{"gene":"HOXB3","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":1997,"finding":"HOXB3 overexpression in murine bone marrow cells via retroviral gene transfer caused defective lymphoid development (reduced CD4+CD8+ thymocytes, absent IL-7-responsive pre-B progenitors) and progressive myeloproliferation (elevated granulocyte macrophage colony-forming cells), establishing a direct role for HOXB3 in hematopoietic proliferation and differentiation.","method":"Retroviral gene transfer into murine bone marrow; transplantation into mice; flow cytometry and colony assays","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean gain-of-function in vivo model with multiple orthogonal readouts (T-cell, B-cell, myeloid lineages), replicated across multiple recipients","pmids":["9052833"],"is_preprint":false},{"year":1997,"finding":"The kreisler protein (Krml1), a Maf/bZIP transcription factor expressed in rhombomeres 5 and 6, directly binds two conserved sequence blocks (19 bp and 45 bp) in the Hoxb3 r5 enhancer and activates Hoxb3 transcription in r5, with an Ets-related activation site also required for both activation and r5 restriction.","method":"Transgenic reporter analysis; in vitro binding assays; deletion/mutational analysis of enhancer elements","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding plus transgenic functional validation in multiple species (mouse, chick), replicated in subsequent independent study (PMID:9895323)","pmids":["9144291"],"is_preprint":false},{"year":1999,"finding":"Hoxa3, like its paralog Hoxb3, is a direct transcriptional target of kreisler (Krml1) in the hindbrain; a single high-affinity Krml1 binding site in the Hoxa3 r5/r6 enhancer is necessary and sufficient for kreisler-dependent activation, but the number and arrangement of binding sites differ between Hoxa3 and Hoxb3 enhancers, accounting for their distinct segmental restriction (r5/r6 vs. r5 only).","method":"Transgenic analysis; deletion analysis; ectopic kreisler expression; kreisler-null embryo analysis","journal":"Development","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct binding site mutagenesis, genetic loss-of-function, and ectopic expression all convergent; independent replication of kreisler→Hoxb3 mechanism","pmids":["9895323"],"is_preprint":false},{"year":1998,"finding":"HOXB3-induced cellular transformation and proliferation of Rat-1 cells requires cooperation with PBX1; the conserved tetrapeptide (mediating PBX binding) and homeodomain (mediating DNA binding) are both required for transforming activity, and modulating PBX1 levels strongly modulates HOXB3 transforming capacity.","method":"Rat-1 cell transformation assay; co-transfection with PBX1; deletion/point mutations of tetrapeptide and homeodomain","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — functional transformation assay with domain mutagenesis and PBX1 modulation, multiple orthogonal approaches in one study","pmids":["9692548"],"is_preprint":false},{"year":1998,"finding":"HOXB1, HOXB2, and HOXB3 proteins all positively regulate a 534-bp upstream fragment of the Otx2 gene in embryonal carcinoma cells; HOXB3 (homeodomain-containing bacterial extract) binds to palindromic TAATTA sites within this fragment, and this binding region is necessary for Otx2 up-regulation.","method":"Co-transfection reporter assay; EMSA with recombinant HOXB3 homeodomain; nuclear extract binding assays","journal":"Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro binding confirmed by EMSA with mutagenesis of binding sites, but single lab and limited in vivo validation","pmids":["9556594"],"is_preprint":false},{"year":2002,"finding":"Krox20 (expressed in r3 and r5) is required for activity of the Hoxb3 r5 enhancer (but not the Hoxa3 r5/r6 enhancer); Krox20 binds the Hoxb3 r5 enhancer and synergizes with kreisler to restrict expression to r5 (the overlap domain of both factors), as shown by genetic analysis in Krox20-null embryos and ectopic Krox20 expression.","method":"Genetic analysis (Krox20-null mice); ectopic expression; mutational analysis of enhancer; EMSA","journal":"EMBO Journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic epistasis in null mice plus ectopic expression plus enhancer mutagenesis plus in vitro binding, multiple orthogonal methods","pmids":["11823429"],"is_preprint":false},{"year":2001,"finding":"Multiple widely-spaced cis-acting regulatory elements (Ib, IIIa, IVa, IVb, Va) within and flanking the Hoxb3 locus control distinct tissue- and stage-specific expression domains in a modular, additive manner; element IVa (r5 enhancer) controls anterior neural expression in r5, element IIIa directs anterior spinal cord/hindbrain to r6, region A/element I mediates posterior neural expression, and element Va controls mesoderm-specific expression.","method":"Transgenic lacZ reporter analysis with multiple DNA fragments; combinatorial element testing","journal":"Developmental Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic transgenic reporter dissection with multiple elements tested independently and in combination, single lab","pmids":["11254356"],"is_preprint":false},{"year":2002,"finding":"Hoxb3 auto/cross-regulates its own expression in the neural tube: within the 482-bp element IIIa, two Hox binding sites are bound in vitro by both Hoxb3 and Hoxb4 proteins; a novel GCCAGGC motif is also required; kreisler binding sites in this element are not required for r6 or neural crest expression.","method":"Transgenic analysis; in vitro binding (EMSA); deletion/mutational analysis of element IIIa","journal":"Developmental Biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro binding confirmed plus transgenic functional validation, but auto-regulation mechanistic link is indirect; single lab","pmids":["12482716"],"is_preprint":false},{"year":2003,"finding":"Mice deficient in both Hoxb3 and Hoxb4 display reduced hematopoietic stem cell (HSC) pool in fetal liver, diminished progenitor numbers, impaired proliferative capacity of Lin-Sca1+c-kit+ progenitors in vitro, reduced in vivo repopulating capability, and slower cell cycle kinetics without perturbing lineage commitment, indicating that Hoxb3 and Hoxb4 cooperate to regulate HSC proliferation and self-renewal.","method":"Double-knockout mouse model; competitive repopulation assay; in vitro colony assay; flow cytometry; cytostatic drug treatment","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with multiple orthogonal readouts (in vitro proliferation, in vivo repopulation, cell cycle kinetics)","pmids":["12748289"],"is_preprint":false},{"year":2000,"finding":"The Polycomb group protein rae28 is required for maintenance (but not establishment) of Hoxb3 expression boundaries; rae28-deficient mice show ectopic anterior extension of Hoxb3 expression in hindbrain and pharyngeal arch despite normal kreisler and Krox20 expression, indicating rae28 restricts Hoxb3 expression domain post-establishment.","method":"rae28-knockout mouse analysis; in situ hybridization for Hoxb3, kreisler, Krox20, p75; temporal expression analysis","journal":"Mechanisms of Development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with temporal resolution and marker controls distinguishing establishment from maintenance, single lab","pmids":["11044623"],"is_preprint":false},{"year":2005,"finding":"The Hoxb3 cis-element b3IIIa functions as a vagal neural crest-specific enhancer that directs expression in vagal (but not trunk or sacral) neural crest, marks a subset of enteric neuroblasts, and is maintained in differentiated myenteric plexus neurons; in Dom mutant mice (Hirschsprung's model), colonization of b3IIIa-expressing cells in large intestine was incomplete.","method":"Transgenic lacZ reporter analysis; cellular marker co-localization; genetic cross with Dom mutant mice","journal":"Developmental Dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic reporter with cellular markers and genetic validation in disease model, single lab","pmids":["15768390"],"is_preprint":false},{"year":2007,"finding":"Hoxb3-deficient mice develop age-dependent impairment of B lymphopoiesis: by 6 months, Hoxb3-/- mice show reduced BM cellularity, twofold reduction in B220+CD43+ progenitor B cells, fivefold reduction in B220+CD43-IgM- precursor B cells, reduced IL-7 receptor expression on progenitor B cells, and impaired IL-7-driven proliferation in vitro.","method":"Hoxb3 knockout mouse analysis; flow cytometry; in vitro IL-7 stimulation proliferation assay; IL-7R expression analysis","journal":"Experimental Hematology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with multiple orthogonal readouts (phenotype, receptor expression, functional proliferation assay) linking Hoxb3 to IL-7R-dependent B lymphopoiesis","pmids":["17309827"],"is_preprint":false},{"year":2009,"finding":"HOXB3 epigenetically silences RASSF1A tumor suppressor by binding to and transcriptionally activating the DNMT3B promoter; DNMT3B is then recruited to the RASSF1A promoter via interactions with Polycomb repressor complex 2 and MYC, resulting in hypermethylation and silencing of RASSF1A; HOXB3 oncogenic activity in xenograft models is partly dependent on RASSF1A silencing.","method":"Genome-wide shRNA screen; ChIP; bisulfite sequencing; reporter assays; shRNA knockdown; mouse xenograft experiments","journal":"Molecular Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — genome-wide screen identified HOXB3, validated by ChIP, methylation analysis, rescue experiments, and in vivo xenograft; multiple orthogonal methods","pmids":["19854132"],"is_preprint":false},{"year":2011,"finding":"Hoxb3 directly represses Hoxb1 transcription by binding to a novel site S3 on the Hoxb1 locus; EMSA confirmed protein-DNA interaction in vitro; in vivo ChIP in P19 cells and hindbrain tissues from Hoxb3(Tg) mutant confirmed occupancy; luciferase reporter assay in chick demonstrated transcriptional suppression; in wildtype E10.5 caudal hindbrain (where Hoxb1 is absent), Hoxb3 occupies the S3 site.","method":"EMSA; in vivo ChIP; luciferase reporter assay (chick in ovo); gain-of-function transgenic mouse","journal":"Developmental Biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct binding confirmed by EMSA and in vivo ChIP, functional repression by luciferase assay, genetic phenocopy of Hoxb1 null, multiple orthogonal methods","pmids":["21320481"],"is_preprint":false},{"year":2012,"finding":"HoxB3 promotes prostate cancer cell proliferation and migration by transcriptionally activating CDCA3; ChIP analysis showed HoxB3 binds the CDCA3 promoter; depletion of HoxB3 decreased proliferation in a CDCA3-dependent manner both in vitro and in vivo.","method":"ChIP; shRNA knockdown; overexpression; xenograft in vivo; proliferation/migration assays","journal":"Cancer Letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrates direct promoter binding, CDCA3-dependence confirmed by rescue experiment, single lab","pmids":["23219899"],"is_preprint":false},{"year":2015,"finding":"HOXB3 overexpression in mouse pro-B cells decreased FLT3-ITD-dependent cell proliferation and colony formation, increased apoptosis, and significantly reduced FLT3-ITD-induced phosphorylation of AKT, ERK, p38, and STAT5, indicating HOXB3 acts as a suppressor of FLT3-ITD oncogenic signaling.","method":"Overexpression in mouse pro-B cells; colony formation assay; Western blot for phospho-AKT, phospho-ERK, phospho-p38, phospho-STAT5; apoptosis assay","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cellular assays with signaling pathway readouts, single lab, no direct binding between HOXB3 and FLT3 pathway demonstrated","pmids":["26482852"],"is_preprint":false},{"year":2018,"finding":"HOXB3 drives leukemogenesis partly by transcriptionally activating CDCA3 (confirmed by knockdown reducing CDCA3 and cell proliferation) and inducing DNMT3B expression; DNMT3B then methylates the pre-miR-375 promoter to silence miR-375, creating a HOXB3→DNMT3B→miR-375 feedback loop that sustains HOXB3 expression; miR-375 directly targets HOXB3 3'-UTR (luciferase reporter).","method":"Luciferase reporter assay for miR-375/HOXB3 3'-UTR; shRNA knockdown; colony formation; xenograft; bisulfite sequencing of pre-miR-375 promoter","journal":"BMC Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (luciferase, methylation, rescue, xenograft), single lab","pmids":["29439669"],"is_preprint":false},{"year":2021,"finding":"Hoxb3 directly regulates Jag1 expression in pharyngeal epithelium: molecular experiments showed Hoxb3 binds to an upstream genomic site S2 on the Jag1 locus; ectopic Hoxb3 in Hoxb3(Tg) mutant specifically upregulated Jag1 in ectodermal pharyngeal epithelial cells of PA2; elevated Jag1 led to abnormal cellular interaction and deficiency of neural crest cells migrating into PA2.","method":"ChIP/molecular binding assay; gain-of-function transgenic mouse; in situ hybridization; cellular migration analysis","journal":"Frontiers in Physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding to Jag1 genomic site demonstrated, functional consequence in transgenic model, single lab","pmids":["33505317"],"is_preprint":false},{"year":2023,"finding":"In castration-resistant prostate cancer (CRPC), WNT3A signaling and APC deficiency cause HOXB3 to dissociate from the destruction complex and translocate to the nucleus, where it transcriptionally activates multiple WNT pathway genes; HOXB3 suppression reduced proliferation in APC-downregulated CRPC cells and re-sensitized APC-deficient CRPC xenografts to abiraterone.","method":"RNA sequencing; WNT3A treatment; APC knockdown; nuclear fractionation/localization; xenograft assays; proliferation assays","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays with mechanistic pathway placement, single lab; localization tied to functional consequence","pmids":["36973255"],"is_preprint":false},{"year":2023,"finding":"HOXB3 transcriptionally activates Notch1 by binding to its promoter (confirmed by luciferase reporter and ChIP assays); this promotes Wnt/β-catenin pathway activation and trophoblast cell proliferation, migration, and invasion; Notch1 knockdown abrogated HOXB3 functions in trophoblasts.","method":"Luciferase reporter assay; ChIP; siRNA knockdown; cell proliferation/migration/invasion assays; rat PE model","journal":"European Journal of Pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct promoter binding confirmed by two methods (luciferase, ChIP), epistasis via Notch1 knockdown rescue, single lab","pmids":["37652291"],"is_preprint":false},{"year":2024,"finding":"STUB1 (an E3 ubiquitin ligase) mediates ubiquitination and degradation of HOXB3; HOXB3 in turn transcriptionally activates PARK7 by binding to its promoter; the STUB1→HOXB3→PARK7 axis regulates ferroptosis and paclitaxel resistance in ovarian cancer cells.","method":"Co-immunoprecipitation; dual luciferase reporter assay; RT-qPCR; western blot; overexpression/knockdown rescue experiments; xenograft","journal":"Communications Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for protein interaction, luciferase for direct transcriptional activation, rescue experiments for pathway epistasis, single lab","pmids":["39501077"],"is_preprint":false},{"year":2024,"finding":"SIRT5 desuccinylates HOXB3 as a post-translational modification, suppressing HOXB3 activity; SIRT5 inhibition increases trophoblast proliferation, invasion, and migration through HOXB3-dependent Notch and β-catenin signaling pathway activation; silencing HOXB3 reversed these effects.","method":"Co-immunoprecipitation; dual-luciferase reporter assay; siRNA knockdown rescue; proliferation/invasion/migration assays in HTR-8/SVneo cells","journal":"Journal of Assisted Reproduction and Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP confirmed SIRT5-HOXB3 interaction and desuccinylation, rescue experiments establish epistasis, single lab","pmids":["39145876"],"is_preprint":false},{"year":2025,"finding":"HOXB3 forms phase-separated condensates in a subset of glioblastoma cells through its intrinsically disordered regions and interactions with RUNX1; these condensates drive oncogenic transcription at super-enhancer-associated sites; a peptide (P621-R9) disrupting HOXB3 condensation altered chromatin structure, reduced super-enhancer-driven transcription, and selectively diminished tumorigenic potential in GBM patient-derived xenograft models with HOXB3 condensates.","method":"Single-cell CUT&Tag (H3K27ac); condensate/phase separation analysis; peptide disruption assay; patient-derived xenograft models; chromatin structure analysis","journal":"Nature Cell Biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-cell chromatin profiling combined with functional condensate disruption and selective in vivo efficacy in patient-derived xenograft models; multiple orthogonal methods in one rigorous study","pmids":["41028837"],"is_preprint":false}],"current_model":"HOXB3 is a homeodomain transcription factor that directly binds DNA at ATTA-core and other motifs to regulate downstream targets (CDCA3, DNMT3B, RASSF1A, Otx2, Hoxb1, Jag1, Notch1, PARK7, WNT pathway genes) and whose activity is modulated by cooperative interactions with kreisler/Krml1, Krox20, PBX1, and RUNX1, by Polycomb-mediated repression (rae28), by SIRT5-mediated desuccinylation, and by STUB1-mediated ubiquitination; in hematopoiesis it promotes HSC proliferation and B lymphopoiesis, in development it patterns hindbrain rhombomeres and neural crest via cross-regulatory Hox networks, and in cancer it can act either as an oncogenic driver (via DNMT3B-mediated epigenetic silencing and WNT/CDCA3 activation) or as a tumor suppressor depending on cellular context."},"narrative":{"mechanistic_narrative":"HOXB3 is a homeodomain transcription factor that patterns the vertebrate hindbrain, governs hematopoietic stem and progenitor cell behavior, and acts as a context-dependent oncogenic driver by directly binding DNA and regulating downstream target genes [PMID:9052833, PMID:19854132, PMID:21320481]. During hindbrain development, Hoxb3 expression is established by direct binding of the Maf/bZIP factor kreisler/Krml1 to conserved blocks in an r5 enhancer, with Krox20 synergizing to restrict expression to rhombomere 5, while a separate set of modular cis-elements directs neural, neural crest, and mesodermal domains [PMID:9144291, PMID:11823429, PMID:11254356]; one of these (b3IIIa) is a vagal neural-crest enhancer relevant to enteric nervous system colonization [PMID:15768390]. HOXB3 participates in cross-regulatory Hox networks, binding its own and paralog loci—repressing Hoxb1 through a discrete S3 site and being bound at element IIIa by both Hoxb3 and Hoxb4 [PMID:12482716, PMID:21320481]. Its expression boundaries are maintained post-establishment by the Polycomb-group protein rae28 [PMID:11044623]. In hematopoiesis, HOXB3 promotes progenitor proliferation: overexpression drives myeloproliferation and impairs lymphoid development, Hoxb3/Hoxb4 double-knockout mice show a reduced and slow-cycling HSC pool, and Hoxb3-deficient mice develop age-dependent defects in IL-7-dependent B lymphopoiesis [PMID:9052833, PMID:12748289, PMID:17309827]. In cancer, HOXB3 acts oncogenically by transcriptionally activating DNMT3B, which silences the RASSF1A tumor suppressor and miR-375 (a self-sustaining feedback loop), and by activating CDCA3, Notch1, and WNT pathway genes to drive proliferation, migration, and invasion [PMID:19854132, PMID:23219899, PMID:29439669, PMID:37652291]; in castration-resistant prostate cancer, WNT3A and APC loss release HOXB3 from the destruction complex to enter the nucleus and activate WNT targets [PMID:36973255]. Transforming activity requires cooperation with PBX1 via its conserved tetrapeptide and homeodomain [PMID:9692548]. HOXB3 activity is further tuned by post-translational control—STUB1-mediated ubiquitination and degradation (with HOXB3 activating PARK7 to regulate ferroptosis) and SIRT5-mediated desuccinylation [PMID:39501077, PMID:39145876]—and in glioblastoma it forms phase-separated condensates through its intrinsically disordered regions and RUNX1 interaction that drive super-enhancer-associated oncogenic transcription [PMID:41028837].","teleology":[{"year":1997,"claim":"Established that HOXB3 directly controls hematopoietic proliferation and lineage output, defining its physiological role in blood formation.","evidence":"Retroviral overexpression in murine bone marrow with transplantation, flow cytometry and colony assays","pmids":["9052833"],"confidence":"High","gaps":["Did not identify direct transcriptional targets mediating the proliferative effect","Gain-of-function may not reflect endogenous dosage"]},{"year":1997,"claim":"Identified the upstream activator of Hoxb3 in the hindbrain, showing kreisler/Krml1 directly binds the r5 enhancer to drive segmental expression.","evidence":"Transgenic reporter analysis with in vitro binding and enhancer mutagenesis","pmids":["9144291"],"confidence":"High","gaps":["Did not establish the full combinatorial logic restricting expression to r5","Role of the required Ets site not assigned to a specific factor"]},{"year":1999,"claim":"Confirmed kreisler as a conserved direct regulator of Hox group 3 paralogs and showed enhancer architecture determines distinct segmental boundaries.","evidence":"Transgenic, deletion, ectopic expression and kreisler-null analysis of Hoxa3/Hoxb3 enhancers","pmids":["9895323"],"confidence":"High","gaps":["Did not address downstream targets of group 3 Hox in r5/r6"]},{"year":1998,"claim":"Demonstrated HOXB3 transforming activity depends on cofactor PBX1, defining a cooperative DNA-binding requirement for oncogenic function.","evidence":"Rat-1 transformation assay with tetrapeptide/homeodomain mutagenesis and PBX1 modulation","pmids":["9692548"],"confidence":"High","gaps":["Did not identify the target genes through which HOXB3/PBX1 drive transformation"]},{"year":1998,"claim":"Provided early evidence that HOXB3 binds defined TAATTA motifs to activate a developmental target gene (Otx2).","evidence":"Reporter assays and EMSA with recombinant HOXB3 homeodomain in embryonal carcinoma cells","pmids":["9556594"],"confidence":"Medium","gaps":["In vivo relevance of Otx2 regulation not established","Single lab, limited functional validation"]},{"year":2000,"claim":"Distinguished establishment from maintenance of Hoxb3 boundaries, assigning Polycomb (rae28) to long-term domain restriction.","evidence":"rae28-knockout mouse with in situ hybridization and temporal expression analysis","pmids":["11044623"],"confidence":"Medium","gaps":["Mechanism of rae28 recruitment to Hoxb3 not defined","Single lab"]},{"year":2001,"claim":"Mapped the modular cis-regulatory architecture of the Hoxb3 locus, assigning separable elements to distinct tissue/stage expression domains.","evidence":"Transgenic lacZ reporter dissection of multiple DNA fragments alone and in combination","pmids":["11254356"],"confidence":"Medium","gaps":["Trans-acting factors for several elements not identified","Single lab"]},{"year":2002,"claim":"Defined the combinatorial logic restricting Hoxb3 to r5, showing Krox20 synergizes with kreisler at the r5 enhancer.","evidence":"Krox20-null genetics, ectopic expression, enhancer mutagenesis and EMSA","pmids":["11823429"],"confidence":"High","gaps":["Did not resolve how synergy is biochemically achieved at the enhancer"]},{"year":2002,"claim":"Revealed Hox auto/cross-regulation, with Hoxb3 and Hoxb4 binding element IIIa to control neural-tube expression independent of kreisler sites.","evidence":"Transgenic analysis with EMSA and deletion/mutational dissection of element IIIa","pmids":["12482716"],"confidence":"Medium","gaps":["Direct autoregulatory link is indirect","Identity of GCCAGGC-binding factor unknown"]},{"year":2003,"claim":"Showed Hoxb3 and Hoxb4 cooperate to sustain the HSC pool through proliferation/self-renewal rather than lineage commitment.","evidence":"Double-knockout mice with competitive repopulation, colony assays, cell-cycle kinetics","pmids":["12748289"],"confidence":"High","gaps":["Direct transcriptional targets in HSCs not identified","Individual contribution of Hoxb3 vs Hoxb4 not separated"]},{"year":2005,"claim":"Identified the b3IIIa element as a vagal neural-crest enhancer with relevance to enteric nervous system colonization.","evidence":"Transgenic lacZ reporter with cellular markers and Dom (Hirschsprung model) genetic cross","pmids":["15768390"],"confidence":"Medium","gaps":["Causal role of HOXB3 itself in Hirschsprung phenotype not established","Single lab"]},{"year":2007,"claim":"Established a non-redundant role for endogenous Hoxb3 in IL-7-dependent B lymphopoiesis, refining its hematopoietic function.","evidence":"Hoxb3 knockout mice with flow cytometry, IL-7R analysis and IL-7 proliferation assays","pmids":["17309827"],"confidence":"High","gaps":["Whether Hoxb3 directly regulates IL-7R transcription not shown"]},{"year":2009,"claim":"Defined an oncogenic epigenetic mechanism whereby HOXB3 activates DNMT3B to silence the RASSF1A tumor suppressor.","evidence":"Genome-wide shRNA screen, ChIP, bisulfite sequencing, rescue and xenograft experiments","pmids":["19854132"],"confidence":"High","gaps":["Did not address context-dependent tumor-suppressive roles of HOXB3"]},{"year":2011,"claim":"Demonstrated direct Hoxb3-mediated repression of Hoxb1 via a discrete site, extending cross-regulatory Hox network function in the hindbrain.","evidence":"EMSA, in vivo ChIP, luciferase reporter and gain-of-function transgenic mouse","pmids":["21320481"],"confidence":"High","gaps":["Cofactors at the S3 site not defined"]},{"year":2012,"claim":"Identified CDCA3 as a direct HOXB3 target driving prostate cancer proliferation and migration.","evidence":"ChIP, shRNA, overexpression, xenograft and proliferation/migration assays","pmids":["23219899"],"confidence":"Medium","gaps":["Single lab","Generality across tumor types not established at this stage"]},{"year":2015,"claim":"Revealed a tumor-suppressive facet of HOXB3, antagonizing FLT3-ITD oncogenic signaling in pro-B cells.","evidence":"Overexpression in mouse pro-B cells with phospho-signaling Western blots and apoptosis/colony assays","pmids":["26482852"],"confidence":"Medium","gaps":["No direct molecular link between HOXB3 and FLT3 pathway demonstrated","Single lab"]},{"year":2018,"claim":"Connected HOXB3 oncogenic outputs into a self-sustaining DNMT3B-miR-375 feedback loop in leukemia.","evidence":"Luciferase 3'-UTR reporter, bisulfite sequencing, shRNA, colony and xenograft assays","pmids":["29439669"],"confidence":"Medium","gaps":["Single lab","Relative contribution of CDCA3 vs DNMT3B arms not quantified"]},{"year":2021,"claim":"Showed Hoxb3 directly regulates Jag1 in pharyngeal epithelium, linking it to neural crest migration via Notch ligand control.","evidence":"Binding assay at Jag1 site S2, gain-of-function transgenic mouse, in situ hybridization, migration analysis","pmids":["33505317"],"confidence":"Medium","gaps":["Single lab","Endogenous loss-of-function effect on Jag1 not tested"]},{"year":2023,"claim":"Placed HOXB3 within WNT signaling as a destruction-complex-regulated transcription factor in castration-resistant prostate cancer.","evidence":"RNA-seq, WNT3A treatment, APC knockdown, nuclear fractionation and xenograft assays","pmids":["36973255"],"confidence":"Medium","gaps":["Direct WNT target genes activated by HOXB3 not individually validated","Single lab"]},{"year":2023,"claim":"Identified Notch1 as a direct HOXB3 target driving Wnt/β-catenin-dependent trophoblast proliferation and invasion.","evidence":"Luciferase reporter, ChIP, siRNA rescue and invasion assays plus a rat preeclampsia model","pmids":["37652291"],"confidence":"Medium","gaps":["Single lab","In vivo human relevance limited"]},{"year":2024,"claim":"Established post-translational control of HOXB3 stability by STUB1 and a downstream PARK7 axis governing ferroptosis and drug resistance.","evidence":"Co-IP, dual luciferase, knockdown/overexpression rescue and xenograft in ovarian cancer","pmids":["39501077"],"confidence":"Medium","gaps":["Ubiquitination sites on HOXB3 not mapped","Single lab"]},{"year":2024,"claim":"Identified SIRT5-mediated desuccinylation as a suppressive post-translational modification of HOXB3 activity in trophoblasts.","evidence":"Co-IP, dual-luciferase, siRNA rescue and invasion/migration assays in HTR-8/SVneo cells","pmids":["39145876"],"confidence":"Medium","gaps":["Specific desuccinylated residues not defined","Single lab"]},{"year":2025,"claim":"Revealed that HOXB3 can drive oncogenic transcription through RUNX1-dependent phase-separated condensates at super-enhancers, offering a targetable mechanism.","evidence":"Single-cell CUT&Tag, condensate analysis, peptide disruption and patient-derived xenografts in glioblastoma","pmids":["41028837"],"confidence":"High","gaps":["Generality of condensate behavior beyond GBM subset unknown","How condensate formation integrates with cofactors like PBX1 not addressed"]},{"year":null,"claim":"The molecular basis determining whether HOXB3 acts as an oncogenic driver versus a tumor suppressor in a given cellular context remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model reconciling oncogenic (DNMT3B/WNT/CDCA3) and suppressive (FLT3-ITD) outputs","Cofactor and PTM combinations that switch HOXB3 output not systematically defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[4,13,14,19]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[12,13,14,19,20]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[18]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,5,6,13,17]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[12,13,14,19]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,18,22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[18,19,15]}],"complexes":[],"partners":["PBX1","RUNX1","STUB1","SIRT5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P14651","full_name":"Homeobox protein Hox-B3","aliases":["Homeobox protein Hox-2.7","Homeobox protein Hox-2G"],"length_aa":431,"mass_kda":44.3,"function":"Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P14651/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HOXB3","classification":"Not Classified","n_dependent_lines":59,"n_total_lines":1208,"dependency_fraction":0.048841059602649006},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HOXB3","total_profiled":1310},"omim":[{"mim_id":"618066","title":"HOMEOBOX B CLUSTER ANTISENSE RNA 1, NONCODING; HOXBAS1","url":"https://www.omim.org/entry/618066"},{"mim_id":"616816","title":"HYPOTONIA, INFANTILE, WITH PSYCHOMOTOR RETARDATION; IHPMR","url":"https://www.omim.org/entry/616816"},{"mim_id":"605082","title":"RAS ASSOCIATION DOMAIN FAMILY PROTEIN 1; RASSF1","url":"https://www.omim.org/entry/605082"},{"mim_id":"601739","title":"MEIS HOMEOBOX 1; 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caused defective lymphoid development (reduced CD4+CD8+ thymocytes, absent IL-7-responsive pre-B progenitors) and progressive myeloproliferation (elevated granulocyte macrophage colony-forming cells), establishing a direct role for HOXB3 in hematopoietic proliferation and differentiation.\",\n      \"method\": \"Retroviral gene transfer into murine bone marrow; transplantation into mice; flow cytometry and colony assays\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean gain-of-function in vivo model with multiple orthogonal readouts (T-cell, B-cell, myeloid lineages), replicated across multiple recipients\",\n      \"pmids\": [\"9052833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The kreisler protein (Krml1), a Maf/bZIP transcription factor expressed in rhombomeres 5 and 6, directly binds two conserved sequence blocks (19 bp and 45 bp) in the Hoxb3 r5 enhancer and activates Hoxb3 transcription in r5, with an Ets-related activation site also required for both activation and r5 restriction.\",\n      \"method\": \"Transgenic reporter analysis; in vitro binding assays; deletion/mutational analysis of enhancer elements\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding plus transgenic functional validation in multiple species (mouse, chick), replicated in subsequent independent study (PMID:9895323)\",\n      \"pmids\": [\"9144291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Hoxa3, like its paralog Hoxb3, is a direct transcriptional target of kreisler (Krml1) in the hindbrain; a single high-affinity Krml1 binding site in the Hoxa3 r5/r6 enhancer is necessary and sufficient for kreisler-dependent activation, but the number and arrangement of binding sites differ between Hoxa3 and Hoxb3 enhancers, accounting for their distinct segmental restriction (r5/r6 vs. r5 only).\",\n      \"method\": \"Transgenic analysis; deletion analysis; ectopic kreisler expression; kreisler-null embryo analysis\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct binding site mutagenesis, genetic loss-of-function, and ectopic expression all convergent; independent replication of kreisler→Hoxb3 mechanism\",\n      \"pmids\": [\"9895323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"HOXB3-induced cellular transformation and proliferation of Rat-1 cells requires cooperation with PBX1; the conserved tetrapeptide (mediating PBX binding) and homeodomain (mediating DNA binding) are both required for transforming activity, and modulating PBX1 levels strongly modulates HOXB3 transforming capacity.\",\n      \"method\": \"Rat-1 cell transformation assay; co-transfection with PBX1; deletion/point mutations of tetrapeptide and homeodomain\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — functional transformation assay with domain mutagenesis and PBX1 modulation, multiple orthogonal approaches in one study\",\n      \"pmids\": [\"9692548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"HOXB1, HOXB2, and HOXB3 proteins all positively regulate a 534-bp upstream fragment of the Otx2 gene in embryonal carcinoma cells; HOXB3 (homeodomain-containing bacterial extract) binds to palindromic TAATTA sites within this fragment, and this binding region is necessary for Otx2 up-regulation.\",\n      \"method\": \"Co-transfection reporter assay; EMSA with recombinant HOXB3 homeodomain; nuclear extract binding assays\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro binding confirmed by EMSA with mutagenesis of binding sites, but single lab and limited in vivo validation\",\n      \"pmids\": [\"9556594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Krox20 (expressed in r3 and r5) is required for activity of the Hoxb3 r5 enhancer (but not the Hoxa3 r5/r6 enhancer); Krox20 binds the Hoxb3 r5 enhancer and synergizes with kreisler to restrict expression to r5 (the overlap domain of both factors), as shown by genetic analysis in Krox20-null embryos and ectopic Krox20 expression.\",\n      \"method\": \"Genetic analysis (Krox20-null mice); ectopic expression; mutational analysis of enhancer; EMSA\",\n      \"journal\": \"EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic epistasis in null mice plus ectopic expression plus enhancer mutagenesis plus in vitro binding, multiple orthogonal methods\",\n      \"pmids\": [\"11823429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Multiple widely-spaced cis-acting regulatory elements (Ib, IIIa, IVa, IVb, Va) within and flanking the Hoxb3 locus control distinct tissue- and stage-specific expression domains in a modular, additive manner; element IVa (r5 enhancer) controls anterior neural expression in r5, element IIIa directs anterior spinal cord/hindbrain to r6, region A/element I mediates posterior neural expression, and element Va controls mesoderm-specific expression.\",\n      \"method\": \"Transgenic lacZ reporter analysis with multiple DNA fragments; combinatorial element testing\",\n      \"journal\": \"Developmental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic transgenic reporter dissection with multiple elements tested independently and in combination, single lab\",\n      \"pmids\": [\"11254356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Hoxb3 auto/cross-regulates its own expression in the neural tube: within the 482-bp element IIIa, two Hox binding sites are bound in vitro by both Hoxb3 and Hoxb4 proteins; a novel GCCAGGC motif is also required; kreisler binding sites in this element are not required for r6 or neural crest expression.\",\n      \"method\": \"Transgenic analysis; in vitro binding (EMSA); deletion/mutational analysis of element IIIa\",\n      \"journal\": \"Developmental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro binding confirmed plus transgenic functional validation, but auto-regulation mechanistic link is indirect; single lab\",\n      \"pmids\": [\"12482716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mice deficient in both Hoxb3 and Hoxb4 display reduced hematopoietic stem cell (HSC) pool in fetal liver, diminished progenitor numbers, impaired proliferative capacity of Lin-Sca1+c-kit+ progenitors in vitro, reduced in vivo repopulating capability, and slower cell cycle kinetics without perturbing lineage commitment, indicating that Hoxb3 and Hoxb4 cooperate to regulate HSC proliferation and self-renewal.\",\n      \"method\": \"Double-knockout mouse model; competitive repopulation assay; in vitro colony assay; flow cytometry; cytostatic drug treatment\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with multiple orthogonal readouts (in vitro proliferation, in vivo repopulation, cell cycle kinetics)\",\n      \"pmids\": [\"12748289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The Polycomb group protein rae28 is required for maintenance (but not establishment) of Hoxb3 expression boundaries; rae28-deficient mice show ectopic anterior extension of Hoxb3 expression in hindbrain and pharyngeal arch despite normal kreisler and Krox20 expression, indicating rae28 restricts Hoxb3 expression domain post-establishment.\",\n      \"method\": \"rae28-knockout mouse analysis; in situ hybridization for Hoxb3, kreisler, Krox20, p75; temporal expression analysis\",\n      \"journal\": \"Mechanisms of Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with temporal resolution and marker controls distinguishing establishment from maintenance, single lab\",\n      \"pmids\": [\"11044623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The Hoxb3 cis-element b3IIIa functions as a vagal neural crest-specific enhancer that directs expression in vagal (but not trunk or sacral) neural crest, marks a subset of enteric neuroblasts, and is maintained in differentiated myenteric plexus neurons; in Dom mutant mice (Hirschsprung's model), colonization of b3IIIa-expressing cells in large intestine was incomplete.\",\n      \"method\": \"Transgenic lacZ reporter analysis; cellular marker co-localization; genetic cross with Dom mutant mice\",\n      \"journal\": \"Developmental Dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic reporter with cellular markers and genetic validation in disease model, single lab\",\n      \"pmids\": [\"15768390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Hoxb3-deficient mice develop age-dependent impairment of B lymphopoiesis: by 6 months, Hoxb3-/- mice show reduced BM cellularity, twofold reduction in B220+CD43+ progenitor B cells, fivefold reduction in B220+CD43-IgM- precursor B cells, reduced IL-7 receptor expression on progenitor B cells, and impaired IL-7-driven proliferation in vitro.\",\n      \"method\": \"Hoxb3 knockout mouse analysis; flow cytometry; in vitro IL-7 stimulation proliferation assay; IL-7R expression analysis\",\n      \"journal\": \"Experimental Hematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with multiple orthogonal readouts (phenotype, receptor expression, functional proliferation assay) linking Hoxb3 to IL-7R-dependent B lymphopoiesis\",\n      \"pmids\": [\"17309827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HOXB3 epigenetically silences RASSF1A tumor suppressor by binding to and transcriptionally activating the DNMT3B promoter; DNMT3B is then recruited to the RASSF1A promoter via interactions with Polycomb repressor complex 2 and MYC, resulting in hypermethylation and silencing of RASSF1A; HOXB3 oncogenic activity in xenograft models is partly dependent on RASSF1A silencing.\",\n      \"method\": \"Genome-wide shRNA screen; ChIP; bisulfite sequencing; reporter assays; shRNA knockdown; mouse xenograft experiments\",\n      \"journal\": \"Molecular Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genome-wide screen identified HOXB3, validated by ChIP, methylation analysis, rescue experiments, and in vivo xenograft; multiple orthogonal methods\",\n      \"pmids\": [\"19854132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Hoxb3 directly represses Hoxb1 transcription by binding to a novel site S3 on the Hoxb1 locus; EMSA confirmed protein-DNA interaction in vitro; in vivo ChIP in P19 cells and hindbrain tissues from Hoxb3(Tg) mutant confirmed occupancy; luciferase reporter assay in chick demonstrated transcriptional suppression; in wildtype E10.5 caudal hindbrain (where Hoxb1 is absent), Hoxb3 occupies the S3 site.\",\n      \"method\": \"EMSA; in vivo ChIP; luciferase reporter assay (chick in ovo); gain-of-function transgenic mouse\",\n      \"journal\": \"Developmental Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct binding confirmed by EMSA and in vivo ChIP, functional repression by luciferase assay, genetic phenocopy of Hoxb1 null, multiple orthogonal methods\",\n      \"pmids\": [\"21320481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HoxB3 promotes prostate cancer cell proliferation and migration by transcriptionally activating CDCA3; ChIP analysis showed HoxB3 binds the CDCA3 promoter; depletion of HoxB3 decreased proliferation in a CDCA3-dependent manner both in vitro and in vivo.\",\n      \"method\": \"ChIP; shRNA knockdown; overexpression; xenograft in vivo; proliferation/migration assays\",\n      \"journal\": \"Cancer Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrates direct promoter binding, CDCA3-dependence confirmed by rescue experiment, single lab\",\n      \"pmids\": [\"23219899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HOXB3 overexpression in mouse pro-B cells decreased FLT3-ITD-dependent cell proliferation and colony formation, increased apoptosis, and significantly reduced FLT3-ITD-induced phosphorylation of AKT, ERK, p38, and STAT5, indicating HOXB3 acts as a suppressor of FLT3-ITD oncogenic signaling.\",\n      \"method\": \"Overexpression in mouse pro-B cells; colony formation assay; Western blot for phospho-AKT, phospho-ERK, phospho-p38, phospho-STAT5; apoptosis assay\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cellular assays with signaling pathway readouts, single lab, no direct binding between HOXB3 and FLT3 pathway demonstrated\",\n      \"pmids\": [\"26482852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HOXB3 drives leukemogenesis partly by transcriptionally activating CDCA3 (confirmed by knockdown reducing CDCA3 and cell proliferation) and inducing DNMT3B expression; DNMT3B then methylates the pre-miR-375 promoter to silence miR-375, creating a HOXB3→DNMT3B→miR-375 feedback loop that sustains HOXB3 expression; miR-375 directly targets HOXB3 3'-UTR (luciferase reporter).\",\n      \"method\": \"Luciferase reporter assay for miR-375/HOXB3 3'-UTR; shRNA knockdown; colony formation; xenograft; bisulfite sequencing of pre-miR-375 promoter\",\n      \"journal\": \"BMC Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (luciferase, methylation, rescue, xenograft), single lab\",\n      \"pmids\": [\"29439669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Hoxb3 directly regulates Jag1 expression in pharyngeal epithelium: molecular experiments showed Hoxb3 binds to an upstream genomic site S2 on the Jag1 locus; ectopic Hoxb3 in Hoxb3(Tg) mutant specifically upregulated Jag1 in ectodermal pharyngeal epithelial cells of PA2; elevated Jag1 led to abnormal cellular interaction and deficiency of neural crest cells migrating into PA2.\",\n      \"method\": \"ChIP/molecular binding assay; gain-of-function transgenic mouse; in situ hybridization; cellular migration analysis\",\n      \"journal\": \"Frontiers in Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding to Jag1 genomic site demonstrated, functional consequence in transgenic model, single lab\",\n      \"pmids\": [\"33505317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In castration-resistant prostate cancer (CRPC), WNT3A signaling and APC deficiency cause HOXB3 to dissociate from the destruction complex and translocate to the nucleus, where it transcriptionally activates multiple WNT pathway genes; HOXB3 suppression reduced proliferation in APC-downregulated CRPC cells and re-sensitized APC-deficient CRPC xenografts to abiraterone.\",\n      \"method\": \"RNA sequencing; WNT3A treatment; APC knockdown; nuclear fractionation/localization; xenograft assays; proliferation assays\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays with mechanistic pathway placement, single lab; localization tied to functional consequence\",\n      \"pmids\": [\"36973255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HOXB3 transcriptionally activates Notch1 by binding to its promoter (confirmed by luciferase reporter and ChIP assays); this promotes Wnt/β-catenin pathway activation and trophoblast cell proliferation, migration, and invasion; Notch1 knockdown abrogated HOXB3 functions in trophoblasts.\",\n      \"method\": \"Luciferase reporter assay; ChIP; siRNA knockdown; cell proliferation/migration/invasion assays; rat PE model\",\n      \"journal\": \"European Journal of Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct promoter binding confirmed by two methods (luciferase, ChIP), epistasis via Notch1 knockdown rescue, single lab\",\n      \"pmids\": [\"37652291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"STUB1 (an E3 ubiquitin ligase) mediates ubiquitination and degradation of HOXB3; HOXB3 in turn transcriptionally activates PARK7 by binding to its promoter; the STUB1→HOXB3→PARK7 axis regulates ferroptosis and paclitaxel resistance in ovarian cancer cells.\",\n      \"method\": \"Co-immunoprecipitation; dual luciferase reporter assay; RT-qPCR; western blot; overexpression/knockdown rescue experiments; xenograft\",\n      \"journal\": \"Communications Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for protein interaction, luciferase for direct transcriptional activation, rescue experiments for pathway epistasis, single lab\",\n      \"pmids\": [\"39501077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SIRT5 desuccinylates HOXB3 as a post-translational modification, suppressing HOXB3 activity; SIRT5 inhibition increases trophoblast proliferation, invasion, and migration through HOXB3-dependent Notch and β-catenin signaling pathway activation; silencing HOXB3 reversed these effects.\",\n      \"method\": \"Co-immunoprecipitation; dual-luciferase reporter assay; siRNA knockdown rescue; proliferation/invasion/migration assays in HTR-8/SVneo cells\",\n      \"journal\": \"Journal of Assisted Reproduction and Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP confirmed SIRT5-HOXB3 interaction and desuccinylation, rescue experiments establish epistasis, single lab\",\n      \"pmids\": [\"39145876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HOXB3 forms phase-separated condensates in a subset of glioblastoma cells through its intrinsically disordered regions and interactions with RUNX1; these condensates drive oncogenic transcription at super-enhancer-associated sites; a peptide (P621-R9) disrupting HOXB3 condensation altered chromatin structure, reduced super-enhancer-driven transcription, and selectively diminished tumorigenic potential in GBM patient-derived xenograft models with HOXB3 condensates.\",\n      \"method\": \"Single-cell CUT&Tag (H3K27ac); condensate/phase separation analysis; peptide disruption assay; patient-derived xenograft models; chromatin structure analysis\",\n      \"journal\": \"Nature Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-cell chromatin profiling combined with functional condensate disruption and selective in vivo efficacy in patient-derived xenograft models; multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"41028837\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HOXB3 is a homeodomain transcription factor that directly binds DNA at ATTA-core and other motifs to regulate downstream targets (CDCA3, DNMT3B, RASSF1A, Otx2, Hoxb1, Jag1, Notch1, PARK7, WNT pathway genes) and whose activity is modulated by cooperative interactions with kreisler/Krml1, Krox20, PBX1, and RUNX1, by Polycomb-mediated repression (rae28), by SIRT5-mediated desuccinylation, and by STUB1-mediated ubiquitination; in hematopoiesis it promotes HSC proliferation and B lymphopoiesis, in development it patterns hindbrain rhombomeres and neural crest via cross-regulatory Hox networks, and in cancer it can act either as an oncogenic driver (via DNMT3B-mediated epigenetic silencing and WNT/CDCA3 activation) or as a tumor suppressor depending on cellular context.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HOXB3 is a homeodomain transcription factor that patterns the vertebrate hindbrain, governs hematopoietic stem and progenitor cell behavior, and acts as a context-dependent oncogenic driver by directly binding DNA and regulating downstream target genes [#0, #12, #13]. During hindbrain development, Hoxb3 expression is established by direct binding of the Maf/bZIP factor kreisler/Krml1 to conserved blocks in an r5 enhancer, with Krox20 synergizing to restrict expression to rhombomere 5, while a separate set of modular cis-elements directs neural, neural crest, and mesodermal domains [#1, #5, #6]; one of these (b3IIIa) is a vagal neural-crest enhancer relevant to enteric nervous system colonization [#10]. HOXB3 participates in cross-regulatory Hox networks, binding its own and paralog loci—repressing Hoxb1 through a discrete S3 site and being bound at element IIIa by both Hoxb3 and Hoxb4 [#7, #13]. Its expression boundaries are maintained post-establishment by the Polycomb-group protein rae28 [#9]. In hematopoiesis, HOXB3 promotes progenitor proliferation: overexpression drives myeloproliferation and impairs lymphoid development, Hoxb3/Hoxb4 double-knockout mice show a reduced and slow-cycling HSC pool, and Hoxb3-deficient mice develop age-dependent defects in IL-7-dependent B lymphopoiesis [#0, #8, #11]. In cancer, HOXB3 acts oncogenically by transcriptionally activating DNMT3B, which silences the RASSF1A tumor suppressor and miR-375 (a self-sustaining feedback loop), and by activating CDCA3, Notch1, and WNT pathway genes to drive proliferation, migration, and invasion [#12, #14, #16, #19]; in castration-resistant prostate cancer, WNT3A and APC loss release HOXB3 from the destruction complex to enter the nucleus and activate WNT targets [#18]. Transforming activity requires cooperation with PBX1 via its conserved tetrapeptide and homeodomain [#3]. HOXB3 activity is further tuned by post-translational control—STUB1-mediated ubiquitination and degradation (with HOXB3 activating PARK7 to regulate ferroptosis) and SIRT5-mediated desuccinylation [#20, #21]—and in glioblastoma it forms phase-separated condensates through its intrinsically disordered regions and RUNX1 interaction that drive super-enhancer-associated oncogenic transcription [#22].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established that HOXB3 directly controls hematopoietic proliferation and lineage output, defining its physiological role in blood formation.\",\n      \"evidence\": \"Retroviral overexpression in murine bone marrow with transplantation, flow cytometry and colony assays\",\n      \"pmids\": [\"9052833\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify direct transcriptional targets mediating the proliferative effect\", \"Gain-of-function may not reflect endogenous dosage\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identified the upstream activator of Hoxb3 in the hindbrain, showing kreisler/Krml1 directly binds the r5 enhancer to drive segmental expression.\",\n      \"evidence\": \"Transgenic reporter analysis with in vitro binding and enhancer mutagenesis\",\n      \"pmids\": [\"9144291\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish the full combinatorial logic restricting expression to r5\", \"Role of the required Ets site not assigned to a specific factor\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Confirmed kreisler as a conserved direct regulator of Hox group 3 paralogs and showed enhancer architecture determines distinct segmental boundaries.\",\n      \"evidence\": \"Transgenic, deletion, ectopic expression and kreisler-null analysis of Hoxa3/Hoxb3 enhancers\",\n      \"pmids\": [\"9895323\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address downstream targets of group 3 Hox in r5/r6\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated HOXB3 transforming activity depends on cofactor PBX1, defining a cooperative DNA-binding requirement for oncogenic function.\",\n      \"evidence\": \"Rat-1 transformation assay with tetrapeptide/homeodomain mutagenesis and PBX1 modulation\",\n      \"pmids\": [\"9692548\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the target genes through which HOXB3/PBX1 drive transformation\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Provided early evidence that HOXB3 binds defined TAATTA motifs to activate a developmental target gene (Otx2).\",\n      \"evidence\": \"Reporter assays and EMSA with recombinant HOXB3 homeodomain in embryonal carcinoma cells\",\n      \"pmids\": [\"9556594\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of Otx2 regulation not established\", \"Single lab, limited functional validation\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Distinguished establishment from maintenance of Hoxb3 boundaries, assigning Polycomb (rae28) to long-term domain restriction.\",\n      \"evidence\": \"rae28-knockout mouse with in situ hybridization and temporal expression analysis\",\n      \"pmids\": [\"11044623\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of rae28 recruitment to Hoxb3 not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Mapped the modular cis-regulatory architecture of the Hoxb3 locus, assigning separable elements to distinct tissue/stage expression domains.\",\n      \"evidence\": \"Transgenic lacZ reporter dissection of multiple DNA fragments alone and in combination\",\n      \"pmids\": [\"11254356\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trans-acting factors for several elements not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined the combinatorial logic restricting Hoxb3 to r5, showing Krox20 synergizes with kreisler at the r5 enhancer.\",\n      \"evidence\": \"Krox20-null genetics, ectopic expression, enhancer mutagenesis and EMSA\",\n      \"pmids\": [\"11823429\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how synergy is biochemically achieved at the enhancer\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Revealed Hox auto/cross-regulation, with Hoxb3 and Hoxb4 binding element IIIa to control neural-tube expression independent of kreisler sites.\",\n      \"evidence\": \"Transgenic analysis with EMSA and deletion/mutational dissection of element IIIa\",\n      \"pmids\": [\"12482716\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct autoregulatory link is indirect\", \"Identity of GCCAGGC-binding factor unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed Hoxb3 and Hoxb4 cooperate to sustain the HSC pool through proliferation/self-renewal rather than lineage commitment.\",\n      \"evidence\": \"Double-knockout mice with competitive repopulation, colony assays, cell-cycle kinetics\",\n      \"pmids\": [\"12748289\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct transcriptional targets in HSCs not identified\", \"Individual contribution of Hoxb3 vs Hoxb4 not separated\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified the b3IIIa element as a vagal neural-crest enhancer with relevance to enteric nervous system colonization.\",\n      \"evidence\": \"Transgenic lacZ reporter with cellular markers and Dom (Hirschsprung model) genetic cross\",\n      \"pmids\": [\"15768390\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of HOXB3 itself in Hirschsprung phenotype not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established a non-redundant role for endogenous Hoxb3 in IL-7-dependent B lymphopoiesis, refining its hematopoietic function.\",\n      \"evidence\": \"Hoxb3 knockout mice with flow cytometry, IL-7R analysis and IL-7 proliferation assays\",\n      \"pmids\": [\"17309827\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Hoxb3 directly regulates IL-7R transcription not shown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined an oncogenic epigenetic mechanism whereby HOXB3 activates DNMT3B to silence the RASSF1A tumor suppressor.\",\n      \"evidence\": \"Genome-wide shRNA screen, ChIP, bisulfite sequencing, rescue and xenograft experiments\",\n      \"pmids\": [\"19854132\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address context-dependent tumor-suppressive roles of HOXB3\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated direct Hoxb3-mediated repression of Hoxb1 via a discrete site, extending cross-regulatory Hox network function in the hindbrain.\",\n      \"evidence\": \"EMSA, in vivo ChIP, luciferase reporter and gain-of-function transgenic mouse\",\n      \"pmids\": [\"21320481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cofactors at the S3 site not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified CDCA3 as a direct HOXB3 target driving prostate cancer proliferation and migration.\",\n      \"evidence\": \"ChIP, shRNA, overexpression, xenograft and proliferation/migration assays\",\n      \"pmids\": [\"23219899\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Generality across tumor types not established at this stage\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed a tumor-suppressive facet of HOXB3, antagonizing FLT3-ITD oncogenic signaling in pro-B cells.\",\n      \"evidence\": \"Overexpression in mouse pro-B cells with phospho-signaling Western blots and apoptosis/colony assays\",\n      \"pmids\": [\"26482852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct molecular link between HOXB3 and FLT3 pathway demonstrated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected HOXB3 oncogenic outputs into a self-sustaining DNMT3B-miR-375 feedback loop in leukemia.\",\n      \"evidence\": \"Luciferase 3'-UTR reporter, bisulfite sequencing, shRNA, colony and xenograft assays\",\n      \"pmids\": [\"29439669\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Relative contribution of CDCA3 vs DNMT3B arms not quantified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed Hoxb3 directly regulates Jag1 in pharyngeal epithelium, linking it to neural crest migration via Notch ligand control.\",\n      \"evidence\": \"Binding assay at Jag1 site S2, gain-of-function transgenic mouse, in situ hybridization, migration analysis\",\n      \"pmids\": [\"33505317\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Endogenous loss-of-function effect on Jag1 not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed HOXB3 within WNT signaling as a destruction-complex-regulated transcription factor in castration-resistant prostate cancer.\",\n      \"evidence\": \"RNA-seq, WNT3A treatment, APC knockdown, nuclear fractionation and xenograft assays\",\n      \"pmids\": [\"36973255\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct WNT target genes activated by HOXB3 not individually validated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified Notch1 as a direct HOXB3 target driving Wnt/β-catenin-dependent trophoblast proliferation and invasion.\",\n      \"evidence\": \"Luciferase reporter, ChIP, siRNA rescue and invasion assays plus a rat preeclampsia model\",\n      \"pmids\": [\"37652291\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"In vivo human relevance limited\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established post-translational control of HOXB3 stability by STUB1 and a downstream PARK7 axis governing ferroptosis and drug resistance.\",\n      \"evidence\": \"Co-IP, dual luciferase, knockdown/overexpression rescue and xenograft in ovarian cancer\",\n      \"pmids\": [\"39501077\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination sites on HOXB3 not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified SIRT5-mediated desuccinylation as a suppressive post-translational modification of HOXB3 activity in trophoblasts.\",\n      \"evidence\": \"Co-IP, dual-luciferase, siRNA rescue and invasion/migration assays in HTR-8/SVneo cells\",\n      \"pmids\": [\"39145876\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific desuccinylated residues not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed that HOXB3 can drive oncogenic transcription through RUNX1-dependent phase-separated condensates at super-enhancers, offering a targetable mechanism.\",\n      \"evidence\": \"Single-cell CUT&Tag, condensate analysis, peptide disruption and patient-derived xenografts in glioblastoma\",\n      \"pmids\": [\"41028837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of condensate behavior beyond GBM subset unknown\", \"How condensate formation integrates with cofactors like PBX1 not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular basis determining whether HOXB3 acts as an oncogenic driver versus a tumor suppressor in a given cellular context remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model reconciling oncogenic (DNMT3B/WNT/CDCA3) and suppressive (FLT3-ITD) outputs\", \"Cofactor and PTM combinations that switch HOXB3 output not systematically defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [4, 13, 14, 19]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [12, 13, 14, 19, 20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 5, 6, 13, 17]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [12, 13, 14, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 18, 22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [18, 19, 15]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PBX1\", \"RUNX1\", \"STUB1\", \"SIRT5\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}