{"gene":"SMAD6","run_date":"2026-06-10T07:46:35","timeline":{"discoveries":[{"year":1997,"finding":"SMAD6 forms stable associations with TGF-β superfamily type I receptors and interferes with phosphorylation of Smad2 and subsequent heteromerization with Smad4; it also inhibits BMP type IB receptor-induced phosphorylation of Smad1, acting as a negative regulator of TGF-β superfamily signaling.","method":"Co-immunoprecipitation, phosphorylation assays, overexpression in mammalian cells","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP and functional phosphorylation assays, foundational paper replicated extensively by subsequent work","pmids":["9335505"],"is_preprint":false},{"year":1998,"finding":"SMAD6 specifically competes with Smad4 for binding to receptor-phosphorylated Smad1, yielding an apparently inactive Smad1-Smad6 complex, thereby acting as a 'Smad4 decoy' to selectively antagonize BMP/Smad1 signaling without inhibiting receptor-mediated phosphorylation of Smad1.","method":"Binding assays in Xenopus embryos and mammalian cells, co-immunoprecipitation, overexpression/loss-of-function","journal":"Genes & Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Xenopus embryo assay, mammalian cell Co-IP, functional reporter), replicated across labs","pmids":["9436979"],"is_preprint":false},{"year":1998,"finding":"SMAD6 mRNA is rapidly and directly induced by TGF-β1, activin, and BMP-7, as well as by EGF, establishing that expression of inhibitory Smads is regulated by multiple stimuli including TGF-β family members whose signaling they antagonize.","method":"Northern blot, RT-PCR, antisense RNA expression experiments in cultured cells","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab, multiple cell lines tested, consistent results","pmids":["9712726"],"is_preprint":false},{"year":1998,"finding":"Smad6 mRNA expression is dramatically and selectively induced by BMP-2 and BMP-7 (OP-1) in various cell types, forming a negative feedback loop to regulate BMP signaling activity.","method":"Northern blot, RT-PCR in multiple cell types treated with BMPs","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab, multiple cell types, consistent findings","pmids":["9514869"],"is_preprint":false},{"year":2000,"finding":"Smad6 interacts with the homeodomain transcription factor Hoxc-8 as a transcriptional corepressor in the nucleus; the Smad6-Hoxc-8 complex binds DNA and inhibits Smad1 interaction with Hoxc-8 and Smad1-induced transcription, establishing a nuclear function for Smad6 in BMP signaling inhibition.","method":"Yeast two-hybrid, co-immunoprecipitation, gel-shift (EMSA) assays, transcriptional reporter assays","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed by Co-IP and EMSA and functional reporter assay, multiple orthogonal methods in single lab","pmids":["10722652"],"is_preprint":false},{"year":2000,"finding":"Smad6 expression is regulated by BMP-activated Smad1/5 via direct binding of Smad1/5 and Smad4 to a GC-rich BMP-responsive element (PBE) in the proximal Smad6 promoter, identifying the BMP-Smad1/5-Smad6 axis as a negative feedback circuit.","method":"Promoter deletion analysis, luciferase reporter assays, DNA-binding assays (gel shift), cotransfection experiments","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — promoter mutagenesis, EMSA DNA-binding, and functional reporter assays in multiple cell types in single lab","pmids":["10692396"],"is_preprint":false},{"year":2000,"finding":"Smad6 negatively regulates the BMP2-induced TAK1-p38 kinase apoptotic pathway in addition to the Smad pathway; Smad6 directly binds TAK1 and blocks BMP2-induced TAK1 activation and p38 phosphorylation, conferring resistance to BMP2-induced apoptosis.","method":"Overexpression in MH60 hybridoma cells, kinase-negative dominant-negative assays, co-immunoprecipitation, kinase activation assays","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional follow-up (dominant-negative kinase, apoptosis assay), single lab","pmids":["10748100"],"is_preprint":false},{"year":2000,"finding":"Targeted deletion of Smad6 (Madh6) in mice causes cardiac valve hyperplasia, outflow tract septation defects, aortic ossification, and elevated blood pressure, establishing an essential in vivo role for Smad6 in cardiovascular development and homeostasis.","method":"Targeted gene disruption in mice (knockout), LacZ reporter insertion, histological and physiological analysis","journal":"Nature Genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout model with defined cardiovascular phenotypes, replicated and widely cited","pmids":["10655064"],"is_preprint":false},{"year":2003,"finding":"Smad6 represses BMP-induced Id1 transcription by recruiting the transcriptional corepressor CtBP via a PLDLS consensus motif in the Smad6 linker region; mutation of the PLDLS motif abolishes CtBP binding and Smad6 repressor activity.","method":"Luciferase reporter assays, co-immunoprecipitation, site-directed mutagenesis of PLDLS motif","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis of critical motif combined with functional transcriptional reporter and Co-IP, multiple orthogonal methods","pmids":["14645520"],"is_preprint":false},{"year":2005,"finding":"Smad6 directly interacts with Runx2 and mediates Smurf1-induced ubiquitin-proteasome-dependent degradation of Runx2, providing an indirect mechanism for Smurf1-induced Runx2 degradation beyond the PY motif interaction.","method":"Co-immunoprecipitation, ubiquitin-proteasome degradation assays, overexpression in mammalian cells","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP confirming Smad6-Runx2 interaction, functional degradation assays, single lab","pmids":["16299379"],"is_preprint":false},{"year":2005,"finding":"Smad6 interacts with the N-terminal domain of the glucocorticoid receptor (GR) through its MH2 domain, suppresses GR-mediated transcriptional activity by recruiting histone deacetylase 3 (HDAC3) to DNA-bound GR, and antagonizes histone H3/H4 acetylation; adenovirus-mediated Smad6 overexpression inhibits glucocorticoid action in rat liver in vivo.","method":"Co-immunoprecipitation, transcriptional reporter assays, adenoviral overexpression in vivo, domain mapping","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, functional reporter, in vivo adenoviral delivery, single lab with multiple methods","pmids":["16249187"],"is_preprint":false},{"year":2006,"finding":"Smad6 directly binds to Pellino-1 (an adaptor of IRAK1) via its MH2 domain, thereby disrupting the IRAK1-Pellino-1-TRAF6 signaling complex, preventing IκBα degradation and NF-κB nuclear translocation, and mediating TGF-β/BMP-induced anti-inflammatory effects on IL-1R/TLR signaling.","method":"Co-immunoprecipitation, siRNA knockdown, NF-κB reporter assays, domain mapping","journal":"Nature Immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP with domain mapping, siRNA functional knockdown, and NF-κB signaling readout, replicated in subsequent papers","pmids":["16951688"],"is_preprint":false},{"year":2006,"finding":"PRMT1 (protein arginine N-methyltransferase 1) methylates Smad6 at arginine 74 in its N-terminal domain; Smad6 (but not Smad4 or R-Smads) is a substrate of PRMT1-mediated dimethylation.","method":"In vitro methylation assay, mass spectrometry identification of methylation site, co-immunoprecipitation, mutagenesis (Smad6R74A)","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro methylation assay with MS site identification and mutagenesis, but functional consequence of methylation was not significant in assays tested, single lab","pmids":["17118358"],"is_preprint":false},{"year":2006,"finding":"Smad6 is phosphorylated by protein kinase X (PrKX) at a serine residue; PrKX and Smad6 co-localize to the nucleus during macrophage differentiation, and both proteins are required for PMA-induced HL-60 cell attachment, spreading, and differentiation.","method":"Yeast two-hybrid, co-immunoprecipitation, in vitro phosphorylation assay, mutagenesis of phosphorylation site, chromatin immunoprecipitation, siRNA knockdown","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay with mutagenesis confirmation and ChIP, single lab, multiple methods","pmids":["16491121"],"is_preprint":false},{"year":2007,"finding":"Smad6 preferentially inhibits BMP signaling through ALK-3/6 receptors over ALK-1/2 receptors; specific amino acid residues in the N-terminal lobe of the ALK-3 kinase domain (Arg-238, Phe-264, Thr-265, Ala-269) are responsible for Smad6 sensitivity, and Smad6 interaction with type I receptors is a critical step in its inhibitory function.","method":"Reporter assays, mutagenesis of ALK-3 residues, binding/co-immunoprecipitation studies","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — site-directed mutagenesis with functional signaling readout and binding studies, single lab","pmids":["17493940"],"is_preprint":false},{"year":2009,"finding":"Smad6 interacts with T-box transcription factor Tbx6 via its MH2 domain (interacting with residues 90-180 of Tbx6) and recruits Smurf1 to facilitate ubiquitin-proteasome-dependent degradation of Tbx6, reducing Tbx6-mediated Myf-5 gene activation.","method":"Co-immunoprecipitation, ubiquitin-proteasome degradation assays, domain mapping, siRNA knockdown, luciferase reporter","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, degradation assay, siRNA functional validation, single lab","pmids":["19561075"],"is_preprint":false},{"year":2011,"finding":"Smad6 inhibits the non-canonical TGF-β1 TRAF6-TAK1-p38 MAPK/JNK pathway by recruiting the A20 deubiquitinase to TRAF6, abolishing K63-linked polyubiquitination of TRAF6 and preventing downstream TAK1 and p38/JNK phosphorylation.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown in cell lines and animal models, phosphorylation assays","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, siRNA in cell culture and in vivo animal model, multiple orthogonal methods, single lab","pmids":["24096742"],"is_preprint":false},{"year":2011,"finding":"TGF-β1-induced Smad6 (but not Smad7) recruits Smurf1 and Smurf2 E3 ubiquitin ligases to mediate K48-linked polyubiquitination and proteasomal degradation of MyD88, thereby suppressing TLR4 and TLR2 (MyD88-dependent) pro-inflammatory signaling but not MyD88-independent TLR3 signaling.","method":"Co-immunoprecipitation, siRNA knockdown, ubiquitination assays, NF-κB nuclear translocation assay","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assays, siRNA knockdown with functional inflammatory readout, pathway specificity established, multiple orthogonal methods","pmids":["21897371"],"is_preprint":false},{"year":2011,"finding":"Loss of Smad6 in mice causes defects in endochondral bone formation, including delayed hypertrophic differentiation at midgestation and expanded hypertrophic zone at late gestation, attributed to increased BMP responsiveness in Smad6-deficient chondrocytes; Smad6 is essential to limit BMP signaling during cartilage development.","method":"Smad6 knockout mice, histological analysis of growth plates, BMP responsiveness assays in chondrocytes","journal":"Journal of Bone and Mineral Research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockout with defined skeletal phenotypes and mechanistic cell-based follow-up","pmids":["21681813"],"is_preprint":false},{"year":2011,"finding":"Smad6 promotes neuronal differentiation in the intermediate zone of the dorsal spinal cord by inhibiting both the BMP pathway and the Wnt/β-catenin pathway; the inhibition of Wnt/β-catenin by Smad6 is independent of BMP inhibition and is mediated through the N-terminal domain and linker region of Smad6, which enhances interaction of CtBP with the β-catenin/TCF complex.","method":"In ovo knockdown (chick), reporter assays, domain mapping, co-immunoprecipitation","journal":"PNAS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockdown, Co-IP, reporter assays with domain mapping, single lab","pmids":["21730158"],"is_preprint":false},{"year":2013,"finding":"UBE2O (E2-230K) functions as an E2-E3 hybrid ubiquitin-conjugating enzyme that monoubiquitinates SMAD6 at lysine 174 (requiring Cys-885 of UBE2O); monoubiquitination of SMAD6 at this site impairs SMAD6 binding to the BMP type I receptor, thereby potentiating BMP7 signaling; UBE2O and SMAD6 cooperate in regulation of BMP7-induced adipogenesis.","method":"Proteomic interaction screen, in vitro ubiquitination assay, site-directed mutagenesis (K174, C885), binding assays, adipogenesis functional assay","journal":"The EMBO Journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitination assay with mutagenesis of both enzyme active site and substrate acceptor site, functional cellular consequence demonstrated, single lab with multiple methods","pmids":["23455153"],"is_preprint":false},{"year":2015,"finding":"Arkadia E3 ubiquitin ligase induces ubiquitylation and proteasome-dependent degradation of Smad6 (as well as Smad7 and c-Ski/SnoN), thereby positively regulating BMP signaling; Arkadia lacking E3 ligase activity (C937A mutant) fails to degrade Smad6.","method":"Ubiquitination assays, proteasome inhibitor treatments, Arkadia knockout MEFs, mutagenesis of Arkadia active site, transcriptional reporter assays","journal":"Journal of Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — E3 ligase active-site mutagenesis with functional degradation assay and KO validation, single lab","pmids":["25762727"],"is_preprint":false},{"year":2018,"finding":"Nuclear Smad6 interacts directly with PIAS3 via its MH2 domain (and PIAS3 Ring domain), recruits Smurf1 via the PY motif to promote PIAS3 ubiquitination and degradation, thereby reducing PIAS3-mediated STAT3 inhibition and promoting glioma cell growth.","method":"Co-immunoprecipitation, domain mapping (MH2, PY motif mutations), ubiquitination assays, functional glioma cell assays","journal":"Nature Communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, ubiquitination assay, functional cellular readout, single lab","pmids":["29950561"],"is_preprint":false},{"year":2018,"finding":"PRMT1-induced arginine methylation of Smad6 enables Smad6 to recruit MyD88 and promote its degradation, thereby inhibiting TLR-NF-κB signaling and periodontal inflammation; disruption of Smad6 methylation exacerbates inflammation and bone loss in experimental periodontitis.","method":"PRMT1-Smad6 signaling assays, methylation-site mutagenesis, MyD88 degradation assays, siRNA knockdown, experimental periodontitis animal model","journal":"Journal of Dental Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of methylation site with functional inflammatory assay and in vivo model, single lab","pmids":["29420098"],"is_preprint":false},{"year":2021,"finding":"SMAD6 functions downstream of Notch1 signaling and upstream of the vascular protocadherin PCDH12 to transduce endothelial cell flow-mediated responses; SMAD6 depletion causes defective barrier function, upregulation of proliferation-associated genes, downregulation of junction-associated genes, and impaired flow-mediated endothelial cell alignment.","method":"Notch1 pathway manipulation combined with SMAD6 knockdown/rescue, flow alignment assays, gene expression analysis, barrier function assays","journal":"Angiogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis experiments (Notch-SMAD6-PCDH12), loss-of-function with defined cellular phenotypes, single lab","pmids":["33779885"],"is_preprint":false},{"year":2005,"finding":"OAZ (transcriptional activator and Smad1/4 cofactor) forms a complex with Smad1/4 upon BMP4 stimulation and activates the Smad6 gene; removal of endogenous OAZ prevents BMP4-induced Smad6 induction and extends Smad1 phosphorylation, while forced OAZ expression in cells that lack it accelerates Smad6 induction and attenuates BMP responses.","method":"OAZ knockout/knockdown and overexpression, chromatin immunoprecipitation, reporter assays, phospho-Smad1 assays","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and gain-of-function with ChIP and functional signaling readouts, single lab","pmids":["16373339"],"is_preprint":false},{"year":2006,"finding":"Smad6 interacts with Dlx3 homeobox transcription factor (via the homeodomain-containing region residues 80-163 of Dlx3) in the nucleus of trophoblasts; Smad6 inhibits Dlx3 binding to target gene promoters (Esx1) and represses Dlx3-dependent transcription, as confirmed by siRNA knockdown of endogenous Smad6.","method":"Co-immunoprecipitation, immunocytochemistry, in vitro protein interaction mapping, EMSA, luciferase reporter, siRNA knockdown","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, EMSA, domain mapping, siRNA functional validation, single lab with multiple methods","pmids":["16687405"],"is_preprint":false},{"year":2011,"finding":"Runx1 (together with Fli1, Gata2, and Scl) directly regulates Smad6 expression via a novel upstream enhancer in the aorta-gonad-mesonephros region, establishing a functional rheostat where Runx1 controls its own activity by driving expression of Smad6, which targets Runx1 to the proteasome.","method":"ChIP, luciferase reporter (enhancer assay), Runx1 null embryo analysis, proteasomal inhibitor experiments","journal":"Molecular and Cellular Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP with functional enhancer reporter and in vivo Runx1 null validation, single lab","pmids":["21576367"],"is_preprint":false},{"year":2017,"finding":"AMPK activation upregulates Smad6 and Smurf1 and enhances their interaction, leading to proteasome-dependent degradation of ALK2; knockdown of Smad6 or Smurf1 prevents metformin-induced reduction of ALK2 levels, placing the Smad6-Smurf1 complex as a mediator of AMPK-induced ALK2 degradation.","method":"AMPK activators/inhibitors, siRNA knockdown of Smad6/Smurf1, co-immunoprecipitation, proteasome inhibitor assays, iPS cell osteogenic differentiation","journal":"Biochimica et Biophysica Acta: Molecular Cell Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, siRNA rescue experiment, functional differentiation assay, single lab","pmids":["28847510"],"is_preprint":false},{"year":2010,"finding":"Smad6 and Smad7 bind simultaneously to discrete non-overlapping regions of Pellino-1 via distinct portions of their MH2 domains, and combined knockdown of both Smad6 and Smad7 further reduces TGF-β1 anti-inflammatory activity compared to single knockdown.","method":"Co-immunoprecipitation, domain mapping, double siRNA knockdown, NF-κB reporter assays","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, double knockdown functional assay, single lab","pmids":["20171181"],"is_preprint":false},{"year":2011,"finding":"JNK1 (but not JNK2) activation decreases binding of inhibitory Smad6 to BMPR-I and reciprocally increases Smad1 binding to BMPR-I, thereby increasing cellular responsiveness to BMP-2 and promoting osteoblast differentiation.","method":"JNK gain-of-function and loss-of-function, receptor binding assays, phospho-Smad1 assays, osteoblast differentiation (mineralized nodule formation)","journal":"Journal of Bone and Mineral Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with binding and functional differentiation assays, single lab","pmids":["21542012"],"is_preprint":false}],"current_model":"SMAD6 is an inhibitory SMAD that negatively regulates BMP/TGF-β superfamily signaling through multiple mechanisms: it binds type I BMP receptors (preferentially ALK-3/6) to block R-Smad phosphorylation, acts as a Smad4 decoy by binding phosphorylated Smad1 to prevent Smad1-Smad4 complex formation, and functions in the nucleus as a transcriptional corepressor by interacting with Hoxc-8 and recruiting CtBP via its PLDLS motif; beyond canonical Smad signaling, SMAD6 suppresses non-canonical TGF-β/BMP pathways by binding TAK1 and recruiting the deubiquitinase A20 to TRAF6, inhibits TLR/IL-1R inflammation by binding Pellino-1 and mediating Smurf1/2-dependent MyD88 degradation (potentiated by PRMT1-mediated arginine methylation of Smad6), interacts with transcription factors (Runx2, Tbx6, Dlx3, GR) to recruit Smurf1 for their ubiquitin-proteasome degradation, and is itself regulated by monoubiquitination at K174 by UBE2O (reducing receptor binding) and by Arkadia-mediated degradation; in vivo, Smad6 is essential for cardiovascular development, endochondral ossification, vascular homeostasis downstream of Notch1, and hematopoietic stem cell regulation."},"narrative":{"mechanistic_narrative":"SMAD6 is an inhibitory SMAD that serves as a negative-feedback brake on BMP/TGF-β superfamily signaling, acting at the receptor, in the cytoplasm, and within the nucleus [PMID:9335505, PMID:9436979]. At the membrane it forms stable associations with type I receptors to block R-Smad phosphorylation, with selectivity for ALK-3/6 over ALK-1/2 dictated by residues in the receptor kinase N-lobe [PMID:9335505, PMID:17493940], and it additionally acts as a 'Smad4 decoy' by binding receptor-phosphorylated Smad1 to prevent productive Smad1–Smad4 complex formation [PMID:9436979]. In the nucleus SMAD6 functions as a transcriptional corepressor: it complexes with the homeodomain factor Hoxc-8 to block Smad1-driven transcription [PMID:10722652] and recruits the corepressor CtBP through a PLDLS motif in its linker to repress BMP-induced Id1 [PMID:14645520]. SMAD6 also extends beyond canonical Smad signaling to suppress non-canonical and inflammatory cascades, binding TAK1 to block BMP2-induced p38 activation [PMID:10748100], recruiting the deubiquitinase A20 to TRAF6 to abolish K63-linked ubiquitination [PMID:24096742], and binding Pellino-1 to disrupt the IRAK1–Pellino-1–TRAF6 complex and dampen NF-κB activation downstream of IL-1R/TLR [PMID:16951688]. A recurring mechanism is SMAD6-dependent recruitment of the E3 ligases Smurf1/2 to direct ubiquitin-proteasome degradation of bound partners, including Runx2, Tbx6, MyD88, and PIAS3 [PMID:16299379, PMID:19561075, PMID:21897371, PMID:29950561]. SMAD6 activity is itself tuned by post-translational modification — PRMT1-mediated arginine methylation potentiates its anti-inflammatory MyD88-degrading function [PMID:29420098], UBE2O-mediated monoubiquitination at K174 impairs receptor binding [PMID:23455153], and Arkadia-mediated ubiquitination targets SMAD6 for degradation to relieve BMP inhibition [PMID:25762727]. In vivo, Smad6 is essential for cardiovascular development and homeostasis [PMID:10655064], for limiting BMP signaling during endochondral ossification [PMID:21681813], and for endothelial flow responses downstream of Notch1 [PMID:33779885].","teleology":[{"year":1997,"claim":"Established SMAD6 as a negative regulator of TGF-β superfamily signaling acting at the receptor level, answering how the pathway is intrinsically restrained.","evidence":"Co-IP and phosphorylation assays in mammalian cells showing receptor association and blocked R-Smad phosphorylation","pmids":["9335505"],"confidence":"High","gaps":["Receptor selectivity (ALK subtypes) not yet defined","Mechanism of decoy versus receptor block not distinguished"]},{"year":1998,"claim":"Defined a distinct cytoplasmic mechanism—competition with Smad4 for phospho-Smad1—showing SMAD6 inhibits downstream of receptor phosphorylation, not only at the receptor.","evidence":"Binding/Co-IP assays in Xenopus embryos and mammalian cells with functional reporters","pmids":["9436979"],"confidence":"High","gaps":["Structural basis of the Smad1–Smad6 complex unresolved","Relative contribution of decoy versus receptor mechanisms in vivo unclear"]},{"year":1998,"claim":"Showed SMAD6 expression is induced by the very ligands it antagonizes, framing it as a negative-feedback component of BMP/TGF-β signaling.","evidence":"Northern blot and RT-PCR after TGF-β, activin, BMP-2/7 and EGF stimulation in multiple cell lines","pmids":["9712726","9514869"],"confidence":"Medium","gaps":["Transcription factors mediating induction not yet identified","Single-lab transcriptional readouts"]},{"year":2000,"claim":"Identified the cis and trans elements driving feedback induction, mapping a BMP-Smad1/5-Smad6 circuit and a nuclear corepressor role.","evidence":"Promoter mutagenesis/EMSA defining the PBE; yeast two-hybrid, Co-IP and EMSA linking SMAD6 to Hoxc-8","pmids":["10692396","10722652"],"confidence":"High","gaps":["Genome-wide SMAD6 target gene set not defined","How nuclear and receptor functions are partitioned unclear"]},{"year":2000,"claim":"Extended SMAD6 inhibition to a non-canonical branch (TAK1-p38) and established an essential in vivo cardiovascular role.","evidence":"TAK1 Co-IP with dominant-negative kinase and apoptosis assays; Smad6 knockout mice with cardiovascular phenotypes","pmids":["10748100","10655064"],"confidence":"High","gaps":["Molecular basis of SMAD6-TAK1 inhibition not defined","Cell-type-specific contributions to cardiovascular phenotype not dissected"]},{"year":2003,"claim":"Pinpointed the corepressor recruitment mechanism for nuclear repression via the PLDLS-CtBP interaction.","evidence":"Site-directed PLDLS mutagenesis with Co-IP and Id1 reporter assays","pmids":["14645520"],"confidence":"High","gaps":["Range of promoters subject to CtBP-dependent repression unknown","Whether CtBP recruitment cooperates with R-Smad binding unclear"]},{"year":2005,"claim":"Revealed SMAD6 as an adaptor that targets transcription factors (Runx2) and nuclear receptors (GR) for Smurf1-mediated degradation or corepressor-mediated silencing, broadening its effector repertoire.","evidence":"Co-IP, degradation/ubiquitination assays for Runx2; domain mapping, HDAC3 recruitment and in vivo adenoviral assays for GR; OAZ-driven Smad6 induction by ChIP","pmids":["16299379","16249187","16373339"],"confidence":"Medium","gaps":["Specificity determinants for substrate selection unclear","Single-lab Co-IP and degradation evidence"]},{"year":2006,"claim":"Established SMAD6 as an anti-inflammatory node linking TGF-β/BMP signaling to IL-1R/TLR-NF-κB suppression and identified covalent modification of SMAD6 itself.","evidence":"Pellino-1 Co-IP/domain mapping with NF-κB reporters; PrKX in vitro kinase assay; PRMT1 in vitro methylation with MS; Dlx3 Co-IP/EMSA","pmids":["16951688","16491121","17118358","16687405"],"confidence":"Medium","gaps":["Functional consequence of R74 methylation not established at this stage","Interplay of modifications not resolved"]},{"year":2007,"claim":"Defined receptor selectivity at residue resolution, explaining why SMAD6 preferentially restrains ALK-3/6 signaling.","evidence":"Mutagenesis of ALK-3 kinase-domain residues with reporter and binding assays","pmids":["17493940"],"confidence":"Medium","gaps":["Structural complex of SMAD6 with receptor not solved","Single-lab mapping"]},{"year":2009,"claim":"Generalized the Smurf1-recruitment mechanism to additional developmental transcription factors (Tbx6), reinforcing SMAD6 as a degradation adaptor.","evidence":"Co-IP, domain mapping, ubiquitin-proteasome degradation and reporter assays with siRNA validation","pmids":["19561075"],"confidence":"Medium","gaps":["In vivo relevance to Myf-5 regulation untested","Single-lab evidence"]},{"year":2011,"claim":"Resolved distinct biochemical mechanisms for inflammatory suppression—A20 recruitment to TRAF6 and Smurf1/2-mediated MyD88 degradation—and confirmed essential in vivo roles in skeletal and neural development.","evidence":"Ubiquitination/Co-IP assays for A20-TRAF6 and MyD88; Smad6 knockout growth-plate histology; in ovo chick knockdown for spinal cord; Runx1-driven enhancer ChIP; JNK1 receptor-binding assays","pmids":["24096742","21897371","21681813","21730158","21576367","21542012"],"confidence":"High","gaps":["Coordination between SMAD6's many parallel mechanisms in a single cell unclear","Wnt/β-catenin inhibition mechanism only partly mapped"]},{"year":2013,"claim":"Showed SMAD6 activity is gated by monoubiquitination, providing a switch that relieves receptor inhibition.","evidence":"Proteomic screen, in vitro ubiquitination with K174/C885 mutagenesis, and BMP7-adipogenesis assays","pmids":["23455153"],"confidence":"High","gaps":["Deubiquitinase reversing K174 modification unknown","Physiological triggers of UBE2O activity undefined"]},{"year":2015,"claim":"Identified Arkadia-mediated degradation as a route to inactivate SMAD6 and positively tune BMP signaling.","evidence":"Ubiquitination/degradation assays with Arkadia C937A mutant and knockout MEFs","pmids":["25762727"],"confidence":"Medium","gaps":["Signals controlling Arkadia targeting of SMAD6 unknown","Single-lab evidence"]},{"year":2018,"claim":"Extended SMAD6 functions into oncogenic STAT3 signaling and refined the methylation mechanism as functionally consequential for inflammation.","evidence":"PIAS3 Co-IP/domain mapping and ubiquitination in glioma cells; PRMT1 methylation-site mutagenesis with periodontitis model","pmids":["29950561","29420098"],"confidence":"Medium","gaps":["Context determining pro- versus anti-tumor roles unclear","Single-lab functional assays"]},{"year":2021,"claim":"Placed SMAD6 within an endothelial mechanotransduction axis, linking it to flow-mediated barrier and alignment responses downstream of Notch1.","evidence":"Notch1-SMAD6-PCDH12 epistasis with flow alignment, barrier and gene-expression assays","pmids":["33779885"],"confidence":"Medium","gaps":["Direct biochemical link between SMAD6 and PCDH12 not defined","Single-lab epistasis"]},{"year":null,"claim":"How SMAD6's many parallel activities—receptor inhibition, decoy function, transcriptional corepression, degradation-adaptor roles, and inflammatory suppression—are integrated and prioritized within a single cell, and the structural basis of its key interactions, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of SMAD6-receptor or SMAD6-Smad1 complexes in the corpus","Hierarchy among cytoplasmic versus nuclear functions undefined","Disease-causing human mutations not addressed in the timeline"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,8,10,26]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[9,15,17,22]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,11,16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[9,15,17,22]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[4,26]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,8,13,22,26]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,14,30]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,11,16]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,14]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[11,16,17]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,8,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[9,15,17,20,21]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,18,24]}],"complexes":[],"partners":["SMAD1","SMURF1","TAK1","TRAF6","PELLINO-1","MYD88","RUNX2","CTBP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43541","full_name":"SMAD family member 6","aliases":["Mothers against decapentaplegic homolog 6","MAD homolog 6","Mothers against DPP homolog 6"],"length_aa":496,"mass_kda":53.5,"function":"Transforming growth factor-beta superfamily receptors signaling occurs through the Smad family of intracellular mediators. 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standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"SMAD6 forms stable associations with TGF-β superfamily type I receptors and interferes with phosphorylation of Smad2 and subsequent heteromerization with Smad4; it also inhibits BMP type IB receptor-induced phosphorylation of Smad1, acting as a negative regulator of TGF-β superfamily signaling.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation assays, overexpression in mammalian cells\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP and functional phosphorylation assays, foundational paper replicated extensively by subsequent work\",\n      \"pmids\": [\"9335505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"SMAD6 specifically competes with Smad4 for binding to receptor-phosphorylated Smad1, yielding an apparently inactive Smad1-Smad6 complex, thereby acting as a 'Smad4 decoy' to selectively antagonize BMP/Smad1 signaling without inhibiting receptor-mediated phosphorylation of Smad1.\",\n      \"method\": \"Binding assays in Xenopus embryos and mammalian cells, co-immunoprecipitation, overexpression/loss-of-function\",\n      \"journal\": \"Genes & Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Xenopus embryo assay, mammalian cell Co-IP, functional reporter), replicated across labs\",\n      \"pmids\": [\"9436979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"SMAD6 mRNA is rapidly and directly induced by TGF-β1, activin, and BMP-7, as well as by EGF, establishing that expression of inhibitory Smads is regulated by multiple stimuli including TGF-β family members whose signaling they antagonize.\",\n      \"method\": \"Northern blot, RT-PCR, antisense RNA expression experiments in cultured cells\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab, multiple cell lines tested, consistent results\",\n      \"pmids\": [\"9712726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Smad6 mRNA expression is dramatically and selectively induced by BMP-2 and BMP-7 (OP-1) in various cell types, forming a negative feedback loop to regulate BMP signaling activity.\",\n      \"method\": \"Northern blot, RT-PCR in multiple cell types treated with BMPs\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab, multiple cell types, consistent findings\",\n      \"pmids\": [\"9514869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Smad6 interacts with the homeodomain transcription factor Hoxc-8 as a transcriptional corepressor in the nucleus; the Smad6-Hoxc-8 complex binds DNA and inhibits Smad1 interaction with Hoxc-8 and Smad1-induced transcription, establishing a nuclear function for Smad6 in BMP signaling inhibition.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, gel-shift (EMSA) assays, transcriptional reporter assays\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed by Co-IP and EMSA and functional reporter assay, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"10722652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Smad6 expression is regulated by BMP-activated Smad1/5 via direct binding of Smad1/5 and Smad4 to a GC-rich BMP-responsive element (PBE) in the proximal Smad6 promoter, identifying the BMP-Smad1/5-Smad6 axis as a negative feedback circuit.\",\n      \"method\": \"Promoter deletion analysis, luciferase reporter assays, DNA-binding assays (gel shift), cotransfection experiments\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — promoter mutagenesis, EMSA DNA-binding, and functional reporter assays in multiple cell types in single lab\",\n      \"pmids\": [\"10692396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Smad6 negatively regulates the BMP2-induced TAK1-p38 kinase apoptotic pathway in addition to the Smad pathway; Smad6 directly binds TAK1 and blocks BMP2-induced TAK1 activation and p38 phosphorylation, conferring resistance to BMP2-induced apoptosis.\",\n      \"method\": \"Overexpression in MH60 hybridoma cells, kinase-negative dominant-negative assays, co-immunoprecipitation, kinase activation assays\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional follow-up (dominant-negative kinase, apoptosis assay), single lab\",\n      \"pmids\": [\"10748100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Targeted deletion of Smad6 (Madh6) in mice causes cardiac valve hyperplasia, outflow tract septation defects, aortic ossification, and elevated blood pressure, establishing an essential in vivo role for Smad6 in cardiovascular development and homeostasis.\",\n      \"method\": \"Targeted gene disruption in mice (knockout), LacZ reporter insertion, histological and physiological analysis\",\n      \"journal\": \"Nature Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout model with defined cardiovascular phenotypes, replicated and widely cited\",\n      \"pmids\": [\"10655064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Smad6 represses BMP-induced Id1 transcription by recruiting the transcriptional corepressor CtBP via a PLDLS consensus motif in the Smad6 linker region; mutation of the PLDLS motif abolishes CtBP binding and Smad6 repressor activity.\",\n      \"method\": \"Luciferase reporter assays, co-immunoprecipitation, site-directed mutagenesis of PLDLS motif\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis of critical motif combined with functional transcriptional reporter and Co-IP, multiple orthogonal methods\",\n      \"pmids\": [\"14645520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Smad6 directly interacts with Runx2 and mediates Smurf1-induced ubiquitin-proteasome-dependent degradation of Runx2, providing an indirect mechanism for Smurf1-induced Runx2 degradation beyond the PY motif interaction.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitin-proteasome degradation assays, overexpression in mammalian cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP confirming Smad6-Runx2 interaction, functional degradation assays, single lab\",\n      \"pmids\": [\"16299379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Smad6 interacts with the N-terminal domain of the glucocorticoid receptor (GR) through its MH2 domain, suppresses GR-mediated transcriptional activity by recruiting histone deacetylase 3 (HDAC3) to DNA-bound GR, and antagonizes histone H3/H4 acetylation; adenovirus-mediated Smad6 overexpression inhibits glucocorticoid action in rat liver in vivo.\",\n      \"method\": \"Co-immunoprecipitation, transcriptional reporter assays, adenoviral overexpression in vivo, domain mapping\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, functional reporter, in vivo adenoviral delivery, single lab with multiple methods\",\n      \"pmids\": [\"16249187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Smad6 directly binds to Pellino-1 (an adaptor of IRAK1) via its MH2 domain, thereby disrupting the IRAK1-Pellino-1-TRAF6 signaling complex, preventing IκBα degradation and NF-κB nuclear translocation, and mediating TGF-β/BMP-induced anti-inflammatory effects on IL-1R/TLR signaling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, NF-κB reporter assays, domain mapping\",\n      \"journal\": \"Nature Immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP with domain mapping, siRNA functional knockdown, and NF-κB signaling readout, replicated in subsequent papers\",\n      \"pmids\": [\"16951688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PRMT1 (protein arginine N-methyltransferase 1) methylates Smad6 at arginine 74 in its N-terminal domain; Smad6 (but not Smad4 or R-Smads) is a substrate of PRMT1-mediated dimethylation.\",\n      \"method\": \"In vitro methylation assay, mass spectrometry identification of methylation site, co-immunoprecipitation, mutagenesis (Smad6R74A)\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro methylation assay with MS site identification and mutagenesis, but functional consequence of methylation was not significant in assays tested, single lab\",\n      \"pmids\": [\"17118358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Smad6 is phosphorylated by protein kinase X (PrKX) at a serine residue; PrKX and Smad6 co-localize to the nucleus during macrophage differentiation, and both proteins are required for PMA-induced HL-60 cell attachment, spreading, and differentiation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, in vitro phosphorylation assay, mutagenesis of phosphorylation site, chromatin immunoprecipitation, siRNA knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay with mutagenesis confirmation and ChIP, single lab, multiple methods\",\n      \"pmids\": [\"16491121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Smad6 preferentially inhibits BMP signaling through ALK-3/6 receptors over ALK-1/2 receptors; specific amino acid residues in the N-terminal lobe of the ALK-3 kinase domain (Arg-238, Phe-264, Thr-265, Ala-269) are responsible for Smad6 sensitivity, and Smad6 interaction with type I receptors is a critical step in its inhibitory function.\",\n      \"method\": \"Reporter assays, mutagenesis of ALK-3 residues, binding/co-immunoprecipitation studies\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — site-directed mutagenesis with functional signaling readout and binding studies, single lab\",\n      \"pmids\": [\"17493940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Smad6 interacts with T-box transcription factor Tbx6 via its MH2 domain (interacting with residues 90-180 of Tbx6) and recruits Smurf1 to facilitate ubiquitin-proteasome-dependent degradation of Tbx6, reducing Tbx6-mediated Myf-5 gene activation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitin-proteasome degradation assays, domain mapping, siRNA knockdown, luciferase reporter\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, degradation assay, siRNA functional validation, single lab\",\n      \"pmids\": [\"19561075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Smad6 inhibits the non-canonical TGF-β1 TRAF6-TAK1-p38 MAPK/JNK pathway by recruiting the A20 deubiquitinase to TRAF6, abolishing K63-linked polyubiquitination of TRAF6 and preventing downstream TAK1 and p38/JNK phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown in cell lines and animal models, phosphorylation assays\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, siRNA in cell culture and in vivo animal model, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"24096742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TGF-β1-induced Smad6 (but not Smad7) recruits Smurf1 and Smurf2 E3 ubiquitin ligases to mediate K48-linked polyubiquitination and proteasomal degradation of MyD88, thereby suppressing TLR4 and TLR2 (MyD88-dependent) pro-inflammatory signaling but not MyD88-independent TLR3 signaling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, ubiquitination assays, NF-κB nuclear translocation assay\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assays, siRNA knockdown with functional inflammatory readout, pathway specificity established, multiple orthogonal methods\",\n      \"pmids\": [\"21897371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Loss of Smad6 in mice causes defects in endochondral bone formation, including delayed hypertrophic differentiation at midgestation and expanded hypertrophic zone at late gestation, attributed to increased BMP responsiveness in Smad6-deficient chondrocytes; Smad6 is essential to limit BMP signaling during cartilage development.\",\n      \"method\": \"Smad6 knockout mice, histological analysis of growth plates, BMP responsiveness assays in chondrocytes\",\n      \"journal\": \"Journal of Bone and Mineral Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockout with defined skeletal phenotypes and mechanistic cell-based follow-up\",\n      \"pmids\": [\"21681813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Smad6 promotes neuronal differentiation in the intermediate zone of the dorsal spinal cord by inhibiting both the BMP pathway and the Wnt/β-catenin pathway; the inhibition of Wnt/β-catenin by Smad6 is independent of BMP inhibition and is mediated through the N-terminal domain and linker region of Smad6, which enhances interaction of CtBP with the β-catenin/TCF complex.\",\n      \"method\": \"In ovo knockdown (chick), reporter assays, domain mapping, co-immunoprecipitation\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockdown, Co-IP, reporter assays with domain mapping, single lab\",\n      \"pmids\": [\"21730158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"UBE2O (E2-230K) functions as an E2-E3 hybrid ubiquitin-conjugating enzyme that monoubiquitinates SMAD6 at lysine 174 (requiring Cys-885 of UBE2O); monoubiquitination of SMAD6 at this site impairs SMAD6 binding to the BMP type I receptor, thereby potentiating BMP7 signaling; UBE2O and SMAD6 cooperate in regulation of BMP7-induced adipogenesis.\",\n      \"method\": \"Proteomic interaction screen, in vitro ubiquitination assay, site-directed mutagenesis (K174, C885), binding assays, adipogenesis functional assay\",\n      \"journal\": \"The EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitination assay with mutagenesis of both enzyme active site and substrate acceptor site, functional cellular consequence demonstrated, single lab with multiple methods\",\n      \"pmids\": [\"23455153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Arkadia E3 ubiquitin ligase induces ubiquitylation and proteasome-dependent degradation of Smad6 (as well as Smad7 and c-Ski/SnoN), thereby positively regulating BMP signaling; Arkadia lacking E3 ligase activity (C937A mutant) fails to degrade Smad6.\",\n      \"method\": \"Ubiquitination assays, proteasome inhibitor treatments, Arkadia knockout MEFs, mutagenesis of Arkadia active site, transcriptional reporter assays\",\n      \"journal\": \"Journal of Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — E3 ligase active-site mutagenesis with functional degradation assay and KO validation, single lab\",\n      \"pmids\": [\"25762727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Nuclear Smad6 interacts directly with PIAS3 via its MH2 domain (and PIAS3 Ring domain), recruits Smurf1 via the PY motif to promote PIAS3 ubiquitination and degradation, thereby reducing PIAS3-mediated STAT3 inhibition and promoting glioma cell growth.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping (MH2, PY motif mutations), ubiquitination assays, functional glioma cell assays\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, ubiquitination assay, functional cellular readout, single lab\",\n      \"pmids\": [\"29950561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PRMT1-induced arginine methylation of Smad6 enables Smad6 to recruit MyD88 and promote its degradation, thereby inhibiting TLR-NF-κB signaling and periodontal inflammation; disruption of Smad6 methylation exacerbates inflammation and bone loss in experimental periodontitis.\",\n      \"method\": \"PRMT1-Smad6 signaling assays, methylation-site mutagenesis, MyD88 degradation assays, siRNA knockdown, experimental periodontitis animal model\",\n      \"journal\": \"Journal of Dental Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of methylation site with functional inflammatory assay and in vivo model, single lab\",\n      \"pmids\": [\"29420098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SMAD6 functions downstream of Notch1 signaling and upstream of the vascular protocadherin PCDH12 to transduce endothelial cell flow-mediated responses; SMAD6 depletion causes defective barrier function, upregulation of proliferation-associated genes, downregulation of junction-associated genes, and impaired flow-mediated endothelial cell alignment.\",\n      \"method\": \"Notch1 pathway manipulation combined with SMAD6 knockdown/rescue, flow alignment assays, gene expression analysis, barrier function assays\",\n      \"journal\": \"Angiogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis experiments (Notch-SMAD6-PCDH12), loss-of-function with defined cellular phenotypes, single lab\",\n      \"pmids\": [\"33779885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"OAZ (transcriptional activator and Smad1/4 cofactor) forms a complex with Smad1/4 upon BMP4 stimulation and activates the Smad6 gene; removal of endogenous OAZ prevents BMP4-induced Smad6 induction and extends Smad1 phosphorylation, while forced OAZ expression in cells that lack it accelerates Smad6 induction and attenuates BMP responses.\",\n      \"method\": \"OAZ knockout/knockdown and overexpression, chromatin immunoprecipitation, reporter assays, phospho-Smad1 assays\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and gain-of-function with ChIP and functional signaling readouts, single lab\",\n      \"pmids\": [\"16373339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Smad6 interacts with Dlx3 homeobox transcription factor (via the homeodomain-containing region residues 80-163 of Dlx3) in the nucleus of trophoblasts; Smad6 inhibits Dlx3 binding to target gene promoters (Esx1) and represses Dlx3-dependent transcription, as confirmed by siRNA knockdown of endogenous Smad6.\",\n      \"method\": \"Co-immunoprecipitation, immunocytochemistry, in vitro protein interaction mapping, EMSA, luciferase reporter, siRNA knockdown\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, EMSA, domain mapping, siRNA functional validation, single lab with multiple methods\",\n      \"pmids\": [\"16687405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Runx1 (together with Fli1, Gata2, and Scl) directly regulates Smad6 expression via a novel upstream enhancer in the aorta-gonad-mesonephros region, establishing a functional rheostat where Runx1 controls its own activity by driving expression of Smad6, which targets Runx1 to the proteasome.\",\n      \"method\": \"ChIP, luciferase reporter (enhancer assay), Runx1 null embryo analysis, proteasomal inhibitor experiments\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP with functional enhancer reporter and in vivo Runx1 null validation, single lab\",\n      \"pmids\": [\"21576367\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AMPK activation upregulates Smad6 and Smurf1 and enhances their interaction, leading to proteasome-dependent degradation of ALK2; knockdown of Smad6 or Smurf1 prevents metformin-induced reduction of ALK2 levels, placing the Smad6-Smurf1 complex as a mediator of AMPK-induced ALK2 degradation.\",\n      \"method\": \"AMPK activators/inhibitors, siRNA knockdown of Smad6/Smurf1, co-immunoprecipitation, proteasome inhibitor assays, iPS cell osteogenic differentiation\",\n      \"journal\": \"Biochimica et Biophysica Acta: Molecular Cell Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, siRNA rescue experiment, functional differentiation assay, single lab\",\n      \"pmids\": [\"28847510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Smad6 and Smad7 bind simultaneously to discrete non-overlapping regions of Pellino-1 via distinct portions of their MH2 domains, and combined knockdown of both Smad6 and Smad7 further reduces TGF-β1 anti-inflammatory activity compared to single knockdown.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, double siRNA knockdown, NF-κB reporter assays\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, double knockdown functional assay, single lab\",\n      \"pmids\": [\"20171181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"JNK1 (but not JNK2) activation decreases binding of inhibitory Smad6 to BMPR-I and reciprocally increases Smad1 binding to BMPR-I, thereby increasing cellular responsiveness to BMP-2 and promoting osteoblast differentiation.\",\n      \"method\": \"JNK gain-of-function and loss-of-function, receptor binding assays, phospho-Smad1 assays, osteoblast differentiation (mineralized nodule formation)\",\n      \"journal\": \"Journal of Bone and Mineral Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with binding and functional differentiation assays, single lab\",\n      \"pmids\": [\"21542012\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SMAD6 is an inhibitory SMAD that negatively regulates BMP/TGF-β superfamily signaling through multiple mechanisms: it binds type I BMP receptors (preferentially ALK-3/6) to block R-Smad phosphorylation, acts as a Smad4 decoy by binding phosphorylated Smad1 to prevent Smad1-Smad4 complex formation, and functions in the nucleus as a transcriptional corepressor by interacting with Hoxc-8 and recruiting CtBP via its PLDLS motif; beyond canonical Smad signaling, SMAD6 suppresses non-canonical TGF-β/BMP pathways by binding TAK1 and recruiting the deubiquitinase A20 to TRAF6, inhibits TLR/IL-1R inflammation by binding Pellino-1 and mediating Smurf1/2-dependent MyD88 degradation (potentiated by PRMT1-mediated arginine methylation of Smad6), interacts with transcription factors (Runx2, Tbx6, Dlx3, GR) to recruit Smurf1 for their ubiquitin-proteasome degradation, and is itself regulated by monoubiquitination at K174 by UBE2O (reducing receptor binding) and by Arkadia-mediated degradation; in vivo, Smad6 is essential for cardiovascular development, endochondral ossification, vascular homeostasis downstream of Notch1, and hematopoietic stem cell regulation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SMAD6 is an inhibitory SMAD that serves as a negative-feedback brake on BMP/TGF-β superfamily signaling, acting at the receptor, in the cytoplasm, and within the nucleus [#0, #1]. At the membrane it forms stable associations with type I receptors to block R-Smad phosphorylation, with selectivity for ALK-3/6 over ALK-1/2 dictated by residues in the receptor kinase N-lobe [#0, #14], and it additionally acts as a 'Smad4 decoy' by binding receptor-phosphorylated Smad1 to prevent productive Smad1–Smad4 complex formation [#1]. In the nucleus SMAD6 functions as a transcriptional corepressor: it complexes with the homeodomain factor Hoxc-8 to block Smad1-driven transcription [#4] and recruits the corepressor CtBP through a PLDLS motif in its linker to repress BMP-induced Id1 [#8]. SMAD6 also extends beyond canonical Smad signaling to suppress non-canonical and inflammatory cascades, binding TAK1 to block BMP2-induced p38 activation [#6], recruiting the deubiquitinase A20 to TRAF6 to abolish K63-linked ubiquitination [#16], and binding Pellino-1 to disrupt the IRAK1–Pellino-1–TRAF6 complex and dampen NF-κB activation downstream of IL-1R/TLR [#11]. A recurring mechanism is SMAD6-dependent recruitment of the E3 ligases Smurf1/2 to direct ubiquitin-proteasome degradation of bound partners, including Runx2, Tbx6, MyD88, and PIAS3 [#9, #15, #17, #22]. SMAD6 activity is itself tuned by post-translational modification — PRMT1-mediated arginine methylation potentiates its anti-inflammatory MyD88-degrading function [#23], UBE2O-mediated monoubiquitination at K174 impairs receptor binding [#20], and Arkadia-mediated ubiquitination targets SMAD6 for degradation to relieve BMP inhibition [#21]. In vivo, Smad6 is essential for cardiovascular development and homeostasis [#7], for limiting BMP signaling during endochondral ossification [#18], and for endothelial flow responses downstream of Notch1 [#24].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established SMAD6 as a negative regulator of TGF-β superfamily signaling acting at the receptor level, answering how the pathway is intrinsically restrained.\",\n      \"evidence\": \"Co-IP and phosphorylation assays in mammalian cells showing receptor association and blocked R-Smad phosphorylation\",\n      \"pmids\": [\"9335505\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor selectivity (ALK subtypes) not yet defined\", \"Mechanism of decoy versus receptor block not distinguished\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined a distinct cytoplasmic mechanism—competition with Smad4 for phospho-Smad1—showing SMAD6 inhibits downstream of receptor phosphorylation, not only at the receptor.\",\n      \"evidence\": \"Binding/Co-IP assays in Xenopus embryos and mammalian cells with functional reporters\",\n      \"pmids\": [\"9436979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the Smad1–Smad6 complex unresolved\", \"Relative contribution of decoy versus receptor mechanisms in vivo unclear\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed SMAD6 expression is induced by the very ligands it antagonizes, framing it as a negative-feedback component of BMP/TGF-β signaling.\",\n      \"evidence\": \"Northern blot and RT-PCR after TGF-β, activin, BMP-2/7 and EGF stimulation in multiple cell lines\",\n      \"pmids\": [\"9712726\", \"9514869\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factors mediating induction not yet identified\", \"Single-lab transcriptional readouts\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified the cis and trans elements driving feedback induction, mapping a BMP-Smad1/5-Smad6 circuit and a nuclear corepressor role.\",\n      \"evidence\": \"Promoter mutagenesis/EMSA defining the PBE; yeast two-hybrid, Co-IP and EMSA linking SMAD6 to Hoxc-8\",\n      \"pmids\": [\"10692396\", \"10722652\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide SMAD6 target gene set not defined\", \"How nuclear and receptor functions are partitioned unclear\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Extended SMAD6 inhibition to a non-canonical branch (TAK1-p38) and established an essential in vivo cardiovascular role.\",\n      \"evidence\": \"TAK1 Co-IP with dominant-negative kinase and apoptosis assays; Smad6 knockout mice with cardiovascular phenotypes\",\n      \"pmids\": [\"10748100\", \"10655064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of SMAD6-TAK1 inhibition not defined\", \"Cell-type-specific contributions to cardiovascular phenotype not dissected\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Pinpointed the corepressor recruitment mechanism for nuclear repression via the PLDLS-CtBP interaction.\",\n      \"evidence\": \"Site-directed PLDLS mutagenesis with Co-IP and Id1 reporter assays\",\n      \"pmids\": [\"14645520\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Range of promoters subject to CtBP-dependent repression unknown\", \"Whether CtBP recruitment cooperates with R-Smad binding unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Revealed SMAD6 as an adaptor that targets transcription factors (Runx2) and nuclear receptors (GR) for Smurf1-mediated degradation or corepressor-mediated silencing, broadening its effector repertoire.\",\n      \"evidence\": \"Co-IP, degradation/ubiquitination assays for Runx2; domain mapping, HDAC3 recruitment and in vivo adenoviral assays for GR; OAZ-driven Smad6 induction by ChIP\",\n      \"pmids\": [\"16299379\", \"16249187\", \"16373339\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specificity determinants for substrate selection unclear\", \"Single-lab Co-IP and degradation evidence\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established SMAD6 as an anti-inflammatory node linking TGF-β/BMP signaling to IL-1R/TLR-NF-κB suppression and identified covalent modification of SMAD6 itself.\",\n      \"evidence\": \"Pellino-1 Co-IP/domain mapping with NF-κB reporters; PrKX in vitro kinase assay; PRMT1 in vitro methylation with MS; Dlx3 Co-IP/EMSA\",\n      \"pmids\": [\"16951688\", \"16491121\", \"17118358\", \"16687405\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of R74 methylation not established at this stage\", \"Interplay of modifications not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined receptor selectivity at residue resolution, explaining why SMAD6 preferentially restrains ALK-3/6 signaling.\",\n      \"evidence\": \"Mutagenesis of ALK-3 kinase-domain residues with reporter and binding assays\",\n      \"pmids\": [\"17493940\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural complex of SMAD6 with receptor not solved\", \"Single-lab mapping\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Generalized the Smurf1-recruitment mechanism to additional developmental transcription factors (Tbx6), reinforcing SMAD6 as a degradation adaptor.\",\n      \"evidence\": \"Co-IP, domain mapping, ubiquitin-proteasome degradation and reporter assays with siRNA validation\",\n      \"pmids\": [\"19561075\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance to Myf-5 regulation untested\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved distinct biochemical mechanisms for inflammatory suppression—A20 recruitment to TRAF6 and Smurf1/2-mediated MyD88 degradation—and confirmed essential in vivo roles in skeletal and neural development.\",\n      \"evidence\": \"Ubiquitination/Co-IP assays for A20-TRAF6 and MyD88; Smad6 knockout growth-plate histology; in ovo chick knockdown for spinal cord; Runx1-driven enhancer ChIP; JNK1 receptor-binding assays\",\n      \"pmids\": [\"24096742\", \"21897371\", \"21681813\", \"21730158\", \"21576367\", \"21542012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination between SMAD6's many parallel mechanisms in a single cell unclear\", \"Wnt/β-catenin inhibition mechanism only partly mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed SMAD6 activity is gated by monoubiquitination, providing a switch that relieves receptor inhibition.\",\n      \"evidence\": \"Proteomic screen, in vitro ubiquitination with K174/C885 mutagenesis, and BMP7-adipogenesis assays\",\n      \"pmids\": [\"23455153\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Deubiquitinase reversing K174 modification unknown\", \"Physiological triggers of UBE2O activity undefined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified Arkadia-mediated degradation as a route to inactivate SMAD6 and positively tune BMP signaling.\",\n      \"evidence\": \"Ubiquitination/degradation assays with Arkadia C937A mutant and knockout MEFs\",\n      \"pmids\": [\"25762727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signals controlling Arkadia targeting of SMAD6 unknown\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended SMAD6 functions into oncogenic STAT3 signaling and refined the methylation mechanism as functionally consequential for inflammation.\",\n      \"evidence\": \"PIAS3 Co-IP/domain mapping and ubiquitination in glioma cells; PRMT1 methylation-site mutagenesis with periodontitis model\",\n      \"pmids\": [\"29950561\", \"29420098\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Context determining pro- versus anti-tumor roles unclear\", \"Single-lab functional assays\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed SMAD6 within an endothelial mechanotransduction axis, linking it to flow-mediated barrier and alignment responses downstream of Notch1.\",\n      \"evidence\": \"Notch1-SMAD6-PCDH12 epistasis with flow alignment, barrier and gene-expression assays\",\n      \"pmids\": [\"33779885\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical link between SMAD6 and PCDH12 not defined\", \"Single-lab epistasis\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SMAD6's many parallel activities—receptor inhibition, decoy function, transcriptional corepression, degradation-adaptor roles, and inflammatory suppression—are integrated and prioritized within a single cell, and the structural basis of its key interactions, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of SMAD6-receptor or SMAD6-Smad1 complexes in the corpus\", \"Hierarchy among cytoplasmic versus nuclear functions undefined\", \"Disease-causing human mutations not addressed in the timeline\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 8, 10, 26]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [9, 15, 17, 22]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 11, 16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [9, 15, 17, 22]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [4, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 8, 13, 22, 26]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 14, 30]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 11, 16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 14]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [11, 16, 17]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 8, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [9, 15, 17, 20, 21]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 18, 24]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SMAD1\", \"SMURF1\", \"TAK1\", \"TRAF6\", \"Pellino-1\", \"MyD88\", \"Runx2\", \"CtBP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}