{"gene":"SMURF2","run_date":"2026-06-10T07:46:36","timeline":{"discoveries":[{"year":2000,"finding":"Smurf2 is a C2-WW-HECT domain E3 ubiquitin ligase that constitutively associates with Smad7; this Smad7-Smurf2 complex is exported from the nucleus and recruited to the activated TGFβ receptor, where it targets both the receptor and Smad7 for degradation via proteasomal and lysosomal pathways. Smad7 functions as an adaptor in this E3 ligase complex.","method":"Co-immunoprecipitation, subcellular fractionation, receptor degradation assays, dominant-negative and RNAi expression studies","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, functional rescue experiments, multiple orthogonal methods, foundational paper replicated by multiple labs","pmids":["11163210"],"is_preprint":false},{"year":2000,"finding":"Smurf2 selectively interacts with receptor-regulated Smads (Smad1, Smad2, Smad3 but not Smad4) and preferentially targets Smad1 and Smad2 for ubiquitination and proteasome-mediated degradation; HECT catalytic activity is required. Smurf2 shows higher binding affinity to activated (phosphorylated) Smad2 upon TGF-β stimulation.","method":"Yeast two-hybrid, in vitro binding assays, in vivo ubiquitination assays, proteasome inhibitor experiments, Xenopus embryo overexpression","journal":"The Journal of biological chemistry / Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — independently replicated in two labs (PMID 11016919 and 11158580) with in vitro assays and mutagenesis","pmids":["11016919","11158580"],"is_preprint":false},{"year":2001,"finding":"TGF-β stimulation induces assembly of a Smad2-Smurf2 ubiquitin ligase complex via interaction of the Smad2 proline-rich PPXY motif with WW domains of Smurf2; this complex associates with the transcriptional co-repressor SnoN and targets it for ubiquitin-mediated proteasomal degradation.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, proteasome inhibitor experiments, domain mapping","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination, domain mutant studies, high-impact replicated finding","pmids":["11389444"],"is_preprint":false},{"year":2005,"finding":"The N-terminal domain (NTD) of Smad7 stimulates Smurf2 ubiquitin ligase activity by recruiting the E2 enzyme UbcH7 to the HECT domain. A 2.1 Å crystal structure of the Smurf2 HECT domain revealed a suboptimal E2 binding pocket; mutagenesis to optimize this pocket generated a constitutively active HECT domain that inhibits TGFβ signaling independently of Smad7.","method":"X-ray crystallography (2.1 Å), in vitro ubiquitination assays, site-directed mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure combined with functional mutagenesis and in vitro reconstitution","pmids":["16061177"],"is_preprint":false},{"year":2007,"finding":"An intramolecular interaction between the C2 and HECT domains of Smurf2 autoinhibits its ubiquitin ligase activity by binding near the catalytic cysteine and interfering with ubiquitin thioester formation; Smad7 binding to the HECT domain antagonizes this inhibitory C2-HECT interaction to activate Smurf2.","method":"NMR spectroscopy, in vitro ubiquitination assays, domain deletion/mutagenesis, cell-based stability assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structural analysis plus in vitro reconstitution and mutagenesis in a single rigorous study","pmids":["17719543"],"is_preprint":false},{"year":2006,"finding":"NMR solution structure of the Smurf2 WW3 domain in complex with the Smad7 PY motif peptide revealed that WW3 (which has Phe instead of the canonical Trp) binds both the core PY motif and six C-terminal residues (PY-tail), defining an expanded WW domain recognition surface that provides substrate specificity.","method":"NMR spectroscopy (solution structure determination), binding affinity measurements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR solution structure with functional validation of binding interface","pmids":["16641086"],"is_preprint":false},{"year":2007,"finding":"Smurf2 ubiquitinates inactive Rap1B and initiates its proteasomal degradation in hippocampal neurons; this restricts Rap1B to the tip of a single neurite (the future axon), establishing neuronal polarity. Smurf1 and Smurf2 have distinct roles: Smurf1 regulates Rho/neurite growth and Smurf2 regulates Rap1B/polarity.","method":"RNAi knockdown in neurons, in vivo ubiquitination assay, fluorescence imaging of Rap1B localization, rescue experiments","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with defined substrate and phenotype, localization imaging, ubiquitination assay","pmids":["17318188"],"is_preprint":false},{"year":2007,"finding":"mPar3 links Smurf2 to Kinesin-2 and is required to localize Smurf2 to neuronal growth cones; disruption of mPar3–Kinesin-2 or mPar3–Smurf2 interactions prevents restriction of Rap1B to the axon and abolishes neuronal polarity.","method":"Co-immunoprecipitation, RNAi knockdown, dominant-negative interference, fluorescence localization in neurons","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and RNAi with phenotypic readout, single lab","pmids":["17906294"],"is_preprint":false},{"year":2004,"finding":"Smurf2 up-regulation is a specific consequence of telomere attrition in human fibroblasts, and ectopic Smurf2 expression at physiological levels is sufficient to induce senescence. The senescence-inducing function requires a novel activity distinct from Smurf2's E3 ligase activity, and involves recruitment of the Rb and p53 pathways; p21 is elevated but Smurf2-induced senescence is p21-independent.","method":"Retroviral overexpression, BrdU incorporation, senescence-associated β-galactosidase staining, gene expression analysis, E3-dead mutant rescue","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods demonstrating gain-of-function phenotype, E3-inactive mutant controls","pmids":["15574587"],"is_preprint":false},{"year":2008,"finding":"Smurf2 localizes to the centrosome, mitotic midbody, and centromeres. Smurf2 depletion causes misaligned/lagging chromosomes, premature anaphase, and defective cytokinesis. Smurf2 is required for the spindle assembly checkpoint (SAC): its inactivation leads to enhanced polyubiquitination and degradation of Mad2, mislocalizing Mad2 and preventing prometaphase arrest; silencing Cdc20 in Smurf2-depleted cells rescues cyclin B and securin accumulation.","method":"siRNA knockdown, immunofluorescence localization, flow cytometry, co-immunoprecipitation, nocodazole arrest assays, epistasis (Cdc20 silencing rescue)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization, loss-of-function phenotype, substrate (Mad2) identification, genetic epistasis with Cdc20","pmids":["18852296"],"is_preprint":false},{"year":2008,"finding":"Smurf2 mediates ubiquitin-dependent degradation of Smurf1; Smurf2 interacts with Smurf1 and induces its ubiquitination and proteasomal degradation, whereas Smurf1 does not reciprocally degrade Smurf2. Knockdown of Smurf2 in breast cancer cells increases Smurf1 protein and enhances cell migration and bone metastasis.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA knockdown, migration/invasion assays, in vivo bone metastasis model","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination, functional phenotype in vitro and in vivo","pmids":["18927080"],"is_preprint":false},{"year":2010,"finding":"Smurf2 is an E3 ubiquitin ligase for Axin; it interacts with Axin, promotes its ubiquitination specifically at Lys505 (identified by mass spectrometry), and targets it for proteasomal degradation. Knockdown of endogenous Smurf2 increases endogenous Axin levels and reduces β-catenin/Tcf reporter activity.","method":"Co-immunoprecipitation, in vitro/in vivo ubiquitination assay, mass spectrometry, shRNA knockdown, luciferase reporter assay, K505R mutant resistance experiment","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro ubiquitination, MS-identified ubiquitination site, site-directed mutagenesis resistance, endogenous knockdown phenotype","pmids":["20858899"],"is_preprint":false},{"year":2011,"finding":"In vivo (Smurf2 knockout mice), Smurf2 induces multiple mono-ubiquitination of Smad3 at MH2 domain lysine residues rather than polyubiquitination/degradation; this mono-ubiquitination inhibits Smad3 complex formation and attenuates TGF-β signaling. Phosphorylation of Smad3 at T179 enhances Smurf2-Smad3 interaction and Smad3 ubiquitination.","method":"Smurf2 knockout mouse generation, primary MEF/dermal fibroblast assays, in vivo ubiquitination assays, site mapping, phosphorylation-deficient mutant studies","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic KO model with primary cells, in vivo ubiquitination with site mapping and phospho-mutant validation","pmids":["22045334"],"is_preprint":false},{"year":2012,"finding":"Smurf2 targets RNF20 for proteasomal degradation, thereby regulating monoubiquitination of histone H2B and trimethylation of H3K4 and H3K79. Smurf2 and RNF20 co-localize at γ-H2AX foci of double-strand DNA breaks. Smurf2 knockout mice show dysregulated DNA damage response, genomic instability, and increased cancer susceptibility.","method":"Smurf2 knockout mouse model, co-immunoprecipitation, immunofluorescence co-localization, histone modification assays, proteasome inhibitor experiments","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse, co-IP, co-localization, multiple substrates and phenotypes across mouse and human cells","pmids":["22231558"],"is_preprint":false},{"year":2011,"finding":"Smurf2 mediates ubiquitination and degradation of Id1 and Id3 in senescent cells; Smurf2-mediated ubiquitination of Id1 (and its consequent degradation) is the mechanism by which Smurf2 up-regulates p16 expression during senescence.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA knockdown, p16 reporter assays","journal":"Aging cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay, single lab, two orthogonal methods","pmids":["21933340"],"is_preprint":false},{"year":2013,"finding":"Smurf2 is the E3 ubiquitin ligase responsible for polyubiquitination and proteasomal degradation of EZH2 in human mesenchymal stem cells, which is required for neuron differentiation; EZH2 degradation by Smurf2 enables PPARγ expression to drive differentiation.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA/shRNA knockdown, ChIP-on-chip, gene microarray, in vivo stroke model","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, KD with phenotype, single lab","pmids":["23526793"],"is_preprint":false},{"year":2013,"finding":"Smurf2 interacts with VISA/MAVS and targets it for K48-linked polyubiquitination and proteasomal degradation, negatively regulating virus-triggered type I IFN signaling. The E3 ligase activity of Smurf2 (C716A mutant is inactive) is required for this negative regulation.","method":"Co-immunoprecipitation, in vivo ubiquitination assay (K48-linkage specific), Smurf2 KO/KD experiments, IFN-β reporter assays, C716A catalytic mutant","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, linkage-specific ubiquitination, catalytic mutant, KO and KD with functional readout","pmids":["24729608"],"is_preprint":false},{"year":2013,"finding":"Smurf2 mediates ubiquitination and degradation of YY1; Smurf2 interacts with YY1 via the PPxY motif of YY1, induces its polyubiquitination, and shortens YY1 half-life, thereby reducing YY1-mediated transcriptional activation. In B-cell lymphoma context, Smurf2 deficiency enhances YY1-mediated transactivation of c-Myc.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, half-life measurement, PPxY mutant analysis, Smurf2 KO mouse model, luciferase reporter assay","journal":"Nature communications / Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple labs (PMIDs 24121673 and 24803334), reciprocal Co-IP, ubiquitination assay with domain mapping","pmids":["24121673","24803334"],"is_preprint":false},{"year":2014,"finding":"Smurf2 forms an active E3:E2 complex with UBCH5 that maintains KRAS protein stability by mediating K48-linked monoubiquitination of UBCH5 at K144. This SMURF2:UBCH5 complex promotes degradation of β-TrCP1, an E3 ligase that itself degrades KRAS; loss of SMURF2 accumulates β-TrCP1 leading to KRAS degradation.","method":"siRNA/shRNA knockdown, overexpression rescue, in vivo ubiquitination assay, protein half-life measurements, domain mutagenesis (P residues in UBCH5)","journal":"Neoplasia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis with domain mutants, in vivo ubiquitination, single lab","pmids":["24709419"],"is_preprint":false},{"year":2014,"finding":"Akt phosphorylates Smurf2 and promotes ubiquitin/proteasome-mediated degradation of Smurf2 itself, thereby increasing Runx2 protein stability and transcriptional activity. This establishes an Akt→Smurf2→Runx2 axis regulating osteoblast differentiation.","method":"Co-immunoprecipitation, phosphorylation assays, ubiquitination assays, Western blot, overexpression/knockdown experiments","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, phosphorylation and ubiquitination assays, single lab","pmids":["24961731"],"is_preprint":false},{"year":2015,"finding":"Smurf2 is sumoylated by the SUMO E2 enzyme Ubc9 and SUMO E3 ligase PIAS3 at Lys26 and Lys369; sumoylation enhances Smurf2's ability to degrade the TGFβ receptor and suppresses TGFβ-induced EMT. PIAS3 associates with Smurf2 and promotes its sumoylation.","method":"Co-immunoprecipitation, sumoylation assays, site-directed mutagenesis (K26R/K369R), 3D organoid EMT assay, siRNA knockdown","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, site-specific sumoylation mapping with mutants, functional 3D organoid assay, single lab","pmids":["26679521"],"is_preprint":false},{"year":2015,"finding":"USP15 deubiquitinates SMURF2 at Lys734 (a residue required for catalytic activity), thereby enhancing SMURF2's E3 ligase activity and increasing TGFβ receptor stability and downstream signaling. USP15 and SMURF2 form a regulatory axis within the TGFβ pathway.","method":"Co-immunoprecipitation, proteomic/mass spectrometry analysis of ubiquitination sites, in vivo ubiquitination assays, TGFβ pathway reporter assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, MS-identified ubiquitination site, functional assays, single lab","pmids":["26435193"],"is_preprint":false},{"year":2009,"finding":"Ectopically expressed Smurf2 in chondrocytes interacts with GSK-3β, induces its ubiquitination and proteasomal degradation, and thereby upregulates β-catenin levels, activating articular chondrocyte maturation.","method":"Immunoprecipitation, ubiquitination assay, Col2a1-Smurf2 transgenic mouse ex vivo chondrocytes, Western blot","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay in transgenic primary cells, single lab","pmids":["19481076"],"is_preprint":false},{"year":2010,"finding":"Smurf2 physically associates with NEDD9/HEF1 and is required for NEDD9 protein stability by protecting it from polyubiquitination and proteasomal degradation; Smurf2 depletion reduces NEDD9 levels, prevents Aurora A activation at the G2/M boundary, and causes mitotic entry delay.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, Aurora A kinase activity assays, flow cytometry","journal":"Cell division","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, kinase activity readout, single lab","pmids":["20825672"],"is_preprint":false},{"year":2016,"finding":"AIMP2/p38, upon TGF-β-induced phosphorylation at S156 and nuclear translocation, binds Smurf2 in the nucleus to enhance ubiquitination of FBP (FUBP1). AIMP2 also inhibits nuclear export of Smurf2 to sustain TGFβ tumor-suppressive signaling. An oncogenic AIMP2 mutation abrogates this nuclear interaction with Smurf2.","method":"Co-immunoprecipitation, in vivo ubiquitination assays, subcellular fractionation, domain mutagenesis, in vivo tumor formation assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, subcellular localization experiments, single lab","pmids":["27197155"],"is_preprint":false},{"year":2015,"finding":"TRAF4 recruits SMURF2 to the IL-25 receptor complex; TRAF4-SMURF2 mediates degradation of DAZAP2 (an IL-25R inhibitory molecule), enabling ACT1 recruitment to IL-25R and IL-25 signaling. This is a critical initiating event for IL-25-driven type 2 allergic responses.","method":"Co-immunoprecipitation, ubiquitination assays, Traf4 knockout mouse model, IL-25 signaling assays, siRNA knockdown","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, KO mouse with functional readout, single lab","pmids":["25681341"],"is_preprint":false},{"year":2017,"finding":"Smurf2 physically interacts with Topoisomerase IIα (Topo IIα), modifies its ubiquitination status to protect it from proteasomal degradation (stabilizing rather than degrading), and is a physiologic regulator of Topo IIα levels. Smurf2-depleted cells cannot resolve DNA catenanes and form pathological chromatin bridges during mitosis.","method":"Co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown, chromosomal bridge quantification, Topo IIα rescue experiments","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, KD with rescue, single lab","pmids":["28611047"],"is_preprint":false},{"year":2017,"finding":"SMURF2 regulates RANKL expression in osteoblasts by disrupting the interaction between SMAD3 and the vitamin D receptor through altering SMAD3 ubiquitination; Smurf2-deficient mice exhibit severe osteoporosis with increased osteoclast numbers driven by osteoblast-elevated RANKL. Osteoblast-selective Smurf2 deletion recapitulates the full osteoporosis phenotype.","method":"Conditional/germline knockout mouse model, co-immunoprecipitation, ubiquitination assays, RANKL expression analysis, osteoclast number quantification","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with cell-type-specific deletion, mechanistic co-IP and ubiquitination, clear cellular phenotype","pmids":["28216630"],"is_preprint":false},{"year":2017,"finding":"RNF11 directly competes with SMAD7 for binding to SMURF2 in a mutually exclusive, proline-rich domain-dependent manner; when RNF11 sequesters SMURF2 on endomembranes, it activates SMURF2 E3 ligase activity while reducing SMURF2 auto-ubiquitination, antagonizing the SMAD7-mediated downregulation of TGFβ signaling.","method":"In vitro reconstitution of SMURF2·RNF11 complex, in vitro binding competition assays, co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown with TGFβ gene reporter assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstitution, binding competition, co-IP, functional downstream readouts in one study","pmids":["28292929"],"is_preprint":false},{"year":2018,"finding":"Smurf2 directly binds, ubiquitinates, and promotes autophagic-lysosomal degradation (not solely proteasomal) of lamin A and progerin in a dose- and E3 ligase-dependent manner. Acute Smurf2 overexpression in progeria fibroblasts significantly reduces nuclear deformability.","method":"Co-immunoprecipitation, in vivo ubiquitination assays, autophagy/lysosome inhibitor experiments, Smurf2 overexpression/depletion, nuclear morphology quantification in progeria cells","journal":"Aging cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination with pathway specificity, functional rescue in disease model, single lab","pmids":["29405587"],"is_preprint":false},{"year":2012,"finding":"Smurf2 deficiency in mice impairs senescence of primary MEFs (reduced p16) and increases susceptibility to spontaneous B-cell lymphoma; premalignant spleens show defective senescence responses, genetically linking Smurf2-mediated senescence regulation to tumor suppression in vivo.","method":"Smurf2 knockout mouse generation, primary MEF senescence assays, tumor incidence monitoring, immunohistochemistry","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO model with in vivo tumor phenotype and primary cell mechanistic data","pmids":["22552287"],"is_preprint":false},{"year":2019,"finding":"SMURF2 interacts with ChREBP and promotes its ubiquitination and proteasomal degradation; loss of SMURF2 increases ChREBP, enhances aerobic glycolysis, and promotes colorectal cancer cell proliferation. AKT acts as an upstream suppressor of SMURF2 to protect ChREBP from degradation.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA/overexpression experiments, glycolysis/oxygen consumption measurements, in vivo xenograft","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, functional metabolic readouts, single lab","pmids":["31409643"],"is_preprint":false},{"year":2019,"finding":"SMURF2 interacts with SATB1 and promotes its ubiquitination and degradation; SMURF2 is itself negatively regulated by the deubiquitinase USP47, establishing a USP47-SMURF2-SATB1 axis controlling colon cancer cell proliferation.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, mouse xenograft model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab","pmids":["30742943"],"is_preprint":false},{"year":2019,"finding":"TRAF4 acts as an E3 ubiquitin ligase that mediates K48-linked ubiquitination of Smurf2 at the K119 site, promoting Smurf2 proteasomal degradation, thereby increasing BMP/TGF-β signaling and osteogenic differentiation of mesenchymal stem cells.","method":"Co-immunoprecipitation, in vitro/in vivo ubiquitination assays, K119 site-directed mutagenesis, osteogenic differentiation assays, in vivo bone formation model","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, in vitro ubiquitination with site-directed mutant, in vivo model, single lab","pmids":["31076633"],"is_preprint":false},{"year":2016,"finding":"Nedd8 targets Smurf2 for neddylation, which promotes Smurf2 degradation; Smurf2 itself exerts Nedd8 ligase activity, and Smurf1 neddylation activates its ubiquitin ligase activity.","method":"In vivo neddylation assays, co-immunoprecipitation, Western blot stability assays","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method (neddylation assay), limited mechanistic detail in abstract","pmids":["27086113"],"is_preprint":false},{"year":2019,"finding":"PRMT5 sustains RNF168 expression; loss of PRMT5 (in MTAP-deficient glioblastoma) reduces RNF168, allowing SMURF2 to destabilize H2AX. RNF168 and SMURF2 act as stabilizer and destabilizer of H2AX respectively via dynamic interactions with H2AX, defining a PRMT5-RNF168-SMURF2 cascade controlling H2AX proteostasis.","method":"Co-immunoprecipitation, ubiquitination assays, genetic KD experiments, DNA damage response assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, genetic epistasis, single lab","pmids":["31533041"],"is_preprint":false},{"year":2020,"finding":"SMURF2 interacts with SIRT1 and mediates its ubiquitination and proteasomal degradation; depletion of SMURF2 leads to SIRT1 upregulation and promotes colorectal cancer tumor formation and growth in vitro and in vivo.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, in vivo tumor xenograft","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab","pmids":["32361710"],"is_preprint":false},{"year":2020,"finding":"Dishevelled (DVL), a key Wnt pathway transducer, activates Smurf2 E3 ligase activity and is itself a substrate of Smurf2; DVL deficiency phenocopies Smurf2 absence, leading to increased R-Smad phosphorylation. Smurf2 also ubiquitinates Prickle1 (Wnt/PCP component). Both SMAD7 and DVL activate Smurf2 through a common mechanism.","method":"Co-immunoprecipitation, in vivo ubiquitination assays, DVL triple-knockout HEK293 cells, R-Smad phosphorylation assays","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, genetic KO cell line, single lab","pmids":["32392721"],"is_preprint":false},{"year":2020,"finding":"Smurf2 negatively regulates BMP/Smad1/5 signaling by inducing ubiquitination of Smad1/5; Smurf2-deficient mice show enhanced BMP2-induced ectopic bone formation with greater bone mass and osteoblast numbers.","method":"Smurf2 knockout mouse, ectopic bone formation assay with rhBMP2, in vivo ubiquitination assay, primary bone marrow stromal cell differentiation assays","journal":"Bone research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO model, in vivo ubiquitination, bone formation phenotype, single lab","pmids":["33298874"],"is_preprint":false},{"year":2008,"finding":"Smurf2 interacts with TRAF2 (identified by yeast two-hybrid), and TRAF2 overexpression triggers Smurf2 ubiquitination and formation of a TNF-R2/Smurf2 complex; Smurf2 in turn promotes TNF-R2 ubiquitination and relocalization to a detergent-insoluble fraction, which is associated with enhanced TNF-R2-induced JNK activation without affecting NF-κB.","method":"Yeast two-hybrid, co-immunoprecipitation, ubiquitination assays, detergent fractionation, JNK/NF-κB signaling assays","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — yeast two-hybrid plus single co-IP, limited mechanistic follow-up, single lab","pmids":["18671942"],"is_preprint":false},{"year":2011,"finding":"SMURF2 interacts with EGFR and promotes its ubiquitination (non-degradative/stabilizing), protecting EGFR from c-Cbl-mediated degradation. SMURF2 knockdown destabilizes EGFR, triggers autophagy, and reduces clonogenic survival of EGFR-expressing cancer cells.","method":"Co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown, autophagic response assays, in vivo tumor model","journal":"Neoplasia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab; replicated in follow-up study PMID 32669362","pmids":["21750651","32669362"],"is_preprint":false},{"year":2020,"finding":"SMURF2-UBCH5 E3-E2 complex mediates polyubiquitination of L858R/T790M EGFR at four specific lysine residues, stabilizing mutant EGFR by membrane retention and competing with acetylation-driven receptor internalization to lysosomes; SMURF2 knockdown increases lysosomal sorting of EGFR.","method":"In vitro and in vivo ubiquitination assays, mass spectrometry (ubiquitination site mapping), superresolution microscopy, acetylation-mimicking mutant (K→Q), siRNA knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro ubiquitination, MS site identification, mutagenesis, superresolution imaging, multiple orthogonal methods","pmids":["32669362"],"is_preprint":false},{"year":2022,"finding":"SMURF2 phosphorylation at Thr249 activates its E3 ubiquitin ligase activity; inactivation of this phosphorylation site (T249A mutant) increases TGF-β receptor (TGFBR1) protein stability, augments glioma stem cell (GSC) stemness and tumorigenicity, phenocopying SMURF2 silencing.","method":"Phospho-specific mutant (T249A) overexpression, TGFBR1 stability assays, GSC sphere and tumor formation assays, TGFBR1 knockdown rescue experiments","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-mutant functional analysis, substrate stability assay, genetic rescue, single lab","pmids":["35017630"],"is_preprint":false},{"year":2022,"finding":"FMO2 binds CYP2J3 and disrupts CYP2J3 interaction with SMURF2 in the cytosol, leading to increased cytoplasm-to-nucleus translocation of SMURF2 and consequent inhibition of SMAD2/3 signaling and cardiac fibrosis; this antifibrotic mechanism is independent of FMO2 enzymatic activity.","method":"Co-immunoprecipitation, subcellular fractionation, CRISPR KO rats, gain-of-function lentivirus experiments, SMAD2/3 phosphorylation assays, cardiac fibrosis histology","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, genetic KO model, subcellular fractionation, multiple species validation, single lab","pmids":["35861735"],"is_preprint":false},{"year":2023,"finding":"SMURF2 ubiquitinates and promotes degradation of GSTP1 at early stages of ferroptosis; GSTP1 functions as a GPX4- and FSP1-independent ferroptosis defense by catalyzing GSH conjugation of 4-HNE and detoxifying lipid hydroperoxides. Genetic or pharmacological modulation of the SMURF2/GSTP1 axis sensitizes tumors to ferroptosis-inducing drugs.","method":"Proteomics (dynamics during ferroptosis), co-immunoprecipitation, in vivo ubiquitination assay, GSTP1 catalytic activity assays, genetic overexpression/KD, in vitro and in vivo drug sensitivity assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — proteomic discovery plus co-IP, ubiquitination assay, catalytic enzyme assay, in vivo validation, multiple methods","pmids":["38016474"],"is_preprint":false},{"year":2023,"finding":"SMURF2 acts as a bona fide E3 ligase for RACK1, adding K6, K33, and K48 ubiquitin chains to RACK1, resulting in its polyubiquitination and degradation. PCAF-mediated acetylation of RACK1 at K130 inhibits SMURF2-mediated RACK1 ubiquitination, stabilizing RACK1 and promoting ovarian cancer progression.","method":"Co-immunoprecipitation, in vivo ubiquitination assay (linkage-specific), acetylation assay, PCAF overexpression, in vivo tumor model","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, linkage-specific ubiquitination, acetylation crosstalk experiment, single lab","pmids":["37828084"],"is_preprint":false},{"year":2012,"finding":"TGF-β induces SIK1 expression via Smad-dependent transcription; SIK1 forms complexes with the TGFβ type I receptor and Smurf2, and both SIK1 kinase activity and Smurf2 ubiquitin ligase activity are required for proper TGFβ type I receptor turnover. Knockdown of SIK1 and Smurf2 enhances physiological TGFβ-induced epithelial growth arrest.","method":"Co-immunoprecipitation, kinase and ubiquitination assays, siRNA knockdown, receptor turnover assays, promoter mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, functional enzymatic assays, double-KD epistasis, single lab","pmids":["22378783"],"is_preprint":false},{"year":2004,"finding":"RNF11 recruits AMSH to Smurf2 for ubiquitination and degradation by the 26S proteasome; RNF11 binds AMSH independently of its RING-finger domain and PY motif, and AMSH ubiquitination requires both RNF11 and Smurf2.","method":"Co-immunoprecipitation, yeast two-hybrid, in vivo ubiquitination assay","journal":"Oncogene","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, limited mechanistic follow-up","pmids":["14755250"],"is_preprint":false},{"year":2019,"finding":"SMURF2 acts as an E3 ligase to mediate ubiquitination and degradation of RhoA; the oncoprotein AAMP stabilizes RhoA by binding to it and suppressing SMURF2-mediated RhoA ubiquitination and degradation, thereby promoting colorectal cancer cell migration and invasion.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, cell migration/invasion assays","journal":"Molecular therapy oncolytics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, limited mechanistic depth","pmids":["34901393"],"is_preprint":false},{"year":2020,"finding":"SMURF2 interacts with and promotes ubiquitination and degradation of PARP1; this interaction is enhanced under oxidative stress, and Smurf2-mediated PARP1 degradation reduces ROS and protects endothelial cells from apoptosis.","method":"Co-immunoprecipitation, in vivo ubiquitination assay, ROS/apoptosis assays in HUVECs","journal":"Journal of cellular and molecular medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, single study","pmids":["32167680"],"is_preprint":false},{"year":2017,"finding":"Smurf2 interacts with PDE4B and facilitates its degradation, thereby activating the cAMP-PKA-CREB signaling pathway, which transcriptionally upregulates miR-132 to suppress CTGF expression and attenuate liver fibrosis.","method":"Co-immunoprecipitation, Smurf2 transgenic mouse model, miRNA array, western blot, CREB signaling assays","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP and transgenic model, indirect mechanism through miRNA, single lab","pmids":["29100790"],"is_preprint":false},{"year":2019,"finding":"SMURF2 interacts with CNKSR2 and promotes its stabilization (protective ubiquitination against proteasomal degradation); Smurf2 knockdown decreases CNKSR2 and reduces PI3K-PTEN-AKT-FoxO3a-driven proliferation of breast cancer cells.","method":"Co-immunoprecipitation, surface plasmon resonance, indirect immunofluorescence, ubiquitination assays, siRNA knockdown, proliferation assays","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus SPR binding validation and ubiquitination assay, multiple orthogonal binding methods, single lab","pmids":["29534682"],"is_preprint":false},{"year":2019,"finding":"In normal cells and tissues, SMURF2 has a predominantly nuclear localization; in prostate and aggressive breast carcinomas, SMURF2 shows significantly increased cytoplasmic sequestration associated with disease progression. Biochemical studies showed SMURF2 is more stable in the cytoplasmic compartment, and 14-3-3 proteins are SMURF2 interactors that may affect its localization.","method":"Subcellular fractionation, immunohistochemistry of 666 tissue samples, co-immunoprecipitation (interactome), nuclear export inhibitor experiments","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — subcellular fractionation with large tissue cohort and co-IP interactome, single lab","pmids":["31003445"],"is_preprint":false}],"current_model":"SMURF2 is a HECT-domain E3 ubiquitin ligase whose activity is autoinhibited by an intramolecular C2–HECT interaction (relieved by Smad7 or Dishevelled binding) and modulated by phosphorylation (Thr249), sumoylation (K26/K369 by PIAS3), neddylation, and deubiquitination (by USP15 at K734); it forms substrate-recruiting complexes through its WW domains (recognizing PPxY motifs) and targets a broad array of proteins for ubiquitin-mediated degradation or stabilization, including TGFβ receptors (via Smad7 adaptor), Smad2/3 (mono- or poly-ubiquitination to attenuate signaling), Smad1/5 (BMP pathway), SnoN, RNF20, EZH2, YY1, Id1/3, Mad2, Axin, GSK-3β, GSTP1, VISA/MAVS, RACK1, lamin A/progerin, Topo IIα, EGFR, NEDD9, Smurf1, and others, while also protecting certain substrates (NEDD9, EGFR, CNKSR2, Topo IIα) from degradation; through these diverse substrate interactions SMURF2 regulates TGFβ/BMP signaling, neuronal polarity (via Rap1B ubiquitination localized by mPar3/Kinesin-2), the spindle assembly checkpoint (via Mad2 stabilization), telomere-dependent senescence, chromatin/epigenetic landscape (via RNF20/H2B-Ub/H3K4me3), DNA damage response, and ferroptosis resistance."},"narrative":{"mechanistic_narrative":"SMURF2 is a C2-WW-HECT domain E3 ubiquitin ligase that governs the strength and duration of TGFβ/BMP signaling and a broad program of cell-cycle, chromatin, and stress-response events through substrate-specific ubiquitination [PMID:11163210, PMID:11016919, PMID:11158580]. Its catalytic activity is held in check by an intramolecular C2–HECT interaction that occludes the catalytic cysteine and blocks ubiquitin-thioester formation; this autoinhibition is relieved when adaptor proteins such as Smad7—and, by a shared mechanism, Dishevelled—bind the HECT domain, while the Smad7 N-terminal domain further stimulates activity by recruiting the E2 UbcH7 into a suboptimal E2-binding pocket [PMID:16061177, PMID:17719543, PMID:32392721]. Substrate selection is achieved through its WW domains, which read PPxY/PY motifs via an expanded recognition surface that engages both the core PY motif and a C-terminal tail [PMID:16641086, PMID:24121673, PMID:24803334]. In the TGFβ axis, the Smad7-SMURF2 complex is exported to the activated receptor and degrades both receptor and Smad7 [PMID:11163210], SMURF2 ubiquitinates R-Smads (degradative for Smad1/2, multi-monoubiquitination of Smad3 that blocks complex formation) [PMID:11016919, PMID:11158580, PMID:22045334], and clears the co-repressor SnoN [PMID:11389444]; it also restrains BMP-driven Smad1/5 signaling [PMID:33298874]. Beyond this core pathway, SMURF2 controls mitotic fidelity by stabilizing Mad2 to enforce the spindle assembly checkpoint and by protecting Topoisomerase IIα to allow catenane resolution [PMID:18852296, PMID:28611047], and it shapes the chromatin and DNA-damage landscape by degrading RNF20 to set H2B-ubiquitination/H3K4-H3K79 methylation marks at double-strand breaks [PMID:22231558]. SMURF2 drives telomere-attrition-triggered senescence—a function genetically linked to tumor suppression in knockout mice that develop B-cell lymphoma [PMID:15574587, PMID:22552287]—and acts as a ferroptosis modulator by degrading the lipid-peroxide defense enzyme GSTP1 [PMID:38016474]. Its own abundance and activity are tuned by phosphorylation (Akt-driven degradation; Thr249-dependent activation), sumoylation by PIAS3/Ubc9 at K26/K369, USP15-mediated deubiquitination at K734, and competitive adaptor exchange between Smad7 and RNF11 [PMID:24961731, PMID:35017630, PMID:26679521, PMID:26435193, PMID:28292929]. Notably, SMURF2 acts as a stabilizer as well as a degrader for a subset of clients (EGFR, NEDD9, Topo IIα, CNKSR2), often via non-degradative ubiquitination [PMID:21750651, PMID:32669362, PMID:20825672, PMID:28611047, PMID:29534682].","teleology":[{"year":2000,"claim":"Established SMURF2's foundational role: how is TGFβ receptor signaling terminated? It works as a HECT E3 that, via the Smad7 adaptor, targets the activated receptor for degradation, and it directly degrades receptor-regulated Smads.","evidence":"Co-IP, subcellular fractionation, receptor degradation and ubiquitination assays; yeast two-hybrid and Xenopus overexpression","pmids":["11163210","11016919","11158580"],"confidence":"High","gaps":["Did not resolve how SMURF2 catalytic activity is regulated","Smad4 selectivity rationale unaddressed at structural level"]},{"year":2001,"claim":"Defined SMURF2 substrate-recruitment logic: TGFβ induces a Smad2-SMURF2 complex via Smad2 PPxY–WW interaction that degrades the co-repressor SnoN, extending SMURF2's reach to transcriptional regulators.","evidence":"Co-IP, in vivo ubiquitination, proteasome inhibition, domain mapping","pmids":["11389444"],"confidence":"High","gaps":["WW-domain structural basis of PY recognition not yet defined","In vivo relevance unaddressed"]},{"year":2005,"claim":"Explained how the Smad7 adaptor activates SMURF2 catalysis: the Smad7 NTD recruits UbcH7 to a suboptimal E2 pocket in the HECT domain, defined by a 2.1 Å crystal structure.","evidence":"X-ray crystallography, in vitro ubiquitination, site-directed mutagenesis","pmids":["16061177"],"confidence":"High","gaps":["Did not explain basal autoinhibition of full-length enzyme"]},{"year":2006,"claim":"Resolved the molecular basis of substrate specificity: the WW3 domain recognizes both the PY core and an extended PY-tail, an expanded recognition surface.","evidence":"NMR solution structure of WW3–Smad7 PY peptide complex with binding measurements","pmids":["16641086"],"confidence":"High","gaps":["Generalizability of PY-tail recognition to other substrates untested"]},{"year":2007,"claim":"Defined the autoinhibition mechanism: an intramolecular C2–HECT interaction near the catalytic cysteine blocks ubiquitin thioester formation and is antagonized by Smad7 binding.","evidence":"NMR, in vitro ubiquitination, domain deletion/mutagenesis, cell-based stability assays","pmids":["17719543"],"confidence":"High","gaps":["Full-length enzyme conformational dynamics not resolved structurally"]},{"year":2007,"claim":"Extended SMURF2 into neuronal polarity: it ubiquitinates inactive Rap1B for degradation, restricting it to the future axon, with mPar3/Kinesin-2 providing spatial targeting.","evidence":"Neuronal RNAi, in vivo ubiquitination, localization imaging, rescue; co-IP and dominant-negative interference","pmids":["17318188","17906294"],"confidence":"High","gaps":["mPar3–Kinesin-2 link is single-lab Medium-confidence","Mechanism of Rap1B activity-state selectivity unclear"]},{"year":2004,"claim":"Linked SMURF2 to senescence and aging: telomere attrition upregulates SMURF2, and its overexpression induces senescence via Rb/p53 through an activity distinct from canonical E3 ligase function.","evidence":"Retroviral overexpression, BrdU, SA-β-gal, E3-dead mutant controls","pmids":["15574587"],"confidence":"High","gaps":["The non-E3 senescence activity remains molecularly undefined","p21-independence mechanism unresolved"]},{"year":2008,"claim":"Established SMURF2 as a mitotic regulator: it localizes to centrosome/midbody/centromeres and enforces the spindle assembly checkpoint by stabilizing Mad2, with Cdc20-silencing epistasis confirming the SAC role.","evidence":"siRNA, immunofluorescence, flow cytometry, co-IP, nocodazole arrest, Cdc20 rescue","pmids":["18852296"],"confidence":"High","gaps":["Direct ubiquitination linkage on Mad2 vs indirect protection not fully separated"]},{"year":2008,"claim":"Showed SMURF2 controls its paralog: it degrades Smurf1 unidirectionally, and loss of this control enhances breast cancer migration and bone metastasis.","evidence":"Co-IP, in vivo ubiquitination, siRNA, migration/invasion, in vivo metastasis model","pmids":["18927080"],"confidence":"High","gaps":["Structural basis of unidirectional degradation not addressed"]},{"year":2010,"claim":"Connected SMURF2 to Wnt signaling: it ubiquitinates Axin at Lys505 to promote degradation, modulating β-catenin/Tcf activity.","evidence":"Co-IP, in vitro/in vivo ubiquitination, MS site mapping, shRNA, reporter, K505R mutant","pmids":["20858899"],"confidence":"High","gaps":["In vivo physiological role in Wnt signaling not established"]},{"year":2011,"claim":"Refined the Smad3 mechanism in vivo: SMURF2 multi-monoubiquitinates Smad3 to block complex formation rather than degrading it, with T179 phosphorylation enhancing the interaction.","evidence":"Smurf2 KO mice, primary cells, in vivo ubiquitination, site mapping, phospho-mutants","pmids":["22045334"],"confidence":"High","gaps":["Switch between mono- and poly-ubiquitination determinants unclear"]},{"year":2012,"claim":"Tied SMURF2 to chromatin and genome stability: it degrades RNF20, setting H2B-Ub/H3K4me3/H3K79me marks, co-localizes at DSBs, and its loss causes genomic instability and cancer susceptibility.","evidence":"Smurf2 KO mice, co-IP, IF co-localization, histone modification and DDR assays","pmids":["22231558","22552287"],"confidence":"High","gaps":["Direct chromatin recruitment mechanism at breaks not defined"]},{"year":2015,"claim":"Revealed adaptor competition and post-translational tuning: RNF11 competes with Smad7 to activate SMURF2 on endomembranes, while sumoylation (PIAS3/Ubc9), USP15 deubiquitination, and Akt phosphorylation set its activity and abundance.","evidence":"In vitro reconstitution and competition, co-IP, sumoylation/ubiquitination site mapping, reporter assays","pmids":["28292929","26679521","26435193","24961731"],"confidence":"High","gaps":["RNF11 finding is High; sumoylation/USP15/Akt are single-lab Medium","Integration of these modifications in vivo unresolved"]},{"year":2016,"claim":"Expanded the substrate and innate-immunity repertoire: SMURF2 degrades VISA/MAVS to dampen type I IFN signaling and targets YY1, Id1/3, EZH2, and others, broadening its regulatory scope.","evidence":"Co-IP, linkage-specific in vivo ubiquitination, catalytic mutants, KO/KD with functional readouts","pmids":["24729608","24121673","24803334","21933340","23526793"],"confidence":"High","gaps":["VISA/YY1 High-confidence; EZH2/Id1-3 single-lab Medium","Substrate selection rules across this set undefined"]},{"year":2020,"claim":"Defined a non-degradative stabilizing mode: SMURF2-UBCH5 polyubiquitinates mutant EGFR at four lysines to retain it at the membrane and block lysosomal sorting, protecting it from degradation.","evidence":"In vitro/in vivo ubiquitination, MS site mapping, superresolution imaging, acetyl-mimic mutant, siRNA","pmids":["32669362","21750651"],"confidence":"High","gaps":["Determinants distinguishing stabilizing vs degradative chains on a given substrate unclear"]},{"year":2022,"claim":"Linked SMURF2 activity to phosphorylation control and cancer stemness: Thr249 phosphorylation activates the ligase, and its loss stabilizes TGFBR1 to enhance glioma stem-cell tumorigenicity.","evidence":"T249A phospho-mutant, TGFBR1 stability and GSC sphere/tumor assays, knockdown rescue","pmids":["35017630"],"confidence":"Medium","gaps":["Upstream Thr249 kinase identity not established","Single-lab"]},{"year":2023,"claim":"Placed SMURF2 in ferroptosis defense: it degrades GSTP1, a GPX4/FSP1-independent lipid-peroxide detoxifier, making the SMURF2/GSTP1 axis a determinant of ferroptosis drug sensitivity.","evidence":"Proteomics, co-IP, in vivo ubiquitination, GSTP1 catalytic assays, in vitro/in vivo drug sensitivity","pmids":["38016474"],"confidence":"High","gaps":["Trigger that activates SMURF2 toward GSTP1 early in ferroptosis unclear"]},{"year":null,"claim":"How a single ligase chooses between degradative polyubiquitination, attenuating mono-ubiquitination, and outright substrate stabilization for its many clients—and how upstream signals coordinate this choice spatially—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model for chain-type/outcome selection across substrates","Spatial (nuclear vs cytoplasmic vs endomembrane) control of substrate choice incomplete","Non-E3 senescence activity remains molecularly undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,2,11,12,44,45]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,12,16,41,44]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,3,4,11,13]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,26,40,51]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,24,52]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,43,52]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[9]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,12,37,38]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[9,23,26]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[13]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[13,35]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[8,30,44]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[16,25]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,10]}],"complexes":["Smad7-SMURF2 E3 ligase complex","SMURF2-UBCH5 (UbcH5) E3:E2 complex"],"partners":["SMAD7","SMAD2","SMAD3","RNF11","USP15","PIAS3","DVL","EGFR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9HAU4","full_name":"E3 ubiquitin-protein ligase SMURF2","aliases":["HECT-type E3 ubiquitin transferase SMURF2","SMAD ubiquitination regulatory factor 2","SMAD-specific E3 ubiquitin-protein ligase 2"],"length_aa":748,"mass_kda":86.2,"function":"E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates (PubMed:11016919, PubMed:38016474). Interacts with SMAD7 to trigger SMAD7-mediated transforming growth factor beta/TGF-beta receptor ubiquitin-dependent degradation, thereby down-regulating TGF-beta signaling (PubMed:11163210, PubMed:12717440, PubMed:21791611). In addition, interaction with SMAD7 activates autocatalytic degradation, which is prevented by interaction with AIMP1 (PubMed:18448069). Also forms a stable complex with TGF-beta receptor-mediated phosphorylated SMAD1, SMAD2 and SMAD3, and targets SMAD1 and SMAD2 for ubiquitination and proteasome-mediated degradation (PubMed:11016919, PubMed:11158580, PubMed:11389444). SMAD2 may recruit substrates, such as SNON, for ubiquitin-dependent degradation (PubMed:11389444). Negatively regulates TGFB1-induced epithelial-mesenchymal transition and myofibroblast differentiation (PubMed:30696809). Acts as an activator of ferroptosis by mediating ubiquitination and degradation of GSTP1, thereby preventing detoxification of 4-hydroxynonenal (4-HNE) reactive aldehyde (PubMed:38016474) (Microbial infection) In case of filoviruses Ebola/EBOV and Marburg/MARV infection, the complex formed by viral matrix protein VP40 and SMURF2 facilitates virus budding","subcellular_location":"Nucleus; Cytoplasm; Cell membrane; Membrane raft","url":"https://www.uniprot.org/uniprotkb/Q9HAU4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SMURF2","classification":"Not Classified","n_dependent_lines":58,"n_total_lines":1208,"dependency_fraction":0.048013245033112585},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SMURF2","total_profiled":1310},"omim":[{"mim_id":"620552","title":"CUE DOMAIN-CONTAINING PROTEIN 1; CUEDC1","url":"https://www.omim.org/entry/620552"},{"mim_id":"612598","title":"RING FINGER PROTEIN 11; RNF11","url":"https://www.omim.org/entry/612598"},{"mim_id":"610667","title":"UBIQUITIN CARBOXYL-TERMINAL HYDROLASE L5; UCHL5","url":"https://www.omim.org/entry/610667"},{"mim_id":"607699","title":"RING FINGER PROTEIN 20; RNF20","url":"https://www.omim.org/entry/607699"},{"mim_id":"606247","title":"STAM-BINDING PROTEIN; STAMBP","url":"https://www.omim.org/entry/606247"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear speckles","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SMURF2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9HAU4","domains":[{"cath_id":"2.60.40.150","chopping":"12-140","consensus_level":"high","plddt":86.959,"start":12,"end":140},{"cath_id":"2.20.70.10","chopping":"162-189","consensus_level":"high","plddt":73.075,"start":162,"end":189},{"cath_id":"2.20.70.10","chopping":"256-338","consensus_level":"high","plddt":77.2083,"start":256,"end":338},{"cath_id":"3.90.1750.10","chopping":"366-628","consensus_level":"medium","plddt":87.2415,"start":366,"end":628},{"cath_id":"3.30.2410.10","chopping":"633-740","consensus_level":"high","plddt":89.1006,"start":633,"end":740}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAU4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAU4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAU4-F1-predicted_aligned_error_v6.png","plddt_mean":76.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SMURF2","jax_strain_url":"https://www.jax.org/strain/search?query=SMURF2"},"sequence":{"accession":"Q9HAU4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HAU4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HAU4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAU4"}},"corpus_meta":[{"pmid":"11163210","id":"PMC_11163210","title":"Smad7 binds to Smurf2 to form an E3 ubiquitin ligase that targets the TGF beta receptor for degradation.","date":"2000","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11163210","citation_count":1150,"is_preprint":false},{"pmid":"11158580","id":"PMC_11158580","title":"Regulation of Smad degradation and activity by Smurf2, an E3 ubiquitin ligase.","date":"2001","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/11158580","citation_count":427,"is_preprint":false},{"pmid":"11016919","id":"PMC_11016919","title":"Smurf2 is a ubiquitin E3 ligase mediating proteasome-dependent degradation of Smad2 in transforming growth factor-beta signaling.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11016919","citation_count":420,"is_preprint":false},{"pmid":"11389444","id":"PMC_11389444","title":"TGF-beta induces assembly of a Smad2-Smurf2 ubiquitin ligase complex that targets SnoN for degradation.","date":"2001","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/11389444","citation_count":269,"is_preprint":false},{"pmid":"16373342","id":"PMC_16373342","title":"Tumor necrosis factor promotes Runx2 degradation through up-regulation of Smurf1 and Smurf2 in osteoblasts.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16373342","citation_count":265,"is_preprint":false},{"pmid":"17719543","id":"PMC_17719543","title":"Autoinhibition of the HECT-type ubiquitin ligase Smurf2 through its C2 domain.","date":"2007","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/17719543","citation_count":233,"is_preprint":false},{"pmid":"16061177","id":"PMC_16061177","title":"Regulation of Smurf2 ubiquitin ligase activity by anchoring the E2 to the HECT domain.","date":"2005","source":"Molecular 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therapy","url":"https://pubmed.ncbi.nlm.nih.gov/34545207","citation_count":17,"is_preprint":false},{"pmid":"36611161","id":"PMC_36611161","title":"The miR-15b-Smurf2-HSP27 axis promotes pulmonary fibrosis.","date":"2023","source":"Journal of biomedical science","url":"https://pubmed.ncbi.nlm.nih.gov/36611161","citation_count":16,"is_preprint":false},{"pmid":"32103168","id":"PMC_32103168","title":"SMURF2 prevents detrimental changes to chromatin, protecting human dermal fibroblasts from chromosomal instability and tumorigenesis.","date":"2020","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/32103168","citation_count":16,"is_preprint":false},{"pmid":"27730540","id":"PMC_27730540","title":"Downregulation of Smurf2 ubiquitin ligase in pancreatic cancer cells reversed TGF-β-induced tumor formation.","date":"2016","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27730540","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52827,"output_tokens":13248,"usd":0.1786,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":24563,"output_tokens":5797,"usd":0.13387,"stage2_stop_reason":"end_turn"},"total_usd":0.31247,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"Smurf2 is a C2-WW-HECT domain E3 ubiquitin ligase that constitutively associates with Smad7; this Smad7-Smurf2 complex is exported from the nucleus and recruited to the activated TGFβ receptor, where it targets both the receptor and Smad7 for degradation via proteasomal and lysosomal pathways. Smad7 functions as an adaptor in this E3 ligase complex.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, receptor degradation assays, dominant-negative and RNAi expression studies\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, functional rescue experiments, multiple orthogonal methods, foundational paper replicated by multiple labs\",\n      \"pmids\": [\"11163210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Smurf2 selectively interacts with receptor-regulated Smads (Smad1, Smad2, Smad3 but not Smad4) and preferentially targets Smad1 and Smad2 for ubiquitination and proteasome-mediated degradation; HECT catalytic activity is required. Smurf2 shows higher binding affinity to activated (phosphorylated) Smad2 upon TGF-β stimulation.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assays, in vivo ubiquitination assays, proteasome inhibitor experiments, Xenopus embryo overexpression\",\n      \"journal\": \"The Journal of biological chemistry / Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — independently replicated in two labs (PMID 11016919 and 11158580) with in vitro assays and mutagenesis\",\n      \"pmids\": [\"11016919\", \"11158580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"TGF-β stimulation induces assembly of a Smad2-Smurf2 ubiquitin ligase complex via interaction of the Smad2 proline-rich PPXY motif with WW domains of Smurf2; this complex associates with the transcriptional co-repressor SnoN and targets it for ubiquitin-mediated proteasomal degradation.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, proteasome inhibitor experiments, domain mapping\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination, domain mutant studies, high-impact replicated finding\",\n      \"pmids\": [\"11389444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The N-terminal domain (NTD) of Smad7 stimulates Smurf2 ubiquitin ligase activity by recruiting the E2 enzyme UbcH7 to the HECT domain. A 2.1 Å crystal structure of the Smurf2 HECT domain revealed a suboptimal E2 binding pocket; mutagenesis to optimize this pocket generated a constitutively active HECT domain that inhibits TGFβ signaling independently of Smad7.\",\n      \"method\": \"X-ray crystallography (2.1 Å), in vitro ubiquitination assays, site-directed mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure combined with functional mutagenesis and in vitro reconstitution\",\n      \"pmids\": [\"16061177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"An intramolecular interaction between the C2 and HECT domains of Smurf2 autoinhibits its ubiquitin ligase activity by binding near the catalytic cysteine and interfering with ubiquitin thioester formation; Smad7 binding to the HECT domain antagonizes this inhibitory C2-HECT interaction to activate Smurf2.\",\n      \"method\": \"NMR spectroscopy, in vitro ubiquitination assays, domain deletion/mutagenesis, cell-based stability assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structural analysis plus in vitro reconstitution and mutagenesis in a single rigorous study\",\n      \"pmids\": [\"17719543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"NMR solution structure of the Smurf2 WW3 domain in complex with the Smad7 PY motif peptide revealed that WW3 (which has Phe instead of the canonical Trp) binds both the core PY motif and six C-terminal residues (PY-tail), defining an expanded WW domain recognition surface that provides substrate specificity.\",\n      \"method\": \"NMR spectroscopy (solution structure determination), binding affinity measurements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR solution structure with functional validation of binding interface\",\n      \"pmids\": [\"16641086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Smurf2 ubiquitinates inactive Rap1B and initiates its proteasomal degradation in hippocampal neurons; this restricts Rap1B to the tip of a single neurite (the future axon), establishing neuronal polarity. Smurf1 and Smurf2 have distinct roles: Smurf1 regulates Rho/neurite growth and Smurf2 regulates Rap1B/polarity.\",\n      \"method\": \"RNAi knockdown in neurons, in vivo ubiquitination assay, fluorescence imaging of Rap1B localization, rescue experiments\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with defined substrate and phenotype, localization imaging, ubiquitination assay\",\n      \"pmids\": [\"17318188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"mPar3 links Smurf2 to Kinesin-2 and is required to localize Smurf2 to neuronal growth cones; disruption of mPar3–Kinesin-2 or mPar3–Smurf2 interactions prevents restriction of Rap1B to the axon and abolishes neuronal polarity.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, dominant-negative interference, fluorescence localization in neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and RNAi with phenotypic readout, single lab\",\n      \"pmids\": [\"17906294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Smurf2 up-regulation is a specific consequence of telomere attrition in human fibroblasts, and ectopic Smurf2 expression at physiological levels is sufficient to induce senescence. The senescence-inducing function requires a novel activity distinct from Smurf2's E3 ligase activity, and involves recruitment of the Rb and p53 pathways; p21 is elevated but Smurf2-induced senescence is p21-independent.\",\n      \"method\": \"Retroviral overexpression, BrdU incorporation, senescence-associated β-galactosidase staining, gene expression analysis, E3-dead mutant rescue\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods demonstrating gain-of-function phenotype, E3-inactive mutant controls\",\n      \"pmids\": [\"15574587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Smurf2 localizes to the centrosome, mitotic midbody, and centromeres. Smurf2 depletion causes misaligned/lagging chromosomes, premature anaphase, and defective cytokinesis. Smurf2 is required for the spindle assembly checkpoint (SAC): its inactivation leads to enhanced polyubiquitination and degradation of Mad2, mislocalizing Mad2 and preventing prometaphase arrest; silencing Cdc20 in Smurf2-depleted cells rescues cyclin B and securin accumulation.\",\n      \"method\": \"siRNA knockdown, immunofluorescence localization, flow cytometry, co-immunoprecipitation, nocodazole arrest assays, epistasis (Cdc20 silencing rescue)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization, loss-of-function phenotype, substrate (Mad2) identification, genetic epistasis with Cdc20\",\n      \"pmids\": [\"18852296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Smurf2 mediates ubiquitin-dependent degradation of Smurf1; Smurf2 interacts with Smurf1 and induces its ubiquitination and proteasomal degradation, whereas Smurf1 does not reciprocally degrade Smurf2. Knockdown of Smurf2 in breast cancer cells increases Smurf1 protein and enhances cell migration and bone metastasis.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA knockdown, migration/invasion assays, in vivo bone metastasis model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vivo ubiquitination, functional phenotype in vitro and in vivo\",\n      \"pmids\": [\"18927080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Smurf2 is an E3 ubiquitin ligase for Axin; it interacts with Axin, promotes its ubiquitination specifically at Lys505 (identified by mass spectrometry), and targets it for proteasomal degradation. Knockdown of endogenous Smurf2 increases endogenous Axin levels and reduces β-catenin/Tcf reporter activity.\",\n      \"method\": \"Co-immunoprecipitation, in vitro/in vivo ubiquitination assay, mass spectrometry, shRNA knockdown, luciferase reporter assay, K505R mutant resistance experiment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro ubiquitination, MS-identified ubiquitination site, site-directed mutagenesis resistance, endogenous knockdown phenotype\",\n      \"pmids\": [\"20858899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In vivo (Smurf2 knockout mice), Smurf2 induces multiple mono-ubiquitination of Smad3 at MH2 domain lysine residues rather than polyubiquitination/degradation; this mono-ubiquitination inhibits Smad3 complex formation and attenuates TGF-β signaling. Phosphorylation of Smad3 at T179 enhances Smurf2-Smad3 interaction and Smad3 ubiquitination.\",\n      \"method\": \"Smurf2 knockout mouse generation, primary MEF/dermal fibroblast assays, in vivo ubiquitination assays, site mapping, phosphorylation-deficient mutant studies\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic KO model with primary cells, in vivo ubiquitination with site mapping and phospho-mutant validation\",\n      \"pmids\": [\"22045334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Smurf2 targets RNF20 for proteasomal degradation, thereby regulating monoubiquitination of histone H2B and trimethylation of H3K4 and H3K79. Smurf2 and RNF20 co-localize at γ-H2AX foci of double-strand DNA breaks. Smurf2 knockout mice show dysregulated DNA damage response, genomic instability, and increased cancer susceptibility.\",\n      \"method\": \"Smurf2 knockout mouse model, co-immunoprecipitation, immunofluorescence co-localization, histone modification assays, proteasome inhibitor experiments\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse, co-IP, co-localization, multiple substrates and phenotypes across mouse and human cells\",\n      \"pmids\": [\"22231558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Smurf2 mediates ubiquitination and degradation of Id1 and Id3 in senescent cells; Smurf2-mediated ubiquitination of Id1 (and its consequent degradation) is the mechanism by which Smurf2 up-regulates p16 expression during senescence.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA knockdown, p16 reporter assays\",\n      \"journal\": \"Aging cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"21933340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Smurf2 is the E3 ubiquitin ligase responsible for polyubiquitination and proteasomal degradation of EZH2 in human mesenchymal stem cells, which is required for neuron differentiation; EZH2 degradation by Smurf2 enables PPARγ expression to drive differentiation.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA/shRNA knockdown, ChIP-on-chip, gene microarray, in vivo stroke model\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, KD with phenotype, single lab\",\n      \"pmids\": [\"23526793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Smurf2 interacts with VISA/MAVS and targets it for K48-linked polyubiquitination and proteasomal degradation, negatively regulating virus-triggered type I IFN signaling. The E3 ligase activity of Smurf2 (C716A mutant is inactive) is required for this negative regulation.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay (K48-linkage specific), Smurf2 KO/KD experiments, IFN-β reporter assays, C716A catalytic mutant\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, linkage-specific ubiquitination, catalytic mutant, KO and KD with functional readout\",\n      \"pmids\": [\"24729608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Smurf2 mediates ubiquitination and degradation of YY1; Smurf2 interacts with YY1 via the PPxY motif of YY1, induces its polyubiquitination, and shortens YY1 half-life, thereby reducing YY1-mediated transcriptional activation. In B-cell lymphoma context, Smurf2 deficiency enhances YY1-mediated transactivation of c-Myc.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, half-life measurement, PPxY mutant analysis, Smurf2 KO mouse model, luciferase reporter assay\",\n      \"journal\": \"Nature communications / Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple labs (PMIDs 24121673 and 24803334), reciprocal Co-IP, ubiquitination assay with domain mapping\",\n      \"pmids\": [\"24121673\", \"24803334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Smurf2 forms an active E3:E2 complex with UBCH5 that maintains KRAS protein stability by mediating K48-linked monoubiquitination of UBCH5 at K144. This SMURF2:UBCH5 complex promotes degradation of β-TrCP1, an E3 ligase that itself degrades KRAS; loss of SMURF2 accumulates β-TrCP1 leading to KRAS degradation.\",\n      \"method\": \"siRNA/shRNA knockdown, overexpression rescue, in vivo ubiquitination assay, protein half-life measurements, domain mutagenesis (P residues in UBCH5)\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis with domain mutants, in vivo ubiquitination, single lab\",\n      \"pmids\": [\"24709419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Akt phosphorylates Smurf2 and promotes ubiquitin/proteasome-mediated degradation of Smurf2 itself, thereby increasing Runx2 protein stability and transcriptional activity. This establishes an Akt→Smurf2→Runx2 axis regulating osteoblast differentiation.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation assays, ubiquitination assays, Western blot, overexpression/knockdown experiments\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, phosphorylation and ubiquitination assays, single lab\",\n      \"pmids\": [\"24961731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Smurf2 is sumoylated by the SUMO E2 enzyme Ubc9 and SUMO E3 ligase PIAS3 at Lys26 and Lys369; sumoylation enhances Smurf2's ability to degrade the TGFβ receptor and suppresses TGFβ-induced EMT. PIAS3 associates with Smurf2 and promotes its sumoylation.\",\n      \"method\": \"Co-immunoprecipitation, sumoylation assays, site-directed mutagenesis (K26R/K369R), 3D organoid EMT assay, siRNA knockdown\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, site-specific sumoylation mapping with mutants, functional 3D organoid assay, single lab\",\n      \"pmids\": [\"26679521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP15 deubiquitinates SMURF2 at Lys734 (a residue required for catalytic activity), thereby enhancing SMURF2's E3 ligase activity and increasing TGFβ receptor stability and downstream signaling. USP15 and SMURF2 form a regulatory axis within the TGFβ pathway.\",\n      \"method\": \"Co-immunoprecipitation, proteomic/mass spectrometry analysis of ubiquitination sites, in vivo ubiquitination assays, TGFβ pathway reporter assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, MS-identified ubiquitination site, functional assays, single lab\",\n      \"pmids\": [\"26435193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Ectopically expressed Smurf2 in chondrocytes interacts with GSK-3β, induces its ubiquitination and proteasomal degradation, and thereby upregulates β-catenin levels, activating articular chondrocyte maturation.\",\n      \"method\": \"Immunoprecipitation, ubiquitination assay, Col2a1-Smurf2 transgenic mouse ex vivo chondrocytes, Western blot\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay in transgenic primary cells, single lab\",\n      \"pmids\": [\"19481076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Smurf2 physically associates with NEDD9/HEF1 and is required for NEDD9 protein stability by protecting it from polyubiquitination and proteasomal degradation; Smurf2 depletion reduces NEDD9 levels, prevents Aurora A activation at the G2/M boundary, and causes mitotic entry delay.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, Aurora A kinase activity assays, flow cytometry\",\n      \"journal\": \"Cell division\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, kinase activity readout, single lab\",\n      \"pmids\": [\"20825672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"AIMP2/p38, upon TGF-β-induced phosphorylation at S156 and nuclear translocation, binds Smurf2 in the nucleus to enhance ubiquitination of FBP (FUBP1). AIMP2 also inhibits nuclear export of Smurf2 to sustain TGFβ tumor-suppressive signaling. An oncogenic AIMP2 mutation abrogates this nuclear interaction with Smurf2.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assays, subcellular fractionation, domain mutagenesis, in vivo tumor formation assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, subcellular localization experiments, single lab\",\n      \"pmids\": [\"27197155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TRAF4 recruits SMURF2 to the IL-25 receptor complex; TRAF4-SMURF2 mediates degradation of DAZAP2 (an IL-25R inhibitory molecule), enabling ACT1 recruitment to IL-25R and IL-25 signaling. This is a critical initiating event for IL-25-driven type 2 allergic responses.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, Traf4 knockout mouse model, IL-25 signaling assays, siRNA knockdown\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, KO mouse with functional readout, single lab\",\n      \"pmids\": [\"25681341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Smurf2 physically interacts with Topoisomerase IIα (Topo IIα), modifies its ubiquitination status to protect it from proteasomal degradation (stabilizing rather than degrading), and is a physiologic regulator of Topo IIα levels. Smurf2-depleted cells cannot resolve DNA catenanes and form pathological chromatin bridges during mitosis.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown, chromosomal bridge quantification, Topo IIα rescue experiments\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, KD with rescue, single lab\",\n      \"pmids\": [\"28611047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SMURF2 regulates RANKL expression in osteoblasts by disrupting the interaction between SMAD3 and the vitamin D receptor through altering SMAD3 ubiquitination; Smurf2-deficient mice exhibit severe osteoporosis with increased osteoclast numbers driven by osteoblast-elevated RANKL. Osteoblast-selective Smurf2 deletion recapitulates the full osteoporosis phenotype.\",\n      \"method\": \"Conditional/germline knockout mouse model, co-immunoprecipitation, ubiquitination assays, RANKL expression analysis, osteoclast number quantification\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with cell-type-specific deletion, mechanistic co-IP and ubiquitination, clear cellular phenotype\",\n      \"pmids\": [\"28216630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RNF11 directly competes with SMAD7 for binding to SMURF2 in a mutually exclusive, proline-rich domain-dependent manner; when RNF11 sequesters SMURF2 on endomembranes, it activates SMURF2 E3 ligase activity while reducing SMURF2 auto-ubiquitination, antagonizing the SMAD7-mediated downregulation of TGFβ signaling.\",\n      \"method\": \"In vitro reconstitution of SMURF2·RNF11 complex, in vitro binding competition assays, co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown with TGFβ gene reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstitution, binding competition, co-IP, functional downstream readouts in one study\",\n      \"pmids\": [\"28292929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Smurf2 directly binds, ubiquitinates, and promotes autophagic-lysosomal degradation (not solely proteasomal) of lamin A and progerin in a dose- and E3 ligase-dependent manner. Acute Smurf2 overexpression in progeria fibroblasts significantly reduces nuclear deformability.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assays, autophagy/lysosome inhibitor experiments, Smurf2 overexpression/depletion, nuclear morphology quantification in progeria cells\",\n      \"journal\": \"Aging cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination with pathway specificity, functional rescue in disease model, single lab\",\n      \"pmids\": [\"29405587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Smurf2 deficiency in mice impairs senescence of primary MEFs (reduced p16) and increases susceptibility to spontaneous B-cell lymphoma; premalignant spleens show defective senescence responses, genetically linking Smurf2-mediated senescence regulation to tumor suppression in vivo.\",\n      \"method\": \"Smurf2 knockout mouse generation, primary MEF senescence assays, tumor incidence monitoring, immunohistochemistry\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO model with in vivo tumor phenotype and primary cell mechanistic data\",\n      \"pmids\": [\"22552287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SMURF2 interacts with ChREBP and promotes its ubiquitination and proteasomal degradation; loss of SMURF2 increases ChREBP, enhances aerobic glycolysis, and promotes colorectal cancer cell proliferation. AKT acts as an upstream suppressor of SMURF2 to protect ChREBP from degradation.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, siRNA/overexpression experiments, glycolysis/oxygen consumption measurements, in vivo xenograft\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, functional metabolic readouts, single lab\",\n      \"pmids\": [\"31409643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SMURF2 interacts with SATB1 and promotes its ubiquitination and degradation; SMURF2 is itself negatively regulated by the deubiquitinase USP47, establishing a USP47-SMURF2-SATB1 axis controlling colon cancer cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, mouse xenograft model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab\",\n      \"pmids\": [\"30742943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TRAF4 acts as an E3 ubiquitin ligase that mediates K48-linked ubiquitination of Smurf2 at the K119 site, promoting Smurf2 proteasomal degradation, thereby increasing BMP/TGF-β signaling and osteogenic differentiation of mesenchymal stem cells.\",\n      \"method\": \"Co-immunoprecipitation, in vitro/in vivo ubiquitination assays, K119 site-directed mutagenesis, osteogenic differentiation assays, in vivo bone formation model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, in vitro ubiquitination with site-directed mutant, in vivo model, single lab\",\n      \"pmids\": [\"31076633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Nedd8 targets Smurf2 for neddylation, which promotes Smurf2 degradation; Smurf2 itself exerts Nedd8 ligase activity, and Smurf1 neddylation activates its ubiquitin ligase activity.\",\n      \"method\": \"In vivo neddylation assays, co-immunoprecipitation, Western blot stability assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method (neddylation assay), limited mechanistic detail in abstract\",\n      \"pmids\": [\"27086113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PRMT5 sustains RNF168 expression; loss of PRMT5 (in MTAP-deficient glioblastoma) reduces RNF168, allowing SMURF2 to destabilize H2AX. RNF168 and SMURF2 act as stabilizer and destabilizer of H2AX respectively via dynamic interactions with H2AX, defining a PRMT5-RNF168-SMURF2 cascade controlling H2AX proteostasis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, genetic KD experiments, DNA damage response assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, genetic epistasis, single lab\",\n      \"pmids\": [\"31533041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SMURF2 interacts with SIRT1 and mediates its ubiquitination and proteasomal degradation; depletion of SMURF2 leads to SIRT1 upregulation and promotes colorectal cancer tumor formation and growth in vitro and in vivo.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, in vivo tumor xenograft\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab\",\n      \"pmids\": [\"32361710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Dishevelled (DVL), a key Wnt pathway transducer, activates Smurf2 E3 ligase activity and is itself a substrate of Smurf2; DVL deficiency phenocopies Smurf2 absence, leading to increased R-Smad phosphorylation. Smurf2 also ubiquitinates Prickle1 (Wnt/PCP component). Both SMAD7 and DVL activate Smurf2 through a common mechanism.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assays, DVL triple-knockout HEK293 cells, R-Smad phosphorylation assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, genetic KO cell line, single lab\",\n      \"pmids\": [\"32392721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Smurf2 negatively regulates BMP/Smad1/5 signaling by inducing ubiquitination of Smad1/5; Smurf2-deficient mice show enhanced BMP2-induced ectopic bone formation with greater bone mass and osteoblast numbers.\",\n      \"method\": \"Smurf2 knockout mouse, ectopic bone formation assay with rhBMP2, in vivo ubiquitination assay, primary bone marrow stromal cell differentiation assays\",\n      \"journal\": \"Bone research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO model, in vivo ubiquitination, bone formation phenotype, single lab\",\n      \"pmids\": [\"33298874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Smurf2 interacts with TRAF2 (identified by yeast two-hybrid), and TRAF2 overexpression triggers Smurf2 ubiquitination and formation of a TNF-R2/Smurf2 complex; Smurf2 in turn promotes TNF-R2 ubiquitination and relocalization to a detergent-insoluble fraction, which is associated with enhanced TNF-R2-induced JNK activation without affecting NF-κB.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, ubiquitination assays, detergent fractionation, JNK/NF-κB signaling assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — yeast two-hybrid plus single co-IP, limited mechanistic follow-up, single lab\",\n      \"pmids\": [\"18671942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SMURF2 interacts with EGFR and promotes its ubiquitination (non-degradative/stabilizing), protecting EGFR from c-Cbl-mediated degradation. SMURF2 knockdown destabilizes EGFR, triggers autophagy, and reduces clonogenic survival of EGFR-expressing cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assays, siRNA knockdown, autophagic response assays, in vivo tumor model\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, in vivo model, single lab; replicated in follow-up study PMID 32669362\",\n      \"pmids\": [\"21750651\", \"32669362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SMURF2-UBCH5 E3-E2 complex mediates polyubiquitination of L858R/T790M EGFR at four specific lysine residues, stabilizing mutant EGFR by membrane retention and competing with acetylation-driven receptor internalization to lysosomes; SMURF2 knockdown increases lysosomal sorting of EGFR.\",\n      \"method\": \"In vitro and in vivo ubiquitination assays, mass spectrometry (ubiquitination site mapping), superresolution microscopy, acetylation-mimicking mutant (K→Q), siRNA knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro ubiquitination, MS site identification, mutagenesis, superresolution imaging, multiple orthogonal methods\",\n      \"pmids\": [\"32669362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SMURF2 phosphorylation at Thr249 activates its E3 ubiquitin ligase activity; inactivation of this phosphorylation site (T249A mutant) increases TGF-β receptor (TGFBR1) protein stability, augments glioma stem cell (GSC) stemness and tumorigenicity, phenocopying SMURF2 silencing.\",\n      \"method\": \"Phospho-specific mutant (T249A) overexpression, TGFBR1 stability assays, GSC sphere and tumor formation assays, TGFBR1 knockdown rescue experiments\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-mutant functional analysis, substrate stability assay, genetic rescue, single lab\",\n      \"pmids\": [\"35017630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FMO2 binds CYP2J3 and disrupts CYP2J3 interaction with SMURF2 in the cytosol, leading to increased cytoplasm-to-nucleus translocation of SMURF2 and consequent inhibition of SMAD2/3 signaling and cardiac fibrosis; this antifibrotic mechanism is independent of FMO2 enzymatic activity.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, CRISPR KO rats, gain-of-function lentivirus experiments, SMAD2/3 phosphorylation assays, cardiac fibrosis histology\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, genetic KO model, subcellular fractionation, multiple species validation, single lab\",\n      \"pmids\": [\"35861735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SMURF2 ubiquitinates and promotes degradation of GSTP1 at early stages of ferroptosis; GSTP1 functions as a GPX4- and FSP1-independent ferroptosis defense by catalyzing GSH conjugation of 4-HNE and detoxifying lipid hydroperoxides. Genetic or pharmacological modulation of the SMURF2/GSTP1 axis sensitizes tumors to ferroptosis-inducing drugs.\",\n      \"method\": \"Proteomics (dynamics during ferroptosis), co-immunoprecipitation, in vivo ubiquitination assay, GSTP1 catalytic activity assays, genetic overexpression/KD, in vitro and in vivo drug sensitivity assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — proteomic discovery plus co-IP, ubiquitination assay, catalytic enzyme assay, in vivo validation, multiple methods\",\n      \"pmids\": [\"38016474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SMURF2 acts as a bona fide E3 ligase for RACK1, adding K6, K33, and K48 ubiquitin chains to RACK1, resulting in its polyubiquitination and degradation. PCAF-mediated acetylation of RACK1 at K130 inhibits SMURF2-mediated RACK1 ubiquitination, stabilizing RACK1 and promoting ovarian cancer progression.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay (linkage-specific), acetylation assay, PCAF overexpression, in vivo tumor model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, linkage-specific ubiquitination, acetylation crosstalk experiment, single lab\",\n      \"pmids\": [\"37828084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TGF-β induces SIK1 expression via Smad-dependent transcription; SIK1 forms complexes with the TGFβ type I receptor and Smurf2, and both SIK1 kinase activity and Smurf2 ubiquitin ligase activity are required for proper TGFβ type I receptor turnover. Knockdown of SIK1 and Smurf2 enhances physiological TGFβ-induced epithelial growth arrest.\",\n      \"method\": \"Co-immunoprecipitation, kinase and ubiquitination assays, siRNA knockdown, receptor turnover assays, promoter mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, functional enzymatic assays, double-KD epistasis, single lab\",\n      \"pmids\": [\"22378783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RNF11 recruits AMSH to Smurf2 for ubiquitination and degradation by the 26S proteasome; RNF11 binds AMSH independently of its RING-finger domain and PY motif, and AMSH ubiquitination requires both RNF11 and Smurf2.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, in vivo ubiquitination assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, limited mechanistic follow-up\",\n      \"pmids\": [\"14755250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SMURF2 acts as an E3 ligase to mediate ubiquitination and degradation of RhoA; the oncoprotein AAMP stabilizes RhoA by binding to it and suppressing SMURF2-mediated RhoA ubiquitination and degradation, thereby promoting colorectal cancer cell migration and invasion.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, cell migration/invasion assays\",\n      \"journal\": \"Molecular therapy oncolytics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, limited mechanistic depth\",\n      \"pmids\": [\"34901393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SMURF2 interacts with and promotes ubiquitination and degradation of PARP1; this interaction is enhanced under oxidative stress, and Smurf2-mediated PARP1 degradation reduces ROS and protects endothelial cells from apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, in vivo ubiquitination assay, ROS/apoptosis assays in HUVECs\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, single study\",\n      \"pmids\": [\"32167680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Smurf2 interacts with PDE4B and facilitates its degradation, thereby activating the cAMP-PKA-CREB signaling pathway, which transcriptionally upregulates miR-132 to suppress CTGF expression and attenuate liver fibrosis.\",\n      \"method\": \"Co-immunoprecipitation, Smurf2 transgenic mouse model, miRNA array, western blot, CREB signaling assays\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP and transgenic model, indirect mechanism through miRNA, single lab\",\n      \"pmids\": [\"29100790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SMURF2 interacts with CNKSR2 and promotes its stabilization (protective ubiquitination against proteasomal degradation); Smurf2 knockdown decreases CNKSR2 and reduces PI3K-PTEN-AKT-FoxO3a-driven proliferation of breast cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, surface plasmon resonance, indirect immunofluorescence, ubiquitination assays, siRNA knockdown, proliferation assays\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus SPR binding validation and ubiquitination assay, multiple orthogonal binding methods, single lab\",\n      \"pmids\": [\"29534682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In normal cells and tissues, SMURF2 has a predominantly nuclear localization; in prostate and aggressive breast carcinomas, SMURF2 shows significantly increased cytoplasmic sequestration associated with disease progression. Biochemical studies showed SMURF2 is more stable in the cytoplasmic compartment, and 14-3-3 proteins are SMURF2 interactors that may affect its localization.\",\n      \"method\": \"Subcellular fractionation, immunohistochemistry of 666 tissue samples, co-immunoprecipitation (interactome), nuclear export inhibitor experiments\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — subcellular fractionation with large tissue cohort and co-IP interactome, single lab\",\n      \"pmids\": [\"31003445\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SMURF2 is a HECT-domain E3 ubiquitin ligase whose activity is autoinhibited by an intramolecular C2–HECT interaction (relieved by Smad7 or Dishevelled binding) and modulated by phosphorylation (Thr249), sumoylation (K26/K369 by PIAS3), neddylation, and deubiquitination (by USP15 at K734); it forms substrate-recruiting complexes through its WW domains (recognizing PPxY motifs) and targets a broad array of proteins for ubiquitin-mediated degradation or stabilization, including TGFβ receptors (via Smad7 adaptor), Smad2/3 (mono- or poly-ubiquitination to attenuate signaling), Smad1/5 (BMP pathway), SnoN, RNF20, EZH2, YY1, Id1/3, Mad2, Axin, GSK-3β, GSTP1, VISA/MAVS, RACK1, lamin A/progerin, Topo IIα, EGFR, NEDD9, Smurf1, and others, while also protecting certain substrates (NEDD9, EGFR, CNKSR2, Topo IIα) from degradation; through these diverse substrate interactions SMURF2 regulates TGFβ/BMP signaling, neuronal polarity (via Rap1B ubiquitination localized by mPar3/Kinesin-2), the spindle assembly checkpoint (via Mad2 stabilization), telomere-dependent senescence, chromatin/epigenetic landscape (via RNF20/H2B-Ub/H3K4me3), DNA damage response, and ferroptosis resistance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SMURF2 is a C2-WW-HECT domain E3 ubiquitin ligase that governs the strength and duration of TGF\\u03b2/BMP signaling and a broad program of cell-cycle, chromatin, and stress-response events through substrate-specific ubiquitination [#0, #1]. Its catalytic activity is held in check by an intramolecular C2\\u2013HECT interaction that occludes the catalytic cysteine and blocks ubiquitin-thioester formation; this autoinhibition is relieved when adaptor proteins such as Smad7\\u2014and, by a shared mechanism, Dishevelled\\u2014bind the HECT domain, while the Smad7 N-terminal domain further stimulates activity by recruiting the E2 UbcH7 into a suboptimal E2-binding pocket [#3, #4, #37]. Substrate selection is achieved through its WW domains, which read PPxY/PY motifs via an expanded recognition surface that engages both the core PY motif and a C-terminal tail [#5, #17]. In the TGF\\u03b2 axis, the Smad7-SMURF2 complex is exported to the activated receptor and degrades both receptor and Smad7 [#0], SMURF2 ubiquitinates R-Smads (degradative for Smad1/2, multi-monoubiquitination of Smad3 that blocks complex formation) [#1, #12], and clears the co-repressor SnoN [#2]; it also restrains BMP-driven Smad1/5 signaling [#38]. Beyond this core pathway, SMURF2 controls mitotic fidelity by stabilizing Mad2 to enforce the spindle assembly checkpoint and by protecting Topoisomerase II\\u03b1 to allow catenane resolution [#9, #26], and it shapes the chromatin and DNA-damage landscape by degrading RNF20 to set H2B-ubiquitination/H3K4-H3K79 methylation marks at double-strand breaks [#13]. SMURF2 drives telomere-attrition-triggered senescence\\u2014a function genetically linked to tumor suppression in knockout mice that develop B-cell lymphoma [#8, #30]\\u2014and acts as a ferroptosis modulator by degrading the lipid-peroxide defense enzyme GSTP1 [#44]. Its own abundance and activity are tuned by phosphorylation (Akt-driven degradation; Thr249-dependent activation), sumoylation by PIAS3/Ubc9 at K26/K369, USP15-mediated deubiquitination at K734, and competitive adaptor exchange between Smad7 and RNF11 [#19, #42, #20, #21, #28]. Notably, SMURF2 acts as a stabilizer as well as a degrader for a subset of clients (EGFR, NEDD9, Topo II\\u03b1, CNKSR2), often via non-degradative ubiquitination [#40, #23, #26, #51].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established SMURF2's foundational role: how is TGF\\u03b2 receptor signaling terminated? It works as a HECT E3 that, via the Smad7 adaptor, targets the activated receptor for degradation, and it directly degrades receptor-regulated Smads.\",\n      \"evidence\": \"Co-IP, subcellular fractionation, receptor degradation and ubiquitination assays; yeast two-hybrid and Xenopus overexpression\",\n      \"pmids\": [\"11163210\", \"11016919\", \"11158580\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how SMURF2 catalytic activity is regulated\", \"Smad4 selectivity rationale unaddressed at structural level\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined SMURF2 substrate-recruitment logic: TGF\\u03b2 induces a Smad2-SMURF2 complex via Smad2 PPxY\\u2013WW interaction that degrades the co-repressor SnoN, extending SMURF2's reach to transcriptional regulators.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitination, proteasome inhibition, domain mapping\",\n      \"pmids\": [\"11389444\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"WW-domain structural basis of PY recognition not yet defined\", \"In vivo relevance unaddressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Explained how the Smad7 adaptor activates SMURF2 catalysis: the Smad7 NTD recruits UbcH7 to a suboptimal E2 pocket in the HECT domain, defined by a 2.1 \\u00c5 crystal structure.\",\n      \"evidence\": \"X-ray crystallography, in vitro ubiquitination, site-directed mutagenesis\",\n      \"pmids\": [\"16061177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain basal autoinhibition of full-length enzyme\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved the molecular basis of substrate specificity: the WW3 domain recognizes both the PY core and an extended PY-tail, an expanded recognition surface.\",\n      \"evidence\": \"NMR solution structure of WW3\\u2013Smad7 PY peptide complex with binding measurements\",\n      \"pmids\": [\"16641086\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generalizability of PY-tail recognition to other substrates untested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the autoinhibition mechanism: an intramolecular C2\\u2013HECT interaction near the catalytic cysteine blocks ubiquitin thioester formation and is antagonized by Smad7 binding.\",\n      \"evidence\": \"NMR, in vitro ubiquitination, domain deletion/mutagenesis, cell-based stability assays\",\n      \"pmids\": [\"17719543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length enzyme conformational dynamics not resolved structurally\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extended SMURF2 into neuronal polarity: it ubiquitinates inactive Rap1B for degradation, restricting it to the future axon, with mPar3/Kinesin-2 providing spatial targeting.\",\n      \"evidence\": \"Neuronal RNAi, in vivo ubiquitination, localization imaging, rescue; co-IP and dominant-negative interference\",\n      \"pmids\": [\"17318188\", \"17906294\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"mPar3\\u2013Kinesin-2 link is single-lab Medium-confidence\", \"Mechanism of Rap1B activity-state selectivity unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Linked SMURF2 to senescence and aging: telomere attrition upregulates SMURF2, and its overexpression induces senescence via Rb/p53 through an activity distinct from canonical E3 ligase function.\",\n      \"evidence\": \"Retroviral overexpression, BrdU, SA-\\u03b2-gal, E3-dead mutant controls\",\n      \"pmids\": [\"15574587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The non-E3 senescence activity remains molecularly undefined\", \"p21-independence mechanism unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established SMURF2 as a mitotic regulator: it localizes to centrosome/midbody/centromeres and enforces the spindle assembly checkpoint by stabilizing Mad2, with Cdc20-silencing epistasis confirming the SAC role.\",\n      \"evidence\": \"siRNA, immunofluorescence, flow cytometry, co-IP, nocodazole arrest, Cdc20 rescue\",\n      \"pmids\": [\"18852296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ubiquitination linkage on Mad2 vs indirect protection not fully separated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed SMURF2 controls its paralog: it degrades Smurf1 unidirectionally, and loss of this control enhances breast cancer migration and bone metastasis.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitination, siRNA, migration/invasion, in vivo metastasis model\",\n      \"pmids\": [\"18927080\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of unidirectional degradation not addressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected SMURF2 to Wnt signaling: it ubiquitinates Axin at Lys505 to promote degradation, modulating \\u03b2-catenin/Tcf activity.\",\n      \"evidence\": \"Co-IP, in vitro/in vivo ubiquitination, MS site mapping, shRNA, reporter, K505R mutant\",\n      \"pmids\": [\"20858899\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological role in Wnt signaling not established\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Refined the Smad3 mechanism in vivo: SMURF2 multi-monoubiquitinates Smad3 to block complex formation rather than degrading it, with T179 phosphorylation enhancing the interaction.\",\n      \"evidence\": \"Smurf2 KO mice, primary cells, in vivo ubiquitination, site mapping, phospho-mutants\",\n      \"pmids\": [\"22045334\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Switch between mono- and poly-ubiquitination determinants unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Tied SMURF2 to chromatin and genome stability: it degrades RNF20, setting H2B-Ub/H3K4me3/H3K79me marks, co-localizes at DSBs, and its loss causes genomic instability and cancer susceptibility.\",\n      \"evidence\": \"Smurf2 KO mice, co-IP, IF co-localization, histone modification and DDR assays\",\n      \"pmids\": [\"22231558\", \"22552287\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct chromatin recruitment mechanism at breaks not defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed adaptor competition and post-translational tuning: RNF11 competes with Smad7 to activate SMURF2 on endomembranes, while sumoylation (PIAS3/Ubc9), USP15 deubiquitination, and Akt phosphorylation set its activity and abundance.\",\n      \"evidence\": \"In vitro reconstitution and competition, co-IP, sumoylation/ubiquitination site mapping, reporter assays\",\n      \"pmids\": [\"28292929\", \"26679521\", \"26435193\", \"24961731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RNF11 finding is High; sumoylation/USP15/Akt are single-lab Medium\", \"Integration of these modifications in vivo unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Expanded the substrate and innate-immunity repertoire: SMURF2 degrades VISA/MAVS to dampen type I IFN signaling and targets YY1, Id1/3, EZH2, and others, broadening its regulatory scope.\",\n      \"evidence\": \"Co-IP, linkage-specific in vivo ubiquitination, catalytic mutants, KO/KD with functional readouts\",\n      \"pmids\": [\"24729608\", \"24121673\", \"24803334\", \"21933340\", \"23526793\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"VISA/YY1 High-confidence; EZH2/Id1-3 single-lab Medium\", \"Substrate selection rules across this set undefined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined a non-degradative stabilizing mode: SMURF2-UBCH5 polyubiquitinates mutant EGFR at four lysines to retain it at the membrane and block lysosomal sorting, protecting it from degradation.\",\n      \"evidence\": \"In vitro/in vivo ubiquitination, MS site mapping, superresolution imaging, acetyl-mimic mutant, siRNA\",\n      \"pmids\": [\"32669362\", \"21750651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants distinguishing stabilizing vs degradative chains on a given substrate unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked SMURF2 activity to phosphorylation control and cancer stemness: Thr249 phosphorylation activates the ligase, and its loss stabilizes TGFBR1 to enhance glioma stem-cell tumorigenicity.\",\n      \"evidence\": \"T249A phospho-mutant, TGFBR1 stability and GSC sphere/tumor assays, knockdown rescue\",\n      \"pmids\": [\"35017630\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream Thr249 kinase identity not established\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed SMURF2 in ferroptosis defense: it degrades GSTP1, a GPX4/FSP1-independent lipid-peroxide detoxifier, making the SMURF2/GSTP1 axis a determinant of ferroptosis drug sensitivity.\",\n      \"evidence\": \"Proteomics, co-IP, in vivo ubiquitination, GSTP1 catalytic assays, in vitro/in vivo drug sensitivity\",\n      \"pmids\": [\"38016474\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger that activates SMURF2 toward GSTP1 early in ferroptosis unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single ligase chooses between degradative polyubiquitination, attenuating mono-ubiquitination, and outright substrate stabilization for its many clients\\u2014and how upstream signals coordinate this choice spatially\\u2014remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model for chain-type/outcome selection across substrates\", \"Spatial (nuclear vs cytoplasmic vs endomembrane) control of substrate choice incomplete\", \"Non-E3 senescence activity remains molecularly undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 11, 12, 44, 45]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 12, 16, 41, 44]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 3, 4, 11, 13]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 26, 40, 51]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 24, 52]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 43, 52]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 12, 37, 38]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [9, 23, 26]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [13, 35]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [8, 30, 44]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [16, 25]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"complexes\": [\n      \"Smad7-SMURF2 E3 ligase complex\",\n      \"SMURF2-UBCH5 (UbcH5) E3:E2 complex\"\n    ],\n    \"partners\": [\n      \"SMAD7\",\n      \"SMAD2\",\n      \"SMAD3\",\n      \"RNF11\",\n      \"USP15\",\n      \"PIAS3\",\n      \"DVL\",\n      \"EGFR\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}