{"gene":"BIRC6","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2004,"finding":"BRUCE functions as a chimeric E2/E3 ubiquitin ligase and inhibitor of apoptosis (IAP) protein localized to the trans-Golgi network. Its BIR domain is required for caspase inhibition and anti-apoptotic activity. BRUCE is antagonized by Smac binding, HtrA2 protease cleavage, and caspase-mediated cleavage. BRUCE ubiquitinates Smac as a substrate.","method":"Wild-type and mutant protein overexpression, in vitro ubiquitination assay, co-immunoprecipitation, caspase activity assay, apoptosis induction assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including in vitro ubiquitination, domain mutagenesis, and functional apoptosis assays in single rigorous study","pmids":["15200957"],"is_preprint":false},{"year":2004,"finding":"Nrdp1/FLRF, a RING finger E3 ubiquitin ligase, associates with BRUCE and promotes its ubiquitination and proteasomal degradation. Purified Nrdp1 catalyzes BRUCE ubiquitination in vitro in the presence of E2 UbcH5c. Apoptotic stimuli induce proteasomal degradation of BRUCE, and reducing Nrdp1 by RNAi attenuates BRUCE loss and reduces apoptosis.","method":"Co-immunoprecipitation, in vitro ubiquitination assay with purified proteins, RNAi knockdown, proteasome inhibitor experiments","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro ubiquitination with purified Nrdp1, validated by RNAi in vivo","pmids":["14765125"],"is_preprint":false},{"year":2004,"finding":"BRUCE/Apollon associates with precursor and mature forms of Smac, HtrA2, and caspase-9 through regions beyond the IAP-binding motif. BRUCE promotes degradation of Smac and inhibits caspase-9 activity but not caspase-3 activity. Upon apoptotic stimuli, BRUCE is degraded by proteasomes or cleaved by caspases and HtrA2 in a stimulus- and cell type-dependent manner.","method":"Co-immunoprecipitation, caspase activity assays, proteasome inhibitor and caspase inhibitor experiments, in vitro binding assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal biochemical methods identifying substrates and mechanism of caspase inhibition","pmids":["15507451"],"is_preprint":false},{"year":2004,"finding":"BRUCE is a 528 kDa peripheral membrane protein of the trans-Golgi network required for normal placental development in mice. Complete inactivation causes perinatal lethality due to impaired maturation of the labyrinth layer and reduced spongiotrophoblast in the placenta, without elevated apoptosis in embryonic tissues.","method":"Knockout mouse generation and characterization, histological analysis, TUNEL assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with specific in vivo phenotypic readout replicated in multiple studies","pmids":["15485903"],"is_preprint":false},{"year":2005,"finding":"Deletion of the C-terminal half of BRUCE (including the UBC domain) in mice causes caspase activation and apoptosis in placenta and yolk sac, leading to embryonic lethality. This apoptosis involves p53 upregulation and nuclear localization, Bax/Bak upregulation, mitochondrial translocation of Bax and caspase-2, cytochrome c and AIF release, and caspase-9/-3 activation. RNAi of p53 rescues cell viability in Bruce-ablated cells by reducing Bax, Bak, Pidd expression and preventing caspase-2/-9/-3 activation.","method":"Conditional knockout mouse, RNAi, caspase activity assays, subcellular fractionation, western blot for apoptosis markers","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with RNAi rescue, multiple orthogonal readouts establishing pathway position","pmids":["15640352"],"is_preprint":false},{"year":2005,"finding":"Bruce mutant mice (gene trap) show progressive loss of the spongiotrophoblast layer between embryonic days 11.5 and 14.5, resulting in embryonic lethality due to lack of spongiotrophoblast cell proliferation rather than elevated apoptosis.","method":"Gene trap mutagenesis, histological analysis, proliferation assays","journal":"Genesis (New York, N.Y. : 2000)","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with specific phenotype, consistent with Lotz et al. 2004 but single lab","pmids":["15887267"],"is_preprint":false},{"year":2008,"finding":"During cytokinesis, BRUCE translocates from the vesicular system to the midbody ring and serves as a platform for membrane delivery machinery and mitotic regulators. BRUCE depletion causes defective abscission and cytokinesis-associated apoptosis, blocks vesicular targeting, and disrupts midbody and midbody ring formation. Ubiquitin relocalizes from midbody microtubules to the midbody ring during cytokinesis, and BRUCE depletion disrupts this process.","method":"RNAi knockdown in cell culture, live imaging, immunofluorescence, subcellular fractionation","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — clean KD with specific cellular phenotypes, live imaging of localization change, multiple readouts in high-impact study","pmids":["18329369"],"is_preprint":false},{"year":2008,"finding":"In Drosophila oogenesis, the effector caspase Dcp-1 and IAP protein Bruce function together to regulate both starvation-induced autophagy and cell death at germarium and mid-oogenesis checkpoints.","method":"Drosophila genetics (mutant analysis), systematic RNAi screen in cultured cells, DNA fragmentation assays","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in Drosophila with specific in vivo phenotypic readouts","pmids":["18794330"],"is_preprint":false},{"year":2008,"finding":"Prostaglandin F2alpha (PGF2alpha) increases BRUCE expression through an NFAT2-dependent pathway, reducing muscle cell death during myogenesis. BRUCE overexpression is sufficient to promote muscle cell survival and myotube growth, establishing a PGF2alpha-NFAT2-BRUCE signaling axis.","method":"In vitro myogenesis assay, siRNA knockdown, overexpression constructs, in vivo mouse experiments","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional rescue and KD experiments with pathway placement, single lab","pmids":["18566603"],"is_preprint":false},{"year":2011,"finding":"Drosophila BRUCE (dBruce) ubiquitinates the IAP-antagonist Reaper through an unconventional mechanism involving non-lysine ubiquitin acceptor sites. dBruce physically interacts with Reaper dependent on Reaper's IAP-binding (IBM) and GH3 motifs. dBruce loss elevates Reaper protein levels.","method":"Co-immunoprecipitation, in vivo ubiquitination assay with lysine-deficient Reaper mutants, genetic loss-of-function analysis","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical ubiquitination assay combined with mutagenesis of ubiquitin acceptor sites and genetic validation","pmids":["21886178"],"is_preprint":false},{"year":2013,"finding":"EBV-encoded miRNA miR-BART15-3p directly targets the 3' UTR of BRUCE mRNA at a specific seed-matched site, suppressing BRUCE protein translation and promoting apoptosis in EBV-negative and EBV-infected cells.","method":"Luciferase reporter assay with 3'UTR constructs, mutation analysis of seed-match sites, western blot, miRNA inhibitor experiments","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 — luciferase reporter with mutagenesis plus functional rescue, single lab","pmids":["23678170"],"is_preprint":false},{"year":2014,"finding":"BIRC6 interacts with p53 and facilitates its degradation, promoting hepatocellular carcinogenesis. BIRC6 knockdown activates p53, causes G1/S arrest, and sensitizes hepatoma cells to sorafenib-induced apoptosis, with these effects partially reversed by p53 RNAi.","method":"Co-immunoprecipitation, lentiviral shRNA knockdown, flow cytometry, RNAi epistasis, xenograft tumor model","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP plus epistasis experiments, single lab","pmids":["25196217"],"is_preprint":false},{"year":2015,"finding":"BRUCE acts as a scaffold bridging USP8 and BRIT1 in a complex. BRIT1 is K63-ubiquitinated in unstressed cells, and BRUCE promotes USP8-catalyzed deubiquitination of BRIT1, which is prerequisite for BRIT1 recruitment to DSB sites via γ-H2AX binding. Loss of BRUCE impairs BRIT1 deubiquitination, BRIT1 DNA damage foci formation, chromatin relaxation, and homologous recombination repair.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, chromatin immunoprecipitation, HR repair assay, BRUCE-mutant mouse analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, epistasis, multiple orthogonal assays, validated in mouse model","pmids":["25733871"],"is_preprint":false},{"year":2015,"finding":"The UBC domain of BRUCE (but not the BIR domain) is required for promoting USP8-mediated deubiquitination of BRIT1 and its recruitment to DSBs. UBC domain mutation or deletion does not disrupt the BRUCE-USP8-BRIT1 complex but impairs BRIT1 deubiquitination, chromatin relaxation, accumulation of MDC1, NBS1, pATM, and RAD51 at DSBs, and homologous recombination repair.","method":"Domain deletion/mutation analysis, in vivo ubiquitination assay, co-immunoprecipitation, immunofluorescence, HR repair assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 — domain mutagenesis with multiple orthogonal mechanistic readouts","pmids":["26683461"],"is_preprint":false},{"year":2017,"finding":"BIRC6 protein stability is regulated by the Src family kinase Lyn in imatinib-resistant CML cells. Lyn inhibition or knockdown reduces BIRC6 protein stability, promotes formation of an N-terminal BIRC6 fragment, and reduces BIRC6 phosphopeptide levels (phosphorylated at S480, S482, S486), suggesting Lyn regulates BIRC6 phosphorylation and stability. BIRC6 mediates imatinib resistance independently of Mcl-1.","method":"Phosphoproteomic analysis, lentiviral shRNA knockdown, kinase inhibitor treatment, caspase activation assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — phosphoproteomic identification plus pharmacological and genetic inhibition, single lab","pmids":["28520795"],"is_preprint":false},{"year":2018,"finding":"BRUCE promotes autophagosome-lysosome fusion by selectively interacting with ATG8 family members GABARAP and GABARAPL1 and with Syntaxin 17, and colocalizes with LAMP2. BRUCE depletion leads to defective autolysosome formation. A non-catalytic N-terminal BRUCE fragment sufficient to bind GABARAP/GABARAPL1 and Syntaxin 17 rescues autolysosome formation, indicating this function is independent of ubiquitin-conjugating activity.","method":"RNAi screen, co-immunoprecipitation, immunofluorescence colocalization, domain deletion rescue experiments in Bruce-/- cells, autophagic flux assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — RNAi screen plus reciprocal co-IP, domain deletion rescue in KO cells, multiple orthogonal methods","pmids":["29426817"],"is_preprint":false},{"year":2019,"finding":"UBA6 and BIRC6 cooperate to monoubiquitinate LC3B, targeting it for proteasomal degradation. Knockout of UBA6 or BIRC6 increases autophagic flux under nutrient deprivation and decreases aggresome-like structures and α-synuclein aggregates, demonstrating that UBA6-BIRC6 negatively regulate autophagy by limiting LC3B availability.","method":"Whole-genome CRISPR/Cas9 knockout screen, LC3B ubiquitination assay, autophagic flux assays, α-synuclein aggregate quantification in neurons","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — genome-wide screen identification, biochemical ubiquitination assay, validated in multiple cellular contexts","pmids":["31692446"],"is_preprint":false},{"year":2019,"finding":"BRUCE together with the proteasome activator PA28γ causes proteasomal degradation of LC3-I, inhibiting autophagy. SIP/CacyBP inhibits BRUCE-mediated degradation of LC3-I under normal conditions by blocking Nrdp1 binding to BRUCE. Upon starvation, SIP enhances BRUCE translocation into the recycling endosome and promotes autophagic destruction of BRUCE via optineurin-mediated autophagy.","method":"Co-immunoprecipitation, LC3-I degradation assays, RNAi knockdown, subcellular fractionation, autophagic flux assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical and cell biological methods establishing mechanism, single lab","pmids":["31213539"],"is_preprint":false},{"year":2019,"finding":"BRUCE depletion promotes autophagy induction by lowering cellular energy levels (elevated AMP/ATP ratio) and activating AMPK (pThr-172), which then activates ULK1 (pSer-555) to initiate autophagy. This is distinct from starvation-induced autophagy, as BRUCE depletion alone does not block autophagosome-lysosome fusion. BRUCE depletion-induced autophagy is coupled to enhanced cisplatin resistance in ovarian cancer cells.","method":"AMP/ATP ratio measurement, AMPK and ULK1 phosphorylation assays, autophagy flux assays, ATG16L puncta quantification, lysosomal enzyme activity measurement","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — mechanistic pathway dissection with multiple markers, single lab","pmids":["31091257"],"is_preprint":false},{"year":2019,"finding":"BRUCE is recruited to induced DNA damage sites and is required for ATR activation during replication stress. BRUCE depletion inhibits ATR auto-activation, phosphorylation of CHK1 and RPA, and monoubiquitination of FANCD2. BRUCE deficiency results in stalled DNA replication forks and increased firing of new replication origins. Liver-specific BRUCE knockout in mice impairs ATR activation and exacerbates inflammation, fibrosis, and hepatocellular carcinoma.","method":"Immunoprecipitation, in vitro kinase assays, DNA fiber assays, conditional liver-specific KO mouse model with DEN-induced HCC","journal":"Hepatology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 — multiple biochemical readouts of ATR signaling plus in vivo validation in liver-specific KO mouse model","pmids":["30693543"],"is_preprint":false},{"year":2021,"finding":"BIRC6 stability is increased by EGF-JNK signaling, which prevents ubiquitination and degradation of BIRC6 mediated by the E3 ubiquitin ligase HECTD1. BIRC6 in turn decreases SMAC expression by inducing the ubiquitin-proteasome pathway, antagonizing apoptosis.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, western blot, xenograft tumor model","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP plus ubiquitination assay identifying HECTD1 as E3, single lab","pmids":["34729249"],"is_preprint":false},{"year":2021,"finding":"BRUCE interacts with Syntaxin 17 (STX17) as shown by co-immunoprecipitation and colocalization. miR-204 targets BRUCE, and knockdown of STX17 or BRUCE inhibits autophagosome-lysosome fusion and impairs axon growth, contributing to axonal dystrophy in an Alzheimer's disease cell model.","method":"Co-immunoprecipitation, dual luciferase reporter assay, immunofluorescence, RNAi knockdown","journal":"Translational psychiatry","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP confirms BRUCE-STX17 interaction, functional readout with RNAi, single lab","pmids":["34354038"],"is_preprint":false},{"year":2021,"finding":"BRUCE deficiency in male germline leads to impaired spermatogonia maintenance, persistent meiotic DNA breaks, impaired homologous synapsis, chromosomal fragmentation and translocations. Bruce-deficient pachytene spermatocytes show unsynapsed regions devoid of ATM and ATR signaling, indicating BRUCE is required for ATM- and ATR-dependent meiotic homologous recombination.","method":"Germline-specific conditional KO mouse, FISH, immunofluorescence for synaptonemal complex components, ATM/ATR signaling markers","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 — clean conditional KO with multiple specific cytogenetic and molecular readouts","pmids":["32139899"],"is_preprint":false},{"year":2021,"finding":"BRUCE deficiency combined with PKA activates β-catenin through PKA-dependent phosphorylation at Ser-675 (pSer-675-β-catenin) and promotes nuclear β-catenin accumulation. BRUCE and PKA colocalize in hepatocyte cytoplasm, and BRUCE suppresses PKA activity. BRUCE deficiency elevates PKA activity and activates β-catenin signaling during liver disease progression.","method":"Co-localization by immunofluorescence, PKA activity assay, western blot for phospho-β-catenin, liver-specific KO mouse model","journal":"World journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2-3 — subcellular colocalization plus kinase activity assay in KO model, single lab","pmids":["33815677"],"is_preprint":false},{"year":2023,"finding":"Cryo-EM structures show BIRC6 forms a megadalton crescent-shaped antiparallel dimer with a spacious central cavity containing client protein receptor sites. BIRC6 directly restricts executioner caspase-3 and -7 and ubiquitinates caspase-3, -7, and -9 exclusively via non-canonical E1 UBA6. SMAC binds BIRC6 with multisite, subnanomolar affinity, competitively displacing caspases and obstructing ubiquitination of both apoptotic and autophagy substrates.","method":"Cryo-electron microscopy structure determination, in vitro caspase inhibition assays, in vitro ubiquitination assay, ITC binding measurements","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structures with functional validation by biochemical assays, replicated across multiple concurrent studies in the same issue","pmids":["36758105","36758106","36758104"],"is_preprint":false},{"year":2024,"finding":"BIRC6 forms an antiparallel U-shaped dimer with multiple previously unannotated domains including a ubiquitin-like domain. SMAC/DIABLO binds BIRC6 in the central cavity and outcompetes effector caspase-3 and HtrA2 but not procaspase-9 for BIRC6 binding in cells. BIRC6 also binds LC3 through its LC3-interacting region (LIR). Induction of autophagy promotes autophagic degradation of BIRC6 and caspase-9 but not other effector caspases.","method":"Cryo-EM structure, co-immunoprecipitation competition assay, LC3-pull down, LC3 ubiquitylation site mutagenesis, autophagic flux assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure combined with multiple biochemical functional validation experiments","pmids":["38291026"],"is_preprint":false},{"year":2024,"finding":"BIRC6 acts as a ubiquitin ligase for KRAS4A, interacting with it on the Golgi apparatus and promoting mono- and di-ubiquitination of KRAS4A at lysines 128 and 147. This interaction is specific to KRAS4A over KRAS4B. Silencing BIRC6 diminishes GTP loading of KRAS4A and suppresses KRAS4A-driven growth stimulation.","method":"Proximity labeling interactome mapping, co-immunoprecipitation, ubiquitination site mapping by mass spectrometry, GTP-loading assay, RNAi knockdown","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 — proximity labeling plus biochemical ubiquitination site identification and functional consequence demonstrated","pmids":["39705142"],"is_preprint":false},{"year":2024,"finding":"BIRC6 modulates Axin protein stability by interacting with Axin and promoting its ubiquitination and degradation, thereby activating β-catenin signaling in renal cell carcinoma cells.","method":"Co-immunoprecipitation, ubiquitination assay, protein turnover assay, siRNA knockdown, xenograft tumor model","journal":"ACS omega","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP plus ubiquitination assay with functional β-catenin pathway readouts, single lab","pmids":["38405482"],"is_preprint":false},{"year":2025,"finding":"BIRC6 gains priority access to UBA6 over all other UBA6-competent E2s through an exceptionally high-affinity interaction mediated by BIRC6 engagement with the UBA6 ubiquitin fold domain, modulated by the UBA6 Cys-Cap loop. BIRC6 disengages from UBA6 upon receiving ubiquitin via a bespoke thioester switch mechanism to prevent inhibition of UBA6.","method":"Cryo-EM structures of BIRC6-UBA6 complexes in different states, biochemical E1-E2 specificity assays, domain mutagenesis","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structures plus in vitro biochemical reconstitution with mutagenesis","pmids":["41350950"],"is_preprint":false}],"current_model":"BIRC6 (BRUCE/Apollon) is a giant (~528 kDa) antiparallel dimeric protein of the trans-Golgi network that functions as both an IAP (inhibiting caspase-3, -7, and -9 via direct binding and ubiquitination) and a chimeric E2/E3 ubiquitin ligase operating exclusively through the non-canonical E1 UBA6, with its BIR domain mediating caspase suppression and its UBC domain driving ubiquitination of substrates including Smac, LC3B, KRAS4A, and Axin; SMAC binds BIRC6 with subnanomolar affinity to competitively displace caspases and block ubiquitination of both apoptotic and autophagic substrates, while upstream regulators Nrdp1 and Lyn control BIRC6 stability via ubiquitin-proteasomal degradation, and BIRC6 additionally promotes autophagosome-lysosome fusion through direct interactions with GABARAP/GABARAPL1 and Syntaxin 17, regulates DNA double-strand break repair as a scaffold bridging USP8 and BRIT1, and activates ATR signaling to maintain replication fork stability."},"narrative":{"teleology":[{"year":2004,"claim":"Establishing BIRC6 as a bifunctional IAP and E2/E3 ubiquitin ligase resolved how a single protein could both inhibit caspases and target pro-apoptotic factors like Smac for ubiquitin-dependent degradation.","evidence":"In vitro ubiquitination assays, domain mutagenesis, caspase activity assays, and co-immunoprecipitation in mammalian cells","pmids":["15200957","15507451"],"confidence":"High","gaps":["E1 enzyme specificity for BIRC6 was unknown","structural basis for dual BIR/UBC function unresolved","full substrate repertoire undefined"]},{"year":2004,"claim":"Identification of Nrdp1 as an E3 ligase promoting BIRC6 proteasomal degradation during apoptosis established that BIRC6 protein levels are actively regulated upstream, explaining how cells overcome its anti-apoptotic activity.","evidence":"Reconstituted in vitro ubiquitination with purified Nrdp1 plus RNAi validation in cells","pmids":["14765125"],"confidence":"High","gaps":["Signals triggering Nrdp1-mediated BIRC6 degradation not fully defined","additional upstream E3 ligases not explored"]},{"year":2004,"claim":"Knockout mouse studies revealed that BIRC6 is essential for placental development and perinatal viability, demonstrating a critical in vivo developmental function beyond apoptosis suppression.","evidence":"Complete and partial knockout mice with histological and TUNEL analysis of placenta","pmids":["15485903","15887267"],"confidence":"High","gaps":["Whether placental defect reflects apoptotic or proliferative role was debated across labs","downstream targets in trophoblast differentiation unknown"]},{"year":2005,"claim":"Conditional deletion of the BIRC6 UBC domain proved that its ubiquitin-conjugating activity is required to suppress a p53-dependent mitochondrial apoptosis cascade involving Bax, caspase-2, and caspase-9 in vivo.","evidence":"Conditional knockout mouse with p53 RNAi rescue, subcellular fractionation, and caspase activation assays","pmids":["15640352"],"confidence":"High","gaps":["Direct ubiquitination substrates mediating p53 suppression not identified","whether BIRC6 ubiquitinates p53 directly was unresolved"]},{"year":2008,"claim":"Discovery that BIRC6 translocates from vesicular membranes to the midbody ring during cytokinesis and is required for abscission revealed an unexpected cell-division function independent of classical IAP activity.","evidence":"RNAi knockdown, live imaging, and immunofluorescence in dividing mammalian cells","pmids":["18329369"],"confidence":"High","gaps":["Substrates ubiquitinated at the midbody ring not identified","mechanism of BIRC6 vesicular targeting to midbody unknown"]},{"year":2011,"claim":"Demonstration that Drosophila BRUCE ubiquitinates the IAP-antagonist Reaper via non-lysine residues established an unconventional ubiquitination mechanism for IAP-antagonist neutralization.","evidence":"In vivo ubiquitination assay with lysine-deficient Reaper mutants and genetic loss-of-function in Drosophila","pmids":["21886178"],"confidence":"High","gaps":["Non-lysine acceptor site identity (Ser/Thr/Cys) unresolved","conservation of non-lysine ubiquitination for mammalian BIRC6 substrates not tested"]},{"year":2015,"claim":"Identification of BIRC6 as a scaffold bridging USP8 and BRIT1 to enable BRIT1 deubiquitination and recruitment to DNA damage sites established a direct role for BIRC6 in homologous recombination repair, with the UBC domain required for promoting USP8 activity.","evidence":"Reciprocal co-immunoprecipitation, in vivo ubiquitination assays, HR repair assays, and domain mutagenesis in BRUCE-mutant cells and mice","pmids":["25733871","26683461"],"confidence":"High","gaps":["Whether BIRC6 UBC domain directly ubiquitinates a component of the repair complex or acts allosterically unclear","how BIRC6 is recruited to DSB sites unknown"]},{"year":2018,"claim":"Discovery that BIRC6 promotes autophagosome–lysosome fusion through non-catalytic binding of GABARAP/GABARAPL1 and Syntaxin 17 revealed a ubiquitin-independent membrane-tethering function, separating its autophagy-promoting role from its E2/E3 activity.","evidence":"RNAi screen, co-immunoprecipitation, domain deletion rescue in Bruce−/− cells, and autophagic flux assays","pmids":["29426817"],"confidence":"High","gaps":["Structural basis for selectivity of GABARAP over LC3 subfamily binding unresolved","whether BIRC6 tethers autophagosomes to lysosomes directly or via intermediate complexes not determined"]},{"year":2019,"claim":"Genome-wide CRISPR screening identified UBA6 as the exclusive E1 for BIRC6-mediated monoubiquitination and proteasomal degradation of LC3B, establishing UBA6–BIRC6 as a negative regulator of autophagy that limits LC3B availability.","evidence":"Whole-genome CRISPR/Cas9 screen, LC3B ubiquitination assay, autophagic flux measurement, and α-synuclein aggregate quantification in neurons","pmids":["31692446"],"confidence":"High","gaps":["Which LC3B lysine residues are ubiquitinated not fully mapped","whether other ATG8 family members are similarly targeted unknown"]},{"year":2019,"claim":"Demonstration that BIRC6 is required for ATR activation, CHK1 phosphorylation, and replication fork stability—with liver-specific knockout exacerbating hepatocarcinogenesis—established BIRC6 as a replication stress response factor distinct from its DSB repair role.","evidence":"IP-kinase assays, DNA fiber assays, conditional liver-specific KO mouse with DEN-induced HCC","pmids":["30693543"],"confidence":"High","gaps":["Mechanism by which BIRC6 activates ATR (direct binding vs. scaffold) not established","relationship between ATR and BRIT1/USP8 repair functions unclear"]},{"year":2021,"claim":"Germline-specific knockout proved BIRC6 is essential for meiotic homologous recombination via ATM/ATR signaling at unsynapsed chromosomal regions, extending its DNA repair role to a specialized developmental context.","evidence":"Germline-specific conditional KO mouse with immunofluorescence for synaptonemal complex components and ATM/ATR markers","pmids":["32139899"],"confidence":"High","gaps":["Direct interaction partners mediating BIRC6 recruitment to meiotic chromosomes unknown","whether BIRC6 ubiquitinates meiotic repair substrates not tested"]},{"year":2023,"claim":"Cryo-EM structures revealing the BIRC6 antiparallel dimer with a central substrate-binding cavity, combined with quantitative binding data showing SMAC's subnanomolar multisite engagement that displaces caspases and blocks ubiquitination, provided the first structural framework integrating BIRC6's IAP and E2/E3 functions.","evidence":"Cryo-EM structure determination, ITC binding measurements, in vitro caspase inhibition and ubiquitination assays across three concurrent studies","pmids":["36758105","36758106","36758104"],"confidence":"High","gaps":["Conformational dynamics during ubiquitin transfer cycle unresolved","how dimer architecture accommodates diverse substrates of vastly different sizes not explained"]},{"year":2024,"claim":"Identification of KRAS4A as a splice-variant-specific BIRC6 substrate ubiquitinated at K128/K147 on the Golgi linked BIRC6's E3 activity to RAS signaling regulation, revealing a new oncogenic signaling axis.","evidence":"Proximity labeling interactome, co-immunoprecipitation, mass spectrometry ubiquitination site mapping, and GTP-loading assay","pmids":["39705142"],"confidence":"High","gaps":["Whether KRAS4A ubiquitination promotes degradation or alters signaling competence not fully resolved","selectivity mechanism excluding KRAS4B not structurally explained"]},{"year":2025,"claim":"Cryo-EM structures of the BIRC6–UBA6 complex revealed a bespoke high-affinity engagement mechanism via the UBA6 ubiquitin fold domain and a thioester switch that ejects BIRC6 after ubiquitin loading, explaining how BIRC6 achieves priority E1 access over other UBA6-competent E2 enzymes.","evidence":"Cryo-EM structures of BIRC6–UBA6 in multiple states, biochemical E1–E2 specificity assays, and domain mutagenesis","pmids":["41350950"],"confidence":"High","gaps":["Whether the thioester switch is regulated by post-translational modifications in vivo unknown","structural basis for how UBA6 selectivity excludes UBE1 completely not resolved"]},{"year":null,"claim":"The integration of BIRC6's multiple functions—apoptosis suppression, autophagy regulation, DNA repair, cytokinesis, and KRAS signaling—into a unified regulatory model remains unresolved, particularly how substrate selection is spatiotemporally controlled within the dimer cavity.","evidence":"","pmids":[],"confidence":"Low","gaps":["No full-length structure with bound substrates other than SMAC","spatial and temporal regulation of BIRC6 dimer across different cellular compartments and cell cycle phases unknown","whether post-translational modifications (e.g., Lyn-mediated phosphorylation) switch BIRC6 between functions not tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,9,16,24,25,26,27]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,12,13,15]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,3,26]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[6]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[23,24]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[12,19,22]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,2,4,24]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[15,16,17,25]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[12,13,19,22]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,16,24,28]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[26,27]}],"complexes":["BIRC6 antiparallel homodimer","BIRC6-USP8-BRIT1 complex","UBA6-BIRC6 E1-E2 complex"],"partners":["UBA6","SMAC","USP8","BRIT1","STX17","GABARAP","GABARAPL1","NRDP1"],"other_free_text":[]},"mechanistic_narrative":"BIRC6 (BRUCE/Apollon) is a giant (~528 kDa) chimeric E2/E3 ubiquitin ligase and inhibitor of apoptosis protein that integrates apoptosis suppression, autophagy regulation, DNA damage repair, and cytokinesis through its multidomain architecture. Its BIR domain directly inhibits executioner caspases-3, -7, and -9, while its UBC domain catalyzes ubiquitination of substrates including Smac, caspases, LC3B, KRAS4A, and Axin exclusively via the non-canonical E1 UBA6, with which BIRC6 engages through a high-affinity bespoke thioester switch mechanism [PMID:15200957, PMID:36758105, PMID:31692446, PMID:39705142, PMID:41350950]. Structurally, BIRC6 forms an antiparallel crescent-shaped dimer with a central cavity harboring client receptor sites, where SMAC binds with subnanomolar multisite affinity to competitively displace caspases and block ubiquitination of both apoptotic and autophagic substrates [PMID:36758105, PMID:38291026]. Beyond apoptosis suppression, BIRC6 promotes autophagosome–lysosome fusion through non-catalytic interactions with GABARAP/GABARAPL1 and Syntaxin 17, scaffolds USP8-mediated deubiquitination of BRIT1 to enable homologous recombination repair, activates ATR signaling to maintain replication fork stability, and translocates to the midbody ring during cytokinesis to facilitate abscission [PMID:29426817, PMID:25733871, PMID:30693543, PMID:18329369]."},"prefetch_data":{"uniprot":{"accession":"Q9NR09","full_name":"Dual E2 ubiquitin-conjugating enzyme/E3 ubiquitin-protein ligase BIRC6","aliases":["BIR repeat-containing ubiquitin-conjugating enzyme","BRUCE","Baculoviral IAP repeat-containing protein 6","Ubiquitin-conjugating BIR domain enzyme apollon","APOLLON"],"length_aa":4857,"mass_kda":530.3,"function":"Anti-apoptotic protein known as inhibitor of apoptosis (IAP) which can regulate cell death by controlling caspases and by acting as an E3 ubiquitin-protein ligase (PubMed:14765125, PubMed:15200957, PubMed:18329369). Unlike most IAPs, does not contain a RING domain and it is not a RING-type E3 ligase (PubMed:15200957, PubMed:36758104, PubMed:36758105, PubMed:36758106). Instead acts as a dual E2/E3 enzyme that combines ubiquitin conjugating (E2) and ubiquitin ligase (E3) activities in a single polypeptide (PubMed:15200957, PubMed:36758104, PubMed:36758105, PubMed:36758106). Ubiquitination is mediated by a non-canonical E1 ubiquitin activating enzyme UBA6 (PubMed:36758104, PubMed:36758105, PubMed:36758106). Ubiquitinates CASP3, CASP7 and CASP9 and inhibits their caspase activity; also ubiquitinates their procaspases but to a weaker extent (PubMed:15200957, PubMed:36758104, PubMed:36758105, PubMed:36758106). Ubiquitinates pro-apoptotic factors DIABLO/SMAC and HTRA2 (PubMed:15200957, PubMed:36758104, PubMed:36758105, PubMed:36758106). DIABLO/SMAC antagonizes the caspase inhibition activity of BIRC6 by competing for the same binding sites as the caspases (PubMed:18329369, PubMed:36758106). Ubiquitinates the autophagy protein MAP1LC3B; this activity is also inhibited by DIABLO/SMAC (PubMed:36758105). Important regulator for the final stages of cytokinesis (PubMed:18329369). Crucial for normal vesicle targeting to the site of abscission, but also for the integrity of the midbody and the midbody ring, and its striking ubiquitin modification (PubMed:18329369)","subcellular_location":"Golgi apparatus, trans-Golgi network membrane; Endosome; Cytoplasm, cytoskeleton, spindle pole; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Midbody, Midbody ring","url":"https://www.uniprot.org/uniprotkb/Q9NR09/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BIRC6","classification":"Not Classified","n_dependent_lines":392,"n_total_lines":1208,"dependency_fraction":0.32450331125827814},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"COPB2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/BIRC6","total_profiled":1310},"omim":[{"mim_id":"616473","title":"MICRO RNA 558; MIR558","url":"https://www.omim.org/entry/616473"},{"mim_id":"607366","title":"POTASSIUM CHANNEL, SUBFAMILY K, MEMBER 12; KCNK12","url":"https://www.omim.org/entry/607366"},{"mim_id":"605737","title":"BACULOVIRAL IAP REPEAT-CONTAINING PROTEIN 7; BIRC7","url":"https://www.omim.org/entry/605737"},{"mim_id":"605638","title":"BACULOVIRAL IAP REPEAT-CONTAINING PROTEIN 6; BIRC6","url":"https://www.omim.org/entry/605638"},{"mim_id":"600355","title":"NEURONAL APOPTOSIS INHIBITORY PROTEIN; NAIP","url":"https://www.omim.org/entry/600355"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"},{"location":"Vesicles","reliability":"Supported"},{"location":"Mitotic spindle","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/BIRC6"},"hgnc":{"alias_symbol":["BRUCE"],"prev_symbol":[]},"alphafold":{"accession":"Q9NR09","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NR09","model_url":"","pae_url":"","plddt_mean":null},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BIRC6","jax_strain_url":"https://www.jax.org/strain/search?query=BIRC6"},"sequence":{"accession":"Q9NR09","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NR09.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NR09/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NR09"}},"corpus_meta":[{"pmid":"10606224","id":"PMC_10606224","title":"The hypoxic cell: a target for selective cancer therapy--eighteenth Bruce F. 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Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/34729249","citation_count":14,"is_preprint":false},{"pmid":"33177288","id":"PMC_33177288","title":"Depletion of circ-BIRC6, a circular RNA, suppresses non-small cell lung cancer progression by targeting miR-4491.","date":"2020","source":"Bioscience trends","url":"https://pubmed.ncbi.nlm.nih.gov/33177288","citation_count":13,"is_preprint":false},{"pmid":"34542161","id":"PMC_34542161","title":"Silencing circ‑BIRC6 inhibits the proliferation, invasion, migration and epithelial‑mesenchymal transition of bladder cancer cells by targeting the miR‑495‑3p/XBP1 signaling axis.","date":"2021","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/34542161","citation_count":12,"is_preprint":false},{"pmid":"25118708","id":"PMC_25118708","title":"Association of a polymorphism in the BIRC6 gene with pseudoexfoliative glaucoma.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25118708","citation_count":12,"is_preprint":false},{"pmid":"16236253","id":"PMC_16236253","title":"Bruce/apollon promotes hippocampal neuron survival and is downregulated by kainic acid.","date":"2005","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/16236253","citation_count":12,"is_preprint":false},{"pmid":"32697959","id":"PMC_32697959","title":"Bioactivity and cytotoxicity profiling of vincosamide and strictosamide, anthelmintic epimers from Sarcocephalus latifolius (Smith) Bruce leaf.","date":"2020","source":"Journal of ethnopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32697959","citation_count":12,"is_preprint":false},{"pmid":"23343397","id":"PMC_23343397","title":"Redescription and genetic characterization of Hysterothylacium thalassini Bruce, 1990 (Nematoda: Anisakidae) from marine fishes in the South China Sea.","date":"2013","source":"The Journal of parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/23343397","citation_count":12,"is_preprint":false},{"pmid":"34354038","id":"PMC_34354038","title":"BRUCE silencing leads to axonal dystrophy by repressing autophagosome-lysosome fusion in Alzheimer's disease.","date":"2021","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/34354038","citation_count":12,"is_preprint":false},{"pmid":"26683461","id":"PMC_26683461","title":"The UBC Domain Is Required for BRUCE to Promote BRIT1/MCPH1 Function in DSB Signaling and Repair Post Formation of BRUCE-USP8-BRIT1 Complex.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26683461","citation_count":11,"is_preprint":false},{"pmid":"27876095","id":"PMC_27876095","title":"Asymmetric hybridization between non-native winter moth, Operophtera brumata (Lepidoptera: Geometridae), and native Bruce spanworm, Operophtera bruceata, in the Northeastern United States, assessed with novel microsatellites and SNPs.","date":"2016","source":"Bulletin of entomological research","url":"https://pubmed.ncbi.nlm.nih.gov/27876095","citation_count":11,"is_preprint":false},{"pmid":"26191375","id":"PMC_26191375","title":"Knockdown of the Inhibitor of Apoptosis BRUCE Sensitizes Resistant Breast Cancer Cells to Chemotherapeutic Agents.","date":"2015","source":"Journal of cancer science & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/26191375","citation_count":11,"is_preprint":false},{"pmid":"22196277","id":"PMC_22196277","title":"RNA interference-mediated validation of survivin and Apollon/BRUCE as new therapeutic targets for cancer therapy.","date":"2012","source":"Current topics in medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22196277","citation_count":9,"is_preprint":false},{"pmid":"31885751","id":"PMC_31885751","title":"Circ_MDM2_000139, Circ_ATF2_001418, Circ_CDC25C_002079, and Circ_BIRC6_001271 Are Involved in the Functions of XAV939 in Non-Small Cell Lung Cancer.","date":"2019","source":"Canadian respiratory journal","url":"https://pubmed.ncbi.nlm.nih.gov/31885751","citation_count":9,"is_preprint":false},{"pmid":"32851903","id":"PMC_32851903","title":"Reflections on Bruce S. McEwen's contributions to stress neurobiology and so much more.","date":"2020","source":"Stress (Amsterdam, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/32851903","citation_count":8,"is_preprint":false},{"pmid":"35863430","id":"PMC_35863430","title":"A new circular RNA-encoded protein BIRC6-236aa inhibits transmissible gastroenteritis virus (TGEV)-induced mitochondrial dysfunction.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35863430","citation_count":8,"is_preprint":false},{"pmid":"23211188","id":"PMC_23211188","title":"BIRC6 (APOLLON) is down-regulated in acute myeloid leukemia and its knockdown attenuates neutrophil differentiation.","date":"2012","source":"Experimental hematology & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/23211188","citation_count":8,"is_preprint":false},{"pmid":"32139899","id":"PMC_32139899","title":"BRUCE preserves genomic stability in the male germline of mice.","date":"2020","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/32139899","citation_count":8,"is_preprint":false},{"pmid":"38066801","id":"PMC_38066801","title":"Evaluation of BIRC6 Expression in Oral Squamous Cell Carcinoma, Epithelial Dysplasia, Lichen Planus with and without Dysplasia, and Hyperkeratosis.","date":"2023","source":"Diagnostics (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/38066801","citation_count":7,"is_preprint":false},{"pmid":"27614745","id":"PMC_27614745","title":"BRUCE Protein, New Marker for Targeted Therapy of Gastric Carcinoma.","date":"2017","source":"Journal of gastrointestinal cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27614745","citation_count":7,"is_preprint":false},{"pmid":"33317170","id":"PMC_33317170","title":"BIRC6 Is Associated with Vulnerability of Carotid Atherosclerotic Plaque.","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33317170","citation_count":7,"is_preprint":false},{"pmid":"35866869","id":"PMC_35866869","title":"BIRC6 modifies risk of invasive bacterial infection in Kenyan children.","date":"2022","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/35866869","citation_count":6,"is_preprint":false},{"pmid":"36033570","id":"PMC_36033570","title":"Oral Squamous Cell Carcinoma: The Role of BIRC6 Serum Level.","date":"2022","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/36033570","citation_count":5,"is_preprint":false},{"pmid":"38405482","id":"PMC_38405482","title":"BIRC6 Modulates the Protein Stability of Axin to Regulate the Growth, Stemness, and Resistance of Renal Cancer Cells via the β-Catenin Pathway.","date":"2024","source":"ACS omega","url":"https://pubmed.ncbi.nlm.nih.gov/38405482","citation_count":5,"is_preprint":false},{"pmid":"27649954","id":"PMC_27649954","title":"Expression analysis of BRUCE protein in esophageal squamous cell carcinoma.","date":"2016","source":"Annals of diagnostic pathology","url":"https://pubmed.ncbi.nlm.nih.gov/27649954","citation_count":5,"is_preprint":false},{"pmid":"34083041","id":"PMC_34083041","title":"Bruce Nathan Ames - Paradigm shifts inside the cancer research revolution.","date":"2020","source":"Mutation research. Reviews in mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/34083041","citation_count":4,"is_preprint":false},{"pmid":"31827407","id":"PMC_31827407","title":"Nrdp1 increases neuron apoptosis via downregulation of Bruce following intracerebral haemorrhage.","date":"2019","source":"Journal of inflammation (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/31827407","citation_count":4,"is_preprint":false},{"pmid":"31585631","id":"PMC_31585631","title":"A personally guided tour on some of our data with the Ames assay-A tribute to Professor Bruce Ames.","date":"2019","source":"Mutation research. Genetic toxicology and environmental mutagenesis","url":"https://pubmed.ncbi.nlm.nih.gov/31585631","citation_count":4,"is_preprint":false},{"pmid":"25138702","id":"PMC_25138702","title":"Apollon/Bruce is upregulated by Humanin.","date":"2014","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25138702","citation_count":4,"is_preprint":false},{"pmid":"19198067","id":"PMC_19198067","title":"Regulation of apoptosis and cytokinesis by the anti-apoptotic E2/E3 ubiquitin-ligase BRUCE.","date":"2008","source":"Ernst Schering Foundation symposium proceedings","url":"https://pubmed.ncbi.nlm.nih.gov/19198067","citation_count":4,"is_preprint":false},{"pmid":"36455174","id":"PMC_36455174","title":"Exploring the Role of the Inhibitor of Apoptosis BIRC6 in Breast Cancer: A Database Analysis.","date":"2022","source":"JCO clinical cancer informatics","url":"https://pubmed.ncbi.nlm.nih.gov/36455174","citation_count":3,"is_preprint":false},{"pmid":"41350950","id":"PMC_41350950","title":"UBA6 specificity for ubiquitin E2 conjugating enzymes reveals a priority mechanism of BIRC6.","date":"2025","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/41350950","citation_count":3,"is_preprint":false},{"pmid":"33815677","id":"PMC_33815677","title":"BIR repeat-containing ubiquitin conjugating enzyme (BRUCE) regulation of β-catenin signaling in the progression of drug-induced hepatic fibrosis and carcinogenesis.","date":"2021","source":"World journal of hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/33815677","citation_count":3,"is_preprint":false},{"pmid":"30136341","id":"PMC_30136341","title":"Using the SSU, ITS, and Ribosomal DNA Operon Arrangement to Characterize Two Microsporidia Infecting Bruce Spanworm, Operophtera bruceata (Lepidoptera: Geometridae).","date":"2018","source":"The Journal of eukaryotic microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30136341","citation_count":3,"is_preprint":false},{"pmid":"7235620","id":"PMC_7235620","title":"Evidence for the involvement of serotoninergic system in the male-induced ovo-implantation failure (Bruce effect) in mice.","date":"1980","source":"Annales d'endocrinologie","url":"https://pubmed.ncbi.nlm.nih.gov/7235620","citation_count":3,"is_preprint":false},{"pmid":"27446249","id":"PMC_27446249","title":"Nrdp1-mediated degradation of BRUCE decreases cell viability and induces apoptosis in human 786-O renal cell carcinoma cells.","date":"2016","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27446249","citation_count":3,"is_preprint":false},{"pmid":"3229446","id":"PMC_3229446","title":"The male-induced implantation failure (the Bruce effect) in laboratory mice: investigations on luteal failure in pregnancy-blocked females.","date":"1988","source":"Experimental and clinical endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/3229446","citation_count":3,"is_preprint":false},{"pmid":"39705142","id":"PMC_39705142","title":"The differential interactomes of the KRAS splice variants identify BIRC6 as a ubiquitin ligase for KRAS4A.","date":"2024","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/39705142","citation_count":2,"is_preprint":false},{"pmid":"33243730","id":"PMC_33243730","title":"[Effect of small interfering RNA-mediated BIRC6 silencing on apoptosis and autophagy of renal cancer 786-O cells].","date":"2020","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/33243730","citation_count":2,"is_preprint":false},{"pmid":"38046892","id":"PMC_38046892","title":"The Media Coverage of Bruce Willis Reveals Unfamiliarity With Frontotemporal Degeneration.","date":"2023","source":"Innovation in aging","url":"https://pubmed.ncbi.nlm.nih.gov/38046892","citation_count":2,"is_preprint":false},{"pmid":"9527909","id":"PMC_9527909","title":"Volume 8, Number 2 (1997): Kyung-Eui Ro, Carl S. Keener, and Bruce A. McPheron, \"Molecular Phylogenetic Study of the Ranunculaceae: Utility of the Nuclear 26S Ribosomal DNA in Inferring Intrafamilial Relationships,\" pp. 117-127:","date":"1998","source":"Molecular phylogenetics and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/9527909","citation_count":2,"is_preprint":false},{"pmid":"33261220","id":"PMC_33261220","title":"A Wide Frequency Scanning Printed Bruce Array Antenna with Bowtie and Semi-Circular Elements.","date":"2020","source":"Sensors (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/33261220","citation_count":2,"is_preprint":false},{"pmid":"20041659","id":"PMC_20041659","title":"Improved synthesis of (3E,6Z,9Z)-1,3,6,9-nonadecatetraene, attraction inhibitor of bruce spanworm, Operophtera bruceata, to pheromone traps for monitoring winter moth, Operophtera brumata.","date":"2010","source":"Journal of agricultural and food chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20041659","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47917,"output_tokens":7362,"usd":0.12709},"stage2":{"model":"claude-opus-4-6","input_tokens":11058,"output_tokens":3891,"usd":0.228848},"total_usd":0.355938,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"BRUCE functions as a chimeric E2/E3 ubiquitin ligase and inhibitor of apoptosis (IAP) protein localized to the trans-Golgi network. Its BIR domain is required for caspase inhibition and anti-apoptotic activity. BRUCE is antagonized by Smac binding, HtrA2 protease cleavage, and caspase-mediated cleavage. BRUCE ubiquitinates Smac as a substrate.\",\n      \"method\": \"Wild-type and mutant protein overexpression, in vitro ubiquitination assay, co-immunoprecipitation, caspase activity assay, apoptosis induction assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including in vitro ubiquitination, domain mutagenesis, and functional apoptosis assays in single rigorous study\",\n      \"pmids\": [\"15200957\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Nrdp1/FLRF, a RING finger E3 ubiquitin ligase, associates with BRUCE and promotes its ubiquitination and proteasomal degradation. Purified Nrdp1 catalyzes BRUCE ubiquitination in vitro in the presence of E2 UbcH5c. Apoptotic stimuli induce proteasomal degradation of BRUCE, and reducing Nrdp1 by RNAi attenuates BRUCE loss and reduces apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay with purified proteins, RNAi knockdown, proteasome inhibitor experiments\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro ubiquitination with purified Nrdp1, validated by RNAi in vivo\",\n      \"pmids\": [\"14765125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"BRUCE/Apollon associates with precursor and mature forms of Smac, HtrA2, and caspase-9 through regions beyond the IAP-binding motif. BRUCE promotes degradation of Smac and inhibits caspase-9 activity but not caspase-3 activity. Upon apoptotic stimuli, BRUCE is degraded by proteasomes or cleaved by caspases and HtrA2 in a stimulus- and cell type-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation, caspase activity assays, proteasome inhibitor and caspase inhibitor experiments, in vitro binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal biochemical methods identifying substrates and mechanism of caspase inhibition\",\n      \"pmids\": [\"15507451\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"BRUCE is a 528 kDa peripheral membrane protein of the trans-Golgi network required for normal placental development in mice. Complete inactivation causes perinatal lethality due to impaired maturation of the labyrinth layer and reduced spongiotrophoblast in the placenta, without elevated apoptosis in embryonic tissues.\",\n      \"method\": \"Knockout mouse generation and characterization, histological analysis, TUNEL assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with specific in vivo phenotypic readout replicated in multiple studies\",\n      \"pmids\": [\"15485903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Deletion of the C-terminal half of BRUCE (including the UBC domain) in mice causes caspase activation and apoptosis in placenta and yolk sac, leading to embryonic lethality. This apoptosis involves p53 upregulation and nuclear localization, Bax/Bak upregulation, mitochondrial translocation of Bax and caspase-2, cytochrome c and AIF release, and caspase-9/-3 activation. RNAi of p53 rescues cell viability in Bruce-ablated cells by reducing Bax, Bak, Pidd expression and preventing caspase-2/-9/-3 activation.\",\n      \"method\": \"Conditional knockout mouse, RNAi, caspase activity assays, subcellular fractionation, western blot for apoptosis markers\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with RNAi rescue, multiple orthogonal readouts establishing pathway position\",\n      \"pmids\": [\"15640352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Bruce mutant mice (gene trap) show progressive loss of the spongiotrophoblast layer between embryonic days 11.5 and 14.5, resulting in embryonic lethality due to lack of spongiotrophoblast cell proliferation rather than elevated apoptosis.\",\n      \"method\": \"Gene trap mutagenesis, histological analysis, proliferation assays\",\n      \"journal\": \"Genesis (New York, N.Y. : 2000)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific phenotype, consistent with Lotz et al. 2004 but single lab\",\n      \"pmids\": [\"15887267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"During cytokinesis, BRUCE translocates from the vesicular system to the midbody ring and serves as a platform for membrane delivery machinery and mitotic regulators. BRUCE depletion causes defective abscission and cytokinesis-associated apoptosis, blocks vesicular targeting, and disrupts midbody and midbody ring formation. Ubiquitin relocalizes from midbody microtubules to the midbody ring during cytokinesis, and BRUCE depletion disrupts this process.\",\n      \"method\": \"RNAi knockdown in cell culture, live imaging, immunofluorescence, subcellular fractionation\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with specific cellular phenotypes, live imaging of localization change, multiple readouts in high-impact study\",\n      \"pmids\": [\"18329369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In Drosophila oogenesis, the effector caspase Dcp-1 and IAP protein Bruce function together to regulate both starvation-induced autophagy and cell death at germarium and mid-oogenesis checkpoints.\",\n      \"method\": \"Drosophila genetics (mutant analysis), systematic RNAi screen in cultured cells, DNA fragmentation assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in Drosophila with specific in vivo phenotypic readouts\",\n      \"pmids\": [\"18794330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Prostaglandin F2alpha (PGF2alpha) increases BRUCE expression through an NFAT2-dependent pathway, reducing muscle cell death during myogenesis. BRUCE overexpression is sufficient to promote muscle cell survival and myotube growth, establishing a PGF2alpha-NFAT2-BRUCE signaling axis.\",\n      \"method\": \"In vitro myogenesis assay, siRNA knockdown, overexpression constructs, in vivo mouse experiments\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional rescue and KD experiments with pathway placement, single lab\",\n      \"pmids\": [\"18566603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Drosophila BRUCE (dBruce) ubiquitinates the IAP-antagonist Reaper through an unconventional mechanism involving non-lysine ubiquitin acceptor sites. dBruce physically interacts with Reaper dependent on Reaper's IAP-binding (IBM) and GH3 motifs. dBruce loss elevates Reaper protein levels.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay with lysine-deficient Reaper mutants, genetic loss-of-function analysis\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical ubiquitination assay combined with mutagenesis of ubiquitin acceptor sites and genetic validation\",\n      \"pmids\": [\"21886178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"EBV-encoded miRNA miR-BART15-3p directly targets the 3' UTR of BRUCE mRNA at a specific seed-matched site, suppressing BRUCE protein translation and promoting apoptosis in EBV-negative and EBV-infected cells.\",\n      \"method\": \"Luciferase reporter assay with 3'UTR constructs, mutation analysis of seed-match sites, western blot, miRNA inhibitor experiments\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — luciferase reporter with mutagenesis plus functional rescue, single lab\",\n      \"pmids\": [\"23678170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BIRC6 interacts with p53 and facilitates its degradation, promoting hepatocellular carcinogenesis. BIRC6 knockdown activates p53, causes G1/S arrest, and sensitizes hepatoma cells to sorafenib-induced apoptosis, with these effects partially reversed by p53 RNAi.\",\n      \"method\": \"Co-immunoprecipitation, lentiviral shRNA knockdown, flow cytometry, RNAi epistasis, xenograft tumor model\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP plus epistasis experiments, single lab\",\n      \"pmids\": [\"25196217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"BRUCE acts as a scaffold bridging USP8 and BRIT1 in a complex. BRIT1 is K63-ubiquitinated in unstressed cells, and BRUCE promotes USP8-catalyzed deubiquitination of BRIT1, which is prerequisite for BRIT1 recruitment to DSB sites via γ-H2AX binding. Loss of BRUCE impairs BRIT1 deubiquitination, BRIT1 DNA damage foci formation, chromatin relaxation, and homologous recombination repair.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, chromatin immunoprecipitation, HR repair assay, BRUCE-mutant mouse analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, epistasis, multiple orthogonal assays, validated in mouse model\",\n      \"pmids\": [\"25733871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The UBC domain of BRUCE (but not the BIR domain) is required for promoting USP8-mediated deubiquitination of BRIT1 and its recruitment to DSBs. UBC domain mutation or deletion does not disrupt the BRUCE-USP8-BRIT1 complex but impairs BRIT1 deubiquitination, chromatin relaxation, accumulation of MDC1, NBS1, pATM, and RAD51 at DSBs, and homologous recombination repair.\",\n      \"method\": \"Domain deletion/mutation analysis, in vivo ubiquitination assay, co-immunoprecipitation, immunofluorescence, HR repair assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — domain mutagenesis with multiple orthogonal mechanistic readouts\",\n      \"pmids\": [\"26683461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"BIRC6 protein stability is regulated by the Src family kinase Lyn in imatinib-resistant CML cells. Lyn inhibition or knockdown reduces BIRC6 protein stability, promotes formation of an N-terminal BIRC6 fragment, and reduces BIRC6 phosphopeptide levels (phosphorylated at S480, S482, S486), suggesting Lyn regulates BIRC6 phosphorylation and stability. BIRC6 mediates imatinib resistance independently of Mcl-1.\",\n      \"method\": \"Phosphoproteomic analysis, lentiviral shRNA knockdown, kinase inhibitor treatment, caspase activation assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — phosphoproteomic identification plus pharmacological and genetic inhibition, single lab\",\n      \"pmids\": [\"28520795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"BRUCE promotes autophagosome-lysosome fusion by selectively interacting with ATG8 family members GABARAP and GABARAPL1 and with Syntaxin 17, and colocalizes with LAMP2. BRUCE depletion leads to defective autolysosome formation. A non-catalytic N-terminal BRUCE fragment sufficient to bind GABARAP/GABARAPL1 and Syntaxin 17 rescues autolysosome formation, indicating this function is independent of ubiquitin-conjugating activity.\",\n      \"method\": \"RNAi screen, co-immunoprecipitation, immunofluorescence colocalization, domain deletion rescue experiments in Bruce-/- cells, autophagic flux assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — RNAi screen plus reciprocal co-IP, domain deletion rescue in KO cells, multiple orthogonal methods\",\n      \"pmids\": [\"29426817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"UBA6 and BIRC6 cooperate to monoubiquitinate LC3B, targeting it for proteasomal degradation. Knockout of UBA6 or BIRC6 increases autophagic flux under nutrient deprivation and decreases aggresome-like structures and α-synuclein aggregates, demonstrating that UBA6-BIRC6 negatively regulate autophagy by limiting LC3B availability.\",\n      \"method\": \"Whole-genome CRISPR/Cas9 knockout screen, LC3B ubiquitination assay, autophagic flux assays, α-synuclein aggregate quantification in neurons\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genome-wide screen identification, biochemical ubiquitination assay, validated in multiple cellular contexts\",\n      \"pmids\": [\"31692446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BRUCE together with the proteasome activator PA28γ causes proteasomal degradation of LC3-I, inhibiting autophagy. SIP/CacyBP inhibits BRUCE-mediated degradation of LC3-I under normal conditions by blocking Nrdp1 binding to BRUCE. Upon starvation, SIP enhances BRUCE translocation into the recycling endosome and promotes autophagic destruction of BRUCE via optineurin-mediated autophagy.\",\n      \"method\": \"Co-immunoprecipitation, LC3-I degradation assays, RNAi knockdown, subcellular fractionation, autophagic flux assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical and cell biological methods establishing mechanism, single lab\",\n      \"pmids\": [\"31213539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BRUCE depletion promotes autophagy induction by lowering cellular energy levels (elevated AMP/ATP ratio) and activating AMPK (pThr-172), which then activates ULK1 (pSer-555) to initiate autophagy. This is distinct from starvation-induced autophagy, as BRUCE depletion alone does not block autophagosome-lysosome fusion. BRUCE depletion-induced autophagy is coupled to enhanced cisplatin resistance in ovarian cancer cells.\",\n      \"method\": \"AMP/ATP ratio measurement, AMPK and ULK1 phosphorylation assays, autophagy flux assays, ATG16L puncta quantification, lysosomal enzyme activity measurement\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — mechanistic pathway dissection with multiple markers, single lab\",\n      \"pmids\": [\"31091257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BRUCE is recruited to induced DNA damage sites and is required for ATR activation during replication stress. BRUCE depletion inhibits ATR auto-activation, phosphorylation of CHK1 and RPA, and monoubiquitination of FANCD2. BRUCE deficiency results in stalled DNA replication forks and increased firing of new replication origins. Liver-specific BRUCE knockout in mice impairs ATR activation and exacerbates inflammation, fibrosis, and hepatocellular carcinoma.\",\n      \"method\": \"Immunoprecipitation, in vitro kinase assays, DNA fiber assays, conditional liver-specific KO mouse model with DEN-induced HCC\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical readouts of ATR signaling plus in vivo validation in liver-specific KO mouse model\",\n      \"pmids\": [\"30693543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BIRC6 stability is increased by EGF-JNK signaling, which prevents ubiquitination and degradation of BIRC6 mediated by the E3 ubiquitin ligase HECTD1. BIRC6 in turn decreases SMAC expression by inducing the ubiquitin-proteasome pathway, antagonizing apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, western blot, xenograft tumor model\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP plus ubiquitination assay identifying HECTD1 as E3, single lab\",\n      \"pmids\": [\"34729249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BRUCE interacts with Syntaxin 17 (STX17) as shown by co-immunoprecipitation and colocalization. miR-204 targets BRUCE, and knockdown of STX17 or BRUCE inhibits autophagosome-lysosome fusion and impairs axon growth, contributing to axonal dystrophy in an Alzheimer's disease cell model.\",\n      \"method\": \"Co-immunoprecipitation, dual luciferase reporter assay, immunofluorescence, RNAi knockdown\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP confirms BRUCE-STX17 interaction, functional readout with RNAi, single lab\",\n      \"pmids\": [\"34354038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BRUCE deficiency in male germline leads to impaired spermatogonia maintenance, persistent meiotic DNA breaks, impaired homologous synapsis, chromosomal fragmentation and translocations. Bruce-deficient pachytene spermatocytes show unsynapsed regions devoid of ATM and ATR signaling, indicating BRUCE is required for ATM- and ATR-dependent meiotic homologous recombination.\",\n      \"method\": \"Germline-specific conditional KO mouse, FISH, immunofluorescence for synaptonemal complex components, ATM/ATR signaling markers\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean conditional KO with multiple specific cytogenetic and molecular readouts\",\n      \"pmids\": [\"32139899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BRUCE deficiency combined with PKA activates β-catenin through PKA-dependent phosphorylation at Ser-675 (pSer-675-β-catenin) and promotes nuclear β-catenin accumulation. BRUCE and PKA colocalize in hepatocyte cytoplasm, and BRUCE suppresses PKA activity. BRUCE deficiency elevates PKA activity and activates β-catenin signaling during liver disease progression.\",\n      \"method\": \"Co-localization by immunofluorescence, PKA activity assay, western blot for phospho-β-catenin, liver-specific KO mouse model\",\n      \"journal\": \"World journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — subcellular colocalization plus kinase activity assay in KO model, single lab\",\n      \"pmids\": [\"33815677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cryo-EM structures show BIRC6 forms a megadalton crescent-shaped antiparallel dimer with a spacious central cavity containing client protein receptor sites. BIRC6 directly restricts executioner caspase-3 and -7 and ubiquitinates caspase-3, -7, and -9 exclusively via non-canonical E1 UBA6. SMAC binds BIRC6 with multisite, subnanomolar affinity, competitively displacing caspases and obstructing ubiquitination of both apoptotic and autophagy substrates.\",\n      \"method\": \"Cryo-electron microscopy structure determination, in vitro caspase inhibition assays, in vitro ubiquitination assay, ITC binding measurements\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures with functional validation by biochemical assays, replicated across multiple concurrent studies in the same issue\",\n      \"pmids\": [\"36758105\", \"36758106\", \"36758104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BIRC6 forms an antiparallel U-shaped dimer with multiple previously unannotated domains including a ubiquitin-like domain. SMAC/DIABLO binds BIRC6 in the central cavity and outcompetes effector caspase-3 and HtrA2 but not procaspase-9 for BIRC6 binding in cells. BIRC6 also binds LC3 through its LC3-interacting region (LIR). Induction of autophagy promotes autophagic degradation of BIRC6 and caspase-9 but not other effector caspases.\",\n      \"method\": \"Cryo-EM structure, co-immunoprecipitation competition assay, LC3-pull down, LC3 ubiquitylation site mutagenesis, autophagic flux assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure combined with multiple biochemical functional validation experiments\",\n      \"pmids\": [\"38291026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BIRC6 acts as a ubiquitin ligase for KRAS4A, interacting with it on the Golgi apparatus and promoting mono- and di-ubiquitination of KRAS4A at lysines 128 and 147. This interaction is specific to KRAS4A over KRAS4B. Silencing BIRC6 diminishes GTP loading of KRAS4A and suppresses KRAS4A-driven growth stimulation.\",\n      \"method\": \"Proximity labeling interactome mapping, co-immunoprecipitation, ubiquitination site mapping by mass spectrometry, GTP-loading assay, RNAi knockdown\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — proximity labeling plus biochemical ubiquitination site identification and functional consequence demonstrated\",\n      \"pmids\": [\"39705142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BIRC6 modulates Axin protein stability by interacting with Axin and promoting its ubiquitination and degradation, thereby activating β-catenin signaling in renal cell carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, protein turnover assay, siRNA knockdown, xenograft tumor model\",\n      \"journal\": \"ACS omega\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP plus ubiquitination assay with functional β-catenin pathway readouts, single lab\",\n      \"pmids\": [\"38405482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BIRC6 gains priority access to UBA6 over all other UBA6-competent E2s through an exceptionally high-affinity interaction mediated by BIRC6 engagement with the UBA6 ubiquitin fold domain, modulated by the UBA6 Cys-Cap loop. BIRC6 disengages from UBA6 upon receiving ubiquitin via a bespoke thioester switch mechanism to prevent inhibition of UBA6.\",\n      \"method\": \"Cryo-EM structures of BIRC6-UBA6 complexes in different states, biochemical E1-E2 specificity assays, domain mutagenesis\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures plus in vitro biochemical reconstitution with mutagenesis\",\n      \"pmids\": [\"41350950\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BIRC6 (BRUCE/Apollon) is a giant (~528 kDa) antiparallel dimeric protein of the trans-Golgi network that functions as both an IAP (inhibiting caspase-3, -7, and -9 via direct binding and ubiquitination) and a chimeric E2/E3 ubiquitin ligase operating exclusively through the non-canonical E1 UBA6, with its BIR domain mediating caspase suppression and its UBC domain driving ubiquitination of substrates including Smac, LC3B, KRAS4A, and Axin; SMAC binds BIRC6 with subnanomolar affinity to competitively displace caspases and block ubiquitination of both apoptotic and autophagic substrates, while upstream regulators Nrdp1 and Lyn control BIRC6 stability via ubiquitin-proteasomal degradation, and BIRC6 additionally promotes autophagosome-lysosome fusion through direct interactions with GABARAP/GABARAPL1 and Syntaxin 17, regulates DNA double-strand break repair as a scaffold bridging USP8 and BRIT1, and activates ATR signaling to maintain replication fork stability.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BIRC6 (BRUCE/Apollon) is a giant (~528 kDa) chimeric E2/E3 ubiquitin ligase and inhibitor of apoptosis protein that integrates apoptosis suppression, autophagy regulation, DNA damage repair, and cytokinesis through its multidomain architecture. Its BIR domain directly inhibits executioner caspases-3, -7, and -9, while its UBC domain catalyzes ubiquitination of substrates including Smac, caspases, LC3B, KRAS4A, and Axin exclusively via the non-canonical E1 UBA6, with which BIRC6 engages through a high-affinity bespoke thioester switch mechanism [PMID:15200957, PMID:36758105, PMID:31692446, PMID:39705142, PMID:41350950]. Structurally, BIRC6 forms an antiparallel crescent-shaped dimer with a central cavity harboring client receptor sites, where SMAC binds with subnanomolar multisite affinity to competitively displace caspases and block ubiquitination of both apoptotic and autophagic substrates [PMID:36758105, PMID:38291026]. Beyond apoptosis suppression, BIRC6 promotes autophagosome–lysosome fusion through non-catalytic interactions with GABARAP/GABARAPL1 and Syntaxin 17, scaffolds USP8-mediated deubiquitination of BRIT1 to enable homologous recombination repair, activates ATR signaling to maintain replication fork stability, and translocates to the midbody ring during cytokinesis to facilitate abscission [PMID:29426817, PMID:25733871, PMID:30693543, PMID:18329369].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing BIRC6 as a bifunctional IAP and E2/E3 ubiquitin ligase resolved how a single protein could both inhibit caspases and target pro-apoptotic factors like Smac for ubiquitin-dependent degradation.\",\n      \"evidence\": \"In vitro ubiquitination assays, domain mutagenesis, caspase activity assays, and co-immunoprecipitation in mammalian cells\",\n      \"pmids\": [\"15200957\", \"15507451\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E1 enzyme specificity for BIRC6 was unknown\", \"structural basis for dual BIR/UBC function unresolved\", \"full substrate repertoire undefined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of Nrdp1 as an E3 ligase promoting BIRC6 proteasomal degradation during apoptosis established that BIRC6 protein levels are actively regulated upstream, explaining how cells overcome its anti-apoptotic activity.\",\n      \"evidence\": \"Reconstituted in vitro ubiquitination with purified Nrdp1 plus RNAi validation in cells\",\n      \"pmids\": [\"14765125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals triggering Nrdp1-mediated BIRC6 degradation not fully defined\", \"additional upstream E3 ligases not explored\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Knockout mouse studies revealed that BIRC6 is essential for placental development and perinatal viability, demonstrating a critical in vivo developmental function beyond apoptosis suppression.\",\n      \"evidence\": \"Complete and partial knockout mice with histological and TUNEL analysis of placenta\",\n      \"pmids\": [\"15485903\", \"15887267\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether placental defect reflects apoptotic or proliferative role was debated across labs\", \"downstream targets in trophoblast differentiation unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Conditional deletion of the BIRC6 UBC domain proved that its ubiquitin-conjugating activity is required to suppress a p53-dependent mitochondrial apoptosis cascade involving Bax, caspase-2, and caspase-9 in vivo.\",\n      \"evidence\": \"Conditional knockout mouse with p53 RNAi rescue, subcellular fractionation, and caspase activation assays\",\n      \"pmids\": [\"15640352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ubiquitination substrates mediating p53 suppression not identified\", \"whether BIRC6 ubiquitinates p53 directly was unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Discovery that BIRC6 translocates from vesicular membranes to the midbody ring during cytokinesis and is required for abscission revealed an unexpected cell-division function independent of classical IAP activity.\",\n      \"evidence\": \"RNAi knockdown, live imaging, and immunofluorescence in dividing mammalian cells\",\n      \"pmids\": [\"18329369\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrates ubiquitinated at the midbody ring not identified\", \"mechanism of BIRC6 vesicular targeting to midbody unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstration that Drosophila BRUCE ubiquitinates the IAP-antagonist Reaper via non-lysine residues established an unconventional ubiquitination mechanism for IAP-antagonist neutralization.\",\n      \"evidence\": \"In vivo ubiquitination assay with lysine-deficient Reaper mutants and genetic loss-of-function in Drosophila\",\n      \"pmids\": [\"21886178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Non-lysine acceptor site identity (Ser/Thr/Cys) unresolved\", \"conservation of non-lysine ubiquitination for mammalian BIRC6 substrates not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of BIRC6 as a scaffold bridging USP8 and BRIT1 to enable BRIT1 deubiquitination and recruitment to DNA damage sites established a direct role for BIRC6 in homologous recombination repair, with the UBC domain required for promoting USP8 activity.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, in vivo ubiquitination assays, HR repair assays, and domain mutagenesis in BRUCE-mutant cells and mice\",\n      \"pmids\": [\"25733871\", \"26683461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether BIRC6 UBC domain directly ubiquitinates a component of the repair complex or acts allosterically unclear\", \"how BIRC6 is recruited to DSB sites unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Discovery that BIRC6 promotes autophagosome–lysosome fusion through non-catalytic binding of GABARAP/GABARAPL1 and Syntaxin 17 revealed a ubiquitin-independent membrane-tethering function, separating its autophagy-promoting role from its E2/E3 activity.\",\n      \"evidence\": \"RNAi screen, co-immunoprecipitation, domain deletion rescue in Bruce−/− cells, and autophagic flux assays\",\n      \"pmids\": [\"29426817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for selectivity of GABARAP over LC3 subfamily binding unresolved\", \"whether BIRC6 tethers autophagosomes to lysosomes directly or via intermediate complexes not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Genome-wide CRISPR screening identified UBA6 as the exclusive E1 for BIRC6-mediated monoubiquitination and proteasomal degradation of LC3B, establishing UBA6–BIRC6 as a negative regulator of autophagy that limits LC3B availability.\",\n      \"evidence\": \"Whole-genome CRISPR/Cas9 screen, LC3B ubiquitination assay, autophagic flux measurement, and α-synuclein aggregate quantification in neurons\",\n      \"pmids\": [\"31692446\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which LC3B lysine residues are ubiquitinated not fully mapped\", \"whether other ATG8 family members are similarly targeted unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstration that BIRC6 is required for ATR activation, CHK1 phosphorylation, and replication fork stability—with liver-specific knockout exacerbating hepatocarcinogenesis—established BIRC6 as a replication stress response factor distinct from its DSB repair role.\",\n      \"evidence\": \"IP-kinase assays, DNA fiber assays, conditional liver-specific KO mouse with DEN-induced HCC\",\n      \"pmids\": [\"30693543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which BIRC6 activates ATR (direct binding vs. scaffold) not established\", \"relationship between ATR and BRIT1/USP8 repair functions unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Germline-specific knockout proved BIRC6 is essential for meiotic homologous recombination via ATM/ATR signaling at unsynapsed chromosomal regions, extending its DNA repair role to a specialized developmental context.\",\n      \"evidence\": \"Germline-specific conditional KO mouse with immunofluorescence for synaptonemal complex components and ATM/ATR markers\",\n      \"pmids\": [\"32139899\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct interaction partners mediating BIRC6 recruitment to meiotic chromosomes unknown\", \"whether BIRC6 ubiquitinates meiotic repair substrates not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Cryo-EM structures revealing the BIRC6 antiparallel dimer with a central substrate-binding cavity, combined with quantitative binding data showing SMAC's subnanomolar multisite engagement that displaces caspases and blocks ubiquitination, provided the first structural framework integrating BIRC6's IAP and E2/E3 functions.\",\n      \"evidence\": \"Cryo-EM structure determination, ITC binding measurements, in vitro caspase inhibition and ubiquitination assays across three concurrent studies\",\n      \"pmids\": [\"36758105\", \"36758106\", \"36758104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational dynamics during ubiquitin transfer cycle unresolved\", \"how dimer architecture accommodates diverse substrates of vastly different sizes not explained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of KRAS4A as a splice-variant-specific BIRC6 substrate ubiquitinated at K128/K147 on the Golgi linked BIRC6's E3 activity to RAS signaling regulation, revealing a new oncogenic signaling axis.\",\n      \"evidence\": \"Proximity labeling interactome, co-immunoprecipitation, mass spectrometry ubiquitination site mapping, and GTP-loading assay\",\n      \"pmids\": [\"39705142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KRAS4A ubiquitination promotes degradation or alters signaling competence not fully resolved\", \"selectivity mechanism excluding KRAS4B not structurally explained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Cryo-EM structures of the BIRC6–UBA6 complex revealed a bespoke high-affinity engagement mechanism via the UBA6 ubiquitin fold domain and a thioester switch that ejects BIRC6 after ubiquitin loading, explaining how BIRC6 achieves priority E1 access over other UBA6-competent E2 enzymes.\",\n      \"evidence\": \"Cryo-EM structures of BIRC6–UBA6 in multiple states, biochemical E1–E2 specificity assays, and domain mutagenesis\",\n      \"pmids\": [\"41350950\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the thioester switch is regulated by post-translational modifications in vivo unknown\", \"structural basis for how UBA6 selectivity excludes UBE1 completely not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The integration of BIRC6's multiple functions—apoptosis suppression, autophagy regulation, DNA repair, cytokinesis, and KRAS signaling—into a unified regulatory model remains unresolved, particularly how substrate selection is spatiotemporally controlled within the dimer cavity.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No full-length structure with bound substrates other than SMAC\", \"spatial and temporal regulation of BIRC6 dimer across different cellular compartments and cell cycle phases unknown\", \"whether post-translational modifications (e.g., Lyn-mediated phosphorylation) switch BIRC6 between functions not tested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 9, 16, 24, 25, 26, 27]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 12, 13, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 3, 26]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [23, 24]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [12, 19, 22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 2, 4, 24]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [15, 16, 17, 25]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [12, 13, 19, 22]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 16, 24, 28]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [26, 27]}\n    ],\n    \"complexes\": [\n      \"BIRC6 antiparallel homodimer\",\n      \"BIRC6-USP8-BRIT1 complex\",\n      \"UBA6-BIRC6 E1-E2 complex\"\n    ],\n    \"partners\": [\n      \"UBA6\",\n      \"SMAC\",\n      \"USP8\",\n      \"BRIT1\",\n      \"STX17\",\n      \"GABARAP\",\n      \"GABARAPL1\",\n      \"NRDP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}