung (low), liver, skeletal muscle (low), kidney, pancreas, spleen, thymus, prostate, testis, ovary, small intestine, colon, and peripheral blood leukocyte (Farooq et al., 2001). In the same study, there was also expression in cancer cell lines, including promyelocytic HL-60 (low), Hela S3 (low), K562, lymphoblastic leukemia Molt-5, Burkitt's lymphoma-Raji, colorectal adenocarcinoma SW480, and lung carcinoma A549 cells. In another study, 1,4 and 4,0 kb BNIP3L transcripts were found in primary hematopoietic cells and in cell lines, including K562, Hela, and Jurkat cells (Aerbajinai et al., 2003). BNIP3L is upregulated during erythroid maturation. BNIP3L protein can form an SDS-resistant dimer, which migrates at twice its predicted MW in SDS-PAGE gels. BNIP3L dimerization is mediated through its transmembrane domain (Imazu et al., 1999).
Localisation	BNIP3L primarily localizes to the mitochondrial outer membrane (Chen et al., 1999; Imazu et al., 1999; Yasuda et al., 1999; Vande Velde et al., 2000). BNIP3L is oriented so that its amino terminus is in the cytoplasm, and its carboxy-terminal tail is in the mitochondrial intermembrane space. It also localizes to nuclear envelope, sarcoplasmic reticulum, and endoplasmic reticulum (Ohi et al., 1999; Diwan et al., 2009).
Function	BNIP3L and BNIP3 can cause cell death by several mechanisms, which are mediated by their BH3-like and transmembrane domains. In cardiomyocytes, mitochondria-targeted BNIP3L causes BAX/BAK-dependent mitochondrial outer membrane permeabilization, whereas ER/SR-targeted BNIP3L causes cyclophilin D-dependent opening of the MPT pore and mitochondrial depolarization (Chen et al., 2010). In tumor cells, BNIP3 expression is associated with opening of the MPT pore and autophagy (Vande Velde et al., 2000). Another property of BNIP3L and BNIP3 is their ability to mediate mitochondrial clearance during erythroid development (Schweers et al., 2007; Sandoval et al., 2008) and in response to hypoxia (Zhang et al., 2008; Liu et al., 2012), respectively. BNIP3L mediates mitochondrial clearance in erythroid cells through its LIR (Schwarten et al., 2009; Novak et al., 2010) and MER (Zhang et al., 2012) domains.
Homology	BNIP3L is conserved from zebrafish to man.

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