{"gene":"NGDN","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1998,"finding":"Yeast LCP5 (ortholog of NGDN) is required for early pre-rRNA cleavage steps (A0 to A2) that lead to 18S rRNA maturation; depletion of Lcp5p impairs pre-rRNA processing and reduces polysome levels. Indirect immunofluorescence showed predominant nucleolar localization, and anti-Lcp5p antibodies immunoprecipitated the U3 snoRNA (snR17), indicating direct involvement in the pre-rRNA processing machinery.","method":"Temperature-sensitive mutants and in vivo depletion, Northern blot for pre-rRNA intermediates, polysome analysis, indirect immunofluorescence, co-immunoprecipitation of U3 snoRNA","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetic depletion, Northern blot, immunofluorescence, RNA co-IP) in a focused mechanistic study; foundational paper for Lcp5/NGDN function","pmids":["9814757"],"is_preprint":false},{"year":2016,"finding":"Human NGDN forms a salt-stable trimeric complex (ANN complex) with AATF/Che-1 and NOL10; all three subunits localize to nucleoli and exhibit mutual dependence for protein stability. The UTP3/SAS10 domain of NGDN is required for ANN complex formation. Depletion of NGDN (or either partner) impairs 18S rRNA maturation and blocks the same nucleolar cleavage steps in the 5'ETS and ITS1 regions of the pre-rRNA, establishing that NGDN functions in 40S ribosomal subunit biogenesis.","method":"Immunoprecipitation (complex identification), domain-mapping co-IP, siRNA depletion with Northern blot analysis of pre-rRNA processing intermediates, immunofluorescence for nucleolar localization","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with domain mapping, multiple depletions with defined rRNA processing readouts, localization confirmed, all in one focused mechanistic study","pmids":["27599843"],"is_preprint":false},{"year":2008,"finding":"Human CANu1/NGDN (alias of NGDN) localizes to nucleoli via its C-terminal domain; siRNA silencing causes ribosomal stress, G1 cell-cycle arrest, p53 induction, and translocation of nucleolar marker B23. Upon UV damage, CANu1 translocates from nucleoli to nuclear foci with increased mobility (FRAP).","method":"GFP-fusion live-cell imaging, C-terminal deletion constructs for localization mapping, siRNA knockdown with flow cytometry (cell-cycle), Western blot (p53, B23), FRAP after UV damage","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional deletion mapping plus KD phenotype (G1 arrest, p53 induction), single lab with multiple orthogonal methods","pmids":["18547334"],"is_preprint":false},{"year":2011,"finding":"Knockdown of Neuroguidin/CANu1 (NGDN) in human osteosarcoma U2OS cells does not affect viability alone but sensitizes cells to doxorubicin-induced apoptosis; depletion induces p21 expression, PARP cleavage, and increased caspase-3/7 activity. NGDN translocates from nucleoli to nuclear foci in response to doxorubicin.","method":"shRNA knockdown, cell viability assay, annexin V apoptosis assay, Western blot (p21, cleaved PARP), caspase-3/7 activity assay, GFP relocalization","journal":"BMB reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KD with defined apoptotic phenotype and multiple readouts, but single lab, no pathway rescue or epistasis","pmids":["21266106"],"is_preprint":false},{"year":2022,"finding":"CryoEM structure of the yeast Bfr2-Lcp5 (NGDN ortholog) complex within the 90S small subunit processome was determined at 3.99–7.24 Å resolution using AlphaFold-assisted modeling; the Bfr2-Lcp5 interaction architecture mimics that of exosome factors Rrp6-Rrp47, and the complex facilitates incorporation of the 5' domain of 18S rRNA into 90S. Protein-protein interaction mapping and circular dichroism of recombinant proteins validated the structural model.","method":"CryoEM structure determination with AlphaFold assistance, recombinant protein circular dichroism, protein-protein interaction assays","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure with biochemical validation (CD, protein interaction), but single lab and AlphaFold-assisted model in a relatively low-resolution map","pmids":["35650250"],"is_preprint":false}],"current_model":"NGDN (human) is a nucleolar protein whose UTP3/SAS10 domain mediates assembly into the trimeric ANN complex (with AATF and NOL10), which supports nucleolar cleavage steps in the 5'ETS and ITS1 of pre-rRNA required for 18S rRNA maturation and 40S ribosomal subunit biogenesis; its yeast ortholog Lcp5 performs the same function and physically associates with the U3 snoRNA, while structural work on the Bfr2-Lcp5 complex within the 90S processome reveals an Rrp6-Rrp47-like interaction architecture that facilitates 5'-domain incorporation into 90S."},"narrative":{"mechanistic_narrative":"NGDN is a nucleolar protein that functions in the early nucleolar processing of pre-rRNA required for 18S rRNA maturation and 40S ribosomal subunit biogenesis [PMID:27599843]. Its UTP3/SAS10 domain mediates assembly into a salt-stable trimeric ANN complex with AATF/Che-1 and NOL10, in which the three subunits are mutually dependent for protein stability and jointly support nucleolar cleavage of the 5'ETS and ITS1 regions of the pre-rRNA [PMID:27599843]. This role is conserved from the yeast ortholog Lcp5, which is required for the early A0–A2 cleavage steps and physically associates with the U3 snoRNA within the pre-rRNA processing machinery [PMID:9814757]; structural analysis of the yeast Bfr2–Lcp5 complex within the 90S small-subunit processome shows an interaction architecture resembling the Rrp6–Rrp47 exosome pair that facilitates incorporation of the 18S 5' domain into the 90S particle [PMID:35650250]. Consistent with its essential biogenesis role, NGDN depletion provokes ribosomal stress with G1 arrest and p53 induction, and the protein relocalizes from nucleoli to nuclear foci upon genotoxic stress [PMID:18547334, PMID:21266106].","teleology":[{"year":1998,"claim":"Established that the NGDN ortholog acts directly in the pre-rRNA processing machinery rather than as a general translation factor, by tying it to specific early cleavage steps and the U3 snoRNP.","evidence":"Temperature-sensitive/depletion genetics, Northern blot of pre-rRNA intermediates, polysome profiling, immunofluorescence, and U3 snoRNA co-IP in yeast Lcp5","pmids":["9814757"],"confidence":"High","gaps":["Did not define the human ortholog's partners or complex","Mechanism of U3 association (direct vs. via other factors) not resolved"]},{"year":2008,"claim":"Identified the human protein as nucleolar via a C-terminal targeting domain and linked its loss to ribosomal stress signaling, connecting NGDN to cell-cycle and p53 control.","evidence":"GFP live-cell imaging, C-terminal deletion mapping, siRNA with flow cytometry, Western blot for p53/B23, and FRAP after UV in human cells","pmids":["18547334"],"confidence":"Medium","gaps":["The molecular basis of stress-induced relocalization not defined","Did not identify NGDN's protein partners"]},{"year":2011,"claim":"Showed that NGDN depletion is not lethal alone but sensitizes cells to genotoxic apoptosis, refining its role as a modulator of stress-induced cell death.","evidence":"shRNA knockdown, viability and annexin V assays, Western blot (p21, cleaved PARP), caspase-3/7 activity, and GFP relocalization in U2OS cells","pmids":["21266106"],"confidence":"Medium","gaps":["Single cell line, no rescue or epistasis","Link between rRNA processing defect and apoptosis sensitization not mechanistically dissected"]},{"year":2016,"claim":"Defined NGDN's physical context in humans by identifying the trimeric ANN complex and mapping the UTP3/SAS10 domain as the assembly module required for 18S maturation.","evidence":"Reciprocal and domain-mapping co-IP, siRNA depletions with Northern blot of pre-rRNA intermediates, and immunofluorescence in human cells","pmids":["27599843"],"confidence":"High","gaps":["Structural basis of ANN assembly not determined","Functional division of labor among the three subunits unresolved"]},{"year":2022,"claim":"Provided a structural rationale for NGDN ortholog action within the 90S processome, showing its complex mimics an exosome-factor architecture to aid 5'-domain incorporation.","evidence":"CryoEM (3.99–7.24 Å) with AlphaFold-assisted modeling, recombinant circular dichroism, and protein-protein interaction assays of yeast Bfr2-Lcp5","pmids":["35650250"],"confidence":"Medium","gaps":["Relatively low-resolution map with AlphaFold-assisted model","Human ANN complex structure within the processome not determined"]},{"year":null,"claim":"How NGDN's nucleolar pre-rRNA processing role is mechanistically coupled to the p53-dependent ribosomal stress and apoptosis phenotypes remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human structure of the ANN complex on the pre-ribosome","Disease association of NGDN not established in this corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,4]}],"complexes":["ANN complex (NGDN-AATF-NOL10)","90S small subunit processome","Bfr2-Lcp5 complex (yeast)"],"partners":["AATF","NOL10","BFR2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NEJ9","full_name":"Neuroguidin","aliases":["Centromere accumulated nuclear protein 1","CANu1","EIF4E-binding protein"],"length_aa":315,"mass_kda":35.9,"function":"Part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. During the assembly of the SSU processome in the nucleolus, many ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA and work in concert to generate RNA folding, modifications, rearrangements and cleavage as well as targeted degradation of pre-ribosomal RNA by the RNA exosome. Its dissociation from the complex determines the transition from state pre-A1 to state pre-A1* (PubMed:34516797). Inhibits mRNA translation in a cytoplasmic polyadenylation element (CPE)-dependent manner (By similarity)","subcellular_location":"Nucleus; Nucleus, nucleolus; Chromosome, centromere; Cytoplasm; Cell projection, axon; Cell projection, dendrite; Cell projection, filopodium","url":"https://www.uniprot.org/uniprotkb/Q8NEJ9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/NGDN","classification":"Common Essential","n_dependent_lines":613,"n_total_lines":1208,"dependency_fraction":0.5074503311258278},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"AATF","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/NGDN","total_profiled":1310},"omim":[{"mim_id":"610777","title":"NEUROGUIDIN; NGDN","url":"https://www.omim.org/entry/610777"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli","reliability":"Approved"},{"location":"Mitochondria","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NGDN"},"hgnc":{"alias_symbol":["DKFZP564O092","LCP5","lpd-2","NGD","CANu1"],"prev_symbol":["C14orf120"]},"alphafold":{"accession":"Q8NEJ9","domains":[{"cath_id":"-","chopping":"226-264","consensus_level":"medium","plddt":84.0551,"start":226,"end":264},{"cath_id":"1.20.58","chopping":"16-120","consensus_level":"medium","plddt":90.6828,"start":16,"end":120},{"cath_id":"1.20.5","chopping":"186-218","consensus_level":"medium","plddt":85.3676,"start":186,"end":218}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NEJ9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NEJ9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NEJ9-F1-predicted_aligned_error_v6.png","plddt_mean":75.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NGDN","jax_strain_url":"https://www.jax.org/strain/search?query=NGDN"},"sequence":{"accession":"Q8NEJ9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NEJ9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NEJ9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NEJ9"}},"corpus_meta":[{"pmid":"9262371","id":"PMC_9262371","title":"II. Localization and characterization of dopamine D4 binding sites in rat and human brain by use of the novel, D4 receptor-selective ligand [3H]NGD 94-1.","date":"1997","source":"The Journal of pharmacology and experimental therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/9262371","citation_count":123,"is_preprint":false},{"pmid":"9814757","id":"PMC_9814757","title":"Synthetic lethal interactions with conditional poly(A) polymerase alleles identify LCP5, a gene involved in 18S rRNA maturation.","date":"1998","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/9814757","citation_count":44,"is_preprint":false},{"pmid":"9262370","id":"PMC_9262370","title":"I. NGD 94-1: identification of a novel, high-affinity antagonist at the human dopamine D4 receptor.","date":"1997","source":"The Journal of pharmacology and experimental therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/9262370","citation_count":43,"is_preprint":false},{"pmid":"29901258","id":"PMC_29901258","title":"Overexpression of Nmnat3 efficiently increases NAD and NGD levels and ameliorates age-associated insulin resistance.","date":"2018","source":"Aging cell","url":"https://pubmed.ncbi.nlm.nih.gov/29901258","citation_count":41,"is_preprint":false},{"pmid":"31511627","id":"PMC_31511627","title":"Metabolism and biochemical properties of nicotinamide adenine dinucleotide (NAD) analogs, nicotinamide guanine dinucleotide (NGD) and nicotinamide hypoxanthine dinucleotide (NHD).","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31511627","citation_count":31,"is_preprint":false},{"pmid":"24040053","id":"PMC_24040053","title":"The newly developed CRF1-receptor antagonists, NGD 98-2 and NGD 9002, suppress acute stress-induced stimulation of colonic motor function and visceral hypersensitivity in rats.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24040053","citation_count":28,"is_preprint":false},{"pmid":"27599843","id":"PMC_27599843","title":"Human AATF/Che-1 forms a nucleolar protein complex with NGDN and NOL10 required for 40S ribosomal subunit synthesis.","date":"2016","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/27599843","citation_count":23,"is_preprint":false},{"pmid":"30112426","id":"PMC_30112426","title":"Measuring CD38 Hydrolase and Cyclase Activities: 1,N6-Ethenonicotinamide Adenine Dinucleotide (ε-NAD) and Nicotinamide Guanine Dinucleotide (NGD) Fluorescence-based Methods.","date":"2018","source":"Bio-protocol","url":"https://pubmed.ncbi.nlm.nih.gov/30112426","citation_count":18,"is_preprint":false},{"pmid":"10395031","id":"PMC_10395031","title":"NGD 94-1 as an agonist at human recombinant dopamine D4.4 receptors expressed in HEK293 cells.","date":"1999","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/10395031","citation_count":18,"is_preprint":false},{"pmid":"21618986","id":"PMC_21618986","title":"Discovery of N-(1-ethylpropyl)-[3-methoxy-5-(2-methoxy-4-trifluoromethoxyphenyl)-6-methyl-pyrazin-2-yl]amine 59 (NGD 98-2): an orally active corticotropin releasing factor-1 (CRF-1) receptor antagonist.","date":"2011","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21618986","citation_count":10,"is_preprint":false},{"pmid":"15693171","id":"PMC_15693171","title":"Optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280.","date":"2005","source":"Bioresource technology","url":"https://pubmed.ncbi.nlm.nih.gov/15693171","citation_count":8,"is_preprint":false},{"pmid":"18547334","id":"PMC_18547334","title":"CANu1, a novel nucleolar protein, accumulated on centromere in response to DNA damage.","date":"2008","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/18547334","citation_count":7,"is_preprint":false},{"pmid":"35142296","id":"PMC_35142296","title":"Vannella mustalahtiana sp. nov. (Amoebozoa, Vannellida) and rainbow trout nodular gill disease (NGD) in Russia.","date":"2022","source":"Diseases of aquatic organisms","url":"https://pubmed.ncbi.nlm.nih.gov/35142296","citation_count":7,"is_preprint":false},{"pmid":"35650250","id":"PMC_35650250","title":"Artificial intelligence-assisted cryoEM structure of Bfr2-Lcp5 complex observed in the yeast small subunit processome.","date":"2022","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/35650250","citation_count":4,"is_preprint":false},{"pmid":"21266106","id":"PMC_21266106","title":"Depletion of Neuroguidin/CANu1 sensitizes human osteosarcoma U2OS cells to doxorubicin.","date":"2011","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/21266106","citation_count":2,"is_preprint":false},{"pmid":"40207436","id":"PMC_40207436","title":"Ptolemeba bulliensis Watson et al. 2014 (Amoebozoa, Tubulinea) From Freshwater NGD-Affected Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792) Gills Tolerates Brackish Water Conditions.","date":"2025","source":"Journal of fish diseases","url":"https://pubmed.ncbi.nlm.nih.gov/40207436","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9891,"output_tokens":1639,"usd":0.027129,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8410,"output_tokens":2159,"usd":0.048012,"stage2_stop_reason":"end_turn"},"total_usd":0.075141,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"Yeast LCP5 (ortholog of NGDN) is required for early pre-rRNA cleavage steps (A0 to A2) that lead to 18S rRNA maturation; depletion of Lcp5p impairs pre-rRNA processing and reduces polysome levels. Indirect immunofluorescence showed predominant nucleolar localization, and anti-Lcp5p antibodies immunoprecipitated the U3 snoRNA (snR17), indicating direct involvement in the pre-rRNA processing machinery.\",\n      \"method\": \"Temperature-sensitive mutants and in vivo depletion, Northern blot for pre-rRNA intermediates, polysome analysis, indirect immunofluorescence, co-immunoprecipitation of U3 snoRNA\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetic depletion, Northern blot, immunofluorescence, RNA co-IP) in a focused mechanistic study; foundational paper for Lcp5/NGDN function\",\n      \"pmids\": [\"9814757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Human NGDN forms a salt-stable trimeric complex (ANN complex) with AATF/Che-1 and NOL10; all three subunits localize to nucleoli and exhibit mutual dependence for protein stability. The UTP3/SAS10 domain of NGDN is required for ANN complex formation. Depletion of NGDN (or either partner) impairs 18S rRNA maturation and blocks the same nucleolar cleavage steps in the 5'ETS and ITS1 regions of the pre-rRNA, establishing that NGDN functions in 40S ribosomal subunit biogenesis.\",\n      \"method\": \"Immunoprecipitation (complex identification), domain-mapping co-IP, siRNA depletion with Northern blot analysis of pre-rRNA processing intermediates, immunofluorescence for nucleolar localization\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with domain mapping, multiple depletions with defined rRNA processing readouts, localization confirmed, all in one focused mechanistic study\",\n      \"pmids\": [\"27599843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Human CANu1/NGDN (alias of NGDN) localizes to nucleoli via its C-terminal domain; siRNA silencing causes ribosomal stress, G1 cell-cycle arrest, p53 induction, and translocation of nucleolar marker B23. Upon UV damage, CANu1 translocates from nucleoli to nuclear foci with increased mobility (FRAP).\",\n      \"method\": \"GFP-fusion live-cell imaging, C-terminal deletion constructs for localization mapping, siRNA knockdown with flow cytometry (cell-cycle), Western blot (p53, B23), FRAP after UV damage\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional deletion mapping plus KD phenotype (G1 arrest, p53 induction), single lab with multiple orthogonal methods\",\n      \"pmids\": [\"18547334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Knockdown of Neuroguidin/CANu1 (NGDN) in human osteosarcoma U2OS cells does not affect viability alone but sensitizes cells to doxorubicin-induced apoptosis; depletion induces p21 expression, PARP cleavage, and increased caspase-3/7 activity. NGDN translocates from nucleoli to nuclear foci in response to doxorubicin.\",\n      \"method\": \"shRNA knockdown, cell viability assay, annexin V apoptosis assay, Western blot (p21, cleaved PARP), caspase-3/7 activity assay, GFP relocalization\",\n      \"journal\": \"BMB reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KD with defined apoptotic phenotype and multiple readouts, but single lab, no pathway rescue or epistasis\",\n      \"pmids\": [\"21266106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CryoEM structure of the yeast Bfr2-Lcp5 (NGDN ortholog) complex within the 90S small subunit processome was determined at 3.99–7.24 Å resolution using AlphaFold-assisted modeling; the Bfr2-Lcp5 interaction architecture mimics that of exosome factors Rrp6-Rrp47, and the complex facilitates incorporation of the 5' domain of 18S rRNA into 90S. Protein-protein interaction mapping and circular dichroism of recombinant proteins validated the structural model.\",\n      \"method\": \"CryoEM structure determination with AlphaFold assistance, recombinant protein circular dichroism, protein-protein interaction assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure with biochemical validation (CD, protein interaction), but single lab and AlphaFold-assisted model in a relatively low-resolution map\",\n      \"pmids\": [\"35650250\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NGDN (human) is a nucleolar protein whose UTP3/SAS10 domain mediates assembly into the trimeric ANN complex (with AATF and NOL10), which supports nucleolar cleavage steps in the 5'ETS and ITS1 of pre-rRNA required for 18S rRNA maturation and 40S ribosomal subunit biogenesis; its yeast ortholog Lcp5 performs the same function and physically associates with the U3 snoRNA, while structural work on the Bfr2-Lcp5 complex within the 90S processome reveals an Rrp6-Rrp47-like interaction architecture that facilitates 5'-domain incorporation into 90S.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NGDN is a nucleolar protein that functions in the early nucleolar processing of pre-rRNA required for 18S rRNA maturation and 40S ribosomal subunit biogenesis [#1]. Its UTP3/SAS10 domain mediates assembly into a salt-stable trimeric ANN complex with AATF/Che-1 and NOL10, in which the three subunits are mutually dependent for protein stability and jointly support nucleolar cleavage of the 5'ETS and ITS1 regions of the pre-rRNA [#1]. This role is conserved from the yeast ortholog Lcp5, which is required for the early A0–A2 cleavage steps and physically associates with the U3 snoRNA within the pre-rRNA processing machinery [#0]; structural analysis of the yeast Bfr2–Lcp5 complex within the 90S small-subunit processome shows an interaction architecture resembling the Rrp6–Rrp47 exosome pair that facilitates incorporation of the 18S 5' domain into the 90S particle [#4]. Consistent with its essential biogenesis role, NGDN depletion provokes ribosomal stress with G1 arrest and p53 induction, and the protein relocalizes from nucleoli to nuclear foci upon genotoxic stress [#2, #3].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that the NGDN ortholog acts directly in the pre-rRNA processing machinery rather than as a general translation factor, by tying it to specific early cleavage steps and the U3 snoRNP.\",\n      \"evidence\": \"Temperature-sensitive/depletion genetics, Northern blot of pre-rRNA intermediates, polysome profiling, immunofluorescence, and U3 snoRNA co-IP in yeast Lcp5\",\n      \"pmids\": [\"9814757\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the human ortholog's partners or complex\", \"Mechanism of U3 association (direct vs. via other factors) not resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified the human protein as nucleolar via a C-terminal targeting domain and linked its loss to ribosomal stress signaling, connecting NGDN to cell-cycle and p53 control.\",\n      \"evidence\": \"GFP live-cell imaging, C-terminal deletion mapping, siRNA with flow cytometry, Western blot for p53/B23, and FRAP after UV in human cells\",\n      \"pmids\": [\"18547334\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The molecular basis of stress-induced relocalization not defined\", \"Did not identify NGDN's protein partners\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed that NGDN depletion is not lethal alone but sensitizes cells to genotoxic apoptosis, refining its role as a modulator of stress-induced cell death.\",\n      \"evidence\": \"shRNA knockdown, viability and annexin V assays, Western blot (p21, cleaved PARP), caspase-3/7 activity, and GFP relocalization in U2OS cells\",\n      \"pmids\": [\"21266106\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single cell line, no rescue or epistasis\", \"Link between rRNA processing defect and apoptosis sensitization not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined NGDN's physical context in humans by identifying the trimeric ANN complex and mapping the UTP3/SAS10 domain as the assembly module required for 18S maturation.\",\n      \"evidence\": \"Reciprocal and domain-mapping co-IP, siRNA depletions with Northern blot of pre-rRNA intermediates, and immunofluorescence in human cells\",\n      \"pmids\": [\"27599843\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ANN assembly not determined\", \"Functional division of labor among the three subunits unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided a structural rationale for NGDN ortholog action within the 90S processome, showing its complex mimics an exosome-factor architecture to aid 5'-domain incorporation.\",\n      \"evidence\": \"CryoEM (3.99–7.24 Å) with AlphaFold-assisted modeling, recombinant circular dichroism, and protein-protein interaction assays of yeast Bfr2-Lcp5\",\n      \"pmids\": [\"35650250\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relatively low-resolution map with AlphaFold-assisted model\", \"Human ANN complex structure within the processome not determined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How NGDN's nucleolar pre-rRNA processing role is mechanistically coupled to the p53-dependent ribosomal stress and apoptosis phenotypes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human structure of the ANN complex on the pre-ribosome\", \"Disease association of NGDN not established in this corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"complexes\": [\"ANN complex (NGDN-AATF-NOL10)\", \"90S small subunit processome\", \"Bfr2-Lcp5 complex (yeast)\"],\n    \"partners\": [\"AATF\", \"NOL10\", \"BFR2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}