{"gene":"UTP23","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2006,"finding":"Utp23 is an essential nucleolar protein and component of the SSU processome required for the first three cleavage steps in 18S rRNA maturation. Unlike Utp24, single-point mutations in the conserved putative active site of Utp23 do NOT abrogate its function in ribosome biogenesis, suggesting Utp23's PIN domain is catalytically degenerate.","method":"Yeast depletion strains, localization assays, pre-rRNA processing analysis, active-site mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (depletion, localization, mutagenesis) in a focused study; negative result on catalytic activity of Utp23 active site is explicitly established","pmids":["16769905"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of yeast Utp23 PIN domain (2.5-Å resolution) reveals a conserved PIN domain core fold with degenerate active site residues, a unique CCHC Zn-finger motif, and terminal extension elements. Mutations in three cysteine ligands of the Zn-finger (but not the histidine ligand) are lethal or strongly inhibitory to yeast growth. Conserved basic residues in the N-terminal helix extension are critical for growth and in vitro RNA-binding. Deletion of the C-terminal tail disrupts interaction with snR30 snoRNA and perturbs pre-ribosomal association of Utp23.","method":"X-ray crystallography, in vivo mutagenesis/growth assays, in vitro RNA-binding assays, co-immunoprecipitation","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and in vitro functional assays in a single focused study","pmids":["24152547"],"is_preprint":false},{"year":2014,"finding":"Depletion of Utp23 in mouse cells disrupts endonucleolytic cleavages in ITS1 of the pre-rRNA transcript, specifically affecting maturation of the small ribosomal subunit, as shown by RAMP (Ratio Analysis of Multiple Precursors) profiling of pre-rRNA intermediates.","method":"siRNA knockdown in mouse cells, RAMP (quantitative pre-rRNA ratio analysis by Northern blotting)","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean knockdown with defined pre-rRNA processing phenotype, single lab but two complementary methods (depletion + RAMP)","pmids":["25190460"],"is_preprint":false},{"year":2022,"finding":"In vitro reconstitution of the yeast snR30 RNP showed that Utp23 binds tightly but non-specifically to RNA on its own; however, in complex with the snR30 RNP, Utp23 increases the affinity of the RNP for rRNA, revealing synergy where snR30 provides specificity and Utp23 enhances overall affinity. The snR30 RNP is anchored on pre-rRNA through base-pairing to expansion segment 6 (ES6) of 18S rRNA, and Utp23 binds tightly to snR30.","method":"In vitro reconstitution of snR30 RNP, quantitative binding assays (EMSAs, fluorescence-based), deletion/mutation analysis of rRNA binding sites","journal":"RNA biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with quantitative binding characterization; single lab but multiple orthogonal binding assays","pmids":["35648701"],"is_preprint":false},{"year":2023,"finding":"DCAF13 promotes NPM1 phase separation in the nucleolus to form biomolecular condensates that recruit UTP23, and UTP23 acts as the endonuclease for 18S rRNA maturation in this context. DCAF13 depletion causes 18S rRNA maturation failure, abnormal ribosome assembly, and impairs T cell proliferation.","method":"Genetic depletion (siRNA/CRISPR) in T cells, phase separation assays, pre-rRNA processing analysis, co-localization/imaging","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular and molecular phenotype, mechanistic model supported by phase separation and rRNA processing assays, single lab","pmids":["37615668"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structural analysis reveals that snR30 (human U17) binds with H/ACA proteins (Cbf5-Gar1-Nop10-Nhp2) to a pre-18S rRNA subdomain containing platform helices and ES6 of the 40S central domain. Utp23 is recruited as part of the Krr1-Utp23-Kri1 assembly factor complex together with ribosomal proteins uS11 and uS15, enabling isolated subdomain assembly prior to integration into the 90S pre-ribosome. Krr1-dependent release of snR30 is required for platform integration into the 90S.","method":"Cryo-EM structural analysis, in vivo assembly factor depletion, pre-rRNA processing assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure with functional validation of assembly factor dependencies; single study but multiple orthogonal methods","pmids":["40399280"],"is_preprint":false},{"year":2024,"finding":"Loss of UTP23 in human pancreatic beta cells (EndoC-βH3) markedly reduces cell viability, as shown by CRISPR-Cas9-mediated deletion in the context of SLC30A8 locus enhancer deletions.","method":"CRISPR-Cas9 gene deletion in human-derived EndoC-βH3 cells, cell viability assays","journal":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KO with specific cellular phenotype (viability), single lab, single method","pmids":["38661000"],"is_preprint":false},{"year":2024,"finding":"Cytoplasmic (but not nucleolar) localization of UTP23 in colorectal cancer cells promotes metastatic and invasive capabilities. Mass spectrometry identified KRT5 as a binding partner of cytoplasmic UTP23, and KRT5 exerts a regulatory influence on UTP23's metastatic potential.","method":"Subcellular fractionation/immunofluorescence in clinical samples and cell lines, functional invasion/migration assays with cytoplasmic vs. nucleolar UTP23, mass spectrometry co-immunoprecipitation","journal":"Cellular and molecular biology (Noisy-le-Grand, France)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP/MS for KRT5 interaction, functional assay with localization variant, single lab without extensive mechanistic follow-up","pmids":["38372088"],"is_preprint":false}],"current_model":"UTP23 is a conserved nucleolar protein with a catalytically degenerate PIN domain and a CCHC Zn-finger motif that functions as an essential component of the SSU processome (90S pre-ribosome), where it binds the snR30/U17 H/ACA snoRNP and rRNA (via ES6) to facilitate early cleavage steps in 18S rRNA maturation; its C-terminal tail mediates snR30 interaction, its N-terminal basic residues mediate RNA binding, and in the context of T cell activation it is recruited into nucleolar NPM1/DCAF13 phase-separated condensates to execute 18S rRNA processing, while aberrant cytoplasmic relocalization in cancer cells engages KRT5 to promote invasion independently of its ribosome-biogenesis function."},"narrative":{"mechanistic_narrative":"UTP23 is a conserved, essential nucleolar protein that functions in early small ribosomal subunit (SSU) biogenesis, where it is required for the endonucleolytic cleavage steps that mature 18S rRNA [PMID:16769905, PMID:25190460]. It adopts a PIN-domain core fold whose putative active-site residues are catalytically degenerate — single active-site point mutations do not abrogate its function — distinguishing it from the active endonuclease Utp24 [PMID:16769905, PMID:24152547]. The structured core is decorated with functional appendages: a CCHC Zn-finger whose cysteine ligands are essential for viability, N-terminal basic helix residues required for RNA binding, and a C-terminal tail that mediates association with the snR30/U17 H/ACA snoRNP and pre-ribosomal incorporation [PMID:24152547]. Mechanistically, UTP23 binds RNA tightly but non-specifically on its own and acts in synergy with the snR30 RNP, which provides sequence specificity by base-pairing to expansion segment 6 (ES6) of 18S rRNA while UTP23 enhances overall RNP affinity for the pre-rRNA [PMID:35648701]. Cryo-EM shows UTP23 is recruited within a Krr1-UTP23-Kri1 assembly-factor module alongside ribosomal proteins uS11 and uS15 to build an isolated 40S central-domain subdomain prior to its Krr1-dependent integration into the 90S pre-ribosome [PMID:40399280]. In activated T cells, DCAF13-driven NPM1 phase separation forms nucleolar condensates that recruit UTP23 to execute 18S rRNA maturation [PMID:37615668]. Beyond its canonical nucleolar role, cytoplasmic relocalization of UTP23 in colorectal cancer cells engages KRT5 to promote invasion and metastasis [PMID:38372088].","teleology":[{"year":2006,"claim":"Established that UTP23 is an essential SSU processome component for early 18S rRNA cleavages and, unexpectedly, that its PIN domain active site is catalytically degenerate rather than a functional nuclease.","evidence":"Yeast depletion strains, nucleolar localization, pre-rRNA processing analysis, and active-site mutagenesis","pmids":["16769905"],"confidence":"High","gaps":["Did not resolve which residues/domains drive function if not catalysis","No structural basis for the degenerate active site"]},{"year":2013,"claim":"Defined the domain architecture underlying UTP23 function by solving the PIN-domain structure and assigning roles to the CCHC Zn-finger (viability), N-terminal basic residues (RNA binding), and C-terminal tail (snR30 interaction and pre-ribosome association).","evidence":"X-ray crystallography of yeast Utp23 PIN domain plus in vivo mutagenesis, in vitro RNA-binding, and co-immunoprecipitation","pmids":["24152547"],"confidence":"High","gaps":["Mechanism by which the Zn-finger contributes to viability unresolved","Structure of UTP23 within an intact RNP not determined"]},{"year":2014,"claim":"Extended the rRNA-processing role to mammalian cells, showing UTP23 depletion specifically disrupts ITS1 cleavages required for SSU maturation.","evidence":"siRNA knockdown in mouse cells with RAMP quantitative pre-rRNA profiling","pmids":["25190460"],"confidence":"Medium","gaps":["Direct enzymatic versus scaffolding contribution not separated","Single-lab knockdown without rescue"]},{"year":2022,"claim":"Resolved how UTP23 achieves specificity by showing it binds RNA non-specifically alone but synergizes with the snR30 RNP, which anchors to ES6 of 18S rRNA, with UTP23 boosting RNP affinity for pre-rRNA.","evidence":"In vitro reconstitution of the yeast snR30 RNP with quantitative EMSA and fluorescence binding assays and deletion/mutation mapping","pmids":["35648701"],"confidence":"High","gaps":["In vitro reconstitution does not capture full 90S context","Functional consequence of affinity enhancement on cleavage timing untested"]},{"year":2023,"claim":"Linked UTP23 recruitment to nucleolar phase separation, showing DCAF13-driven NPM1 condensates recruit UTP23 to carry out 18S rRNA maturation during T cell proliferation.","evidence":"Genetic depletion in T cells, phase separation and co-localization imaging, and pre-rRNA processing analysis","pmids":["37615668"],"confidence":"Medium","gaps":["Whether UTP23 itself is the cleaving endonuclease conflicts with the catalytically degenerate PIN domain evidence","Direct UTP23-condensate biophysical interaction not isolated"]},{"year":2024,"claim":"Demonstrated a non-canonical, localization-dependent oncogenic role in which cytoplasmic UTP23 binds KRT5 to promote colorectal cancer invasion and metastasis.","evidence":"Subcellular fractionation/immunofluorescence in clinical samples and lines, invasion/migration assays comparing cytoplasmic versus nucleolar UTP23, and mass-spectrometry co-IP","pmids":["38372088"],"confidence":"Low","gaps":["Single Co-IP/MS for KRT5 without reciprocal validation","Mechanism driving cytoplasmic relocalization unknown","Independence from ribosome-biogenesis function not rigorously established"]},{"year":2024,"claim":"Provided evidence that UTP23 is required for survival of a human endocrine cell type, with CRISPR deletion sharply reducing pancreatic beta-cell viability.","evidence":"CRISPR-Cas9 deletion in EndoC-βH3 cells with viability assays","pmids":["38661000"],"confidence":"Medium","gaps":["Mechanism of lethality (presumed ribosome biogenesis) not directly shown","Single method, single lab"]},{"year":2025,"claim":"Placed UTP23 in a structural assembly pathway, showing it acts within a Krr1-UTP23-Kri1 module with uS11/uS15 to build an isolated 40S central-domain subdomain that is integrated into the 90S after Krr1-dependent snR30 release.","evidence":"Cryo-EM structural analysis with in vivo assembly-factor depletion and pre-rRNA processing assays","pmids":["40399280"],"confidence":"High","gaps":["Temporal coordination between subdomain assembly and cleavage not fully defined","UTP23's precise catalytic versus scaffolding role at integration unresolved"]},{"year":null,"claim":"Whether UTP23 contributes any direct catalytic activity to 18S rRNA cleavage, or acts purely as an RNA-binding scaffold/recruitment factor, remains unresolved given its degenerate PIN active site.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconciliation between degenerate active-site evidence and reported endonuclease role","No reconstituted cleavage assay assigning catalysis to UTP23"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[1,3]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0,4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,2,5]}],"complexes":["SSU processome (90S pre-ribosome)","snR30/U17 H/ACA snoRNP","Krr1-UTP23-Kri1 assembly module"],"partners":["SNR30","KRR1","KRI1","US11","US15","DCAF13","NPM1","KRT5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BRU9","full_name":"rRNA-processing protein UTP23 homolog","aliases":[],"length_aa":249,"mass_kda":28.4,"function":"Involved in rRNA-processing and ribosome biogenesis","subcellular_location":"Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/Q9BRU9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/UTP23","classification":"Common Essential","n_dependent_lines":1060,"n_total_lines":1208,"dependency_fraction":0.8774834437086093},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/UTP23","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/UTP23"},"hgnc":{"alias_symbol":["MGC14595"],"prev_symbol":["C8orf53"]},"alphafold":{"accession":"Q9BRU9","domains":[{"cath_id":"3.40.50.1010","chopping":"2-13_23-158","consensus_level":"high","plddt":94.5847,"start":2,"end":158}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BRU9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BRU9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BRU9-F1-predicted_aligned_error_v6.png","plddt_mean":82.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UTP23","jax_strain_url":"https://www.jax.org/strain/search?query=UTP23"},"sequence":{"accession":"Q9BRU9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BRU9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BRU9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BRU9"}},"corpus_meta":[{"pmid":"22367214","id":"PMC_22367214","title":"Characterization of gene-environment interactions for colorectal cancer susceptibility loci.","date":"2012","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/22367214","citation_count":149,"is_preprint":false},{"pmid":"25607466","id":"PMC_25607466","title":"TXNDC17 promotes paclitaxel resistance via inducing autophagy in ovarian cancer.","date":"2015","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/25607466","citation_count":146,"is_preprint":false},{"pmid":"16769905","id":"PMC_16769905","title":"The PINc domain protein Utp24, a putative nuclease, is required for the early cleavage steps in 18S rRNA maturation.","date":"2006","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16769905","citation_count":84,"is_preprint":false},{"pmid":"25190460","id":"PMC_25190460","title":"Two orthogonal cleavages separate subunit RNAs in mouse ribosome biogenesis.","date":"2014","source":"Nucleic acids 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model.","date":"2017","source":"Diabetologia","url":"https://pubmed.ncbi.nlm.nih.gov/28321468","citation_count":30,"is_preprint":false},{"pmid":"24152547","id":"PMC_24152547","title":"Structural and functional analysis of Utp23, a yeast ribosome synthesis factor with degenerate PIN domain.","date":"2013","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/24152547","citation_count":23,"is_preprint":false},{"pmid":"26553438","id":"PMC_26553438","title":"Recurrent Coding Sequence Variation Explains Only A Small Fraction of the Genetic Architecture of Colorectal Cancer.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26553438","citation_count":23,"is_preprint":false},{"pmid":"37615668","id":"PMC_37615668","title":"T cell proliferation requires ribosomal maturation in nucleolar condensates dependent on DCAF13.","date":"2023","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/37615668","citation_count":16,"is_preprint":false},{"pmid":"35648701","id":"PMC_35648701","title":"Synergistic interaction network between the snR30 RNP, Utp23, and ribosomal RNA during ribosome synthesis.","date":"2022","source":"RNA biology","url":"https://pubmed.ncbi.nlm.nih.gov/35648701","citation_count":9,"is_preprint":false},{"pmid":"29641590","id":"PMC_29641590","title":"Structural and functional analysis of Utp24, an endonuclease for processing 18S ribosomal RNA.","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/29641590","citation_count":9,"is_preprint":false},{"pmid":"38661000","id":"PMC_38661000","title":"Multiple genetic variants at the SLC30A8 locus affect local super-enhancer activity and influence pancreatic β-cell survival and function.","date":"2024","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/38661000","citation_count":5,"is_preprint":false},{"pmid":"40399280","id":"PMC_40399280","title":"H/ACA snR30 snoRNP guides independent 18S rRNA subdomain formation.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40399280","citation_count":4,"is_preprint":false},{"pmid":"38433915","id":"PMC_38433915","title":"Differential alternative splicing landscape identifies potentially functional RNA binding proteins in early embryonic development in mammals.","date":"2024","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/38433915","citation_count":4,"is_preprint":false},{"pmid":"38350227","id":"PMC_38350227","title":"Genome-wide association and functional annotation analysis for the calving interval in Nellore cattle.","date":"2024","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/38350227","citation_count":4,"is_preprint":false},{"pmid":"38372088","id":"PMC_38372088","title":"Cytoplasmic expression of UTP23 promotes colorectal cancer progression.","date":"2024","source":"Cellular and molecular biology (Noisy-le-Grand, France)","url":"https://pubmed.ncbi.nlm.nih.gov/38372088","citation_count":1,"is_preprint":false},{"pmid":"37502937","id":"PMC_37502937","title":"Multiple genetic variants at the SLC30A8 locus affect local super-enhancer activity and influence pancreatic β-cell survival and function.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37502937","citation_count":1,"is_preprint":false},{"pmid":"37733425","id":"PMC_37733425","title":"Nucleolar condensates: A cellular machinery necessary for T cell activation.","date":"2023","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/37733425","citation_count":1,"is_preprint":false},{"pmid":"38665548","id":"PMC_38665548","title":"Relationship between 233 colorectal cancer risk loci and survival in 1926 patients with advanced disease.","date":"2023","source":"BJC reports","url":"https://pubmed.ncbi.nlm.nih.gov/38665548","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11851,"output_tokens":2280,"usd":0.034876,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9311,"output_tokens":3114,"usd":0.062203,"stage2_stop_reason":"end_turn"},"total_usd":0.097079,"stage1_batch_id":"msgbatch_01UT1AahFPCAyn2uVweS7A9z","stage2_batch_id":"msgbatch_01HuKWtKNT4Pqj1bc8eEP5RV","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"Utp23 is an essential nucleolar protein and component of the SSU processome required for the first three cleavage steps in 18S rRNA maturation. Unlike Utp24, single-point mutations in the conserved putative active site of Utp23 do NOT abrogate its function in ribosome biogenesis, suggesting Utp23's PIN domain is catalytically degenerate.\",\n      \"method\": \"Yeast depletion strains, localization assays, pre-rRNA processing analysis, active-site mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (depletion, localization, mutagenesis) in a focused study; negative result on catalytic activity of Utp23 active site is explicitly established\",\n      \"pmids\": [\"16769905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of yeast Utp23 PIN domain (2.5-Å resolution) reveals a conserved PIN domain core fold with degenerate active site residues, a unique CCHC Zn-finger motif, and terminal extension elements. Mutations in three cysteine ligands of the Zn-finger (but not the histidine ligand) are lethal or strongly inhibitory to yeast growth. Conserved basic residues in the N-terminal helix extension are critical for growth and in vitro RNA-binding. Deletion of the C-terminal tail disrupts interaction with snR30 snoRNA and perturbs pre-ribosomal association of Utp23.\",\n      \"method\": \"X-ray crystallography, in vivo mutagenesis/growth assays, in vitro RNA-binding assays, co-immunoprecipitation\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and in vitro functional assays in a single focused study\",\n      \"pmids\": [\"24152547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Depletion of Utp23 in mouse cells disrupts endonucleolytic cleavages in ITS1 of the pre-rRNA transcript, specifically affecting maturation of the small ribosomal subunit, as shown by RAMP (Ratio Analysis of Multiple Precursors) profiling of pre-rRNA intermediates.\",\n      \"method\": \"siRNA knockdown in mouse cells, RAMP (quantitative pre-rRNA ratio analysis by Northern blotting)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockdown with defined pre-rRNA processing phenotype, single lab but two complementary methods (depletion + RAMP)\",\n      \"pmids\": [\"25190460\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In vitro reconstitution of the yeast snR30 RNP showed that Utp23 binds tightly but non-specifically to RNA on its own; however, in complex with the snR30 RNP, Utp23 increases the affinity of the RNP for rRNA, revealing synergy where snR30 provides specificity and Utp23 enhances overall affinity. The snR30 RNP is anchored on pre-rRNA through base-pairing to expansion segment 6 (ES6) of 18S rRNA, and Utp23 binds tightly to snR30.\",\n      \"method\": \"In vitro reconstitution of snR30 RNP, quantitative binding assays (EMSAs, fluorescence-based), deletion/mutation analysis of rRNA binding sites\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with quantitative binding characterization; single lab but multiple orthogonal binding assays\",\n      \"pmids\": [\"35648701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DCAF13 promotes NPM1 phase separation in the nucleolus to form biomolecular condensates that recruit UTP23, and UTP23 acts as the endonuclease for 18S rRNA maturation in this context. DCAF13 depletion causes 18S rRNA maturation failure, abnormal ribosome assembly, and impairs T cell proliferation.\",\n      \"method\": \"Genetic depletion (siRNA/CRISPR) in T cells, phase separation assays, pre-rRNA processing analysis, co-localization/imaging\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular and molecular phenotype, mechanistic model supported by phase separation and rRNA processing assays, single lab\",\n      \"pmids\": [\"37615668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structural analysis reveals that snR30 (human U17) binds with H/ACA proteins (Cbf5-Gar1-Nop10-Nhp2) to a pre-18S rRNA subdomain containing platform helices and ES6 of the 40S central domain. Utp23 is recruited as part of the Krr1-Utp23-Kri1 assembly factor complex together with ribosomal proteins uS11 and uS15, enabling isolated subdomain assembly prior to integration into the 90S pre-ribosome. Krr1-dependent release of snR30 is required for platform integration into the 90S.\",\n      \"method\": \"Cryo-EM structural analysis, in vivo assembly factor depletion, pre-rRNA processing assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure with functional validation of assembly factor dependencies; single study but multiple orthogonal methods\",\n      \"pmids\": [\"40399280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of UTP23 in human pancreatic beta cells (EndoC-βH3) markedly reduces cell viability, as shown by CRISPR-Cas9-mediated deletion in the context of SLC30A8 locus enhancer deletions.\",\n      \"method\": \"CRISPR-Cas9 gene deletion in human-derived EndoC-βH3 cells, cell viability assays\",\n      \"journal\": \"FASEB journal : official publication of the Federation of American Societies for Experimental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KO with specific cellular phenotype (viability), single lab, single method\",\n      \"pmids\": [\"38661000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cytoplasmic (but not nucleolar) localization of UTP23 in colorectal cancer cells promotes metastatic and invasive capabilities. Mass spectrometry identified KRT5 as a binding partner of cytoplasmic UTP23, and KRT5 exerts a regulatory influence on UTP23's metastatic potential.\",\n      \"method\": \"Subcellular fractionation/immunofluorescence in clinical samples and cell lines, functional invasion/migration assays with cytoplasmic vs. nucleolar UTP23, mass spectrometry co-immunoprecipitation\",\n      \"journal\": \"Cellular and molecular biology (Noisy-le-Grand, France)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/MS for KRT5 interaction, functional assay with localization variant, single lab without extensive mechanistic follow-up\",\n      \"pmids\": [\"38372088\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UTP23 is a conserved nucleolar protein with a catalytically degenerate PIN domain and a CCHC Zn-finger motif that functions as an essential component of the SSU processome (90S pre-ribosome), where it binds the snR30/U17 H/ACA snoRNP and rRNA (via ES6) to facilitate early cleavage steps in 18S rRNA maturation; its C-terminal tail mediates snR30 interaction, its N-terminal basic residues mediate RNA binding, and in the context of T cell activation it is recruited into nucleolar NPM1/DCAF13 phase-separated condensates to execute 18S rRNA processing, while aberrant cytoplasmic relocalization in cancer cells engages KRT5 to promote invasion independently of its ribosome-biogenesis function.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"UTP23 is a conserved, essential nucleolar protein that functions in early small ribosomal subunit (SSU) biogenesis, where it is required for the endonucleolytic cleavage steps that mature 18S rRNA [#0, #2]. It adopts a PIN-domain core fold whose putative active-site residues are catalytically degenerate — single active-site point mutations do not abrogate its function — distinguishing it from the active endonuclease Utp24 [#0, #1]. The structured core is decorated with functional appendages: a CCHC Zn-finger whose cysteine ligands are essential for viability, N-terminal basic helix residues required for RNA binding, and a C-terminal tail that mediates association with the snR30/U17 H/ACA snoRNP and pre-ribosomal incorporation [#1]. Mechanistically, UTP23 binds RNA tightly but non-specifically on its own and acts in synergy with the snR30 RNP, which provides sequence specificity by base-pairing to expansion segment 6 (ES6) of 18S rRNA while UTP23 enhances overall RNP affinity for the pre-rRNA [#3]. Cryo-EM shows UTP23 is recruited within a Krr1-UTP23-Kri1 assembly-factor module alongside ribosomal proteins uS11 and uS15 to build an isolated 40S central-domain subdomain prior to its Krr1-dependent integration into the 90S pre-ribosome [#5]. In activated T cells, DCAF13-driven NPM1 phase separation forms nucleolar condensates that recruit UTP23 to execute 18S rRNA maturation [#4]. Beyond its canonical nucleolar role, cytoplasmic relocalization of UTP23 in colorectal cancer cells engages KRT5 to promote invasion and metastasis [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that UTP23 is an essential SSU processome component for early 18S rRNA cleavages and, unexpectedly, that its PIN domain active site is catalytically degenerate rather than a functional nuclease.\",\n      \"evidence\": \"Yeast depletion strains, nucleolar localization, pre-rRNA processing analysis, and active-site mutagenesis\",\n      \"pmids\": [\"16769905\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which residues/domains drive function if not catalysis\", \"No structural basis for the degenerate active site\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the domain architecture underlying UTP23 function by solving the PIN-domain structure and assigning roles to the CCHC Zn-finger (viability), N-terminal basic residues (RNA binding), and C-terminal tail (snR30 interaction and pre-ribosome association).\",\n      \"evidence\": \"X-ray crystallography of yeast Utp23 PIN domain plus in vivo mutagenesis, in vitro RNA-binding, and co-immunoprecipitation\",\n      \"pmids\": [\"24152547\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which the Zn-finger contributes to viability unresolved\", \"Structure of UTP23 within an intact RNP not determined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Extended the rRNA-processing role to mammalian cells, showing UTP23 depletion specifically disrupts ITS1 cleavages required for SSU maturation.\",\n      \"evidence\": \"siRNA knockdown in mouse cells with RAMP quantitative pre-rRNA profiling\",\n      \"pmids\": [\"25190460\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct enzymatic versus scaffolding contribution not separated\", \"Single-lab knockdown without rescue\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved how UTP23 achieves specificity by showing it binds RNA non-specifically alone but synergizes with the snR30 RNP, which anchors to ES6 of 18S rRNA, with UTP23 boosting RNP affinity for pre-rRNA.\",\n      \"evidence\": \"In vitro reconstitution of the yeast snR30 RNP with quantitative EMSA and fluorescence binding assays and deletion/mutation mapping\",\n      \"pmids\": [\"35648701\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro reconstitution does not capture full 90S context\", \"Functional consequence of affinity enhancement on cleavage timing untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked UTP23 recruitment to nucleolar phase separation, showing DCAF13-driven NPM1 condensates recruit UTP23 to carry out 18S rRNA maturation during T cell proliferation.\",\n      \"evidence\": \"Genetic depletion in T cells, phase separation and co-localization imaging, and pre-rRNA processing analysis\",\n      \"pmids\": [\"37615668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether UTP23 itself is the cleaving endonuclease conflicts with the catalytically degenerate PIN domain evidence\", \"Direct UTP23-condensate biophysical interaction not isolated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated a non-canonical, localization-dependent oncogenic role in which cytoplasmic UTP23 binds KRT5 to promote colorectal cancer invasion and metastasis.\",\n      \"evidence\": \"Subcellular fractionation/immunofluorescence in clinical samples and lines, invasion/migration assays comparing cytoplasmic versus nucleolar UTP23, and mass-spectrometry co-IP\",\n      \"pmids\": [\"38372088\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP/MS for KRT5 without reciprocal validation\", \"Mechanism driving cytoplasmic relocalization unknown\", \"Independence from ribosome-biogenesis function not rigorously established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided evidence that UTP23 is required for survival of a human endocrine cell type, with CRISPR deletion sharply reducing pancreatic beta-cell viability.\",\n      \"evidence\": \"CRISPR-Cas9 deletion in EndoC-βH3 cells with viability assays\",\n      \"pmids\": [\"38661000\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of lethality (presumed ribosome biogenesis) not directly shown\", \"Single method, single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed UTP23 in a structural assembly pathway, showing it acts within a Krr1-UTP23-Kri1 module with uS11/uS15 to build an isolated 40S central-domain subdomain that is integrated into the 90S after Krr1-dependent snR30 release.\",\n      \"evidence\": \"Cryo-EM structural analysis with in vivo assembly-factor depletion and pre-rRNA processing assays\",\n      \"pmids\": [\"40399280\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Temporal coordination between subdomain assembly and cleavage not fully defined\", \"UTP23's precise catalytic versus scaffolding role at integration unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether UTP23 contributes any direct catalytic activity to 18S rRNA cleavage, or acts purely as an RNA-binding scaffold/recruitment factor, remains unresolved given its degenerate PIN active site.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconciliation between degenerate active-site evidence and reported endonuclease role\", \"No reconstituted cleavage assay assigning catalysis to UTP23\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"complexes\": [\n      \"SSU processome (90S pre-ribosome)\",\n      \"snR30/U17 H/ACA snoRNP\",\n      \"Krr1-UTP23-Kri1 assembly module\"\n    ],\n    \"partners\": [\n      \"snR30\",\n      \"Krr1\",\n      \"Kri1\",\n      \"uS11\",\n      \"uS15\",\n      \"DCAF13\",\n      \"NPM1\",\n      \"KRT5\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}