{"gene":"BBOX1","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2020,"finding":"BBOX1 (gamma-butyrobetaine hydroxylase 1) binds directly to the calcium channel IP3R3 in an enzymatic activity-dependent manner and prevents IP3R3 ubiquitination and proteasomal degradation, thereby maintaining IP3R3-mediated endoplasmic reticulum calcium release that supports mitochondrial respiration and mTORC1-mediated glycolysis in triple-negative breast cancer cells.","method":"siRNA functional screen, co-immunoprecipitation, in vitro enzymatic assays, genetic knockdown/knockout with cell viability and metabolic readouts, in vivo xenograft models","journal":"Cancer discovery","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, enzymatic-dependent binding demonstrated, multiple orthogonal methods, in vitro and in vivo validation","pmids":["32690540"],"is_preprint":false},{"year":2022,"finding":"CRIP1 interacts with BBOX1 and the E3 ligase STUB1, promoting BBOX1 ubiquitination at lysine 240 and proteasomal degradation, leading to downregulation of carnitine metabolism and enhanced cancer stem-like properties in hepatocellular carcinoma.","method":"Co-immunoprecipitation, ubiquitination assays, site-directed mutagenesis (K240), loss-of-function experiments, rescue assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — specific ubiquitination site identified by mutagenesis, reciprocal Co-IP, multiple orthogonal methods in single study","pmids":["35775648"],"is_preprint":false},{"year":2006,"finding":"BBOX1 (gamma-butyrobetaine hydroxylase) is a cytosolic dimeric enzyme of the dioxygenase family responsible for the biosynthesis of L-carnitine; the human gene is located on chromosome 11 and uses three different promoters driving tissue-specific transcription initiation in kidney, liver, and brain, with alternative polyadenylation generating two distinct 3'-UTR forms.","method":"Genomic structure determination, 5'/3'-UTR characterization, promoter activity assays, organ-specific mRNA analysis","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 — direct molecular characterization of gene structure and expression, single lab study","pmids":["17110165"],"is_preprint":false},{"year":2014,"finding":"Homozygous deletion of BBOX1 in a patient completely abolishes de novo carnitine biosynthesis, resulting in mildly decreased free serum carnitine levels but not clinical carnitine deficiency, demonstrating that dietary intake and renal reabsorption are sufficient to maintain carnitine homeostasis in the absence of BBOX1 enzymatic function.","method":"Array comparative genomic hybridization, metabolite profiling (acylcarnitine and free carnitine measurement) in a patient with confirmed homozygous deletion","journal":"BMC medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — natural loss-of-function human case with direct metabolic readout, single subject","pmids":["24986124"],"is_preprint":false}],"current_model":"BBOX1 is a cytosolic dioxygenase enzyme that catalyzes the final step of L-carnitine biosynthesis from gamma-butyrobetaine; in cancer contexts it additionally binds to and stabilizes the IP3R3 calcium channel by preventing its ubiquitin-mediated degradation, sustaining calcium-dependent energy metabolism, and is itself subject to ubiquitination at K240 by the CRIP1/STUB1 E3 ligase complex, linking carnitine metabolism to cancer stem cell signaling."},"narrative":{"teleology":[{"year":2006,"claim":"Establishing the genomic and transcriptional architecture of BBOX1 resolved how a single gene achieves tissue-specific expression in carnitine-synthesizing organs, defining it as a cytosolic dimeric dioxygenase with three alternative promoters and two polyadenylation-derived 3'-UTR forms.","evidence":"Genomic structure determination, promoter activity assays, and organ-specific mRNA analysis in human kidney, liver, and brain","pmids":["17110165"],"confidence":"Medium","gaps":["Functional significance of the two 3'-UTR isoforms for post-transcriptional regulation was not determined","Relative contribution of each promoter to total BBOX1 protein levels in vivo was not quantified"]},{"year":2014,"claim":"A natural human knockout demonstrated that BBOX1 is dispensable for carnitine homeostasis under normal dietary conditions, establishing that de novo biosynthesis is not the dominant source of carnitine in humans.","evidence":"Array CGH-confirmed homozygous BBOX1 deletion in a single patient with metabolite profiling showing mildly reduced but clinically sufficient free carnitine levels","pmids":["24986124"],"confidence":"Medium","gaps":["Based on a single patient; phenotypic spectrum of BBOX1 loss across multiple individuals and dietary contexts is unknown","Whether BBOX1 loss has consequences under metabolic stress or in specific tissues (e.g., heart, skeletal muscle) was not tested"]},{"year":2020,"claim":"Discovery that BBOX1 physically stabilizes the IP3R3 calcium channel in an enzymatic activity-dependent manner revealed a non-canonical function linking carnitine biosynthesis to ER calcium signaling, mitochondrial bioenergetics, and cancer cell viability.","evidence":"Reciprocal co-immunoprecipitation, in vitro enzymatic assays, siRNA/knockout studies with metabolic readouts, and in vivo xenograft models in triple-negative breast cancer","pmids":["32690540"],"confidence":"High","gaps":["Whether BBOX1–IP3R3 interaction occurs in non-cancer tissues with high BBOX1 expression (kidney, liver) is unknown","The structural basis for enzymatic activity-dependent binding to IP3R3 has not been resolved"]},{"year":2022,"claim":"Identification of CRIP1 as an adaptor recruiting the E3 ligase STUB1 to ubiquitinate BBOX1 at K240 defined the degradation pathway controlling BBOX1 protein levels and connected BBOX1 turnover to cancer stemness.","evidence":"Co-immunoprecipitation, ubiquitination assays with K240 mutagenesis, loss-of-function and rescue experiments in hepatocellular carcinoma cells","pmids":["35775648"],"confidence":"High","gaps":["Whether CRIP1/STUB1-mediated degradation of BBOX1 operates in normal tissues or is cancer-specific is unknown","Downstream consequences of BBOX1 K240 ubiquitination on IP3R3 stability were not examined"]},{"year":null,"claim":"It remains unknown how BBOX1's enzymatic activity mechanistically couples to its IP3R3-stabilizing function, whether this non-canonical role operates in normal physiology, and how the CRIP1/STUB1 degradation axis integrates with the IP3R3-protective mechanism.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the BBOX1–IP3R3 complex exists","The relationship between BBOX1 catalytic product (carnitine) and IP3R3 protection is mechanistically unresolved","In vivo physiological relevance of the BBOX1–IP3R3 axis outside cancer has not been tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,2,3]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0]}],"complexes":[],"partners":["ITPR3","CRIP1","STUB1"],"other_free_text":[]},"mechanistic_narrative":"BBOX1 is a cytosolic dimeric dioxygenase that catalyzes the hydroxylation of gamma-butyrobetaine to L-carnitine, constituting the final step of carnitine biosynthesis, with tissue-specific expression driven by three alternative promoters active in kidney, liver, and brain [PMID:17110165]. Homozygous loss of BBOX1 in humans abolishes de novo carnitine synthesis but does not cause clinical carnitine deficiency, indicating that dietary intake and renal reabsorption compensate for the biosynthetic deficit [PMID:24986124]. Beyond its metabolic role, BBOX1 directly binds and stabilizes the IP3R3 calcium channel in an enzymatic activity-dependent manner, preventing its ubiquitin-mediated proteasomal degradation and thereby sustaining ER-to-mitochondria calcium transfer that supports mitochondrial respiration and mTORC1-dependent glycolysis in triple-negative breast cancer cells [PMID:32690540]. BBOX1 itself is targeted for proteasomal degradation through STUB1-mediated ubiquitination at lysine 240, a process promoted by the adaptor CRIP1, linking carnitine metabolism to cancer stem cell properties in hepatocellular carcinoma [PMID:35775648]."},"prefetch_data":{"uniprot":{"accession":"O75936","full_name":"Gamma-butyrobetaine dioxygenase","aliases":["Gamma-butyrobetaine hydroxylase","Gamma-BBH","Gamma-butyrobetaine,2-oxoglutarate dioxygenase"],"length_aa":387,"mass_kda":44.7,"function":"Catalyzes the formation of L-carnitine from gamma-butyrobetaine","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O75936/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BBOX1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BBOX1","total_profiled":1310},"omim":[{"mim_id":"617085","title":"FIN BUD INITIATION FACTOR, ZEBRAFISH, HOMOLOG OF; FIBIN","url":"https://www.omim.org/entry/617085"},{"mim_id":"616225","title":"AUTOPHAGY-RELATED 2A; ATG2A","url":"https://www.omim.org/entry/616225"},{"mim_id":"603312","title":"BUTYROBETAINE-GAMMA,2-OXOGLUTARATE DIOXYGENASE 1; BBOX1","url":"https://www.omim.org/entry/603312"},{"mim_id":"259050","title":"PRIMROSE SYNDROME; PRIMS","url":"https://www.omim.org/entry/259050"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Vesicles","reliability":"Uncertain"},{"location":"Actin filaments","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"kidney","ntpm":436.5},{"tissue":"liver","ntpm":123.3}],"url":"https://www.proteinatlas.org/search/BBOX1"},"hgnc":{"alias_symbol":["gamma-BBH","G-BBH","BBH"],"prev_symbol":["BBOX"]},"alphafold":{"accession":"O75936","domains":[{"cath_id":"3.30.2020.30","chopping":"4-100","consensus_level":"high","plddt":96.1311,"start":4,"end":100},{"cath_id":"3.60.130.10","chopping":"123-385","consensus_level":"high","plddt":95.2495,"start":123,"end":385}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75936","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75936-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75936-F1-predicted_aligned_error_v6.png","plddt_mean":94.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BBOX1","jax_strain_url":"https://www.jax.org/strain/search?query=BBOX1"},"sequence":{"accession":"O75936","fasta_url":"https://rest.uniprot.org/uniprotkb/O75936.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75936/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75936"}},"corpus_meta":[{"pmid":"12974876","id":"PMC_12974876","title":"High mobility group 1 B-box mediates activation of human endothelium.","date":"2003","source":"Journal of internal medicine","url":"https://pubmed.ncbi.nlm.nih.gov/12974876","citation_count":285,"is_preprint":false},{"pmid":"30963689","id":"PMC_30963689","title":"BBX16, a B-box protein, positively regulates light-induced anthocyanin accumulation by activating MYB10 in red pear.","date":"2019","source":"Plant biotechnology journal","url":"https://pubmed.ncbi.nlm.nih.gov/30963689","citation_count":213,"is_preprint":false},{"pmid":"27325768","id":"PMC_27325768","title":"BBX21, an Arabidopsis B-box protein, directly activates HY5 and is targeted by COP1 for 26S proteasome-mediated degradation.","date":"2016","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/27325768","citation_count":205,"is_preprint":false},{"pmid":"23624715","id":"PMC_23624715","title":"The Arabidopsis B-BOX protein BBX25 interacts with HY5, negatively regulating BBX22 expression to suppress seedling photomorphogenesis.","date":"2013","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/23624715","citation_count":200,"is_preprint":false},{"pmid":"17965270","id":"PMC_17965270","title":"SALT TOLERANCE HOMOLOG2, a B-box protein in Arabidopsis that activates transcription and positively regulates light-mediated development.","date":"2007","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/17965270","citation_count":196,"is_preprint":false},{"pmid":"15897199","id":"PMC_15897199","title":"The contribution of RING and B-box 2 domains to retroviral restriction mediated by monkey TRIM5alpha.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15897199","citation_count":151,"is_preprint":false},{"pmid":"11428128","id":"PMC_11428128","title":"Two B or not two B? 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the human gene is located on chromosome 11 and uses three different promoters driving tissue-specific transcription initiation in kidney, liver, and brain, with alternative polyadenylation generating two distinct 3'-UTR forms.\",\n      \"method\": \"Genomic structure determination, 5'/3'-UTR characterization, promoter activity assays, organ-specific mRNA analysis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct molecular characterization of gene structure and expression, single lab study\",\n      \"pmids\": [\"17110165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Homozygous deletion of BBOX1 in a patient completely abolishes de novo carnitine biosynthesis, resulting in mildly decreased free serum carnitine levels but not clinical carnitine deficiency, demonstrating that dietary intake and renal reabsorption are sufficient to maintain carnitine homeostasis in the absence of BBOX1 enzymatic function.\",\n      \"method\": \"Array comparative genomic hybridization, metabolite profiling (acylcarnitine and free carnitine measurement) in a patient with confirmed homozygous deletion\",\n      \"journal\": \"BMC medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — natural loss-of-function human case with direct metabolic readout, single subject\",\n      \"pmids\": [\"24986124\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BBOX1 is a cytosolic dioxygenase enzyme that catalyzes the final step of L-carnitine biosynthesis from gamma-butyrobetaine; in cancer contexts it additionally binds to and stabilizes the IP3R3 calcium channel by preventing its ubiquitin-mediated degradation, sustaining calcium-dependent energy metabolism, and is itself subject to ubiquitination at K240 by the CRIP1/STUB1 E3 ligase complex, linking carnitine metabolism to cancer stem cell signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BBOX1 is a cytosolic dimeric dioxygenase that catalyzes the hydroxylation of gamma-butyrobetaine to L-carnitine, constituting the final step of carnitine biosynthesis, with tissue-specific expression driven by three alternative promoters active in kidney, liver, and brain [PMID:17110165]. Homozygous loss of BBOX1 in humans abolishes de novo carnitine synthesis but does not cause clinical carnitine deficiency, indicating that dietary intake and renal reabsorption compensate for the biosynthetic deficit [PMID:24986124]. Beyond its metabolic role, BBOX1 directly binds and stabilizes the IP3R3 calcium channel in an enzymatic activity-dependent manner, preventing its ubiquitin-mediated proteasomal degradation and thereby sustaining ER-to-mitochondria calcium transfer that supports mitochondrial respiration and mTORC1-dependent glycolysis in triple-negative breast cancer cells [PMID:32690540]. BBOX1 itself is targeted for proteasomal degradation through STUB1-mediated ubiquitination at lysine 240, a process promoted by the adaptor CRIP1, linking carnitine metabolism to cancer stem cell properties in hepatocellular carcinoma [PMID:35775648].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Establishing the genomic and transcriptional architecture of BBOX1 resolved how a single gene achieves tissue-specific expression in carnitine-synthesizing organs, defining it as a cytosolic dimeric dioxygenase with three alternative promoters and two polyadenylation-derived 3'-UTR forms.\",\n      \"evidence\": \"Genomic structure determination, promoter activity assays, and organ-specific mRNA analysis in human kidney, liver, and brain\",\n      \"pmids\": [\"17110165\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional significance of the two 3'-UTR isoforms for post-transcriptional regulation was not determined\",\n        \"Relative contribution of each promoter to total BBOX1 protein levels in vivo was not quantified\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A natural human knockout demonstrated that BBOX1 is dispensable for carnitine homeostasis under normal dietary conditions, establishing that de novo biosynthesis is not the dominant source of carnitine in humans.\",\n      \"evidence\": \"Array CGH-confirmed homozygous BBOX1 deletion in a single patient with metabolite profiling showing mildly reduced but clinically sufficient free carnitine levels\",\n      \"pmids\": [\"24986124\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Based on a single patient; phenotypic spectrum of BBOX1 loss across multiple individuals and dietary contexts is unknown\",\n        \"Whether BBOX1 loss has consequences under metabolic stress or in specific tissues (e.g., heart, skeletal muscle) was not tested\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery that BBOX1 physically stabilizes the IP3R3 calcium channel in an enzymatic activity-dependent manner revealed a non-canonical function linking carnitine biosynthesis to ER calcium signaling, mitochondrial bioenergetics, and cancer cell viability.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, in vitro enzymatic assays, siRNA/knockout studies with metabolic readouts, and in vivo xenograft models in triple-negative breast cancer\",\n      \"pmids\": [\"32690540\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether BBOX1–IP3R3 interaction occurs in non-cancer tissues with high BBOX1 expression (kidney, liver) is unknown\",\n        \"The structural basis for enzymatic activity-dependent binding to IP3R3 has not been resolved\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identification of CRIP1 as an adaptor recruiting the E3 ligase STUB1 to ubiquitinate BBOX1 at K240 defined the degradation pathway controlling BBOX1 protein levels and connected BBOX1 turnover to cancer stemness.\",\n      \"evidence\": \"Co-immunoprecipitation, ubiquitination assays with K240 mutagenesis, loss-of-function and rescue experiments in hepatocellular carcinoma cells\",\n      \"pmids\": [\"35775648\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether CRIP1/STUB1-mediated degradation of BBOX1 operates in normal tissues or is cancer-specific is unknown\",\n        \"Downstream consequences of BBOX1 K240 ubiquitination on IP3R3 stability were not examined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how BBOX1's enzymatic activity mechanistically couples to its IP3R3-stabilizing function, whether this non-canonical role operates in normal physiology, and how the CRIP1/STUB1 degradation axis integrates with the IP3R3-protective mechanism.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural model of the BBOX1–IP3R3 complex exists\",\n        \"The relationship between BBOX1 catalytic product (carnitine) and IP3R3 protection is mechanistically unresolved\",\n        \"In vivo physiological relevance of the BBOX1–IP3R3 axis outside cancer has not been tested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ITPR3\",\n      \"CRIP1\",\n      \"STUB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}