{"gene":"RHOBTB2","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2002,"finding":"RHOBTB2 (DBC2) expression in breast cancer cells lacking DBC2 transcripts causes growth inhibition, establishing a functional tumor suppressor role; a somatic missense mutant discovered in a breast cancer specimen does not suppress growth, indicating loss-of-function relevance.","method":"Ectopic expression in DBC2-negative breast cancer cells, growth inhibition assay; somatic mutant functional comparison","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional expression experiment with mutant comparison, single lab, two conditions (WT vs mutant)","pmids":["12370419"],"is_preprint":false},{"year":2004,"finding":"RhoBTB2 binds to the ubiquitin ligase scaffold Cul3 via its first BTB domain, and is itself a substrate for ubiquitination and proteasomal degradation by the Cul3-based ubiquitin ligase complex both in vitro and in vivo. A lung cancer-derived missense mutant of RhoBTB2 is unable to bind Cul3 and is not regulated by the ubiquitin/proteasome system, resulting in elevated RhoBTB2 protein levels.","method":"Co-immunoprecipitation (binding to Cul3), in vitro and in vivo ubiquitination assays, domain mapping (BTB1 domain), analysis of cancer-derived mutant","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro ubiquitination assay plus in vivo experiments, domain mapping, cancer mutant validation, single rigorous study with multiple orthogonal methods","pmids":["15107402"],"is_preprint":false},{"year":2006,"finding":"DBC2/RhoBTB2 is required for microtubule-dependent vesicular transport of VSV-G glycoprotein from the ER to the Golgi apparatus; RhoBTB2 mobility itself depends on an intact microtubule network.","method":"siRNA knockdown of DBC2 in 293 cells; VSVG-GFP transport assay; microtubule disruption experiments","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell transport assay with RNAi knockdown and cytoskeletal perturbation, single lab, two orthogonal approaches","pmids":["17023000"],"is_preprint":false},{"year":2007,"finding":"RhoBTB2 is a direct transcriptional target of E2F1; RhoBTB2 expression is upregulated by E2F1 overexpression even in the presence of cycloheximide (indicating direct regulation), and RNAi knockdown of E2F1 decreases RhoBTB2 protein. RhoBTB2 expression is elevated during mitosis and during drug-induced apoptosis in an E2F1-dependent manner; siRNA knockdown of RhoBTB2 delays drug-induced apoptosis.","method":"E2F1 overexpression with cycloheximide treatment, siRNA knockdown of E2F1 and RhoBTB2, cell cycle analysis, apoptosis assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple siRNA and overexpression experiments with cycloheximide control establishing direct transcriptional regulation, single lab","pmids":["18039672"],"is_preprint":false},{"year":2007,"finding":"DBC2 suppresses breast cancer proliferation through down-regulation of Cyclin D1 (CCND1); constitutive overexpression of CCND1 (or CCNE1 under the CCND1 promoter) prevents the growth-suppressive effect of DBC2, establishing CCND1 down-regulation as an essential step in DBC2's tumor suppressor mechanism.","method":"DBC2 expression in breast cancer cells, CCND1 overexpression rescue experiment, cell proliferation assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis/rescue experiment establishing pathway dependence, single lab, single study","pmids":["17517369"],"is_preprint":false},{"year":2007,"finding":"DBC2-resistant breast cancer cells survive DBC2 induction by rapid degradation of DBC2 protein via the 26S proteasome; proteasome inhibition (MG132) restores DBC2 protein detection in resistant cells.","method":"Inducible DBC2 expression system, MG132 proteasome inhibitor treatment, Western blot","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition of proteasome with functional rescue, single lab, mechanistically informative negative control (GFP induction confirmed functional)","pmids":["17617377"],"is_preprint":false},{"year":2008,"finding":"Loss of RhoBTB2 expression in primary human epithelial cells results in down-regulation of CXCL14; reintroduction of RhoBTB2 into head and neck squamous cell carcinoma lines restores CXCL14 secretion, identifying CXCL14 as a downstream gene target of RhoBTB2.","method":"siRNA knockdown in primary human epithelial cells, microarray gene expression analysis, CXCL14 secretion assay, RhoBTB2 re-expression in cancer cell lines","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi plus rescue experiment in multiple cell contexts, single lab, two orthogonal functional readouts","pmids":["18762809"],"is_preprint":false},{"year":2008,"finding":"The Cul3 ubiquitin ligase complex ubiquitinates RhoBTB2 directly, leading to its degradation by the proteasome; detailed cell biological and biochemical methods for analyzing this regulation are established.","method":"Co-immunoprecipitation, in vitro ubiquitination assay, proteasome inhibitor experiments (methods review paper)","journal":"Methods in enzymology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — biochemical methods paper confirming prior in vitro and in vivo results from the same group, single lab","pmids":["18374159"],"is_preprint":false},{"year":2014,"finding":"DBC2/RhoBTB2 associates with Hsp90 and its co-chaperone Cdc37 in reticulocyte lysate and MCF7 cells; DBC2 retains the capacity to bind GTP, which is modulated by the Hsp90 ATPase cycle (geldanamycin suppresses GTP binding; molybdate enhances it). Assembly of DBC2–Cul3–COP9 E3 ligase complexes is Hsp90-dependent.","method":"Pull-down assays, GTP-binding assays, Hsp90 inhibitor (geldanamycin) and stabilizer (molybdate) treatment, co-immunoprecipitation of DBC2-Cul3-COP9 complex","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical approaches (pulldown, GTP binding, pharmacological modulation, co-IP), single lab","pmids":["24608665"],"is_preprint":false},{"year":2016,"finding":"DBC2/RhoBTB2 acts as a substrate-specific adaptor for the Cul3-based E3 ubiquitin ligase; it directly interacts with Musashi-2 (MSI2), promoting MSI2 polyubiquitination and proteasomal degradation in breast cancer cells. DBC2 overexpression suppresses MSI2-associated oncogenic functions and induces apoptosis; DBC2 and MSI2 protein levels are inversely correlated in breast cancer tissues.","method":"Genome-wide cDNA library-based in vitro ubiquitination target screen, co-immunoprecipitation (DBC2–MSI2 interaction), overexpression and siRNA knockdown experiments, proteasomal degradation assays, IHC tissue microarray","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — genome-wide in vitro ubiquitination screen followed by co-IP validation, functional overexpression/KD experiments with defined substrate (MSI2), multiple orthogonal methods in single study","pmids":["27941885"],"is_preprint":false},{"year":2010,"finding":"Ectopic RhoBTB2 expression inhibits migration and invasion of metastatic breast cancer cells by upregulating the metastasis suppressor BRMS1 and decreasing phosphorylation of ezrin and Akt2; siRNA knockdown of BRMS1 reverses RhoBTB2-mediated inhibition of migration and invasion.","method":"Ectopic RhoBTB2 expression, siRNA knockdown of BRMS1, Transwell migration/invasion assays, Western blot for BRMS1, phospho-ezrin, and phospho-Akt2","journal":"Cancer biology & therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression with epistasis rescue (BRMS1 KD), multiple signaling readouts, single lab","pmids":["20930524"],"is_preprint":false},{"year":2018,"finding":"De novo missense variants in RHOBTB2 BTB domains result in mutant protein accumulation; co-expression of CUL3 with wild-type RHOBTB2 decreased WT protein levels but not those of any of three disease-associated mutants, demonstrating that disease-causing variants impair CUL3-dependent proteasomal degradation of RHOBTB2.","method":"Transient expression in Neuro-2a cells, co-expression with CUL3, Western blot quantification of WT vs mutant RHOBTB2 protein levels","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct comparison of WT vs three disease mutants with CUL3 co-expression, single lab, single study","pmids":["29768694"],"is_preprint":false},{"year":2025,"finding":"BTB-domain variants of RHOBTB2 (R461H, R485C, R489Q) cause increased RHOBTB2 protein accumulation with nuclear and mitochondrial localization, and lead to significantly altered neuronal excitability (measured by patch-clamp) and downregulation of ion channel genes including those related to sodium channels (paralytic/SCN1A ortholog). GTPase-domain variants (D92H, W217C) do not alter protein levels but reduce Na+/K+-ATPase protein via lysosome-dependent degradation. Functional genetic interaction between RhoBTB and paralytic (SCN1A ortholog) was confirmed in Drosophila in vivo. Complete loss of RHOBTB2 does not produce the same neuronal excitability phenotype as BTB-domain variants.","method":"Drosophila RNA-seq on fly heads overexpressing RhoBTB, genetic interaction experiments in flies; patch-clamp recordings on iPSC-derived neurons with homozygous frameshifts or patient-specific missense variants; doxycycline-inducible cell model; protein localization analysis; RNA-seq in cell model; lysosome inhibitor experiments","journal":"Human molecular genetics / Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods across model organisms and human iPSC-derived neurons, genetic interaction validation in vivo, electrophysiology with direct mechanistic readout","pmids":["39849855","41478322"],"is_preprint":false},{"year":2025,"finding":"In AML cells, RHOBTB2 directly interacts with KLHL13 (validated by co-immunoprecipitation); RHOBTB2 stabilizes KLHL13 protein by inhibiting its proteasomal degradation (MG132 reverses KLHL13 loss upon RHOBTB2 knockdown). RHOBTB2 promotes AML cell proliferation and migration and suppresses apoptosis, acting through KLHL13 and the Hippo-YAP1 pathway.","method":"Co-immunoprecipitation (RHOBTB2–KLHL13), siRNA knockdown, MG132 proteasome inhibitor rescue, Western blot, CCK-8 proliferation assay, Transwell assay, Annexin V/PI apoptosis assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus proteasomal inhibitor rescue establishing functional interaction, single lab, multiple functional readouts","pmids":["41107424"],"is_preprint":false}],"current_model":"RHOBTB2 (DBC2) is an atypical Rho GTPase that functions primarily as a substrate-specific adaptor for the Cul3-based E3 ubiquitin ligase complex—binding Cul3 via its first BTB domain—to promote ubiquitination and proteasomal degradation of substrates including Musashi-2 (MSI2); the Cul3-RHOBTB2 complex assembly is Hsp90-dependent, and disease-causing BTB-domain missense variants impair Cul3-mediated degradation of RHOBTB2 itself, causing protein accumulation with nuclear/mitochondrial localization, deregulated ion channel expression, and altered neuronal excitability, while tumor-suppressor functions are mediated through CCND1 downregulation, CXCL14 upregulation, BRMS1-dependent inhibition of migration/invasion, and E2F1-regulated apoptosis."},"narrative":{"mechanistic_narrative":"RHOBTB2 (DBC2) is an atypical Rho GTPase that functions principally as a substrate-specific adaptor for Cul3-based E3 ubiquitin ligase complexes, coupling protein ubiquitination to control of cell proliferation, apoptosis, and neuronal excitability [PMID:15107402, PMID:27941885]. It binds the Cul3 scaffold through its first BTB domain and is itself a substrate of the Cul3 complex, undergoing proteasomal degradation; a cancer-derived missense mutant that fails to bind Cul3 escapes this regulation and accumulates [PMID:15107402]. Assembly of the DBC2–Cul3–COP9 ligase is Hsp90-dependent, and DBC2 associates with Hsp90/Cdc37 while retaining GTP-binding capacity modulated by the Hsp90 ATPase cycle [PMID:24608665]. As an adaptor, RHOBTB2 directs polyubiquitination and degradation of substrates including the RNA-binding oncoprotein Musashi-2 (MSI2), and DBC2 and MSI2 levels are inversely correlated in breast cancer [PMID:27941885]. Its tumor-suppressor activity—first established by growth inhibition upon re-expression in DBC2-negative breast cancer cells [PMID:12370419]—operates through downregulation of Cyclin D1 (CCND1) as an essential step [PMID:17517369], upregulation of CXCL14 [PMID:18762809] and the metastasis suppressor BRMS1 with decreased phospho-ezrin and phospho-Akt2 to inhibit migration/invasion [PMID:20930524], and E2F1-dependent transcriptional induction during apoptosis, where RHOBTB2 is a direct E2F1 target whose knockdown delays drug-induced apoptosis [PMID:18039672]. De novo BTB-domain missense variants impair Cul3-dependent degradation of RHOBTB2, causing protein accumulation with nuclear and mitochondrial localization, downregulation of ion channel genes, and altered neuronal excitability—a phenotype distinct from complete loss of RHOBTB2 and validated by a genetic interaction with the SCN1A ortholog paralytic in Drosophila [PMID:29768694, PMID:39849855, PMID:41478322].","teleology":[{"year":2002,"claim":"Established RHOBTB2/DBC2 as a functional tumor suppressor by showing re-expression inhibits growth in cancer cells that have lost it, while a cancer-derived mutant cannot.","evidence":"Ectopic expression in DBC2-negative breast cancer cells with WT vs somatic mutant comparison and growth assays","pmids":["12370419"],"confidence":"Medium","gaps":["No molecular mechanism for growth suppression identified","Single cell-context, no in vivo validation"]},{"year":2004,"claim":"Defined the core biochemical activity: RHOBTB2 binds the Cul3 ligase scaffold via its first BTB domain and is itself a Cul3 ubiquitination substrate, with a cancer mutant escaping this regulation.","evidence":"Co-IP, in vitro and in vivo ubiquitination assays, BTB1 domain mapping, cancer-mutant analysis","pmids":["15107402"],"confidence":"High","gaps":["Did not identify substrates other than RHOBTB2 itself","Structural basis of BTB–Cul3 interaction not resolved"]},{"year":2006,"claim":"Linked RHOBTB2 to microtubule-dependent ER-to-Golgi vesicular transport, broadening its cellular role beyond ubiquitination.","evidence":"siRNA knockdown in 293 cells with VSVG-GFP transport assay and microtubule disruption","pmids":["17023000"],"confidence":"Medium","gaps":["Molecular mechanism connecting RHOBTB2 to transport unknown","No identified transport machinery partner"]},{"year":2007,"claim":"Connected RHOBTB2 to cell-cycle and apoptotic transcriptional control, showing it is a direct E2F1 target required for timely drug-induced apoptosis.","evidence":"E2F1 overexpression with cycloheximide, E2F1 and RHOBTB2 siRNA, cell-cycle and apoptosis assays","pmids":["18039672"],"confidence":"Medium","gaps":["Pro-apoptotic effector mechanism downstream of RHOBTB2 not defined"]},{"year":2007,"claim":"Identified CCND1 downregulation as an essential, non-bypassable step in DBC2-mediated growth suppression.","evidence":"DBC2 expression with CCND1/CCNE1 overexpression rescue and proliferation assays; inducible expression with MG132 in resistant cells","pmids":["17517369","17617377"],"confidence":"Medium","gaps":["Whether CCND1 is a direct RHOBTB2 ubiquitination target unresolved","Mechanism of resistance via proteasomal DBC2 destruction not fully mapped"]},{"year":2008,"claim":"Expanded the downstream gene network by identifying CXCL14 as a RHOBTB2-regulated target restored upon re-expression in carcinoma cells.","evidence":"siRNA in primary epithelial cells, microarray, CXCL14 secretion assay, re-expression in HNSCC lines","pmids":["18762809"],"confidence":"Medium","gaps":["Whether CXCL14 regulation is transcriptional or via ubiquitination is unclear","Causal link to tumor suppression not formally tested"]},{"year":2010,"claim":"Defined an anti-metastatic mechanism in which RHOBTB2 upregulates BRMS1 and dampens ezrin/Akt2 signaling to block migration and invasion.","evidence":"Ectopic RHOBTB2 expression, BRMS1 siRNA rescue, Transwell assays, phospho-protein Western blots","pmids":["20930524"],"confidence":"Medium","gaps":["Mechanism linking RHOBTB2 to BRMS1 upregulation unknown","Single cell-line system"]},{"year":2014,"claim":"Established that DBC2–Cul3–COP9 ligase assembly is Hsp90/Cdc37-dependent and that DBC2 GTP binding is coupled to the Hsp90 ATPase cycle.","evidence":"Pull-downs, GTP-binding assays, geldanamycin/molybdate modulation, complex co-IP in reticulocyte lysate and MCF7 cells","pmids":["24608665"],"confidence":"Medium","gaps":["Functional consequence of GTP binding for adaptor activity not defined","No GTPase cycling regulators identified"]},{"year":2016,"claim":"Defined RHOBTB2 as a substrate-receptor adaptor with a bona fide degradation target, MSI2, linking its ubiquitin-ligase function to suppression of oncogenic signaling.","evidence":"Genome-wide cDNA in vitro ubiquitination screen, DBC2–MSI2 co-IP, overexpression/knockdown, degradation assays, IHC tissue microarray","pmids":["27941885"],"confidence":"High","gaps":["Degron on MSI2 recognized by RHOBTB2 not mapped","Other substrates from the screen not characterized"]},{"year":2025,"claim":"Mechanistically distinguished disease-causing BTB-domain variants—which impair Cul3-mediated self-degradation, accumulate in nucleus/mitochondria, and deregulate ion channels to alter neuronal excitability—from loss of function and GTPase-domain variants.","evidence":"Co-expression of CUL3 with WT vs mutants in Neuro-2a; Drosophila RNA-seq and paralytic genetic interaction; iPSC-neuron patch-clamp; inducible cell model with lysosome inhibitor experiments","pmids":["29768694","39849855","41478322"],"confidence":"Medium","gaps":["Direct ion-channel substrate relationship vs transcriptional effect not separated","Mechanism of mitochondrial localization unresolved"]},{"year":2025,"claim":"Revealed a context-dependent stabilizing role in AML, where RHOBTB2 binds and protects KLHL13 from degradation to drive proliferation via Hippo-YAP1.","evidence":"RHOBTB2–KLHL13 co-IP, siRNA, MG132 rescue, proliferation/migration/apoptosis assays","pmids":["41107424"],"confidence":"Medium","gaps":["How RHOBTB2 stabilizes rather than degrades KLHL13 is unexplained","Reconciliation with tumor-suppressor role in other cancers absent"]},{"year":null,"claim":"How RHOBTB2 selects between its degradative adaptor function and protein-stabilizing role, and the rules governing substrate recognition across tissues, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of substrate engagement","Determinants of context-specific tumor-suppressor vs oncogenic behavior unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,9]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[9]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[12]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[12]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,9]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,9]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[12]}],"complexes":["Cul3-RHOBTB2 E3 ubiquitin ligase","DBC2–Cul3–COP9 signalosome complex"],"partners":["CUL3","MSI2","HSP90","CDC37","KLHL13","E2F1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BYZ6","full_name":"Rho-related BTB domain-containing protein 2","aliases":["Deleted in breast cancer 2 gene protein","p83"],"length_aa":727,"mass_kda":82.6,"function":"Regulator of cell proliferation and apoptosis (PubMed:21801820). It likely functions as a substrate-adapter that recruits key substrates, e.g. MSI2, to CUL3-based ubiquitin ligase complexes for degradation (PubMed:15107402, PubMed:27941885). Required for MSI2 ubiquitination and degradation (PubMed:27941885)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9BYZ6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RHOBTB2","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/RHOBTB2","total_profiled":1310},"omim":[{"mim_id":"618753","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 41; LRRC41","url":"https://www.omim.org/entry/618753"},{"mim_id":"618004","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 64; DEE64","url":"https://www.omim.org/entry/618004"},{"mim_id":"607353","title":"RHO-RELATED BTB DOMAIN-CONTAINING PROTEIN 3; RHOBTB3","url":"https://www.omim.org/entry/607353"},{"mim_id":"607352","title":"RHO-RELATED BTB DOMAIN-CONTAINING PROTEIN 2; RHOBTB2","url":"https://www.omim.org/entry/607352"},{"mim_id":"607351","title":"RHO-RELATED BTB DOMAIN-CONTAINING PROTEIN 1; RHOBTB1","url":"https://www.omim.org/entry/607351"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RHOBTB2"},"hgnc":{"alias_symbol":["KIAA0717","DBC2"],"prev_symbol":[]},"alphafold":{"accession":"Q9BYZ6","domains":[{"cath_id":"3.40.50.300","chopping":"14-222","consensus_level":"high","plddt":85.9672,"start":14,"end":222},{"cath_id":"3.30.710.10","chopping":"267-301_384-489","consensus_level":"medium","plddt":92.5302,"start":267,"end":489}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BYZ6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BYZ6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BYZ6-F1-predicted_aligned_error_v6.png","plddt_mean":81.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RHOBTB2","jax_strain_url":"https://www.jax.org/strain/search?query=RHOBTB2"},"sequence":{"accession":"Q9BYZ6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BYZ6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BYZ6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BYZ6"}},"corpus_meta":[{"pmid":"12370419","id":"PMC_12370419","title":"DBC2, a candidate for a tumor suppressor gene involved in breast cancer.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12370419","citation_count":186,"is_preprint":false},{"pmid":"15107402","id":"PMC_15107402","title":"RhoBTB2 is a substrate of the mammalian Cul3 ubiquitin ligase complex.","date":"2004","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/15107402","citation_count":106,"is_preprint":false},{"pmid":"15663929","id":"PMC_15663929","title":"DBC2 significantly influences cell-cycle, apoptosis, cytoskeleton and membrane-trafficking pathways.","date":"2004","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15663929","citation_count":67,"is_preprint":false},{"pmid":"15922864","id":"PMC_15922864","title":"Mutation analysis of the 8p candidate tumour suppressor genes DBC2 (RHOBTB2) and LZTS1 in bladder cancer.","date":"2004","source":"Cancer 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novo variants in RHOBTB2, an atypical Rho GTPase gene, cause epileptic encephalopathy.","date":"2018","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/29768694","citation_count":31,"is_preprint":false},{"pmid":"17023000","id":"PMC_17023000","title":"DBC2 is essential for transporting vesicular stomatitis virus glycoprotein.","date":"2006","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17023000","citation_count":31,"is_preprint":false},{"pmid":"17517369","id":"PMC_17517369","title":"Cyclin D1 down-regulation is essential for DBC2's tumor suppressor function.","date":"2007","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/17517369","citation_count":28,"is_preprint":false},{"pmid":"33504645","id":"PMC_33504645","title":"RHOBTB2 Mutations Expand the Phenotypic Spectrum of Alternating Hemiplegia of 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multifunctional tumor suppressor in thyroid cancer cells via mitochondrial apoptotic pathway.","date":"2015","source":"International journal of clinical and experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26131191","citation_count":11,"is_preprint":false},{"pmid":"17653899","id":"PMC_17653899","title":"Mutation analysis of the DBC2 gene in sporadic and familial breast cancer.","date":"2007","source":"Acta oncologica (Stockholm, Sweden)","url":"https://pubmed.ncbi.nlm.nih.gov/17653899","citation_count":11,"is_preprint":false},{"pmid":"34457998","id":"PMC_34457998","title":"Novel miR-5088-5p promotes malignancy of breast cancer by inhibiting DBC2.","date":"2021","source":"Molecular therapy. 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Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32337345","citation_count":10,"is_preprint":false},{"pmid":"23777252","id":"PMC_23777252","title":"Downregulated RhoBTB2 expression contributes to poor outcome in osteosarcoma patients.","date":"2013","source":"Cancer biotherapy & radiopharmaceuticals","url":"https://pubmed.ncbi.nlm.nih.gov/23777252","citation_count":10,"is_preprint":false},{"pmid":"15567721","id":"PMC_15567721","title":"High expression during neurogenesis but not mammogenesis of a murine homologue of the Deleted in Breast Cancer2/Rhobtb2 tumor suppressor.","date":"2004","source":"Gene expression patterns : GEP","url":"https://pubmed.ncbi.nlm.nih.gov/15567721","citation_count":10,"is_preprint":false},{"pmid":"22901165","id":"PMC_22901165","title":"Loss of DBC2 expression is an early and progressive event in the development of lung adenocarcinoma.","date":"2012","source":"Asian Pacific journal of cancer prevention : APJCP","url":"https://pubmed.ncbi.nlm.nih.gov/22901165","citation_count":9,"is_preprint":false},{"pmid":"23626933","id":"PMC_23626933","title":"Evaluation of Methylation Status in the 5'UTR Promoter Region of the DBC2 Gene as a Biomarker in Sporadic Breast Cancer.","date":"2012","source":"Cell journal","url":"https://pubmed.ncbi.nlm.nih.gov/23626933","citation_count":9,"is_preprint":false},{"pmid":"23546941","id":"PMC_23546941","title":"Decreased expression of the DBC2 gene and its clinicopathological significance in breast cancer: correlation with aberrant DNA methylation.","date":"2013","source":"Biotechnology letters","url":"https://pubmed.ncbi.nlm.nih.gov/23546941","citation_count":8,"is_preprint":false},{"pmid":"24356943","id":"PMC_24356943","title":"RhoBTB2 gene in breast cancer is silenced by promoter methylation.","date":"2013","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/24356943","citation_count":8,"is_preprint":false},{"pmid":"19173804","id":"PMC_19173804","title":"[Expressions of Fas, CTLA-4 and RhoBTB2 genes in breast carcinoma and their relationship with clinicopathological factors].","date":"2008","source":"Zhonghua zhong liu za zhi [Chinese journal of oncology]","url":"https://pubmed.ncbi.nlm.nih.gov/19173804","citation_count":8,"is_preprint":false},{"pmid":"35315256","id":"PMC_35315256","title":"Developmental and epileptic encephalopathy related to a heterozygous variant of the RHOBTB2 gene: A case report from French Guiana.","date":"2022","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35315256","citation_count":8,"is_preprint":false},{"pmid":"37090824","id":"PMC_37090824","title":"RHOBTB2 p.Arg511Trp Mutation in Early Infantile Epileptic Encephalopathy-64: Review and Case Report.","date":"2021","source":"Journal of pediatric genetics","url":"https://pubmed.ncbi.nlm.nih.gov/37090824","citation_count":5,"is_preprint":false},{"pmid":"18374159","id":"PMC_18374159","title":"Regulation of RhoBTB2 by the Cul3 ubiquitin ligase complex.","date":"2008","source":"Methods in enzymology","url":"https://pubmed.ncbi.nlm.nih.gov/18374159","citation_count":5,"is_preprint":false},{"pmid":"39849855","id":"PMC_39849855","title":"Deregulated ion channels contribute to RHOBTB2-associated developmental and epileptic encephalopathy.","date":"2025","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39849855","citation_count":3,"is_preprint":false},{"pmid":"39736890","id":"PMC_39736890","title":"Variants in RHOBTB2 associated with cancer and rare developmental and epileptic encephalopathy.","date":"2024","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/39736890","citation_count":2,"is_preprint":false},{"pmid":"39831600","id":"PMC_39831600","title":"RHOBTB2 Variant p.Arg511Gln Causes Developmental and Epileptic Encephalopathy Type 64 in an Infant: A Case Report and Hotspot Variant Analysis.","date":"2025","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39831600","citation_count":2,"is_preprint":false},{"pmid":"41107424","id":"PMC_41107424","title":"RHOBTB2 enhances cell proliferation of acute myeloid leukemia by modulating Hippo-YAP1 signaling and dependent of KLHL13.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41107424","citation_count":1,"is_preprint":false},{"pmid":"39129541","id":"PMC_39129541","title":"[Neurodevelopmental impact of a mutation in the RHOBTB2 gene].","date":"2024","source":"Revue medicale de Liege","url":"https://pubmed.ncbi.nlm.nih.gov/39129541","citation_count":0,"is_preprint":false},{"pmid":"42187878","id":"PMC_42187878","title":"RHOBTB2-Associated Neurological Phenotypes and Underlying Mechanisms: Alternating Hemiplegia of Childhood Beyond ATP1A3.","date":"2026","source":"Diseases (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/42187878","citation_count":0,"is_preprint":false},{"pmid":"41478322","id":"PMC_41478322","title":"Mutant-specific dysfunction of RHOBTB2 impairs mitochondrial function and Na+/K+-ATPase levels in a cell model.","date":"2025","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/41478322","citation_count":0,"is_preprint":false},{"pmid":"24485767","id":"PMC_24485767","title":"The mutation of DBC2 in breast cancer patients from the Han ethnic group in Eastern China.","date":"2014","source":"Hematology/oncology and stem cell therapy","url":"https://pubmed.ncbi.nlm.nih.gov/24485767","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.13.648593","title":"Developmental, neuroanatomical and cellular expression of genes causing dystonia","date":"2025-04-18","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.13.648593","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20532,"output_tokens":3913,"usd":0.060145,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11653,"output_tokens":3875,"usd":0.07757,"stage2_stop_reason":"end_turn"},"total_usd":0.137715,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"RHOBTB2 (DBC2) expression in breast cancer cells lacking DBC2 transcripts causes growth inhibition, establishing a functional tumor suppressor role; a somatic missense mutant discovered in a breast cancer specimen does not suppress growth, indicating loss-of-function relevance.\",\n      \"method\": \"Ectopic expression in DBC2-negative breast cancer cells, growth inhibition assay; somatic mutant functional comparison\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional expression experiment with mutant comparison, single lab, two conditions (WT vs mutant)\",\n      \"pmids\": [\"12370419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RhoBTB2 binds to the ubiquitin ligase scaffold Cul3 via its first BTB domain, and is itself a substrate for ubiquitination and proteasomal degradation by the Cul3-based ubiquitin ligase complex both in vitro and in vivo. A lung cancer-derived missense mutant of RhoBTB2 is unable to bind Cul3 and is not regulated by the ubiquitin/proteasome system, resulting in elevated RhoBTB2 protein levels.\",\n      \"method\": \"Co-immunoprecipitation (binding to Cul3), in vitro and in vivo ubiquitination assays, domain mapping (BTB1 domain), analysis of cancer-derived mutant\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro ubiquitination assay plus in vivo experiments, domain mapping, cancer mutant validation, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"15107402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DBC2/RhoBTB2 is required for microtubule-dependent vesicular transport of VSV-G glycoprotein from the ER to the Golgi apparatus; RhoBTB2 mobility itself depends on an intact microtubule network.\",\n      \"method\": \"siRNA knockdown of DBC2 in 293 cells; VSVG-GFP transport assay; microtubule disruption experiments\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell transport assay with RNAi knockdown and cytoskeletal perturbation, single lab, two orthogonal approaches\",\n      \"pmids\": [\"17023000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"RhoBTB2 is a direct transcriptional target of E2F1; RhoBTB2 expression is upregulated by E2F1 overexpression even in the presence of cycloheximide (indicating direct regulation), and RNAi knockdown of E2F1 decreases RhoBTB2 protein. RhoBTB2 expression is elevated during mitosis and during drug-induced apoptosis in an E2F1-dependent manner; siRNA knockdown of RhoBTB2 delays drug-induced apoptosis.\",\n      \"method\": \"E2F1 overexpression with cycloheximide treatment, siRNA knockdown of E2F1 and RhoBTB2, cell cycle analysis, apoptosis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple siRNA and overexpression experiments with cycloheximide control establishing direct transcriptional regulation, single lab\",\n      \"pmids\": [\"18039672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"DBC2 suppresses breast cancer proliferation through down-regulation of Cyclin D1 (CCND1); constitutive overexpression of CCND1 (or CCNE1 under the CCND1 promoter) prevents the growth-suppressive effect of DBC2, establishing CCND1 down-regulation as an essential step in DBC2's tumor suppressor mechanism.\",\n      \"method\": \"DBC2 expression in breast cancer cells, CCND1 overexpression rescue experiment, cell proliferation assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis/rescue experiment establishing pathway dependence, single lab, single study\",\n      \"pmids\": [\"17517369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"DBC2-resistant breast cancer cells survive DBC2 induction by rapid degradation of DBC2 protein via the 26S proteasome; proteasome inhibition (MG132) restores DBC2 protein detection in resistant cells.\",\n      \"method\": \"Inducible DBC2 expression system, MG132 proteasome inhibitor treatment, Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition of proteasome with functional rescue, single lab, mechanistically informative negative control (GFP induction confirmed functional)\",\n      \"pmids\": [\"17617377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Loss of RhoBTB2 expression in primary human epithelial cells results in down-regulation of CXCL14; reintroduction of RhoBTB2 into head and neck squamous cell carcinoma lines restores CXCL14 secretion, identifying CXCL14 as a downstream gene target of RhoBTB2.\",\n      \"method\": \"siRNA knockdown in primary human epithelial cells, microarray gene expression analysis, CXCL14 secretion assay, RhoBTB2 re-expression in cancer cell lines\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi plus rescue experiment in multiple cell contexts, single lab, two orthogonal functional readouts\",\n      \"pmids\": [\"18762809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The Cul3 ubiquitin ligase complex ubiquitinates RhoBTB2 directly, leading to its degradation by the proteasome; detailed cell biological and biochemical methods for analyzing this regulation are established.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitination assay, proteasome inhibitor experiments (methods review paper)\",\n      \"journal\": \"Methods in enzymology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — biochemical methods paper confirming prior in vitro and in vivo results from the same group, single lab\",\n      \"pmids\": [\"18374159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"DBC2/RhoBTB2 associates with Hsp90 and its co-chaperone Cdc37 in reticulocyte lysate and MCF7 cells; DBC2 retains the capacity to bind GTP, which is modulated by the Hsp90 ATPase cycle (geldanamycin suppresses GTP binding; molybdate enhances it). Assembly of DBC2–Cul3–COP9 E3 ligase complexes is Hsp90-dependent.\",\n      \"method\": \"Pull-down assays, GTP-binding assays, Hsp90 inhibitor (geldanamycin) and stabilizer (molybdate) treatment, co-immunoprecipitation of DBC2-Cul3-COP9 complex\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical approaches (pulldown, GTP binding, pharmacological modulation, co-IP), single lab\",\n      \"pmids\": [\"24608665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"DBC2/RhoBTB2 acts as a substrate-specific adaptor for the Cul3-based E3 ubiquitin ligase; it directly interacts with Musashi-2 (MSI2), promoting MSI2 polyubiquitination and proteasomal degradation in breast cancer cells. DBC2 overexpression suppresses MSI2-associated oncogenic functions and induces apoptosis; DBC2 and MSI2 protein levels are inversely correlated in breast cancer tissues.\",\n      \"method\": \"Genome-wide cDNA library-based in vitro ubiquitination target screen, co-immunoprecipitation (DBC2–MSI2 interaction), overexpression and siRNA knockdown experiments, proteasomal degradation assays, IHC tissue microarray\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — genome-wide in vitro ubiquitination screen followed by co-IP validation, functional overexpression/KD experiments with defined substrate (MSI2), multiple orthogonal methods in single study\",\n      \"pmids\": [\"27941885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Ectopic RhoBTB2 expression inhibits migration and invasion of metastatic breast cancer cells by upregulating the metastasis suppressor BRMS1 and decreasing phosphorylation of ezrin and Akt2; siRNA knockdown of BRMS1 reverses RhoBTB2-mediated inhibition of migration and invasion.\",\n      \"method\": \"Ectopic RhoBTB2 expression, siRNA knockdown of BRMS1, Transwell migration/invasion assays, Western blot for BRMS1, phospho-ezrin, and phospho-Akt2\",\n      \"journal\": \"Cancer biology & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression with epistasis rescue (BRMS1 KD), multiple signaling readouts, single lab\",\n      \"pmids\": [\"20930524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"De novo missense variants in RHOBTB2 BTB domains result in mutant protein accumulation; co-expression of CUL3 with wild-type RHOBTB2 decreased WT protein levels but not those of any of three disease-associated mutants, demonstrating that disease-causing variants impair CUL3-dependent proteasomal degradation of RHOBTB2.\",\n      \"method\": \"Transient expression in Neuro-2a cells, co-expression with CUL3, Western blot quantification of WT vs mutant RHOBTB2 protein levels\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct comparison of WT vs three disease mutants with CUL3 co-expression, single lab, single study\",\n      \"pmids\": [\"29768694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"BTB-domain variants of RHOBTB2 (R461H, R485C, R489Q) cause increased RHOBTB2 protein accumulation with nuclear and mitochondrial localization, and lead to significantly altered neuronal excitability (measured by patch-clamp) and downregulation of ion channel genes including those related to sodium channels (paralytic/SCN1A ortholog). GTPase-domain variants (D92H, W217C) do not alter protein levels but reduce Na+/K+-ATPase protein via lysosome-dependent degradation. Functional genetic interaction between RhoBTB and paralytic (SCN1A ortholog) was confirmed in Drosophila in vivo. Complete loss of RHOBTB2 does not produce the same neuronal excitability phenotype as BTB-domain variants.\",\n      \"method\": \"Drosophila RNA-seq on fly heads overexpressing RhoBTB, genetic interaction experiments in flies; patch-clamp recordings on iPSC-derived neurons with homozygous frameshifts or patient-specific missense variants; doxycycline-inducible cell model; protein localization analysis; RNA-seq in cell model; lysosome inhibitor experiments\",\n      \"journal\": \"Human molecular genetics / Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods across model organisms and human iPSC-derived neurons, genetic interaction validation in vivo, electrophysiology with direct mechanistic readout\",\n      \"pmids\": [\"39849855\", \"41478322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In AML cells, RHOBTB2 directly interacts with KLHL13 (validated by co-immunoprecipitation); RHOBTB2 stabilizes KLHL13 protein by inhibiting its proteasomal degradation (MG132 reverses KLHL13 loss upon RHOBTB2 knockdown). RHOBTB2 promotes AML cell proliferation and migration and suppresses apoptosis, acting through KLHL13 and the Hippo-YAP1 pathway.\",\n      \"method\": \"Co-immunoprecipitation (RHOBTB2–KLHL13), siRNA knockdown, MG132 proteasome inhibitor rescue, Western blot, CCK-8 proliferation assay, Transwell assay, Annexin V/PI apoptosis assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus proteasomal inhibitor rescue establishing functional interaction, single lab, multiple functional readouts\",\n      \"pmids\": [\"41107424\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RHOBTB2 (DBC2) is an atypical Rho GTPase that functions primarily as a substrate-specific adaptor for the Cul3-based E3 ubiquitin ligase complex—binding Cul3 via its first BTB domain—to promote ubiquitination and proteasomal degradation of substrates including Musashi-2 (MSI2); the Cul3-RHOBTB2 complex assembly is Hsp90-dependent, and disease-causing BTB-domain missense variants impair Cul3-mediated degradation of RHOBTB2 itself, causing protein accumulation with nuclear/mitochondrial localization, deregulated ion channel expression, and altered neuronal excitability, while tumor-suppressor functions are mediated through CCND1 downregulation, CXCL14 upregulation, BRMS1-dependent inhibition of migration/invasion, and E2F1-regulated apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RHOBTB2 (DBC2) is an atypical Rho GTPase that functions principally as a substrate-specific adaptor for Cul3-based E3 ubiquitin ligase complexes, coupling protein ubiquitination to control of cell proliferation, apoptosis, and neuronal excitability [#1, #9]. It binds the Cul3 scaffold through its first BTB domain and is itself a substrate of the Cul3 complex, undergoing proteasomal degradation; a cancer-derived missense mutant that fails to bind Cul3 escapes this regulation and accumulates [#1]. Assembly of the DBC2–Cul3–COP9 ligase is Hsp90-dependent, and DBC2 associates with Hsp90/Cdc37 while retaining GTP-binding capacity modulated by the Hsp90 ATPase cycle [#8]. As an adaptor, RHOBTB2 directs polyubiquitination and degradation of substrates including the RNA-binding oncoprotein Musashi-2 (MSI2), and DBC2 and MSI2 levels are inversely correlated in breast cancer [#9]. Its tumor-suppressor activity—first established by growth inhibition upon re-expression in DBC2-negative breast cancer cells [#0]—operates through downregulation of Cyclin D1 (CCND1) as an essential step [#4], upregulation of CXCL14 [#6] and the metastasis suppressor BRMS1 with decreased phospho-ezrin and phospho-Akt2 to inhibit migration/invasion [#10], and E2F1-dependent transcriptional induction during apoptosis, where RHOBTB2 is a direct E2F1 target whose knockdown delays drug-induced apoptosis [#3]. De novo BTB-domain missense variants impair Cul3-dependent degradation of RHOBTB2, causing protein accumulation with nuclear and mitochondrial localization, downregulation of ion channel genes, and altered neuronal excitability—a phenotype distinct from complete loss of RHOBTB2 and validated by a genetic interaction with the SCN1A ortholog paralytic in Drosophila [#11, #12].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established RHOBTB2/DBC2 as a functional tumor suppressor by showing re-expression inhibits growth in cancer cells that have lost it, while a cancer-derived mutant cannot.\",\n      \"evidence\": \"Ectopic expression in DBC2-negative breast cancer cells with WT vs somatic mutant comparison and growth assays\",\n      \"pmids\": [\"12370419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular mechanism for growth suppression identified\", \"Single cell-context, no in vivo validation\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the core biochemical activity: RHOBTB2 binds the Cul3 ligase scaffold via its first BTB domain and is itself a Cul3 ubiquitination substrate, with a cancer mutant escaping this regulation.\",\n      \"evidence\": \"Co-IP, in vitro and in vivo ubiquitination assays, BTB1 domain mapping, cancer-mutant analysis\",\n      \"pmids\": [\"15107402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify substrates other than RHOBTB2 itself\", \"Structural basis of BTB–Cul3 interaction not resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked RHOBTB2 to microtubule-dependent ER-to-Golgi vesicular transport, broadening its cellular role beyond ubiquitination.\",\n      \"evidence\": \"siRNA knockdown in 293 cells with VSVG-GFP transport assay and microtubule disruption\",\n      \"pmids\": [\"17023000\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism connecting RHOBTB2 to transport unknown\", \"No identified transport machinery partner\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected RHOBTB2 to cell-cycle and apoptotic transcriptional control, showing it is a direct E2F1 target required for timely drug-induced apoptosis.\",\n      \"evidence\": \"E2F1 overexpression with cycloheximide, E2F1 and RHOBTB2 siRNA, cell-cycle and apoptosis assays\",\n      \"pmids\": [\"18039672\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pro-apoptotic effector mechanism downstream of RHOBTB2 not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified CCND1 downregulation as an essential, non-bypassable step in DBC2-mediated growth suppression.\",\n      \"evidence\": \"DBC2 expression with CCND1/CCNE1 overexpression rescue and proliferation assays; inducible expression with MG132 in resistant cells\",\n      \"pmids\": [\"17517369\", \"17617377\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CCND1 is a direct RHOBTB2 ubiquitination target unresolved\", \"Mechanism of resistance via proteasomal DBC2 destruction not fully mapped\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Expanded the downstream gene network by identifying CXCL14 as a RHOBTB2-regulated target restored upon re-expression in carcinoma cells.\",\n      \"evidence\": \"siRNA in primary epithelial cells, microarray, CXCL14 secretion assay, re-expression in HNSCC lines\",\n      \"pmids\": [\"18762809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CXCL14 regulation is transcriptional or via ubiquitination is unclear\", \"Causal link to tumor suppression not formally tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined an anti-metastatic mechanism in which RHOBTB2 upregulates BRMS1 and dampens ezrin/Akt2 signaling to block migration and invasion.\",\n      \"evidence\": \"Ectopic RHOBTB2 expression, BRMS1 siRNA rescue, Transwell assays, phospho-protein Western blots\",\n      \"pmids\": [\"20930524\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking RHOBTB2 to BRMS1 upregulation unknown\", \"Single cell-line system\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established that DBC2–Cul3–COP9 ligase assembly is Hsp90/Cdc37-dependent and that DBC2 GTP binding is coupled to the Hsp90 ATPase cycle.\",\n      \"evidence\": \"Pull-downs, GTP-binding assays, geldanamycin/molybdate modulation, complex co-IP in reticulocyte lysate and MCF7 cells\",\n      \"pmids\": [\"24608665\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of GTP binding for adaptor activity not defined\", \"No GTPase cycling regulators identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined RHOBTB2 as a substrate-receptor adaptor with a bona fide degradation target, MSI2, linking its ubiquitin-ligase function to suppression of oncogenic signaling.\",\n      \"evidence\": \"Genome-wide cDNA in vitro ubiquitination screen, DBC2–MSI2 co-IP, overexpression/knockdown, degradation assays, IHC tissue microarray\",\n      \"pmids\": [\"27941885\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Degron on MSI2 recognized by RHOBTB2 not mapped\", \"Other substrates from the screen not characterized\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mechanistically distinguished disease-causing BTB-domain variants—which impair Cul3-mediated self-degradation, accumulate in nucleus/mitochondria, and deregulate ion channels to alter neuronal excitability—from loss of function and GTPase-domain variants.\",\n      \"evidence\": \"Co-expression of CUL3 with WT vs mutants in Neuro-2a; Drosophila RNA-seq and paralytic genetic interaction; iPSC-neuron patch-clamp; inducible cell model with lysosome inhibitor experiments\",\n      \"pmids\": [\"29768694\", \"39849855\", \"41478322\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ion-channel substrate relationship vs transcriptional effect not separated\", \"Mechanism of mitochondrial localization unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a context-dependent stabilizing role in AML, where RHOBTB2 binds and protects KLHL13 from degradation to drive proliferation via Hippo-YAP1.\",\n      \"evidence\": \"RHOBTB2–KLHL13 co-IP, siRNA, MG132 rescue, proliferation/migration/apoptosis assays\",\n      \"pmids\": [\"41107424\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How RHOBTB2 stabilizes rather than degrades KLHL13 is unexplained\", \"Reconciliation with tumor-suppressor role in other cancers absent\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RHOBTB2 selects between its degradative adaptor function and protein-stabilizing role, and the rules governing substrate recognition across tissues, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of substrate engagement\", \"Determinants of context-specific tumor-suppressor vs oncogenic behavior unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 9]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 9]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 9]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"complexes\": [\"Cul3-RHOBTB2 E3 ubiquitin ligase\", \"DBC2–Cul3–COP9 signalosome complex\"],\n    \"partners\": [\"CUL3\", \"MSI2\", \"HSP90\", \"CDC37\", \"KLHL13\", \"E2F1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}