{"gene":"CAND2","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":1999,"finding":"TIP120B (CAND2) is a muscle-specific protein that binds TBP (TATA-binding protein) as shown by GST pull-down assay using GST-fused TBP with nuclear extract, and is expressed specifically in muscle tissues with transient upregulation during embryogenesis.","method":"GST pull-down assay, Northern blot, Western blot","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct pull-down demonstrating TBP binding, confirmed by tissue-specific expression data; single lab, two orthogonal methods","pmids":["10441524"],"is_preprint":false},{"year":2003,"finding":"KIAA10 (a HECT domain E3 ubiquitin ligase) targets TIP120B (CAND2) for proteolytic degradation: the N-terminal domain of KIAA10 binds TIP120B, and KIAA10 ubiquitinates TIP120B as a specific substrate in vitro and in C2C12 myoblasts, but not TIP120A (CAND1). This substrate specificity is tissue-restricted, as it occurs in muscle cells but not Cos-1 cells.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, co-transfection studies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro ubiquitination assay plus co-transfection and binding studies in relevant cell lines, with clear substrate specificity discrimination between CAND2 and CAND1","pmids":["12692129"],"is_preprint":false},{"year":2007,"finding":"TIP120B (CAND2) suppresses SCF (Skp1-CUL1-F-box protein) ubiquitin ligase-dependent ubiquitination of myogenin by binding CUL1 and disrupting the SCF-myogenin complex, thereby stabilizing myogenin and accelerating myogenic differentiation of C2C12 cells. CUL1 siRNA knockdown independently inhibited myogenin ubiquitination, confirming SCF involvement. CAND2 was associated with the SCF complex in cells, and myogenin was also found in this complex.","method":"Co-immunoprecipitation, siRNA knockdown, ubiquitination assay, overexpression in C2C12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, siRNA epistasis, and ubiquitination assay with multiple orthogonal approaches in a single study","pmids":["17242400"],"is_preprint":false},{"year":2021,"finding":"Cand2 is translationally upregulated downstream of mTORC1 signaling in cardiomyocytes, and Cand2 deletion protects against pathological cardiac remodeling. Mechanistically, Cand2 links mTOR signaling to pathological cell growth by increasing GRK5 protein expression.","method":"Genome-wide ribosome sequencing (ribosome profiling), Cand2 knockout mouse model, protein expression analysis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ribosome profiling plus genetic KO with defined phenotypic readout and GRK5 protein-level measurement; single lab","pmids":["34605609"],"is_preprint":false},{"year":2025,"finding":"CAND2 functions as an F-box protein exchange factor for SCF (CUL1-based) ubiquitin ligases, promoting SCF-mediated protein degradation. CAND2 binds CUL1 with structure and affinity comparable to CAND1, but exhibits lower efficiency in exchanging F-box proteins due to a significantly higher KM for SCF disassembly, attributed to less favorable conformations of the CAND2·SCF exchange intermediate complex.","method":"Quantitative binding assays, real-time kinetic measurements, structural analysis, F-box protein exchange assays in human cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with kinetic measurements, structural characterization, and cellular functional assays; single lab but multiple orthogonal methods","pmids":["40011427"],"is_preprint":false},{"year":2026,"finding":"CAND2, in addition to its role in CRL1, functions as a bona fide CRL4 exchange factor: CAND2 promotes CRL4-mediated protein degradation and enhances dynamic exchange of DDB1·DCAF substrate receptor modules. Unlike its reduced efficiency relative to CAND1 in CRL1 disassembly, CAND2 exhibits similar kinetic parameters and comparable exchange efficiency to CAND1 across most CRL4 complexes.","method":"Genetic perturbation, real-time kinetic analyses, quantitative interaction proteomics","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — kinetic measurements, quantitative proteomics, and genetic perturbation with multiple orthogonal methods in a single rigorous study","pmids":["41864201"],"is_preprint":false}],"current_model":"CAND2 (TIP120B) is a muscle-enriched paralog of CAND1 that acts as an F-box protein exchange factor for both CRL1 (SCF) and CRL4 ubiquitin ligase complexes, promoting substrate receptor cycling; it binds CUL1 with affinity comparable to CAND1 but exchanges F-box proteins less efficiently due to a higher KM for SCF disassembly, while showing comparable efficiency to CAND1 on CRL4; in muscle, CAND2 stabilizes the pro-differentiation transcription factor myogenin by disrupting the SCF–myogenin complex and suppressing myogenin ubiquitination, thereby accelerating myogenesis; CAND2 is itself a substrate of the HECT E3 ligase KIAA10 specifically in muscle cells; and in the heart CAND2 is translationally upregulated by mTORC1 and promotes pathological cardiac remodeling by increasing GRK5 protein levels."},"narrative":{"mechanistic_narrative":"CAND2 (TIP120B) is a muscle-enriched regulator of cullin-RING ubiquitin ligase (CRL) activity that controls substrate receptor cycling and, through it, the stability of myogenic and cardiac signaling factors [PMID:17242400, PMID:40011427]. It functions as an F-box protein exchange factor for CUL1-based SCF ligases, binding CUL1 with structure and affinity comparable to CAND1 but disassembling SCF less efficiently owing to a higher KM for the exchange intermediate [PMID:40011427]; it acts in parallel as a bona fide CRL4 exchange factor, enhancing dynamic exchange of DDB1·DCAF substrate receptor modules with kinetics comparable to CAND1 [PMID:41864201]. In muscle, CAND2 binds CUL1 and disrupts the SCF–myogenin complex, suppressing myogenin ubiquitination to stabilize this transcription factor and accelerate myogenic differentiation of C2C12 cells [PMID:17242400]. CAND2 is itself a tissue-restricted substrate of the HECT E3 ligase KIAA10, which binds and ubiquitinates CAND2 (but not CAND1) specifically in muscle cells [PMID:12692129]. In the heart, CAND2 is translationally upregulated downstream of mTORC1 and drives pathological cardiac remodeling by increasing GRK5 protein levels, with Cand2 deletion conferring protection [PMID:34605609]. An early observation that CAND2 binds TBP and is muscle-specific established its tissue restriction [PMID:10441524]; how this interaction integrates with its CRL exchange function has not been characterized in the available corpus.","teleology":[{"year":1999,"claim":"Established CAND2 as a distinct, muscle-specific protein and gave the first candidate interaction, linking it to the basal transcription machinery via TBP.","evidence":"GST pull-down with GST-TBP against nuclear extract, plus Northern/Western tissue profiling","pmids":["10441524"],"confidence":"Medium","gaps":["No functional consequence of TBP binding shown","Interaction not reconciled with later CRL exchange role","Single-lab pull-down without reciprocal validation"]},{"year":2003,"claim":"Showed CAND2 is regulated by targeted proteolysis in a tissue-restricted manner, distinguishing it from CAND1 and indicating muscle-specific control of CAND2 levels.","evidence":"Co-IP, in vitro ubiquitination, and co-transfection in C2C12 myoblasts versus Cos-1 cells with KIAA10","pmids":["12692129"],"confidence":"High","gaps":["Physiological signal triggering CAND2 degradation unknown","Consequences of CAND2 turnover for CRL function not addressed"]},{"year":2007,"claim":"Defined a mechanistic role for CAND2 in myogenesis by showing it protects a pro-differentiation transcription factor from SCF-mediated degradation.","evidence":"Reciprocal Co-IP, CUL1 siRNA epistasis, and myogenin ubiquitination assays in C2C12 cells","pmids":["17242400"],"confidence":"High","gaps":["Whether stabilization reflects general exchange-factor activity or a dedicated myogenin mechanism unresolved","Identity of the relevant F-box receptor for myogenin not defined"]},{"year":2021,"claim":"Extended CAND2 into cardiac pathophysiology, placing it downstream of mTORC1 as a driver of pathological growth via GRK5.","evidence":"Ribosome profiling and Cand2 knockout mouse with GRK5 protein-level readout","pmids":["34605609"],"confidence":"Medium","gaps":["Molecular route from CAND2 to elevated GRK5 not defined","Whether CRL exchange activity mediates the GRK5 effect untested"]},{"year":2025,"claim":"Provided the biochemical mechanism for CAND2 as an SCF F-box exchange factor and quantified why it is a weaker disassembler than CAND1.","evidence":"Quantitative binding, real-time kinetics, structural analysis, and cellular F-box exchange assays","pmids":["40011427"],"confidence":"High","gaps":["Functional significance of reduced SCF exchange efficiency in vivo unclear","Tissue-specific consequences of the kinetic difference not addressed"]},{"year":2026,"claim":"Broadened CAND2's exchange-factor function to CRL4, showing it cycles DDB1·DCAF modules with CAND1-like efficiency, unlike its weaker CRL1 activity.","evidence":"Real-time kinetics, quantitative interaction proteomics, and genetic perturbation","pmids":["41864201"],"confidence":"High","gaps":["Specific CRL4 substrates regulated by CAND2 not enumerated","Why CAND2 is CRL4-efficient but CRL1-impaired structurally unresolved"]},{"year":null,"claim":"How CAND2's CRL exchange-factor activity, its TBP binding, and its tissue-specific roles in myogenesis and cardiac remodeling are mechanistically connected remains open.","evidence":"No single study integrates the biochemical exchange function with the muscle/heart phenotypes","pmids":[],"confidence":"Medium","gaps":["No demonstration that GRK5 or myogenin regulation requires CAND2 exchange activity","TBP interaction unexplained in CRL context"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,4,5]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2]}],"complexes":["SCF (CRL1)","CRL4 (DDB1-DCAF)"],"partners":["CUL1","DDB1","KIAA10","TBP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75155","full_name":"Cullin-associated NEDD8-dissociated protein 2","aliases":["Cullin-associated and neddylation-dissociated protein 2","Epididymis tissue protein Li 169","TBP-interacting protein of 120 kDa B","TBP-interacting protein 120B","p120 CAND2"],"length_aa":1236,"mass_kda":135.3,"function":"Probable assembly factor of SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complexes that promotes the exchange of the substrate-recognition F-box subunit in SCF complexes, thereby playing a key role in the cellular repertoire of SCF complexes","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/O75155/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CAND2","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CAND2","total_profiled":1310},"omim":[{"mim_id":"610403","title":"CULLIN-ASSOCIATED NEDDYLATION-DISSOCIATED 2; CAND2","url":"https://www.omim.org/entry/610403"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear bodies","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"skeletal muscle","ntpm":125.9},{"tissue":"tongue","ntpm":33.7}],"url":"https://www.proteinatlas.org/search/CAND2"},"hgnc":{"alias_symbol":["TIP120B","KIAA0667","Tp120b"],"prev_symbol":[]},"alphafold":{"accession":"O75155","domains":[{"cath_id":"-","chopping":"521-624","consensus_level":"medium","plddt":92.7409,"start":521,"end":624},{"cath_id":"-","chopping":"999-1106","consensus_level":"medium","plddt":90.1461,"start":999,"end":1106}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75155","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75155-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75155-F1-predicted_aligned_error_v6.png","plddt_mean":87.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CAND2","jax_strain_url":"https://www.jax.org/strain/search?query=CAND2"},"sequence":{"accession":"O75155","fasta_url":"https://rest.uniprot.org/uniprotkb/O75155.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75155/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75155"}},"corpus_meta":[{"pmid":"17242400","id":"PMC_17242400","title":"TBP-interacting protein 120B (TIP120B)/cullin-associated and neddylation-dissociated 2 (CAND2) inhibits SCF-dependent ubiquitination of myogenin and accelerates myogenic differentiation.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17242400","citation_count":41,"is_preprint":false},{"pmid":"10441524","id":"PMC_10441524","title":"TIP120B: a novel TIP120-family protein that is expressed specifically in muscle tissues.","date":"1999","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/10441524","citation_count":31,"is_preprint":false},{"pmid":"12692129","id":"PMC_12692129","title":"Proteolytic targeting of transcriptional regulator TIP120B by a HECT domain E3 ligase.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12692129","citation_count":23,"is_preprint":false},{"pmid":"34605609","id":"PMC_34605609","title":"Muscle-specific Cand2 is translationally upregulated by mTORC1 and promotes adverse cardiac remodeling.","date":"2021","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/34605609","citation_count":18,"is_preprint":false},{"pmid":"19159115","id":"PMC_19159115","title":"Evaluation of CAND2 and WNT7a as candidate genes for congenital idiopathic clubfoot.","date":"2009","source":"Clinical orthopaedics and related research","url":"https://pubmed.ncbi.nlm.nih.gov/19159115","citation_count":14,"is_preprint":false},{"pmid":"27203392","id":"PMC_27203392","title":"NEURL rs6584555 and CAND2 rs4642101 contribute to postoperative atrial fibrillation: a prospective study among Chinese population.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/27203392","citation_count":11,"is_preprint":false},{"pmid":"29717274","id":"PMC_29717274","title":"Detecting epistasis within chromatin regulatory circuitry reveals CAND2 as a novel susceptibility gene for obesity.","date":"2018","source":"International journal of obesity (2005)","url":"https://pubmed.ncbi.nlm.nih.gov/29717274","citation_count":7,"is_preprint":false},{"pmid":"37718510","id":"PMC_37718510","title":"Cand2 inhibits CRL-mediated ubiquitination and suppresses autophagy to facilitate pathogenicity of phytopathogenic fungi.","date":"2023","source":"Plant communications","url":"https://pubmed.ncbi.nlm.nih.gov/37718510","citation_count":5,"is_preprint":false},{"pmid":"40011427","id":"PMC_40011427","title":"Molecular mechanisms of CAND2 in regulating SCF ubiquitin ligases.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40011427","citation_count":3,"is_preprint":false},{"pmid":"41864201","id":"PMC_41864201","title":"CAND1 and CAND2 drive CUL4 substrate receptor exchange with largely comparable biochemical efficiency, unlike their relative effects on CUL1.","date":"2026","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/41864201","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6968,"output_tokens":1747,"usd":0.023554,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8576,"output_tokens":2338,"usd":0.050665,"stage2_stop_reason":"end_turn"},"total_usd":0.074219,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"TIP120B (CAND2) is a muscle-specific protein that binds TBP (TATA-binding protein) as shown by GST pull-down assay using GST-fused TBP with nuclear extract, and is expressed specifically in muscle tissues with transient upregulation during embryogenesis.\",\n      \"method\": \"GST pull-down assay, Northern blot, Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct pull-down demonstrating TBP binding, confirmed by tissue-specific expression data; single lab, two orthogonal methods\",\n      \"pmids\": [\"10441524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"KIAA10 (a HECT domain E3 ubiquitin ligase) targets TIP120B (CAND2) for proteolytic degradation: the N-terminal domain of KIAA10 binds TIP120B, and KIAA10 ubiquitinates TIP120B as a specific substrate in vitro and in C2C12 myoblasts, but not TIP120A (CAND1). This substrate specificity is tissue-restricted, as it occurs in muscle cells but not Cos-1 cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, co-transfection studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro ubiquitination assay plus co-transfection and binding studies in relevant cell lines, with clear substrate specificity discrimination between CAND2 and CAND1\",\n      \"pmids\": [\"12692129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TIP120B (CAND2) suppresses SCF (Skp1-CUL1-F-box protein) ubiquitin ligase-dependent ubiquitination of myogenin by binding CUL1 and disrupting the SCF-myogenin complex, thereby stabilizing myogenin and accelerating myogenic differentiation of C2C12 cells. CUL1 siRNA knockdown independently inhibited myogenin ubiquitination, confirming SCF involvement. CAND2 was associated with the SCF complex in cells, and myogenin was also found in this complex.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, ubiquitination assay, overexpression in C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, siRNA epistasis, and ubiquitination assay with multiple orthogonal approaches in a single study\",\n      \"pmids\": [\"17242400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cand2 is translationally upregulated downstream of mTORC1 signaling in cardiomyocytes, and Cand2 deletion protects against pathological cardiac remodeling. Mechanistically, Cand2 links mTOR signaling to pathological cell growth by increasing GRK5 protein expression.\",\n      \"method\": \"Genome-wide ribosome sequencing (ribosome profiling), Cand2 knockout mouse model, protein expression analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ribosome profiling plus genetic KO with defined phenotypic readout and GRK5 protein-level measurement; single lab\",\n      \"pmids\": [\"34605609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CAND2 functions as an F-box protein exchange factor for SCF (CUL1-based) ubiquitin ligases, promoting SCF-mediated protein degradation. CAND2 binds CUL1 with structure and affinity comparable to CAND1, but exhibits lower efficiency in exchanging F-box proteins due to a significantly higher KM for SCF disassembly, attributed to less favorable conformations of the CAND2·SCF exchange intermediate complex.\",\n      \"method\": \"Quantitative binding assays, real-time kinetic measurements, structural analysis, F-box protein exchange assays in human cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with kinetic measurements, structural characterization, and cellular functional assays; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"40011427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CAND2, in addition to its role in CRL1, functions as a bona fide CRL4 exchange factor: CAND2 promotes CRL4-mediated protein degradation and enhances dynamic exchange of DDB1·DCAF substrate receptor modules. Unlike its reduced efficiency relative to CAND1 in CRL1 disassembly, CAND2 exhibits similar kinetic parameters and comparable exchange efficiency to CAND1 across most CRL4 complexes.\",\n      \"method\": \"Genetic perturbation, real-time kinetic analyses, quantitative interaction proteomics\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — kinetic measurements, quantitative proteomics, and genetic perturbation with multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"41864201\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CAND2 (TIP120B) is a muscle-enriched paralog of CAND1 that acts as an F-box protein exchange factor for both CRL1 (SCF) and CRL4 ubiquitin ligase complexes, promoting substrate receptor cycling; it binds CUL1 with affinity comparable to CAND1 but exchanges F-box proteins less efficiently due to a higher KM for SCF disassembly, while showing comparable efficiency to CAND1 on CRL4; in muscle, CAND2 stabilizes the pro-differentiation transcription factor myogenin by disrupting the SCF–myogenin complex and suppressing myogenin ubiquitination, thereby accelerating myogenesis; CAND2 is itself a substrate of the HECT E3 ligase KIAA10 specifically in muscle cells; and in the heart CAND2 is translationally upregulated by mTORC1 and promotes pathological cardiac remodeling by increasing GRK5 protein levels.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CAND2 (TIP120B) is a muscle-enriched regulator of cullin-RING ubiquitin ligase (CRL) activity that controls substrate receptor cycling and, through it, the stability of myogenic and cardiac signaling factors [#2, #4]. It functions as an F-box protein exchange factor for CUL1-based SCF ligases, binding CUL1 with structure and affinity comparable to CAND1 but disassembling SCF less efficiently owing to a higher KM for the exchange intermediate [#4]; it acts in parallel as a bona fide CRL4 exchange factor, enhancing dynamic exchange of DDB1·DCAF substrate receptor modules with kinetics comparable to CAND1 [#5]. In muscle, CAND2 binds CUL1 and disrupts the SCF–myogenin complex, suppressing myogenin ubiquitination to stabilize this transcription factor and accelerate myogenic differentiation of C2C12 cells [#2]. CAND2 is itself a tissue-restricted substrate of the HECT E3 ligase KIAA10, which binds and ubiquitinates CAND2 (but not CAND1) specifically in muscle cells [#1]. In the heart, CAND2 is translationally upregulated downstream of mTORC1 and drives pathological cardiac remodeling by increasing GRK5 protein levels, with Cand2 deletion conferring protection [#3]. An early observation that CAND2 binds TBP and is muscle-specific established its tissue restriction [#0]; how this interaction integrates with its CRL exchange function has not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established CAND2 as a distinct, muscle-specific protein and gave the first candidate interaction, linking it to the basal transcription machinery via TBP.\",\n      \"evidence\": \"GST pull-down with GST-TBP against nuclear extract, plus Northern/Western tissue profiling\",\n      \"pmids\": [\"10441524\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional consequence of TBP binding shown\", \"Interaction not reconciled with later CRL exchange role\", \"Single-lab pull-down without reciprocal validation\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed CAND2 is regulated by targeted proteolysis in a tissue-restricted manner, distinguishing it from CAND1 and indicating muscle-specific control of CAND2 levels.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitination, and co-transfection in C2C12 myoblasts versus Cos-1 cells with KIAA10\",\n      \"pmids\": [\"12692129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signal triggering CAND2 degradation unknown\", \"Consequences of CAND2 turnover for CRL function not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined a mechanistic role for CAND2 in myogenesis by showing it protects a pro-differentiation transcription factor from SCF-mediated degradation.\",\n      \"evidence\": \"Reciprocal Co-IP, CUL1 siRNA epistasis, and myogenin ubiquitination assays in C2C12 cells\",\n      \"pmids\": [\"17242400\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether stabilization reflects general exchange-factor activity or a dedicated myogenin mechanism unresolved\", \"Identity of the relevant F-box receptor for myogenin not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended CAND2 into cardiac pathophysiology, placing it downstream of mTORC1 as a driver of pathological growth via GRK5.\",\n      \"evidence\": \"Ribosome profiling and Cand2 knockout mouse with GRK5 protein-level readout\",\n      \"pmids\": [\"34605609\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular route from CAND2 to elevated GRK5 not defined\", \"Whether CRL exchange activity mediates the GRK5 effect untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the biochemical mechanism for CAND2 as an SCF F-box exchange factor and quantified why it is a weaker disassembler than CAND1.\",\n      \"evidence\": \"Quantitative binding, real-time kinetics, structural analysis, and cellular F-box exchange assays\",\n      \"pmids\": [\"40011427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional significance of reduced SCF exchange efficiency in vivo unclear\", \"Tissue-specific consequences of the kinetic difference not addressed\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Broadened CAND2's exchange-factor function to CRL4, showing it cycles DDB1·DCAF modules with CAND1-like efficiency, unlike its weaker CRL1 activity.\",\n      \"evidence\": \"Real-time kinetics, quantitative interaction proteomics, and genetic perturbation\",\n      \"pmids\": [\"41864201\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific CRL4 substrates regulated by CAND2 not enumerated\", \"Why CAND2 is CRL4-efficient but CRL1-impaired structurally unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CAND2's CRL exchange-factor activity, its TBP binding, and its tissue-specific roles in myogenesis and cardiac remodeling are mechanistically connected remains open.\",\n      \"evidence\": \"No single study integrates the biochemical exchange function with the muscle/heart phenotypes\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No demonstration that GRK5 or myogenin regulation requires CAND2 exchange activity\", \"TBP interaction unexplained in CRL context\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 4, 5]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\"SCF (CRL1)\", \"CRL4 (DDB1-DCAF)\"],\n    \"partners\": [\"CUL1\", \"DDB1\", \"KIAA10\", \"TBP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}