{"gene":"USP22","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2008,"finding":"USP22 is a catalytic subunit of the human SAGA (hSAGA) transcriptional cofactor complex where it deubiquitylates histone H2B. It is recruited to specific genes by activators such as Myc and is required for activated transcription and cell-cycle progression.","method":"Biochemical subunit identification, in vitro deubiquitylation assay, chromatin immunoprecipitation, RNAi loss-of-function","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (biochemical complex purification, in vitro enzymatic assay, ChIP, functional knockdown) in a single rigorous study; foundational finding widely replicated","pmids":["18206973"],"is_preprint":false},{"year":2008,"finding":"USP22 deubiquitylates histone H2A in addition to H2B, antagonizing Polycomb-catalyzed H2A ubiquitylation and thereby activating transcription.","method":"Biochemical substrate specificity assay with purified USP22","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assay demonstrating H2A deubiquitylation, single lab, single method","pmids":["18469533"],"is_preprint":false},{"year":2005,"finding":"USP22 (and its mouse homolog Usp22) encode ~525 aa proteins containing the conserved Cys, Asp(I), His, Asp/Asn(II) catalytic domains of the UBP deubiquitinase family and possess deubiquitinating enzyme activity in biochemical assay.","method":"Biochemical deubiquitinase activity assay, sequence/domain analysis","journal":"Gene expression patterns : GEP","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct enzymatic assay confirming DUB activity, single lab, single method","pmids":["16378762"],"is_preprint":false},{"year":2012,"finding":"USP22 interacts with and deubiquitinates SIRT1, removing polyubiquitin chains and stabilizing SIRT1 protein. USP22-mediated SIRT1 stabilization suppresses p53 acetylation and p53-dependent apoptosis. Genetic deletion of Usp22 in mice causes SIRT1 instability, elevated p53 activity, and early embryonic lethality.","method":"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, genetic knockout mouse model","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ubiquitination assay, in vivo knockout with defined molecular and developmental phenotype; multiple orthogonal methods","pmids":["22542455"],"is_preprint":false},{"year":2011,"finding":"USP22 deubiquitinates the transcriptional regulator FBP1 (FUSE-binding protein 1); increased FBP1 polyubiquitination upon USP22 ablation does not alter FBP1 stability but reduces its stable recruitment to target loci (including the p21 gene), thereby regulating p21 expression and cell proliferation.","method":"RNAi knockdown, ubiquitination assay, chromatin immunoprecipitation","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and ubiquitination assay with functional readout, single lab, two orthogonal methods","pmids":["21779003"],"is_preprint":false},{"year":2011,"finding":"USP22 knockdown leads to increased monoubiquitination of histone H2B and impaired transcriptional elongation at the STAT1 target gene IRF1; USP22 depletion also diminishes 3'-end cleavage/polyadenylation and impairs recruitment of polyadenylation factor CPSF73 and serine 2 phosphorylation of RNA Pol II CTD.","method":"RNAi knockdown, ChIP, quantitative RT-PCR, rescue by overexpression","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple chromatin and transcription assays, single lab","pmids":["22067483"],"is_preprint":false},{"year":2013,"finding":"SIRT1 interacts with USP22 via the ZnF-UBP domain of USP22; this interaction is disrupted by the SIRT1 H363Y inactivating mutation. USP22 is acetylated on multiple lysines; acetylation of K129 within the ZnF-UBP domain alters interaction of the DUB module with the core SAGA complex. SIRT1 recruited by USP22 deacetylates individual SAGA complex components.","method":"High-confidence interactome mapping (comparative Co-IP/MS), domain mutagenesis, acetylation mapping","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — quantitative interactome, domain mutagenesis, and acetylation assays; multiple orthogonal methods in single study","pmids":["23382074"],"is_preprint":false},{"year":2013,"finding":"USP22 is required for embryonic stem cell differentiation into all three germ layers. USP22 occupies the Sox2 promoter and hydrolyzes monoubiquitin from H2B, repressing Sox2 transcription; this repression is required for ESCs to transition from self-renewal to differentiation.","method":"Loss-of-function (knockdown/knockout in ESCs), chromatin immunoprecipitation, differentiation assays, H2Bub analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP showing USP22 occupancy at Sox2 promoter, H2Bub enzymatic assay at locus, functional differentiation phenotype; multiple methods single lab","pmids":["23760504"],"is_preprint":false},{"year":2016,"finding":"USP22 deubiquitylates and stabilizes the histone demethylase KDM1A (LSD1) after KDM1A is phosphorylated at Ser683 by GSK3β (primed by CK1α phosphorylation at Ser687). Phosphorylated KDM1A binds USP22, which removes ubiquitin and prevents its proteasomal degradation; this stabilization is required for H3K4 demethylation and repression of BMP2/CDKN1A/GATA6 to drive glioblastoma tumorigenesis.","method":"Co-immunoprecipitation, ubiquitination assay, phosphorylation mapping, mutagenesis, ChIP, xenograft models","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reciprocal Co-IP, in vitro ubiquitination/deubiquitination, mutagenesis of phosphorylation sites, ChIP, and in vivo models; multiple orthogonal methods in rigorous study","pmids":["27501329"],"is_preprint":false},{"year":2017,"finding":"USP22 deubiquitinates c-Myc, preventing its proteasomal degradation and increasing c-Myc protein levels in breast cancer cells; USP22 knockdown reduces c-Myc levels.","method":"Co-immunoprecipitation, ubiquitination assay, knockdown/overexpression","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitination assay, single lab, two orthogonal methods","pmids":["28160502"],"is_preprint":false},{"year":2018,"finding":"USP22 directly deubiquitylates cyclin D1 (CCND1), protecting it from proteasome-mediated degradation through a mechanism distinct from canonical T286 phosphorylation-dependent ubiquitylation. This non-transcriptional control of CCND1 is a key mechanism by which USP22 promotes G1 cell cycle progression in cancer cells.","method":"Ubiquitylation assay, protein stability assay (cycloheximide chase), cell cycle analysis, cancer cell knockdown/KO","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct deubiquitylation assay, protein stability assay, epistasis with cell cycle phenotype; multiple orthogonal methods, single lab","pmids":["30224477"],"is_preprint":false},{"year":2018,"finding":"Usp22 (the mouse homolog) promotes antibody class switch recombination and V(D)J recombination by facilitating classical non-homologous end joining (c-NHEJ) for DNA break repair; Usp22 ablation in B cells impairs γH2AX formation and c-NHEJ. CSR to IgA is more reliant on alternative end joining and is less affected by Usp22 loss.","method":"Conditional knockout in primary B cells, γH2AX analysis, CSR/V(D)J recombination assays, epistasis with DNA repair pathways","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with defined molecular and functional phenotype in primary cells, multiple DNA repair readouts; single lab but rigorous","pmids":["29520062"],"is_preprint":false},{"year":2018,"finding":"USP22 deficiency in the context of oncogenic Kras promotes AML transformation by blocking myeloid differentiation. USP22 functions as a deubiquitylase for PU.1, positively regulating PU.1 protein stability and the expression of PU.1 target genes; reconstitution of PU.1 in USP22-deficient Kras progenitors rescues differentiation.","method":"Conditional knockout mouse model, bone marrow transplantation, ubiquitylation assay, transcriptomic analysis, PU.1 rescue experiment","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout model, direct ubiquitylation assay for PU.1, epistasis rescue experiment; multiple methods, rigorous","pmids":["29844011"],"is_preprint":false},{"year":2019,"finding":"USP22 deubiquitinates and stabilizes HIF1α, promoting hypoxia-induced HCC stemness and glycolysis. In TP53 wild-type cells, HIF1α-induced TP53 suppresses USP22 upregulation; in TP53-mutant cells, USP22 and HIF1α form a positive feedback loop.","method":"Immunoprecipitation, ubiquitination assay, chromatin immunoprecipitation, loss/gain-of-function, in vivo mouse model","journal":"Gut","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, ChIP, and in vivo xenograft models; multiple orthogonal methods single lab","pmids":["31776228"],"is_preprint":false},{"year":2019,"finding":"Loss of USP22 in murine intestinal epithelium exacerbates Apc-mutant intestinal tumor burden and increases mTOR activity; USP22 depletion in human CRC cells increases tumorigenic properties reversed by mTOR inhibitor treatment, indicating USP22 exerts tumor-suppressive function in colorectal cancer via mTOR suppression.","method":"Tissue-specific conditional knockout mouse model, in vivo tumor assays, mTOR pathway analysis, pharmacological rescue","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo conditional KO with defined tumor phenotype, pharmacological epistasis; multiple methods single lab","pmids":["31527800"],"is_preprint":false},{"year":2020,"finding":"Cytoplasmic USP22 promotes nuclear translocation of IRF3 after viral infection by deubiquitinating and stabilizing the importin protein KPNA2. Viral infection induces USP22-IRF3 association in the cytoplasm in a KPNA2-dependent manner; USP22 or KPNA2 knockout impairs IRF3 nuclear translocation and type I IFN production. Reconstitution of KPNA2 into USP22-KO cells restores antiviral responses.","method":"Co-immunoprecipitation, ubiquitination assay, conditional knockout mice (Cre-ER and Lyz2-Cre), KPNA2 reconstitution epistasis, viral infection models","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple Co-IPs, direct ubiquitination assay, two in vivo KO mouse models, epistasis reconstitution; rigorous study with multiple orthogonal methods","pmids":["32130408"],"is_preprint":false},{"year":2020,"finding":"USP22 deubiquitinates PD-L1 directly, inhibiting its proteasomal degradation and stabilizing PD-L1 protein. USP22 also deubiquitinates CSN5 and stabilizes it; either USP22 or CSN5 facilitates the interaction of PD-L1 with the other. USP22 removes K6, K11, K27, K29, K33, and K63-linked ubiquitin chains from both CSN5 and PD-L1.","method":"Co-immunoprecipitation, ubiquitination assay specifying linkage types, protein half-life assay, flow cytometry","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitin linkage-specific assays, single lab, two orthogonal methods","pmids":["32665011"],"is_preprint":false},{"year":2020,"finding":"USP22 controls necroptosis by deubiquitinating RIPK3 at lysines 42, 351, and 518; mutation of RIPK3 K518 reduces necroptosis-associated ubiquitination and amplifies necrosome formation and necroptotic cell death. Loss of USP22 delays TNFα/Smac mimetic/zVAD-induced necroptosis without affecting NF-κB activation or extrinsic apoptosis.","method":"USP22 knockout in human tumor cell lines, ubiquitin remnant profiling (mass spectrometry), RIPK3 mutagenesis, cell death assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — ubiquitin remnant profiling by MS, site-directed mutagenesis of RIPK3, KO cell lines with defined death phenotype; multiple orthogonal methods single lab","pmids":["33369872"],"is_preprint":false},{"year":2020,"finding":"USP22 interacts with MED1 (Mediator complex subunit 1) in iNKT cells. USP22 does not deubiquitinate MED1 for its stabilization; instead, USP22 enhances MED1 transcriptional activity for IL-2Rβ and T-bet gene expression through deubiquitination of histone H2A (not H2B). USP22 deficiency blocks iNKT cell development at stage 1→2 transition in a cell-intrinsic manner.","method":"Co-immunoprecipitation, H2A ubiquitination assay, conditional knockout mouse model, iNKT developmental analysis","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP, direct H2A deubiquitination assay distinguishing H2A from H2B substrate specificity, in vivo conditional KO; multiple methods single lab","pmids":["32069354"],"is_preprint":false},{"year":2019,"finding":"USP22 loss in murine placental endothelial cells and pericytes causes embryonic lethality due to defects in extra-embryonic placental vasculature; USP22 deletion hinders TGFβ and receptor tyrosine kinase signaling cascades with detrimental effects on cell survival, differentiation, and vessel formation.","method":"Conditional knockout mouse model, embryonic stem cell-derived endothelial/pericyte differentiation, signaling pathway analysis","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo conditional KO with placental/vascular phenotype and signaling analysis; single lab","pmids":["30718289"],"is_preprint":false},{"year":2015,"finding":"Global reduction of Usp22 in mice impairs lineage specification in the small intestine and brain, with altered frequencies of differentiated cells, while H2B and H2Bub1 levels remain constant, indicating USP22 controls differentiation through mechanisms beyond bulk H2Bub1 levels.","method":"Usp22 hypomorphic (lacZ knock-in) mouse model, histological analysis, H2Bub1 Western blot","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with tissue-specific differentiation phenotype; single lab","pmids":["26431380"],"is_preprint":false},{"year":2022,"finding":"USP22 directly interacts with, deubiquitinates (K48-linked), and stabilizes PPARγ, which in turn increases ACC and ACLY expression, promoting de novo fatty acid synthesis and HCC tumorigenesis.","method":"Co-immunoprecipitation, ubiquitination assay (K48-linkage specific), in vivo tumorigenesis experiments with PPARγ/ACLY/ACC inhibition","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, linkage-specific ubiquitination assay, in vivo epistasis; multiple orthogonal methods single lab","pmids":["35449157"],"is_preprint":false},{"year":2022,"finding":"USP22 stabilizes ATG5 by decreasing K27- and K48-linked ubiquitination at Lys118, thereby promoting ATG5-mediated autophagy, which in turn degrades NLRP3 and suppresses NLRP3 inflammasome activation. USP22 deficiency increases alum-induced peritonitis and LPS-induced systemic inflammation in vivo.","method":"Co-immunoprecipitation, site-specific ubiquitination assay (K27/K48 linkage, Lys118 mutagenesis), autophagy assays, in vivo USP22 silencing models","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — site-specific mutagenesis of ubiquitination site, linkage-specific assays, in vivo inflammasome phenotype; multiple orthogonal methods single lab","pmids":["35900990"],"is_preprint":false},{"year":2022,"finding":"USP22 controls basal and cGAMP-induced STING activation in human intestinal epithelial cells; loss of USP22 upregulates IFN-λ secretion and ISGs through STING, and USP22-deficient cells are protected against SARS-CoV-2 infection in a STING-dependent manner.","method":"USP22-deficient human intestinal epithelial cell lines, STING pathway analysis, SARS-CoV-2 infection assays, epistasis with STING inhibition","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO cells with IFN pathway and antiviral phenotype, STING epistasis; single lab","pmids":["35933402"],"is_preprint":false},{"year":2019,"finding":"USP22 interacts with and deubiquitinates BRCA2/PALB2, stabilizing their protein levels; this interaction occurs through the C-terminal WD40 domain of PALB2 and stimulates USP22 catalytic activity in vitro. USP22 is necessary for BRCA2, PALB2, and Rad51 recruitment to DNA double-strand breaks, facilitating homologous recombination repair.","method":"Co-immunoprecipitation, in vitro catalytic activity assay, DNA damage foci analysis, HR reporter assay","journal":"Molecular cancer research : MCR","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro catalytic stimulation assay, Co-IP, DNA repair functional assay; single lab, multiple methods","pmids":["31685642"],"is_preprint":false},{"year":2019,"finding":"USP22 depletion in prostate cancer cells sensitizes them to genotoxic insult; ubiquitylome analysis identified XPC (nucleotide excision repair protein) as a USP22 substrate that undergoes deubiquitylation by USP22 to promote survival after DNA damage.","method":"Ubiquitylome profiling, USP22 KO/KD, genotoxic sensitivity assays, novel USP22-overexpressing murine model","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitylome-wide profiling plus functional DNA damage assay; single lab","pmids":["31740444"],"is_preprint":false},{"year":2014,"finding":"USP22 regulates androgen receptor (AR) accumulation and signaling; it is sufficient to reprogram AR function and induce transition to therapeutic resistance in prostate cancer xenograft models.","method":"Xenograft models, USP22 modulation (overexpression/depletion), AR signaling pathway analysis","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo xenograft with AR pathway analysis, functional phenotype; single lab","pmids":["24197134"],"is_preprint":false},{"year":2015,"finding":"USP22 directly interacts with and deubiquitinates COX-2, modulating COX-2 stability; USP22 silencing decreases COX-2 protein half-life and inhibits lung carcinoma cell proliferation.","method":"Co-immunoprecipitation, ubiquitination assay, cycloheximide-chase protein stability assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, and protein stability assay; single lab, multiple methods","pmids":["25817787"],"is_preprint":false},{"year":2018,"finding":"USP22 deubiquitinates EGFR on late endosomes, preventing ubiquitin-mediated EGFR degradation and enhancing EGFR recycling after EGF stimulation, thereby sustaining EGFR downstream signaling (STAT3, AKT/mTOR, MEK/ERK) and conferring resistance to EGFR-TKIs.","method":"Co-immunoprecipitation, ubiquitination assay, endosomal localization, EGFR recycling assay, in vitro and in vivo knockdown","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, subcellular localization, recycling assay; single lab","pmids":["29981430"],"is_preprint":false},{"year":2020,"finding":"USP22 positively modulates ERα stability and transactivation via its deubiquitinase activity; USP22 is recruited together with ERα to cis-regulatory elements of ERα target genes, and USP22 deubiquitinase activity is required for maintaining ERα stability and conferring endocrine resistance.","method":"Co-immunoprecipitation, ChIP, ubiquitination assay, mutagenesis (deubiquitinase-dead), overexpression/knockdown","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, ChIP, deubiquitinase-dead mutant; single lab, multiple methods","pmids":["32494025"],"is_preprint":false},{"year":2014,"finding":"USP22 promotes EMT in pancreatic cancer cells through the FAK signaling pathway, promoting Ezrin redistribution/phosphorylation, cytoskeletal remodeling, and upregulation of EMT transcription factors Snail and ZEB1; blockade of USP22 reverses these effects.","method":"Overexpression/knockdown in PANC-1 cells, phosphorylation analysis, immunofluorescence, invasion assay","journal":"Oncology reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional phenotype with pathway placement but no direct substrate deubiquitination assay; single lab, single cell line","pmids":["25070659"],"is_preprint":false},{"year":2014,"finding":"USP22 interacts with NFATc2 and deubiquitinates it, stabilizing NFATc2 protein levels; USP22 depletion in T cells reduces IL-2 expression, and this stabilization requires USP22 deubiquitinase activity.","method":"Co-immunoprecipitation, ubiquitination assay, knockdown in T cells, IL-2 expression analysis","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and direct ubiquitination assay with functional T cell readout; single lab","pmids":["24561192"],"is_preprint":false},{"year":2014,"finding":"USP22 overexpression downregulates STAT3 acetylation by deubiquitinating and stabilizing SIRT1; USP22, SIRT1, and STAT3 form a single protein complex. USP22 knockdown destabilizes SIRT1 and elevates STAT3 acetylation, with downstream reduction of MMP9 and TWIST expression.","method":"Co-immunoprecipitation, ubiquitination assay, Western blot for acetylated STAT3","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP confirming ternary complex, ubiquitination/acetylation assays; single lab","pmids":["24969755"],"is_preprint":false},{"year":2015,"finding":"USP22 deubiquitinase activity (demonstrated with C185S and Y513C mutants) is necessary for cell cycle regulation in HeLa cells and is required for maintaining BMI-1, c-Myc, cyclin D2, and p53 levels.","method":"Active-site mutagenesis (C185S catalytic dead, Y513C activity-reduced), cell cycle analysis, Western blot","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — active-site mutagenesis directly linking catalytic activity to cellular phenotype; single lab, single cell line","pmids":["26143114"],"is_preprint":false},{"year":2017,"finding":"USP22 stabilizes BMI1 protein in gastric cancer cells through deubiquitination; USP22 knockdown suppresses cancer stem cell sphere formation, reduces CD133/SOX2/OCT4/NANOG expression, and these effects are rescued by TAT-BMI1 protein reconstitution.","method":"Knockdown/overexpression, protein stability assay, sphere formation assay, BMI1 reconstitution rescue","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis rescue with BMI1, protein stability assay; single lab","pmids":["28415621"],"is_preprint":false},{"year":2021,"finding":"USP22 deubiquitinates STAT1 and improves its stability in melanoma cells; USP22 deficiency impairs sensitivity to IFNγ-JAK1-STAT1 signaling, reducing T cell-mediated killing; USP22 overexpression enhances tumor cell sensitivity to T cell killing.","method":"Co-immunoprecipitation, ubiquitination assay, CRISPR-Cas9 KO screen, in vitro and in vivo T cell killing assays","journal":"Molecular therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen followed by Co-IP, ubiquitination assay, and functional T cell assays; single lab","pmids":["33601053"],"is_preprint":false},{"year":2021,"finding":"USP22 promotes HER2-driven mammary carcinoma by stabilizing the ER chaperone HSPA5, actively suppressing unfolded protein response (UPR) induction; USP22 loss renders tumor cells more sensitive to apoptosis and ER-stress targeting therapies.","method":"Genetic mouse models, human HER2+ cell lines, transcriptome-wide gene expression analysis, HSPA5 stability assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic mouse models plus transcriptomic identification of UPR pathway; HSPA5 stabilization assay; single lab","pmids":["34007022"],"is_preprint":false},{"year":2021,"finding":"USP22 deubiquitinates and stabilizes E2F6, which transcriptionally represses the phosphatase DUSP1, leading to AKT activation in HCC cells.","method":"Co-immunoprecipitation, ubiquitination assay, luciferase reporter, knockdown epistasis","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, transcriptional reporter; single lab, multiple methods","pmids":["34339800"],"is_preprint":false},{"year":2021,"finding":"USP22 deubiquitinates and stabilizes PTEN in pancreatic cancer cells; USP22-mediated PTEN stabilization induces p21 expression through PTEN interaction with ANKHD1, inhibiting ANKHD1 binding to the p21 promoter.","method":"Co-immunoprecipitation, ubiquitination assay, ChIP, overexpression/knockdown","journal":"Molecular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitination assay, functional epistasis; single lab","pmids":["34743406"],"is_preprint":false},{"year":2023,"finding":"USP22 deubiquitinates and stabilizes the EMT transcription factor Snail1 in renal tubular epithelial cells, depending on its deubiquitinase activity, thereby promoting EMT and diabetic renal tubulointerstitial fibrosis.","method":"Co-immunoprecipitation, ubiquitination assay, deubiquitinase activity mutant, in vivo db/db mouse model","journal":"European journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, in vivo model; single lab, multiple methods","pmids":["37001578"],"is_preprint":false},{"year":2023,"finding":"USP22 acts as a co-activator of VEGFA transcription by maintaining ZEB1 stability via its deubiquitinase activity; USP22 is recruited to ZEB1-binding elements on the VEGFA promoter and alters H2Bub1 levels to enhance ZEB1-mediated VEGFA transcription.","method":"Co-immunoprecipitation, ubiquitination assay, ChIP, H2Bub1 chromatin analysis, knockdown/overexpression","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, ChIP at VEGFA promoter; single lab, multiple methods","pmids":["36906615"],"is_preprint":false},{"year":2022,"finding":"PRDM1 enhances USP22 transcription, and USP22 in turn reduces SPI1 (PU.1) protein degradation through deubiquitination, which enhances PD-L1 transcription in HCC cells, dampening antitumor immunity.","method":"Co-immunoprecipitation, ubiquitination assay, ChIP, gain-of-function in vivo models","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitination assay for SPI1 deubiquitination, in vivo immune phenotype; single lab","pmids":["36509766"],"is_preprint":false},{"year":2018,"finding":"Gα12 stabilizes SIRT1 protein through transcriptional induction of USP22 via HIF-1α; USP22 in turn deubiquitinates and stabilizes SIRT1 to regulate mitochondrial respiration and hepatic lipid metabolism.","method":"cDNA microarray, Gna12-KO mouse model, lentiviral overexpression, protein stability assay","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO model plus lentiviral rescue, identification of USP22 as transcriptional target of Gα12/HIF-1α; single lab","pmids":["30300140"],"is_preprint":false},{"year":2015,"finding":"USP22 interacts with RCAN1 (regulator of calcineurin 1) and promotes RCAN1 deubiquitination and protein stabilization, antagonizing FBW7, NEDD4-2, and β-TrCP E3 ligase actions on RCAN1. IFN-α treatment dissociates RCAN1 from USP22, triggering RCAN1 ubiquitination and degradation.","method":"Co-immunoprecipitation, ubiquitination assay, E3 ligase competition assay, IFN-α treatment","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, multiple E3 ligase competition; single lab","pmids":["25546086"],"is_preprint":false},{"year":2024,"finding":"Phosphorylated MYH9 (Ser1943) recruits USP22 to deubiquitinate and stabilize HIF-1α in lenvatinib-resistant HCC, promoting cancer stemness. A CK2 inhibitor or USP22 inhibitor effectively reversed lenvatinib resistance in vivo and in vitro.","method":"Immunoprecipitation, mass spectrometry, ubiquitination assay, RNA-sequencing, patient-derived xenograft models","journal":"Signal transduction and targeted therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identifying the interaction, ubiquitination assay for HIF-1α, in vivo PDX model; single lab","pmids":["39300073"],"is_preprint":false},{"year":2022,"finding":"EZH2 inhibition transcriptionally upregulates USP22, which in turn stabilizes PD-L1 via deubiquitination in colorectal cancer cells. Knockdown of USP22 enhances therapeutic efficacy of EZH2 inhibitors.","method":"USP22 knockdown/overexpression, ubiquitination assay, protein stability assay, in vivo tumor models","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination and stability assays with in vivo epistasis; single lab","pmids":["38520088"],"is_preprint":false},{"year":2024,"finding":"The small molecule demethylzeylasteral (Dem) binds USP22 and promotes its degradation, resulting in increased ubiquitination and proteasomal degradation of PD-L1; structure-based analysis identified Leu475 and Arg419 as crucial residues for USP22 inhibitor binding.","method":"Structure-based virtual screening, binding assay, ubiquitination assay, in vivo syngeneic tumor model, molecular dynamics simulation","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — direct binding assay, ubiquitination assay, residue identification by MD; single lab","pmids":["39525573"],"is_preprint":false},{"year":2023,"finding":"Structure-based inhibitor discovery identified Rottlerin and Morusin as selective USP22 inhibitors (IC50 2.53 and 8.29 μM, respectively); treatment with these compounds increases H2A and H2B monoubiquitination and reduces Sirt1 and PD-L1 protein levels, consistent with USP22 substrate specificity. Key binding residues Leu475 (conserved) and Arg419 (non-conserved) are crucial for inhibitory function.","method":"Structure-based virtual screening, in vitro USP22 enzyme assay, cellular ubiquitination assay, in vivo syngeneic tumor model, molecular dynamics/binding free energy calculation","journal":"Bioorganic chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with selectivity profiling, cellular substrate validation, and structural modeling; single lab","pmids":["37769523"],"is_preprint":false},{"year":2012,"finding":"The USP22 promoter basal activity is controlled by the -210 to -7 region; an Sp1 binding site immediately upstream of the transcriptional start site (-13 to -7) acts as a repressor—Sp1 binding suppresses USP22 transcription, and Sp1 knockdown or inhibition increases USP22 mRNA levels.","method":"5'-RACE, promoter deletion analysis, mutagenesis, Sp1 ChIP, mithramycin A treatment, Sp1 overexpression/knockdown","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter deletion mapping, Sp1 mutagenesis, ChIP, pharmacological and genetic Sp1 manipulation; single lab","pmids":["23300749"],"is_preprint":false},{"year":2020,"finding":"USP22 depletion in pancreatic tumor cells reduces myeloid cell infiltration and promotes T cell and NK cell infiltration, leading to improved response to combination immunotherapy; USP22 exerts its effects on the tumor immune microenvironment through its association with the deubiquitylase module of the SAGA/STAGA complex and reshaping the cancer cell transcriptome.","method":"USP22 deletion in pancreatic tumor cells, immune cell profiling, immunotherapy response assay, SAGA complex association analysis","journal":"Cancer immunology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo deletion model with immune microenvironment phenotype, SAGA association; single lab","pmids":["31871120"],"is_preprint":false},{"year":2021,"finding":"USP22 suppresses SPARC expression in intestinal epithelial cells by affecting H3K27ac and H2Bub1 occupancy on the SPARC gene; Usp22 intestine-specific deletion upregulates SPARC and increases colitis severity and inflammation-associated colorectal tumor growth.","method":"Intestine-specific conditional Usp22 KO mouse, DSS colitis model, chromatin immunoprecipitation (H3K27ac, H2Bub1), gene expression analysis","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO in vivo with ChIP evidence at SPARC locus; single lab","pmids":["33920268"],"is_preprint":false},{"year":2022,"finding":"USP22 deubiquitinates and stabilizes FASN; in p53 wild-type CRC cells, H2O2-induced p53 represses USP22 transcription, reducing FASN stability and fatty acid synthesis. In p53-deficient cells, this repression is relieved, leading to FASN stabilization and increased lipid synthesis.","method":"Co-immunoprecipitation, ubiquitination assay, FASN protein stability assay, p53 transcriptional repression of USP22, lipogenesis assay","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination/stability assays, p53-USP22 transcriptional epistasis; single lab","pmids":["36333288"],"is_preprint":false},{"year":2021,"finding":"USP22 deubiquitinates and stabilizes LSD1 (KDM1A) in osteosarcoma; USP22 knockdown leads to ubiquitination and degradation of LSD1, reduced p21 repression, and inhibited cell proliferation/invasion. miR-140 suppresses this axis by targeting USP22.","method":"Knockdown/overexpression, ubiquitination assay, protein stability assay, in vivo xenograft","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination and stability assays for LSD1 substrate, in vivo xenograft; single lab","pmids":["33868787"],"is_preprint":false}],"current_model":"USP22 is a catalytic deubiquitylase subunit of the mammalian SAGA transcriptional co-activator complex that removes monoubiquitin from histones H2B and H2A to regulate transcription elongation, 3'-end processing, and epigenetic gene control; beyond histones, USP22 stabilizes a broad array of non-histone substrates—including SIRT1, HIF1α, PPARγ, CCND1, c-Myc, KDM1A/LSD1, PU.1, KPNA2, ATG5, RIPK3, PD-L1, ERα, EGFR, PTEN, STAT1, NFATc2, ZEB1, Snail1, FASN, and others—by deubiquitinating them and preventing proteasomal degradation, thereby acting as a multi-substrate DUB that integrates transcriptional, cell-cycle, apoptotic, immune, metabolic, and DNA-repair programs in both normal development and cancer."},"narrative":{"mechanistic_narrative":"USP22 is the catalytic deubiquitylase subunit of the human SAGA transcriptional coactivator complex, where it hydrolyzes monoubiquitin from histones H2B and H2A to control activated transcription, transcriptional elongation, mRNA 3'-end processing, and cell-cycle progression [PMID:18206973, PMID:18469533, PMID:22067483]. Within SAGA, USP22 is recruited to target genes by activators such as Myc and engages SIRT1 through its ZnF-UBP domain; the recruited SIRT1 deacetylates SAGA components, and reciprocal acetylation of USP22 modulates how the deubiquitinase module docks onto the core complex [PMID:18206973, PMID:23382074]. Through this chromatin activity, USP22 governs developmental programs—it is required for embryonic stem cell exit from self-renewal by hydrolyzing H2Bub at the Sox2 promoter, and Usp22 loss disrupts lineage specification in intestine and brain independent of bulk H2Bub1 levels [PMID:23760504, PMID:26431380]. Beyond histones, USP22 is a multi-substrate deubiquitinase that stabilizes diverse non-histone proteins by removing degradative ubiquitin chains: it stabilizes SIRT1 to suppress p53-dependent apoptosis, an activity essential for embryonic viability [PMID:22542455], and the catalytic-site requirement for these functions is established by active-site mutants (C185S, Y513C) that abolish maintenance of substrate levels and cell-cycle control [PMID:26143114]. Its substrate repertoire spans transcription factors and chromatin regulators (KDM1A/LSD1, c-Myc, PU.1, BMI1, E2F6, ZEB1, Snail1, PPARγ) [PMID:27501329, PMID:28160502, PMID:29844011, PMID:28415621, PMID:34339800, PMID:36906615, PMID:37001578, PMID:35449157], cell-cycle and growth-control proteins (CCND1, PTEN) [PMID:30224477, PMID:34743406], metabolic enzymes (FASN) [PMID:36333288], and receptors/signaling nodes (EGFR deubiquitinated on late endosomes, ERα, HIF1α) [PMID:29981430, PMID:32494025, PMID:31776228]. In immunity and cell death, USP22 stabilizes KPNA2 to drive IRF3 nuclear translocation and type I interferon production, deubiquitinates RIPK3 to restrain necroptosis, stabilizes ATG5 to promote autophagic suppression of the NLRP3 inflammasome, stabilizes STAT1 to sustain IFNγ sensitivity, and stabilizes PD-L1 to dampen antitumor immunity [PMID:32130408, PMID:33369872, PMID:35900990, PMID:33601053, PMID:32665011]. USP22 also promotes DNA double-strand break repair, facilitating BRCA2/PALB2/Rad51 recruitment for homologous recombination and supporting c-NHEJ during antibody class switch and V(D)J recombination [PMID:31685642, PMID:29520062]. Across cancers USP22 exhibits context-dependent oncogenic and tumor-suppressive roles, suppressing mTOR signaling in the intestine while promoting proliferation, stemness, metabolic reprogramming, and therapy resistance elsewhere [PMID:31527800, PMID:30224477, PMID:31776228]. USP22 transcription is itself regulated—repressed by an Sp1 site at its promoter and by p53—and small-molecule inhibitors (Rottlerin, Morusin, demethylzeylasteral) targeting residues including Leu475 and Arg419 reduce its substrate stabilization [PMID:23300749, PMID:36333288, PMID:37769523, PMID:39525573].","teleology":[{"year":2005,"claim":"Established that USP22 is a bona fide enzyme, defining it as a UBP-family deubiquitinase with the conserved catalytic residues required for ubiquitin hydrolysis.","evidence":"Sequence/domain analysis and biochemical DUB activity assay on the ~525 aa protein and its mouse homolog","pmids":["16378762"],"confidence":"Medium","gaps":["No physiological substrate identified at this stage","No structural model of the catalytic domain"]},{"year":2008,"claim":"Placed USP22 within the SAGA coactivator complex and identified histones as its substrates, explaining how a DUB controls transcription and cell-cycle progression.","evidence":"Biochemical subunit purification, in vitro H2B and H2A deubiquitylation, ChIP, and RNAi loss-of-function","pmids":["18206973","18469533"],"confidence":"High","gaps":["Relative contribution of H2B vs H2A deubiquitylation to specific genes unresolved","Mechanism of activator-directed recruitment beyond Myc not detailed"]},{"year":2011,"claim":"Extended USP22's chromatin role beyond histone removal to transcriptional elongation, 3'-end processing, and recruitment/stable loading of regulatory factors at target loci.","evidence":"RNAi knockdown, ChIP, qRT-PCR, and ubiquitination assays at IRF1 and p21 loci (FBP1)","pmids":["22067483","21779003"],"confidence":"Medium","gaps":["Direct link between H2Bub and CPSF73/Pol II Ser2-P recruitment mechanistic detail incomplete","Generality across the genome not established"]},{"year":2012,"claim":"Demonstrated USP22 acts on non-histone substrates in vivo, showing SIRT1 stabilization suppresses p53 and is essential for embryonic viability—reframing USP22 as a multi-substrate DUB.","evidence":"Reciprocal Co-IP, ubiquitination assay, RNAi, and Usp22 knockout mouse","pmids":["22542455"],"confidence":"High","gaps":["Whether SIRT1 stabilization is SAGA-dependent or cytoplasmic not fully resolved","Full breadth of non-histone substrate spectrum unknown at this point"]},{"year":2013,"claim":"Defined the structural basis of the USP22–SIRT1 interaction and showed reciprocal post-translational crosstalk (USP22 acetylation, SIRT1 deacetylation of SAGA) regulating DUB module assembly.","evidence":"Comparative Co-IP/MS interactome, ZnF-UBP domain mutagenesis, acetylation site mapping","pmids":["23382074"],"confidence":"High","gaps":["Enzyme responsible for USP22 acetylation not identified","Functional consequence of K129 acetylation on substrate selection not quantified"]},{"year":2013,"claim":"Connected USP22 chromatin activity to a developmental decision, showing H2Bub removal at Sox2 represses pluripotency and licenses ESC differentiation.","evidence":"Knockdown/knockout in ESCs, ChIP, locus H2Bub analysis, three-germ-layer differentiation assays","pmids":["23760504"],"confidence":"High","gaps":["Whether other pluripotency loci are co-regulated not addressed","Recruitment determinants at the Sox2 promoter undefined"]},{"year":2015,"claim":"Provided genetic active-site evidence directly tying USP22 catalytic activity to maintenance of cell-cycle regulators and demonstrated tissue-level differentiation roles uncoupled from bulk H2Bub1.","evidence":"C185S/Y513C active-site mutants with cell-cycle readout; Usp22 hypomorphic mouse with intestine/brain phenotypes and unchanged global H2Bub1","pmids":["26143114","26431380"],"confidence":"Medium","gaps":["Locus-specific vs global H2Bub effects not reconciled","Which substrates dominate the differentiation phenotype unclear"]},{"year":2018,"claim":"Expanded USP22 into receptor and endosomal signaling and direct cell-cycle control, deubiquitinating EGFR on late endosomes to sustain signaling and stabilizing cyclin D1 independent of T286 phosphorylation.","evidence":"Co-IP, ubiquitination assays, endosomal localization, recycling assay, cycloheximide chase, cell-cycle analysis","pmids":["29981430","30224477"],"confidence":"High","gaps":["How a SAGA subunit accesses late endosomal EGFR mechanistically unexplained","Cytoplasmic vs nuclear pools of USP22 not quantified"]},{"year":2018,"claim":"Established USP22's roles in DNA repair and hematopoietic differentiation through PU.1 stabilization and c-NHEJ facilitation, with in vivo genetic models.","evidence":"Conditional B-cell and Kras-progenitor knockouts, ubiquitylation assays, γH2AX/CSR/V(D)J readouts, PU.1 rescue","pmids":["29520062","29844011"],"confidence":"High","gaps":["Direct DNA-repair substrate(s) underlying c-NHEJ effect not all defined","Tissue-context determinants of oncogenic vs differentiation roles unclear"]},{"year":2019,"claim":"Revealed USP22's context-dependent tumor biology—tumor-suppressive via mTOR restraint in intestine versus oncogenic stabilization of HIF1α—and demonstrated direct roles in homologous recombination repair.","evidence":"Tissue-specific conditional KO mice, mTOR pharmacological rescue, ubiquitination/ChIP assays for HIF1α, BRCA2/PALB2/Rad51 foci and HR reporter assays","pmids":["31527800","31776228","31685642"],"confidence":"High","gaps":["Molecular determinant switching USP22 between suppressor and oncogene unknown","Whether HR function requires SAGA or is chromatin-independent unresolved"]},{"year":2020,"claim":"Positioned USP22 as a central regulator of innate immunity and cell death by stabilizing KPNA2 (IRF3 translocation/IFN-I), restraining RIPK3-driven necroptosis, and stabilizing PD-L1 and the iNKT transcriptional program.","evidence":"Co-IP, linkage-specific and remnant-profiling ubiquitination assays, RIPK3 site mutagenesis, conditional KO mice, viral and necroptosis models","pmids":["32130408","33369872","32665011","32069354"],"confidence":"High","gaps":["How USP22 selects K-linkage-specific chains on different substrates unclear","Cytoplasmic targeting signals for these substrates undefined"]},{"year":2022,"claim":"Linked USP22 to metabolic and inflammatory homeostasis through site-specific stabilization of PPARγ, FASN, and ATG5, the latter coupling autophagy to NLRP3 inflammasome suppression.","evidence":"Co-IP, linkage- and lysine-site-specific ubiquitination assays, autophagy/lipogenesis assays, in vivo inflammation and tumor models","pmids":["35449157","36333288","35900990"],"confidence":"High","gaps":["Determinants of site-specific deubiquitination (e.g. ATG5 Lys118) not structurally explained","Crosstalk between metabolic and immune substrates in vivo not integrated"]},{"year":2024,"claim":"Advanced USP22 as a druggable target, identifying selective small-molecule inhibitors and binding residues whose engagement reduces stabilization of substrates including PD-L1 and SIRT1.","evidence":"Structure-based virtual screening, in vitro enzyme assays, binding/MD studies, cellular ubiquitination assays, syngeneic and PDX tumor models","pmids":["37769523","39525573","39300073"],"confidence":"Medium","gaps":["No experimentally determined high-resolution USP22 structure reported in the corpus","Selectivity over other USP-family DUBs only partially profiled"]},{"year":null,"claim":"It remains unresolved how a single SAGA-associated deubiquitinase achieves substrate selectivity across dozens of histone and non-histone targets and how cellular context dictates its opposing tumor-suppressive versus oncogenic outputs.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model for substrate/linkage discrimination","No high-resolution structure of full-length USP22 or its substrate complexes","Determinants of nuclear/SAGA vs cytoplasmic substrate engagement undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,8,10,16,17,22,24]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[2,0,33]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,5,7,40,49]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,7,5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[15,3]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[28]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1,7,50]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,5,7,40]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,1,50]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[10,33]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[24,11,25]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[15,16,35,22,41]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,17]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[21,51,13]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[13,14,26,28,44]}],"complexes":["SAGA/STAGA deubiquitinase module"],"partners":["SIRT1","KDM1A","HIF1A","KPNA2","RIPK3","PPARG","BRCA2","PALB2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UPT9","full_name":"Ubiquitin carboxyl-terminal hydrolase 22","aliases":["Deubiquitinating enzyme 22","Ubiquitin thioesterase 22","Ubiquitin-specific-processing protease 22"],"length_aa":525,"mass_kda":60.0,"function":"Deubiquitinase that plays a role in several cellular processes including transcriptional regulation, cell cycle progression or innate immunity. As part of the transcription regulatory histone acetylation (HAT) complex SAGA, catalyzes the deubiquitination of both histones H2A and H2B, thereby acting as a transcriptional coactivator (PubMed:18206972, PubMed:18206973, PubMed:18469533). Recruited to specific gene promoters by activators such as MYC, where it is required for transcription. Facilitates cell-cycle progression by stabilizing CCNB1 and antagonizing its proteasome-mediated degradation in a cell cycle-specific manner (PubMed:27030811). Modulates cell cycle progression and apoptosis also by antagonizing TP53 transcriptional activation through deacetylase SIRT1 stabilization (PubMed:22542455). Plays multiple roles in immunity and inflammation. Participates in antiviral response by deubiquitinating the importin KPNA2, leading to IRF3 nuclear translocation and subsequent type I interferon production (PubMed:32130408). Acts as a central regulator of type III IFN signaling by negatively regulating STING1 activation and ubiquitination (PubMed:35933402). Inhibits NLRP3 inflammasome activation by promoting NLRP3 degradation through ATG5-dependent autophagy (By similarity). Deubiquitinates CD274 to induce its stabilization and thereby participates in maintenance of immune tolerance to self (PubMed:31399419). Controls necroptotic cell death by regulating RIPK3 phosphorylation and ubiquitination (PubMed:33369872). During bacterial infection, promotes pro-inflammatory response by targeting TRAF6 and removing its 'Lys-48'-linked polyubiquitination (By similarity)","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9UPT9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/USP22","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000124422","cell_line_id":"CID001774","localizations":[{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"ENY2","stoichiometry":10.0},{"gene":"ACTR3","stoichiometry":10.0},{"gene":"ACTR2","stoichiometry":10.0},{"gene":"ARPC1A","stoichiometry":10.0},{"gene":"ARPC2","stoichiometry":10.0},{"gene":"SUPT7L","stoichiometry":10.0},{"gene":"FAM50A","stoichiometry":4.0},{"gene":"TAF9B","stoichiometry":4.0},{"gene":"CCDC101","stoichiometry":4.0},{"gene":"ARPC5","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/target/CID001774","total_profiled":1310},"omim":[{"mim_id":"619015","title":"ENY2 TRANSCRIPTION AND EXPORT COMPLEX 2 SUBUNIT; ENY2","url":"https://www.omim.org/entry/619015"},{"mim_id":"619010","title":"ATXN7-LIKE 3; ATXN7L3","url":"https://www.omim.org/entry/619010"},{"mim_id":"612116","title":"UBIQUITIN-SPECIFIC PROTEASE 22; USP22","url":"https://www.omim.org/entry/612116"},{"mim_id":"607699","title":"RING FINGER PROTEIN 20; RNF20","url":"https://www.omim.org/entry/607699"},{"mim_id":"607640","title":"ATAXIN 7; ATXN7","url":"https://www.omim.org/entry/607640"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/USP22"},"hgnc":{"alias_symbol":["KIAA1063"],"prev_symbol":["USP3L"]},"alphafold":{"accession":"Q9UPT9","domains":[{"cath_id":"3.30.40.10","chopping":"26-140","consensus_level":"high","plddt":89.9016,"start":26,"end":140},{"cath_id":"-","chopping":"185-280","consensus_level":"medium","plddt":90.9366,"start":185,"end":280}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UPT9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UPT9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UPT9-F1-predicted_aligned_error_v6.png","plddt_mean":83.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=USP22","jax_strain_url":"https://www.jax.org/strain/search?query=USP22"},"sequence":{"accession":"Q9UPT9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UPT9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UPT9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UPT9"}},"corpus_meta":[{"pmid":"18206973","id":"PMC_18206973","title":"The putative cancer stem cell marker USP22 is a subunit of the human SAGA complex required for activated transcription and cell-cycle progression.","date":"2008","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/18206973","citation_count":359,"is_preprint":false},{"pmid":"22542455","id":"PMC_22542455","title":"USP22 antagonizes p53 transcriptional activation by deubiquitinating Sirt1 to suppress cell apoptosis and is required for mouse embryonic development.","date":"2012","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/22542455","citation_count":265,"is_preprint":false},{"pmid":"33192549","id":"PMC_33192549","title":"USP22 Protects Against Myocardial Ischemia-Reperfusion Injury via the SIRT1-p53/SLC7A11-Dependent Inhibition of Ferroptosis-Induced Cardiomyocyte Death.","date":"2020","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/33192549","citation_count":178,"is_preprint":false},{"pmid":"31776228","id":"PMC_31776228","title":"USP22 promotes hypoxia-induced hepatocellular carcinoma stemness by a HIF1α/USP22 positive feedback loop upon TP53 inactivation.","date":"2019","source":"Gut","url":"https://pubmed.ncbi.nlm.nih.gov/31776228","citation_count":168,"is_preprint":false},{"pmid":"35449157","id":"PMC_35449157","title":"USP22 regulates lipidome accumulation by stabilizing PPARγ in hepatocellular carcinoma.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/35449157","citation_count":165,"is_preprint":false},{"pmid":"27501329","id":"PMC_27501329","title":"Nuclear GSK3β promotes tumorigenesis by phosphorylating KDM1A and inducing its deubiquitylation by USP22.","date":"2016","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/27501329","citation_count":145,"is_preprint":false},{"pmid":"28160502","id":"PMC_28160502","title":"Deubiquitinating enzyme USP22 positively regulates c-Myc stability and tumorigenic activity in mammalian and breast cancer cells.","date":"2017","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28160502","citation_count":126,"is_preprint":false},{"pmid":"18469533","id":"PMC_18469533","title":"USP22, an hSAGA subunit and potential cancer stem cell marker, reverses the polycomb-catalyzed ubiquitylation of histone H2A.","date":"2008","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/18469533","citation_count":124,"is_preprint":false},{"pmid":"21779003","id":"PMC_21779003","title":"USP22 regulates cell proliferation by deubiquitinating the transcriptional regulator FBP1.","date":"2011","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/21779003","citation_count":118,"is_preprint":false},{"pmid":"32665011","id":"PMC_32665011","title":"The deubiquitinase USP22 regulates PD-L1 degradation in human cancer cells.","date":"2020","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/32665011","citation_count":107,"is_preprint":false},{"pmid":"30224477","id":"PMC_30224477","title":"Control of CCND1 ubiquitylation by the catalytic SAGA subunit USP22 is essential for cell cycle progression through G1 in cancer cells.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/30224477","citation_count":107,"is_preprint":false},{"pmid":"24197134","id":"PMC_24197134","title":"USP22 regulates oncogenic signaling pathways to drive lethal cancer progression.","date":"2013","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/24197134","citation_count":104,"is_preprint":false},{"pmid":"36509766","id":"PMC_36509766","title":"PRDM1/BLIMP1 induces cancer immune evasion by modulating the USP22-SPI1-PD-L1 axis in hepatocellular carcinoma cells.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36509766","citation_count":99,"is_preprint":false},{"pmid":"28417539","id":"PMC_28417539","title":"USP22 mediates the multidrug resistance of hepatocellular carcinoma via the SIRT1/AKT/MRP1 signaling pathway.","date":"2017","source":"Molecular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/28417539","citation_count":94,"is_preprint":false},{"pmid":"34350172","id":"PMC_34350172","title":"LncRNA KCNQ1OT1 Secreted by Tumor Cell-Derived Exosomes Mediates Immune Escape in Colorectal Cancer by Regulating PD-L1 Ubiquitination via MiR-30a-5p/USP22.","date":"2021","source":"Frontiers in cell and developmental 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It is recruited to specific genes by activators such as Myc and is required for activated transcription and cell-cycle progression.\",\n      \"method\": \"Biochemical subunit identification, in vitro deubiquitylation assay, chromatin immunoprecipitation, RNAi loss-of-function\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (biochemical complex purification, in vitro enzymatic assay, ChIP, functional knockdown) in a single rigorous study; foundational finding widely replicated\",\n      \"pmids\": [\"18206973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"USP22 deubiquitylates histone H2A in addition to H2B, antagonizing Polycomb-catalyzed H2A ubiquitylation and thereby activating transcription.\",\n      \"method\": \"Biochemical substrate specificity assay with purified USP22\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assay demonstrating H2A deubiquitylation, single lab, single method\",\n      \"pmids\": [\"18469533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"USP22 (and its mouse homolog Usp22) encode ~525 aa proteins containing the conserved Cys, Asp(I), His, Asp/Asn(II) catalytic domains of the UBP deubiquitinase family and possess deubiquitinating enzyme activity in biochemical assay.\",\n      \"method\": \"Biochemical deubiquitinase activity assay, sequence/domain analysis\",\n      \"journal\": \"Gene expression patterns : GEP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct enzymatic assay confirming DUB activity, single lab, single method\",\n      \"pmids\": [\"16378762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"USP22 interacts with and deubiquitinates SIRT1, removing polyubiquitin chains and stabilizing SIRT1 protein. USP22-mediated SIRT1 stabilization suppresses p53 acetylation and p53-dependent apoptosis. Genetic deletion of Usp22 in mice causes SIRT1 instability, elevated p53 activity, and early embryonic lethality.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, genetic knockout mouse model\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ubiquitination assay, in vivo knockout with defined molecular and developmental phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"22542455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP22 deubiquitinates the transcriptional regulator FBP1 (FUSE-binding protein 1); increased FBP1 polyubiquitination upon USP22 ablation does not alter FBP1 stability but reduces its stable recruitment to target loci (including the p21 gene), thereby regulating p21 expression and cell proliferation.\",\n      \"method\": \"RNAi knockdown, ubiquitination assay, chromatin immunoprecipitation\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and ubiquitination assay with functional readout, single lab, two orthogonal methods\",\n      \"pmids\": [\"21779003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP22 knockdown leads to increased monoubiquitination of histone H2B and impaired transcriptional elongation at the STAT1 target gene IRF1; USP22 depletion also diminishes 3'-end cleavage/polyadenylation and impairs recruitment of polyadenylation factor CPSF73 and serine 2 phosphorylation of RNA Pol II CTD.\",\n      \"method\": \"RNAi knockdown, ChIP, quantitative RT-PCR, rescue by overexpression\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple chromatin and transcription assays, single lab\",\n      \"pmids\": [\"22067483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SIRT1 interacts with USP22 via the ZnF-UBP domain of USP22; this interaction is disrupted by the SIRT1 H363Y inactivating mutation. USP22 is acetylated on multiple lysines; acetylation of K129 within the ZnF-UBP domain alters interaction of the DUB module with the core SAGA complex. SIRT1 recruited by USP22 deacetylates individual SAGA complex components.\",\n      \"method\": \"High-confidence interactome mapping (comparative Co-IP/MS), domain mutagenesis, acetylation mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — quantitative interactome, domain mutagenesis, and acetylation assays; multiple orthogonal methods in single study\",\n      \"pmids\": [\"23382074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"USP22 is required for embryonic stem cell differentiation into all three germ layers. USP22 occupies the Sox2 promoter and hydrolyzes monoubiquitin from H2B, repressing Sox2 transcription; this repression is required for ESCs to transition from self-renewal to differentiation.\",\n      \"method\": \"Loss-of-function (knockdown/knockout in ESCs), chromatin immunoprecipitation, differentiation assays, H2Bub analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP showing USP22 occupancy at Sox2 promoter, H2Bub enzymatic assay at locus, functional differentiation phenotype; multiple methods single lab\",\n      \"pmids\": [\"23760504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP22 deubiquitylates and stabilizes the histone demethylase KDM1A (LSD1) after KDM1A is phosphorylated at Ser683 by GSK3β (primed by CK1α phosphorylation at Ser687). Phosphorylated KDM1A binds USP22, which removes ubiquitin and prevents its proteasomal degradation; this stabilization is required for H3K4 demethylation and repression of BMP2/CDKN1A/GATA6 to drive glioblastoma tumorigenesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, phosphorylation mapping, mutagenesis, ChIP, xenograft models\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reciprocal Co-IP, in vitro ubiquitination/deubiquitination, mutagenesis of phosphorylation sites, ChIP, and in vivo models; multiple orthogonal methods in rigorous study\",\n      \"pmids\": [\"27501329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"USP22 deubiquitinates c-Myc, preventing its proteasomal degradation and increasing c-Myc protein levels in breast cancer cells; USP22 knockdown reduces c-Myc levels.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, knockdown/overexpression\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitination assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"28160502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP22 directly deubiquitylates cyclin D1 (CCND1), protecting it from proteasome-mediated degradation through a mechanism distinct from canonical T286 phosphorylation-dependent ubiquitylation. This non-transcriptional control of CCND1 is a key mechanism by which USP22 promotes G1 cell cycle progression in cancer cells.\",\n      \"method\": \"Ubiquitylation assay, protein stability assay (cycloheximide chase), cell cycle analysis, cancer cell knockdown/KO\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct deubiquitylation assay, protein stability assay, epistasis with cell cycle phenotype; multiple orthogonal methods, single lab\",\n      \"pmids\": [\"30224477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Usp22 (the mouse homolog) promotes antibody class switch recombination and V(D)J recombination by facilitating classical non-homologous end joining (c-NHEJ) for DNA break repair; Usp22 ablation in B cells impairs γH2AX formation and c-NHEJ. CSR to IgA is more reliant on alternative end joining and is less affected by Usp22 loss.\",\n      \"method\": \"Conditional knockout in primary B cells, γH2AX analysis, CSR/V(D)J recombination assays, epistasis with DNA repair pathways\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with defined molecular and functional phenotype in primary cells, multiple DNA repair readouts; single lab but rigorous\",\n      \"pmids\": [\"29520062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP22 deficiency in the context of oncogenic Kras promotes AML transformation by blocking myeloid differentiation. USP22 functions as a deubiquitylase for PU.1, positively regulating PU.1 protein stability and the expression of PU.1 target genes; reconstitution of PU.1 in USP22-deficient Kras progenitors rescues differentiation.\",\n      \"method\": \"Conditional knockout mouse model, bone marrow transplantation, ubiquitylation assay, transcriptomic analysis, PU.1 rescue experiment\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout model, direct ubiquitylation assay for PU.1, epistasis rescue experiment; multiple methods, rigorous\",\n      \"pmids\": [\"29844011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USP22 deubiquitinates and stabilizes HIF1α, promoting hypoxia-induced HCC stemness and glycolysis. In TP53 wild-type cells, HIF1α-induced TP53 suppresses USP22 upregulation; in TP53-mutant cells, USP22 and HIF1α form a positive feedback loop.\",\n      \"method\": \"Immunoprecipitation, ubiquitination assay, chromatin immunoprecipitation, loss/gain-of-function, in vivo mouse model\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, ChIP, and in vivo xenograft models; multiple orthogonal methods single lab\",\n      \"pmids\": [\"31776228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of USP22 in murine intestinal epithelium exacerbates Apc-mutant intestinal tumor burden and increases mTOR activity; USP22 depletion in human CRC cells increases tumorigenic properties reversed by mTOR inhibitor treatment, indicating USP22 exerts tumor-suppressive function in colorectal cancer via mTOR suppression.\",\n      \"method\": \"Tissue-specific conditional knockout mouse model, in vivo tumor assays, mTOR pathway analysis, pharmacological rescue\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo conditional KO with defined tumor phenotype, pharmacological epistasis; multiple methods single lab\",\n      \"pmids\": [\"31527800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cytoplasmic USP22 promotes nuclear translocation of IRF3 after viral infection by deubiquitinating and stabilizing the importin protein KPNA2. Viral infection induces USP22-IRF3 association in the cytoplasm in a KPNA2-dependent manner; USP22 or KPNA2 knockout impairs IRF3 nuclear translocation and type I IFN production. Reconstitution of KPNA2 into USP22-KO cells restores antiviral responses.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, conditional knockout mice (Cre-ER and Lyz2-Cre), KPNA2 reconstitution epistasis, viral infection models\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple Co-IPs, direct ubiquitination assay, two in vivo KO mouse models, epistasis reconstitution; rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"32130408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP22 deubiquitinates PD-L1 directly, inhibiting its proteasomal degradation and stabilizing PD-L1 protein. USP22 also deubiquitinates CSN5 and stabilizes it; either USP22 or CSN5 facilitates the interaction of PD-L1 with the other. USP22 removes K6, K11, K27, K29, K33, and K63-linked ubiquitin chains from both CSN5 and PD-L1.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay specifying linkage types, protein half-life assay, flow cytometry\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitin linkage-specific assays, single lab, two orthogonal methods\",\n      \"pmids\": [\"32665011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP22 controls necroptosis by deubiquitinating RIPK3 at lysines 42, 351, and 518; mutation of RIPK3 K518 reduces necroptosis-associated ubiquitination and amplifies necrosome formation and necroptotic cell death. Loss of USP22 delays TNFα/Smac mimetic/zVAD-induced necroptosis without affecting NF-κB activation or extrinsic apoptosis.\",\n      \"method\": \"USP22 knockout in human tumor cell lines, ubiquitin remnant profiling (mass spectrometry), RIPK3 mutagenesis, cell death assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — ubiquitin remnant profiling by MS, site-directed mutagenesis of RIPK3, KO cell lines with defined death phenotype; multiple orthogonal methods single lab\",\n      \"pmids\": [\"33369872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP22 interacts with MED1 (Mediator complex subunit 1) in iNKT cells. USP22 does not deubiquitinate MED1 for its stabilization; instead, USP22 enhances MED1 transcriptional activity for IL-2Rβ and T-bet gene expression through deubiquitination of histone H2A (not H2B). USP22 deficiency blocks iNKT cell development at stage 1→2 transition in a cell-intrinsic manner.\",\n      \"method\": \"Co-immunoprecipitation, H2A ubiquitination assay, conditional knockout mouse model, iNKT developmental analysis\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, direct H2A deubiquitination assay distinguishing H2A from H2B substrate specificity, in vivo conditional KO; multiple methods single lab\",\n      \"pmids\": [\"32069354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USP22 loss in murine placental endothelial cells and pericytes causes embryonic lethality due to defects in extra-embryonic placental vasculature; USP22 deletion hinders TGFβ and receptor tyrosine kinase signaling cascades with detrimental effects on cell survival, differentiation, and vessel formation.\",\n      \"method\": \"Conditional knockout mouse model, embryonic stem cell-derived endothelial/pericyte differentiation, signaling pathway analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo conditional KO with placental/vascular phenotype and signaling analysis; single lab\",\n      \"pmids\": [\"30718289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Global reduction of Usp22 in mice impairs lineage specification in the small intestine and brain, with altered frequencies of differentiated cells, while H2B and H2Bub1 levels remain constant, indicating USP22 controls differentiation through mechanisms beyond bulk H2Bub1 levels.\",\n      \"method\": \"Usp22 hypomorphic (lacZ knock-in) mouse model, histological analysis, H2Bub1 Western blot\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with tissue-specific differentiation phenotype; single lab\",\n      \"pmids\": [\"26431380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP22 directly interacts with, deubiquitinates (K48-linked), and stabilizes PPARγ, which in turn increases ACC and ACLY expression, promoting de novo fatty acid synthesis and HCC tumorigenesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K48-linkage specific), in vivo tumorigenesis experiments with PPARγ/ACLY/ACC inhibition\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, linkage-specific ubiquitination assay, in vivo epistasis; multiple orthogonal methods single lab\",\n      \"pmids\": [\"35449157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP22 stabilizes ATG5 by decreasing K27- and K48-linked ubiquitination at Lys118, thereby promoting ATG5-mediated autophagy, which in turn degrades NLRP3 and suppresses NLRP3 inflammasome activation. USP22 deficiency increases alum-induced peritonitis and LPS-induced systemic inflammation in vivo.\",\n      \"method\": \"Co-immunoprecipitation, site-specific ubiquitination assay (K27/K48 linkage, Lys118 mutagenesis), autophagy assays, in vivo USP22 silencing models\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — site-specific mutagenesis of ubiquitination site, linkage-specific assays, in vivo inflammasome phenotype; multiple orthogonal methods single lab\",\n      \"pmids\": [\"35900990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP22 controls basal and cGAMP-induced STING activation in human intestinal epithelial cells; loss of USP22 upregulates IFN-λ secretion and ISGs through STING, and USP22-deficient cells are protected against SARS-CoV-2 infection in a STING-dependent manner.\",\n      \"method\": \"USP22-deficient human intestinal epithelial cell lines, STING pathway analysis, SARS-CoV-2 infection assays, epistasis with STING inhibition\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO cells with IFN pathway and antiviral phenotype, STING epistasis; single lab\",\n      \"pmids\": [\"35933402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USP22 interacts with and deubiquitinates BRCA2/PALB2, stabilizing their protein levels; this interaction occurs through the C-terminal WD40 domain of PALB2 and stimulates USP22 catalytic activity in vitro. USP22 is necessary for BRCA2, PALB2, and Rad51 recruitment to DNA double-strand breaks, facilitating homologous recombination repair.\",\n      \"method\": \"Co-immunoprecipitation, in vitro catalytic activity assay, DNA damage foci analysis, HR reporter assay\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro catalytic stimulation assay, Co-IP, DNA repair functional assay; single lab, multiple methods\",\n      \"pmids\": [\"31685642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"USP22 depletion in prostate cancer cells sensitizes them to genotoxic insult; ubiquitylome analysis identified XPC (nucleotide excision repair protein) as a USP22 substrate that undergoes deubiquitylation by USP22 to promote survival after DNA damage.\",\n      \"method\": \"Ubiquitylome profiling, USP22 KO/KD, genotoxic sensitivity assays, novel USP22-overexpressing murine model\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitylome-wide profiling plus functional DNA damage assay; single lab\",\n      \"pmids\": [\"31740444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP22 regulates androgen receptor (AR) accumulation and signaling; it is sufficient to reprogram AR function and induce transition to therapeutic resistance in prostate cancer xenograft models.\",\n      \"method\": \"Xenograft models, USP22 modulation (overexpression/depletion), AR signaling pathway analysis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo xenograft with AR pathway analysis, functional phenotype; single lab\",\n      \"pmids\": [\"24197134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP22 directly interacts with and deubiquitinates COX-2, modulating COX-2 stability; USP22 silencing decreases COX-2 protein half-life and inhibits lung carcinoma cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, cycloheximide-chase protein stability assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, and protein stability assay; single lab, multiple methods\",\n      \"pmids\": [\"25817787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP22 deubiquitinates EGFR on late endosomes, preventing ubiquitin-mediated EGFR degradation and enhancing EGFR recycling after EGF stimulation, thereby sustaining EGFR downstream signaling (STAT3, AKT/mTOR, MEK/ERK) and conferring resistance to EGFR-TKIs.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, endosomal localization, EGFR recycling assay, in vitro and in vivo knockdown\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, subcellular localization, recycling assay; single lab\",\n      \"pmids\": [\"29981430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP22 positively modulates ERα stability and transactivation via its deubiquitinase activity; USP22 is recruited together with ERα to cis-regulatory elements of ERα target genes, and USP22 deubiquitinase activity is required for maintaining ERα stability and conferring endocrine resistance.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, ubiquitination assay, mutagenesis (deubiquitinase-dead), overexpression/knockdown\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, ChIP, deubiquitinase-dead mutant; single lab, multiple methods\",\n      \"pmids\": [\"32494025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP22 promotes EMT in pancreatic cancer cells through the FAK signaling pathway, promoting Ezrin redistribution/phosphorylation, cytoskeletal remodeling, and upregulation of EMT transcription factors Snail and ZEB1; blockade of USP22 reverses these effects.\",\n      \"method\": \"Overexpression/knockdown in PANC-1 cells, phosphorylation analysis, immunofluorescence, invasion assay\",\n      \"journal\": \"Oncology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional phenotype with pathway placement but no direct substrate deubiquitination assay; single lab, single cell line\",\n      \"pmids\": [\"25070659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP22 interacts with NFATc2 and deubiquitinates it, stabilizing NFATc2 protein levels; USP22 depletion in T cells reduces IL-2 expression, and this stabilization requires USP22 deubiquitinase activity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, knockdown in T cells, IL-2 expression analysis\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and direct ubiquitination assay with functional T cell readout; single lab\",\n      \"pmids\": [\"24561192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"USP22 overexpression downregulates STAT3 acetylation by deubiquitinating and stabilizing SIRT1; USP22, SIRT1, and STAT3 form a single protein complex. USP22 knockdown destabilizes SIRT1 and elevates STAT3 acetylation, with downstream reduction of MMP9 and TWIST expression.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, Western blot for acetylated STAT3\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP confirming ternary complex, ubiquitination/acetylation assays; single lab\",\n      \"pmids\": [\"24969755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP22 deubiquitinase activity (demonstrated with C185S and Y513C mutants) is necessary for cell cycle regulation in HeLa cells and is required for maintaining BMI-1, c-Myc, cyclin D2, and p53 levels.\",\n      \"method\": \"Active-site mutagenesis (C185S catalytic dead, Y513C activity-reduced), cell cycle analysis, Western blot\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site mutagenesis directly linking catalytic activity to cellular phenotype; single lab, single cell line\",\n      \"pmids\": [\"26143114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"USP22 stabilizes BMI1 protein in gastric cancer cells through deubiquitination; USP22 knockdown suppresses cancer stem cell sphere formation, reduces CD133/SOX2/OCT4/NANOG expression, and these effects are rescued by TAT-BMI1 protein reconstitution.\",\n      \"method\": \"Knockdown/overexpression, protein stability assay, sphere formation assay, BMI1 reconstitution rescue\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis rescue with BMI1, protein stability assay; single lab\",\n      \"pmids\": [\"28415621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 deubiquitinates STAT1 and improves its stability in melanoma cells; USP22 deficiency impairs sensitivity to IFNγ-JAK1-STAT1 signaling, reducing T cell-mediated killing; USP22 overexpression enhances tumor cell sensitivity to T cell killing.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, CRISPR-Cas9 KO screen, in vitro and in vivo T cell killing assays\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen followed by Co-IP, ubiquitination assay, and functional T cell assays; single lab\",\n      \"pmids\": [\"33601053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 promotes HER2-driven mammary carcinoma by stabilizing the ER chaperone HSPA5, actively suppressing unfolded protein response (UPR) induction; USP22 loss renders tumor cells more sensitive to apoptosis and ER-stress targeting therapies.\",\n      \"method\": \"Genetic mouse models, human HER2+ cell lines, transcriptome-wide gene expression analysis, HSPA5 stability assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic mouse models plus transcriptomic identification of UPR pathway; HSPA5 stabilization assay; single lab\",\n      \"pmids\": [\"34007022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 deubiquitinates and stabilizes E2F6, which transcriptionally represses the phosphatase DUSP1, leading to AKT activation in HCC cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, luciferase reporter, knockdown epistasis\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, transcriptional reporter; single lab, multiple methods\",\n      \"pmids\": [\"34339800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 deubiquitinates and stabilizes PTEN in pancreatic cancer cells; USP22-mediated PTEN stabilization induces p21 expression through PTEN interaction with ANKHD1, inhibiting ANKHD1 binding to the p21 promoter.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, ChIP, overexpression/knockdown\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitination assay, functional epistasis; single lab\",\n      \"pmids\": [\"34743406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP22 deubiquitinates and stabilizes the EMT transcription factor Snail1 in renal tubular epithelial cells, depending on its deubiquitinase activity, thereby promoting EMT and diabetic renal tubulointerstitial fibrosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, deubiquitinase activity mutant, in vivo db/db mouse model\",\n      \"journal\": \"European journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, in vivo model; single lab, multiple methods\",\n      \"pmids\": [\"37001578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP22 acts as a co-activator of VEGFA transcription by maintaining ZEB1 stability via its deubiquitinase activity; USP22 is recruited to ZEB1-binding elements on the VEGFA promoter and alters H2Bub1 levels to enhance ZEB1-mediated VEGFA transcription.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, ChIP, H2Bub1 chromatin analysis, knockdown/overexpression\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, ChIP at VEGFA promoter; single lab, multiple methods\",\n      \"pmids\": [\"36906615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PRDM1 enhances USP22 transcription, and USP22 in turn reduces SPI1 (PU.1) protein degradation through deubiquitination, which enhances PD-L1 transcription in HCC cells, dampening antitumor immunity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, ChIP, gain-of-function in vivo models\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitination assay for SPI1 deubiquitination, in vivo immune phenotype; single lab\",\n      \"pmids\": [\"36509766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Gα12 stabilizes SIRT1 protein through transcriptional induction of USP22 via HIF-1α; USP22 in turn deubiquitinates and stabilizes SIRT1 to regulate mitochondrial respiration and hepatic lipid metabolism.\",\n      \"method\": \"cDNA microarray, Gna12-KO mouse model, lentiviral overexpression, protein stability assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO model plus lentiviral rescue, identification of USP22 as transcriptional target of Gα12/HIF-1α; single lab\",\n      \"pmids\": [\"30300140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP22 interacts with RCAN1 (regulator of calcineurin 1) and promotes RCAN1 deubiquitination and protein stabilization, antagonizing FBW7, NEDD4-2, and β-TrCP E3 ligase actions on RCAN1. IFN-α treatment dissociates RCAN1 from USP22, triggering RCAN1 ubiquitination and degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, E3 ligase competition assay, IFN-α treatment\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, multiple E3 ligase competition; single lab\",\n      \"pmids\": [\"25546086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Phosphorylated MYH9 (Ser1943) recruits USP22 to deubiquitinate and stabilize HIF-1α in lenvatinib-resistant HCC, promoting cancer stemness. A CK2 inhibitor or USP22 inhibitor effectively reversed lenvatinib resistance in vivo and in vitro.\",\n      \"method\": \"Immunoprecipitation, mass spectrometry, ubiquitination assay, RNA-sequencing, patient-derived xenograft models\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identifying the interaction, ubiquitination assay for HIF-1α, in vivo PDX model; single lab\",\n      \"pmids\": [\"39300073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"EZH2 inhibition transcriptionally upregulates USP22, which in turn stabilizes PD-L1 via deubiquitination in colorectal cancer cells. Knockdown of USP22 enhances therapeutic efficacy of EZH2 inhibitors.\",\n      \"method\": \"USP22 knockdown/overexpression, ubiquitination assay, protein stability assay, in vivo tumor models\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination and stability assays with in vivo epistasis; single lab\",\n      \"pmids\": [\"38520088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The small molecule demethylzeylasteral (Dem) binds USP22 and promotes its degradation, resulting in increased ubiquitination and proteasomal degradation of PD-L1; structure-based analysis identified Leu475 and Arg419 as crucial residues for USP22 inhibitor binding.\",\n      \"method\": \"Structure-based virtual screening, binding assay, ubiquitination assay, in vivo syngeneic tumor model, molecular dynamics simulation\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct binding assay, ubiquitination assay, residue identification by MD; single lab\",\n      \"pmids\": [\"39525573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Structure-based inhibitor discovery identified Rottlerin and Morusin as selective USP22 inhibitors (IC50 2.53 and 8.29 μM, respectively); treatment with these compounds increases H2A and H2B monoubiquitination and reduces Sirt1 and PD-L1 protein levels, consistent with USP22 substrate specificity. Key binding residues Leu475 (conserved) and Arg419 (non-conserved) are crucial for inhibitory function.\",\n      \"method\": \"Structure-based virtual screening, in vitro USP22 enzyme assay, cellular ubiquitination assay, in vivo syngeneic tumor model, molecular dynamics/binding free energy calculation\",\n      \"journal\": \"Bioorganic chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with selectivity profiling, cellular substrate validation, and structural modeling; single lab\",\n      \"pmids\": [\"37769523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The USP22 promoter basal activity is controlled by the -210 to -7 region; an Sp1 binding site immediately upstream of the transcriptional start site (-13 to -7) acts as a repressor—Sp1 binding suppresses USP22 transcription, and Sp1 knockdown or inhibition increases USP22 mRNA levels.\",\n      \"method\": \"5'-RACE, promoter deletion analysis, mutagenesis, Sp1 ChIP, mithramycin A treatment, Sp1 overexpression/knockdown\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter deletion mapping, Sp1 mutagenesis, ChIP, pharmacological and genetic Sp1 manipulation; single lab\",\n      \"pmids\": [\"23300749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP22 depletion in pancreatic tumor cells reduces myeloid cell infiltration and promotes T cell and NK cell infiltration, leading to improved response to combination immunotherapy; USP22 exerts its effects on the tumor immune microenvironment through its association with the deubiquitylase module of the SAGA/STAGA complex and reshaping the cancer cell transcriptome.\",\n      \"method\": \"USP22 deletion in pancreatic tumor cells, immune cell profiling, immunotherapy response assay, SAGA complex association analysis\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo deletion model with immune microenvironment phenotype, SAGA association; single lab\",\n      \"pmids\": [\"31871120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 suppresses SPARC expression in intestinal epithelial cells by affecting H3K27ac and H2Bub1 occupancy on the SPARC gene; Usp22 intestine-specific deletion upregulates SPARC and increases colitis severity and inflammation-associated colorectal tumor growth.\",\n      \"method\": \"Intestine-specific conditional Usp22 KO mouse, DSS colitis model, chromatin immunoprecipitation (H3K27ac, H2Bub1), gene expression analysis\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO in vivo with ChIP evidence at SPARC locus; single lab\",\n      \"pmids\": [\"33920268\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP22 deubiquitinates and stabilizes FASN; in p53 wild-type CRC cells, H2O2-induced p53 represses USP22 transcription, reducing FASN stability and fatty acid synthesis. In p53-deficient cells, this repression is relieved, leading to FASN stabilization and increased lipid synthesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, FASN protein stability assay, p53 transcriptional repression of USP22, lipogenesis assay\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination/stability assays, p53-USP22 transcriptional epistasis; single lab\",\n      \"pmids\": [\"36333288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP22 deubiquitinates and stabilizes LSD1 (KDM1A) in osteosarcoma; USP22 knockdown leads to ubiquitination and degradation of LSD1, reduced p21 repression, and inhibited cell proliferation/invasion. miR-140 suppresses this axis by targeting USP22.\",\n      \"method\": \"Knockdown/overexpression, ubiquitination assay, protein stability assay, in vivo xenograft\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination and stability assays for LSD1 substrate, in vivo xenograft; single lab\",\n      \"pmids\": [\"33868787\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"USP22 is a catalytic deubiquitylase subunit of the mammalian SAGA transcriptional co-activator complex that removes monoubiquitin from histones H2B and H2A to regulate transcription elongation, 3'-end processing, and epigenetic gene control; beyond histones, USP22 stabilizes a broad array of non-histone substrates—including SIRT1, HIF1α, PPARγ, CCND1, c-Myc, KDM1A/LSD1, PU.1, KPNA2, ATG5, RIPK3, PD-L1, ERα, EGFR, PTEN, STAT1, NFATc2, ZEB1, Snail1, FASN, and others—by deubiquitinating them and preventing proteasomal degradation, thereby acting as a multi-substrate DUB that integrates transcriptional, cell-cycle, apoptotic, immune, metabolic, and DNA-repair programs in both normal development and cancer.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"USP22 is the catalytic deubiquitylase subunit of the human SAGA transcriptional coactivator complex, where it hydrolyzes monoubiquitin from histones H2B and H2A to control activated transcription, transcriptional elongation, mRNA 3'-end processing, and cell-cycle progression [#0, #1, #5]. Within SAGA, USP22 is recruited to target genes by activators such as Myc and engages SIRT1 through its ZnF-UBP domain; the recruited SIRT1 deacetylates SAGA components, and reciprocal acetylation of USP22 modulates how the deubiquitinase module docks onto the core complex [#0, #6]. Through this chromatin activity, USP22 governs developmental programs—it is required for embryonic stem cell exit from self-renewal by hydrolyzing H2Bub at the Sox2 promoter, and Usp22 loss disrupts lineage specification in intestine and brain independent of bulk H2Bub1 levels [#7, #20]. Beyond histones, USP22 is a multi-substrate deubiquitinase that stabilizes diverse non-histone proteins by removing degradative ubiquitin chains: it stabilizes SIRT1 to suppress p53-dependent apoptosis, an activity essential for embryonic viability [#3], and the catalytic-site requirement for these functions is established by active-site mutants (C185S, Y513C) that abolish maintenance of substrate levels and cell-cycle control [#33]. Its substrate repertoire spans transcription factors and chromatin regulators (KDM1A/LSD1, c-Myc, PU.1, BMI1, E2F6, ZEB1, Snail1, PPARγ) [#8, #9, #12, #34, #37, #40, #39, #21], cell-cycle and growth-control proteins (CCND1, PTEN) [#10, #38], metabolic enzymes (FASN) [#51], and receptors/signaling nodes (EGFR deubiquitinated on late endosomes, ERα, HIF1α) [#28, #29, #13]. In immunity and cell death, USP22 stabilizes KPNA2 to drive IRF3 nuclear translocation and type I interferon production, deubiquitinates RIPK3 to restrain necroptosis, stabilizes ATG5 to promote autophagic suppression of the NLRP3 inflammasome, stabilizes STAT1 to sustain IFNγ sensitivity, and stabilizes PD-L1 to dampen antitumor immunity [#15, #17, #22, #35, #16]. USP22 also promotes DNA double-strand break repair, facilitating BRCA2/PALB2/Rad51 recruitment for homologous recombination and supporting c-NHEJ during antibody class switch and V(D)J recombination [#24, #11]. Across cancers USP22 exhibits context-dependent oncogenic and tumor-suppressive roles, suppressing mTOR signaling in the intestine while promoting proliferation, stemness, metabolic reprogramming, and therapy resistance elsewhere [#14, #10, #13]. USP22 transcription is itself regulated—repressed by an Sp1 site at its promoter and by p53—and small-molecule inhibitors (Rottlerin, Morusin, demethylzeylasteral) targeting residues including Leu475 and Arg419 reduce its substrate stabilization [#48, #51, #47, #46].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that USP22 is a bona fide enzyme, defining it as a UBP-family deubiquitinase with the conserved catalytic residues required for ubiquitin hydrolysis.\",\n      \"evidence\": \"Sequence/domain analysis and biochemical DUB activity assay on the ~525 aa protein and its mouse homolog\",\n      \"pmids\": [\"16378762\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No physiological substrate identified at this stage\", \"No structural model of the catalytic domain\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Placed USP22 within the SAGA coactivator complex and identified histones as its substrates, explaining how a DUB controls transcription and cell-cycle progression.\",\n      \"evidence\": \"Biochemical subunit purification, in vitro H2B and H2A deubiquitylation, ChIP, and RNAi loss-of-function\",\n      \"pmids\": [\"18206973\", \"18469533\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of H2B vs H2A deubiquitylation to specific genes unresolved\", \"Mechanism of activator-directed recruitment beyond Myc not detailed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended USP22's chromatin role beyond histone removal to transcriptional elongation, 3'-end processing, and recruitment/stable loading of regulatory factors at target loci.\",\n      \"evidence\": \"RNAi knockdown, ChIP, qRT-PCR, and ubiquitination assays at IRF1 and p21 loci (FBP1)\",\n      \"pmids\": [\"22067483\", \"21779003\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between H2Bub and CPSF73/Pol II Ser2-P recruitment mechanistic detail incomplete\", \"Generality across the genome not established\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated USP22 acts on non-histone substrates in vivo, showing SIRT1 stabilization suppresses p53 and is essential for embryonic viability—reframing USP22 as a multi-substrate DUB.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination assay, RNAi, and Usp22 knockout mouse\",\n      \"pmids\": [\"22542455\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SIRT1 stabilization is SAGA-dependent or cytoplasmic not fully resolved\", \"Full breadth of non-histone substrate spectrum unknown at this point\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the structural basis of the USP22–SIRT1 interaction and showed reciprocal post-translational crosstalk (USP22 acetylation, SIRT1 deacetylation of SAGA) regulating DUB module assembly.\",\n      \"evidence\": \"Comparative Co-IP/MS interactome, ZnF-UBP domain mutagenesis, acetylation site mapping\",\n      \"pmids\": [\"23382074\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzyme responsible for USP22 acetylation not identified\", \"Functional consequence of K129 acetylation on substrate selection not quantified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected USP22 chromatin activity to a developmental decision, showing H2Bub removal at Sox2 represses pluripotency and licenses ESC differentiation.\",\n      \"evidence\": \"Knockdown/knockout in ESCs, ChIP, locus H2Bub analysis, three-germ-layer differentiation assays\",\n      \"pmids\": [\"23760504\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other pluripotency loci are co-regulated not addressed\", \"Recruitment determinants at the Sox2 promoter undefined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided genetic active-site evidence directly tying USP22 catalytic activity to maintenance of cell-cycle regulators and demonstrated tissue-level differentiation roles uncoupled from bulk H2Bub1.\",\n      \"evidence\": \"C185S/Y513C active-site mutants with cell-cycle readout; Usp22 hypomorphic mouse with intestine/brain phenotypes and unchanged global H2Bub1\",\n      \"pmids\": [\"26143114\", \"26431380\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Locus-specific vs global H2Bub effects not reconciled\", \"Which substrates dominate the differentiation phenotype unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Expanded USP22 into receptor and endosomal signaling and direct cell-cycle control, deubiquitinating EGFR on late endosomes to sustain signaling and stabilizing cyclin D1 independent of T286 phosphorylation.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, endosomal localization, recycling assay, cycloheximide chase, cell-cycle analysis\",\n      \"pmids\": [\"29981430\", \"30224477\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a SAGA subunit accesses late endosomal EGFR mechanistically unexplained\", \"Cytoplasmic vs nuclear pools of USP22 not quantified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established USP22's roles in DNA repair and hematopoietic differentiation through PU.1 stabilization and c-NHEJ facilitation, with in vivo genetic models.\",\n      \"evidence\": \"Conditional B-cell and Kras-progenitor knockouts, ubiquitylation assays, γH2AX/CSR/V(D)J readouts, PU.1 rescue\",\n      \"pmids\": [\"29520062\", \"29844011\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct DNA-repair substrate(s) underlying c-NHEJ effect not all defined\", \"Tissue-context determinants of oncogenic vs differentiation roles unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed USP22's context-dependent tumor biology—tumor-suppressive via mTOR restraint in intestine versus oncogenic stabilization of HIF1α—and demonstrated direct roles in homologous recombination repair.\",\n      \"evidence\": \"Tissue-specific conditional KO mice, mTOR pharmacological rescue, ubiquitination/ChIP assays for HIF1α, BRCA2/PALB2/Rad51 foci and HR reporter assays\",\n      \"pmids\": [\"31527800\", \"31776228\", \"31685642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular determinant switching USP22 between suppressor and oncogene unknown\", \"Whether HR function requires SAGA or is chromatin-independent unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Positioned USP22 as a central regulator of innate immunity and cell death by stabilizing KPNA2 (IRF3 translocation/IFN-I), restraining RIPK3-driven necroptosis, and stabilizing PD-L1 and the iNKT transcriptional program.\",\n      \"evidence\": \"Co-IP, linkage-specific and remnant-profiling ubiquitination assays, RIPK3 site mutagenesis, conditional KO mice, viral and necroptosis models\",\n      \"pmids\": [\"32130408\", \"33369872\", \"32665011\", \"32069354\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How USP22 selects K-linkage-specific chains on different substrates unclear\", \"Cytoplasmic targeting signals for these substrates undefined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked USP22 to metabolic and inflammatory homeostasis through site-specific stabilization of PPARγ, FASN, and ATG5, the latter coupling autophagy to NLRP3 inflammasome suppression.\",\n      \"evidence\": \"Co-IP, linkage- and lysine-site-specific ubiquitination assays, autophagy/lipogenesis assays, in vivo inflammation and tumor models\",\n      \"pmids\": [\"35449157\", \"36333288\", \"35900990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants of site-specific deubiquitination (e.g. ATG5 Lys118) not structurally explained\", \"Crosstalk between metabolic and immune substrates in vivo not integrated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Advanced USP22 as a druggable target, identifying selective small-molecule inhibitors and binding residues whose engagement reduces stabilization of substrates including PD-L1 and SIRT1.\",\n      \"evidence\": \"Structure-based virtual screening, in vitro enzyme assays, binding/MD studies, cellular ubiquitination assays, syngeneic and PDX tumor models\",\n      \"pmids\": [\"37769523\", \"39525573\", \"39300073\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimentally determined high-resolution USP22 structure reported in the corpus\", \"Selectivity over other USP-family DUBs only partially profiled\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how a single SAGA-associated deubiquitinase achieves substrate selectivity across dozens of histone and non-histone targets and how cellular context dictates its opposing tumor-suppressive versus oncogenic outputs.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model for substrate/linkage discrimination\", \"No high-resolution structure of full-length USP22 or its substrate complexes\", \"Determinants of nuclear/SAGA vs cytoplasmic substrate engagement undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 8, 10, 16, 17, 22, 24]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [2, 0, 33]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 5, 7, 40, 49]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 7, 5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [15, 3]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [28]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 1, 7, 50]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 5, 7, 40]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 1, 50]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [10, 33]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [24, 11, 25]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [15, 16, 35, 22, 41]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 17]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [21, 51, 13]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [13, 14, 26, 28, 44]}\n    ],\n    \"complexes\": [\"SAGA/STAGA deubiquitinase module\"],\n    \"partners\": [\"SIRT1\", \"KDM1A\", \"HIF1A\", \"KPNA2\", \"RIPK3\", \"PPARG\", \"BRCA2\", \"PALB2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}