{"gene":"UCK2","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2020,"finding":"UCK2 promotes HCC metastasis through a non-metabolic (catalysis-independent) mechanism: in response to EGF, UCK2 physically interacts with EGFR to block EGF-induced EGFR ubiquitination and degradation, resulting in elevated EGFR-AKT pathway activation. Site-directed mutagenesis confirmed this function is independent of UCK2 catalytic activity.","method":"Site-directed mutagenesis, Co-immunoprecipitation, functional metastasis assays, pharmacological inhibition","journal":"Oncogenesis","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with mutagenesis distinguishing catalytic vs non-catalytic roles, single lab with multiple orthogonal methods","pmids":["33277463"],"is_preprint":false},{"year":2025,"finding":"mTORC1 controls UCK2 protein stability (half-life) in the pyrimidine salvage pathway: when mTORC1 is inhibited, UCK2 is degraded via the CTLH-WDR26 E3 ubiquitin ligase complex; active mTORC1 prevents this degradation. Additionally, UCK1 (an isoform) influences UCK2 turnover by affecting its cellular localization.","method":"Protein stability/turnover assays, genetic knockdown/knockout of CTLH-WDR26 components, subcellular fractionation, pyrimidine salvage flux assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KO/KD with defined biochemical phenotype, multiple pathway components tested, single lab with orthogonal methods","pmids":["39808525"],"is_preprint":false},{"year":2025,"finding":"Under glucose limitation, AMPK phosphorylates GART at Ser440, which facilitates GART binding to UCK2. GART binding (and its production of tetrahydrofolate, THF) inhibits ILKAP phosphatase activity, thereby maintaining AKT1-mediated UCK2-Ser254 phosphorylation. Loss of UCK2-Ser254 phosphorylation promotes TRIM21-mediated UCK2 polyubiquitination and proteasomal degradation.","method":"Phosphosite mutagenesis, Co-immunoprecipitation, ubiquitination assays, AMPK kinase assays, in vivo tumor models","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — site-specific mutagenesis (Ser254, Ser440), reconstituted pathway with multiple enzymatic steps validated, single lab with multiple orthogonal methods","pmids":["39865175"],"is_preprint":false},{"year":2025,"finding":"GLI2 transcriptionally activates HRD1 (an E3 ubiquitin ligase), which in turn mediates ubiquitination and degradation of UCK2, reducing UCK2 protein levels and conferring 5-FU resistance in gastric cancer cells. UCK2 was identified as a critical gene for 5-FU sensitivity via genome-wide CRISPR knockout screen.","method":"CRISPR knockout screen (GeCKO v2), overexpression/knockdown functional assays, ubiquitination assays, luciferase reporter for GLI2-HRD1 transcriptional activation, in vivo xenograft","journal":"Translational oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus functional rescue, ubiquitination assays, single lab with multiple methods","pmids":["40414119"],"is_preprint":false},{"year":2022,"finding":"UCK2 is a homotetrameric enzyme with an allosteric site at the intersubunit interface. Two classes of inhibitors were identified that noncompetitively inhibit UCK2 by reducing kcat without altering KM, confirming the allosteric (not active-site competitive) mechanism.","method":"Structure-based drug design, enzyme kinetics (kcat, KM measurements), in vitro enzymatic inhibition assays","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with kinetic characterization and structural basis identified, single lab with rigorous biochemical methods","pmids":["36190114"],"is_preprint":false},{"year":2025,"finding":"UCK2 forms a physical complex with UCKL1 (Uridine-Cytidine Kinase Like-1) that functions as a molecular scaffold independent of metabolic activity. This UCK2/UCKL1 complex recruits E3 ubiquitin ligase TRIM21, orchestrating ubiquitination and degradation of Smurf2, thereby sustaining Smad3 phosphorylation and amplifying fibrogenic TGF-β signaling in cardiac fibroblasts.","method":"Co-immunoprecipitation, genetic silencing (siRNA/shRNA), AAV-mediated knockdown in murine MI model, western blotting for pathway components, murine cardiac fibrosis model","journal":"Molecular biomedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP and in vivo model, single lab, novel non-metabolic scaffold function not yet independently replicated","pmids":["41457201"],"is_preprint":false},{"year":2025,"finding":"UCK2 (and UCK1) phosphorylate N4-hydroxycytidine (NHC), the active compound of the antiviral molnupiravir. UCK2 displays 9-fold higher catalytic efficiency than UCK1 for NHC. siRNA-mediated knockdown of UCK2 in SARS-CoV-2-infected cells reduced intracellular triphosphate NHC metabolite accumulation and decreased antiviral efficacy 10-fold, establishing UCK2 as the rate-limiting kinase for molnupiravir bioactivation.","method":"Target engagement assays, enzyme kinetic assays with recombinant UCK1/UCK2, siRNA knockdown in SARS-CoV-2-infected cells, intracellular metabolite quantification","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic reconstitution with kinetics plus cellular siRNA validation, preprint not yet peer-reviewed, single lab","pmids":["bio_10.1101_2025.05.13.653844"],"is_preprint":true},{"year":2025,"finding":"UCK2-mediated phosphorylation of cytidine is required for CTP uptake by Chlamydia trachomatis: host UCK2 must convert cytidine to its phosphorylated form prior to incorporation into bacterial nucleic acids, indicating nucleosides are phosphorylated in the host cytoplasm before translocation into the bacterial inclusion.","method":"Click chemistry coupled with fluorescence microscopy tracking cytidine incorporation, UCK2-dependent phosphorylation assay in infected cells","journal":"microPublication biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct experimental demonstration with orthogonal labeling method, single study, single lab","pmids":["40415900"],"is_preprint":false},{"year":2025,"finding":"Overexpression of UCK2 in donor cells enhanced 5-ethynyl uridine (5-EU) incorporation into nascent RNA, demonstrating that UCK2 kinase activity directly controls the intracellular availability of this uridine analog for RNA incorporation. This establishes UCK2 as the rate-limiting kinase for uridine analog phosphorylation in living cells.","method":"UCK2 overexpression, metabolic labeling with 5-EU, click chemistry fluorescence detection, quantification in isolated extracellular vesicles","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single overexpression experiment used as tool for EV labeling, mechanistic detail on UCK2 itself is incidental, preprint, single lab","pmids":["bio_10.1101_2025.08.28.672797"],"is_preprint":true},{"year":2025,"finding":"Cytotoxicity of epigenetic ribopyrimidines in human cells is mediated primarily by UCK2 kinase activity, as demonstrated by identification of UCK2 as the metabolic regulator governing incorporation of these modified nucleosides into cellular RNA.","method":"Cell growth assays with UCK2 modulation, quantification of misincorporation into cellular RNAs, metabolic regulator screening","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, limited mechanistic detail on UCK2 mechanism in abstract","pmids":["bio_10.1101_2025.06.11.659152"],"is_preprint":true},{"year":1976,"finding":"UMPK (UCK2) enzyme activity declines during red cell aging; the lower activity of the UMPK2 allelic variant compared to UMPK1 is explained by more rapid catabolism of the UMPK2 gene product, not by a difference in intrinsic specific activity.","method":"Red cell fractionation by age, enzyme activity measurement across red cell age cohorts","journal":"American journal of human genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — enzyme activity measurements in aged red cell fractions, single study, no molecular mechanism defined","pmids":["178178"],"is_preprint":false},{"year":2026,"finding":"UCK2 physically interacts with the small GTPase RHEB and regulates mTOR signaling in lung adenocarcinoma cells, promoting cell proliferation and migration.","method":"Co-immunoprecipitation, overexpression functional assays, pathway analysis","journal":"Oncology research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP experiment, single lab, limited mechanistic follow-up described in abstract","pmids":["42232606"],"is_preprint":false},{"year":2024,"finding":"UCK2 promotes intrahepatic cholangiocarcinoma progression and cisplatin resistance by activating the PI3K/AKT/mTOR signaling pathway, which inhibits autophagy.","method":"UCK2 knockdown/overexpression, western blotting for PI3K/AKT/mTOR/autophagy markers, in vivo and in vitro cisplatin sensitivity assays","journal":"Cell death discovery","confidence":"Low","confidence_rationale":"Tier 3 / Weak — KD/OE with pathway marker readout, no direct mechanistic link between UCK2 and PI3K established, single lab","pmids":["39179560"],"is_preprint":false}],"current_model":"UCK2 is the rate-limiting enzyme of the pyrimidine salvage pathway that phosphorylates uridine and cytidine to UMP and CMP; its protein stability is regulated by mTORC1 (via CTLH-WDR26 E3-mediated degradation when mTORC1 is inactive) and by a GART-ILKAP-AKT1 axis that protects UCK2-Ser254 phosphorylation from TRIM21-mediated ubiquitination under nutrient stress; additionally, UCK2 exerts non-metabolic, catalysis-independent functions including scaffolding EGFR to block its ubiquitination and activate the EGFR-AKT metastatic pathway, and forming a UCK2/UCKL1 complex that recruits TRIM21 to degrade Smurf2 and amplify TGF-β/Smad3 fibrogenic signaling; UCK2 also contains an allosteric site at its homotetrameric intersubunit interface that can be targeted to reduce kcat without affecting KM."},"narrative":{"mechanistic_narrative":"UCK2 is the rate-limiting kinase of the pyrimidine salvage pathway, phosphorylating uridine and cytidine and thereby controlling the intracellular availability of natural and analog pyrimidine nucleosides for nucleic acid incorporation [PMID:40415900, PMID:bio_10.1101_2025.08.28.672797]. Its catalytic role determines the activation of therapeutically and pathologically relevant nucleoside analogs: UCK2 is the rate-limiting kinase that bioactivates the molnupiravir metabolite N4-hydroxycytidine, with knockdown reducing intracellular triphosphate accumulation and antiviral efficacy [PMID:bio_10.1101_2025.05.13.653844], and it governs the cytotoxic misincorporation of modified ribopyrimidines into cellular RNA [PMID:bio_10.1101_2025.06.11.659152]. UCK2 functions as a homotetramer with an allosteric site at the intersubunit interface that can be inhibited noncompetitively, reducing kcat without altering KM [PMID:36190114]. Beyond catalysis, UCK2 exerts catalysis-independent scaffolding functions: in hepatocellular carcinoma it binds EGFR to block its EGF-induced ubiquitination and degradation, sustaining EGFR-AKT signaling and metastasis [PMID:33277463], and it partners with UCKL1 to recruit the E3 ligase TRIM21 and degrade Smurf2, amplifying TGF-β/Smad3 fibrogenic signaling in cardiac fibroblasts [PMID:41457201]. UCK2 protein abundance is tightly controlled by competing degradation pathways: mTORC1 stabilizes UCK2 while its inactivation triggers CTLH-WDR26 E3-mediated turnover [PMID:39808525], and a glucose-stress AMPK-GART-ILKAP-AKT1 axis maintains UCK2-Ser254 phosphorylation to protect it from TRIM21-mediated ubiquitination [PMID:39865175].","teleology":[{"year":1976,"claim":"Established that UCK2 (UMPK) enzyme activity is set by protein turnover rather than intrinsic catalytic differences, providing the first link between UCK2 abundance and post-synthetic stability.","evidence":"Enzyme activity measurement across age-fractionated red cells comparing UMPK allelic variants","pmids":["178178"],"confidence":"Low","gaps":["No molecular degradation mechanism defined","Allelic variant identity at protein level not resolved"]},{"year":2020,"claim":"Revealed that UCK2 has a non-metabolic function, scaffolding EGFR to prevent its ubiquitination and driving metastasis independent of kinase activity, reframing UCK2 as more than a salvage enzyme.","evidence":"Catalytic-dead mutagenesis, reciprocal Co-IP, and metastasis assays in hepatocellular carcinoma","pmids":["33277463"],"confidence":"High","gaps":["EGFR-binding interface on UCK2 not mapped","Whether tetramerization affects scaffolding unknown"]},{"year":2022,"claim":"Defined UCK2 as a homotetramer with an allosteric intersubunit site that can be targeted noncompetitively, establishing a druggable regulatory mechanism distinct from active-site competition.","evidence":"Structure-based drug design with kcat/KM kinetic characterization of inhibitor classes in vitro","pmids":["36190114"],"confidence":"High","gaps":["Physiological allosteric ligand unidentified","Link between allostery and scaffold function untested"]},{"year":2025,"claim":"Showed UCK2 protein stability is governed by competing nutrient-sensing degradation circuits, integrating UCK2 abundance into mTORC1 and AMPK signaling states.","evidence":"CTLH-WDR26 KO/KD and turnover assays (mTORC1 axis) plus phosphosite mutagenesis of Ser254/Ser440 with ubiquitination assays (AMPK-GART-ILKAP-AKT1-TRIM21 axis) in tumor models","pmids":["39808525","39865175"],"confidence":"High","gaps":["Interplay between the two degradation routes unresolved","Direct E3-substrate contacts not structurally defined"]},{"year":2025,"claim":"Identified a second catalysis-independent scaffold role in which a UCK2/UCKL1 complex recruits TRIM21 to degrade Smurf2, linking UCK2 to TGF-β/Smad3 fibrogenic signaling.","evidence":"Co-IP, genetic silencing, and AAV knockdown in a murine cardiac fibrosis (MI) model","pmids":["41457201"],"confidence":"Medium","gaps":["Not independently replicated","How UCK2 toggles between EGFR and UCKL1/TRIM21 scaffolds unknown"]},{"year":2025,"claim":"Demonstrated UCK2 is the rate-limiting kinase for therapeutic and analog pyrimidine nucleosides, controlling molnupiravir bioactivation, uridine-analog RNA labeling, ribopyrimidine cytotoxicity, and host-supplied nucleoside flux to Chlamydia.","evidence":"Recombinant enzyme kinetics, siRNA knockdown in SARS-CoV-2 infection, click-chemistry metabolic labeling, and infected-cell incorporation assays (some preprint)","pmids":["bio_10.1101_2025.05.13.653844","40415900","bio_10.1101_2025.08.28.672797","bio_10.1101_2025.06.11.659152"],"confidence":"Medium","gaps":["Substrate selectivity determinants across analogs not mapped","Some findings remain preprint-stage"]},{"year":2026,"claim":"Connected UCK2 to upstream mTOR signaling via physical interaction with RHEB, hinting at a feedback link between UCK2 and the mTORC1 axis that stabilizes it.","evidence":"Co-IP and overexpression assays in lung adenocarcinoma cells","pmids":["42232606"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation","Functional consequence of RHEB binding on mTOR not mechanistically established"]},{"year":null,"claim":"How UCK2 partitions between its catalytic salvage role and its multiple catalysis-independent scaffold functions, and what governs partner selection (EGFR vs UCKL1/TRIM21 vs RHEB), remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural basis for distinct scaffold complexes","No unified model coupling abundance control to function switching"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[4,6,7,8]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[6,7,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2]}],"complexes":["UCK2/UCKL1 complex","UCK2 homotetramer"],"partners":["EGFR","UCKL1","TRIM21","GART","RHEB","WDR26"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BZX2","full_name":"Uridine-cytidine kinase 2","aliases":["Cytidine monophosphokinase 2","Testis-specific protein TSA903","Uridine monophosphokinase 2"],"length_aa":261,"mass_kda":29.3,"function":"Phosphorylates uridine and cytidine to uridine monophosphate and cytidine monophosphate (PubMed:11306702, PubMed:11494055). Does not phosphorylate deoxyribonucleosides or purine ribonucleosides (PubMed:11306702). Can use ATP or GTP as a phosphate donor (PubMed:11306702). Can also phosphorylate cytidine and uridine nucleoside analogs such as 6-azauridine, 5-fluorouridine, 4-thiouridine, 5-bromouridine, N(4)-acetylcytidine, N(4)-benzoylcytidine, 5-fluorocytidine, 2-thiocytidine, 5-methylcytidine, and N(4)-anisoylcytidine (PubMed:11306702)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9BZX2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/UCK2","classification":"Not Classified","n_dependent_lines":23,"n_total_lines":1208,"dependency_fraction":0.01903973509933775},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/UCK2","total_profiled":1310},"omim":[{"mim_id":"610866","title":"URIDINE/CYTIDINE KINASE-LIKE 1; UCKL1","url":"https://www.omim.org/entry/610866"},{"mim_id":"609329","title":"URIDINE/CYTIDINE KINASE 2; UCK2","url":"https://www.omim.org/entry/609329"},{"mim_id":"609328","title":"URIDINE/CYTIDINE KINASE 1; UCK1","url":"https://www.omim.org/entry/609328"},{"mim_id":"607505","title":"PAS DOMAIN-CONTAINING SERINE/THREONINE KINASE; PASK","url":"https://www.omim.org/entry/607505"},{"mim_id":"191710","title":"CYTIDINE MONOPHOSPHATE (UMP-CMP) KINASE 1, CYTOSOLIC; CMPK1","url":"https://www.omim.org/entry/191710"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/UCK2"},"hgnc":{"alias_symbol":[],"prev_symbol":["UMPK"]},"alphafold":{"accession":"Q9BZX2","domains":[{"cath_id":"3.40.50.300","chopping":"20-229","consensus_level":"high","plddt":97.0487,"start":20,"end":229}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZX2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZX2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZX2-F1-predicted_aligned_error_v6.png","plddt_mean":86.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UCK2","jax_strain_url":"https://www.jax.org/strain/search?query=UCK2"},"sequence":{"accession":"Q9BZX2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BZX2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BZX2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZX2"}},"corpus_meta":[{"pmid":"23462292","id":"PMC_23462292","title":"Testicular germ cell tumor susceptibility associated with the UCK2 locus on chromosome 1q23.","date":"2013","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23462292","citation_count":57,"is_preprint":false},{"pmid":"31844675","id":"PMC_31844675","title":"CircRNA-UCK2 Increased TET1 Inhibits Proliferation and Invasion of Prostate Cancer Cells Via Sponge MiRNA-767-5p.","date":"2019","source":"Open medicine (Warsaw, Poland)","url":"https://pubmed.ncbi.nlm.nih.gov/31844675","citation_count":54,"is_preprint":false},{"pmid":"34430596","id":"PMC_34430596","title":"METTL3-induced UCK2 m6A hypermethylation promotes melanoma cancer cell metastasis via the WNT/β-catenin pathway.","date":"2021","source":"Annals of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/34430596","citation_count":36,"is_preprint":false},{"pmid":"32670881","id":"PMC_32670881","title":"Hypoxia-Induced lncRNA-NEAT1 Sustains the Growth of Hepatocellular Carcinoma via Regulation of miR-199a-3p/UCK2.","date":"2020","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/32670881","citation_count":35,"is_preprint":false},{"pmid":"1660788","id":"PMC_1660788","title":"Relationships between UMPK and PGD activities and deletions of chromosome 1p in colorectal cancers.","date":"1991","source":"Cancer genetics and cytogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/1660788","citation_count":28,"is_preprint":false},{"pmid":"33277463","id":"PMC_33277463","title":"Non-metabolic role of UCK2 links EGFR-AKT pathway activation to metastasis enhancement in hepatocellular carcinoma.","date":"2020","source":"Oncogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/33277463","citation_count":28,"is_preprint":false},{"pmid":"28103302","id":"PMC_28103302","title":"Crude Extracts, Flavokawain B and Alpinetin Compounds from the Rhizome of Alpinia mutica Induce Cell Death via UCK2 Enzyme Inhibition and in Turn Reduce 18S rRNA Biosynthesis in HT-29 Cells.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28103302","citation_count":28,"is_preprint":false},{"pmid":"35669416","id":"PMC_35669416","title":"The Metabolic and Non-Metabolic Roles of UCK2 in Tumor Progression.","date":"2022","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/35669416","citation_count":25,"is_preprint":false},{"pmid":"2842250","id":"PMC_2842250","title":"Confirmation of the assignment of MYCL to chromosome 1 in humans and its position relative to RH, UMPK, and PGM1.","date":"1988","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/2842250","citation_count":16,"is_preprint":false},{"pmid":"39808525","id":"PMC_39808525","title":"mTORC1 regulates the pyrimidine salvage pathway by controlling UCK2 turnover via the CTLH-WDR26 E3 ligase.","date":"2025","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/39808525","citation_count":13,"is_preprint":false},{"pmid":"416891","id":"PMC_416891","title":"Relative positions of chromosome 1 loci Fy, PGM1, Sc, UMPK, Rh, PGD and ENO1 in man.","date":"1977","source":"Canadian journal of genetics and cytology. Journal canadien de genetique et de cytologie","url":"https://pubmed.ncbi.nlm.nih.gov/416891","citation_count":11,"is_preprint":false},{"pmid":"178178","id":"PMC_178178","title":"Red cell uridine monophosphate kinase: effects of red cell aging on the activity of two UMPK gene products.","date":"1976","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/178178","citation_count":10,"is_preprint":false},{"pmid":"39179560","id":"PMC_39179560","title":"UCK2 promotes intrahepatic cholangiocarcinoma progression and desensitizes cisplatin treatment by PI3K/AKT/mTOR/autophagic axis.","date":"2024","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/39179560","citation_count":9,"is_preprint":false},{"pmid":"35137600","id":"PMC_35137600","title":"UCK2 regulated by miR-139-3p regulates the progression of hepatocellular carcinoma cells.","date":"2022","source":"Future oncology (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/35137600","citation_count":7,"is_preprint":false},{"pmid":"35033815","id":"PMC_35033815","title":"RETRACTED: LncRNA SNHG6 facilitates cell proliferation, migration, invasion and EMT by upregulating UCK2 and activating the Wnt/β-catenin signaling in cervical cancer.","date":"2021","source":"Bioorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35033815","citation_count":7,"is_preprint":false},{"pmid":"168150","id":"PMC_168150","title":"Red-cell uridine-5-monophosphate kinase (UMPK): formal genetics, linkage analysis and population genetics from southwestern Germany.","date":"1975","source":"Humangenetik","url":"https://pubmed.ncbi.nlm.nih.gov/168150","citation_count":7,"is_preprint":false},{"pmid":"39865175","id":"PMC_39865175","title":"The protection of UCK2 protein stability by GART maintains pyrimidine salvage synthesis for HCC growth under glucose limitation.","date":"2025","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/39865175","citation_count":5,"is_preprint":false},{"pmid":"28267789","id":"PMC_28267789","title":"Correction: Crude Extracts, Flavokawain B and Alpinetin Compounds from the Rhizome of Alpinia mutica Induce Cell Death via UCK2 Enzyme Inhibition and in Turn Reduce 18S rRNA Biosynthesis in HT-29 Cells.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28267789","citation_count":5,"is_preprint":false},{"pmid":"37534791","id":"PMC_37534791","title":"Cytotoxic Flavokawain B Inhibits the Growth and Metastasis of Hepatocellular Carcinoma through UCK2 Modulation of the STAT3/Hif-1α/VEGF Signalling Pathway.","date":"2023","source":"Current drug targets","url":"https://pubmed.ncbi.nlm.nih.gov/37534791","citation_count":4,"is_preprint":false},{"pmid":"40414119","id":"PMC_40414119","title":"GLI2-HRD1 axis facilitates 5-FU resistance in gastric cancer cells by regulating ubiquitination degradation of UCK2.","date":"2025","source":"Translational oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40414119","citation_count":3,"is_preprint":false},{"pmid":"2821877","id":"PMC_2821877","title":"[Gene frequencies of the enzymes ALADH, GOT2, GPT, PGM3, SAHH and UMPK in a Swiss population].","date":"1987","source":"Anthropologischer Anzeiger; Bericht uber die biologisch-anthropologische Literatur","url":"https://pubmed.ncbi.nlm.nih.gov/2821877","citation_count":3,"is_preprint":false},{"pmid":"6084457","id":"PMC_6084457","title":"Genetic markers in a Malaysian population: variants of uridine monophosphate kinase (UMPK), phosphoglycolate phosphatase (PGP) and pancreatic amylase (AMY2).","date":"1984","source":"Annals of human biology","url":"https://pubmed.ncbi.nlm.nih.gov/6084457","citation_count":2,"is_preprint":false},{"pmid":"38245591","id":"PMC_38245591","title":"CircUCK2 promotes hepatocellular carcinoma development by upregulating UCK2 in a mir-149-5p-dependent manner.","date":"2024","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/38245591","citation_count":1,"is_preprint":false},{"pmid":"36190114","id":"PMC_36190114","title":"Structure-Based Prototyping of Allosteric Inhibitors of Human Uridine/Cytidine Kinase 2 (UCK2).","date":"2022","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36190114","citation_count":1,"is_preprint":false},{"pmid":"41457201","id":"PMC_41457201","title":"Uridine-Cytidine Kinase 2 (UCK2)/Uridine-Cytidine Kinase Like 1 (UCKL1) complex exacerbates the differentiation of myocardial fibroblasts via TRIM21/Smurf2/Smad3 pathway after myocardial infarction.","date":"2025","source":"Molecular biomedicine","url":"https://pubmed.ncbi.nlm.nih.gov/41457201","citation_count":0,"is_preprint":false},{"pmid":"42232606","id":"PMC_42232606","title":"UCK2 Drives Lung Adenocarcinoma Progression and Immune Dysregulation via the RHEB/mTOR Signaling Axis.","date":"2026","source":"Oncology research","url":"https://pubmed.ncbi.nlm.nih.gov/42232606","citation_count":0,"is_preprint":false},{"pmid":"40415900","id":"PMC_40415900","title":"UCK2-dependent conversion of cytidine to CTP is required for CTP uptake by Chlamydia trachomatis.","date":"2025","source":"microPublication biology","url":"https://pubmed.ncbi.nlm.nih.gov/40415900","citation_count":0,"is_preprint":false},{"pmid":"41928337","id":"PMC_41928337","title":"Extracellular matrix-growth factor signalling drives the oncogenic mir-125b-2/UCK2 axis in hepatocellular carcinoma.","date":"2026","source":"Hereditas","url":"https://pubmed.ncbi.nlm.nih.gov/41928337","citation_count":0,"is_preprint":false},{"pmid":"42255676","id":"PMC_42255676","title":"Network Pharmacology and Integrated Experimental Evidence Demonstrate That Ophiopogonin D Suppresses Hepatocellular Carcinoma Progression via the UCK2-SLC7A11 Axis.","date":"2026","source":"Food science & nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/42255676","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.28.672797","title":"Visualizing extracellular vesicle-mediated RNA transfer using a novel metabolic labeling approach","date":"2025-09-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.28.672797","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.05.13.653844","title":"Uridine cytidine kinases dictate the therapeutic response of molnupiravir via its bioactivation","date":"2025-05-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.13.653844","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.11.659152","title":"Metabolism of epigenetic ribonucleosides leads to nucleolar stress and cytotoxicity","date":"2025-06-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.11.659152","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16123,"output_tokens":3349,"usd":0.049302,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10877,"output_tokens":2924,"usd":0.063742,"stage2_stop_reason":"end_turn"},"total_usd":0.113044,"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\": 2020,\n      \"finding\": \"UCK2 promotes HCC metastasis through a non-metabolic (catalysis-independent) mechanism: in response to EGF, UCK2 physically interacts with EGFR to block EGF-induced EGFR ubiquitination and degradation, resulting in elevated EGFR-AKT pathway activation. Site-directed mutagenesis confirmed this function is independent of UCK2 catalytic activity.\",\n      \"method\": \"Site-directed mutagenesis, Co-immunoprecipitation, functional metastasis assays, pharmacological inhibition\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with mutagenesis distinguishing catalytic vs non-catalytic roles, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33277463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"mTORC1 controls UCK2 protein stability (half-life) in the pyrimidine salvage pathway: when mTORC1 is inhibited, UCK2 is degraded via the CTLH-WDR26 E3 ubiquitin ligase complex; active mTORC1 prevents this degradation. Additionally, UCK1 (an isoform) influences UCK2 turnover by affecting its cellular localization.\",\n      \"method\": \"Protein stability/turnover assays, genetic knockdown/knockout of CTLH-WDR26 components, subcellular fractionation, pyrimidine salvage flux assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO/KD with defined biochemical phenotype, multiple pathway components tested, single lab with orthogonal methods\",\n      \"pmids\": [\"39808525\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Under glucose limitation, AMPK phosphorylates GART at Ser440, which facilitates GART binding to UCK2. GART binding (and its production of tetrahydrofolate, THF) inhibits ILKAP phosphatase activity, thereby maintaining AKT1-mediated UCK2-Ser254 phosphorylation. Loss of UCK2-Ser254 phosphorylation promotes TRIM21-mediated UCK2 polyubiquitination and proteasomal degradation.\",\n      \"method\": \"Phosphosite mutagenesis, Co-immunoprecipitation, ubiquitination assays, AMPK kinase assays, in vivo tumor models\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — site-specific mutagenesis (Ser254, Ser440), reconstituted pathway with multiple enzymatic steps validated, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"39865175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GLI2 transcriptionally activates HRD1 (an E3 ubiquitin ligase), which in turn mediates ubiquitination and degradation of UCK2, reducing UCK2 protein levels and conferring 5-FU resistance in gastric cancer cells. UCK2 was identified as a critical gene for 5-FU sensitivity via genome-wide CRISPR knockout screen.\",\n      \"method\": \"CRISPR knockout screen (GeCKO v2), overexpression/knockdown functional assays, ubiquitination assays, luciferase reporter for GLI2-HRD1 transcriptional activation, in vivo xenograft\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus functional rescue, ubiquitination assays, single lab with multiple methods\",\n      \"pmids\": [\"40414119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"UCK2 is a homotetrameric enzyme with an allosteric site at the intersubunit interface. Two classes of inhibitors were identified that noncompetitively inhibit UCK2 by reducing kcat without altering KM, confirming the allosteric (not active-site competitive) mechanism.\",\n      \"method\": \"Structure-based drug design, enzyme kinetics (kcat, KM measurements), in vitro enzymatic inhibition assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with kinetic characterization and structural basis identified, single lab with rigorous biochemical methods\",\n      \"pmids\": [\"36190114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UCK2 forms a physical complex with UCKL1 (Uridine-Cytidine Kinase Like-1) that functions as a molecular scaffold independent of metabolic activity. This UCK2/UCKL1 complex recruits E3 ubiquitin ligase TRIM21, orchestrating ubiquitination and degradation of Smurf2, thereby sustaining Smad3 phosphorylation and amplifying fibrogenic TGF-β signaling in cardiac fibroblasts.\",\n      \"method\": \"Co-immunoprecipitation, genetic silencing (siRNA/shRNA), AAV-mediated knockdown in murine MI model, western blotting for pathway components, murine cardiac fibrosis model\",\n      \"journal\": \"Molecular biomedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP and in vivo model, single lab, novel non-metabolic scaffold function not yet independently replicated\",\n      \"pmids\": [\"41457201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UCK2 (and UCK1) phosphorylate N4-hydroxycytidine (NHC), the active compound of the antiviral molnupiravir. UCK2 displays 9-fold higher catalytic efficiency than UCK1 for NHC. siRNA-mediated knockdown of UCK2 in SARS-CoV-2-infected cells reduced intracellular triphosphate NHC metabolite accumulation and decreased antiviral efficacy 10-fold, establishing UCK2 as the rate-limiting kinase for molnupiravir bioactivation.\",\n      \"method\": \"Target engagement assays, enzyme kinetic assays with recombinant UCK1/UCK2, siRNA knockdown in SARS-CoV-2-infected cells, intracellular metabolite quantification\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic reconstitution with kinetics plus cellular siRNA validation, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.05.13.653844\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UCK2-mediated phosphorylation of cytidine is required for CTP uptake by Chlamydia trachomatis: host UCK2 must convert cytidine to its phosphorylated form prior to incorporation into bacterial nucleic acids, indicating nucleosides are phosphorylated in the host cytoplasm before translocation into the bacterial inclusion.\",\n      \"method\": \"Click chemistry coupled with fluorescence microscopy tracking cytidine incorporation, UCK2-dependent phosphorylation assay in infected cells\",\n      \"journal\": \"microPublication biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct experimental demonstration with orthogonal labeling method, single study, single lab\",\n      \"pmids\": [\"40415900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Overexpression of UCK2 in donor cells enhanced 5-ethynyl uridine (5-EU) incorporation into nascent RNA, demonstrating that UCK2 kinase activity directly controls the intracellular availability of this uridine analog for RNA incorporation. This establishes UCK2 as the rate-limiting kinase for uridine analog phosphorylation in living cells.\",\n      \"method\": \"UCK2 overexpression, metabolic labeling with 5-EU, click chemistry fluorescence detection, quantification in isolated extracellular vesicles\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single overexpression experiment used as tool for EV labeling, mechanistic detail on UCK2 itself is incidental, preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.08.28.672797\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cytotoxicity of epigenetic ribopyrimidines in human cells is mediated primarily by UCK2 kinase activity, as demonstrated by identification of UCK2 as the metabolic regulator governing incorporation of these modified nucleosides into cellular RNA.\",\n      \"method\": \"Cell growth assays with UCK2 modulation, quantification of misincorporation into cellular RNAs, metabolic regulator screening\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, limited mechanistic detail on UCK2 mechanism in abstract\",\n      \"pmids\": [\"bio_10.1101_2025.06.11.659152\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 1976,\n      \"finding\": \"UMPK (UCK2) enzyme activity declines during red cell aging; the lower activity of the UMPK2 allelic variant compared to UMPK1 is explained by more rapid catabolism of the UMPK2 gene product, not by a difference in intrinsic specific activity.\",\n      \"method\": \"Red cell fractionation by age, enzyme activity measurement across red cell age cohorts\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — enzyme activity measurements in aged red cell fractions, single study, no molecular mechanism defined\",\n      \"pmids\": [\"178178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UCK2 physically interacts with the small GTPase RHEB and regulates mTOR signaling in lung adenocarcinoma cells, promoting cell proliferation and migration.\",\n      \"method\": \"Co-immunoprecipitation, overexpression functional assays, pathway analysis\",\n      \"journal\": \"Oncology research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP experiment, single lab, limited mechanistic follow-up described in abstract\",\n      \"pmids\": [\"42232606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UCK2 promotes intrahepatic cholangiocarcinoma progression and cisplatin resistance by activating the PI3K/AKT/mTOR signaling pathway, which inhibits autophagy.\",\n      \"method\": \"UCK2 knockdown/overexpression, western blotting for PI3K/AKT/mTOR/autophagy markers, in vivo and in vitro cisplatin sensitivity assays\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — KD/OE with pathway marker readout, no direct mechanistic link between UCK2 and PI3K established, single lab\",\n      \"pmids\": [\"39179560\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UCK2 is the rate-limiting enzyme of the pyrimidine salvage pathway that phosphorylates uridine and cytidine to UMP and CMP; its protein stability is regulated by mTORC1 (via CTLH-WDR26 E3-mediated degradation when mTORC1 is inactive) and by a GART-ILKAP-AKT1 axis that protects UCK2-Ser254 phosphorylation from TRIM21-mediated ubiquitination under nutrient stress; additionally, UCK2 exerts non-metabolic, catalysis-independent functions including scaffolding EGFR to block its ubiquitination and activate the EGFR-AKT metastatic pathway, and forming a UCK2/UCKL1 complex that recruits TRIM21 to degrade Smurf2 and amplify TGF-β/Smad3 fibrogenic signaling; UCK2 also contains an allosteric site at its homotetrameric intersubunit interface that can be targeted to reduce kcat without affecting KM.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"UCK2 is the rate-limiting kinase of the pyrimidine salvage pathway, phosphorylating uridine and cytidine and thereby controlling the intracellular availability of natural and analog pyrimidine nucleosides for nucleic acid incorporation [#7, #8]. Its catalytic role determines the activation of therapeutically and pathologically relevant nucleoside analogs: UCK2 is the rate-limiting kinase that bioactivates the molnupiravir metabolite N4-hydroxycytidine, with knockdown reducing intracellular triphosphate accumulation and antiviral efficacy [#6], and it governs the cytotoxic misincorporation of modified ribopyrimidines into cellular RNA [#9]. UCK2 functions as a homotetramer with an allosteric site at the intersubunit interface that can be inhibited noncompetitively, reducing kcat without altering KM [#4]. Beyond catalysis, UCK2 exerts catalysis-independent scaffolding functions: in hepatocellular carcinoma it binds EGFR to block its EGF-induced ubiquitination and degradation, sustaining EGFR-AKT signaling and metastasis [#0], and it partners with UCKL1 to recruit the E3 ligase TRIM21 and degrade Smurf2, amplifying TGF-\\u03b2/Smad3 fibrogenic signaling in cardiac fibroblasts [#5]. UCK2 protein abundance is tightly controlled by competing degradation pathways: mTORC1 stabilizes UCK2 while its inactivation triggers CTLH-WDR26 E3-mediated turnover [#1], and a glucose-stress AMPK-GART-ILKAP-AKT1 axis maintains UCK2-Ser254 phosphorylation to protect it from TRIM21-mediated ubiquitination [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 1976,\n      \"claim\": \"Established that UCK2 (UMPK) enzyme activity is set by protein turnover rather than intrinsic catalytic differences, providing the first link between UCK2 abundance and post-synthetic stability.\",\n      \"evidence\": \"Enzyme activity measurement across age-fractionated red cells comparing UMPK allelic variants\",\n      \"pmids\": [\"178178\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No molecular degradation mechanism defined\", \"Allelic variant identity at protein level not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed that UCK2 has a non-metabolic function, scaffolding EGFR to prevent its ubiquitination and driving metastasis independent of kinase activity, reframing UCK2 as more than a salvage enzyme.\",\n      \"evidence\": \"Catalytic-dead mutagenesis, reciprocal Co-IP, and metastasis assays in hepatocellular carcinoma\",\n      \"pmids\": [\"33277463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"EGFR-binding interface on UCK2 not mapped\", \"Whether tetramerization affects scaffolding unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined UCK2 as a homotetramer with an allosteric intersubunit site that can be targeted noncompetitively, establishing a druggable regulatory mechanism distinct from active-site competition.\",\n      \"evidence\": \"Structure-based drug design with kcat/KM kinetic characterization of inhibitor classes in vitro\",\n      \"pmids\": [\"36190114\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological allosteric ligand unidentified\", \"Link between allostery and scaffold function untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed UCK2 protein stability is governed by competing nutrient-sensing degradation circuits, integrating UCK2 abundance into mTORC1 and AMPK signaling states.\",\n      \"evidence\": \"CTLH-WDR26 KO/KD and turnover assays (mTORC1 axis) plus phosphosite mutagenesis of Ser254/Ser440 with ubiquitination assays (AMPK-GART-ILKAP-AKT1-TRIM21 axis) in tumor models\",\n      \"pmids\": [\"39808525\", \"39865175\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interplay between the two degradation routes unresolved\", \"Direct E3-substrate contacts not structurally defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a second catalysis-independent scaffold role in which a UCK2/UCKL1 complex recruits TRIM21 to degrade Smurf2, linking UCK2 to TGF-\\u03b2/Smad3 fibrogenic signaling.\",\n      \"evidence\": \"Co-IP, genetic silencing, and AAV knockdown in a murine cardiac fibrosis (MI) model\",\n      \"pmids\": [\"41457201\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Not independently replicated\", \"How UCK2 toggles between EGFR and UCKL1/TRIM21 scaffolds unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated UCK2 is the rate-limiting kinase for therapeutic and analog pyrimidine nucleosides, controlling molnupiravir bioactivation, uridine-analog RNA labeling, ribopyrimidine cytotoxicity, and host-supplied nucleoside flux to Chlamydia.\",\n      \"evidence\": \"Recombinant enzyme kinetics, siRNA knockdown in SARS-CoV-2 infection, click-chemistry metabolic labeling, and infected-cell incorporation assays (some preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.05.13.653844\", \"40415900\", \"bio_10.1101_2025.08.28.672797\", \"bio_10.1101_2025.06.11.659152\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate selectivity determinants across analogs not mapped\", \"Some findings remain preprint-stage\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected UCK2 to upstream mTOR signaling via physical interaction with RHEB, hinting at a feedback link between UCK2 and the mTORC1 axis that stabilizes it.\",\n      \"evidence\": \"Co-IP and overexpression assays in lung adenocarcinoma cells\",\n      \"pmids\": [\"42232606\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation\", \"Functional consequence of RHEB binding on mTOR not mechanistically established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How UCK2 partitions between its catalytic salvage role and its multiple catalysis-independent scaffold functions, and what governs partner selection (EGFR vs UCKL1/TRIM21 vs RHEB), remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural basis for distinct scaffold complexes\", \"No unified model coupling abundance control to function switching\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [4, 6, 7, 8]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [6, 7, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\n      \"UCK2/UCKL1 complex\",\n      \"UCK2 homotetramer\"\n    ],\n    \"partners\": [\n      \"EGFR\",\n      \"UCKL1\",\n      \"TRIM21\",\n      \"GART\",\n      \"RHEB\",\n      \"WDR26\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}