{"gene":"GNL2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2002,"finding":"Yeast Nog2 (ortholog of GNL2) is a putative GTPase required for 60S ribosomal subunit maturation and may also participate in mRNA splicing; extra copies of NOG2 suppress deficiency of cohesin Irr1p/Scc3p.","method":"Dosage suppressor screen in Saccharomyces cerevisiae; genetic epistasis","journal":"Acta biochimica Polonica","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single genetic screen, no direct biochemical characterization of Nog2 activity in this paper","pmids":["12362983"],"is_preprint":false},{"year":2011,"finding":"NGP-1 (GNL2) localizes to the nucleolus via two independent nucleolar localization signals (NoLS): an amino-terminal signal (residues 1–100) that interacts with importin-β, and a carboxyl-terminal signal (residues 661–731) that interacts with importin-α. GTP binding via G4 and G5 motifs of the G-domain is required for nucleolar localization (GTP-gating mechanism). Ongoing transcription is also required for efficient nucleolar retention.","method":"Site-specific mutagenesis, immunofluorescence, co-immunoprecipitation with importin-α and importin-β, alanine scanning mutagenesis of G-domain, heterologous protein targeting assays","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple orthogonal methods (mutagenesis, IF, Co-IP) in single lab establishing NoLS and GTP-gating mechanism","pmids":["21495629"],"is_preprint":false},{"year":2011,"finding":"Zebrafish Gnl2 (ortholog of GNL2) is required for correct timing of cell cycle exit and neural differentiation in the retina and brain. Loss of Gnl2 induces p53 stabilization and p53-mediated apoptosis, and aberrant expression of cell cycle regulators cyclinD1 and p57kip2. However, retinal differentiation defects caused by Gnl2 loss are independent of p53 activation, demonstrating a p53-independent function in neural progenitor cell cycle exit.","method":"Forward and reverse genetic screens in zebrafish; loss-of-function mutant analysis; genetic epistasis (p53-independent phenotype); immunostaining for cyclinD1 and p57kip2","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — zebrafish loss-of-function with defined cellular phenotype and genetic epistasis separating p53-dependent from p53-independent functions, single lab","pmids":["21565180"],"is_preprint":false},{"year":2015,"finding":"NGP-1 (GNL2) promotes G1-to-S phase transition by enhancing CDK inhibitor p21(Cip1/Waf1) expression through p53, and by maintaining the stoichiometry of the cyclin D1-CDK4 complex relative to p21, leading to hyperphosphorylation of Rb at Ser780 and upregulation of E2F1 target genes. Ribosomal protein RPL23A interacts with NGP-1 and abolishes NGP-1-induced p53 activity by enhancing Mdm2-mediated p53 polyubiquitination.","method":"Co-immunoprecipitation (NGP-1/RPL23A interaction), ectopic expression and knockdown with cell cycle analysis, immunoblotting for p-Rb(Ser780), p21, cyclin D1-CDK4, and E2F1 target genes; ubiquitination assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple orthogonal methods (Co-IP, cell cycle analysis, ubiquitination assay, KD/OE), single lab","pmids":["26203195"],"is_preprint":false},{"year":2021,"finding":"GNL2 influences 60S ribosomal subunit maturation and global protein synthesis in ovarian cancer cells and fallopian tube secretory epithelial cells (FTSECs). GNL2 silencing diminished xenograft tumor formation, while GNL2 overexpression stimulated proliferation and colony formation in FTSECs.","method":"siRNA knockdown, xenograft tumor formation assay, overexpression with proliferation and colony formation assays, protein synthesis assessment","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — functional loss- and gain-of-function experiments with defined cellular readouts including in vivo xenograft, single lab","pmids":["34965383"],"is_preprint":false},{"year":2023,"finding":"The GTPase activity of yeast Nog2 (ortholog of GNL2) is regulated by rRNA methylation status at G2922 of the A-loop. Cryo-EM structures reveal that unmethylated G2922 (due to catalytically deficient Spb1 methyltransferase) leads to premature activation of Nog2 GTPase activity. A Nog2-GDP-AlF4- transition state structure implicates the direct involvement of unmodified G2922 in Nog2 GTPase activation. Premature GTP hydrolysis prevents efficient binding of Nog2 to early nucleoplasmic 60S intermediates, establishing that G2922 methylation levels constitute a kinetic checkpoint regulating Nog2 recruitment at the nucleolar/nucleoplasmic phase boundary.","method":"Cryo-EM structural determination (including transition state analog GDP-AlF4- structure), genetic suppressors, in vivo imaging, catalytically deficient methyltransferase mutant (spb1D52A)","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures including transition state, genetic suppressors, in vivo imaging, multiple orthogonal methods in single rigorous study","pmids":["36864048"],"is_preprint":false},{"year":2024,"finding":"GNL2 affects overall protein synthesis in glioma cells, specifically influencing ribosomal protein L11 levels. GNL2 knockdown inhibited glioma cell growth, migration, and invasion.","method":"siRNA knockdown with cell proliferation, migration, and invasion assays; protein synthesis analysis (ribosomal protein L11 levels)","journal":"Oncology letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic detail in abstract, single method per readout","pmids":["38779136"],"is_preprint":false},{"year":2025,"finding":"GNL2 physically interacts with Ki-67 (MKI67) at the nucleolar periphery and together these proteins can recruit MDN1 to the nucleolar periphery. Depletion of GNL2 results in characteristic changes in nucleolar protein and chromatin localization. GNL2 participates in the export of pre-60S particles from the nucleolus, and depleting GNL2 decreases levels of RNAs involved in ribosome biogenesis.","method":"ChIP-seq, RNA-seq, confocal microscopy, biochemical co-immunoprecipitation (protein-protein interaction), knockdown with nucleolar phenotype readouts in HEK293T cells","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple orthogonal methods (ChIP-seq, RNA-seq, confocal, Co-IP, KD phenotype), preprint not yet peer-reviewed, single lab","pmids":["bio_10.1101_2025.02.13.638155"],"is_preprint":true}],"current_model":"GNL2 (NGP-1/Nog2) is a nucleolar GTPase that localizes to the nucleolus via two independent importin-dependent nucleolar localization signals in a GTP-binding- and transcription-dependent manner; its core function is facilitating 60S ribosomal subunit maturation and export — a process regulated by rRNA A-loop methylation status that controls the timing of Nog2 GTPase activation — and it also promotes cell cycle G1-to-S progression by activating the p53/p21/cyclin D1-CDK4/Rb-E2F1 axis, with ribosomal protein RPL23A acting as a negative regulator by enhancing Mdm2-mediated p53 ubiquitination downstream of NGP-1."},"narrative":{"mechanistic_narrative":"GNL2 (NGP-1/Nog2) is a nucleolar GTPase that functions in 60S ribosomal subunit maturation and export, and it also couples ribosome biogenesis to cell cycle progression [PMID:21495629, PMID:34965383, PMID:36864048]. It is targeted to the nucleolus through two independent importin-dependent nucleolar localization signals — an N-terminal signal binding importin-β and a C-terminal signal binding importin-α — with efficient nucleolar retention requiring GTP binding at the G-domain (a GTP-gating mechanism) and ongoing transcription [PMID:21495629]. Within ribosome assembly, GNL2 binds nucleoplasmic pre-60S intermediates and participates in their export from the nucleolus; its recruitment timing is set by a kinetic checkpoint in which rRNA A-loop methylation at G2922 controls premature versus appropriately timed activation of its GTPase activity, ensuring stable engagement at the nucleolar/nucleoplasmic phase boundary [PMID:36864048, PMID:bio_10.1101_2025.02.13.638155]. GNL2 promotes the G1-to-S transition by enhancing p53-dependent p21 expression and maintaining the cyclin D1-CDK4/p21 stoichiometry that drives Rb hyperphosphorylation and E2F1 target activation, with ribosomal protein RPL23A acting as a negative regulator by enhancing Mdm2-mediated p53 ubiquitination downstream of GNL2 [PMID:26203195]. Consistent with these roles, GNL2 supports global protein synthesis and proliferative capacity in ovarian and glioma cancer cell models [PMID:34965383, PMID:38779136].","teleology":[{"year":2002,"claim":"Established the founding hypothesis that the GNL2 ortholog is a GTPase acting in 60S ribosomal subunit maturation, placing the gene in ribosome biogenesis.","evidence":"Dosage suppressor screen and genetic epistasis in S. cerevisiae","pmids":["12362983"],"confidence":"Low","gaps":["No direct biochemical demonstration of GTPase activity","Proposed mRNA splicing role not validated","Mechanism of cohesin suppression unexplained"]},{"year":2011,"claim":"Defined how GNL2 reaches its site of action, identifying dual importin-dependent nucleolar localization signals and a GTP-gating requirement, explaining the spatial control of the protein.","evidence":"Site-directed mutagenesis, immunofluorescence, and Co-IP with importin-α/β plus G-domain alanine scanning in human cells","pmids":["21495629"],"confidence":"Medium","gaps":["Does not address what GNL2 does once in the nucleolus","GTPase catalytic cycle not measured biochemically","No structural model of the targeting determinants"]},{"year":2011,"claim":"Connected GNL2 to developmental cell cycle control, showing it is required for proper timing of cell cycle exit and separating its p53-dependent apoptotic role from a p53-independent differentiation role.","evidence":"Loss-of-function mutant analysis and genetic epistasis in zebrafish retina/brain","pmids":["21565180"],"confidence":"Medium","gaps":["Molecular basis of the p53-independent differentiation function unidentified","Link to ribosome biogenesis vs. direct cell cycle role not resolved","Direct targets in neural progenitors unknown"]},{"year":2015,"claim":"Mapped the cell cycle mechanism, showing GNL2 drives G1-to-S transition through a p53/p21/cyclin D1-CDK4/Rb/E2F1 axis and identifying RPL23A as a negative regulator via Mdm2-mediated p53 ubiquitination.","evidence":"Co-IP, knockdown/overexpression with cell cycle analysis, immunoblotting, and ubiquitination assay in human cells","pmids":["26203195"],"confidence":"Medium","gaps":["Whether p53 activation is a consequence of impaired ribosome biogenesis (nucleolar stress) not distinguished","Direct vs. indirect effect of GNL2 on p53 unresolved","Single-lab findings"]},{"year":2021,"claim":"Demonstrated that GNL2 controls 60S maturation and global protein synthesis in human cells and supports tumorigenic proliferation, linking its biogenesis role to disease-relevant phenotypes.","evidence":"siRNA knockdown, overexpression, proliferation/colony assays, xenograft, and protein synthesis measurement in ovarian cancer cells and FTSECs","pmids":["34965383"],"confidence":"Medium","gaps":["Specific maturation step catalyzed not defined","Mechanistic basis of tumor dependence unclear","No structural insight into substrate engagement"]},{"year":2023,"claim":"Resolved the activation logic of the Nog2 GTPase, showing rRNA A-loop G2922 methylation status sets a kinetic checkpoint that times GTPase activation and stable binding to pre-60S intermediates.","evidence":"Cryo-EM including a GDP-AlF4- transition-state structure, genetic suppressors, and in vivo imaging with a methyltransferase mutant in yeast","pmids":["36864048"],"confidence":"High","gaps":["Conservation of the G2922 checkpoint in human GNL2 not directly tested","Identity of the human GTPase-activating partner unconfirmed","Coupling to export machinery not structurally defined"]},{"year":2024,"claim":"Extended the protein-synthesis dependency to glioma, linking GNL2 to ribosomal protein L11 levels and malignant cell behavior.","evidence":"siRNA knockdown with proliferation, migration, invasion, and protein synthesis assays in glioma cells","pmids":["38779136"],"confidence":"Low","gaps":["Limited mechanistic detail","Direct interaction with RPL11 not shown","Single method per readout"]},{"year":2025,"claim":"Identified physical partners and chromatin/RNA-level consequences of GNL2, placing it at the nucleolar periphery with Ki-67 and MDN1 during pre-60S export.","evidence":"Co-IP, ChIP-seq, RNA-seq, and confocal microscopy with knockdown phenotypes in HEK293T cells (preprint)","pmids":["bio_10.1101_2025.02.13.638155"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Functional significance of the Ki-67/MDN1 recruitment not established","Direct vs. indirect chromatin effects unresolved"]},{"year":null,"claim":"Whether the yeast G2922 methylation checkpoint governing GTPase timing operates in human GNL2, and how its 60S maturation role mechanistically connects to the p53/cell cycle axis, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human structural data on GNL2-pre-60S engagement","Cause-effect relationship between biogenesis defect and p53 activation undefined","Human GTPase-activating cofactor unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,5]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[1,7]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[4,5,7]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2,3]}],"complexes":["pre-60S ribosomal particle"],"partners":["KPNB1","KPNA2","RPL23A","MKI67","MDN1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q13823","full_name":"Nucleolar GTP-binding protein 2","aliases":["Autoantigen NGP-1"],"length_aa":731,"mass_kda":83.7,"function":"GTPase that associates with pre-60S ribosomal subunits in the nucleolus and is required for their nuclear export and maturation (PubMed:32669547). May promote cell proliferation possibly by increasing p53/TP53 protein levels, and consequently those of its downstream product CDKN1A/p21, and decreasing RPL23A protein levels (PubMed:26203195)","subcellular_location":"Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/Q13823/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GNL2","classification":"Common Essential","n_dependent_lines":1201,"n_total_lines":1208,"dependency_fraction":0.9942052980132451},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000134697","cell_line_id":"CID001070","localizations":[{"compartment":"nucleolus_gc","grade":3}],"interactors":[{"gene":"DRG1","stoichiometry":0.2},{"gene":"G3BP2","stoichiometry":0.2},{"gene":"IPO5","stoichiometry":0.2},{"gene":"METAP2","stoichiometry":0.2},{"gene":"NPM1","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"RACK1","stoichiometry":0.2},{"gene":"RBM42","stoichiometry":0.2},{"gene":"RBM8A","stoichiometry":0.2},{"gene":"RPS16","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001070","total_profiled":1310},"omim":[{"mim_id":"612845","title":"SENTRIN-SPECIFIC PROTEASE FAMILY, MEMBER 5; SENP5","url":"https://www.omim.org/entry/612845"},{"mim_id":"612844","title":"SENTRIN-SPECIFIC PROTEASE FAMILY, MEMBER 3; SENP3","url":"https://www.omim.org/entry/612844"},{"mim_id":"609365","title":"GUANINE NUCLEOTIDE-BINDING PROTEIN-LIKE 2; GNL2","url":"https://www.omim.org/entry/609365"},{"mim_id":"108745","title":"ATPase, H+ TRANSPORTING, LYSOSOMAL, 16-KD, V0 SUBUNIT C; ATP6V0C","url":"https://www.omim.org/entry/108745"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoli","reliability":"Supported"},{"location":"Nucleoli rim","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GNL2"},"hgnc":{"alias_symbol":["Ngp-1","HUMAUANTIG","Nog2","Nug2"],"prev_symbol":[]},"alphafold":{"accession":"Q13823","domains":[{"cath_id":"3.40.50.300","chopping":"203-360","consensus_level":"high","plddt":93.7087,"start":203,"end":360},{"cath_id":"1.10.1580.10","chopping":"372-452","consensus_level":"high","plddt":93.2946,"start":372,"end":452}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13823","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13823-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13823-F1-predicted_aligned_error_v6.png","plddt_mean":73.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GNL2","jax_strain_url":"https://www.jax.org/strain/search?query=GNL2"},"sequence":{"accession":"Q13823","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13823.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13823/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13823"}},"corpus_meta":[{"pmid":"12441390","id":"PMC_12441390","title":"Crystal structures and increased stabilization of the protein G variants with switched folding pathways NuG1 and NuG2.","date":"2002","source":"Protein science : a publication of the Protein Society","url":"https://pubmed.ncbi.nlm.nih.gov/12441390","citation_count":49,"is_preprint":false},{"pmid":"28026101","id":"PMC_28026101","title":"Single-Molecule Force Spectroscopy Trajectories of a Single Protein and Its Polyproteins Are Equivalent: A Direct Experimental Validation Based on A Small Protein NuG2.","date":"2016","source":"Angewandte Chemie (International ed. in English)","url":"https://pubmed.ncbi.nlm.nih.gov/28026101","citation_count":34,"is_preprint":false},{"pmid":"21565180","id":"PMC_21565180","title":"The nucleolar GTP-binding proteins Gnl2 and nucleostemin are required for retinal neurogenesis in developing zebrafish.","date":"2011","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/21565180","citation_count":31,"is_preprint":false},{"pmid":"27119632","id":"PMC_27119632","title":"Markov State Models and tICA Reveal a Nonnative Folding Nucleus in Simulations of NuG2.","date":"2016","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/27119632","citation_count":25,"is_preprint":false},{"pmid":"26203195","id":"PMC_26203195","title":"Nucleolar GTP-binding Protein-1 (NGP-1) Promotes G1 to S Phase Transition by Activating Cyclin-dependent Kinase Inhibitor p21 Cip1/Waf1.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26203195","citation_count":22,"is_preprint":false},{"pmid":"36864048","id":"PMC_36864048","title":"rRNA methylation by Spb1 regulates the GTPase activity of Nog2 during 60S ribosomal subunit assembly.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36864048","citation_count":12,"is_preprint":false},{"pmid":"34965383","id":"PMC_34965383","title":"Functional analysis of the 1p34.3 risk locus implicates GNL2 in high-grade serous ovarian cancer.","date":"2021","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34965383","citation_count":11,"is_preprint":false},{"pmid":"31370539","id":"PMC_31370539","title":"Folding pathways of NuG2-a designed mutant of protein G-using relaxation mode analysis.","date":"2019","source":"The Journal of chemical physics","url":"https://pubmed.ncbi.nlm.nih.gov/31370539","citation_count":11,"is_preprint":false},{"pmid":"36941720","id":"PMC_36941720","title":"DNER and GNL2 are differentially m6A methylated in periodontitis in comparison with periodontal health revealed by m6A microarray of human gingival tissue and transcriptomic analysis.","date":"2023","source":"Journal of periodontal research","url":"https://pubmed.ncbi.nlm.nih.gov/36941720","citation_count":7,"is_preprint":false},{"pmid":"21495629","id":"PMC_21495629","title":"Signals and pathways regulating nucleolar retention of novel putative nucleolar GTPase NGP-1(GNL-2).","date":"2011","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21495629","citation_count":7,"is_preprint":false},{"pmid":"12362983","id":"PMC_12362983","title":"Additional copies of the NOG2 and IST2 genes suppress the deficiency of cohesin Irr1p/Scc3p in Saccharomyces cerevisiae.","date":"2002","source":"Acta biochimica Polonica","url":"https://pubmed.ncbi.nlm.nih.gov/12362983","citation_count":3,"is_preprint":false},{"pmid":"38779136","id":"PMC_38779136","title":"Oncogenic role of RNA-binding protein GNL2 in glioma: Promotion of tumor development through enhancing protein synthesis.","date":"2024","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/38779136","citation_count":1,"is_preprint":false},{"pmid":"37570604","id":"PMC_37570604","title":"Assessment of Purity, Stability, and Pharmacokinetics of NGP-1, a Novel Prodrug of GS441254 with Potential Anti-SARS-CoV-2 Activity, Using Liquid Chromatography.","date":"2023","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/37570604","citation_count":1,"is_preprint":false},{"pmid":"42135716","id":"PMC_42135716","title":"Multi-omics integration identifies ribosome biogenesis-active macrophage subpopulation and its key gene GNL2 in driving liver hepatocellular carcinoma progression and mechanisms.","date":"2026","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/42135716","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.13.638155","title":"The roles of MKI67, GNL2, and MDN1 in Ribosome biogenesis and Transcriptome regulation in the Neuronal Lineage cell line HEK293T","date":"2025-02-16","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.13.638155","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.03.657657","title":"Evolutionary origin and functional diversification of plant GBF1-type ARF guanine-nucleotide exchange factors","date":"2025-06-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.03.657657","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10055,"output_tokens":2809,"usd":0.03615,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9493,"output_tokens":2985,"usd":0.061045,"stage2_stop_reason":"end_turn"},"total_usd":0.097195,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at these papers, I need to identify which ones are about the human/mammalian GNL2 gene (also known as NGP-1, Nog2, Nug2) and contain mechanistic findings.\n\n**Classification:**\n- Papers 1, 2, 4, 8: About \"NuG2\" - a designed protein G variant used in protein folding studies. This is NOT GNL2/NGP-1/Nog2. It's a synthetic protein engineering construct. EXCLUDE.\n- Paper 3: About zebrafish Gnl2 (ortholog of human GNL2). INCLUDE.\n- Paper 5: About NGP-1 (GNL2 alias). INCLUDE.\n- Paper 6: About yeast Nog2 (ortholog of GNL2). INCLUDE.\n- Paper 7: About human GNL2 in ovarian cancer. INCLUDE.\n- Paper 9: m6A methylation correlation study - no mechanistic experiment. EXCLUDE.\n- Paper 10: About NGP-1/GNL-2 (GNL2 alias). INCLUDE.\n- Paper 11: About yeast NOG2 (ortholog). INCLUDE.\n- Paper 12: About GNL2 in glioma. INCLUDE.\n- Paper 13: NGP-1 is a prodrug name, not the GNL2 gene. EXCLUDE.\n- Paper 14: GNL2 in liver cancer - mostly bioinformatics with some functional validation. Partial INCLUDE.\n- Paper 15: About GNL2 in HEK293T. INCLUDE (preprint).\n- Paper 16: AtGNL2 is an Arabidopsis ARF-GEF - symbol collision with plant gene, fundamentally different protein. EXCLUDE.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"Yeast Nog2 (ortholog of GNL2) is a putative GTPase required for 60S ribosomal subunit maturation and may also participate in mRNA splicing; extra copies of NOG2 suppress deficiency of cohesin Irr1p/Scc3p.\",\n      \"method\": \"Dosage suppressor screen in Saccharomyces cerevisiae; genetic epistasis\",\n      \"journal\": \"Acta biochimica Polonica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single genetic screen, no direct biochemical characterization of Nog2 activity in this paper\",\n      \"pmids\": [\"12362983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NGP-1 (GNL2) localizes to the nucleolus via two independent nucleolar localization signals (NoLS): an amino-terminal signal (residues 1–100) that interacts with importin-β, and a carboxyl-terminal signal (residues 661–731) that interacts with importin-α. GTP binding via G4 and G5 motifs of the G-domain is required for nucleolar localization (GTP-gating mechanism). Ongoing transcription is also required for efficient nucleolar retention.\",\n      \"method\": \"Site-specific mutagenesis, immunofluorescence, co-immunoprecipitation with importin-α and importin-β, alanine scanning mutagenesis of G-domain, heterologous protein targeting assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple orthogonal methods (mutagenesis, IF, Co-IP) in single lab establishing NoLS and GTP-gating mechanism\",\n      \"pmids\": [\"21495629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Zebrafish Gnl2 (ortholog of GNL2) is required for correct timing of cell cycle exit and neural differentiation in the retina and brain. Loss of Gnl2 induces p53 stabilization and p53-mediated apoptosis, and aberrant expression of cell cycle regulators cyclinD1 and p57kip2. However, retinal differentiation defects caused by Gnl2 loss are independent of p53 activation, demonstrating a p53-independent function in neural progenitor cell cycle exit.\",\n      \"method\": \"Forward and reverse genetic screens in zebrafish; loss-of-function mutant analysis; genetic epistasis (p53-independent phenotype); immunostaining for cyclinD1 and p57kip2\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — zebrafish loss-of-function with defined cellular phenotype and genetic epistasis separating p53-dependent from p53-independent functions, single lab\",\n      \"pmids\": [\"21565180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"NGP-1 (GNL2) promotes G1-to-S phase transition by enhancing CDK inhibitor p21(Cip1/Waf1) expression through p53, and by maintaining the stoichiometry of the cyclin D1-CDK4 complex relative to p21, leading to hyperphosphorylation of Rb at Ser780 and upregulation of E2F1 target genes. Ribosomal protein RPL23A interacts with NGP-1 and abolishes NGP-1-induced p53 activity by enhancing Mdm2-mediated p53 polyubiquitination.\",\n      \"method\": \"Co-immunoprecipitation (NGP-1/RPL23A interaction), ectopic expression and knockdown with cell cycle analysis, immunoblotting for p-Rb(Ser780), p21, cyclin D1-CDK4, and E2F1 target genes; ubiquitination assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple orthogonal methods (Co-IP, cell cycle analysis, ubiquitination assay, KD/OE), single lab\",\n      \"pmids\": [\"26203195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GNL2 influences 60S ribosomal subunit maturation and global protein synthesis in ovarian cancer cells and fallopian tube secretory epithelial cells (FTSECs). GNL2 silencing diminished xenograft tumor formation, while GNL2 overexpression stimulated proliferation and colony formation in FTSECs.\",\n      \"method\": \"siRNA knockdown, xenograft tumor formation assay, overexpression with proliferation and colony formation assays, protein synthesis assessment\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — functional loss- and gain-of-function experiments with defined cellular readouts including in vivo xenograft, single lab\",\n      \"pmids\": [\"34965383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The GTPase activity of yeast Nog2 (ortholog of GNL2) is regulated by rRNA methylation status at G2922 of the A-loop. Cryo-EM structures reveal that unmethylated G2922 (due to catalytically deficient Spb1 methyltransferase) leads to premature activation of Nog2 GTPase activity. A Nog2-GDP-AlF4- transition state structure implicates the direct involvement of unmodified G2922 in Nog2 GTPase activation. Premature GTP hydrolysis prevents efficient binding of Nog2 to early nucleoplasmic 60S intermediates, establishing that G2922 methylation levels constitute a kinetic checkpoint regulating Nog2 recruitment at the nucleolar/nucleoplasmic phase boundary.\",\n      \"method\": \"Cryo-EM structural determination (including transition state analog GDP-AlF4- structure), genetic suppressors, in vivo imaging, catalytically deficient methyltransferase mutant (spb1D52A)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures including transition state, genetic suppressors, in vivo imaging, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"36864048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GNL2 affects overall protein synthesis in glioma cells, specifically influencing ribosomal protein L11 levels. GNL2 knockdown inhibited glioma cell growth, migration, and invasion.\",\n      \"method\": \"siRNA knockdown with cell proliferation, migration, and invasion assays; protein synthesis analysis (ribosomal protein L11 levels)\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic detail in abstract, single method per readout\",\n      \"pmids\": [\"38779136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GNL2 physically interacts with Ki-67 (MKI67) at the nucleolar periphery and together these proteins can recruit MDN1 to the nucleolar periphery. Depletion of GNL2 results in characteristic changes in nucleolar protein and chromatin localization. GNL2 participates in the export of pre-60S particles from the nucleolus, and depleting GNL2 decreases levels of RNAs involved in ribosome biogenesis.\",\n      \"method\": \"ChIP-seq, RNA-seq, confocal microscopy, biochemical co-immunoprecipitation (protein-protein interaction), knockdown with nucleolar phenotype readouts in HEK293T cells\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple orthogonal methods (ChIP-seq, RNA-seq, confocal, Co-IP, KD phenotype), preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.02.13.638155\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"GNL2 (NGP-1/Nog2) is a nucleolar GTPase that localizes to the nucleolus via two independent importin-dependent nucleolar localization signals in a GTP-binding- and transcription-dependent manner; its core function is facilitating 60S ribosomal subunit maturation and export — a process regulated by rRNA A-loop methylation status that controls the timing of Nog2 GTPase activation — and it also promotes cell cycle G1-to-S progression by activating the p53/p21/cyclin D1-CDK4/Rb-E2F1 axis, with ribosomal protein RPL23A acting as a negative regulator by enhancing Mdm2-mediated p53 ubiquitination downstream of NGP-1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GNL2 (NGP-1/Nog2) is a nucleolar GTPase that functions in 60S ribosomal subunit maturation and export, and it also couples ribosome biogenesis to cell cycle progression [#1, #4, #5]. It is targeted to the nucleolus through two independent importin-dependent nucleolar localization signals — an N-terminal signal binding importin-\\u03b2 and a C-terminal signal binding importin-\\u03b1 — with efficient nucleolar retention requiring GTP binding at the G-domain (a GTP-gating mechanism) and ongoing transcription [#1]. Within ribosome assembly, GNL2 binds nucleoplasmic pre-60S intermediates and participates in their export from the nucleolus; its recruitment timing is set by a kinetic checkpoint in which rRNA A-loop methylation at G2922 controls premature versus appropriately timed activation of its GTPase activity, ensuring stable engagement at the nucleolar/nucleoplasmic phase boundary [#5, #7]. GNL2 promotes the G1-to-S transition by enhancing p53-dependent p21 expression and maintaining the cyclin D1-CDK4/p21 stoichiometry that drives Rb hyperphosphorylation and E2F1 target activation, with ribosomal protein RPL23A acting as a negative regulator by enhancing Mdm2-mediated p53 ubiquitination downstream of GNL2 [#3]. Consistent with these roles, GNL2 supports global protein synthesis and proliferative capacity in ovarian and glioma cancer cell models [#4, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established the founding hypothesis that the GNL2 ortholog is a GTPase acting in 60S ribosomal subunit maturation, placing the gene in ribosome biogenesis.\",\n      \"evidence\": \"Dosage suppressor screen and genetic epistasis in S. cerevisiae\",\n      \"pmids\": [\"12362983\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct biochemical demonstration of GTPase activity\", \"Proposed mRNA splicing role not validated\", \"Mechanism of cohesin suppression unexplained\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined how GNL2 reaches its site of action, identifying dual importin-dependent nucleolar localization signals and a GTP-gating requirement, explaining the spatial control of the protein.\",\n      \"evidence\": \"Site-directed mutagenesis, immunofluorescence, and Co-IP with importin-\\u03b1/\\u03b2 plus G-domain alanine scanning in human cells\",\n      \"pmids\": [\"21495629\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address what GNL2 does once in the nucleolus\", \"GTPase catalytic cycle not measured biochemically\", \"No structural model of the targeting determinants\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected GNL2 to developmental cell cycle control, showing it is required for proper timing of cell cycle exit and separating its p53-dependent apoptotic role from a p53-independent differentiation role.\",\n      \"evidence\": \"Loss-of-function mutant analysis and genetic epistasis in zebrafish retina/brain\",\n      \"pmids\": [\"21565180\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the p53-independent differentiation function unidentified\", \"Link to ribosome biogenesis vs. direct cell cycle role not resolved\", \"Direct targets in neural progenitors unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mapped the cell cycle mechanism, showing GNL2 drives G1-to-S transition through a p53/p21/cyclin D1-CDK4/Rb/E2F1 axis and identifying RPL23A as a negative regulator via Mdm2-mediated p53 ubiquitination.\",\n      \"evidence\": \"Co-IP, knockdown/overexpression with cell cycle analysis, immunoblotting, and ubiquitination assay in human cells\",\n      \"pmids\": [\"26203195\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether p53 activation is a consequence of impaired ribosome biogenesis (nucleolar stress) not distinguished\", \"Direct vs. indirect effect of GNL2 on p53 unresolved\", \"Single-lab findings\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated that GNL2 controls 60S maturation and global protein synthesis in human cells and supports tumorigenic proliferation, linking its biogenesis role to disease-relevant phenotypes.\",\n      \"evidence\": \"siRNA knockdown, overexpression, proliferation/colony assays, xenograft, and protein synthesis measurement in ovarian cancer cells and FTSECs\",\n      \"pmids\": [\"34965383\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific maturation step catalyzed not defined\", \"Mechanistic basis of tumor dependence unclear\", \"No structural insight into substrate engagement\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the activation logic of the Nog2 GTPase, showing rRNA A-loop G2922 methylation status sets a kinetic checkpoint that times GTPase activation and stable binding to pre-60S intermediates.\",\n      \"evidence\": \"Cryo-EM including a GDP-AlF4- transition-state structure, genetic suppressors, and in vivo imaging with a methyltransferase mutant in yeast\",\n      \"pmids\": [\"36864048\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conservation of the G2922 checkpoint in human GNL2 not directly tested\", \"Identity of the human GTPase-activating partner unconfirmed\", \"Coupling to export machinery not structurally defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the protein-synthesis dependency to glioma, linking GNL2 to ribosomal protein L11 levels and malignant cell behavior.\",\n      \"evidence\": \"siRNA knockdown with proliferation, migration, invasion, and protein synthesis assays in glioma cells\",\n      \"pmids\": [\"38779136\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Limited mechanistic detail\", \"Direct interaction with RPL11 not shown\", \"Single method per readout\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified physical partners and chromatin/RNA-level consequences of GNL2, placing it at the nucleolar periphery with Ki-67 and MDN1 during pre-60S export.\",\n      \"evidence\": \"Co-IP, ChIP-seq, RNA-seq, and confocal microscopy with knockdown phenotypes in HEK293T cells (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.02.13.638155\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Functional significance of the Ki-67/MDN1 recruitment not established\", \"Direct vs. indirect chromatin effects unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether the yeast G2922 methylation checkpoint governing GTPase timing operates in human GNL2, and how its 60S maturation role mechanistically connects to the p53/cell cycle axis, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human structural data on GNL2-pre-60S engagement\", \"Cause-effect relationship between biogenesis defect and p53 activation undefined\", \"Human GTPase-activating cofactor unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [1, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [4, 5, 7]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"complexes\": [\"pre-60S ribosomal particle\"],\n    \"partners\": [\"KPNB1\", \"KPNA2\", \"RPL23A\", \"MKI67\", \"MDN1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}