{"gene":"FBXO8","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2007,"finding":"FBXO8 (Fbx8), an F-box protein bearing a Sec7 domain, mediates ubiquitination of the small GTPase Arf6. This ubiquitination does not lead to immediate proteasomal degradation of Arf6 but instead makes Arf6 refractory to activation; Fbx8 knockdown caused hyperactivation of Arf6, and both the F-box and Sec7 domains of Fbx8 are required for suppression of Arf6 activity and cell invasion.","method":"Ubiquitination assay, Fbx8 knockdown, domain-deletion mutants (F-box and Sec7 domain), forced expression in breast tumor cell lines with invasion assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (ubiquitination assay, knockdown, domain mutagenesis, functional invasion assay) in a single focused study establishing the mechanism","pmids":["18094045"],"is_preprint":false},{"year":2010,"finding":"c-Myc binds directly to FBXO8 via its Myc box II (MBII) region. c-Myc overexpression affects FBXO8 cellular translocation and rescues cells from FBXO8-mediated inhibition of ARF6 function, thereby promoting cell invasion.","method":"Large-scale tandem repeat affinity purification to identify FBXO8 as a Myc-binding protein, Co-IP to confirm interaction, domain-mapping (MBII), cellular localization assays, invasion assays","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — affinity purification plus Co-IP interaction validation and functional invasion assay, single lab","pmids":["20848231"],"is_preprint":false},{"year":2016,"finding":"FBXO8 (FBX8) targets mTOR as a substrate for ubiquitin-mediated proteasomal degradation as part of the SCF E3 ubiquitin ligase complex, and this activity is required for FBX8-mediated suppression of CRC cell proliferation and invasion. FBX8 is transcriptionally suppressed by miR-223, which is itself regulated by MEF2A.","method":"Mechanistic studies including ubiquitination/degradation assays, miRNA functional characterization, Co-IP, knockdown/overexpression with proliferation and invasion readouts, clinical validation","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay plus functional rescue experiments establishing mTOR as substrate, single lab","pmids":["27916606"],"is_preprint":false},{"year":2019,"finding":"FBXO8 (FBX8) directly targets GSTP1 for ubiquitin-mediated proteasomal degradation as a component of the SCF E3 ubiquitin ligase. Loss of FBX8 increases GSTP1 protein stability and accelerates colon tumorigenesis in vivo; FBX8 knockout transgenic mice show increased GSTP1 levels.","method":"Co-IP, ubiquitination/proteasome degradation assays, FBX8 knockout transgenic mice, chemical-induced colon tumorigenesis model, cell proliferation/invasion assays","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo knockout model, and ubiquitination assay providing multiple orthogonal lines of evidence in a single study","pmids":["31024008"],"is_preprint":false},{"year":2020,"finding":"FBXO8 directly binds HIF-1α, CDK4, and c-Myc through its Sec7 domain and targets these proteins for ubiquitin-mediated degradation, thereby inhibiting cell cycle progression, proliferation, angiogenesis, and metastasis and promoting metastatic dormancy of CRC cells in the liver.","method":"GST pull-down assay, Co-IP, immunofluorescence to confirm binding; liver metastasis orthotopic mouse model; short-term chemotherapy dormancy experiments; ubiquitin degradation assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pull-down, Co-IP, immunofluorescence, and in vivo model used together; single lab","pmids":["32796813"],"is_preprint":false},{"year":2023,"finding":"The lncRNA FENDRR acts as a molecular scaffold that simultaneously binds both GSTP1 and FBXO8, facilitating FBXO8-mediated ubiquitination and degradation of GSTP1 in CRC cells.","method":"RNA pull-down with mass spectrometry, RNA immunoprecipitation (RIP), Co-IP, immunofluorescence, overexpression/rescue functional assays","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP, Co-IP, and pull-down assays confirming ternary scaffold interaction; single lab with multiple orthogonal methods","pmids":["38144314"],"is_preprint":false}],"current_model":"FBXO8 is an F-box/Sec7 domain-containing component of SCF E3 ubiquitin ligase complexes that uses its Sec7 domain to recruit substrates—including Arf6 (non-degradative ubiquitination that inactivates Arf6), mTOR, GSTP1, HIF-1α, CDK4, and c-Myc—for ubiquitin-mediated regulation; c-Myc binds FBXO8 via its MBII domain to block FBXO8-dependent suppression of ARF6 and invasion, while the lncRNA FENDRR can scaffold FBXO8 with GSTP1 to enhance its degradation."},"narrative":{"mechanistic_narrative":"FBXO8 is an F-box/Sec7 domain-containing substrate-recognition subunit of SCF E3 ubiquitin ligase complexes that acts as a tumor suppressor by directing ubiquitination of distinct substrates, with effects ranging from non-degradative inactivation to proteasomal degradation [PMID:18094045, PMID:27916606]. Its founding activity is ubiquitination of the small GTPase Arf6: rather than triggering Arf6 degradation, this modification renders Arf6 refractory to activation, and both the F-box and Sec7 domains are required to suppress Arf6 activity and cell invasion [PMID:18094045]. Through its Sec7 domain, FBXO8 also engages a panel of pro-proliferative substrates—mTOR, HIF-1α, CDK4, and c-Myc—targeting them for ubiquitin-mediated proteasomal degradation and thereby restraining cell cycle progression, proliferation, angiogenesis, and metastasis while promoting metastatic dormancy of colorectal cancer cells [PMID:27916606, PMID:32796813]. FBXO8 likewise degrades GSTP1, and its loss stabilizes GSTP1 and accelerates colon tumorigenesis in knockout mice [PMID:31024008]. This activity is itself regulated at multiple levels: c-Myc binds FBXO8 via its MBII domain to block FBXO8-dependent suppression of Arf6 and invasion [PMID:20848231], the lncRNA FENDRR scaffolds FBXO8 with GSTP1 to enhance GSTP1 degradation [PMID:38144314], and FBXO8 expression is suppressed by miR-223 downstream of MEF2A [PMID:27916606].","teleology":[{"year":2007,"claim":"Established FBXO8 as a functional E3 ligase component by showing it ubiquitinates Arf6 in a non-degradative manner that blocks Arf6 activation and cell invasion, defining both an enzymatic activity and a domain requirement.","evidence":"Ubiquitination assay, knockdown, F-box and Sec7 domain-deletion mutants, and invasion assays in breast tumor cell lines","pmids":["18094045"],"confidence":"High","gaps":["Cullin/Skp1 scaffold composition of the FBXO8-containing SCF complex not biochemically defined","molecular basis for non-degradative outcome on Arf6 versus degradation of other substrates not resolved"]},{"year":2010,"claim":"Identified c-Myc as a direct FBXO8 binding partner via its MBII domain that antagonizes FBXO8 function, showing FBXO8 activity is regulated by protein-protein interaction and subcellular relocalization.","evidence":"Tandem affinity purification, Co-IP, MBII domain mapping, localization and invasion assays","pmids":["20848231"],"confidence":"Medium","gaps":["mechanism by which c-Myc binding alters FBXO8 localization unknown","whether c-Myc is also a substrate not addressed in this study"]},{"year":2016,"claim":"Extended FBXO8 to degradative ubiquitination by identifying mTOR as a substrate and placed FBXO8 in a regulatory axis where miR-223/MEF2A suppress its expression in colorectal cancer.","evidence":"Ubiquitination/degradation assays, miRNA functional characterization, Co-IP, knockdown/overexpression with proliferation and invasion readouts, clinical validation","pmids":["27916606"],"confidence":"Medium","gaps":["direct degron/recognition motif on mTOR not mapped","single-lab data without independent replication"]},{"year":2019,"claim":"Provided in vivo tumor-suppressor evidence by showing FBXO8 degrades GSTP1 and that FBXO8 loss stabilizes GSTP1 and accelerates colon tumorigenesis in knockout mice.","evidence":"Reciprocal Co-IP, ubiquitination/degradation assays, FBX8 knockout mice, chemical-induced colon tumorigenesis model","pmids":["31024008"],"confidence":"High","gaps":["contribution of GSTP1 stabilization relative to other substrates in the tumorigenesis phenotype not separated"]},{"year":2020,"claim":"Broadened the FBXO8 substrate repertoire to HIF-1α, CDK4, and c-Myc through Sec7-domain binding, linking FBXO8 to cell cycle, angiogenesis, metastasis, and metastatic dormancy.","evidence":"GST pull-down, Co-IP, immunofluorescence, orthotopic liver metastasis mouse model, chemotherapy dormancy experiments, ubiquitination assays","pmids":["32796813"],"confidence":"Medium","gaps":["specificity of a single Sec7 domain for multiple structurally distinct substrates not mechanistically explained","single-lab in vivo findings"]},{"year":2023,"claim":"Identified a lncRNA-based regulatory layer in which FENDRR scaffolds FBXO8 with GSTP1 to enhance GSTP1 ubiquitination and degradation.","evidence":"RNA pull-down with mass spectrometry, RIP, Co-IP, immunofluorescence, rescue functional assays","pmids":["38144314"],"confidence":"Medium","gaps":["whether FENDRR similarly modulates other FBXO8 substrates not tested","single-lab ternary-complex evidence"]},{"year":null,"claim":"The structural and biochemical basis for how a single Sec7-domain F-box protein selects such diverse substrates—and what determines degradative versus non-degradative ubiquitination outcomes—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["no structure of FBXO8 or its substrate-bound complexes","SCF complex composition not biochemically reconstituted","rules governing degradative vs non-degradative ubiquitination unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,3,4]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,3]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,3,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,3,4]}],"complexes":["SCF E3 ubiquitin ligase complex"],"partners":["ARF6","MYC","MTOR","GSTP1","HIF1A","CDK4","FENDRR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NRD0","full_name":"F-box only protein 8","aliases":["F-box/SEC7 protein FBS"],"length_aa":319,"mass_kda":37.1,"function":"May promote guanine-nucleotide exchange on an ARF. Promotes the activation of ARF through replacement of GDP with GTP (Potential)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9NRD0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FBXO8","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FBXO8","total_profiled":1310},"omim":[{"mim_id":"606586","title":"RETINOIC ACID-INDUCED 14; RAI14","url":"https://www.omim.org/entry/606586"},{"mim_id":"605649","title":"F-BOX ONLY PROTEIN 8; FBXO8","url":"https://www.omim.org/entry/605649"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FBXO8"},"hgnc":{"alias_symbol":["FBX8","FBS"],"prev_symbol":[]},"alphafold":{"accession":"Q9NRD0","domains":[{"cath_id":"1.10.1000.11","chopping":"203-313","consensus_level":"high","plddt":90.5005,"start":203,"end":313}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRD0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRD0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NRD0-F1-predicted_aligned_error_v6.png","plddt_mean":81.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FBXO8","jax_strain_url":"https://www.jax.org/strain/search?query=FBXO8"},"sequence":{"accession":"Q9NRD0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NRD0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NRD0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NRD0"}},"corpus_meta":[{"pmid":"27916606","id":"PMC_27916606","title":"FBX8 is a metastasis suppressor downstream of miR-223 and targeting mTOR for degradation in colorectal carcinoma.","date":"2016","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/27916606","citation_count":37,"is_preprint":false},{"pmid":"31024008","id":"PMC_31024008","title":"FBX8 degrades GSTP1 through ubiquitination to suppress colorectal cancer progression.","date":"2019","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/31024008","citation_count":32,"is_preprint":false},{"pmid":"32796813","id":"PMC_32796813","title":"FBX8 promotes metastatic dormancy of colorectal cancer in liver.","date":"2020","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/32796813","citation_count":31,"is_preprint":false},{"pmid":"18094045","id":"PMC_18094045","title":"Fbx8 makes Arf6 refractory to function via ubiquitination.","date":"2007","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/18094045","citation_count":27,"is_preprint":false},{"pmid":"25801334","id":"PMC_25801334","title":"Significance of FBX8 in progression of gastric cancer.","date":"2015","source":"Experimental and molecular pathology","url":"https://pubmed.ncbi.nlm.nih.gov/25801334","citation_count":20,"is_preprint":false},{"pmid":"20848231","id":"PMC_20848231","title":"c-Myc stimulates cell invasion by inhibiting FBX8 function.","date":"2010","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/20848231","citation_count":16,"is_preprint":false},{"pmid":"24038848","id":"PMC_24038848","title":"Bilaterally cleft lip and bilateral thumb polydactyly with triphalangeal component in a patient with two de novo deletions of HSA 4q32 and 4q34 involving PDGFC, GRIA2, and FBXO8 genes.","date":"2013","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/24038848","citation_count":7,"is_preprint":false},{"pmid":"38144314","id":"PMC_38144314","title":"The lncRNA FENDRR inhibits colorectal cancer progression via interacting with and triggering GSTP1 ubiquitination by FBX8.","date":"2023","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/38144314","citation_count":7,"is_preprint":false},{"pmid":"41953918","id":"PMC_41953918","title":"Posttranscriptional Repression of FBXW7 and FBXO8 by microRNA-223 Regulates Ubiquitin-dependent Proteostasis in Periodontal Disease.","date":"2026","source":"Contemporary clinical dentistry","url":"https://pubmed.ncbi.nlm.nih.gov/41953918","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6659,"output_tokens":1680,"usd":0.022589,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8448,"output_tokens":2522,"usd":0.052645,"stage2_stop_reason":"end_turn"},"total_usd":0.075234,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"FBXO8 (Fbx8), an F-box protein bearing a Sec7 domain, mediates ubiquitination of the small GTPase Arf6. This ubiquitination does not lead to immediate proteasomal degradation of Arf6 but instead makes Arf6 refractory to activation; Fbx8 knockdown caused hyperactivation of Arf6, and both the F-box and Sec7 domains of Fbx8 are required for suppression of Arf6 activity and cell invasion.\",\n      \"method\": \"Ubiquitination assay, Fbx8 knockdown, domain-deletion mutants (F-box and Sec7 domain), forced expression in breast tumor cell lines with invasion assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (ubiquitination assay, knockdown, domain mutagenesis, functional invasion assay) in a single focused study establishing the mechanism\",\n      \"pmids\": [\"18094045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"c-Myc binds directly to FBXO8 via its Myc box II (MBII) region. c-Myc overexpression affects FBXO8 cellular translocation and rescues cells from FBXO8-mediated inhibition of ARF6 function, thereby promoting cell invasion.\",\n      \"method\": \"Large-scale tandem repeat affinity purification to identify FBXO8 as a Myc-binding protein, Co-IP to confirm interaction, domain-mapping (MBII), cellular localization assays, invasion assays\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — affinity purification plus Co-IP interaction validation and functional invasion assay, single lab\",\n      \"pmids\": [\"20848231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FBXO8 (FBX8) targets mTOR as a substrate for ubiquitin-mediated proteasomal degradation as part of the SCF E3 ubiquitin ligase complex, and this activity is required for FBX8-mediated suppression of CRC cell proliferation and invasion. FBX8 is transcriptionally suppressed by miR-223, which is itself regulated by MEF2A.\",\n      \"method\": \"Mechanistic studies including ubiquitination/degradation assays, miRNA functional characterization, Co-IP, knockdown/overexpression with proliferation and invasion readouts, clinical validation\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay plus functional rescue experiments establishing mTOR as substrate, single lab\",\n      \"pmids\": [\"27916606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FBXO8 (FBX8) directly targets GSTP1 for ubiquitin-mediated proteasomal degradation as a component of the SCF E3 ubiquitin ligase. Loss of FBX8 increases GSTP1 protein stability and accelerates colon tumorigenesis in vivo; FBX8 knockout transgenic mice show increased GSTP1 levels.\",\n      \"method\": \"Co-IP, ubiquitination/proteasome degradation assays, FBX8 knockout transgenic mice, chemical-induced colon tumorigenesis model, cell proliferation/invasion assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo knockout model, and ubiquitination assay providing multiple orthogonal lines of evidence in a single study\",\n      \"pmids\": [\"31024008\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FBXO8 directly binds HIF-1α, CDK4, and c-Myc through its Sec7 domain and targets these proteins for ubiquitin-mediated degradation, thereby inhibiting cell cycle progression, proliferation, angiogenesis, and metastasis and promoting metastatic dormancy of CRC cells in the liver.\",\n      \"method\": \"GST pull-down assay, Co-IP, immunofluorescence to confirm binding; liver metastasis orthotopic mouse model; short-term chemotherapy dormancy experiments; ubiquitin degradation assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST pull-down, Co-IP, immunofluorescence, and in vivo model used together; single lab\",\n      \"pmids\": [\"32796813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The lncRNA FENDRR acts as a molecular scaffold that simultaneously binds both GSTP1 and FBXO8, facilitating FBXO8-mediated ubiquitination and degradation of GSTP1 in CRC cells.\",\n      \"method\": \"RNA pull-down with mass spectrometry, RNA immunoprecipitation (RIP), Co-IP, immunofluorescence, overexpression/rescue functional assays\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP, Co-IP, and pull-down assays confirming ternary scaffold interaction; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"38144314\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FBXO8 is an F-box/Sec7 domain-containing component of SCF E3 ubiquitin ligase complexes that uses its Sec7 domain to recruit substrates—including Arf6 (non-degradative ubiquitination that inactivates Arf6), mTOR, GSTP1, HIF-1α, CDK4, and c-Myc—for ubiquitin-mediated regulation; c-Myc binds FBXO8 via its MBII domain to block FBXO8-dependent suppression of ARF6 and invasion, while the lncRNA FENDRR can scaffold FBXO8 with GSTP1 to enhance its degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FBXO8 is an F-box/Sec7 domain-containing substrate-recognition subunit of SCF E3 ubiquitin ligase complexes that acts as a tumor suppressor by directing ubiquitination of distinct substrates, with effects ranging from non-degradative inactivation to proteasomal degradation [#0, #2]. Its founding activity is ubiquitination of the small GTPase Arf6: rather than triggering Arf6 degradation, this modification renders Arf6 refractory to activation, and both the F-box and Sec7 domains are required to suppress Arf6 activity and cell invasion [#0]. Through its Sec7 domain, FBXO8 also engages a panel of pro-proliferative substrates—mTOR, HIF-1\\u03b1, CDK4, and c-Myc—targeting them for ubiquitin-mediated proteasomal degradation and thereby restraining cell cycle progression, proliferation, angiogenesis, and metastasis while promoting metastatic dormancy of colorectal cancer cells [#2, #4]. FBXO8 likewise degrades GSTP1, and its loss stabilizes GSTP1 and accelerates colon tumorigenesis in knockout mice [#3]. This activity is itself regulated at multiple levels: c-Myc binds FBXO8 via its MBII domain to block FBXO8-dependent suppression of Arf6 and invasion [#1], the lncRNA FENDRR scaffolds FBXO8 with GSTP1 to enhance GSTP1 degradation [#5], and FBXO8 expression is suppressed by miR-223 downstream of MEF2A [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established FBXO8 as a functional E3 ligase component by showing it ubiquitinates Arf6 in a non-degradative manner that blocks Arf6 activation and cell invasion, defining both an enzymatic activity and a domain requirement.\",\n      \"evidence\": \"Ubiquitination assay, knockdown, F-box and Sec7 domain-deletion mutants, and invasion assays in breast tumor cell lines\",\n      \"pmids\": [\"18094045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cullin/Skp1 scaffold composition of the FBXO8-containing SCF complex not biochemically defined\", \"molecular basis for non-degradative outcome on Arf6 versus degradation of other substrates not resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified c-Myc as a direct FBXO8 binding partner via its MBII domain that antagonizes FBXO8 function, showing FBXO8 activity is regulated by protein-protein interaction and subcellular relocalization.\",\n      \"evidence\": \"Tandem affinity purification, Co-IP, MBII domain mapping, localization and invasion assays\",\n      \"pmids\": [\"20848231\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"mechanism by which c-Myc binding alters FBXO8 localization unknown\", \"whether c-Myc is also a substrate not addressed in this study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended FBXO8 to degradative ubiquitination by identifying mTOR as a substrate and placed FBXO8 in a regulatory axis where miR-223/MEF2A suppress its expression in colorectal cancer.\",\n      \"evidence\": \"Ubiquitination/degradation assays, miRNA functional characterization, Co-IP, knockdown/overexpression with proliferation and invasion readouts, clinical validation\",\n      \"pmids\": [\"27916606\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"direct degron/recognition motif on mTOR not mapped\", \"single-lab data without independent replication\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided in vivo tumor-suppressor evidence by showing FBXO8 degrades GSTP1 and that FBXO8 loss stabilizes GSTP1 and accelerates colon tumorigenesis in knockout mice.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination/degradation assays, FBX8 knockout mice, chemical-induced colon tumorigenesis model\",\n      \"pmids\": [\"31024008\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"contribution of GSTP1 stabilization relative to other substrates in the tumorigenesis phenotype not separated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Broadened the FBXO8 substrate repertoire to HIF-1\\u03b1, CDK4, and c-Myc through Sec7-domain binding, linking FBXO8 to cell cycle, angiogenesis, metastasis, and metastatic dormancy.\",\n      \"evidence\": \"GST pull-down, Co-IP, immunofluorescence, orthotopic liver metastasis mouse model, chemotherapy dormancy experiments, ubiquitination assays\",\n      \"pmids\": [\"32796813\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"specificity of a single Sec7 domain for multiple structurally distinct substrates not mechanistically explained\", \"single-lab in vivo findings\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified a lncRNA-based regulatory layer in which FENDRR scaffolds FBXO8 with GSTP1 to enhance GSTP1 ubiquitination and degradation.\",\n      \"evidence\": \"RNA pull-down with mass spectrometry, RIP, Co-IP, immunofluorescence, rescue functional assays\",\n      \"pmids\": [\"38144314\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"whether FENDRR similarly modulates other FBXO8 substrates not tested\", \"single-lab ternary-complex evidence\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural and biochemical basis for how a single Sec7-domain F-box protein selects such diverse substrates—and what determines degradative versus non-degradative ubiquitination outcomes—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"no structure of FBXO8 or its substrate-bound complexes\", \"SCF complex composition not biochemically reconstituted\", \"rules governing degradative vs non-degradative ubiquitination unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 3, 4]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 3, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3, 4]}\n    ],\n    \"complexes\": [\"SCF E3 ubiquitin ligase complex\"],\n    \"partners\": [\"ARF6\", \"MYC\", \"MTOR\", \"GSTP1\", \"HIF1A\", \"CDK4\", \"FENDRR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}