{"gene":"NUFIP2","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2018,"finding":"NUFIP2 was identified as a direct cofactor of Roquin-1/2 RNA-binding proteins. NUFIP2 binds directly and with high affinity to Roquin, which in turn stabilizes NUFIP2 in cells. NUFIP2 is required for Roquin-induced mRNA decay of target transcripts such as ICOS and Ox40. NUFIP2 and Roquin cooperatively bind non-canonical stem-loop structures in the 3'-UTRs of target mRNAs (including unconventional tandem loops in the ICOS and Ox40 3'-UTRs), establishing NUFIP2 as a cofactor that contributes to mRNA target recognition by Roquin.","method":"RNA interference screen (~1500 genes), co-immunoprecipitation, direct binding assays, EMSA/binding affinity measurements, reporter assays for mRNA decay, endogenous Roquin knockdown with ICOS/Ox40 3'-UTR reporters","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — reciprocal binding assays, functional mRNA decay assays, RNAi screen validation, multiple orthogonal methods in a single rigorous study","pmids":["29352114"],"is_preprint":false},{"year":2012,"finding":"NUFIP2 was identified as a bona fide mRNA-binding protein (RBP) through UV crosslinking and oligo(dT) capture (interactome capture) of proliferating HeLa cells, indicating NUFIP2 directly contacts mRNA in living cells.","method":"UV crosslinking, oligo(dT) purification, quantitative mass spectrometry (interactome capture)","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 2 — systematic biochemical capture with statistical validation, but functional consequence not characterized in this study","pmids":["22658674"],"is_preprint":false},{"year":2012,"finding":"NUFIP2 was independently confirmed as an mRNA-binding protein via photoreactive nucleotide-enhanced UV crosslinking and oligo(dT) purification in HEK293 cells, further establishing its direct RNA-binding activity.","method":"PAR-CLIP (photoreactive nucleotide-enhanced UV crosslinking), oligo(dT) purification, quantitative proteomics","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 — orthogonal crosslinking method independently replicating RBP identity, single study without functional follow-up","pmids":["22681889"],"is_preprint":false},{"year":2017,"finding":"NUFIP2 was identified as part of the pre-miRNA interactome through proteomics-based pull-down with multiple pre-miRNA substrates, placing NUFIP2 among RNA-binding proteins that interact with miRNA precursors and potentially regulate miRNA biogenesis.","method":"Proteomics-based pull-down with pre-miRNA baits, mass spectrometry, RNAi/CRISPR validation of candidates","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 — systematic proteomics pull-down with pre-miRNA substrates; NUFIP2 functional role in miRNA processing not directly validated in this study","pmids":["28431233"],"is_preprint":false},{"year":2016,"finding":"NUFIP2 was identified as a component of the human Polycomb complexome through affinity purification mass spectrometry, linking NUFIP2 to the PRC2 or associated PcG protein network.","method":"Affinity purification mass spectrometry (AP-MS) systematic mapping of Polycomb group complexes","journal":"Cell reports","confidence":"Low","confidence_rationale":"Tier 3 — single AP-MS dataset; no direct functional validation of NUFIP2's role in PcG complexes","pmids":["27705803"],"is_preprint":false},{"year":2018,"finding":"BioID proximity labeling placed NUFIP2 within the mRNA-associated granule proteome, specifically in proximity to stress granule and processing body components, consistent with a role in cytoplasmic mRNA regulation.","method":"BioID proximity-dependent biotinylation, mass spectrometry, systematic mapping of 119 mRNA biology proteins","journal":"Molecular cell","confidence":"Low","confidence_rationale":"Tier 3 — proximity labeling without direct functional validation of NUFIP2's role in granule biology","pmids":["29395067"],"is_preprint":false},{"year":2025,"finding":"ATXN2L (Ataxin-2-like) was identified as the primary interactor of NUFIP2 by co-immunoprecipitation in murine embryonic fibroblasts; ATXN2L-null cells showed depletion of NUFIP2 protein, indicating ATXN2L stabilizes NUFIP2. In a SCA2 mouse model (Atxn2-CAG100-KnockIn), NUFIP2 homodimers accumulate in spinal cord tissues concurrent with ATXN2 polyQ aggregation, suggesting NUFIP2 is sequestered into pathological aggregates. NUFIP2 was the strongest co-immunoprecipitating partner among a panel of RNA-binding proteins tested.","method":"Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, mass spectrometry proteome profiling, SCA2 mouse model tissue analysis","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP with null-cell controls and proteome profiling, replicated in disease mouse model tissue","pmids":["40220918"],"is_preprint":false},{"year":2025,"finding":"NUFIP2 was identified as a context-dependent interactor of TDP-43 associated specifically with TDP-43 cytoplasmic mislocalization. NUFIP2 sequesters TDP-43 into cytoplasmic aggregates, and NUFIP2 co-localizes with TDP-43 pathology in ALS/FTLD patient tissue, implicating NUFIP2 in promoting TDP-43 dysfunction.","method":"APEX2 proximity labeling, mass spectrometry, functional screen (RNAi), immunofluorescence co-localization in patient tissue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — proximity labeling with functional screen validation and patient tissue confirmation, but preprint without peer review","pmids":[],"is_preprint":true}],"current_model":"NUFIP2 is a direct-binding cofactor of Roquin-1/2 that stabilizes Roquin and cooperatively recognizes non-canonical stem-loop structures in target mRNA 3'-UTRs to promote mRNA decay; it is also a bona fide mRNA-binding protein that associates with stress granule components, is stabilized by ATXN2L (whose loss depletes NUFIP2), and can sequester TDP-43 into cytoplasmic aggregates under mislocalization conditions relevant to ALS/FTLD."},"narrative":{"teleology":[{"year":2012,"claim":"Whether NUFIP2 directly contacts mRNA was unknown; two independent interactome capture studies using UV crosslinking in HeLa and HEK293 cells established NUFIP2 as a bona fide mRNA-binding protein, opening the question of which mRNAs and pathways it regulates.","evidence":"UV crosslinking/oligo(dT) capture (HeLa) and PAR-CLIP/oligo(dT) capture (HEK293) with quantitative mass spectrometry","pmids":["22658674","22681889"],"confidence":"Medium","gaps":["Specific mRNA targets not identified","Functional consequence of mRNA binding not tested","RNA-binding domain(s) of NUFIP2 not mapped"]},{"year":2017,"claim":"NUFIP2's interaction with pre-miRNA substrates was discovered through proteomics pull-downs, extending its RNA-binding repertoire beyond mRNA to miRNA precursors, though its functional role in miRNA biogenesis was not resolved.","evidence":"Proteomics-based pull-down with multiple pre-miRNA baits followed by mass spectrometry","pmids":["28431233"],"confidence":"Medium","gaps":["No direct evidence that NUFIP2 regulates miRNA processing or maturation","Whether pre-miRNA binding is independent of or related to Roquin pathway unknown"]},{"year":2018,"claim":"The central mechanistic question—how NUFIP2 participates in post-transcriptional regulation—was answered by showing it is a direct, high-affinity cofactor of Roquin-1/2 that is required for Roquin-mediated mRNA decay and cooperatively binds non-canonical stem-loop elements in 3′-UTRs of immune-regulatory transcripts.","evidence":"RNAi screen of ~1500 genes, co-immunoprecipitation, direct binding/EMSA, and 3′-UTR reporter decay assays in human and murine cells","pmids":["29352114"],"confidence":"High","gaps":["Structural basis of the NUFIP2–Roquin interface not determined","Full transcriptome-wide repertoire of NUFIP2-dependent Roquin targets not mapped","Whether NUFIP2 has Roquin-independent mRNA-regulatory functions remains untested"]},{"year":2025,"claim":"The question of what stabilizes NUFIP2 protein was resolved by identifying ATXN2L as its primary physical interactor whose loss depletes NUFIP2; furthermore, NUFIP2 homodimers accumulate in spinal cord aggregates in a SCA2 mouse model, linking NUFIP2 to polyglutamine neurodegeneration.","evidence":"Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, proteome profiling, SCA2 Atxn2-CAG100 knock-in mouse tissue analysis","pmids":["40220918"],"confidence":"Medium","gaps":["Mechanism by which ATXN2L stabilizes NUFIP2 (direct protection vs. transcriptional) not dissected","Whether NUFIP2 aggregation is a driver or bystander in SCA2 pathology unclear","Relationship between ATXN2L–NUFIP2 axis and Roquin-mediated mRNA decay not tested"]},{"year":2025,"claim":"NUFIP2 was shown to interact with cytoplasmically mislocalized TDP-43, sequestering it into aggregates and co-localizing with TDP-43 pathology in ALS/FTLD patient tissue, establishing a disease-relevant gain-of-function interaction.","evidence":"APEX2 proximity labeling, RNAi functional screen, immunofluorescence in patient tissue (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Whether NUFIP2 knockdown rescues TDP-43 aggregation in vivo not shown","Molecular determinants of the NUFIP2–TDP-43 interaction not mapped"]},{"year":null,"claim":"Major open questions include whether NUFIP2 possesses Roquin-independent mRNA-regulatory activities, the structural basis of its interactions with Roquin and ATXN2L, and whether its aggregation in SCA2 and ALS/FTLD is pathogenic or a secondary consequence of broader RNA granule dysregulation.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No genome-wide map of NUFIP2 direct RNA targets (e.g., CLIP-seq)","No high-resolution structure of NUFIP2 or its complexes","Causal role in neurodegeneration not established by genetic rescue or knockout models"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,1,2,3]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,7]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,7]}],"complexes":[],"partners":["RC3H1","RC3H2","ATXN2L","TARDBP"],"other_free_text":[]},"mechanistic_narrative":"NUFIP2 is an RNA-binding protein that functions as a direct high-affinity cofactor of the Roquin-1/2 post-transcriptional regulators, cooperatively recognizing non-canonical stem-loop structures in target mRNA 3′-UTRs (including ICOS and Ox40) to promote mRNA decay [PMID:29352114]. Independent UV-crosslinking and oligo(dT) capture studies confirmed NUFIP2 as a bona fide mRNA-binding protein, and it associates with pre-miRNA substrates and stress granule/processing body components [PMID:22658674, PMID:22681889, PMID:28431233]. NUFIP2 protein stability depends on ATXN2L, and in neurodegenerative disease contexts NUFIP2 accumulates in pathological aggregates—homodimerizing in SCA2 spinal cord tissue with polyQ-expanded ATXN2 and co-localizing with cytoplasmic TDP-43 inclusions in ALS/FTLD patient tissue [PMID:40220918]."},"prefetch_data":{"uniprot":{"accession":"Q7Z417","full_name":"FMR1-interacting protein NUFIP2","aliases":["82 kDa FMRP-interacting protein","82-FIP","Cell proliferation-inducing gene 1 protein","FMRP-interacting protein 2","Nuclear FMR1-interacting protein 2"],"length_aa":695,"mass_kda":76.1,"function":"Binds RNA","subcellular_location":"Nucleus; Cytoplasm; Cytoplasm, Stress granule","url":"https://www.uniprot.org/uniprotkb/Q7Z417/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NUFIP2","classification":"Not Classified","n_dependent_lines":40,"n_total_lines":1208,"dependency_fraction":0.033112582781456956},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000108256","cell_line_id":"CID001517","localizations":[{"compartment":"cytoplasmic","grade":3}],"interactors":[{"gene":"DDX6","stoichiometry":10.0},{"gene":"RPS16","stoichiometry":4.0},{"gene":"ATG13","stoichiometry":0.2},{"gene":"ATG4B","stoichiometry":0.2},{"gene":"ATXN2L","stoichiometry":0.2},{"gene":"CAPRIN1","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"DRG1","stoichiometry":0.2},{"gene":"EIF2S3","stoichiometry":0.2},{"gene":"EIF3B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001517","total_profiled":1310},"omim":[{"mim_id":"609356","title":"NUCLEAR FMRP-INTERACTING PROTEIN 2; NUFIP2","url":"https://www.omim.org/entry/609356"},{"mim_id":"309550","title":"FRAGILE X MESSENGER RIBONUCLEOPROTEIN 1; FMR1","url":"https://www.omim.org/entry/309550"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":75.4}],"url":"https://www.proteinatlas.org/search/NUFIP2"},"hgnc":{"alias_symbol":["KIAA1321","MGC117262","PIG1","182-FIP","FIP-82","82-FIP","NUFP2"],"prev_symbol":[]},"alphafold":{"accession":"Q7Z417","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7Z417","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q7Z417-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q7Z417-F1-predicted_aligned_error_v6.png","plddt_mean":47.66},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NUFIP2","jax_strain_url":"https://www.jax.org/strain/search?query=NUFIP2"},"sequence":{"accession":"Q7Z417","fasta_url":"https://rest.uniprot.org/uniprotkb/Q7Z417.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q7Z417/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7Z417"}},"corpus_meta":[{"pmid":"11706006","id":"PMC_11706006","title":"Galectin-7 (PIG1) exhibits pro-apoptotic function through JNK activation and mitochondrial cytochrome c release.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11706006","citation_count":173,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"16774992","id":"PMC_16774992","title":"The C. elegans MELK ortholog PIG-1 regulates cell size asymmetry and daughter cell fate in asymmetric neuroblast divisions.","date":"2006","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/16774992","citation_count":82,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"9918396","id":"PMC_9918396","title":"Novel erythromycins from a recombinant Saccharopolyspora erythraea strain NRRL 2338 pIG1. 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neurodegeneration.","date":"2022","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/35063084","citation_count":256,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28431233","id":"PMC_28431233","title":"A Compendium of RNA-Binding Proteins that Regulate MicroRNA Biogenesis.","date":"2017","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/28431233","citation_count":248,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"27705803","id":"PMC_27705803","title":"A High-Density Map for Navigating the Human Polycomb Complexome.","date":"2016","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/27705803","citation_count":216,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10976,"output_tokens":923,"usd":0.023387},"stage2":{"model":"claude-opus-4-6","input_tokens":4105,"output_tokens":1450,"usd":0.085163},"total_usd":0.277437,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":22826,"output_tokens":2772,"usd":0.055029},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":5551,"output_tokens":1926,"usd":0.113858}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"NUFIP2 directly binds Roquin-1/Roquin-2 with high affinity and acts as a cofactor that stabilizes NUFIP2 in cells. NUFIP2 cooperatively binds with Roquin to non-canonical stem-loop structures in the 3'-UTRs of ICOS and Ox40 mRNAs, promoting Roquin-induced mRNA decay and post-transcriptional repression of ICOS.\",\n      \"method\": \"RNA interference screen (~1500 genes), direct binding assays, co-immunoprecipitation, luciferase reporter assays, endogenous protein interaction studies\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (RNAi screen, direct binding, Co-IP, reporter assays) in a single rigorous study with functional validation\",\n      \"pmids\": [\"29352114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ATXN2L primarily interacts with NUFIP2 (identified as its strongest interactor among RNA-binding proteins by co-immunoprecipitation/mass spectrometry). NUFIP2 protein is depleted in ATXN2L-null fibroblasts, indicating ATXN2L stabilizes NUFIP2. NUFIP2 homodimers accumulate in spinal cord tissues during ATXN2 polyQ-expansion-driven aggregation, suggesting NUFIP2 is sequestered into pathological aggregates.\",\n      \"method\": \"Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, mass spectrometry proteome profiling, SCA2 mouse model (Atxn2-CAG100-KnockIn)\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with MS and genetic model, but single study\",\n      \"pmids\": [\"40220918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NUFIP2 interacts with TDP-43 under conditions of cytoplasmic mislocalization and sequesters TDP-43 into cytoplasmic aggregates; NUFIP2 co-localizes with TDP-43 pathology in ALS/FTLD patient tissue.\",\n      \"method\": \"APEX2-driven proximity labeling, mass spectrometry interactome profiling, functional screen, co-localization in patient tissue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — proximity labeling/MS plus functional screen and patient tissue validation, but preprint single study\",\n      \"pmids\": [\"bio_10.1101_2025.04.07.646890\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"NUFIP2 is an RNA-binding cofactor that directly and cooperatively binds Roquin proteins to facilitate recognition and decay of structured 3'-UTR elements in target mRNAs (e.g., ICOS, Ox40); it is stabilized by ATXN2L interaction in cells and, under disease conditions (TDP-43 proteinopathy, ATXN2 polyQ expansion), NUFIP2 can be sequestered into cytoplasmic aggregates, implicating it in RNA granule surveillance and neurodegeneration.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries from KEEP papers only.\n\n**Classification:**\n\n- Papers [1], [2] (corpus): PIG1/galectin-7 → EXCLUDE (alias collision)\n- Paper [2] corpus PIG-1/MELK C.elegans → EXCLUDE (symbol collision, unrelated organism/protein)\n- Papers [3], [5], [6], [8], [9], [12], [13], [16], [17] (corpus): PIG1/PIG-1 in yeast, Drosophila, fungi, C.elegans → EXCLUDE (symbol collisions)\n- Paper [7]: PIG1 melanocyte cell line → EXCLUDE (PIG1 here is a cell line name, not NUFIP2)\n- Paper [10]: Scedosporium PIG1 → EXCLUDE (fungal gene)\n- Paper [14]: mmu_circ_0001442/miR-125a-3p/NUFIP2 axis → EXCLUDE (alt-locus product: circRNA axis, NUFIP2 is downstream target but the paper is about the circRNA, not NUFIP2 mechanism)\n- Paper [15]: PIG1/PIG3V melanocyte cell lines, SIRT7 → EXCLUDE (PIG1/PIG3V are cell line names)\n- Paper [18]: PIG1 melanocyte cell line → EXCLUDE\n- Paper [20]: SASH1/PIG1 cell line → EXCLUDE\n\n**Corpus KEEP:**\n- [4]: NUFIP2 + Roquin → KEEP\n- [11]: ATXN2L + NUFIP2 → KEEP\n- [19]: NUFIP2 + TDP-43 → KEEP (preprint)\n\n**Gene2pubmed curated papers:**\n- [1] Olsen 2006 phosphoproteomics: NUFIP2 detected as phosphoprotein → KEEP (minor)\n- [2] Castello 2012 mRNA interactome: NUFIP2 identified as RBP → KEEP\n- [5] Sowa 2009 DUB interactome: may include NUFIP2 → minor\n- [6] Jain 2016 stress granules proteome → KEEP if NUFIP2 mentioned\n- [7] BioPlex 2015 → KEEP (interactome, NUFIP2 interactions)\n- [8] BioPlex 2.0 2017 → KEEP\n- [16] Youn 2018 BioID mRNA granules → KEEP\n- [29] Treiber 2017 pre-miRNA RBPs → KEEP (NUFIP2 identified)\n- [30] Hauri 2016 Polycomb complexome → KEEP (NUFIP2 in PcG context)\n- [20] OpenCell 2022 → KEEP\n- [24] Go 2021 BioID human cell → KEEP\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"NUFIP2 was identified as a direct cofactor of Roquin-1/2 RNA-binding proteins. NUFIP2 binds directly and with high affinity to Roquin, which in turn stabilizes NUFIP2 in cells. NUFIP2 is required for Roquin-induced mRNA decay of target transcripts such as ICOS and Ox40. NUFIP2 and Roquin cooperatively bind non-canonical stem-loop structures in the 3'-UTRs of target mRNAs (including unconventional tandem loops in the ICOS and Ox40 3'-UTRs), establishing NUFIP2 as a cofactor that contributes to mRNA target recognition by Roquin.\",\n      \"method\": \"RNA interference screen (~1500 genes), co-immunoprecipitation, direct binding assays, EMSA/binding affinity measurements, reporter assays for mRNA decay, endogenous Roquin knockdown with ICOS/Ox40 3'-UTR reporters\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding assays, functional mRNA decay assays, RNAi screen validation, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"29352114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NUFIP2 was identified as a bona fide mRNA-binding protein (RBP) through UV crosslinking and oligo(dT) capture (interactome capture) of proliferating HeLa cells, indicating NUFIP2 directly contacts mRNA in living cells.\",\n      \"method\": \"UV crosslinking, oligo(dT) purification, quantitative mass spectrometry (interactome capture)\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic biochemical capture with statistical validation, but functional consequence not characterized in this study\",\n      \"pmids\": [\"22658674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NUFIP2 was independently confirmed as an mRNA-binding protein via photoreactive nucleotide-enhanced UV crosslinking and oligo(dT) purification in HEK293 cells, further establishing its direct RNA-binding activity.\",\n      \"method\": \"PAR-CLIP (photoreactive nucleotide-enhanced UV crosslinking), oligo(dT) purification, quantitative proteomics\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — orthogonal crosslinking method independently replicating RBP identity, single study without functional follow-up\",\n      \"pmids\": [\"22681889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NUFIP2 was identified as part of the pre-miRNA interactome through proteomics-based pull-down with multiple pre-miRNA substrates, placing NUFIP2 among RNA-binding proteins that interact with miRNA precursors and potentially regulate miRNA biogenesis.\",\n      \"method\": \"Proteomics-based pull-down with pre-miRNA baits, mass spectrometry, RNAi/CRISPR validation of candidates\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic proteomics pull-down with pre-miRNA substrates; NUFIP2 functional role in miRNA processing not directly validated in this study\",\n      \"pmids\": [\"28431233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NUFIP2 was identified as a component of the human Polycomb complexome through affinity purification mass spectrometry, linking NUFIP2 to the PRC2 or associated PcG protein network.\",\n      \"method\": \"Affinity purification mass spectrometry (AP-MS) systematic mapping of Polycomb group complexes\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single AP-MS dataset; no direct functional validation of NUFIP2's role in PcG complexes\",\n      \"pmids\": [\"27705803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"BioID proximity labeling placed NUFIP2 within the mRNA-associated granule proteome, specifically in proximity to stress granule and processing body components, consistent with a role in cytoplasmic mRNA regulation.\",\n      \"method\": \"BioID proximity-dependent biotinylation, mass spectrometry, systematic mapping of 119 mRNA biology proteins\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — proximity labeling without direct functional validation of NUFIP2's role in granule biology\",\n      \"pmids\": [\"29395067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ATXN2L (Ataxin-2-like) was identified as the primary interactor of NUFIP2 by co-immunoprecipitation in murine embryonic fibroblasts; ATXN2L-null cells showed depletion of NUFIP2 protein, indicating ATXN2L stabilizes NUFIP2. In a SCA2 mouse model (Atxn2-CAG100-KnockIn), NUFIP2 homodimers accumulate in spinal cord tissues concurrent with ATXN2 polyQ aggregation, suggesting NUFIP2 is sequestered into pathological aggregates. NUFIP2 was the strongest co-immunoprecipitating partner among a panel of RNA-binding proteins tested.\",\n      \"method\": \"Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, mass spectrometry proteome profiling, SCA2 mouse model tissue analysis\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with null-cell controls and proteome profiling, replicated in disease mouse model tissue\",\n      \"pmids\": [\"40220918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NUFIP2 was identified as a context-dependent interactor of TDP-43 associated specifically with TDP-43 cytoplasmic mislocalization. NUFIP2 sequesters TDP-43 into cytoplasmic aggregates, and NUFIP2 co-localizes with TDP-43 pathology in ALS/FTLD patient tissue, implicating NUFIP2 in promoting TDP-43 dysfunction.\",\n      \"method\": \"APEX2 proximity labeling, mass spectrometry, functional screen (RNAi), immunofluorescence co-localization in patient tissue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — proximity labeling with functional screen validation and patient tissue confirmation, but preprint without peer review\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"NUFIP2 is a direct-binding cofactor of Roquin-1/2 that stabilizes Roquin and cooperatively recognizes non-canonical stem-loop structures in target mRNA 3'-UTRs to promote mRNA decay; it is also a bona fide mRNA-binding protein that associates with stress granule components, is stabilized by ATXN2L (whose loss depletes NUFIP2), and can sequester TDP-43 into cytoplasmic aggregates under mislocalization conditions relevant to ALS/FTLD.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NUFIP2 is an RNA-binding cofactor that directly binds Roquin-1 and Roquin-2 with high affinity and cooperatively enhances their recognition of non-canonical stem-loop structures in the 3′-UTRs of target mRNAs such as ICOS and Ox40, thereby promoting Roquin-mediated mRNA decay and post-transcriptional gene repression [PMID:29352114]. NUFIP2 protein stability depends on interaction with ATXN2L, as NUFIP2 is depleted in ATXN2L-null cells [PMID:40220918]. Under pathological conditions, NUFIP2 homodimers accumulate in spinal cord aggregates in an ATXN2 polyQ-expansion mouse model, and NUFIP2 co-localizes with TDP-43 pathology in ALS/FTLD patient tissue, implicating it in RNA granule dysregulation during neurodegeneration [PMID:40220918].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of NUFIP2 as a direct, high-affinity Roquin cofactor resolved how Roquin recognizes non-canonical stem-loop elements in target 3′-UTRs and established NUFIP2 as a functional component of post-transcriptional mRNA decay.\",\n      \"evidence\": \"RNAi screen of ~1500 genes, direct binding assays, co-immunoprecipitation, and luciferase reporter assays in mammalian cells\",\n      \"pmids\": [\"29352114\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the NUFIP2–Roquin–RNA ternary complex is unresolved\",\n        \"Full repertoire of NUFIP2-dependent mRNA targets beyond ICOS and Ox40 is unknown\",\n        \"Whether NUFIP2 functions independently of Roquin in other RNA regulatory contexts has not been tested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating that ATXN2L stabilizes NUFIP2 protein and that NUFIP2 homodimers accumulate in polyQ-driven aggregates linked NUFIP2 to RNA granule pathology in spinocerebellar ataxia type 2.\",\n      \"evidence\": \"Co-immunoprecipitation/mass spectrometry in wild-type and ATXN2L-null murine embryonic fibroblasts; SCA2 Atxn2-CAG100-KnockIn mouse spinal cord tissue\",\n      \"pmids\": [\"40220918\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which ATXN2L stabilizes NUFIP2 (direct binding interface, degradation pathway) is undefined\",\n        \"Functional consequence of NUFIP2 sequestration into aggregates on Roquin-dependent mRNA regulation is untested\",\n        \"Single study; independent replication needed\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that NUFIP2 interacts with cytoplasmically mislocalized TDP-43 and co-localizes with TDP-43 pathology in ALS/FTLD patients extended NUFIP2's role in aggregate biology to a second major neurodegenerative proteinopathy.\",\n      \"evidence\": \"(preprint) APEX2 proximity labeling, mass spectrometry, functional screen, and co-localization in ALS/FTLD patient tissue\",\n      \"pmids\": [\"bio_10.1101_2025.04.07.646890\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint; not yet peer-reviewed\",\n        \"Whether NUFIP2 is an active driver of TDP-43 aggregation or a passively sequestered bystander is unresolved\",\n        \"Direct binding interface between NUFIP2 and TDP-43 has not been mapped\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the structural basis of the NUFIP2–Roquin–RNA complex, the full spectrum of NUFIP2-regulated transcripts, whether NUFIP2 aggregate sequestration causally contributes to neurodegeneration, and whether NUFIP2 possesses Roquin-independent RNA-regulatory functions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of NUFIP2 in complex with any partner\",\n        \"Genome-wide identification of NUFIP2-dependent mRNAs (e.g., by CLIP) has not been reported\",\n        \"Causal role of NUFIP2 in neurodegeneration not established by loss-of-function or rescue experiments in vivo\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RC3H1\",\n      \"RC3H2\",\n      \"ATXN2L\",\n      \"TDP-43\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"NUFIP2 is an RNA-binding protein that functions as a direct high-affinity cofactor of the Roquin-1/2 post-transcriptional regulators, cooperatively recognizing non-canonical stem-loop structures in target mRNA 3′-UTRs (including ICOS and Ox40) to promote mRNA decay [PMID:29352114]. Independent UV-crosslinking and oligo(dT) capture studies confirmed NUFIP2 as a bona fide mRNA-binding protein, and it associates with pre-miRNA substrates and stress granule/processing body components [PMID:22658674, PMID:22681889, PMID:28431233]. NUFIP2 protein stability depends on ATXN2L, and in neurodegenerative disease contexts NUFIP2 accumulates in pathological aggregates—homodimerizing in SCA2 spinal cord tissue with polyQ-expanded ATXN2 and co-localizing with cytoplasmic TDP-43 inclusions in ALS/FTLD patient tissue [PMID:40220918].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Whether NUFIP2 directly contacts mRNA was unknown; two independent interactome capture studies using UV crosslinking in HeLa and HEK293 cells established NUFIP2 as a bona fide mRNA-binding protein, opening the question of which mRNAs and pathways it regulates.\",\n      \"evidence\": \"UV crosslinking/oligo(dT) capture (HeLa) and PAR-CLIP/oligo(dT) capture (HEK293) with quantitative mass spectrometry\",\n      \"pmids\": [\"22658674\", \"22681889\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific mRNA targets not identified\",\n        \"Functional consequence of mRNA binding not tested\",\n        \"RNA-binding domain(s) of NUFIP2 not mapped\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"NUFIP2's interaction with pre-miRNA substrates was discovered through proteomics pull-downs, extending its RNA-binding repertoire beyond mRNA to miRNA precursors, though its functional role in miRNA biogenesis was not resolved.\",\n      \"evidence\": \"Proteomics-based pull-down with multiple pre-miRNA baits followed by mass spectrometry\",\n      \"pmids\": [\"28431233\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No direct evidence that NUFIP2 regulates miRNA processing or maturation\",\n        \"Whether pre-miRNA binding is independent of or related to Roquin pathway unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The central mechanistic question—how NUFIP2 participates in post-transcriptional regulation—was answered by showing it is a direct, high-affinity cofactor of Roquin-1/2 that is required for Roquin-mediated mRNA decay and cooperatively binds non-canonical stem-loop elements in 3′-UTRs of immune-regulatory transcripts.\",\n      \"evidence\": \"RNAi screen of ~1500 genes, co-immunoprecipitation, direct binding/EMSA, and 3′-UTR reporter decay assays in human and murine cells\",\n      \"pmids\": [\"29352114\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the NUFIP2–Roquin interface not determined\",\n        \"Full transcriptome-wide repertoire of NUFIP2-dependent Roquin targets not mapped\",\n        \"Whether NUFIP2 has Roquin-independent mRNA-regulatory functions remains untested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The question of what stabilizes NUFIP2 protein was resolved by identifying ATXN2L as its primary physical interactor whose loss depletes NUFIP2; furthermore, NUFIP2 homodimers accumulate in spinal cord aggregates in a SCA2 mouse model, linking NUFIP2 to polyglutamine neurodegeneration.\",\n      \"evidence\": \"Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, proteome profiling, SCA2 Atxn2-CAG100 knock-in mouse tissue analysis\",\n      \"pmids\": [\"40220918\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which ATXN2L stabilizes NUFIP2 (direct protection vs. transcriptional) not dissected\",\n        \"Whether NUFIP2 aggregation is a driver or bystander in SCA2 pathology unclear\",\n        \"Relationship between ATXN2L–NUFIP2 axis and Roquin-mediated mRNA decay not tested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"NUFIP2 was shown to interact with cytoplasmically mislocalized TDP-43, sequestering it into aggregates and co-localizing with TDP-43 pathology in ALS/FTLD patient tissue, establishing a disease-relevant gain-of-function interaction.\",\n      \"evidence\": \"APEX2 proximity labeling, RNAi functional screen, immunofluorescence in patient tissue (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint not yet peer-reviewed\",\n        \"Whether NUFIP2 knockdown rescues TDP-43 aggregation in vivo not shown\",\n        \"Molecular determinants of the NUFIP2–TDP-43 interaction not mapped\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include whether NUFIP2 possesses Roquin-independent mRNA-regulatory activities, the structural basis of its interactions with Roquin and ATXN2L, and whether its aggregation in SCA2 and ALS/FTLD is pathogenic or a secondary consequence of broader RNA granule dysregulation.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No genome-wide map of NUFIP2 direct RNA targets (e.g., CLIP-seq)\",\n        \"No high-resolution structure of NUFIP2 or its complexes\",\n        \"Causal role in neurodegeneration not established by genetic rescue or knockout models\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RC3H1\",\n      \"RC3H2\",\n      \"ATXN2L\",\n      \"TARDBP\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}