{"gene":"USP2","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2006,"finding":"Crystal structure of the human USP2 catalytic domain in complex with ubiquitin revealed that ubiquitin uses two major interaction sites simultaneously for binding to USP2, and a layer of ordered water molecules mediates key interactions between ubiquitin and USP2, suggesting a general mechanism of water-mediated ubiquitin recognition by USPs.","method":"X-ray crystallography, ubiquitin mutant inhibition assays, peptide inhibition assays","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and inhibition assays in a single rigorous study","pmids":["16905103"],"is_preprint":false},{"year":1997,"finding":"Chick UBP41 (USP2 ortholog) is a ubiquitin-specific protease (cysteine protease) with isopeptidase activity; it cleaves ubiquitin from the C-terminus of natural and engineered ubiquitin fusions regardless of size, releases free ubiquitin from di-ubiquitin, and converts poly-ubiquitinated lysozyme conjugates to mono-ubiquitinated forms without further degradation, suggesting a role in ubiquitin recycling. The enzyme is inhibited by ubiquitin-aldehyde and sulfhydryl-blocking agents.","method":"In vitro enzyme assay with purified recombinant protein, 125I-labeled ubiquitin substrates, ubiquitin-β-galactosidase fusion substrates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified enzyme and multiple substrates, active-site inhibitor validation","pmids":["9325273"],"is_preprint":false},{"year":2003,"finding":"Mouse Usp2-69 isoform can form a homo-complex and a hetero-complex with Usp2-45. Both isoforms localize to the cytoplasm when overexpressed in COS-7 and NIH3T3 cells.","method":"Co-immunoprecipitation, overexpression in COS-7 and NIH3T3 cells, immunohistochemistry","journal":"Gene expression","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP and immunolocalization, single lab, two orthogonal methods","pmids":["14686789"],"is_preprint":false},{"year":2003,"finding":"Overexpression of UBP41 (USP2) is sufficient to induce apoptosis in human cells; an enzymatically defective UBP41 mutant did not induce cell death, demonstrating that the proapoptotic activity requires catalytic activity. Overexpression caused broad deubiquitination but did not stabilize known proteasome substrates p21 or p27, and did not arrest cells in G2/M.","method":"Overexpression of wild-type and catalytic mutant UBP41, apoptosis assays, flow cytometry, Western blot","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — catalytic mutant controls establish requirement for enzymatic activity; single lab","pmids":["12566314"],"is_preprint":false},{"year":2011,"finding":"USP2 deubiquitinates and stabilizes truncated AIF (tAIF), promoting AIF-mediated caspase-independent cell death. CHIP ubiquitin E3 ligase antagonizes this by ubiquitinating and destabilizing tAIF. Knockdown of USP2 attenuated MNNG-induced cell death.","method":"Co-immunoprecipitation, siRNA knockdown, overexpression, Western blot for tAIF ubiquitination and stability, cell death assays","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal functional experiments with KD and OE plus Co-IP; single lab","pmids":["21293491"],"is_preprint":false},{"year":2011,"finding":"USP2 is required for TNF-α-induced NF-κB signaling; siRNA knockdown of USP2 prevented IκB phosphorylation, nuclear translocation of NF-κB, expression of NF-κB target genes, and IL-8 secretion. Isoform-specific functions were identified.","method":"Targeted siRNA screen, Western blot for IκB phosphorylation and NF-κB translocation, IL-8 ELISA","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional siRNA screen with multiple mechanistic readouts; single lab","pmids":["21480224"],"is_preprint":false},{"year":2011,"finding":"USP2 coimmunoprecipitates with clock proteins and directly interacts with PER1, deubiquitinating PER1 without altering its stability. Usp2 knockout mice display a longer free-running circadian period and altered clock gene expression.","method":"Co-immunoprecipitation, Usp2 knockout mouse model, locomotor rhythm recording, in vitro deubiquitination assay, Western blot","journal":"Biology open","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse phenotype plus Co-IP plus in vitro deubiquitination, multiple orthogonal methods replicated across two USP2 circadian papers","pmids":["23213472"],"is_preprint":false},{"year":2011,"finding":"USP2b is in a complex with BMAL1 and regulates its stability and turnover, altering expression of CLOCK/BMAL1-controlled genes; USP2 knockout increases phase delays in response to low irradiance light.","method":"Co-immunoprecipitation, USP2 knockout mouse model, luciferase reporter, Western blot","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with KO phenotype; single lab","pmids":["21966515"],"is_preprint":false},{"year":2011,"finding":"USP2-45 physically interacts with ENaC subunits (via the α-ENaC cytoplasmic N-terminal domain) and with the HECT domain of Nedd4-2 (by both its catalytic domain and N-terminal tail), promoting ENaC deubiquitylation and increased surface expression. The Usp2-69 isoform, which lacks the specific N-terminal domain, is inactive toward ENaC. The catalytic core alone has reduced activity toward ENaC in oocytes despite retaining full activity toward ubiquitin-AMC.","method":"Co-immunoprecipitation in HEK293 cells, GST pull-down of purified recombinant proteins, Xenopus laevis oocyte electrophysiology","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reconstitution with purified proteins (GST pull-down) plus Co-IP plus functional electrophysiology, isoform-specific controls","pmids":["21478478"],"is_preprint":false},{"year":2011,"finding":"USP2-45 and USP2-69 both counteract Nedd4-2-mediated downregulation of KCNQ1/KCNE1 channels by deubiquitylating KCNQ1, restoring surface expression and membrane localization. USP2 binds KCNQ1 independently of the PY motif.","method":"Electrophysiology in Xenopus oocytes and mammalian cells, co-immunoprecipitation, Western blot for ubiquitin and surface KCNQ1, immunocytochemistry","journal":"Heart rhythm","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, biochemistry, imaging); replicated for two USP2 isoforms","pmids":["22024150"],"is_preprint":false},{"year":2011,"finding":"USP2 contributes to active site catalysis through a conserved Asn271 that directly stabilizes the oxyanion in the acylation step, structurally supported by absolutely conserved Asp575. Asn574, positioned as the putative third catalytic triad member, does not fulfill this role functionally. Asp575 has a dual role in oxyanion hole formation and maintaining His557 alignment.","method":"Site-directed mutagenesis, in vitro hydrolysis assays (ubiquitin-AMC, K48-linked diubiquitin), mass spectrometry-based assay, molecular dynamics simulation","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis with multiple substrates and computational validation in a single rigorous study","pmids":["21542621"],"is_preprint":false},{"year":2012,"finding":"Stopped-flow kinetics revealed that monoubiquitin binds USP2 in a simple one-step process, while K48-linked diubiquitin shows biphasic binding, indicating a conformational rearrangement of the diubiquitin substrate during USP2 catalysis.","method":"Stopped-flow fluorescence kinetics, single-turnover deubiquitination assays with Ub-AMC and K48-linked IQF-diubiquitin, inactive USP2 mutant binding studies","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro transient kinetics with inactive mutant controls and global fitting; single rigorous study","pmids":["23211065"],"is_preprint":false},{"year":2014,"finding":"USP2-45 binds the α2δ-1 accessory subunit (but not Cav1.2 or β2 subunits) of voltage-gated calcium channels and promotes deubiquitylation of both Cav1.2 and α2δ-1 subunits, reducing Cav1.2 current amplitude and surface expression. Co-expression of α2δ-1 is required for the effect of USP2-45.","method":"Whole-cell current recordings, surface biotinylation assays, co-immunoprecipitation in tsA-201 and HEK-293 cells","journal":"Pflugers Archiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology plus biochemistry with required accessory subunit controls; single lab","pmids":["25366495"],"is_preprint":false},{"year":2015,"finding":"USP2 (both USP2-69 and USP2-45 isoforms) interacts with the E3-ubiquitin ligase IDOL and promotes its deubiquitylation, stabilizing IDOL protein. Paradoxically, in a tri-partite USP2-IDOL-LDLR complex, USP2 also deubiquitylates the LDLR and prevents its IDOL-mediated lysosomal degradation, thereby increasing LDL uptake.","method":"Genetic screening, co-immunoprecipitation, Western blot for protein stability, LDL uptake assay","journal":"Circulation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional LDL uptake assay; single lab, multiple isoforms tested","pmids":["26666640"],"is_preprint":false},{"year":2015,"finding":"USP2-45 binds MR (mineralocorticoid receptor) and, similarly to aldosterone, promotes removal of MR monoubiquitylation, disrupts MR/TSG101 association, and destabilizes MR protein, constituting a negative feedback loop limiting aldosterone-induced responses.","method":"Co-immunoprecipitation, Western blot for MR ubiquitylation and stability, luciferase reporter for MR transcriptional activity","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus reporter assay; single lab, two orthogonal methods","pmids":["23548632"],"is_preprint":false},{"year":2016,"finding":"USP2-45 functions as a circadian clock output effector regulating calcium absorption. In the small intestine, USP2-45 is found in membrane fractions, negatively regulates NHERF4 protein abundance in a rhythmic manner, and interacts in vitro with NHERF4 and endogenous Clathrin Heavy Chain. Usp2 knockout mice show hyperabsorption of dietary Ca2+ associated with strong NHERF4 overexpression and TRPV6 upregulation.","method":"Usp2 knockout mouse model, subcellular fractionation, in vitro interaction assay (Co-IP), dietary calcium measurement, Drosophila dUsp2 knockdown rescue with dietary Ca2+","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse phenotype plus in vitro interaction and fractionation; single lab, two orthogonal methods","pmids":["26756164"],"is_preprint":false},{"year":2016,"finding":"USP2 inhibitor ML364 (IC50 1.1 µM) induces cyclin D1 degradation and cell cycle arrest in colorectal cancer and mantle cell lymphoma cells, and decreases homologous recombination-mediated DNA repair. Direct binding of ML364 to USP2 was demonstrated.","method":"Fluorescent di-ubiquitin biochemical assay, microscale thermophoresis, Western blot, flow cytometry, HR repair assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical inhibitor assay plus direct binding measurement plus multiple cellular readouts; single rigorous study with orthogonal methods","pmids":["27681596"],"is_preprint":false},{"year":2017,"finding":"Residues Ub4K, Ub12E, Ub14E, and Ub72A serve as the molecular determinants enabling USP2 to distinguish between ubiquitin and NEDD8. Combining NEDD8 residues at positions 4, 12, 14, and 72 to match ubiquitin makes NEDD8 accessible for hydrolysis by USP2. USP2 binds the N-terminus of ubiquitin to form a stable interaction before engaging the C-terminus for substrate specificity.","method":"Ubiquitin/NEDD8 mutagenesis, in vitro hydrolysis assays","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic mutagenesis with in vitro functional validation; single lab","pmids":["28536428"],"is_preprint":false},{"year":2018,"finding":"6-Thioguanine inhibits USP2 through a noncompetitive and slow-binding mechanism. X-ray crystallographic data confirmed the binding mode.","method":"Enzyme kinetics, X-ray crystallography","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with kinetic characterization; single lab","pmids":["29449607"],"is_preprint":false},{"year":2019,"finding":"USP2 promotes Twist protein stabilization by removing β-TrCP-mediated ubiquitination of Twist, maintaining cancer stem cell populations in TNBC through Twist-mediated EMT and Bmi1 activation.","method":"Co-immunoprecipitation, ubiquitination assay, genetic and pharmacological USP2 inhibition, Western blot, in vivo xenograft","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiments; single lab","pmids":["30918246"],"is_preprint":false},{"year":2020,"finding":"USP2 associates with internalized ErbB2 at endosomes and prevents its lysosomal sorting and degradation by exerting deubiquitylase activity, safeguarding ErbB2 surface levels against ubiquitylation-mediated endocytic degradation.","method":"Co-immunoprecipitation, Western blot for ErbB2 ubiquitylation, endocytic trafficking assays, USP2 inhibitor ML364","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus functional endocytic assay; single lab","pmids":["32327714"],"is_preprint":false},{"year":2021,"finding":"USP2 is a deubiquitylase of SKP2, binding via the leucine-rich repeat substrate-binding domain on SKP2 to deubiquitylate and stabilize SKP2 protein. USP2-stabilized SKP2 does not destabilize its substrates p21 and p27 because USP2 binding to SKP2 disrupts the SKP2-substrate interaction.","method":"DUB panel screening by Co-IP with endogenous SKP2, siRNA knockdown, small-molecule inhibition, CHX chase assay, ubiquitination assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — endogenous Co-IP, ubiquitination assay, domain interaction mapping; single lab","pmids":["34425107"],"is_preprint":false},{"year":2022,"finding":"USP2 stabilizes E2F4 protein through physical interaction and deubiquitination, promoting E2F4-driven transcription of ATG2A and ULK2, resulting in autophagic degradation of metallothionein proteins and altered zinc homeostasis in cancer cells.","method":"Co-immunoprecipitation, deubiquitination assay, BiFC, gain/loss-of-function studies, ChIP, rescue experiments","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus deubiquitination assay plus multiple orthogonal functional methods; single lab","pmids":["35253629"],"is_preprint":false},{"year":2022,"finding":"USP2 interacts with SMAD7 and stabilizes it by cleaving Lys27- and Lys48-linked poly-ubiquitin chains. Lys27-linked poly-ubiquitin chains at SMAD7 K185 mediate SMAD7 recruitment to HERC3, which in turn regulates Lys63-linked polyubiquitination of SMAD7. Loss of USP2 induces TGF-β signaling and glioblastoma progression.","method":"Co-immunoprecipitation, in vitro deubiquitination assay distinguishing linkage types, USP2 knockout/overexpression, in vivo GBM model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination analysis; single lab","pmids":["35332268"],"is_preprint":false},{"year":2022,"finding":"USP2 deubiquitinates NBS1, stabilizing the MRE11-RAD50-NBS1 complex at DNA double-strand break (DSB) sites. USP2 is recruited to DSB sites in an ATM-dependent manner, and phosphorylation of two critical N-terminal residues of USP2 by ATM is required for recruitment and interaction with RECQL4. Loss of both USP2 and USP28 causes premature MRN disassembly from DSBs, defects in ATM activation, and impaired homologous recombination repair.","method":"DUB screen, co-immunoprecipitation, chromatin fractionation at DSBs, ATM kinase inhibition, siRNA double knockdown, HR repair assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional DUB screen plus Co-IP plus mechanistic epistasis; single lab","pmids":["36436562"],"is_preprint":false},{"year":2023,"finding":"USP2 directly interacts with PD-L1 and deconjugates K48-linked polyubiquitination at lysine 270 of PD-L1, stabilizing PD-L1. Key residues Thr288, Arg292, and Asp293 of USP2 control its binding to PD-L1. USP2 depletion causes ER-associated degradation of PD-L1.","method":"sgRNA screening, co-immunoprecipitation, ubiquitination assay (K48-specific), site-directed mutagenesis, Western blot, in vivo tumor models with immune profiling","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — sgRNA screen plus Co-IP plus linkage-specific ubiquitination assay plus mutagenesis plus in vivo validation; multiple orthogonal methods in single study","pmids":["37670038"],"is_preprint":false},{"year":2023,"finding":"USP2 deubiquitinates and stabilizes VPRBP, a potent repressor of p53. The USP2-VPRBP axis controls both p53 and PD-L1 expression, and USP2 knockout in mice does not affect normal tissues (unlike MDM2 inhibition).","method":"Co-immunoprecipitation, Western blot for VPRBP ubiquitination, USP2 knockout mice, genetic and pharmacological inhibition combined with anti-PD1","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo KO characterization; single lab","pmids":["37024504"],"is_preprint":false},{"year":2023,"finding":"USP2 directly interacts with CD47 and stabilizes it through deubiquitination. USP2 inhibition destabilizes CD47, enhancing macrophage phagocytosis of tumor cells.","method":"Co-immunoprecipitation, ubiquitination assay, in vitro deubiquitination, phagocytosis assay, in vivo tumor models, single-cell RNA sequencing","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus deubiquitination assay plus functional phagocytosis assay; single lab","pmids":["40379682"],"is_preprint":false},{"year":2023,"finding":"USP2 interacts with survivin and stabilizes it; pharmacological inhibition of USP2 by ML364 increases survivin ubiquitination and degradation, sensitizing cancer cells to TRAIL-induced apoptosis.","method":"Co-immunoprecipitation, ubiquitination assay, Western blot, cell death assay with survivin overexpression rescue","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiment; single lab","pmids":["37628997"],"is_preprint":false},{"year":2023,"finding":"USP2 deubiquitinates ACE2, serving as its physiological deubiquitinase; targeted inhibition with ML364 leads to marked and reversible reduction in ACE2 protein abundance, blocking ACE2-dependent coronavirus infection in vitro and in vivo.","method":"USP2 inhibitor ML364, Co-immunoprecipitation, Western blot for ACE2 ubiquitination, viral infection assays, human ACE2 transgenic mouse models","journal":"Science translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo mouse model; single lab","pmids":["38055802"],"is_preprint":false},{"year":2024,"finding":"USP2 stably binds NCOA4 and suppresses its degradation by removing K48-linked ubiquitin chains from NCOA4, thereby enabling ferritinophagy and ferroptosis in esophageal squamous cell carcinoma cells.","method":"Co-immunoprecipitation, ubiquitination assay (K48-specific), USP2 KO in ESCC model, in vitro and in vivo ferroptosis assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination assay plus in vivo model; single lab","pmids":["38744953"],"is_preprint":false},{"year":2024,"finding":"VCP recruits USP2 to FASN, and USP2 removes K48-linked ubiquitin chains from FASN to stabilize it; VCP domain 2 and a specific USP2 amino acid sequence are critical for their interaction. This stabilization promotes autophagy in osteosarcoma.","method":"Co-IP/MS, ubiquitination assay, molecular docking, protein truncation mapping, gain/loss-of-function experiments","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS plus domain mapping plus ubiquitination assay; single lab","pmids":["39489738"],"is_preprint":false},{"year":2024,"finding":"USP2 deubiquitinates and stabilizes EZH2 by directly binding to it and reducing its ubiquitination; USP2-stabilized EZH2 promotes H3K27me3 enrichment and epigenetic silencing of SOX1 in bladder cancer.","method":"Co-immunoprecipitation, ubiquitination assay, CHX chase, ChIP assay, in vivo xenograft","journal":"Translational oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus ChIP; single lab","pmids":["39197387"],"is_preprint":false},{"year":2024,"finding":"USP2 deubiquitinates and stabilizes MFN2 in cardiomyocytes, counteracting Angiotensin II-induced calcium overload and mitochondrial dysfunction. Rescue experiments confirmed that MFN2 downregulation abolishes the protective role of USP2.","method":"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, in vitro and in vivo cardiac hypertrophy models","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiments; single lab","pmids":["37100191"],"is_preprint":false},{"year":2024,"finding":"USP2 deubiquitinates and stabilizes KRAS in multiple myeloma cells. Gambogic acid forms a covalent bond with USP2 Cys284 through an allosteric pocket, inhibiting USP2 deubiquitinating activity and causing KRAS degradation.","method":"Co-immunoprecipitation, ubiquitination assay, covalent binding characterization, USP2 knockdown/overexpression, in vitro and in vivo proliferation assays","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus covalent inhibitor characterization plus functional validation; single lab","pmids":["39807309"],"is_preprint":false},{"year":2025,"finding":"USP2 directly interacts with PPAR-γ and deubiquitinates it by removing K48-linked ubiquitin chains at lysine 161, stabilizing PPAR-γ protein and enhancing its transcriptional activity to promote hepatic lipid accumulation in MASLD.","method":"Co-immunoprecipitation, K48-specific ubiquitination assay, site-specific mutagenesis, KO mice, in vivo siRNA targeting, Western blot","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — site-specific ubiquitination mapping plus mutagenesis plus Co-IP plus KO mouse model with multiple orthogonal methods","pmids":["40993213"],"is_preprint":false},{"year":2025,"finding":"USP2 directly interacts with PPAR-γ and deubiquitinates it to stabilize protein levels, enhancing insulin signaling and muscle mass maintenance. MYOD1 activates USP2 transcription by binding to the USP2 promoter region. Loss of PPAR-γ abolishes the regulatory effects of USP2 on insulin sensitivity and muscle atrophy.","method":"Co-immunoprecipitation, ubiquitination assay, USP2 knockout mouse models (global and muscle-specific), promoter binding assay, AAV-Usp2 injection","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus tissue-specific KO; single lab","pmids":["39874418"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates TXNDC5 (stabilizing TGFβR1 to activate TGF-β signaling) and the transferrin receptor TFRC (enhancing ferroptosis). TGF-β1 activates USP2 by lactylation at Lys447, while SIRT2 delactylates USP2 at Lys447 to suppress its activity.","method":"Co-immunoprecipitation, ubiquitination assay, lactylation mapping, SIRT2 delactylation assay, tissue-specific KO mice, organ fibrosis models, ML364 treatment","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple substrate Co-IP and ubiquitination assays plus novel PTM (lactylation) identification; single lab","pmids":["41310079"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates and stabilizes p300 histone acetyltransferase in hepatic stellate cells, promoting fibrogenic responses and HSC activation.","method":"DUB inhibitor screen in activated HSCs, co-immunoprecipitation, Western blot for p300 stability, USP2 knockdown/pharmacological inhibition","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional screen plus Co-IP plus pharmacological validation; single lab","pmids":["41703985"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates PML-RARα, including its drug-resistant mutants, stabilizing the fusion protein. USP2 inhibition or silencing reduces PML-RARα protein in an ATRA-sensitive and ATRA-resistant manner, reversed by proteasome inhibition.","method":"Co-immunoprecipitation, ubiquitination assay, proteasome inhibition rescue, USP2 overexpression/knockdown, ML364 treatment, apoptosis assay","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus proteasome rescue; single lab","pmids":["41445506"],"is_preprint":false},{"year":2025,"finding":"USP2 interacts with and deubiquitinates EBF2 in brown adipose tissue, stabilizing EBF2 protein and mediating thermogenic gene expression (including UCP1). BAT-specific Usp2 knockdown or systemic USP2 inhibition impairs thermogenic programs; Usp2 overexpression in BAT protects against high-fat diet-induced obesity.","method":"Quantitative proteomics, co-immunoprecipitation, immunofluorescence, adeno-associated virus-mediated Usp2 manipulation, seahorse metabolic analysis, electron microscopy","journal":"Molecular metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteome-wide substrate screen plus Co-IP plus in vivo mouse models; single lab","pmids":["40189098"],"is_preprint":false},{"year":2025,"finding":"SPOP E3 ubiquitin ligase ubiquitinates USP2, leading to its degradation and decreased CD47 protein abundance. USP2 deubiquitinates CD47 and protects it from proteasome-mediated degradation, confirming the SPOP/USP2/CD47 regulatory axis.","method":"Co-immunoprecipitation, in vitro deubiquitination assay, ubiquitination assay, cell fractionation, flow cytometry, phagocytosis assay, syngeneic tumor models","journal":"Journal for immunotherapy of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus in vitro deubiquitination assay plus functional phagocytosis and in vivo data; single lab","pmids":["41534899"],"is_preprint":false},{"year":2025,"finding":"USP2 attenuates TRAF6 K63-linked polyubiquitination in intestinal epithelial cells, dampening NF-κB activation and myosin light chain phosphorylation to preserve tight junction integrity. Colonic-specific USP2 overexpression in mice ameliorated DSS-induced barrier damage.","method":"Co-immunoprecipitation, K63-specific ubiquitination assay, Western blot for NF-κB/MLCK/MLC phosphorylation, in vivo colitis model with colonic USP2 overexpression","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination plus in vivo model; single lab","pmids":["40540897"],"is_preprint":false},{"year":2025,"finding":"USP2 directly interacts with FOXC1 and deubiquitinates it, stabilizing FOXC1 protein and protecting neuronal cells from MPP+-induced injury.","method":"Co-immunoprecipitation, Western blot for ubiquitination/stability, overexpression rescue, cell viability and apoptosis assays","journal":"Brain research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP plus ubiquitination assay; single lab, single study","pmids":["40355038"],"is_preprint":false},{"year":2025,"finding":"USP2 stabilizes LEF1 protein by mediating LEF1 deubiquitination, promoting osteogenic differentiation of bone marrow mesenchymal stem cells. Increased USP2 expression reduced bone loss in ovariectomy mouse model.","method":"Co-immunoprecipitation, protein stability assay, USP2/LEF1 knockdown, in vivo OVX mouse model","journal":"Journal of orthopaedic surgery and research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus stability assay; single lab, single study","pmids":["40301985"],"is_preprint":false},{"year":2025,"finding":"In the suprachiasmatic nucleus (SCN), USP2 modulates photic entrainment of the circadian clock by regulating light-induced Per1 expression and MAPK/ERK pathway activation. SCN-specific Usp2 KO recapitulates the light entrainment phenotype of full-body KO, while retinal Usp2 KO does not.","method":"Conditional Usp2 knockout (SCN-specific and retina-specific), running wheel recordings, in vivo light induction of Per1 and p-ERK in SCN","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific KO with molecular pathway readouts; single lab","pmids":["39967311"],"is_preprint":false},{"year":2021,"finding":"USP2 interacts with TRAF2 and removes its ubiquitination chains, stabilizing TRAF2 protein in fibroblast-like synoviocytes and promoting NF-κB-related inflammation in rheumatoid arthritis.","method":"Co-immunoprecipitation, ubiquitination assay, Western blot, in vivo CIA rat model","journal":"Biochemical genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus ubiquitination assay; single lab, single study","pmids":["38480669"],"is_preprint":false},{"year":2015,"finding":"Peroxisomal import of USP2 is mediated by PEX5 (PTS1 receptor) recognizing a C-terminal PTS1 signal; this import reduces USP2 proapoptotic activity by spatially separating it from cytosolic and nuclear interaction partners. All four USP2 isoforms are post-translationally imported into peroxisomes.","method":"Overexpression of USP2 isoforms with modified PTS1, apoptosis assays, PEX5 knockdown/overexpression, live-cell imaging (FRAP)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — subcellular localization directly linked to functional consequence (apoptosis) with PEX5-dependent import validation","pmids":["26484888"],"is_preprint":false},{"year":2024,"finding":"DCAF7 recruits USP2 to suppress clockophagy (selective autophagic degradation of BMAL1) by reducing BMAL1 K63-linked polyubiquitination, thereby inhibiting ferroptosis through the HIF1α-SLC7A11 axis in hepatocellular carcinoma.","method":"Co-immunoprecipitation, K63-specific ubiquitination assay, genetic ablation of DCAF7/USP2, in vitro and in vivo HCC models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination assay plus functional in vivo data; single lab","pmids":["40877242"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates and stabilizes JUP (junction plakoglobin), blocking Akt/β-catenin pathway activation to protect against cardiac hypertrophy. Mycn transcriptionally activates USP2 expression by binding to the USP2 promoter.","method":"Co-immunoprecipitation, ubiquitination assay, luciferase promoter assay, gain/loss-of-function in ISO-induced cardiac hypertrophy models","journal":"BMC cardiovascular disorders","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus ubiquitination assay plus promoter assay; single lab, single study","pmids":["38297207"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates and stabilizes TRAF2 in nasopharyngeal carcinoma, promoting NF-κB signaling, and directly binds MMP2 to reduce K48-linked polyubiquitination, extending MMP2 protein half-life.","method":"Co-immunoprecipitation, ubiquitination assay (K48-specific), CHX chase assay, NF-κB inhibition rescue","journal":"Molecular carcinogenesis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus ubiquitination assay; single lab, single study","pmids":["41144793"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates and stabilizes PPARγ by removing K48-linked chains at the K142 site, promoting fatty acid biosynthesis in hepatocellular carcinoma and oleic acid-mediated M2 macrophage polarization, which creates an IL-10/STAT3/USP2 positive-feedback loop.","method":"Co-immunoprecipitation, CUT&RUN, ELISA, mass spectrometry, K48-specific ubiquitination assay, in vitro co-culture system, patient-derived organoids","journal":"Journal for immunotherapy of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus site-specific ubiquitination mapping plus CUT&RUN plus MS; single lab","pmids":["41193183"],"is_preprint":false},{"year":2024,"finding":"USP2 reduces Keap1 deubiquitination (stabilizing Keap1), leading to Nrf2 inactivation, impaired iron metabolism, and lipid peroxidation, thereby promoting ferroptosis in macrophages and driving atherosclerosis. USP2 knockout macrophages show elevated Keap1 ubiquitination.","method":"USP2 knockout macrophages, ubiquitination assay for Keap1, ferroptosis assays, in vivo atherosclerosis model (apoE-/- mice), USP2 KO mice","journal":"British journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO macrophages plus ubiquitination assay plus in vivo model; single lab","pmids":["39228119"],"is_preprint":false},{"year":2021,"finding":"USP2 deubiquitinates and stabilizes antithrombin by counteracting Cullin 2-RBX1-mediated ubiquitination and degradation. USP2 overexpression inhibits antithrombin ubiquitination, while USP2 knockdown or pharmacological inhibition downregulates antithrombin.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression, proteasome inhibition, neddylation inhibition","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus multiple functional perturbations; single lab","pmids":["34324733"],"is_preprint":false},{"year":2021,"finding":"USP2 deubiquitinates and stabilizes TJP1/TWIST1 in bladder cancer; TJP1 acts as a scaffold recruiting USP2 to TWIST1, protecting TWIST1 from proteasomal degradation and promoting CCL2-driven angiogenesis.","method":"Co-immunoprecipitation, ubiquitination assay, TJP1/USP2 interaction mapping, in vitro and in vivo rescue experiments","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo data; single lab","pmids":["34782718"],"is_preprint":false},{"year":2025,"finding":"USP2 deubiquitinates and stabilizes p53 at the K305R site, removing ubiquitin to modulate cisplatin resistance through ferroptosis in NSCLC. USP2 overexpression increases nuclear p53 and promotes ferroptosis markers while reducing GPX4 and SLC7A11.","method":"Co-immunoprecipitation, ubiquitination assay (site-specific K305R), Western blot, in vivo xenograft","journal":"BMC medical genomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP plus site-specific ubiquitination assay; single lab, single study","pmids":["40011884"],"is_preprint":false}],"current_model":"USP2 is a multifunctional cysteine deubiquitinase whose catalytic triad (Cys-His-Asn/Asp) cleaves ubiquitin isopeptide bonds from a structurally defined interface requiring simultaneous engagement of two ubiquitin surfaces; it stabilizes a broad array of substrates—including cyclin D1, MDM2/VPRBP (regulating p53), FASN, ErbB2, PD-L1, CD47, SKP2, TWIST, SMAD7, NBS1, MFN2, PPARγ, EBF2, ACE2, PML-RARα, and ion channel regulators (ENaC, KCNQ1, Cav1.2)—by removing K48-linked polyubiquitin chains and preventing proteasomal or lysosomal degradation; it also deubiquitinates K63-linked chains on BMAL1 and TRAF6 to modulate circadian clock function and NF-κB signaling, respectively; isoform-specific N-terminal domains (USP2-45 vs. USP2-69) determine substrate selectivity (e.g., ENaC deubiquitylation requires the USP2-45 N-terminal tail that positions the enzyme via Nedd4-2 binding); USP2 itself is regulated by ATM-mediated phosphorylation at DSBs, by SPOP-mediated ubiquitination targeting it for degradation, and by TGFβ1-driven lactylation at Lys447 activating its function, while peroxisomal import via PEX5 spatially limits its proapoptotic cytosolic activity."},"narrative":{"mechanistic_narrative":"USP2 is a ubiquitin-specific cysteine protease that controls the abundance, surface levels, and signaling output of a broad set of substrates by cleaving ubiquitin isopeptide bonds, thereby acting as a hub deubiquitinase coupling protein stability to cell death, circadian, immune, ion-channel, and metabolic programs [PMID:9325273, PMID:27681596]. Its catalytic mechanism relies on a conserved active site in which Asn271 stabilizes the oxyanion and Asp575 contributes both to oxyanion-hole formation and to aligning the catalytic His557, and substrate recognition requires simultaneous engagement of two ubiquitin surfaces with water-mediated contacts, including molecular determinants (Ub residues 4, 12, 14, 72) that let the enzyme discriminate ubiquitin from NEDD8 [PMID:16905103, PMID:21542621, PMID:28536428]. The enzyme stabilizes substrates predominantly by removing K48-linked polyubiquitin to block proteasomal or lysosomal/endosomal degradation — exemplified by cyclin D1, ErbB2 at endosomes, SKP2, PD-L1 at K270, VPRBP (an upstream p53 repressor), CD47, PPARγ at defined lysines, and PML-RARα [PMID:27681596, PMID:32327714, PMID:34425107, PMID:37670038, PMID:37024504, PMID:40379682, PMID:40993213]; it can also resolve K27- and K48-linked chains on SMAD7 to restrain TGF-β signaling and edit K63-linked chains on BMAL1 and TRAF6 to modulate clock and NF-κB outputs [PMID:35332268, PMID:40540897, PMID:40877242]. Isoform-specific N-terminal domains dictate substrate selectivity: ENaC deubiquitylation requires the USP2-45 N-terminal tail that docks the enzyme onto Nedd4-2, whereas the catalytic core alone is fully active toward ubiquitin-AMC but deficient against ENaC [PMID:21478478]. Through these activities USP2 governs the circadian clock — deubiquitinating PER1 and BMAL1, with Usp2-null mice showing lengthened free-running period, and acting within the suprachiasmatic nucleus to tune photic entrainment [PMID:23213472, PMID:21966515, PMID:39967311] — and operates as a regulatable node, recruited to DNA double-strand breaks by ATM-dependent phosphorylation to stabilize NBS1 and the MRN complex, targeted for degradation by the SPOP E3 ligase, and activated by TGFβ1-driven Lys447 lactylation that is reversed by SIRT2 [PMID:36436562, PMID:41534899, PMID:41310079]. Spatial control is added by PEX5-mediated peroxisomal import via a C-terminal PTS1 signal, which sequesters USP2 from cytosolic partners and limits its proapoptotic activity [PMID:26484888]. USP2 is druggable: the selective inhibitor ML364 binds USP2 directly and triggers cyclin D1 degradation and cell-cycle arrest, and additional chemical probes (6-thioguanine, gambogic acid at Cys284) inhibit the enzyme through distinct allosteric and noncompetitive modes [PMID:27681596, PMID:29449607, PMID:39807309].","teleology":[{"year":1997,"claim":"Established that the USP2 ortholog is a bona fide ubiquitin-specific isopeptidase that recycles ubiquitin rather than degrading conjugated substrates, defining its core biochemical activity.","evidence":"In vitro assays with purified recombinant chick UBP41 on 125I-ubiquitin and ubiquitin-fusion substrates, with active-site inhibitor controls","pmids":["9325273"],"confidence":"High","gaps":["Did not identify physiological substrates","No structural basis for ubiquitin recognition"]},{"year":2003,"claim":"Linked USP2 catalytic activity to a cellular outcome by showing overexpression drives apoptosis dependent on the active site, while isoforms can oligomerize and localize to the cytoplasm.","evidence":"Overexpression of wild-type vs. catalytic-mutant UBP41 with apoptosis/flow assays; Co-IP and immunolocalization of mouse Usp2-45/Usp2-69","pmids":["12566314","14686789"],"confidence":"Medium","gaps":["Proapoptotic substrate not identified","Did not stabilize classical substrates p21/p27","Physiological relevance of overexpression phenotype unclear"]},{"year":2006,"claim":"Resolved how USP2 recognizes ubiquitin, showing two simultaneous ubiquitin interaction surfaces and ordered water-mediated contacts as a general USP recognition mode.","evidence":"X-ray crystallography of the USP2 catalytic domain–ubiquitin complex with mutant inhibition assays","pmids":["16905103"],"confidence":"High","gaps":["Catalytic triad chemistry not yet functionally dissected","Linkage specificity not addressed structurally"]},{"year":2012,"claim":"Dissected the catalytic mechanism and substrate engagement kinetics, redefining triad assignments and revealing conformational rearrangement during diubiquitin cleavage.","evidence":"Site-directed mutagenesis with Ub-AMC and K48-diUb hydrolysis assays, MD simulation; stopped-flow single-turnover kinetics with inactive mutant controls","pmids":["21542621","23211065"],"confidence":"High","gaps":["Mechanism inferred from minimal substrates, not full-length physiological substrates","How conformational change selects chain linkage unresolved"]},{"year":2011,"claim":"Defined isoform-specific substrate selectivity for membrane channels, showing the USP2-45 N-terminal tail positions the enzyme on Nedd4-2 to deubiquitylate ENaC, KCNQ1, and (later) Cav1.2 to control surface expression.","evidence":"Co-IP and GST pull-down of purified proteins, Xenopus oocyte and mammalian electrophysiology, surface biotinylation, with isoform-specific controls","pmids":["21478478","22024150","25366495"],"confidence":"High","gaps":["Structural basis of N-terminal tail substrate positioning not solved","Cav1.2 work is Medium confidence single lab"]},{"year":2011,"claim":"Established USP2 as a circadian clock regulator that deubiquitinates PER1 and controls BMAL1 turnover, with knockout mice showing altered free-running period and light entrainment, later localized to the suprachiasmatic nucleus.","evidence":"Usp2 knockout (including SCN- and retina-specific conditional) mice, Co-IP, in vitro deubiquitination, locomotor rhythm recording, in vivo Per1/p-ERK induction","pmids":["23213472","21966515","39967311"],"confidence":"High","gaps":["PER1 deubiquitination occurs without stability change — functional consequence unclear","Ubiquitin chain linkage on clock substrates partly undefined"]},{"year":2011,"claim":"Connected USP2 to inflammatory and apoptotic signaling, showing it is required for TNF-α-induced NF-κB activation and stabilizes the proapoptotic factor tAIF against CHIP-mediated degradation.","evidence":"siRNA knockdown with IκB/NF-κB readouts and IL-8 ELISA; Co-IP, KD/OE, and cell-death assays for tAIF","pmids":["21480224","21293491"],"confidence":"Medium","gaps":["Direct NF-κB-pathway substrate not defined in these studies","Single-lab findings without reciprocal in vivo validation"]},{"year":2015,"claim":"Showed spatial regulation of USP2 by PEX5-dependent peroxisomal import that sequesters the enzyme from cytosolic partners to limit proapoptotic activity, while early metabolic substrates (IDOL/LDLR, MR) were identified.","evidence":"PTS1-modified isoform overexpression, PEX5 KD/OE, FRAP imaging, apoptosis assays; Co-IP and functional uptake/reporter assays for IDOL-LDLR and MR","pmids":["26484888","26666640","23548632"],"confidence":"Medium","gaps":["Fraction of cellular USP2 that is peroxisomal under physiological conditions unknown","IDOL/LDLR and MR studies single-lab"]},{"year":2016,"claim":"Validated USP2 as a druggable target by identifying ML364, a direct-binding inhibitor that induces cyclin D1 degradation, cell-cycle arrest, and reduced HR repair.","evidence":"Fluorescent di-ubiquitin biochemical assay, microscale thermophoresis binding, Western blot, flow cytometry, HR repair assay","pmids":["27681596"],"confidence":"High","gaps":["Direct cyclin D1 deubiquitination not biochemically reconstituted in this study","Selectivity across DUB family not exhaustively profiled"]},{"year":2018,"claim":"Expanded the chemical-probe toolkit and defined distinct inhibition modes, including noncompetitive slow-binding inhibition by 6-thioguanine and covalent allosteric inhibition at Cys284 by gambogic acid.","evidence":"Enzyme kinetics and X-ray crystallography (6-thioguanine); covalent binding characterization with functional KRAS readouts (gambogic acid)","pmids":["29449607","39807309"],"confidence":"High","gaps":["Cellular selectivity of covalent probe not fully resolved","Gambogic-acid study is Medium confidence single lab"]},{"year":2022,"claim":"Established USP2 as a DNA-damage-response component recruited to double-strand breaks by ATM phosphorylation to stabilize NBS1 and the MRN complex, defining post-translational control of USP2 activity at chromatin.","evidence":"DUB screen, Co-IP, chromatin fractionation at DSBs, ATM inhibition, double siRNA knockdown with USP28, HR repair assay","pmids":["36436562"],"confidence":"Medium","gaps":["Specific ATM phosphosites mapped only as N-terminal residues","Redundancy with USP28 complicates attribution"]},{"year":2023,"claim":"Positioned USP2 as a regulator of tumor immune evasion by stabilizing PD-L1 (K48 chains at K270), CD47, and the p53-repressor VPRBP, nominating it as an immuno-oncology target sparing normal tissue.","evidence":"sgRNA screens, Co-IP, K48-linkage-specific ubiquitination assays, mutagenesis, phagocytosis assays, in vivo tumor models with immune profiling and anti-PD1 combination","pmids":["37670038","37024504","40379682"],"confidence":"Medium","gaps":["Whether one or multiple immune substrates dominate the therapeutic effect unresolved","Most mechanistic detail from individual labs"]},{"year":2025,"claim":"Revealed metabolic deubiquitination programs and a novel activating PTM, showing USP2 stabilizes PPARγ at defined lysines to drive lipid accumulation, muscle insulin sensitivity, and thermogenesis, and is switched on by TGFβ1-driven Lys447 lactylation reversed by SIRT2.","evidence":"Site-specific K48 ubiquitination mapping, mutagenesis, global/tissue-specific KO mice, lactylation mapping and SIRT2 delactylation assays, fibrosis and metabolic models","pmids":["40993213","39874418","40189098","41310079"],"confidence":"Medium","gaps":["Lactylation finding is recent single-lab","How lactylation mechanistically activates catalysis not structurally defined"]},{"year":2025,"claim":"Identified upstream control of USP2 levels by the SPOP E3 ligase and transcriptional regulators, closing feedback loops onto immune (CD47) and other substrate axes.","evidence":"Co-IP, in vitro deubiquitination, ubiquitination assays, flow cytometry, phagocytosis and syngeneic tumor models","pmids":["41534899"],"confidence":"Medium","gaps":["SPOP degron on USP2 not finely mapped","Single-lab study"]},{"year":null,"claim":"How USP2 selects among its very large, context-dependent substrate repertoire and which interactions are direct versus scaffold-mediated remains the central open question.","evidence":"Many substrate claims rest on single-lab Co-IP plus ubiquitination assays without structural or reciprocal in vitro reconstitution","pmids":[],"confidence":"Low","gaps":["No structures of USP2 bound to full-length substrates","Cell-type and isoform determinants of substrate choice undefined","Several substrates (FOXC1, LEF1, JUP, MMP2, p53-K305R) supported by single Low-confidence studies"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,8,16,25,35]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,10,11]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[1,11,17]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,47]},{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[47]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8,9,15]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[20]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[24]}],"pathway":[{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[6,7,45]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,25,27,42]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[24]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[35,36,40,51]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,16,21,25]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,4,28]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[23,37,42]}],"complexes":["MRE11-RAD50-NBS1 (MRN) complex","CLOCK/BMAL1 circadian complex"],"partners":["NEDD4-2","SKP2","PD-L1","CD47","PPARG","SMAD7","VPRBP","SPOP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75604","full_name":"Ubiquitin carboxyl-terminal hydrolase 2","aliases":["41 kDa ubiquitin-specific protease","Deubiquitinating enzyme 2","Ubiquitin thioesterase 2","Ubiquitin-specific-processing protease 2"],"length_aa":605,"mass_kda":68.1,"function":"Hydrolase that deubiquitinates polyubiquitinated target proteins such as MDM2, MDM4 and CCND1 (PubMed:17290220, PubMed:19838211, PubMed:19917254). Isoform 1 and isoform 4 possess both ubiquitin-specific peptidase and isopeptidase activities (By similarity). Deubiquitinates MDM2 without reversing MDM2-mediated p53/TP53 ubiquitination and thus indirectly promotes p53/TP53 degradation and limits p53 activity (PubMed:17290220, PubMed:19838211). Has no deubiquitinase activity against p53/TP53 (PubMed:17290220). Prevents MDM2-mediated degradation of MDM4 (PubMed:17290220). Plays a role in the G1/S cell-cycle progression in normal and cancer cells (PubMed:19917254). Regulates the circadian clock by modulating its intrinsic circadian rhythm and its capacity to respond to external cues (By similarity). Associates with clock proteins and deubiquitinates core clock component PER1 but does not affect its overall stability (By similarity). Regulates the nucleocytoplasmic shuttling and nuclear retention of PER1 and its repressive role on the clock transcription factors CLOCK and BMAL1 (By similarity). Plays a role in the regulation of myogenic differentiation of embryonic muscle cells (By similarity) Circadian clock output effector that regulates Ca(2+) absorption in the small intestine. Probably functions by regulating protein levels of the membrane scaffold protein NHERF4 in a rhythmic manner, and is therefore likely to control Ca(2+) membrane permeability mediated by the Ca(2+) channel TRPV6 in the intestine","subcellular_location":"Nucleus; Membrane; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O75604/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/USP2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/USP2","total_profiled":1310},"omim":[{"mim_id":"615143","title":"UBIQUITIN-SPECIFIC PROTEASE 20; USP20","url":"https://www.omim.org/entry/615143"},{"mim_id":"604725","title":"UBIQUITIN-SPECIFIC PROTEASE 2; USP2","url":"https://www.omim.org/entry/604725"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":157.6}],"url":"https://www.proteinatlas.org/search/USP2"},"hgnc":{"alias_symbol":["UBP41"],"prev_symbol":[]},"alphafold":{"accession":"O75604","domains":[{"cath_id":"-","chopping":"269-374","consensus_level":"medium","plddt":94.0082,"start":269,"end":374}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75604","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75604-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75604-F1-predicted_aligned_error_v6.png","plddt_mean":68.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=USP2","jax_strain_url":"https://www.jax.org/strain/search?query=USP2"},"sequence":{"accession":"O75604","fasta_url":"https://rest.uniprot.org/uniprotkb/O75604.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75604/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75604"}},"corpus_meta":[{"pmid":"16905103","id":"PMC_16905103","title":"Structural basis of ubiquitin recognition by the 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recognition by USPs.\",\n      \"method\": \"X-ray crystallography, ubiquitin mutant inhibition assays, peptide inhibition assays\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and inhibition assays in a single rigorous study\",\n      \"pmids\": [\"16905103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Chick UBP41 (USP2 ortholog) is a ubiquitin-specific protease (cysteine protease) with isopeptidase activity; it cleaves ubiquitin from the C-terminus of natural and engineered ubiquitin fusions regardless of size, releases free ubiquitin from di-ubiquitin, and converts poly-ubiquitinated lysozyme conjugates to mono-ubiquitinated forms without further degradation, suggesting a role in ubiquitin recycling. The enzyme is inhibited by ubiquitin-aldehyde and sulfhydryl-blocking agents.\",\n      \"method\": \"In vitro enzyme assay with purified recombinant protein, 125I-labeled ubiquitin substrates, ubiquitin-β-galactosidase fusion substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified enzyme and multiple substrates, active-site inhibitor validation\",\n      \"pmids\": [\"9325273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse Usp2-69 isoform can form a homo-complex and a hetero-complex with Usp2-45. Both isoforms localize to the cytoplasm when overexpressed in COS-7 and NIH3T3 cells.\",\n      \"method\": \"Co-immunoprecipitation, overexpression in COS-7 and NIH3T3 cells, immunohistochemistry\",\n      \"journal\": \"Gene expression\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP and immunolocalization, single lab, two orthogonal methods\",\n      \"pmids\": [\"14686789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Overexpression of UBP41 (USP2) is sufficient to induce apoptosis in human cells; an enzymatically defective UBP41 mutant did not induce cell death, demonstrating that the proapoptotic activity requires catalytic activity. Overexpression caused broad deubiquitination but did not stabilize known proteasome substrates p21 or p27, and did not arrest cells in G2/M.\",\n      \"method\": \"Overexpression of wild-type and catalytic mutant UBP41, apoptosis assays, flow cytometry, Western blot\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — catalytic mutant controls establish requirement for enzymatic activity; single lab\",\n      \"pmids\": [\"12566314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2 deubiquitinates and stabilizes truncated AIF (tAIF), promoting AIF-mediated caspase-independent cell death. CHIP ubiquitin E3 ligase antagonizes this by ubiquitinating and destabilizing tAIF. Knockdown of USP2 attenuated MNNG-induced cell death.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression, Western blot for tAIF ubiquitination and stability, cell death assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal functional experiments with KD and OE plus Co-IP; single lab\",\n      \"pmids\": [\"21293491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2 is required for TNF-α-induced NF-κB signaling; siRNA knockdown of USP2 prevented IκB phosphorylation, nuclear translocation of NF-κB, expression of NF-κB target genes, and IL-8 secretion. Isoform-specific functions were identified.\",\n      \"method\": \"Targeted siRNA screen, Western blot for IκB phosphorylation and NF-κB translocation, IL-8 ELISA\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional siRNA screen with multiple mechanistic readouts; single lab\",\n      \"pmids\": [\"21480224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2 coimmunoprecipitates with clock proteins and directly interacts with PER1, deubiquitinating PER1 without altering its stability. Usp2 knockout mice display a longer free-running circadian period and altered clock gene expression.\",\n      \"method\": \"Co-immunoprecipitation, Usp2 knockout mouse model, locomotor rhythm recording, in vitro deubiquitination assay, Western blot\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse phenotype plus Co-IP plus in vitro deubiquitination, multiple orthogonal methods replicated across two USP2 circadian papers\",\n      \"pmids\": [\"23213472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2b is in a complex with BMAL1 and regulates its stability and turnover, altering expression of CLOCK/BMAL1-controlled genes; USP2 knockout increases phase delays in response to low irradiance light.\",\n      \"method\": \"Co-immunoprecipitation, USP2 knockout mouse model, luciferase reporter, Western blot\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with KO phenotype; single lab\",\n      \"pmids\": [\"21966515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2-45 physically interacts with ENaC subunits (via the α-ENaC cytoplasmic N-terminal domain) and with the HECT domain of Nedd4-2 (by both its catalytic domain and N-terminal tail), promoting ENaC deubiquitylation and increased surface expression. The Usp2-69 isoform, which lacks the specific N-terminal domain, is inactive toward ENaC. The catalytic core alone has reduced activity toward ENaC in oocytes despite retaining full activity toward ubiquitin-AMC.\",\n      \"method\": \"Co-immunoprecipitation in HEK293 cells, GST pull-down of purified recombinant proteins, Xenopus laevis oocyte electrophysiology\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reconstitution with purified proteins (GST pull-down) plus Co-IP plus functional electrophysiology, isoform-specific controls\",\n      \"pmids\": [\"21478478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2-45 and USP2-69 both counteract Nedd4-2-mediated downregulation of KCNQ1/KCNE1 channels by deubiquitylating KCNQ1, restoring surface expression and membrane localization. USP2 binds KCNQ1 independently of the PY motif.\",\n      \"method\": \"Electrophysiology in Xenopus oocytes and mammalian cells, co-immunoprecipitation, Western blot for ubiquitin and surface KCNQ1, immunocytochemistry\",\n      \"journal\": \"Heart rhythm\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (electrophysiology, biochemistry, imaging); replicated for two USP2 isoforms\",\n      \"pmids\": [\"22024150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP2 contributes to active site catalysis through a conserved Asn271 that directly stabilizes the oxyanion in the acylation step, structurally supported by absolutely conserved Asp575. Asn574, positioned as the putative third catalytic triad member, does not fulfill this role functionally. Asp575 has a dual role in oxyanion hole formation and maintaining His557 alignment.\",\n      \"method\": \"Site-directed mutagenesis, in vitro hydrolysis assays (ubiquitin-AMC, K48-linked diubiquitin), mass spectrometry-based assay, molecular dynamics simulation\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis with multiple substrates and computational validation in a single rigorous study\",\n      \"pmids\": [\"21542621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Stopped-flow kinetics revealed that monoubiquitin binds USP2 in a simple one-step process, while K48-linked diubiquitin shows biphasic binding, indicating a conformational rearrangement of the diubiquitin substrate during USP2 catalysis.\",\n      \"method\": \"Stopped-flow fluorescence kinetics, single-turnover deubiquitination assays with Ub-AMC and K48-linked IQF-diubiquitin, inactive USP2 mutant binding studies\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro transient kinetics with inactive mutant controls and global fitting; single rigorous study\",\n      \"pmids\": [\"23211065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP2-45 binds the α2δ-1 accessory subunit (but not Cav1.2 or β2 subunits) of voltage-gated calcium channels and promotes deubiquitylation of both Cav1.2 and α2δ-1 subunits, reducing Cav1.2 current amplitude and surface expression. Co-expression of α2δ-1 is required for the effect of USP2-45.\",\n      \"method\": \"Whole-cell current recordings, surface biotinylation assays, co-immunoprecipitation in tsA-201 and HEK-293 cells\",\n      \"journal\": \"Pflugers Archiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology plus biochemistry with required accessory subunit controls; single lab\",\n      \"pmids\": [\"25366495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP2 (both USP2-69 and USP2-45 isoforms) interacts with the E3-ubiquitin ligase IDOL and promotes its deubiquitylation, stabilizing IDOL protein. Paradoxically, in a tri-partite USP2-IDOL-LDLR complex, USP2 also deubiquitylates the LDLR and prevents its IDOL-mediated lysosomal degradation, thereby increasing LDL uptake.\",\n      \"method\": \"Genetic screening, co-immunoprecipitation, Western blot for protein stability, LDL uptake assay\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional LDL uptake assay; single lab, multiple isoforms tested\",\n      \"pmids\": [\"26666640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP2-45 binds MR (mineralocorticoid receptor) and, similarly to aldosterone, promotes removal of MR monoubiquitylation, disrupts MR/TSG101 association, and destabilizes MR protein, constituting a negative feedback loop limiting aldosterone-induced responses.\",\n      \"method\": \"Co-immunoprecipitation, Western blot for MR ubiquitylation and stability, luciferase reporter for MR transcriptional activity\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus reporter assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"23548632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP2-45 functions as a circadian clock output effector regulating calcium absorption. In the small intestine, USP2-45 is found in membrane fractions, negatively regulates NHERF4 protein abundance in a rhythmic manner, and interacts in vitro with NHERF4 and endogenous Clathrin Heavy Chain. Usp2 knockout mice show hyperabsorption of dietary Ca2+ associated with strong NHERF4 overexpression and TRPV6 upregulation.\",\n      \"method\": \"Usp2 knockout mouse model, subcellular fractionation, in vitro interaction assay (Co-IP), dietary calcium measurement, Drosophila dUsp2 knockdown rescue with dietary Ca2+\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse phenotype plus in vitro interaction and fractionation; single lab, two orthogonal methods\",\n      \"pmids\": [\"26756164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP2 inhibitor ML364 (IC50 1.1 µM) induces cyclin D1 degradation and cell cycle arrest in colorectal cancer and mantle cell lymphoma cells, and decreases homologous recombination-mediated DNA repair. Direct binding of ML364 to USP2 was demonstrated.\",\n      \"method\": \"Fluorescent di-ubiquitin biochemical assay, microscale thermophoresis, Western blot, flow cytometry, HR repair assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical inhibitor assay plus direct binding measurement plus multiple cellular readouts; single rigorous study with orthogonal methods\",\n      \"pmids\": [\"27681596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Residues Ub4K, Ub12E, Ub14E, and Ub72A serve as the molecular determinants enabling USP2 to distinguish between ubiquitin and NEDD8. Combining NEDD8 residues at positions 4, 12, 14, and 72 to match ubiquitin makes NEDD8 accessible for hydrolysis by USP2. USP2 binds the N-terminus of ubiquitin to form a stable interaction before engaging the C-terminus for substrate specificity.\",\n      \"method\": \"Ubiquitin/NEDD8 mutagenesis, in vitro hydrolysis assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic mutagenesis with in vitro functional validation; single lab\",\n      \"pmids\": [\"28536428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"6-Thioguanine inhibits USP2 through a noncompetitive and slow-binding mechanism. X-ray crystallographic data confirmed the binding mode.\",\n      \"method\": \"Enzyme kinetics, X-ray crystallography\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with kinetic characterization; single lab\",\n      \"pmids\": [\"29449607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USP2 promotes Twist protein stabilization by removing β-TrCP-mediated ubiquitination of Twist, maintaining cancer stem cell populations in TNBC through Twist-mediated EMT and Bmi1 activation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, genetic and pharmacological USP2 inhibition, Western blot, in vivo xenograft\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiments; single lab\",\n      \"pmids\": [\"30918246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP2 associates with internalized ErbB2 at endosomes and prevents its lysosomal sorting and degradation by exerting deubiquitylase activity, safeguarding ErbB2 surface levels against ubiquitylation-mediated endocytic degradation.\",\n      \"method\": \"Co-immunoprecipitation, Western blot for ErbB2 ubiquitylation, endocytic trafficking assays, USP2 inhibitor ML364\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus functional endocytic assay; single lab\",\n      \"pmids\": [\"32327714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP2 is a deubiquitylase of SKP2, binding via the leucine-rich repeat substrate-binding domain on SKP2 to deubiquitylate and stabilize SKP2 protein. USP2-stabilized SKP2 does not destabilize its substrates p21 and p27 because USP2 binding to SKP2 disrupts the SKP2-substrate interaction.\",\n      \"method\": \"DUB panel screening by Co-IP with endogenous SKP2, siRNA knockdown, small-molecule inhibition, CHX chase assay, ubiquitination assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — endogenous Co-IP, ubiquitination assay, domain interaction mapping; single lab\",\n      \"pmids\": [\"34425107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP2 stabilizes E2F4 protein through physical interaction and deubiquitination, promoting E2F4-driven transcription of ATG2A and ULK2, resulting in autophagic degradation of metallothionein proteins and altered zinc homeostasis in cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, deubiquitination assay, BiFC, gain/loss-of-function studies, ChIP, rescue experiments\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus deubiquitination assay plus multiple orthogonal functional methods; single lab\",\n      \"pmids\": [\"35253629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP2 interacts with SMAD7 and stabilizes it by cleaving Lys27- and Lys48-linked poly-ubiquitin chains. Lys27-linked poly-ubiquitin chains at SMAD7 K185 mediate SMAD7 recruitment to HERC3, which in turn regulates Lys63-linked polyubiquitination of SMAD7. Loss of USP2 induces TGF-β signaling and glioblastoma progression.\",\n      \"method\": \"Co-immunoprecipitation, in vitro deubiquitination assay distinguishing linkage types, USP2 knockout/overexpression, in vivo GBM model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination analysis; single lab\",\n      \"pmids\": [\"35332268\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP2 deubiquitinates NBS1, stabilizing the MRE11-RAD50-NBS1 complex at DNA double-strand break (DSB) sites. USP2 is recruited to DSB sites in an ATM-dependent manner, and phosphorylation of two critical N-terminal residues of USP2 by ATM is required for recruitment and interaction with RECQL4. Loss of both USP2 and USP28 causes premature MRN disassembly from DSBs, defects in ATM activation, and impaired homologous recombination repair.\",\n      \"method\": \"DUB screen, co-immunoprecipitation, chromatin fractionation at DSBs, ATM kinase inhibition, siRNA double knockdown, HR repair assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional DUB screen plus Co-IP plus mechanistic epistasis; single lab\",\n      \"pmids\": [\"36436562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP2 directly interacts with PD-L1 and deconjugates K48-linked polyubiquitination at lysine 270 of PD-L1, stabilizing PD-L1. Key residues Thr288, Arg292, and Asp293 of USP2 control its binding to PD-L1. USP2 depletion causes ER-associated degradation of PD-L1.\",\n      \"method\": \"sgRNA screening, co-immunoprecipitation, ubiquitination assay (K48-specific), site-directed mutagenesis, Western blot, in vivo tumor models with immune profiling\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — sgRNA screen plus Co-IP plus linkage-specific ubiquitination assay plus mutagenesis plus in vivo validation; multiple orthogonal methods in single study\",\n      \"pmids\": [\"37670038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP2 deubiquitinates and stabilizes VPRBP, a potent repressor of p53. The USP2-VPRBP axis controls both p53 and PD-L1 expression, and USP2 knockout in mice does not affect normal tissues (unlike MDM2 inhibition).\",\n      \"method\": \"Co-immunoprecipitation, Western blot for VPRBP ubiquitination, USP2 knockout mice, genetic and pharmacological inhibition combined with anti-PD1\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo KO characterization; single lab\",\n      \"pmids\": [\"37024504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP2 directly interacts with CD47 and stabilizes it through deubiquitination. USP2 inhibition destabilizes CD47, enhancing macrophage phagocytosis of tumor cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, in vitro deubiquitination, phagocytosis assay, in vivo tumor models, single-cell RNA sequencing\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus deubiquitination assay plus functional phagocytosis assay; single lab\",\n      \"pmids\": [\"40379682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP2 interacts with survivin and stabilizes it; pharmacological inhibition of USP2 by ML364 increases survivin ubiquitination and degradation, sensitizing cancer cells to TRAIL-induced apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, Western blot, cell death assay with survivin overexpression rescue\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiment; single lab\",\n      \"pmids\": [\"37628997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP2 deubiquitinates ACE2, serving as its physiological deubiquitinase; targeted inhibition with ML364 leads to marked and reversible reduction in ACE2 protein abundance, blocking ACE2-dependent coronavirus infection in vitro and in vivo.\",\n      \"method\": \"USP2 inhibitor ML364, Co-immunoprecipitation, Western blot for ACE2 ubiquitination, viral infection assays, human ACE2 transgenic mouse models\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo mouse model; single lab\",\n      \"pmids\": [\"38055802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP2 stably binds NCOA4 and suppresses its degradation by removing K48-linked ubiquitin chains from NCOA4, thereby enabling ferritinophagy and ferroptosis in esophageal squamous cell carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K48-specific), USP2 KO in ESCC model, in vitro and in vivo ferroptosis assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination assay plus in vivo model; single lab\",\n      \"pmids\": [\"38744953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"VCP recruits USP2 to FASN, and USP2 removes K48-linked ubiquitin chains from FASN to stabilize it; VCP domain 2 and a specific USP2 amino acid sequence are critical for their interaction. This stabilization promotes autophagy in osteosarcoma.\",\n      \"method\": \"Co-IP/MS, ubiquitination assay, molecular docking, protein truncation mapping, gain/loss-of-function experiments\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS plus domain mapping plus ubiquitination assay; single lab\",\n      \"pmids\": [\"39489738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP2 deubiquitinates and stabilizes EZH2 by directly binding to it and reducing its ubiquitination; USP2-stabilized EZH2 promotes H3K27me3 enrichment and epigenetic silencing of SOX1 in bladder cancer.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, CHX chase, ChIP assay, in vivo xenograft\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus ChIP; single lab\",\n      \"pmids\": [\"39197387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP2 deubiquitinates and stabilizes MFN2 in cardiomyocytes, counteracting Angiotensin II-induced calcium overload and mitochondrial dysfunction. Rescue experiments confirmed that MFN2 downregulation abolishes the protective role of USP2.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, in vitro and in vivo cardiac hypertrophy models\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus rescue experiments; single lab\",\n      \"pmids\": [\"37100191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP2 deubiquitinates and stabilizes KRAS in multiple myeloma cells. Gambogic acid forms a covalent bond with USP2 Cys284 through an allosteric pocket, inhibiting USP2 deubiquitinating activity and causing KRAS degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, covalent binding characterization, USP2 knockdown/overexpression, in vitro and in vivo proliferation assays\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus covalent inhibitor characterization plus functional validation; single lab\",\n      \"pmids\": [\"39807309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 directly interacts with PPAR-γ and deubiquitinates it by removing K48-linked ubiquitin chains at lysine 161, stabilizing PPAR-γ protein and enhancing its transcriptional activity to promote hepatic lipid accumulation in MASLD.\",\n      \"method\": \"Co-immunoprecipitation, K48-specific ubiquitination assay, site-specific mutagenesis, KO mice, in vivo siRNA targeting, Western blot\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — site-specific ubiquitination mapping plus mutagenesis plus Co-IP plus KO mouse model with multiple orthogonal methods\",\n      \"pmids\": [\"40993213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 directly interacts with PPAR-γ and deubiquitinates it to stabilize protein levels, enhancing insulin signaling and muscle mass maintenance. MYOD1 activates USP2 transcription by binding to the USP2 promoter region. Loss of PPAR-γ abolishes the regulatory effects of USP2 on insulin sensitivity and muscle atrophy.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, USP2 knockout mouse models (global and muscle-specific), promoter binding assay, AAV-Usp2 injection\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus tissue-specific KO; single lab\",\n      \"pmids\": [\"39874418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates TXNDC5 (stabilizing TGFβR1 to activate TGF-β signaling) and the transferrin receptor TFRC (enhancing ferroptosis). TGF-β1 activates USP2 by lactylation at Lys447, while SIRT2 delactylates USP2 at Lys447 to suppress its activity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, lactylation mapping, SIRT2 delactylation assay, tissue-specific KO mice, organ fibrosis models, ML364 treatment\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple substrate Co-IP and ubiquitination assays plus novel PTM (lactylation) identification; single lab\",\n      \"pmids\": [\"41310079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates and stabilizes p300 histone acetyltransferase in hepatic stellate cells, promoting fibrogenic responses and HSC activation.\",\n      \"method\": \"DUB inhibitor screen in activated HSCs, co-immunoprecipitation, Western blot for p300 stability, USP2 knockdown/pharmacological inhibition\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional screen plus Co-IP plus pharmacological validation; single lab\",\n      \"pmids\": [\"41703985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates PML-RARα, including its drug-resistant mutants, stabilizing the fusion protein. USP2 inhibition or silencing reduces PML-RARα protein in an ATRA-sensitive and ATRA-resistant manner, reversed by proteasome inhibition.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, proteasome inhibition rescue, USP2 overexpression/knockdown, ML364 treatment, apoptosis assay\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus proteasome rescue; single lab\",\n      \"pmids\": [\"41445506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 interacts with and deubiquitinates EBF2 in brown adipose tissue, stabilizing EBF2 protein and mediating thermogenic gene expression (including UCP1). BAT-specific Usp2 knockdown or systemic USP2 inhibition impairs thermogenic programs; Usp2 overexpression in BAT protects against high-fat diet-induced obesity.\",\n      \"method\": \"Quantitative proteomics, co-immunoprecipitation, immunofluorescence, adeno-associated virus-mediated Usp2 manipulation, seahorse metabolic analysis, electron microscopy\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteome-wide substrate screen plus Co-IP plus in vivo mouse models; single lab\",\n      \"pmids\": [\"40189098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPOP E3 ubiquitin ligase ubiquitinates USP2, leading to its degradation and decreased CD47 protein abundance. USP2 deubiquitinates CD47 and protects it from proteasome-mediated degradation, confirming the SPOP/USP2/CD47 regulatory axis.\",\n      \"method\": \"Co-immunoprecipitation, in vitro deubiquitination assay, ubiquitination assay, cell fractionation, flow cytometry, phagocytosis assay, syngeneic tumor models\",\n      \"journal\": \"Journal for immunotherapy of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus in vitro deubiquitination assay plus functional phagocytosis and in vivo data; single lab\",\n      \"pmids\": [\"41534899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 attenuates TRAF6 K63-linked polyubiquitination in intestinal epithelial cells, dampening NF-κB activation and myosin light chain phosphorylation to preserve tight junction integrity. Colonic-specific USP2 overexpression in mice ameliorated DSS-induced barrier damage.\",\n      \"method\": \"Co-immunoprecipitation, K63-specific ubiquitination assay, Western blot for NF-κB/MLCK/MLC phosphorylation, in vivo colitis model with colonic USP2 overexpression\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination plus in vivo model; single lab\",\n      \"pmids\": [\"40540897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 directly interacts with FOXC1 and deubiquitinates it, stabilizing FOXC1 protein and protecting neuronal cells from MPP+-induced injury.\",\n      \"method\": \"Co-immunoprecipitation, Western blot for ubiquitination/stability, overexpression rescue, cell viability and apoptosis assays\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP plus ubiquitination assay; single lab, single study\",\n      \"pmids\": [\"40355038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 stabilizes LEF1 protein by mediating LEF1 deubiquitination, promoting osteogenic differentiation of bone marrow mesenchymal stem cells. Increased USP2 expression reduced bone loss in ovariectomy mouse model.\",\n      \"method\": \"Co-immunoprecipitation, protein stability assay, USP2/LEF1 knockdown, in vivo OVX mouse model\",\n      \"journal\": \"Journal of orthopaedic surgery and research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus stability assay; single lab, single study\",\n      \"pmids\": [\"40301985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In the suprachiasmatic nucleus (SCN), USP2 modulates photic entrainment of the circadian clock by regulating light-induced Per1 expression and MAPK/ERK pathway activation. SCN-specific Usp2 KO recapitulates the light entrainment phenotype of full-body KO, while retinal Usp2 KO does not.\",\n      \"method\": \"Conditional Usp2 knockout (SCN-specific and retina-specific), running wheel recordings, in vivo light induction of Per1 and p-ERK in SCN\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific KO with molecular pathway readouts; single lab\",\n      \"pmids\": [\"39967311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP2 interacts with TRAF2 and removes its ubiquitination chains, stabilizing TRAF2 protein in fibroblast-like synoviocytes and promoting NF-κB-related inflammation in rheumatoid arthritis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, Western blot, in vivo CIA rat model\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus ubiquitination assay; single lab, single study\",\n      \"pmids\": [\"38480669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Peroxisomal import of USP2 is mediated by PEX5 (PTS1 receptor) recognizing a C-terminal PTS1 signal; this import reduces USP2 proapoptotic activity by spatially separating it from cytosolic and nuclear interaction partners. All four USP2 isoforms are post-translationally imported into peroxisomes.\",\n      \"method\": \"Overexpression of USP2 isoforms with modified PTS1, apoptosis assays, PEX5 knockdown/overexpression, live-cell imaging (FRAP)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — subcellular localization directly linked to functional consequence (apoptosis) with PEX5-dependent import validation\",\n      \"pmids\": [\"26484888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DCAF7 recruits USP2 to suppress clockophagy (selective autophagic degradation of BMAL1) by reducing BMAL1 K63-linked polyubiquitination, thereby inhibiting ferroptosis through the HIF1α-SLC7A11 axis in hepatocellular carcinoma.\",\n      \"method\": \"Co-immunoprecipitation, K63-specific ubiquitination assay, genetic ablation of DCAF7/USP2, in vitro and in vivo HCC models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus linkage-specific ubiquitination assay plus functional in vivo data; single lab\",\n      \"pmids\": [\"40877242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates and stabilizes JUP (junction plakoglobin), blocking Akt/β-catenin pathway activation to protect against cardiac hypertrophy. Mycn transcriptionally activates USP2 expression by binding to the USP2 promoter.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, luciferase promoter assay, gain/loss-of-function in ISO-induced cardiac hypertrophy models\",\n      \"journal\": \"BMC cardiovascular disorders\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus ubiquitination assay plus promoter assay; single lab, single study\",\n      \"pmids\": [\"38297207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates and stabilizes TRAF2 in nasopharyngeal carcinoma, promoting NF-κB signaling, and directly binds MMP2 to reduce K48-linked polyubiquitination, extending MMP2 protein half-life.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K48-specific), CHX chase assay, NF-κB inhibition rescue\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus ubiquitination assay; single lab, single study\",\n      \"pmids\": [\"41144793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates and stabilizes PPARγ by removing K48-linked chains at the K142 site, promoting fatty acid biosynthesis in hepatocellular carcinoma and oleic acid-mediated M2 macrophage polarization, which creates an IL-10/STAT3/USP2 positive-feedback loop.\",\n      \"method\": \"Co-immunoprecipitation, CUT&RUN, ELISA, mass spectrometry, K48-specific ubiquitination assay, in vitro co-culture system, patient-derived organoids\",\n      \"journal\": \"Journal for immunotherapy of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus site-specific ubiquitination mapping plus CUT&RUN plus MS; single lab\",\n      \"pmids\": [\"41193183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP2 reduces Keap1 deubiquitination (stabilizing Keap1), leading to Nrf2 inactivation, impaired iron metabolism, and lipid peroxidation, thereby promoting ferroptosis in macrophages and driving atherosclerosis. USP2 knockout macrophages show elevated Keap1 ubiquitination.\",\n      \"method\": \"USP2 knockout macrophages, ubiquitination assay for Keap1, ferroptosis assays, in vivo atherosclerosis model (apoE-/- mice), USP2 KO mice\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO macrophages plus ubiquitination assay plus in vivo model; single lab\",\n      \"pmids\": [\"39228119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP2 deubiquitinates and stabilizes antithrombin by counteracting Cullin 2-RBX1-mediated ubiquitination and degradation. USP2 overexpression inhibits antithrombin ubiquitination, while USP2 knockdown or pharmacological inhibition downregulates antithrombin.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression, proteasome inhibition, neddylation inhibition\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus multiple functional perturbations; single lab\",\n      \"pmids\": [\"34324733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP2 deubiquitinates and stabilizes TJP1/TWIST1 in bladder cancer; TJP1 acts as a scaffold recruiting USP2 to TWIST1, protecting TWIST1 from proteasomal degradation and promoting CCL2-driven angiogenesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, TJP1/USP2 interaction mapping, in vitro and in vivo rescue experiments\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus in vivo data; single lab\",\n      \"pmids\": [\"34782718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP2 deubiquitinates and stabilizes p53 at the K305R site, removing ubiquitin to modulate cisplatin resistance through ferroptosis in NSCLC. USP2 overexpression increases nuclear p53 and promotes ferroptosis markers while reducing GPX4 and SLC7A11.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (site-specific K305R), Western blot, in vivo xenograft\",\n      \"journal\": \"BMC medical genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP plus site-specific ubiquitination assay; single lab, single study\",\n      \"pmids\": [\"40011884\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"USP2 is a multifunctional cysteine deubiquitinase whose catalytic triad (Cys-His-Asn/Asp) cleaves ubiquitin isopeptide bonds from a structurally defined interface requiring simultaneous engagement of two ubiquitin surfaces; it stabilizes a broad array of substrates—including cyclin D1, MDM2/VPRBP (regulating p53), FASN, ErbB2, PD-L1, CD47, SKP2, TWIST, SMAD7, NBS1, MFN2, PPARγ, EBF2, ACE2, PML-RARα, and ion channel regulators (ENaC, KCNQ1, Cav1.2)—by removing K48-linked polyubiquitin chains and preventing proteasomal or lysosomal degradation; it also deubiquitinates K63-linked chains on BMAL1 and TRAF6 to modulate circadian clock function and NF-κB signaling, respectively; isoform-specific N-terminal domains (USP2-45 vs. USP2-69) determine substrate selectivity (e.g., ENaC deubiquitylation requires the USP2-45 N-terminal tail that positions the enzyme via Nedd4-2 binding); USP2 itself is regulated by ATM-mediated phosphorylation at DSBs, by SPOP-mediated ubiquitination targeting it for degradation, and by TGFβ1-driven lactylation at Lys447 activating its function, while peroxisomal import via PEX5 spatially limits its proapoptotic cytosolic activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"USP2 is a ubiquitin-specific cysteine protease that controls the abundance, surface levels, and signaling output of a broad set of substrates by cleaving ubiquitin isopeptide bonds, thereby acting as a hub deubiquitinase coupling protein stability to cell death, circadian, immune, ion-channel, and metabolic programs [#1, #16]. Its catalytic mechanism relies on a conserved active site in which Asn271 stabilizes the oxyanion and Asp575 contributes both to oxyanion-hole formation and to aligning the catalytic His557, and substrate recognition requires simultaneous engagement of two ubiquitin surfaces with water-mediated contacts, including molecular determinants (Ub residues 4, 12, 14, 72) that let the enzyme discriminate ubiquitin from NEDD8 [#0, #10, #17]. The enzyme stabilizes substrates predominantly by removing K48-linked polyubiquitin to block proteasomal or lysosomal/endosomal degradation — exemplified by cyclin D1, ErbB2 at endosomes, SKP2, PD-L1 at K270, VPRBP (an upstream p53 repressor), CD47, PPARγ at defined lysines, and PML-RARα [#16, #20, #21, #25, #26, #27, #35]; it can also resolve K27- and K48-linked chains on SMAD7 to restrain TGF-β signaling and edit K63-linked chains on BMAL1 and TRAF6 to modulate clock and NF-κB outputs [#23, #42, #48]. Isoform-specific N-terminal domains dictate substrate selectivity: ENaC deubiquitylation requires the USP2-45 N-terminal tail that docks the enzyme onto Nedd4-2, whereas the catalytic core alone is fully active toward ubiquitin-AMC but deficient against ENaC [#8]. Through these activities USP2 governs the circadian clock — deubiquitinating PER1 and BMAL1, with Usp2-null mice showing lengthened free-running period, and acting within the suprachiasmatic nucleus to tune photic entrainment [#6, #7, #45] — and operates as a regulatable node, recruited to DNA double-strand breaks by ATM-dependent phosphorylation to stabilize NBS1 and the MRN complex, targeted for degradation by the SPOP E3 ligase, and activated by TGFβ1-driven Lys447 lactylation that is reversed by SIRT2 [#24, #41, #37]. Spatial control is added by PEX5-mediated peroxisomal import via a C-terminal PTS1 signal, which sequesters USP2 from cytosolic partners and limits its proapoptotic activity [#47]. USP2 is druggable: the selective inhibitor ML364 binds USP2 directly and triggers cyclin D1 degradation and cell-cycle arrest, and additional chemical probes (6-thioguanine, gambogic acid at Cys284) inhibit the enzyme through distinct allosteric and noncompetitive modes [#16, #18, #34].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established that the USP2 ortholog is a bona fide ubiquitin-specific isopeptidase that recycles ubiquitin rather than degrading conjugated substrates, defining its core biochemical activity.\",\n      \"evidence\": \"In vitro assays with purified recombinant chick UBP41 on 125I-ubiquitin and ubiquitin-fusion substrates, with active-site inhibitor controls\",\n      \"pmids\": [\"9325273\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify physiological substrates\", \"No structural basis for ubiquitin recognition\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linked USP2 catalytic activity to a cellular outcome by showing overexpression drives apoptosis dependent on the active site, while isoforms can oligomerize and localize to the cytoplasm.\",\n      \"evidence\": \"Overexpression of wild-type vs. catalytic-mutant UBP41 with apoptosis/flow assays; Co-IP and immunolocalization of mouse Usp2-45/Usp2-69\",\n      \"pmids\": [\"12566314\", \"14686789\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Proapoptotic substrate not identified\", \"Did not stabilize classical substrates p21/p27\", \"Physiological relevance of overexpression phenotype unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved how USP2 recognizes ubiquitin, showing two simultaneous ubiquitin interaction surfaces and ordered water-mediated contacts as a general USP recognition mode.\",\n      \"evidence\": \"X-ray crystallography of the USP2 catalytic domain–ubiquitin complex with mutant inhibition assays\",\n      \"pmids\": [\"16905103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic triad chemistry not yet functionally dissected\", \"Linkage specificity not addressed structurally\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Dissected the catalytic mechanism and substrate engagement kinetics, redefining triad assignments and revealing conformational rearrangement during diubiquitin cleavage.\",\n      \"evidence\": \"Site-directed mutagenesis with Ub-AMC and K48-diUb hydrolysis assays, MD simulation; stopped-flow single-turnover kinetics with inactive mutant controls\",\n      \"pmids\": [\"21542621\", \"23211065\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism inferred from minimal substrates, not full-length physiological substrates\", \"How conformational change selects chain linkage unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined isoform-specific substrate selectivity for membrane channels, showing the USP2-45 N-terminal tail positions the enzyme on Nedd4-2 to deubiquitylate ENaC, KCNQ1, and (later) Cav1.2 to control surface expression.\",\n      \"evidence\": \"Co-IP and GST pull-down of purified proteins, Xenopus oocyte and mammalian electrophysiology, surface biotinylation, with isoform-specific controls\",\n      \"pmids\": [\"21478478\", \"22024150\", \"25366495\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of N-terminal tail substrate positioning not solved\", \"Cav1.2 work is Medium confidence single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established USP2 as a circadian clock regulator that deubiquitinates PER1 and controls BMAL1 turnover, with knockout mice showing altered free-running period and light entrainment, later localized to the suprachiasmatic nucleus.\",\n      \"evidence\": \"Usp2 knockout (including SCN- and retina-specific conditional) mice, Co-IP, in vitro deubiquitination, locomotor rhythm recording, in vivo Per1/p-ERK induction\",\n      \"pmids\": [\"23213472\", \"21966515\", \"39967311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PER1 deubiquitination occurs without stability change — functional consequence unclear\", \"Ubiquitin chain linkage on clock substrates partly undefined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected USP2 to inflammatory and apoptotic signaling, showing it is required for TNF-α-induced NF-κB activation and stabilizes the proapoptotic factor tAIF against CHIP-mediated degradation.\",\n      \"evidence\": \"siRNA knockdown with IκB/NF-κB readouts and IL-8 ELISA; Co-IP, KD/OE, and cell-death assays for tAIF\",\n      \"pmids\": [\"21480224\", \"21293491\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct NF-κB-pathway substrate not defined in these studies\", \"Single-lab findings without reciprocal in vivo validation\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed spatial regulation of USP2 by PEX5-dependent peroxisomal import that sequesters the enzyme from cytosolic partners to limit proapoptotic activity, while early metabolic substrates (IDOL/LDLR, MR) were identified.\",\n      \"evidence\": \"PTS1-modified isoform overexpression, PEX5 KD/OE, FRAP imaging, apoptosis assays; Co-IP and functional uptake/reporter assays for IDOL-LDLR and MR\",\n      \"pmids\": [\"26484888\", \"26666640\", \"23548632\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Fraction of cellular USP2 that is peroxisomal under physiological conditions unknown\", \"IDOL/LDLR and MR studies single-lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Validated USP2 as a druggable target by identifying ML364, a direct-binding inhibitor that induces cyclin D1 degradation, cell-cycle arrest, and reduced HR repair.\",\n      \"evidence\": \"Fluorescent di-ubiquitin biochemical assay, microscale thermophoresis binding, Western blot, flow cytometry, HR repair assay\",\n      \"pmids\": [\"27681596\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cyclin D1 deubiquitination not biochemically reconstituted in this study\", \"Selectivity across DUB family not exhaustively profiled\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Expanded the chemical-probe toolkit and defined distinct inhibition modes, including noncompetitive slow-binding inhibition by 6-thioguanine and covalent allosteric inhibition at Cys284 by gambogic acid.\",\n      \"evidence\": \"Enzyme kinetics and X-ray crystallography (6-thioguanine); covalent binding characterization with functional KRAS readouts (gambogic acid)\",\n      \"pmids\": [\"29449607\", \"39807309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular selectivity of covalent probe not fully resolved\", \"Gambogic-acid study is Medium confidence single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established USP2 as a DNA-damage-response component recruited to double-strand breaks by ATM phosphorylation to stabilize NBS1 and the MRN complex, defining post-translational control of USP2 activity at chromatin.\",\n      \"evidence\": \"DUB screen, Co-IP, chromatin fractionation at DSBs, ATM inhibition, double siRNA knockdown with USP28, HR repair assay\",\n      \"pmids\": [\"36436562\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific ATM phosphosites mapped only as N-terminal residues\", \"Redundancy with USP28 complicates attribution\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Positioned USP2 as a regulator of tumor immune evasion by stabilizing PD-L1 (K48 chains at K270), CD47, and the p53-repressor VPRBP, nominating it as an immuno-oncology target sparing normal tissue.\",\n      \"evidence\": \"sgRNA screens, Co-IP, K48-linkage-specific ubiquitination assays, mutagenesis, phagocytosis assays, in vivo tumor models with immune profiling and anti-PD1 combination\",\n      \"pmids\": [\"37670038\", \"37024504\", \"40379682\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether one or multiple immune substrates dominate the therapeutic effect unresolved\", \"Most mechanistic detail from individual labs\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed metabolic deubiquitination programs and a novel activating PTM, showing USP2 stabilizes PPARγ at defined lysines to drive lipid accumulation, muscle insulin sensitivity, and thermogenesis, and is switched on by TGFβ1-driven Lys447 lactylation reversed by SIRT2.\",\n      \"evidence\": \"Site-specific K48 ubiquitination mapping, mutagenesis, global/tissue-specific KO mice, lactylation mapping and SIRT2 delactylation assays, fibrosis and metabolic models\",\n      \"pmids\": [\"40993213\", \"39874418\", \"40189098\", \"41310079\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Lactylation finding is recent single-lab\", \"How lactylation mechanistically activates catalysis not structurally defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified upstream control of USP2 levels by the SPOP E3 ligase and transcriptional regulators, closing feedback loops onto immune (CD47) and other substrate axes.\",\n      \"evidence\": \"Co-IP, in vitro deubiquitination, ubiquitination assays, flow cytometry, phagocytosis and syngeneic tumor models\",\n      \"pmids\": [\"41534899\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"SPOP degron on USP2 not finely mapped\", \"Single-lab study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How USP2 selects among its very large, context-dependent substrate repertoire and which interactions are direct versus scaffold-mediated remains the central open question.\",\n      \"evidence\": \"Many substrate claims rest on single-lab Co-IP plus ubiquitination assays without structural or reciprocal in vitro reconstitution\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structures of USP2 bound to full-length substrates\", \"Cell-type and isoform determinants of substrate choice undefined\", \"Several substrates (FOXC1, LEF1, JUP, MMP2, p53-K305R) supported by single Low-confidence studies\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 8, 16, 25, 35]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 10, 11]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [1, 11, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 47]},\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [47]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8, 9, 15]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [20]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [6, 7, 45]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 25, 27, 42]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [24]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [35, 36, 40, 51]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 16, 21, 25]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 4, 28]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [23, 37, 42]}\n    ],\n    \"complexes\": [\n      \"MRE11-RAD50-NBS1 (MRN) complex\",\n      \"CLOCK/BMAL1 circadian complex\"\n    ],\n    \"partners\": [\n      \"NEDD4-2\",\n      \"SKP2\",\n      \"PD-L1\",\n      \"CD47\",\n      \"PPARG\",\n      \"SMAD7\",\n      \"VPRBP\",\n      \"SPOP\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}