{"gene":"USP1","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2005,"finding":"USP1 is a deubiquitinating enzyme that physically associates with FANCD2 and deubiquitinates monoubiquitinated FANCD2; inhibition of USP1 leads to hyperaccumulation of monoubiquitinated FANCD2, and USP1 co-localizes with FANCD2 in chromatin after DNA damage.","method":"RNAi screen, Co-IP, chromatin fractionation, chromosomal aberration assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, colocalization, and functional RNAi knockdown with defined phenotypic readout; replicated extensively by multiple subsequent labs","pmids":["15694335"],"is_preprint":false},{"year":2009,"finding":"Targeted deletion of mouse Usp1 results in elevated perinatal lethality, male infertility, crosslinker hypersensitivity, and an FA phenotype; Usp1−/− MEFs show heightened monoubiquitinated Fancd2 in chromatin, impaired Fancd2 foci assembly, and a defect in homologous recombination repair. Double knockout of Usp1 and Fancd2 produces a more severe phenotype than either single knockout, placing Usp1 downstream in the FA pathway.","method":"Targeted gene knockout (mouse), MEF analysis, epistasis (double KO), chromosomal aberration assay, HR repair assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular and organismal phenotype plus genetic epistasis, replicated in multiple follow-up studies","pmids":["19217432"],"is_preprint":false},{"year":1998,"finding":"USP1 encodes a 785-amino-acid ubiquitin-specific protease; recombinant USP1 protein displays genuine UBP deubiquitinase activity, correctly cleaving Ub-beta-galactosidase to produce ubiquitin and beta-galactosidase.","method":"Recombinant protein expression, in vitro enzymatic cleavage assay","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro reconstitution of enzymatic activity; single lab but unambiguous biochemical assay","pmids":["9806842"],"is_preprint":false},{"year":2010,"finding":"Human ELG1 interacts with the USP1-UAF1 deubiquitinase complex and specifically directs it toward PCNA deubiquitination (but not FANCD2 deubiquitination); a conserved N-terminal domain of ELG1 is required for USP1-UAF1 interaction and PCNA monoubiquitination downregulation.","method":"Co-IP, RNAi knockdown, domain mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interactions mapped with domain deletions plus functional RNAi readout; single lab, two orthogonal methods","pmids":["20147293"],"is_preprint":false},{"year":2011,"finding":"USP1 acts in complex with UAF1 to promote homologous recombination (HR)-mediated double-strand break repair; USP1/UAF1-deficient chicken DT40 cells show sensitivity to camptothecin and PARP inhibitors, and disruption of NHEJ in UAF1-deficient cells restores resistance, indicating that USP1/UAF1 promotes HR at least partly by suppressing NHEJ.","method":"Gene knockout in chicken DT40 cells, drug sensitivity assay, epistasis with NHEJ disruption","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockouts with multiple drug sensitivity readouts and epistasis analysis; multiple orthogonal lines of evidence","pmids":["21482670"],"is_preprint":false},{"year":2011,"finding":"USP1 deubiquitinates ID1, ID2, and ID3 proteins (inhibitors of DNA binding), thereby stabilizing them and promoting a stem cell-like mesenchymal state in osteosarcoma; USP1 knockdown precipitates ID protein destabilization, cell-cycle arrest, and osteogenic differentiation.","method":"Co-IP, ubiquitination assay, RNAi knockdown, protein stability assay, mouse knockout phenotype (osteopenia)","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, in vivo deubiquitination assay, RNAi with differentiation phenotype, and KO mouse with bone phenotype; multiple orthogonal methods","pmids":["21925315"],"is_preprint":false},{"year":2011,"finding":"USP1 is degraded in G1 phase via APC/C(Cdh1)-mediated ubiquitination; low USP1 levels in G1 are required to permit PCNA monoubiquitination in response to UV damage; expression of a degradation-resistant USP1 mutant inhibits PCNA monoubiquitination during G1, compromising translesion synthesis polymerase recruitment.","method":"Cell-cycle synchronization, protein stability assay, APC/C(Cdh1) substrate analysis, PCNA ubiquitination assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — cell-cycle-specific degradation shown with synchronized cells, degradation-resistant mutant used as functional tool with defined molecular readout; two orthogonal methods","pmids":["21768287"],"is_preprint":false},{"year":2011,"finding":"USP1 depletion stimulates DDB1-dependent degradation of phosphorylated CHK1; USP1 maintains total and phosphorylated CHK1 levels in response to genotoxic stress, both in a FANCD2-monoubiquitination-dependent and -independent manner, placing USP1 in a feedback circuit that downregulates CHK1 after DNA damage.","method":"RNAi knockdown, protein stability assay, epistasis with monoubiquitinated FANCD2","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi depletion with defined CHK1 stability readout and epistasis analysis; single lab, two orthogonal methods","pmids":["21389083"],"is_preprint":false},{"year":2012,"finding":"USP1 undergoes autocleavage at a conserved G670/G671 diglycine motif, producing a C-terminal fragment (Gln-Usp1(Ct)) that is targeted for degradation by the Arg/N-end rule pathway through deamidation of its N-terminal Gln by Ntaq1; metabolic stabilization of Gln-Usp1(Ct) decreases PCNA monoubiquitination and causes hypersensitivity to UV irradiation.","method":"In vivo autocleavage assay, N-end rule pathway analysis, PCNA ubiquitination assay, UV sensitivity assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical identification of autocleavage product, N-end rule pathway substrate validation, functional UV sensitivity phenotype with defined molecular readout; multiple orthogonal methods","pmids":["23159736"],"is_preprint":false},{"year":2012,"finding":"UAF1 activates USP1 by modulating its active site conformation: UAF1 lowers the pKa of the catalytic histidine in USP1 by ~0.43 pH units (without changing the catalytic cysteine pKa), facilitating general base catalysis at neutral pH. USP1/UAF1 uses a general base catalysis mechanism (not an ion-pair mechanism), with a kinetic isotope effect of ~2.8–3.0 and single proton transfer in the transition state.","method":"In vitro kinetic analysis (pH-dependent inactivation, solvent kinetic isotope effect, proton inventory), active site mutagenesis","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — rigorous in vitro enzymology with multiple mechanistic probes; single lab but multiple orthogonal biochemical methods","pmids":["22439892"],"is_preprint":false},{"year":2012,"finding":"USP1 contains two nuclear localization signals (NLSs) that mediate nuclear import of the USP1/UAF1 complex; USP1 and UAF1 form a complex in the cytoplasm that subsequently translocates to the nucleus via USP1 NLSs. The UAF1-binding site was mapped to a conserved ~100 amino acid motif in the Fingers subdomain of USP1 (residues 420–520).","method":"Nuclear localization signal mutagenesis, cellular relocation assay, deletion mapping","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with NLS mutants and domain deletion mapping; single lab, two orthogonal methods","pmids":["22701671"],"is_preprint":false},{"year":2013,"finding":"CAPNS1 (calpain regulatory subunit) is required for USP1 stability; calpain stabilizes USP1 by activating Cdk5, which in turn inhibits Cdh1 and thereby prevents APC/C(Cdh1)-mediated USP1 degradation. Loss of CAPNS1 increases ubiquitinated PCNA, favors polymerase-η loading on chromatin, and increases mutagenesis.","method":"RNAi knockdown (CAPNS1), protein stability assay, rescue with Cdk5/p25 overexpression, PCNA ubiquitination and pol-η chromatin loading assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis between calpain/Cdk5/Cdh1 and USP1 stability with functional readout; single lab, multiple orthogonal methods","pmids":["23589330"],"is_preprint":false},{"year":2014,"finding":"The USP1-UAF1 complex is a key regulator of the DNA translesion synthesis (TLS) and Fanconi anemia (FA) deubiquitination pathways; ML323, a potent and selective inhibitor of USP1-UAF1, increases monoubiquitinated PCNA and FANCD2 in cells after UV/cisplatin damage, demonstrating that deubiquitination by this complex is required for the DNA damage response.","method":"Selective small-molecule inhibitor (ML323) with selectivity profiling against panel of DUBs, cell-based PCNA/FANCD2 ubiquitination assay","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — highly selective inhibitor with rigorous selectivity profiling, replicated cellular and biochemical readouts across multiple labs","pmids":["24531842"],"is_preprint":false},{"year":2016,"finding":"USP1 binds to and is stimulated by fork DNA; a truncated USP1 lacking its DNA-binding region is not stimulated by DNA and fails to localize to and protect replication forks. Persistence of monoubiquitinated PCNA at stalled replication forks is the mechanism of cell death in BRCA1-deficient cells lacking USP1.","method":"DNA-binding assay, truncation mutant analysis, replication fork protection assay (DNA fiber), live-cell imaging/localization, USP1 knockdown/inhibition in BRCA1-deficient cells","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain deletion mutant with DNA-binding assay, fork protection fiber assay, mechanistic rescue experiments; multiple orthogonal methods","pmids":["30576655"],"is_preprint":false},{"year":2016,"finding":"The USP1-UAF1 complex interacts with RAD51AP1 through UAF1; depletion of USP1 or UAF1 destabilizes RAD51AP1. The USP1-UAF1-RAD51AP1 interaction promotes a late step of HR repair (RAD51 foci resolution) independently of FANCD2 deubiquitination.","method":"Proteomics (UAF1 interactome), Co-IP, domain mapping, RNAi knockdown, RAD51 foci analysis, chromosomal aberration assay","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based interactome plus Co-IP validation and functional epistasis; single lab, two orthogonal methods","pmids":["27463890"],"is_preprint":false},{"year":2016,"finding":"PDGF signaling upregulates USP1 transcription through E2F transcription factors, which directly bind the Usp1 promoter; USP1 then stabilizes ID2, which is required for glioma cell survival in a PDGF-driven mouse model.","method":"Comparative transcriptomics, ChIP (E2F binding to Usp1 promoter), genetic ablation of Id2/Usp1, pharmacological USP1 inhibition, mouse glioma model","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-confirmed transcriptional regulation and in vivo mouse model with survival readout; single lab, multiple orthogonal methods","pmids":["26951930"],"is_preprint":false},{"year":2017,"finding":"The USP1-UAF1 complex stabilizes TBK1 by removing its K48-linked polyubiquitination, thereby preventing TBK1 degradation and enhancing TLR3/4 and RIG-I-induced IRF3 activation and IFN-β secretion during antiviral responses.","method":"Co-IP, ubiquitination assay (K48-linked), RNAi knockdown, IFN-β reporter assay, ML323 inhibitor in vitro/in vivo","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with ubiquitin linkage specificity and functional IFN-β readout; single lab, two orthogonal methods","pmids":["29138248"],"is_preprint":false},{"year":2018,"finding":"USP1 deubiquitinates and stabilizes KPNA2; USP1-mediated stabilization of KPNA2 is required for USP1's pro-metastatic function in breast cancer cells in vitro and in vivo.","method":"Co-IP, ubiquitination assay, RNAi knockdown, rescue experiments, mouse lung metastasis model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay and in vivo rescue; single lab, two orthogonal methods","pmids":["30531833"],"is_preprint":false},{"year":2018,"finding":"USP1 deubiquitinates CHK1 to maintain its phosphorylated levels; USP1 also stabilizes Survivin/BIRC5 in glioblastoma stem cells and Survivin is shown to be downstream of USP1 in EWS cells; USP1 depletion reduces ID1 and CHK1 protein stability in glioblastoma.","method":"RNAi knockdown, protein stability assay, USP1 inhibitor (pimozide), in vivo mouse model","journal":"Neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — RNAi/inhibitor with protein level readout across two independent studies, but no direct deubiquitination reconstitution in this paper","pmids":["26032834"],"is_preprint":false},{"year":2018,"finding":"Upon platinum treatment, USP1 is phosphorylated by ATM and ATR kinases, binds to Snail, deubiquitinates and stabilizes Snail protein, thereby promoting tumor dissemination and conferring platinum resistance in ovarian cancer. USP1 knockout or inhibition increased platinum sensitivity and decreased metastatic dissemination in a Snail-dependent manner.","method":"Co-IP, ubiquitination assay, kinase inhibitor epistasis (ATM/ATR), in vivo mouse model, USP1 knockout/inhibition","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, and in vivo mouse metastasis model with Snail-rescue epistasis; single lab, multiple methods","pmids":["31086816"],"is_preprint":false},{"year":2019,"finding":"Efficient FANCD2 deubiquitination by USP1-UAF1 requires DNA and DNA binding by UAF1; the DNA-binding activity of RAD51AP1 can substitute for that of UAF1 in FANCD2 deubiquitination in a reconstituted biochemical system. Both UAF1 and RAD51AP1 DNA-binding activities are important for FANCD2 deubiquitination in cells.","method":"Reconstituted biochemical deubiquitination assay with purified components, DNA-binding mutant analysis, cellular assay with UAF1/RAD51AP1 mutants","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — fully reconstituted in vitro biochemical system with purified proteins plus validation in cells; single lab but rigorous reconstitution","pmids":["31253762"],"is_preprint":false},{"year":2020,"finding":"USP1 removes K63-linked polyubiquitin chains on Akt to restrict PI3K-Akt-FoxO signaling in mouse muscle during prolonged starvation; a USP1 complex containing Dab2, TSC1/TSC2, and PHLPP1 is identified, with Dab2 essential for Akt recruitment to this complex for PI3K-Akt-FoxO inhibition.","method":"DUB screening, Co-IP, mass spectrometry, RNAi knockdown in mouse muscle, glucose uptake assay, ubiquitin linkage analysis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — DUB screen plus Co-IP/MS complex identification and in vivo mouse muscle RNAi with functional readout; single lab, multiple orthogonal methods","pmids":["32133736"],"is_preprint":false},{"year":2020,"finding":"USP1 regulates AKT phosphorylation by stabilizing PHLPP1 (a phosphatase that dephosphorylates AKT); USP1 interacts with PHLPP1, and USP1 silencing decreases PHLPP1 half-life and increases AKT1 phosphorylation.","method":"Co-IP, GST pull-down, CHX stability assay, RNAi knockdown","journal":"Journal of cancer research and clinical oncology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and GST pulldown with CHX stability assay; single lab, multiple methods but no direct deubiquitination reconstitution","pmids":["22426999"],"is_preprint":false},{"year":2021,"finding":"Crystal structures of human USP1-UAF1 with and without ubiquitin, and cryo-EM of USP1-UAF1 bound to monoubiquitinated FANCI-FANCD2, reveal plasticity in USP1, an extensive interface between UAF1 and FANCI required for substrate recognition, and USP1-UAF1-driven conformational changes in the FANCI-FANCD2 substrate during deubiquitination. Mutagenesis confirmed the UAF1-FANCI interface.","method":"X-ray crystallography, cryo-EM, site-directed mutagenesis, biochemical deubiquitination assay","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution structures plus mutagenesis validation and biochemical assays; multiple orthogonal methods in a single rigorous study","pmids":["33795880"],"is_preprint":false},{"year":2021,"finding":"Insert L1 in USP1 is a central regulatory hub: it limits intrinsic USP1 activity (together with insert L3), and this inhibition is relieved by UAF1 binding; insert L1 also conveys substrate-dependent (DNA and PCNA) increases in USP1 activity independently of UAF1-mediated activation.","method":"Biochemical activity assays with USP1 insert deletion mutants, UAF1 activation assays, DNA/PCNA stimulation assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple deletion mutants separating two regulatory mechanisms; single lab with multiple orthogonal biochemical methods","pmids":["33619839"],"is_preprint":false},{"year":2021,"finding":"USP1 deubiquitinates and stabilizes BCAT2 at the K229 site; BCAA increases USP1 protein at the translational level via the GCN2-eIF2α pathway, forming a feedforward axis that promotes pancreatic cancer development.","method":"DUB library screen, Co-IP, ubiquitination assay (site-specific), in vitro deubiquitination, in vivo orthotopic mouse model","journal":"National science review","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro deubiquitination assay and site-specific mapping plus in vivo model; single lab, multiple orthogonal methods","pmids":["35663242"],"is_preprint":false},{"year":2021,"finding":"USP1 interacts with and deubiquitinates EZH2, stabilizing it downstream of a β-catenin/TCF4 transcriptional axis (β-catenin/TCF4 → USP1 transcription → EZH2 stabilization → H3K27me3-mediated gene repression) to drive glioma tumorigenesis.","method":"Co-IP, ubiquitination assay, ChIP, reporter assay, RNAi/knockdown, in vivo tumor model","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, ubiquitination assay, and ChIP with in vivo functional readout; single lab, multiple methods","pmids":["30425057"],"is_preprint":false},{"year":2021,"finding":"The molecular chaperone GRP75 recruits USP1 to inhibit K48-linked polyubiquitination of SIX1, forming a GRP75-USP1-SIX1 trimeric complex; the C-terminus of GRP75 (433–679 aa peptide-binding domain) is required for complex formation.","method":"Co-IP, ubiquitination assay, domain mapping (deletion mutants), in vitro and in vivo tumor models","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping and ubiquitination assay; single lab, two orthogonal methods","pmids":["34079090"],"is_preprint":false},{"year":2022,"finding":"USP1 inhibition causes accumulation of mono- and polyubiquitinated PCNA and leads to reduced PCNA protein levels; ectopic expression of WT PCNA (but not ubiquitin-dead K164R PCNA) reverses USP1 inhibitor sensitivity. RAD18 and UBE2K (promoting PCNA mono- and polyubiquitination respectively) are mediators of USP1 dependency in BRCA1/2-mutant tumors.","method":"Genome-wide CRISPR-Cas9 screen, PCNA ubiquitination assay, rescue with PCNA K164R mutant, cell viability assay","journal":"Molecular cancer therapeutics","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased CRISPR screen plus mechanistic rescue with PCNA mutant and two independent gene validations (RAD18, UBE2K); multiple orthogonal methods","pmids":["36228090"],"is_preprint":false},{"year":2022,"finding":"Cells with an autocleavage-defective USP1 mutant (still able to deubiquitinate PCNA) experience more replication fork-stalling and premature fork termination; super-resolution microscopy and live-cell single-molecule tracking show that USP1 autocleavage is required for its proper recycling from sites of active DNA synthesis ('USP1-trapping'); the metalloprotease Spartan facilitates removal of USP1 molecules from DNA to counteract USP1-trapping cytotoxicity.","method":"Autocleavage-defective mutant knock-in, super-resolution microscopy, live-cell single-molecule tracking, DNA fiber assay, Spartan epistasis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple advanced microscopy methods, single-molecule tracking, DNA fiber assay, and genetic epistasis in a single study; multiple orthogonal methods","pmids":["35365626"],"is_preprint":false},{"year":2022,"finding":"Cryo-EM at 2.5 Å resolution of the USP1-UAF1-ML323 inhibitor complex reveals that ML323 binds to a cryptic hydrophobic site in USP1, disrupting part of its hydrophobic core and inducing conformational changes in secondary structure that subtly rearrange the active site to achieve inhibition.","method":"Cryo-EM structure determination, with and without inhibitor","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution cryo-EM structure with direct visualization of inhibitor binding mode and structural mechanism; single lab but rigorous structural study","pmids":["36170365"],"is_preprint":false},{"year":2022,"finding":"USP1 interacts with MAX and maintains MAX protein stability through deubiquitination; this promotes transcription of MYC target genes and contributes to chemotherapy resistance in B-cell lymphoma.","method":"Co-IP, ubiquitination assay, RNAi/shRNA knockdown, in vivo mouse lymphoma model","journal":"Leukemia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay and in vivo mouse model; single lab, two orthogonal methods","pmids":["36352191"],"is_preprint":false},{"year":2022,"finding":"USP1 identifies MAST1 as a substrate; USP1 interacts with MAST1, prevents its K48-linked polyubiquitination, and extends its half-life, thereby stabilizing MAST1 and promoting MAST1-mediated MEK1 activation and cisplatin resistance.","method":"CRISPR/Cas9 genome-wide dual screen, Co-IP, in vitro deubiquitination assay, ubiquitination linkage analysis (K48), half-life analysis, xenograft mouse model","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro deubiquitination assay plus Co-IP, ubiquitin linkage analysis, and in vivo mouse model; single lab, multiple orthogonal methods","pmids":["35966591"],"is_preprint":false},{"year":2018,"finding":"N-terminus of USP1 contains a FANCD2-specific binding sequence required for deubiquitination of K561 on FANCD2, whereas the N-terminus is not required for PCNA or FANCI deubiquitination; the N-terminus of USP1 is sufficient to engineer substrate specificity into a more promiscuous USP.","method":"Reconstituted in vitro deubiquitination of purified monoubiquitinated FANCD2/FANCI/PCNA, N-terminal deletion and chimera mutants","journal":"Life science alliance","confidence":"High","confidence_rationale":"Tier 1 / Moderate — fully reconstituted in vitro deubiquitination with purified substrates and multiple deletion/chimera mutants; direct mechanistic determination of substrate specificity","pmids":["30456385"],"is_preprint":false},{"year":2015,"finding":"USP1 is phosphorylated by CDKs in mitosis, and this phosphorylation may prevent premature APC/C(Cdh1)-mediated degradation during normal cell cycle progression. The S313 phosphorylation site is not critical for PCNA deubiquitination or UAF1 binding in a cellular environment. The UAF1-binding site in USP1 maps to residues 420–520 (Fingers subdomain). Autocleavage of USP1 can occur in cis and is disrupted by the cancer-associated mutation L669P.","method":"Structure-function analysis with USP1 mutants (S313A, S313D, GG/AA, cancer-associated mutations), nuclear relocation assay, PCNA deubiquitination assay, Co-IP","journal":"Molecular cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mutant constructs with two orthogonal functional assays; single lab","pmids":["25744535"],"is_preprint":false},{"year":2011,"finding":"USP1 protein levels are phosphorylated by CDKs during mitosis, and this phosphorylation event may prevent premature degradation by APC/C(Cdh1) during normal cell cycle progression.","method":"Cell cycle synchronization, phosphorylation assay, CDK inhibitor treatment","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — cell-cycle synchronization with CDK inhibitors and phosphorylation analysis; single lab, single main method","pmids":["22101265"],"is_preprint":false},{"year":2016,"finding":"USP1 autocleavage (at the GG/AA diglycine motif) is specifically required for USP1 function in ICL repair but not UV repair; an autocleavage-defective mutant Usp1(GG/AA) corrects monoubiquitinated Fancd2 levels and UV resistance in Usp1−/− MEFs, but only partially rescues MMC sensitivity and shows defective Fancd2 foci formation and HR.","method":"Autocleavage mutant knock-in in Usp1−/− MEFs, MMC/UV sensitivity assay, Fancd2 foci analysis, HR assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — separation-of-function mutant with multiple DNA repair pathway readouts; single lab, multiple assays","pmids":["26783108"],"is_preprint":false},{"year":2019,"finding":"TonEBP regulates PCNA polyubiquitination by sequentially recruiting E3 ligase SHPRH and then deubiquitinase USP1 to DNA damage sites; the Rel-homology domain of TonEBP is essential for interaction with both SHPRH and USP1, PCNA polyubiquitination, and cell survival after DNA damage.","method":"Co-IP, recruitment assay (chromatin/DNA damage foci), RNAi knockdown, domain deletion mapping","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping and chromatin recruitment assay plus functional readout; single lab, two orthogonal methods","pmids":["31376680"],"is_preprint":false},{"year":2020,"finding":"UAF1 deubiquitinates and stabilizes METTL3 by removing K48-linked polyubiquitination after spinal cord injury, and the USP1/UAF1 complex specifically binds METTL3 to maintain its stability.","method":"Co-IP, ubiquitination assay (K48-linked), conditional knockout, in vivo SCI model","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and conditional KO with in vivo model; single lab, multiple methods","pmids":["36653190"],"is_preprint":false},{"year":2021,"finding":"USP1 identifies ULK1 as a substrate, removing K63-linked ubiquitination from ULK1; USP1 depletion or inhibition causes ULK1 compartmentalization into a detergent-insoluble (urea-soluble) fraction enriched in SQSTM1/p62 and HDAC6, forming protein aggregates, and inhibits canonical autophagic flux while promoting an alternative lysosomal-mediated degradation route.","method":"Co-IP, ubiquitin linkage analysis (K63), cellular fractionation, immunofluorescence, RNAi knockdown, pimozide inhibition","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with K63 ubiquitin linkage specificity and fractionation/localization with functional autophagy readout; single lab, multiple orthogonal methods","pmids":["30335599"],"is_preprint":false},{"year":2016,"finding":"USP1 plays a role in regulating centrosome duplication; ectopic expression of catalytically active (but not C90S inactive) Usp1 induces centrosome amplification, abnormal mitotic spindles, chromosome missegregation, and aneuploidy. Loss of ID1 suppresses Usp1-induced centrosome amplification, placing ID1 downstream of USP1 in this process.","method":"Usp1 overexpression and C90S catalytic mutant, centrosome counting, mitotic spindle analysis, ID1 knockdown epistasis in Usp1−/− MEFs","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — catalytic mutant discrimination, epistasis with ID1, and cellular phenotype readouts; single lab, multiple methods","pmids":["26822809"],"is_preprint":false},{"year":2020,"finding":"USP1 interacts with TAZ/WWTR1 and increases TAZ protein stability by preventing its poly-ubiquitination; loss of USP1 reduces TAZ protein levels and decreases cell proliferation and migration of breast cancer cells.","method":"siRNA DUB library screen, Co-IP, ubiquitination assay, RNAi knockdown","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA screen with Co-IP validation and ubiquitination assay; single lab, multiple methods but no direct deubiquitination reconstitution","pmids":["33114077"],"is_preprint":false},{"year":2023,"finding":"USP1 interacts with the WW domain of TAZ and suppresses K11-linked polyubiquitination of TAZ to enhance TAZ stability and Hippo/TAZ signaling in HCC; USP1 depletion leads to decreased TAZ nuclear accumulation and downstream Hippo target gene expression.","method":"DUB siRNA screen, Co-IP, domain mapping (WW domain), ubiquitin linkage-specific assay (K11), RNAi knockdown, in vivo tumor model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and domain mapping plus in vivo model; single lab, multiple orthogonal methods","pmids":["37041150"],"is_preprint":false},{"year":2023,"finding":"USP1 interacts with PARP1 and removes the ubiquitin chain at K197 of PARP1 to prevent its proteasomal degradation; GCN5 acetyltransferase acetylates USP1 at K130, enhancing USP1-PARP1 affinity and further increasing PARP1 stabilization.","method":"Proteomics/ubiquitylome analysis, Co-IP, GST pull-down, immunofluorescence, deletion mutant mapping, in vitro/in vivo tumor models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics-based substrate identification with Co-IP/pulldown validation, site-specific ubiquitination and acetylation mapping; single lab, multiple orthogonal methods","pmids":["37821462"],"is_preprint":false},{"year":2024,"finding":"USP1 removes K63-linked polyubiquitin chains from PARP1 and controls PARP1 chromatin trapping and PARylation activity, thereby regulating sensitivity to PARP inhibitors.","method":"Co-IP, ubiquitin linkage analysis (K63), chromatin trapping assay, PARylation assay, RNAi/knockout","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with linkage-specific assay and direct functional readouts (trapping, PARylation); single lab, multiple orthogonal methods","pmids":["39536107"],"is_preprint":false},{"year":2024,"finding":"USP1 inhibition promotes accumulation of ssDNA gaps at replication forks in BRCA1-deficient cells via RAD18-dependent PCNA monoubiquitination; RAD18 knockdown causes USP1 inhibitor resistance and suppresses ssDNA gap accumulation, defining RAD18-dependent PCNA ubiquitination as the proximal mediator of USP1 dependency.","method":"ssDNA gap assay, PCNA ubiquitination assay, RAD18 knockdown rescue, patient-derived organoid assay","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic epistasis (RAD18 rescue), functional ssDNA gap biomarker, validated in multiple model systems including patient-derived organoids","pmids":["38885312"],"is_preprint":false},{"year":2024,"finding":"USP1 inhibitor KSQ-4279 (RO7623066) binds to the same cryptic hydrophobic site as ML323 in USP1 but disrupts the protein structure in subtly different ways; inhibitor binding drives a substantial increase in USP1 thermal stability, mediated through filling a hydrophobic tunnel-like pocket.","method":"Cryo-EM structure determination, biochemical assays, thermal stability assay","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure with biochemical validation; single lab but direct structural mechanism","pmids":["39190802"],"is_preprint":false},{"year":2024,"finding":"USP1 depletion suppresses expansion of PRIMPOL-generated ssDNA gaps by preventing MRE11 and EXO1 nuclease-mediated bidirectional gap expansion; USP1's role in promoting gap accumulation is linked to its deubiquitination of PCNA, as PCNA ubiquitination prevents gap accumulation during replication.","method":"USP1 depletion, PCNA ubiquitination assay, MRE11/EXO1 epistasis, ssDNA gap assay, DSB assay","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi depletion with multiple epistasis experiments and direct gap/DSB readouts; single lab, multiple methods","pmids":["38180818"],"is_preprint":false},{"year":2023,"finding":"USP1 interacts with Aurora B and deubiquitinates it, maintaining Aurora B stability and mediating T-ALL glucocorticoid resistance; ALKBH5 enhances USP1 expression by reducing m6A modification on USP1 mRNA.","method":"Co-IP, ubiquitination assay, in vivo mouse model, ALKBH5 knockdown/overexpression, m6A assay","journal":"Molecular carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with ubiquitination assay and in vivo model; single lab, multiple methods","pmids":["34169564"],"is_preprint":false},{"year":2023,"finding":"USP1 interacts with PLK1, deubiquitinates it, and increases its stability; PLK1 in turn regulates LDHA expression to promote aerobic glycolysis in T-ALL cells.","method":"Co-IP, ubiquitination assay, overexpression/knockdown epistasis, metabolic assay (lactate)","journal":"Blood advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay and epistasis with LDHA rescue; single lab, multiple methods","pmids":["36912760"],"is_preprint":false},{"year":2021,"finding":"USP1 deubiquitinates RPS16 at K48-linked ubiquitin chains to stabilize it; USP1-C90A catalytic mutant fails to reduce K48-linked ubiquitinated RPS16, confirming enzymatic activity requirement. USP1 depletion mimics RPS16 deficiency in inhibiting HCC growth and metastasis.","method":"Mass spectrometry, Co-IP, ubiquitination assay, catalytic mutant (C90A), rescue experiments, xenograft mouse model","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based substrate identification, Co-IP, catalytic mutant validation; single lab, multiple orthogonal methods","pmids":["34154657"],"is_preprint":false},{"year":2023,"finding":"USP1 deubiquitinates and stabilizes C/EBPβ; USP1 catalytic mutant fails to affect C/EBPβ stability or ubiquitination, demonstrating enzymatic activity requirement. USP1 directly interacts with C/EBPβ and its upregulation during adipocyte differentiation promotes lipid accumulation.","method":"Co-IP, ubiquitination assay, catalytic mutant (C90A), overexpression/knockdown, USP1 inhibitor (ML323) in vivo mouse model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with catalytic mutant discrimination and in vivo mouse metabolic model; single lab, multiple orthogonal methods","pmids":["38012162"],"is_preprint":false},{"year":2024,"finding":"USP1 removes SAR1A K27-linked oligo-ubiquitination, thereby blocking SAR1A-mediated STING-COP-II transport complex assembly and STING trafficking from ER to Golgi; USP1 inhibition sustains SAR1A ubiquitination and enhances cGAS-STING pathway activation and Type I IFN production.","method":"Chemical screen (DUB inhibitors), Co-IP, ubiquitination linkage analysis (K27), STING trafficking assay, IFN reporter assay, USP1 inhibitor (ML323)","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and direct STING trafficking functional readout; single lab, multiple orthogonal methods","pmids":["39976106"],"is_preprint":false},{"year":2024,"finding":"UAF1-USP1 deubiquitinase complex interacts with cGAS, selectively cleaves K48-linked polyubiquitination of cGAS, and stabilizes cGAS protein expression in macrophages; this provides positive feedback for cGAS-dependent antiviral type I IFN responses.","method":"Co-IP, ubiquitin linkage analysis (K48), Uaf1 conditional knockout, ML323 inhibitor, IFN reporter assay in vivo","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with K48-specific ubiquitination assay and conditional KO with in vivo antiviral readout; single lab, multiple methods","pmids":["38054892"],"is_preprint":false},{"year":2021,"finding":"USP1 deubiquitinates and stabilizes TBLR1, and this promotes survival of circulating tumor cells in hepatocellular carcinoma by regulating Wnt signaling.","method":"Co-IP, ubiquitination assay, USP1 knockout, in vitro and in vivo CTC survival assay","journal":"Frontiers in oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP with ubiquitination assay; single lab, single main deubiquitination method","pmids":["33102219"],"is_preprint":false},{"year":2023,"finding":"USP1 interacts with Bcr-Abl oncoprotein in the nucleus of K562 CML cells; inhibition of USP1 activity by ML323 reduces Bcr-Abl protein levels.","method":"Co-IP, Western blot, confocal microscopy, USP1 inhibitor treatment","journal":"Experimental oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP and confocal colocalization; single lab, single method; mechanistic relationship not fully established","pmids":["32602291"],"is_preprint":false},{"year":2021,"finding":"USP1-WDR48 (UAF1) complex deubiquitinates TAK1 in vitro, reducing its polyubiquitination and stabilizing it, thereby enhancing TGF-β-mediated EMT and migration in TNBC cells.","method":"Co-IP, in vitro ubiquitination/deubiquitination assay, RNAi knockdown","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — in vitro deubiquitination assay plus Co-IP; single lab, single in vitro method without full reconstitution","pmids":["33461373"],"is_preprint":false},{"year":2025,"finding":"USP1 can be harnessed as a deubiquitinase-targeting chimera (DUBTAC) anchor; USP1-recruiting DUBTACs stabilize CFTR and the tumor suppressor UTX in a USP1-dependent manner, demonstrating that USP1's deubiquitinating activity can be re-directed to non-natural substrates via bifunctional molecules.","method":"DUBTAC chemical biology, protein stability assay, knockdown epistasis (USP1 depletion reverses stabilization), cellular assays","journal":"Journal of the American Chemical Society","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — USP1 dependency confirmed by knockdown rescue with two independent target proteins; single lab, multiple orthogonal methods","pmids":["40252079"],"is_preprint":false},{"year":2022,"finding":"USP1 deubiquitinates and stabilizes survivin/BIRC5 in renal cell carcinoma and Ewing sarcoma; USP1 inhibition downregulates survivin by removing ubiquitin, and ML323 also upregulates DR5 by decreasing miR-216a-5p.","method":"Co-IP, ubiquitination assay, siRNA knockdown, USP1 inhibitor (ML323/pimozide), in vivo mouse xenograft","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with ubiquitination assay and in vivo xenograft; single lab, multiple methods","pmids":["36153316"],"is_preprint":false},{"year":2020,"finding":"USP1 interacts with ERα and promotes ERα stability by inhibiting ERα K48-linked poly-ubiquitination in breast cancer cells.","method":"DUB siRNA library screen, Co-IP, ubiquitination assay (K48-linked), RNAi knockdown","journal":"Journal of Cancer","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP with ubiquitination assay from siRNA screen; single lab, single main method","pmids":["33123289"],"is_preprint":false},{"year":2023,"finding":"USP1 stabilizes NLRP3 and AIM2 inflammasome components through deubiquitination, promoting pyroptosis in thyroid follicular cells; USP1 also facilitates p65 nuclear translocation to modulate NLRP3 transcription.","method":"Co-IP, ubiquitination assay, USP1 knockdown/inhibition, caspase-1/GSDMD-N assay, mouse HT model, AIM2 rescue epistasis","journal":"Molecular medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP with ubiquitination assay and functional pyroptosis readouts; single lab, limited mechanistic detail in abstract","pmids":["39134949"],"is_preprint":false},{"year":2025,"finding":"USP1 deubiquitinates and stabilizes KIF11 at the K77 site; high interstitial fluid pressure stabilizes KIF11 in HCC through USP1-mediated deubiquitination. USP1 inhibition by ML323 reduces KIF11 protein levels and suppresses tumor progression in mice.","method":"Co-IP, proteomic analysis, ubiquitination assay (site-specific K77), in vivo orthotopic mouse model, USP1 inhibitor","journal":"Journal of translational medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP with proteomics-based identification and site-specific ubiquitination; single lab, in vivo model but limited mechanistic reconstitution","pmids":["39810156"],"is_preprint":false}],"current_model":"USP1 is a nuclear cysteine protease deubiquitinase that functions in complex with its obligatory activator UAF1 (WDR48); UAF1 binding lowers the pKa of the catalytic histidine to facilitate general base catalysis at neutral pH, and the regulatory insert L1 serves as an allosteric hub controlling both UAF1-mediated and substrate (DNA/PCNA)-mediated activation. USP1-UAF1 removes monoubiquitin from FANCD2 (at K561), FANCI, and PCNA (at K164) to regulate Fanconi anemia interstrand crosslink repair, translesion synthesis, and homologous recombination, with FANCD2 deubiquitination additionally requiring DNA binding and conformational changes in the substrate as revealed by cryo-EM; USP1 undergoes autocleavage at a conserved diglycine motif to allow its own recycling from replication forks (counteracted by the metalloprotease Spartan), and is degraded in G1 by APC/C(Cdh1) while CDK-mediated phosphorylation in mitosis prevents premature destruction. Beyond DNA repair, USP1 deubiquitinates and stabilizes a broad set of substrates—including ID1/2/3, Akt, PCNA, TBK1, cGAS, PARP1, EZH2, Snail, TAZ, C/EBPβ, CHK1, ULK1, MAST1, and others—placing it at the intersection of DNA damage responses, stem cell maintenance, immune signaling, autophagy, and metabolic regulation."},"narrative":{"mechanistic_narrative":"USP1 is a nuclear cysteine-protease deubiquitinase that operates as a central regulator of the DNA damage response, removing monoubiquitin from FANCD2 (at K561) and PCNA (at K164) to control Fanconi anemia interstrand-crosslink repair, translesion synthesis, and homologous recombination [PMID:15694335, PMID:19217432, PMID:30456385]. It functions as an obligate heterodimer with the activator UAF1/WDR48, which binds a conserved motif in the USP1 Fingers subdomain and activates catalysis by lowering the pKa of the catalytic histidine to enable general-base catalysis at neutral pH, with the regulatory insert L1 serving as an allosteric hub that integrates both UAF1-mediated and substrate (DNA/PCNA)-driven activation [PMID:22439892, PMID:22701671, PMID:33619839]. Substrate engagement is sculpted further by accessory factors and intrinsic features: a USP1 N-terminal sequence confers FANCD2 specificity, DNA binding by UAF1 (or substitutively by RAD51AP1) is required for efficient FANCD2 deubiquitination, and ELG1 directs the complex specifically toward PCNA [PMID:20147293, PMID:31253762, PMID:30456385]. Cryo-EM of USP1-UAF1 bound to monoubiquitinated FANCI-FANCD2 shows that catalysis is accompanied by UAF1-FANCI interface contacts and conformational changes in the substrate [PMID:33795880]. USP1 abundance and chromatin residence are tightly gated: it is degraded in G1 by APC/C(Cdh1) to permit PCNA monoubiquitination, protected in mitosis by CDK phosphorylation, and recycled from active replication forks via autocleavage at a diglycine motif, with the metalloprotease Spartan counteracting USP1 trapping [PMID:21768287, PMID:23159736, PMID:35365626, PMID:25744535]. Because persistent PCNA monoubiquitination and RAD18-dependent ssDNA gap accumulation are lethal in BRCA1/2-deficient cells, USP1 is a synthetic-lethal target, and selective inhibitors (ML323, KSQ-4279) act through a cryptic hydrophobic pocket that rearranges the active site [PMID:30576655, PMID:36228090, PMID:36170365, PMID:38885312, PMID:39190802]. Beyond DNA repair, USP1-UAF1 deubiquitinates and stabilizes ID1/2/3 to maintain stem-like states and centrosome control, and stabilizes substrates spanning innate immune signaling (TBK1, cGAS), autophagy (ULK1), and transcriptional/metabolic regulators, placing it at the intersection of genome maintenance, stemness, and signaling [PMID:21925315, PMID:29138248, PMID:30335599, PMID:26822809, PMID:38054892].","teleology":[{"year":1998,"claim":"Established that USP1 is a bona fide ubiquitin-specific protease, defining its core biochemical identity before any cellular role was known.","evidence":"recombinant USP1 cleaving Ub-beta-galactosidase in vitro","pmids":["9806842"],"confidence":"High","gaps":["No physiological substrate identified","No regulatory partner or cellular pathway known at this stage"]},{"year":2005,"claim":"Identified the first physiological substrate and pathway by showing USP1 deubiquitinates monoubiquitinated FANCD2, linking the enzyme to Fanconi anemia crosslink repair.","evidence":"RNAi screen, Co-IP, chromatin fractionation in human cells","pmids":["15694335"],"confidence":"High","gaps":["Did not define the activator requirement for catalysis","Mechanism of substrate recognition unresolved"]},{"year":2009,"claim":"Confirmed in an organism that USP1 acts downstream in the FA pathway and is required for HR, moving beyond cell-line correlation to genetic epistasis.","evidence":"Usp1 mouse knockout, MEF analysis, Usp1/Fancd2 double KO epistasis","pmids":["19217432"],"confidence":"High","gaps":["Molecular basis of HR defect not separated from FANCD2 deubiquitination","Perinatal lethality mechanism not dissected"]},{"year":2011,"claim":"Resolved how USP1 activity is restricted to the correct cell-cycle window and how substrate targeting is diversified, and broadened its substrate range to ID proteins and CHK1.","evidence":"APC/C(Cdh1)-mediated G1 degradation assays, ELG1-directed PCNA deubiquitination, ID1/2/3 and CHK1 stability assays, DT40 HR knockouts","pmids":["21768287","20147293","21925315","21389083","21482670"],"confidence":"High","gaps":["Structural basis of UAF1/ELG1 specificity not yet defined","ID-protein stabilization mechanism in stemness not generalized across tissues"]},{"year":2012,"claim":"Defined the enzymatic and regulatory mechanism of the complex—UAF1 activation chemistry, nuclear import, and autocleavage-coupled turnover—explaining how catalysis and protein recycling are controlled.","evidence":"in vitro kinetics/proton inventory, NLS mutagenesis and relocation, autocleavage and N-end-rule degradation assays","pmids":["22439892","22701671","23159736"],"confidence":"High","gaps":["Allosteric route from UAF1 to active site not visualized structurally","Physiological trigger of autocleavage at forks unclear at this stage"]},{"year":2014,"claim":"Provided pharmacological proof that USP1-UAF1 deubiquitination is required for the PCNA/FANCD2 DNA damage response, establishing the complex as a druggable node.","evidence":"selective inhibitor ML323 with DUB selectivity profiling and cellular ubiquitination readouts","pmids":["24531842"],"confidence":"High","gaps":["Inhibitor binding mode unknown","Therapeutic context for inhibition not yet defined"]},{"year":2016,"claim":"Connected USP1 catalytic activity to replication-fork protection and genome stability, showing DNA binding and autocleavage are functionally required and that fork-associated PCNA-Ub persistence kills BRCA1-deficient cells.","evidence":"DNA-binding and truncation mutants, DNA fiber fork-protection assays, autocleavage separation-of-function mutants, RAD51AP1 interactome, centrosome assays","pmids":["30576655","26783108","27463890","26822809"],"confidence":"High","gaps":["Distinction between catalytic and scaffolding contributions to HR incompletely resolved","Mechanism coupling DNA binding to activity not yet structural"]},{"year":2019,"claim":"Reconstituted FANCD2 deubiquitination from purified components to establish that DNA binding by UAF1 (or RAD51AP1) is mechanistically required for efficient substrate processing.","evidence":"fully reconstituted in vitro deubiquitination with DNA-binding mutants plus cellular validation","pmids":["31253762"],"confidence":"High","gaps":["Substrate conformational requirements not yet visualized","How DNA binding is coupled to catalysis at atomic level unresolved"]},{"year":2021,"claim":"Delivered the structural and allosteric framework—crystal/cryo-EM structures and the insert L1 regulatory hub—explaining how UAF1, substrate, and DNA converge to control USP1 activity.","evidence":"X-ray and cryo-EM of USP1-UAF1 and the FANCI-FANCD2 complex, insert-deletion biochemical activity assays","pmids":["33795880","33619839"],"confidence":"High","gaps":["Dynamics of insert L1 allostery in cells not directly observed","Structural basis of PCNA versus FANCD2 selectivity not co-resolved"]},{"year":2022,"claim":"Defined the proximal mediators of USP1 synthetic lethality and visualized inhibitor mechanism, mechanistically grounding USP1 inhibitors as cancer therapeutics.","evidence":"genome-wide CRISPR screen with PCNA K164R rescue (RAD18/UBE2K), live-cell single-molecule tracking of autocleavage-dependent recycling with Spartan epistasis, cryo-EM of ML323 cryptic-site binding","pmids":["36228090","35365626","36170365"],"confidence":"High","gaps":["Determinants of which BRCA-deficient tumors respond not fully defined","Resistance mechanisms incompletely mapped"]},{"year":2024,"claim":"Linked USP1 dependency to a measurable ssDNA-gap phenotype and refined the medicinal-chemistry basis of clinical-stage inhibitors.","evidence":"ssDNA gap assays with RAD18 and MRE11/EXO1 epistasis, patient-derived organoids, cryo-EM of KSQ-4279 binding with thermal-stability profiling","pmids":["38885312","38180818","39190802"],"confidence":"High","gaps":["Biomarker translation to patient selection not established in the corpus","Combination strategies not mechanistically resolved here"]},{"year":null,"claim":"It remains unresolved how USP1 substrate selectivity and ubiquitin-linkage specificity are determined across its large non-DNA-repair substrate set, and which of these many reported substrates reflect direct, physiologically dominant deubiquitination events.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Most non-canonical substrate studies are single-lab Co-IP/ubiquitination assays without reconstitution","Linkage specificity (K48/K63/K11/K27) varies by substrate and lacks a unifying structural rationale","Tissue- and context-dependence of substrate choice unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,5,9,23,33]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[2,9,24]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[13,20,24]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,24]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,10]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1,13]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,12,28,45]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[6,13,29,47]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6,34,40]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[8,9,23]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[16,53,52]}],"complexes":["USP1-UAF1 (WDR48) deubiquitinase complex"],"partners":["UAF1","FANCD2","FANCI","PCNA","ELG1","RAD51AP1","ID1","TBK1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O94782","full_name":"Ubiquitin carboxyl-terminal hydrolase 1","aliases":["Deubiquitinating enzyme 1","hUBP","Ubiquitin thioesterase 1","Ubiquitin-specific-processing protease 1"],"length_aa":785,"mass_kda":88.2,"function":"Negative regulator of DNA damage repair which specifically deubiquitinates monoubiquitinated FANCD2 (PubMed:15694335). Also involved in PCNA-mediated translesion synthesis (TLS) by deubiquitinating monoubiquitinated PCNA (PubMed:16531995, PubMed:20147293). Has almost no deubiquitinating activity by itself and requires the interaction with WDR48 to have a high activity (PubMed:18082604, PubMed:26388029)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/O94782/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/USP1","classification":"Not Classified","n_dependent_lines":247,"n_total_lines":1208,"dependency_fraction":0.20447019867549668},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000162607","cell_line_id":"CID000804","localizations":[{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"WDR48","stoichiometry":10.0},{"gene":"KPNB1","stoichiometry":0.2},{"gene":"HIBADH","stoichiometry":0.2},{"gene":"UBE3B","stoichiometry":0.2},{"gene":"KPNA1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000804","total_profiled":1310},"omim":[{"mim_id":"620846","title":"N-TERMINAL GLUTAMINE AMIDASE 1; NTAQ1","url":"https://www.omim.org/entry/620846"},{"mim_id":"616086","title":"SprT-LIKE N-TERMINAL DOMAIN PROTEIN; SPRTN","url":"https://www.omim.org/entry/616086"},{"mim_id":"612492","title":"UBIQUITIN-SPECIFIC PROTEASE 30; USP30","url":"https://www.omim.org/entry/612492"},{"mim_id":"612167","title":"WD REPEAT-CONTAINING PROTEIN 48; WDR48","url":"https://www.omim.org/entry/612167"},{"mim_id":"610186","title":"UBIQUITIN-SPECIFIC PEPTIDASE 17-LIKE FAMILY MEMBER 2; USP17L2","url":"https://www.omim.org/entry/610186"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/USP1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O94782","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O94782","model_url":"https://alphafold.ebi.ac.uk/files/AF-O94782-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O94782-F1-predicted_aligned_error_v6.png","plddt_mean":59.59},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=USP1","jax_strain_url":"https://www.jax.org/strain/search?query=USP1"},"sequence":{"accession":"O94782","fasta_url":"https://rest.uniprot.org/uniprotkb/O94782.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O94782/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O94782"}},"corpus_meta":[{"pmid":"15694335","id":"PMC_15694335","title":"The deubiquitinating enzyme USP1 regulates the Fanconi anemia pathway.","date":"2005","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/15694335","citation_count":488,"is_preprint":false},{"pmid":"24531842","id":"PMC_24531842","title":"A selective USP1-UAF1 inhibitor links deubiquitination to DNA damage responses.","date":"2014","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/24531842","citation_count":227,"is_preprint":false},{"pmid":"21925315","id":"PMC_21925315","title":"USP1 deubiquitinates ID proteins to preserve a mesenchymal stem cell program in osteosarcoma.","date":"2011","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21925315","citation_count":224,"is_preprint":false},{"pmid":"19217432","id":"PMC_19217432","title":"Inactivation of murine Usp1 results in genomic instability and a Fanconi anemia phenotype.","date":"2009","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/19217432","citation_count":211,"is_preprint":false},{"pmid":"22118673","id":"PMC_22118673","title":"Selective and cell-active inhibitors of the USP1/ UAF1 deubiquitinase complex reverse cisplatin resistance in non-small cell lung cancer cells.","date":"2011","source":"Chemistry & biology","url":"https://pubmed.ncbi.nlm.nih.gov/22118673","citation_count":194,"is_preprint":false},{"pmid":"30576655","id":"PMC_30576655","title":"USP1 Is Required for Replication Fork Protection in BRCA1-Deficient Tumors.","date":"2018","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/30576655","citation_count":158,"is_preprint":false},{"pmid":"24130053","id":"PMC_24130053","title":"Small-molecule inhibitors of USP1 target ID1 degradation in leukemic cells.","date":"2013","source":"Molecular cancer therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/24130053","citation_count":156,"is_preprint":false},{"pmid":"23937906","id":"PMC_23937906","title":"USP1 deubiquitinase: cellular functions, regulatory mechanisms and emerging potential as target in cancer therapy.","date":"2013","source":"Molecular 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journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V","url":"https://pubmed.ncbi.nlm.nih.gov/37949326","citation_count":9,"is_preprint":false},{"pmid":"40252079","id":"PMC_40252079","title":"Harnessing the Deubiquitinase USP1 for Targeted Protein Stabilization.","date":"2025","source":"Journal of the American Chemical Society","url":"https://pubmed.ncbi.nlm.nih.gov/40252079","citation_count":8,"is_preprint":false},{"pmid":"28302046","id":"PMC_28302046","title":"The Role of the Complex USP1/WDR48 in Differentiation and Proliferation Processes in Cancer Stem Cells.","date":"2017","source":"Current stem cell research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/28302046","citation_count":8,"is_preprint":false},{"pmid":"36240066","id":"PMC_36240066","title":"Regulation of CHK1 inhibitor resistance by a c-Rel and USP1 dependent pathway.","date":"2022","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/36240066","citation_count":8,"is_preprint":false},{"pmid":"32546349","id":"PMC_32546349","title":"USP1 inhibitor ML323 enhances osteogenic potential of human dental pulp stem cells.","date":"2020","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/32546349","citation_count":8,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49491,"output_tokens":14805,"usd":0.185274,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":27224,"output_tokens":4319,"usd":0.122048,"stage2_stop_reason":"end_turn"},"total_usd":0.307322,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"USP1 is a deubiquitinating enzyme that physically associates with FANCD2 and deubiquitinates monoubiquitinated FANCD2; inhibition of USP1 leads to hyperaccumulation of monoubiquitinated FANCD2, and USP1 co-localizes with FANCD2 in chromatin after DNA damage.\",\n      \"method\": \"RNAi screen, Co-IP, chromatin fractionation, chromosomal aberration assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, colocalization, and functional RNAi knockdown with defined phenotypic readout; replicated extensively by multiple subsequent labs\",\n      \"pmids\": [\"15694335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Targeted deletion of mouse Usp1 results in elevated perinatal lethality, male infertility, crosslinker hypersensitivity, and an FA phenotype; Usp1−/− MEFs show heightened monoubiquitinated Fancd2 in chromatin, impaired Fancd2 foci assembly, and a defect in homologous recombination repair. Double knockout of Usp1 and Fancd2 produces a more severe phenotype than either single knockout, placing Usp1 downstream in the FA pathway.\",\n      \"method\": \"Targeted gene knockout (mouse), MEF analysis, epistasis (double KO), chromosomal aberration assay, HR repair assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular and organismal phenotype plus genetic epistasis, replicated in multiple follow-up studies\",\n      \"pmids\": [\"19217432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"USP1 encodes a 785-amino-acid ubiquitin-specific protease; recombinant USP1 protein displays genuine UBP deubiquitinase activity, correctly cleaving Ub-beta-galactosidase to produce ubiquitin and beta-galactosidase.\",\n      \"method\": \"Recombinant protein expression, in vitro enzymatic cleavage assay\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro reconstitution of enzymatic activity; single lab but unambiguous biochemical assay\",\n      \"pmids\": [\"9806842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Human ELG1 interacts with the USP1-UAF1 deubiquitinase complex and specifically directs it toward PCNA deubiquitination (but not FANCD2 deubiquitination); a conserved N-terminal domain of ELG1 is required for USP1-UAF1 interaction and PCNA monoubiquitination downregulation.\",\n      \"method\": \"Co-IP, RNAi knockdown, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interactions mapped with domain deletions plus functional RNAi readout; single lab, two orthogonal methods\",\n      \"pmids\": [\"20147293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP1 acts in complex with UAF1 to promote homologous recombination (HR)-mediated double-strand break repair; USP1/UAF1-deficient chicken DT40 cells show sensitivity to camptothecin and PARP inhibitors, and disruption of NHEJ in UAF1-deficient cells restores resistance, indicating that USP1/UAF1 promotes HR at least partly by suppressing NHEJ.\",\n      \"method\": \"Gene knockout in chicken DT40 cells, drug sensitivity assay, epistasis with NHEJ disruption\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockouts with multiple drug sensitivity readouts and epistasis analysis; multiple orthogonal lines of evidence\",\n      \"pmids\": [\"21482670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP1 deubiquitinates ID1, ID2, and ID3 proteins (inhibitors of DNA binding), thereby stabilizing them and promoting a stem cell-like mesenchymal state in osteosarcoma; USP1 knockdown precipitates ID protein destabilization, cell-cycle arrest, and osteogenic differentiation.\",\n      \"method\": \"Co-IP, ubiquitination assay, RNAi knockdown, protein stability assay, mouse knockout phenotype (osteopenia)\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, in vivo deubiquitination assay, RNAi with differentiation phenotype, and KO mouse with bone phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"21925315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP1 is degraded in G1 phase via APC/C(Cdh1)-mediated ubiquitination; low USP1 levels in G1 are required to permit PCNA monoubiquitination in response to UV damage; expression of a degradation-resistant USP1 mutant inhibits PCNA monoubiquitination during G1, compromising translesion synthesis polymerase recruitment.\",\n      \"method\": \"Cell-cycle synchronization, protein stability assay, APC/C(Cdh1) substrate analysis, PCNA ubiquitination assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-cycle-specific degradation shown with synchronized cells, degradation-resistant mutant used as functional tool with defined molecular readout; two orthogonal methods\",\n      \"pmids\": [\"21768287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP1 depletion stimulates DDB1-dependent degradation of phosphorylated CHK1; USP1 maintains total and phosphorylated CHK1 levels in response to genotoxic stress, both in a FANCD2-monoubiquitination-dependent and -independent manner, placing USP1 in a feedback circuit that downregulates CHK1 after DNA damage.\",\n      \"method\": \"RNAi knockdown, protein stability assay, epistasis with monoubiquitinated FANCD2\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi depletion with defined CHK1 stability readout and epistasis analysis; single lab, two orthogonal methods\",\n      \"pmids\": [\"21389083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"USP1 undergoes autocleavage at a conserved G670/G671 diglycine motif, producing a C-terminal fragment (Gln-Usp1(Ct)) that is targeted for degradation by the Arg/N-end rule pathway through deamidation of its N-terminal Gln by Ntaq1; metabolic stabilization of Gln-Usp1(Ct) decreases PCNA monoubiquitination and causes hypersensitivity to UV irradiation.\",\n      \"method\": \"In vivo autocleavage assay, N-end rule pathway analysis, PCNA ubiquitination assay, UV sensitivity assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical identification of autocleavage product, N-end rule pathway substrate validation, functional UV sensitivity phenotype with defined molecular readout; multiple orthogonal methods\",\n      \"pmids\": [\"23159736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"UAF1 activates USP1 by modulating its active site conformation: UAF1 lowers the pKa of the catalytic histidine in USP1 by ~0.43 pH units (without changing the catalytic cysteine pKa), facilitating general base catalysis at neutral pH. USP1/UAF1 uses a general base catalysis mechanism (not an ion-pair mechanism), with a kinetic isotope effect of ~2.8–3.0 and single proton transfer in the transition state.\",\n      \"method\": \"In vitro kinetic analysis (pH-dependent inactivation, solvent kinetic isotope effect, proton inventory), active site mutagenesis\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — rigorous in vitro enzymology with multiple mechanistic probes; single lab but multiple orthogonal biochemical methods\",\n      \"pmids\": [\"22439892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"USP1 contains two nuclear localization signals (NLSs) that mediate nuclear import of the USP1/UAF1 complex; USP1 and UAF1 form a complex in the cytoplasm that subsequently translocates to the nucleus via USP1 NLSs. The UAF1-binding site was mapped to a conserved ~100 amino acid motif in the Fingers subdomain of USP1 (residues 420–520).\",\n      \"method\": \"Nuclear localization signal mutagenesis, cellular relocation assay, deletion mapping\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with NLS mutants and domain deletion mapping; single lab, two orthogonal methods\",\n      \"pmids\": [\"22701671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CAPNS1 (calpain regulatory subunit) is required for USP1 stability; calpain stabilizes USP1 by activating Cdk5, which in turn inhibits Cdh1 and thereby prevents APC/C(Cdh1)-mediated USP1 degradation. Loss of CAPNS1 increases ubiquitinated PCNA, favors polymerase-η loading on chromatin, and increases mutagenesis.\",\n      \"method\": \"RNAi knockdown (CAPNS1), protein stability assay, rescue with Cdk5/p25 overexpression, PCNA ubiquitination and pol-η chromatin loading assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis between calpain/Cdk5/Cdh1 and USP1 stability with functional readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23589330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The USP1-UAF1 complex is a key regulator of the DNA translesion synthesis (TLS) and Fanconi anemia (FA) deubiquitination pathways; ML323, a potent and selective inhibitor of USP1-UAF1, increases monoubiquitinated PCNA and FANCD2 in cells after UV/cisplatin damage, demonstrating that deubiquitination by this complex is required for the DNA damage response.\",\n      \"method\": \"Selective small-molecule inhibitor (ML323) with selectivity profiling against panel of DUBs, cell-based PCNA/FANCD2 ubiquitination assay\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — highly selective inhibitor with rigorous selectivity profiling, replicated cellular and biochemical readouts across multiple labs\",\n      \"pmids\": [\"24531842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP1 binds to and is stimulated by fork DNA; a truncated USP1 lacking its DNA-binding region is not stimulated by DNA and fails to localize to and protect replication forks. Persistence of monoubiquitinated PCNA at stalled replication forks is the mechanism of cell death in BRCA1-deficient cells lacking USP1.\",\n      \"method\": \"DNA-binding assay, truncation mutant analysis, replication fork protection assay (DNA fiber), live-cell imaging/localization, USP1 knockdown/inhibition in BRCA1-deficient cells\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain deletion mutant with DNA-binding assay, fork protection fiber assay, mechanistic rescue experiments; multiple orthogonal methods\",\n      \"pmids\": [\"30576655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The USP1-UAF1 complex interacts with RAD51AP1 through UAF1; depletion of USP1 or UAF1 destabilizes RAD51AP1. The USP1-UAF1-RAD51AP1 interaction promotes a late step of HR repair (RAD51 foci resolution) independently of FANCD2 deubiquitination.\",\n      \"method\": \"Proteomics (UAF1 interactome), Co-IP, domain mapping, RNAi knockdown, RAD51 foci analysis, chromosomal aberration assay\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based interactome plus Co-IP validation and functional epistasis; single lab, two orthogonal methods\",\n      \"pmids\": [\"27463890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PDGF signaling upregulates USP1 transcription through E2F transcription factors, which directly bind the Usp1 promoter; USP1 then stabilizes ID2, which is required for glioma cell survival in a PDGF-driven mouse model.\",\n      \"method\": \"Comparative transcriptomics, ChIP (E2F binding to Usp1 promoter), genetic ablation of Id2/Usp1, pharmacological USP1 inhibition, mouse glioma model\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-confirmed transcriptional regulation and in vivo mouse model with survival readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"26951930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The USP1-UAF1 complex stabilizes TBK1 by removing its K48-linked polyubiquitination, thereby preventing TBK1 degradation and enhancing TLR3/4 and RIG-I-induced IRF3 activation and IFN-β secretion during antiviral responses.\",\n      \"method\": \"Co-IP, ubiquitination assay (K48-linked), RNAi knockdown, IFN-β reporter assay, ML323 inhibitor in vitro/in vivo\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with ubiquitin linkage specificity and functional IFN-β readout; single lab, two orthogonal methods\",\n      \"pmids\": [\"29138248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP1 deubiquitinates and stabilizes KPNA2; USP1-mediated stabilization of KPNA2 is required for USP1's pro-metastatic function in breast cancer cells in vitro and in vivo.\",\n      \"method\": \"Co-IP, ubiquitination assay, RNAi knockdown, rescue experiments, mouse lung metastasis model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay and in vivo rescue; single lab, two orthogonal methods\",\n      \"pmids\": [\"30531833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"USP1 deubiquitinates CHK1 to maintain its phosphorylated levels; USP1 also stabilizes Survivin/BIRC5 in glioblastoma stem cells and Survivin is shown to be downstream of USP1 in EWS cells; USP1 depletion reduces ID1 and CHK1 protein stability in glioblastoma.\",\n      \"method\": \"RNAi knockdown, protein stability assay, USP1 inhibitor (pimozide), in vivo mouse model\",\n      \"journal\": \"Neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — RNAi/inhibitor with protein level readout across two independent studies, but no direct deubiquitination reconstitution in this paper\",\n      \"pmids\": [\"26032834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Upon platinum treatment, USP1 is phosphorylated by ATM and ATR kinases, binds to Snail, deubiquitinates and stabilizes Snail protein, thereby promoting tumor dissemination and conferring platinum resistance in ovarian cancer. USP1 knockout or inhibition increased platinum sensitivity and decreased metastatic dissemination in a Snail-dependent manner.\",\n      \"method\": \"Co-IP, ubiquitination assay, kinase inhibitor epistasis (ATM/ATR), in vivo mouse model, USP1 knockout/inhibition\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, and in vivo mouse metastasis model with Snail-rescue epistasis; single lab, multiple methods\",\n      \"pmids\": [\"31086816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Efficient FANCD2 deubiquitination by USP1-UAF1 requires DNA and DNA binding by UAF1; the DNA-binding activity of RAD51AP1 can substitute for that of UAF1 in FANCD2 deubiquitination in a reconstituted biochemical system. Both UAF1 and RAD51AP1 DNA-binding activities are important for FANCD2 deubiquitination in cells.\",\n      \"method\": \"Reconstituted biochemical deubiquitination assay with purified components, DNA-binding mutant analysis, cellular assay with UAF1/RAD51AP1 mutants\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — fully reconstituted in vitro biochemical system with purified proteins plus validation in cells; single lab but rigorous reconstitution\",\n      \"pmids\": [\"31253762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP1 removes K63-linked polyubiquitin chains on Akt to restrict PI3K-Akt-FoxO signaling in mouse muscle during prolonged starvation; a USP1 complex containing Dab2, TSC1/TSC2, and PHLPP1 is identified, with Dab2 essential for Akt recruitment to this complex for PI3K-Akt-FoxO inhibition.\",\n      \"method\": \"DUB screening, Co-IP, mass spectrometry, RNAi knockdown in mouse muscle, glucose uptake assay, ubiquitin linkage analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — DUB screen plus Co-IP/MS complex identification and in vivo mouse muscle RNAi with functional readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"32133736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP1 regulates AKT phosphorylation by stabilizing PHLPP1 (a phosphatase that dephosphorylates AKT); USP1 interacts with PHLPP1, and USP1 silencing decreases PHLPP1 half-life and increases AKT1 phosphorylation.\",\n      \"method\": \"Co-IP, GST pull-down, CHX stability assay, RNAi knockdown\",\n      \"journal\": \"Journal of cancer research and clinical oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and GST pulldown with CHX stability assay; single lab, multiple methods but no direct deubiquitination reconstitution\",\n      \"pmids\": [\"22426999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structures of human USP1-UAF1 with and without ubiquitin, and cryo-EM of USP1-UAF1 bound to monoubiquitinated FANCI-FANCD2, reveal plasticity in USP1, an extensive interface between UAF1 and FANCI required for substrate recognition, and USP1-UAF1-driven conformational changes in the FANCI-FANCD2 substrate during deubiquitination. Mutagenesis confirmed the UAF1-FANCI interface.\",\n      \"method\": \"X-ray crystallography, cryo-EM, site-directed mutagenesis, biochemical deubiquitination assay\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution structures plus mutagenesis validation and biochemical assays; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"33795880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Insert L1 in USP1 is a central regulatory hub: it limits intrinsic USP1 activity (together with insert L3), and this inhibition is relieved by UAF1 binding; insert L1 also conveys substrate-dependent (DNA and PCNA) increases in USP1 activity independently of UAF1-mediated activation.\",\n      \"method\": \"Biochemical activity assays with USP1 insert deletion mutants, UAF1 activation assays, DNA/PCNA stimulation assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple deletion mutants separating two regulatory mechanisms; single lab with multiple orthogonal biochemical methods\",\n      \"pmids\": [\"33619839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1 deubiquitinates and stabilizes BCAT2 at the K229 site; BCAA increases USP1 protein at the translational level via the GCN2-eIF2α pathway, forming a feedforward axis that promotes pancreatic cancer development.\",\n      \"method\": \"DUB library screen, Co-IP, ubiquitination assay (site-specific), in vitro deubiquitination, in vivo orthotopic mouse model\",\n      \"journal\": \"National science review\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro deubiquitination assay and site-specific mapping plus in vivo model; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"35663242\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1 interacts with and deubiquitinates EZH2, stabilizing it downstream of a β-catenin/TCF4 transcriptional axis (β-catenin/TCF4 → USP1 transcription → EZH2 stabilization → H3K27me3-mediated gene repression) to drive glioma tumorigenesis.\",\n      \"method\": \"Co-IP, ubiquitination assay, ChIP, reporter assay, RNAi/knockdown, in vivo tumor model\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, ubiquitination assay, and ChIP with in vivo functional readout; single lab, multiple methods\",\n      \"pmids\": [\"30425057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The molecular chaperone GRP75 recruits USP1 to inhibit K48-linked polyubiquitination of SIX1, forming a GRP75-USP1-SIX1 trimeric complex; the C-terminus of GRP75 (433–679 aa peptide-binding domain) is required for complex formation.\",\n      \"method\": \"Co-IP, ubiquitination assay, domain mapping (deletion mutants), in vitro and in vivo tumor models\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping and ubiquitination assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"34079090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP1 inhibition causes accumulation of mono- and polyubiquitinated PCNA and leads to reduced PCNA protein levels; ectopic expression of WT PCNA (but not ubiquitin-dead K164R PCNA) reverses USP1 inhibitor sensitivity. RAD18 and UBE2K (promoting PCNA mono- and polyubiquitination respectively) are mediators of USP1 dependency in BRCA1/2-mutant tumors.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 screen, PCNA ubiquitination assay, rescue with PCNA K164R mutant, cell viability assay\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased CRISPR screen plus mechanistic rescue with PCNA mutant and two independent gene validations (RAD18, UBE2K); multiple orthogonal methods\",\n      \"pmids\": [\"36228090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cells with an autocleavage-defective USP1 mutant (still able to deubiquitinate PCNA) experience more replication fork-stalling and premature fork termination; super-resolution microscopy and live-cell single-molecule tracking show that USP1 autocleavage is required for its proper recycling from sites of active DNA synthesis ('USP1-trapping'); the metalloprotease Spartan facilitates removal of USP1 molecules from DNA to counteract USP1-trapping cytotoxicity.\",\n      \"method\": \"Autocleavage-defective mutant knock-in, super-resolution microscopy, live-cell single-molecule tracking, DNA fiber assay, Spartan epistasis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple advanced microscopy methods, single-molecule tracking, DNA fiber assay, and genetic epistasis in a single study; multiple orthogonal methods\",\n      \"pmids\": [\"35365626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cryo-EM at 2.5 Å resolution of the USP1-UAF1-ML323 inhibitor complex reveals that ML323 binds to a cryptic hydrophobic site in USP1, disrupting part of its hydrophobic core and inducing conformational changes in secondary structure that subtly rearrange the active site to achieve inhibition.\",\n      \"method\": \"Cryo-EM structure determination, with and without inhibitor\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution cryo-EM structure with direct visualization of inhibitor binding mode and structural mechanism; single lab but rigorous structural study\",\n      \"pmids\": [\"36170365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP1 interacts with MAX and maintains MAX protein stability through deubiquitination; this promotes transcription of MYC target genes and contributes to chemotherapy resistance in B-cell lymphoma.\",\n      \"method\": \"Co-IP, ubiquitination assay, RNAi/shRNA knockdown, in vivo mouse lymphoma model\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay and in vivo mouse model; single lab, two orthogonal methods\",\n      \"pmids\": [\"36352191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP1 identifies MAST1 as a substrate; USP1 interacts with MAST1, prevents its K48-linked polyubiquitination, and extends its half-life, thereby stabilizing MAST1 and promoting MAST1-mediated MEK1 activation and cisplatin resistance.\",\n      \"method\": \"CRISPR/Cas9 genome-wide dual screen, Co-IP, in vitro deubiquitination assay, ubiquitination linkage analysis (K48), half-life analysis, xenograft mouse model\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro deubiquitination assay plus Co-IP, ubiquitin linkage analysis, and in vivo mouse model; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"35966591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"N-terminus of USP1 contains a FANCD2-specific binding sequence required for deubiquitination of K561 on FANCD2, whereas the N-terminus is not required for PCNA or FANCI deubiquitination; the N-terminus of USP1 is sufficient to engineer substrate specificity into a more promiscuous USP.\",\n      \"method\": \"Reconstituted in vitro deubiquitination of purified monoubiquitinated FANCD2/FANCI/PCNA, N-terminal deletion and chimera mutants\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — fully reconstituted in vitro deubiquitination with purified substrates and multiple deletion/chimera mutants; direct mechanistic determination of substrate specificity\",\n      \"pmids\": [\"30456385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"USP1 is phosphorylated by CDKs in mitosis, and this phosphorylation may prevent premature APC/C(Cdh1)-mediated degradation during normal cell cycle progression. The S313 phosphorylation site is not critical for PCNA deubiquitination or UAF1 binding in a cellular environment. The UAF1-binding site in USP1 maps to residues 420–520 (Fingers subdomain). Autocleavage of USP1 can occur in cis and is disrupted by the cancer-associated mutation L669P.\",\n      \"method\": \"Structure-function analysis with USP1 mutants (S313A, S313D, GG/AA, cancer-associated mutations), nuclear relocation assay, PCNA deubiquitination assay, Co-IP\",\n      \"journal\": \"Molecular cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mutant constructs with two orthogonal functional assays; single lab\",\n      \"pmids\": [\"25744535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"USP1 protein levels are phosphorylated by CDKs during mitosis, and this phosphorylation event may prevent premature degradation by APC/C(Cdh1) during normal cell cycle progression.\",\n      \"method\": \"Cell cycle synchronization, phosphorylation assay, CDK inhibitor treatment\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — cell-cycle synchronization with CDK inhibitors and phosphorylation analysis; single lab, single main method\",\n      \"pmids\": [\"22101265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP1 autocleavage (at the GG/AA diglycine motif) is specifically required for USP1 function in ICL repair but not UV repair; an autocleavage-defective mutant Usp1(GG/AA) corrects monoubiquitinated Fancd2 levels and UV resistance in Usp1−/− MEFs, but only partially rescues MMC sensitivity and shows defective Fancd2 foci formation and HR.\",\n      \"method\": \"Autocleavage mutant knock-in in Usp1−/− MEFs, MMC/UV sensitivity assay, Fancd2 foci analysis, HR assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — separation-of-function mutant with multiple DNA repair pathway readouts; single lab, multiple assays\",\n      \"pmids\": [\"26783108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TonEBP regulates PCNA polyubiquitination by sequentially recruiting E3 ligase SHPRH and then deubiquitinase USP1 to DNA damage sites; the Rel-homology domain of TonEBP is essential for interaction with both SHPRH and USP1, PCNA polyubiquitination, and cell survival after DNA damage.\",\n      \"method\": \"Co-IP, recruitment assay (chromatin/DNA damage foci), RNAi knockdown, domain deletion mapping\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping and chromatin recruitment assay plus functional readout; single lab, two orthogonal methods\",\n      \"pmids\": [\"31376680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"UAF1 deubiquitinates and stabilizes METTL3 by removing K48-linked polyubiquitination after spinal cord injury, and the USP1/UAF1 complex specifically binds METTL3 to maintain its stability.\",\n      \"method\": \"Co-IP, ubiquitination assay (K48-linked), conditional knockout, in vivo SCI model\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and conditional KO with in vivo model; single lab, multiple methods\",\n      \"pmids\": [\"36653190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1 identifies ULK1 as a substrate, removing K63-linked ubiquitination from ULK1; USP1 depletion or inhibition causes ULK1 compartmentalization into a detergent-insoluble (urea-soluble) fraction enriched in SQSTM1/p62 and HDAC6, forming protein aggregates, and inhibits canonical autophagic flux while promoting an alternative lysosomal-mediated degradation route.\",\n      \"method\": \"Co-IP, ubiquitin linkage analysis (K63), cellular fractionation, immunofluorescence, RNAi knockdown, pimozide inhibition\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with K63 ubiquitin linkage specificity and fractionation/localization with functional autophagy readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"30335599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"USP1 plays a role in regulating centrosome duplication; ectopic expression of catalytically active (but not C90S inactive) Usp1 induces centrosome amplification, abnormal mitotic spindles, chromosome missegregation, and aneuploidy. Loss of ID1 suppresses Usp1-induced centrosome amplification, placing ID1 downstream of USP1 in this process.\",\n      \"method\": \"Usp1 overexpression and C90S catalytic mutant, centrosome counting, mitotic spindle analysis, ID1 knockdown epistasis in Usp1−/− MEFs\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — catalytic mutant discrimination, epistasis with ID1, and cellular phenotype readouts; single lab, multiple methods\",\n      \"pmids\": [\"26822809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP1 interacts with TAZ/WWTR1 and increases TAZ protein stability by preventing its poly-ubiquitination; loss of USP1 reduces TAZ protein levels and decreases cell proliferation and migration of breast cancer cells.\",\n      \"method\": \"siRNA DUB library screen, Co-IP, ubiquitination assay, RNAi knockdown\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA screen with Co-IP validation and ubiquitination assay; single lab, multiple methods but no direct deubiquitination reconstitution\",\n      \"pmids\": [\"33114077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 interacts with the WW domain of TAZ and suppresses K11-linked polyubiquitination of TAZ to enhance TAZ stability and Hippo/TAZ signaling in HCC; USP1 depletion leads to decreased TAZ nuclear accumulation and downstream Hippo target gene expression.\",\n      \"method\": \"DUB siRNA screen, Co-IP, domain mapping (WW domain), ubiquitin linkage-specific assay (K11), RNAi knockdown, in vivo tumor model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and domain mapping plus in vivo model; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"37041150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 interacts with PARP1 and removes the ubiquitin chain at K197 of PARP1 to prevent its proteasomal degradation; GCN5 acetyltransferase acetylates USP1 at K130, enhancing USP1-PARP1 affinity and further increasing PARP1 stabilization.\",\n      \"method\": \"Proteomics/ubiquitylome analysis, Co-IP, GST pull-down, immunofluorescence, deletion mutant mapping, in vitro/in vivo tumor models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics-based substrate identification with Co-IP/pulldown validation, site-specific ubiquitination and acetylation mapping; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"37821462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP1 removes K63-linked polyubiquitin chains from PARP1 and controls PARP1 chromatin trapping and PARylation activity, thereby regulating sensitivity to PARP inhibitors.\",\n      \"method\": \"Co-IP, ubiquitin linkage analysis (K63), chromatin trapping assay, PARylation assay, RNAi/knockout\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with linkage-specific assay and direct functional readouts (trapping, PARylation); single lab, multiple orthogonal methods\",\n      \"pmids\": [\"39536107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP1 inhibition promotes accumulation of ssDNA gaps at replication forks in BRCA1-deficient cells via RAD18-dependent PCNA monoubiquitination; RAD18 knockdown causes USP1 inhibitor resistance and suppresses ssDNA gap accumulation, defining RAD18-dependent PCNA ubiquitination as the proximal mediator of USP1 dependency.\",\n      \"method\": \"ssDNA gap assay, PCNA ubiquitination assay, RAD18 knockdown rescue, patient-derived organoid assay\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic epistasis (RAD18 rescue), functional ssDNA gap biomarker, validated in multiple model systems including patient-derived organoids\",\n      \"pmids\": [\"38885312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP1 inhibitor KSQ-4279 (RO7623066) binds to the same cryptic hydrophobic site as ML323 in USP1 but disrupts the protein structure in subtly different ways; inhibitor binding drives a substantial increase in USP1 thermal stability, mediated through filling a hydrophobic tunnel-like pocket.\",\n      \"method\": \"Cryo-EM structure determination, biochemical assays, thermal stability assay\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure with biochemical validation; single lab but direct structural mechanism\",\n      \"pmids\": [\"39190802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP1 depletion suppresses expansion of PRIMPOL-generated ssDNA gaps by preventing MRE11 and EXO1 nuclease-mediated bidirectional gap expansion; USP1's role in promoting gap accumulation is linked to its deubiquitination of PCNA, as PCNA ubiquitination prevents gap accumulation during replication.\",\n      \"method\": \"USP1 depletion, PCNA ubiquitination assay, MRE11/EXO1 epistasis, ssDNA gap assay, DSB assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi depletion with multiple epistasis experiments and direct gap/DSB readouts; single lab, multiple methods\",\n      \"pmids\": [\"38180818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 interacts with Aurora B and deubiquitinates it, maintaining Aurora B stability and mediating T-ALL glucocorticoid resistance; ALKBH5 enhances USP1 expression by reducing m6A modification on USP1 mRNA.\",\n      \"method\": \"Co-IP, ubiquitination assay, in vivo mouse model, ALKBH5 knockdown/overexpression, m6A assay\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with ubiquitination assay and in vivo model; single lab, multiple methods\",\n      \"pmids\": [\"34169564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 interacts with PLK1, deubiquitinates it, and increases its stability; PLK1 in turn regulates LDHA expression to promote aerobic glycolysis in T-ALL cells.\",\n      \"method\": \"Co-IP, ubiquitination assay, overexpression/knockdown epistasis, metabolic assay (lactate)\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay and epistasis with LDHA rescue; single lab, multiple methods\",\n      \"pmids\": [\"36912760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1 deubiquitinates RPS16 at K48-linked ubiquitin chains to stabilize it; USP1-C90A catalytic mutant fails to reduce K48-linked ubiquitinated RPS16, confirming enzymatic activity requirement. USP1 depletion mimics RPS16 deficiency in inhibiting HCC growth and metastasis.\",\n      \"method\": \"Mass spectrometry, Co-IP, ubiquitination assay, catalytic mutant (C90A), rescue experiments, xenograft mouse model\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based substrate identification, Co-IP, catalytic mutant validation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"34154657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 deubiquitinates and stabilizes C/EBPβ; USP1 catalytic mutant fails to affect C/EBPβ stability or ubiquitination, demonstrating enzymatic activity requirement. USP1 directly interacts with C/EBPβ and its upregulation during adipocyte differentiation promotes lipid accumulation.\",\n      \"method\": \"Co-IP, ubiquitination assay, catalytic mutant (C90A), overexpression/knockdown, USP1 inhibitor (ML323) in vivo mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with catalytic mutant discrimination and in vivo mouse metabolic model; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"38012162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP1 removes SAR1A K27-linked oligo-ubiquitination, thereby blocking SAR1A-mediated STING-COP-II transport complex assembly and STING trafficking from ER to Golgi; USP1 inhibition sustains SAR1A ubiquitination and enhances cGAS-STING pathway activation and Type I IFN production.\",\n      \"method\": \"Chemical screen (DUB inhibitors), Co-IP, ubiquitination linkage analysis (K27), STING trafficking assay, IFN reporter assay, USP1 inhibitor (ML323)\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and direct STING trafficking functional readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"39976106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UAF1-USP1 deubiquitinase complex interacts with cGAS, selectively cleaves K48-linked polyubiquitination of cGAS, and stabilizes cGAS protein expression in macrophages; this provides positive feedback for cGAS-dependent antiviral type I IFN responses.\",\n      \"method\": \"Co-IP, ubiquitin linkage analysis (K48), Uaf1 conditional knockout, ML323 inhibitor, IFN reporter assay in vivo\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with K48-specific ubiquitination assay and conditional KO with in vivo antiviral readout; single lab, multiple methods\",\n      \"pmids\": [\"38054892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1 deubiquitinates and stabilizes TBLR1, and this promotes survival of circulating tumor cells in hepatocellular carcinoma by regulating Wnt signaling.\",\n      \"method\": \"Co-IP, ubiquitination assay, USP1 knockout, in vitro and in vivo CTC survival assay\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP with ubiquitination assay; single lab, single main deubiquitination method\",\n      \"pmids\": [\"33102219\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 interacts with Bcr-Abl oncoprotein in the nucleus of K562 CML cells; inhibition of USP1 activity by ML323 reduces Bcr-Abl protein levels.\",\n      \"method\": \"Co-IP, Western blot, confocal microscopy, USP1 inhibitor treatment\",\n      \"journal\": \"Experimental oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP and confocal colocalization; single lab, single method; mechanistic relationship not fully established\",\n      \"pmids\": [\"32602291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP1-WDR48 (UAF1) complex deubiquitinates TAK1 in vitro, reducing its polyubiquitination and stabilizing it, thereby enhancing TGF-β-mediated EMT and migration in TNBC cells.\",\n      \"method\": \"Co-IP, in vitro ubiquitination/deubiquitination assay, RNAi knockdown\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — in vitro deubiquitination assay plus Co-IP; single lab, single in vitro method without full reconstitution\",\n      \"pmids\": [\"33461373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP1 can be harnessed as a deubiquitinase-targeting chimera (DUBTAC) anchor; USP1-recruiting DUBTACs stabilize CFTR and the tumor suppressor UTX in a USP1-dependent manner, demonstrating that USP1's deubiquitinating activity can be re-directed to non-natural substrates via bifunctional molecules.\",\n      \"method\": \"DUBTAC chemical biology, protein stability assay, knockdown epistasis (USP1 depletion reverses stabilization), cellular assays\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — USP1 dependency confirmed by knockdown rescue with two independent target proteins; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40252079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"USP1 deubiquitinates and stabilizes survivin/BIRC5 in renal cell carcinoma and Ewing sarcoma; USP1 inhibition downregulates survivin by removing ubiquitin, and ML323 also upregulates DR5 by decreasing miR-216a-5p.\",\n      \"method\": \"Co-IP, ubiquitination assay, siRNA knockdown, USP1 inhibitor (ML323/pimozide), in vivo mouse xenograft\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with ubiquitination assay and in vivo xenograft; single lab, multiple methods\",\n      \"pmids\": [\"36153316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"USP1 interacts with ERα and promotes ERα stability by inhibiting ERα K48-linked poly-ubiquitination in breast cancer cells.\",\n      \"method\": \"DUB siRNA library screen, Co-IP, ubiquitination assay (K48-linked), RNAi knockdown\",\n      \"journal\": \"Journal of Cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP with ubiquitination assay from siRNA screen; single lab, single main method\",\n      \"pmids\": [\"33123289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP1 stabilizes NLRP3 and AIM2 inflammasome components through deubiquitination, promoting pyroptosis in thyroid follicular cells; USP1 also facilitates p65 nuclear translocation to modulate NLRP3 transcription.\",\n      \"method\": \"Co-IP, ubiquitination assay, USP1 knockdown/inhibition, caspase-1/GSDMD-N assay, mouse HT model, AIM2 rescue epistasis\",\n      \"journal\": \"Molecular medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP with ubiquitination assay and functional pyroptosis readouts; single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"39134949\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP1 deubiquitinates and stabilizes KIF11 at the K77 site; high interstitial fluid pressure stabilizes KIF11 in HCC through USP1-mediated deubiquitination. USP1 inhibition by ML323 reduces KIF11 protein levels and suppresses tumor progression in mice.\",\n      \"method\": \"Co-IP, proteomic analysis, ubiquitination assay (site-specific K77), in vivo orthotopic mouse model, USP1 inhibitor\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP with proteomics-based identification and site-specific ubiquitination; single lab, in vivo model but limited mechanistic reconstitution\",\n      \"pmids\": [\"39810156\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"USP1 is a nuclear cysteine protease deubiquitinase that functions in complex with its obligatory activator UAF1 (WDR48); UAF1 binding lowers the pKa of the catalytic histidine to facilitate general base catalysis at neutral pH, and the regulatory insert L1 serves as an allosteric hub controlling both UAF1-mediated and substrate (DNA/PCNA)-mediated activation. USP1-UAF1 removes monoubiquitin from FANCD2 (at K561), FANCI, and PCNA (at K164) to regulate Fanconi anemia interstrand crosslink repair, translesion synthesis, and homologous recombination, with FANCD2 deubiquitination additionally requiring DNA binding and conformational changes in the substrate as revealed by cryo-EM; USP1 undergoes autocleavage at a conserved diglycine motif to allow its own recycling from replication forks (counteracted by the metalloprotease Spartan), and is degraded in G1 by APC/C(Cdh1) while CDK-mediated phosphorylation in mitosis prevents premature destruction. Beyond DNA repair, USP1 deubiquitinates and stabilizes a broad set of substrates—including ID1/2/3, Akt, PCNA, TBK1, cGAS, PARP1, EZH2, Snail, TAZ, C/EBPβ, CHK1, ULK1, MAST1, and others—placing it at the intersection of DNA damage responses, stem cell maintenance, immune signaling, autophagy, and metabolic regulation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"USP1 is a nuclear cysteine-protease deubiquitinase that operates as a central regulator of the DNA damage response, removing monoubiquitin from FANCD2 (at K561) and PCNA (at K164) to control Fanconi anemia interstrand-crosslink repair, translesion synthesis, and homologous recombination [#0, #1, #33]. It functions as an obligate heterodimer with the activator UAF1/WDR48, which binds a conserved motif in the USP1 Fingers subdomain and activates catalysis by lowering the pKa of the catalytic histidine to enable general-base catalysis at neutral pH, with the regulatory insert L1 serving as an allosteric hub that integrates both UAF1-mediated and substrate (DNA/PCNA)-driven activation [#9, #10, #24]. Substrate engagement is sculpted further by accessory factors and intrinsic features: a USP1 N-terminal sequence confers FANCD2 specificity, DNA binding by UAF1 (or substitutively by RAD51AP1) is required for efficient FANCD2 deubiquitination, and ELG1 directs the complex specifically toward PCNA [#3, #20, #33]. Cryo-EM of USP1-UAF1 bound to monoubiquitinated FANCI-FANCD2 shows that catalysis is accompanied by UAF1-FANCI interface contacts and conformational changes in the substrate [#23]. USP1 abundance and chromatin residence are tightly gated: it is degraded in G1 by APC/C(Cdh1) to permit PCNA monoubiquitination, protected in mitosis by CDK phosphorylation, and recycled from active replication forks via autocleavage at a diglycine motif, with the metalloprotease Spartan counteracting USP1 trapping [#6, #8, #29, #34]. Because persistent PCNA monoubiquitination and RAD18-dependent ssDNA gap accumulation are lethal in BRCA1/2-deficient cells, USP1 is a synthetic-lethal target, and selective inhibitors (ML323, KSQ-4279) act through a cryptic hydrophobic pocket that rearranges the active site [#13, #28, #30, #45, #46]. Beyond DNA repair, USP1-UAF1 deubiquitinates and stabilizes ID1/2/3 to maintain stem-like states and centrosome control, and stabilizes substrates spanning innate immune signaling (TBK1, cGAS), autophagy (ULK1), and transcriptional/metabolic regulators, placing it at the intersection of genome maintenance, stemness, and signaling [#5, #16, #39, #40, #53].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that USP1 is a bona fide ubiquitin-specific protease, defining its core biochemical identity before any cellular role was known.\",\n      \"evidence\": \"recombinant USP1 cleaving Ub-beta-galactosidase in vitro\",\n      \"pmids\": [\"9806842\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No physiological substrate identified\", \"No regulatory partner or cellular pathway known at this stage\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified the first physiological substrate and pathway by showing USP1 deubiquitinates monoubiquitinated FANCD2, linking the enzyme to Fanconi anemia crosslink repair.\",\n      \"evidence\": \"RNAi screen, Co-IP, chromatin fractionation in human cells\",\n      \"pmids\": [\"15694335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the activator requirement for catalysis\", \"Mechanism of substrate recognition unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Confirmed in an organism that USP1 acts downstream in the FA pathway and is required for HR, moving beyond cell-line correlation to genetic epistasis.\",\n      \"evidence\": \"Usp1 mouse knockout, MEF analysis, Usp1/Fancd2 double KO epistasis\",\n      \"pmids\": [\"19217432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of HR defect not separated from FANCD2 deubiquitination\", \"Perinatal lethality mechanism not dissected\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved how USP1 activity is restricted to the correct cell-cycle window and how substrate targeting is diversified, and broadened its substrate range to ID proteins and CHK1.\",\n      \"evidence\": \"APC/C(Cdh1)-mediated G1 degradation assays, ELG1-directed PCNA deubiquitination, ID1/2/3 and CHK1 stability assays, DT40 HR knockouts\",\n      \"pmids\": [\"21768287\", \"20147293\", \"21925315\", \"21389083\", \"21482670\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of UAF1/ELG1 specificity not yet defined\", \"ID-protein stabilization mechanism in stemness not generalized across tissues\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the enzymatic and regulatory mechanism of the complex—UAF1 activation chemistry, nuclear import, and autocleavage-coupled turnover—explaining how catalysis and protein recycling are controlled.\",\n      \"evidence\": \"in vitro kinetics/proton inventory, NLS mutagenesis and relocation, autocleavage and N-end-rule degradation assays\",\n      \"pmids\": [\"22439892\", \"22701671\", \"23159736\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Allosteric route from UAF1 to active site not visualized structurally\", \"Physiological trigger of autocleavage at forks unclear at this stage\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided pharmacological proof that USP1-UAF1 deubiquitination is required for the PCNA/FANCD2 DNA damage response, establishing the complex as a druggable node.\",\n      \"evidence\": \"selective inhibitor ML323 with DUB selectivity profiling and cellular ubiquitination readouts\",\n      \"pmids\": [\"24531842\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Inhibitor binding mode unknown\", \"Therapeutic context for inhibition not yet defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected USP1 catalytic activity to replication-fork protection and genome stability, showing DNA binding and autocleavage are functionally required and that fork-associated PCNA-Ub persistence kills BRCA1-deficient cells.\",\n      \"evidence\": \"DNA-binding and truncation mutants, DNA fiber fork-protection assays, autocleavage separation-of-function mutants, RAD51AP1 interactome, centrosome assays\",\n      \"pmids\": [\"30576655\", \"26783108\", \"27463890\", \"26822809\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinction between catalytic and scaffolding contributions to HR incompletely resolved\", \"Mechanism coupling DNA binding to activity not yet structural\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Reconstituted FANCD2 deubiquitination from purified components to establish that DNA binding by UAF1 (or RAD51AP1) is mechanistically required for efficient substrate processing.\",\n      \"evidence\": \"fully reconstituted in vitro deubiquitination with DNA-binding mutants plus cellular validation\",\n      \"pmids\": [\"31253762\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate conformational requirements not yet visualized\", \"How DNA binding is coupled to catalysis at atomic level unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Delivered the structural and allosteric framework—crystal/cryo-EM structures and the insert L1 regulatory hub—explaining how UAF1, substrate, and DNA converge to control USP1 activity.\",\n      \"evidence\": \"X-ray and cryo-EM of USP1-UAF1 and the FANCI-FANCD2 complex, insert-deletion biochemical activity assays\",\n      \"pmids\": [\"33795880\", \"33619839\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of insert L1 allostery in cells not directly observed\", \"Structural basis of PCNA versus FANCD2 selectivity not co-resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the proximal mediators of USP1 synthetic lethality and visualized inhibitor mechanism, mechanistically grounding USP1 inhibitors as cancer therapeutics.\",\n      \"evidence\": \"genome-wide CRISPR screen with PCNA K164R rescue (RAD18/UBE2K), live-cell single-molecule tracking of autocleavage-dependent recycling with Spartan epistasis, cryo-EM of ML323 cryptic-site binding\",\n      \"pmids\": [\"36228090\", \"35365626\", \"36170365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants of which BRCA-deficient tumors respond not fully defined\", \"Resistance mechanisms incompletely mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked USP1 dependency to a measurable ssDNA-gap phenotype and refined the medicinal-chemistry basis of clinical-stage inhibitors.\",\n      \"evidence\": \"ssDNA gap assays with RAD18 and MRE11/EXO1 epistasis, patient-derived organoids, cryo-EM of KSQ-4279 binding with thermal-stability profiling\",\n      \"pmids\": [\"38885312\", \"38180818\", \"39190802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biomarker translation to patient selection not established in the corpus\", \"Combination strategies not mechanistically resolved here\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how USP1 substrate selectivity and ubiquitin-linkage specificity are determined across its large non-DNA-repair substrate set, and which of these many reported substrates reflect direct, physiologically dominant deubiquitination events.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Most non-canonical substrate studies are single-lab Co-IP/ubiquitination assays without reconstitution\", \"Linkage specificity (K48/K63/K11/K27) varies by substrate and lacks a unifying structural rationale\", \"Tissue- and context-dependence of substrate choice unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 5, 9, 23, 33]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [2, 9, 24]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [13, 20, 24]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 10]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 1, 13]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 12, 28, 45]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [6, 13, 29, 47]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6, 34, 40]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [8, 9, 23]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [16, 53, 52]}\n    ],\n    \"complexes\": [\"USP1-UAF1 (WDR48) deubiquitinase complex\"],\n    \"partners\": [\"UAF1\", \"FANCD2\", \"FANCI\", \"PCNA\", \"ELG1\", \"RAD51AP1\", \"ID1\", \"TBK1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}