{"gene":"ELP4","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2001,"finding":"ELP4 (together with ELP5 and ELP6) forms a discrete subcomplex of the six-subunit holo-Elongator complex, which can be separated from the Elp1/2/3 core subcomplex at higher salt concentrations; disruption of ELP4 confers phenotypes indistinguishable from those of other elp mutants.","method":"Tandem affinity purification (TAP), affinity chromatography, genetic disruption with phenotypic analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 — replicated independently by two labs in the same year using purification and genetics","pmids":["11689709","11435442"],"is_preprint":false},{"year":2002,"finding":"The three smallest Elongator subunits Elp4, Elp5, and Elp6 are required for the histone acetyltransferase (HAT) activity of the intact Elongator complex toward histone H3 (K14) and histone H4 (K8), including nucleosomal substrates.","method":"In vitro HAT assay with purified Elongator complex from deletion strains; chromatin immunoprecipitation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic assay with defined substrates and genetic knockouts, supported by in vivo ChIP","pmids":["11904415"],"is_preprint":false},{"year":2001,"finding":"ELP4 (TOT7) is genetically required for the zymocin-sensitive, RNA polymerase II-associated TOT/Elongator function; deletion of ELP4 confers zymocin resistance and complex tot phenotypes, linking ELP4 to RNAPII transcription elongation.","method":"Genetic deletion, zymocin sensitivity assays, global mRNA level measurement","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic KO with defined phenotypic readouts in yeast Elongator context","pmids":["11737649"],"is_preprint":false},{"year":2002,"finding":"Structural integrity of the Elp4/5/6 (HAP) subcomplex requires all three subunits; loss of ELP4 disrupts the interaction between Elp5 and Elp2, and the association of the HAP subcomplex with the core Elp1/2/3 subcomplex.","method":"Co-immunoprecipitation, subunit interaction mapping in deletion strains","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP across multiple subunit combinations","pmids":["12424236"],"is_preprint":false},{"year":2004,"finding":"Elp2 and Elp4 are largely dispensable for Elongator association with nascent RNA transcript in vivo, whereas Elp3 is required for this RNA interaction; Elp2 is also dispensable for holo-Elongator complex integrity.","method":"Immunoprecipitation, two-hybrid interaction mapping, in vitro binary interaction studies, in vivo Elongator-RNA association assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods defining subunit-specific roles within the complex","pmids":["15138274"],"is_preprint":false},{"year":2012,"finding":"The Elp4/5/6 subcomplex adopts a heterohexameric ring-like structure where each subunit has a RecA-ATPase-like fold; this subcomplex specifically binds tRNAs in a manner regulated by ATP.","method":"Crystal structure determination, in vitro tRNA binding assays, ATPase assays, in vivo complementation","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus multiple orthogonal in vitro and in vivo functional assays","pmids":["22343726"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of the yeast Elp4-6 subcomplex reveals that Elp6 acts as a bridge assembling Elp4 and Elp5, each adopting a RecA-ATPase-like fold; ring-shaped hexameric assembly of Elp4-6 is required for specific histone H3 binding.","method":"Crystal structure determination, site-directed mutagenesis, biochemical assembly assays, GST pulldown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — structure plus mutagenesis plus biochemical binding assays","pmids":["22556426"],"is_preprint":false},{"year":2010,"finding":"ELP4 knockdown in mouse zygotes impairs paternal genome demethylation, demonstrating a role for the Elongator complex (via its radical SAM domain on Elp3) in zygotic DNA demethylation.","method":"siRNA-mediated knockdown in mouse zygotes, live-cell imaging of methylation reporter, immunostaining, bisulfite sequencing","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — clean KD with specific phenotypic readout using multiple orthogonal methods","pmids":["20054296"],"is_preprint":false},{"year":2012,"finding":"Human ELP5 (DERP6) directly connects ELP3 to ELP4 within the Elongator complex; depletion of ELP5 or ELP6 disrupts Elongator integrity and reduces migration, invasion, and tumorigenicity of melanoma cells similarly to ELP1 or ELP3 depletion.","method":"Co-immunoprecipitation, biochemical subunit interaction analysis, cell migration/invasion assays, tumor xenograft assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP plus multiple functional cellular assays","pmids":["22854966"],"is_preprint":false},{"year":2018,"finding":"ELP4 directly interacts with the carboxyl-terminal domain (CTD) of RNA polymerase II, supporting a role for Elongator in transcription elongation; Elongator also interacts in vivo with the transcription elongation factor SUPPRESSOR OF Ty4 at target gene loci.","method":"Co-immunoprecipitation (ELP4-RNAPII CTD interaction), in vivo protein interaction, ChIP","journal":"Plant physiology","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct Co-IP of ELP4 with RNAPII CTD, but performed in Arabidopsis (plant ortholog context)","pmids":["30401723"],"is_preprint":false},{"year":2018,"finding":"ELP4 overexpression promotes migration and invasion of hepatocellular carcinoma cells; Elongator (via ELP3) activates AKT phosphorylation to upregulate MMP-2 and MMP-9 expression, driving cell migration.","method":"Overexpression and siRNA knockdown, cell migration/invasion assays, AKT inhibitor treatment, in vivo lung metastasis mouse model","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 — KD/OE with defined pathway placement via inhibitor studies and in vivo model","pmids":["29805303"],"is_preprint":false},{"year":2022,"finding":"Patient-derived missense mutations in ELP4 and ELP6 reduce tRNA modification activity of Elongator in vitro and in human and murine cells; ELP4/ELP6 mutations cause neuropathology distinct from that caused by ELP123 mutations, revealing functional divergence between the two subcomplexes for specific tRNA species and cell types during neurodevelopment.","method":"Cryo-EM/crystal structures of human and murine Elp456, in vitro tRNA modification assays, patient cell analyses, mouse modeling of pathogenic variants","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 1 — structure determination plus in vitro enzymatic assays plus in vivo mouse modeling with multiple orthogonal methods","pmids":["35698786"],"is_preprint":false},{"year":2009,"finding":"Human ELP4 partially complements yeast elp4Δ growth defects (caffeine sensitivity, heat sensitivity, 6-AU sensitivity) and partially restores gene activation (PHO5, SSA3) in the deletion strain, demonstrating functional conservation between human and yeast ELP4.","method":"Yeast complementation assay, gene expression analysis","journal":"Yi chuan xue bao = Acta genetica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional complementation across species with gene expression readout","pmids":["15473317"],"is_preprint":false},{"year":2025,"finding":"ELP4 promotes H3K27ac enrichment at the TCF7L2 promoter, enhancing its transcriptional activation, which in turn drives TLR4/NF-κB-mediated microglia M1 polarization in ischemic stroke context.","method":"Co-IP (ELP4-TCF7L2 interaction), ChIP assay (H3K27ac enrichment), knockdown/overexpression with cytokine and polarization readouts","journal":"Journal of cell communication and signaling","confidence":"Low","confidence_rationale":"Tier 3 — single lab, limited mechanistic validation, novel finding without independent replication","pmids":["39822731"],"is_preprint":false}],"current_model":"ELP4 is a subunit of the accessory Elp4/5/6 subcomplex of the Elongator complex, adopting a RecA-ATPase-like fold within a heterohexameric ring that binds tRNAs in an ATP-regulated manner; together with ELP5 and ELP6 it is required for the HAT activity of holo-Elongator toward histones H3-K14 and H4-K8, for Elongator structural integrity, and for wobble-uridine tRNA modification that underlies its essential role in neurodevelopment, with patient-derived ELP4 mutations causing reduced tRNA modification and neurological disease distinct from that caused by Elp1/2/3 subcomplex mutations."},"narrative":{"teleology":[{"year":2001,"claim":"ELP4 was identified as part of a discrete Elp4/5/6 subcomplex separable from the Elp1/2/3 core, establishing the modular architecture of Elongator and showing that ELP4 loss phenocopies other elp deletions.","evidence":"TAP purification, affinity chromatography, and genetic disruption in S. cerevisiae","pmids":["11689709","11435442","11737649"],"confidence":"High","gaps":["Structural basis for Elp4/5/6 subcomplex assembly unknown","No direct biochemical activity assigned to ELP4 itself","Mechanism by which Elp4/5/6 supports Elongator function unresolved"]},{"year":2002,"claim":"ELP4 was shown to be required for Elongator's histone acetyltransferase activity and for structural integrity of the holo-complex, revealing that the accessory subcomplex is not merely structural but essential for catalytic function.","evidence":"In vitro HAT assays on purified Elongator from deletion strains; reciprocal Co-IP mapping subunit dependencies","pmids":["11904415","12424236"],"confidence":"High","gaps":["Whether ELP4 contacts histones directly or acts allosterically on ELP3 was unknown","Whether ELP4 contributes to tRNA modification was not yet addressed"]},{"year":2004,"claim":"Dissection of subunit-specific roles showed ELP4 is largely dispensable for Elongator's association with nascent RNA transcripts, unlike ELP3, delineating functional asymmetry within the complex.","evidence":"Immunoprecipitation, two-hybrid, and in vivo Elongator-RNA association assays in yeast","pmids":["15138274"],"confidence":"High","gaps":["What substrate ELP4 contributes to recognizing remained unclear","Whether ELP4 has ATPase activity was untested"]},{"year":2010,"claim":"ELP4 knockdown in mouse zygotes impaired paternal genome demethylation, extending Elongator's functional repertoire beyond transcription elongation and tRNA modification to epigenetic reprogramming.","evidence":"siRNA knockdown in mouse zygotes with live-cell methylation imaging, immunostaining, and bisulfite sequencing","pmids":["20054296"],"confidence":"High","gaps":["Whether the demethylation role is direct or a secondary consequence of tRNA modification deficiency","Mechanism of Elp3 radical SAM involvement in demethylation not fully resolved"]},{"year":2012,"claim":"Crystal structures revealed the Elp4/5/6 subcomplex forms a RecA-ATPase-fold heterohexameric ring that binds tRNAs in an ATP-dependent manner and histone H3, providing the first structural framework for how the accessory subcomplex delivers substrates to the catalytic core.","evidence":"Crystal structure determination, in vitro tRNA/histone binding assays, site-directed mutagenesis, ATPase assays","pmids":["22343726","22556426"],"confidence":"High","gaps":["How tRNA is handed off from Elp4/5/6 ring to Elp3 active site unknown","ATP hydrolysis cycle and its coupling to tRNA release not defined","Structure of intact holo-Elongator not yet available"]},{"year":2018,"claim":"ELP4 was found to directly interact with the RNA polymerase II CTD, providing biochemical evidence for the long-proposed role of Elongator in transcription elongation beyond tRNA modification.","evidence":"Co-immunoprecipitation of ELP4 with RNAPII CTD in Arabidopsis, ChIP at target loci","pmids":["30401723"],"confidence":"Medium","gaps":["Interaction demonstrated only in plant system; conservation of ELP4-RNAPII CTD binding in mammals untested","Whether this interaction is functionally separable from tRNA modification remains unclear"]},{"year":2022,"claim":"Patient-derived ELP4 mutations were shown to reduce tRNA modification and cause neurodevelopmental disease distinct from ELP1/2/3 mutations, establishing ELP4 as a human disease gene and revealing functional divergence between the two Elongator subcomplexes for specific tRNA species and cell types.","evidence":"Cryo-EM/crystal structures of human/murine Elp456, in vitro tRNA modification assays, patient cell analyses, mouse modeling","pmids":["35698786"],"confidence":"High","gaps":["Full genotype-phenotype spectrum for ELP4 mutations not yet defined","Which specific tRNA species and neuronal populations are most sensitive to ELP4 loss","Therapeutic strategies to restore tRNA modification not explored"]},{"year":null,"claim":"How the Elp4/5/6 ring coordinates tRNA substrate selection and handoff to the Elp3 catalytic site within the intact holo-Elongator remains structurally and mechanistically unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["Full holo-Elongator structure with tRNA substrate bound not yet determined at high resolution","ATP hydrolysis cycle coupling to tRNA modification catalysis not defined","Whether ELP4's roles in histone acetylation and tRNA modification are mechanistically separable in vivo"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[5,6]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[5]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[1,6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[5,11]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[2,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[11]}],"complexes":["Elongator complex","Elp4/5/6 subcomplex"],"partners":["ELP5","ELP6","ELP3","ELP2","ELP1"],"other_free_text":[]},"mechanistic_narrative":"ELP4 is a core subunit of the Elp4/5/6 accessory subcomplex of the six-subunit Elongator complex, functioning in tRNA wobble-uridine modification, histone acetylation, and transcription elongation. Within the Elp4/5/6 subcomplex, ELP4 adopts a RecA-ATPase-like fold and assembles into a heterohexameric ring that binds tRNAs in an ATP-regulated manner and is required for the histone acetyltransferase activity of holo-Elongator toward histone H3-K14 and H4-K8 [PMID:22343726, PMID:11904415]. Loss of ELP4 disrupts subcomplex integrity and the association of Elp4/5/6 with the Elp1/2/3 catalytic core, abolishing Elongator function [PMID:12424236, PMID:11689709]. Patient-derived missense mutations in ELP4 reduce tRNA modification activity and cause a neurodevelopmental disorder distinct from that caused by mutations in Elp1/2/3 subunits, establishing ELP4 as a disease gene with subcomplex-specific neuropathological consequences [PMID:35698786]."},"prefetch_data":{"uniprot":{"accession":"Q96EB1","full_name":"Elongator complex protein 4","aliases":["PAX6 neighbor gene protein"],"length_aa":424,"mass_kda":46.6,"function":"Component of the elongator complex which is required for multiple tRNA modifications, including mcm5U (5-methoxycarbonylmethyl uridine), mcm5s2U (5-methoxycarbonylmethyl-2-thiouridine), and ncm5U (5-carbamoylmethyl uridine) (PubMed:29332244). The elongator complex catalyzes the formation of carboxymethyluridine in the wobble base at position 34 in tRNAs (PubMed:29332244)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q96EB1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ELP4","classification":"Not Classified","n_dependent_lines":609,"n_total_lines":1208,"dependency_fraction":0.5041390728476821},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ELP4","total_profiled":1310},"omim":[{"mim_id":"617141","title":"ANIRIDIA 2; AN2","url":"https://www.omim.org/entry/617141"},{"mim_id":"616902","title":"CHROMOSOME 11p13 DELETION SYNDROME, DISTAL","url":"https://www.omim.org/entry/616902"},{"mim_id":"616054","title":"ELONGATOR ACETYLTRANSFERASE COMPLEX, SUBUNIT 2; ELP2","url":"https://www.omim.org/entry/616054"},{"mim_id":"615019","title":"ELONGATOR ACETYLTRANSFERASE COMPLEX, SUBUNIT 5; ELP5","url":"https://www.omim.org/entry/615019"},{"mim_id":"612722","title":"ELONGATOR ACETYLTRANSFERASE COMPLEX, SUBUNIT 3; ELP3","url":"https://www.omim.org/entry/612722"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ELP4"},"hgnc":{"alias_symbol":["PAXNEB"],"prev_symbol":["C11orf19"]},"alphafold":{"accession":"Q96EB1","domains":[{"cath_id":"3.40.50.300","chopping":"53-151_179-386","consensus_level":"high","plddt":84.7076,"start":53,"end":386}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96EB1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96EB1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96EB1-F1-predicted_aligned_error_v6.png","plddt_mean":73.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ELP4","jax_strain_url":"https://www.jax.org/strain/search?query=ELP4"},"sequence":{"accession":"Q96EB1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96EB1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96EB1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96EB1"}},"corpus_meta":[{"pmid":"11904415","id":"PMC_11904415","title":"Elongator is a 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\"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — replicated independently by two labs in the same year using purification and genetics\",\n      \"pmids\": [\"11689709\", \"11435442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The three smallest Elongator subunits Elp4, Elp5, and Elp6 are required for the histone acetyltransferase (HAT) activity of the intact Elongator complex toward histone H3 (K14) and histone H4 (K8), including nucleosomal substrates.\",\n      \"method\": \"In vitro HAT assay with purified Elongator complex from deletion strains; chromatin immunoprecipitation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assay with defined substrates and genetic knockouts, supported by in vivo ChIP\",\n      \"pmids\": [\"11904415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ELP4 (TOT7) is genetically required for the zymocin-sensitive, RNA polymerase II-associated TOT/Elongator function; deletion of ELP4 confers zymocin resistance and complex tot phenotypes, linking ELP4 to RNAPII transcription elongation.\",\n      \"method\": \"Genetic deletion, zymocin sensitivity assays, global mRNA level measurement\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined phenotypic readouts in yeast Elongator context\",\n      \"pmids\": [\"11737649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Structural integrity of the Elp4/5/6 (HAP) subcomplex requires all three subunits; loss of ELP4 disrupts the interaction between Elp5 and Elp2, and the association of the HAP subcomplex with the core Elp1/2/3 subcomplex.\",\n      \"method\": \"Co-immunoprecipitation, subunit interaction mapping in deletion strains\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP across multiple subunit combinations\",\n      \"pmids\": [\"12424236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Elp2 and Elp4 are largely dispensable for Elongator association with nascent RNA transcript in vivo, whereas Elp3 is required for this RNA interaction; Elp2 is also dispensable for holo-Elongator complex integrity.\",\n      \"method\": \"Immunoprecipitation, two-hybrid interaction mapping, in vitro binary interaction studies, in vivo Elongator-RNA association assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods defining subunit-specific roles within the complex\",\n      \"pmids\": [\"15138274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The Elp4/5/6 subcomplex adopts a heterohexameric ring-like structure where each subunit has a RecA-ATPase-like fold; this subcomplex specifically binds tRNAs in a manner regulated by ATP.\",\n      \"method\": \"Crystal structure determination, in vitro tRNA binding assays, ATPase assays, in vivo complementation\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus multiple orthogonal in vitro and in vivo functional assays\",\n      \"pmids\": [\"22343726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of the yeast Elp4-6 subcomplex reveals that Elp6 acts as a bridge assembling Elp4 and Elp5, each adopting a RecA-ATPase-like fold; ring-shaped hexameric assembly of Elp4-6 is required for specific histone H3 binding.\",\n      \"method\": \"Crystal structure determination, site-directed mutagenesis, biochemical assembly assays, GST pulldown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structure plus mutagenesis plus biochemical binding assays\",\n      \"pmids\": [\"22556426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ELP4 knockdown in mouse zygotes impairs paternal genome demethylation, demonstrating a role for the Elongator complex (via its radical SAM domain on Elp3) in zygotic DNA demethylation.\",\n      \"method\": \"siRNA-mediated knockdown in mouse zygotes, live-cell imaging of methylation reporter, immunostaining, bisulfite sequencing\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with specific phenotypic readout using multiple orthogonal methods\",\n      \"pmids\": [\"20054296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Human ELP5 (DERP6) directly connects ELP3 to ELP4 within the Elongator complex; depletion of ELP5 or ELP6 disrupts Elongator integrity and reduces migration, invasion, and tumorigenicity of melanoma cells similarly to ELP1 or ELP3 depletion.\",\n      \"method\": \"Co-immunoprecipitation, biochemical subunit interaction analysis, cell migration/invasion assays, tumor xenograft assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP plus multiple functional cellular assays\",\n      \"pmids\": [\"22854966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ELP4 directly interacts with the carboxyl-terminal domain (CTD) of RNA polymerase II, supporting a role for Elongator in transcription elongation; Elongator also interacts in vivo with the transcription elongation factor SUPPRESSOR OF Ty4 at target gene loci.\",\n      \"method\": \"Co-immunoprecipitation (ELP4-RNAPII CTD interaction), in vivo protein interaction, ChIP\",\n      \"journal\": \"Plant physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct Co-IP of ELP4 with RNAPII CTD, but performed in Arabidopsis (plant ortholog context)\",\n      \"pmids\": [\"30401723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ELP4 overexpression promotes migration and invasion of hepatocellular carcinoma cells; Elongator (via ELP3) activates AKT phosphorylation to upregulate MMP-2 and MMP-9 expression, driving cell migration.\",\n      \"method\": \"Overexpression and siRNA knockdown, cell migration/invasion assays, AKT inhibitor treatment, in vivo lung metastasis mouse model\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD/OE with defined pathway placement via inhibitor studies and in vivo model\",\n      \"pmids\": [\"29805303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Patient-derived missense mutations in ELP4 and ELP6 reduce tRNA modification activity of Elongator in vitro and in human and murine cells; ELP4/ELP6 mutations cause neuropathology distinct from that caused by ELP123 mutations, revealing functional divergence between the two subcomplexes for specific tRNA species and cell types during neurodevelopment.\",\n      \"method\": \"Cryo-EM/crystal structures of human and murine Elp456, in vitro tRNA modification assays, patient cell analyses, mouse modeling of pathogenic variants\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structure determination plus in vitro enzymatic assays plus in vivo mouse modeling with multiple orthogonal methods\",\n      \"pmids\": [\"35698786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human ELP4 partially complements yeast elp4Δ growth defects (caffeine sensitivity, heat sensitivity, 6-AU sensitivity) and partially restores gene activation (PHO5, SSA3) in the deletion strain, demonstrating functional conservation between human and yeast ELP4.\",\n      \"method\": \"Yeast complementation assay, gene expression analysis\",\n      \"journal\": \"Yi chuan xue bao = Acta genetica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional complementation across species with gene expression readout\",\n      \"pmids\": [\"15473317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ELP4 promotes H3K27ac enrichment at the TCF7L2 promoter, enhancing its transcriptional activation, which in turn drives TLR4/NF-κB-mediated microglia M1 polarization in ischemic stroke context.\",\n      \"method\": \"Co-IP (ELP4-TCF7L2 interaction), ChIP assay (H3K27ac enrichment), knockdown/overexpression with cytokine and polarization readouts\",\n      \"journal\": \"Journal of cell communication and signaling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, limited mechanistic validation, novel finding without independent replication\",\n      \"pmids\": [\"39822731\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ELP4 is a subunit of the accessory Elp4/5/6 subcomplex of the Elongator complex, adopting a RecA-ATPase-like fold within a heterohexameric ring that binds tRNAs in an ATP-regulated manner; together with ELP5 and ELP6 it is required for the HAT activity of holo-Elongator toward histones H3-K14 and H4-K8, for Elongator structural integrity, and for wobble-uridine tRNA modification that underlies its essential role in neurodevelopment, with patient-derived ELP4 mutations causing reduced tRNA modification and neurological disease distinct from that caused by Elp1/2/3 subcomplex mutations.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ELP4 is a core subunit of the Elp4/5/6 accessory subcomplex of the six-subunit Elongator complex, functioning in tRNA wobble-uridine modification, histone acetylation, and transcription elongation. Within the Elp4/5/6 subcomplex, ELP4 adopts a RecA-ATPase-like fold and assembles into a heterohexameric ring that binds tRNAs in an ATP-regulated manner and is required for the histone acetyltransferase activity of holo-Elongator toward histone H3-K14 and H4-K8 [PMID:22343726, PMID:11904415]. Loss of ELP4 disrupts subcomplex integrity and the association of Elp4/5/6 with the Elp1/2/3 catalytic core, abolishing Elongator function [PMID:12424236, PMID:11689709]. Patient-derived missense mutations in ELP4 reduce tRNA modification activity and cause a neurodevelopmental disorder distinct from that caused by mutations in Elp1/2/3 subunits, establishing ELP4 as a disease gene with subcomplex-specific neuropathological consequences [PMID:35698786].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"ELP4 was identified as part of a discrete Elp4/5/6 subcomplex separable from the Elp1/2/3 core, establishing the modular architecture of Elongator and showing that ELP4 loss phenocopies other elp deletions.\",\n      \"evidence\": \"TAP purification, affinity chromatography, and genetic disruption in S. cerevisiae\",\n      \"pmids\": [\"11689709\", \"11435442\", \"11737649\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for Elp4/5/6 subcomplex assembly unknown\",\n        \"No direct biochemical activity assigned to ELP4 itself\",\n        \"Mechanism by which Elp4/5/6 supports Elongator function unresolved\"\n      ]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"ELP4 was shown to be required for Elongator's histone acetyltransferase activity and for structural integrity of the holo-complex, revealing that the accessory subcomplex is not merely structural but essential for catalytic function.\",\n      \"evidence\": \"In vitro HAT assays on purified Elongator from deletion strains; reciprocal Co-IP mapping subunit dependencies\",\n      \"pmids\": [\"11904415\", \"12424236\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ELP4 contacts histones directly or acts allosterically on ELP3 was unknown\",\n        \"Whether ELP4 contributes to tRNA modification was not yet addressed\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Dissection of subunit-specific roles showed ELP4 is largely dispensable for Elongator's association with nascent RNA transcripts, unlike ELP3, delineating functional asymmetry within the complex.\",\n      \"evidence\": \"Immunoprecipitation, two-hybrid, and in vivo Elongator-RNA association assays in yeast\",\n      \"pmids\": [\"15138274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"What substrate ELP4 contributes to recognizing remained unclear\",\n        \"Whether ELP4 has ATPase activity was untested\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"ELP4 knockdown in mouse zygotes impaired paternal genome demethylation, extending Elongator's functional repertoire beyond transcription elongation and tRNA modification to epigenetic reprogramming.\",\n      \"evidence\": \"siRNA knockdown in mouse zygotes with live-cell methylation imaging, immunostaining, and bisulfite sequencing\",\n      \"pmids\": [\"20054296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether the demethylation role is direct or a secondary consequence of tRNA modification deficiency\",\n        \"Mechanism of Elp3 radical SAM involvement in demethylation not fully resolved\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Crystal structures revealed the Elp4/5/6 subcomplex forms a RecA-ATPase-fold heterohexameric ring that binds tRNAs in an ATP-dependent manner and histone H3, providing the first structural framework for how the accessory subcomplex delivers substrates to the catalytic core.\",\n      \"evidence\": \"Crystal structure determination, in vitro tRNA/histone binding assays, site-directed mutagenesis, ATPase assays\",\n      \"pmids\": [\"22343726\", \"22556426\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How tRNA is handed off from Elp4/5/6 ring to Elp3 active site unknown\",\n        \"ATP hydrolysis cycle and its coupling to tRNA release not defined\",\n        \"Structure of intact holo-Elongator not yet available\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"ELP4 was found to directly interact with the RNA polymerase II CTD, providing biochemical evidence for the long-proposed role of Elongator in transcription elongation beyond tRNA modification.\",\n      \"evidence\": \"Co-immunoprecipitation of ELP4 with RNAPII CTD in Arabidopsis, ChIP at target loci\",\n      \"pmids\": [\"30401723\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Interaction demonstrated only in plant system; conservation of ELP4-RNAPII CTD binding in mammals untested\",\n        \"Whether this interaction is functionally separable from tRNA modification remains unclear\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Patient-derived ELP4 mutations were shown to reduce tRNA modification and cause neurodevelopmental disease distinct from ELP1/2/3 mutations, establishing ELP4 as a human disease gene and revealing functional divergence between the two Elongator subcomplexes for specific tRNA species and cell types.\",\n      \"evidence\": \"Cryo-EM/crystal structures of human/murine Elp456, in vitro tRNA modification assays, patient cell analyses, mouse modeling\",\n      \"pmids\": [\"35698786\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Full genotype-phenotype spectrum for ELP4 mutations not yet defined\",\n        \"Which specific tRNA species and neuronal populations are most sensitive to ELP4 loss\",\n        \"Therapeutic strategies to restore tRNA modification not explored\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the Elp4/5/6 ring coordinates tRNA substrate selection and handoff to the Elp3 catalytic site within the intact holo-Elongator remains structurally and mechanistically unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Full holo-Elongator structure with tRNA substrate bound not yet determined at high resolution\",\n        \"ATP hydrolysis cycle coupling to tRNA modification catalysis not defined\",\n        \"Whether ELP4's roles in histone acetylation and tRNA modification are mechanistically separable in vivo\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [1, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [5, 11]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [2, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"complexes\": [\n      \"Elongator complex\",\n      \"Elp4/5/6 subcomplex\"\n    ],\n    \"partners\": [\n      \"ELP5\",\n      \"ELP6\",\n      \"ELP3\",\n      \"ELP2\",\n      \"ELP1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}