{"gene":"EIF4G3","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":1998,"finding":"eIF4GII (encoded by EIF4G3) was identified as a functional homolog of eIF4GI in mammals, sharing 46% amino acid identity. Far-Western analysis and co-immunoprecipitation demonstrated that eIF4GII directly interacts with eIF4E, eIF4A, and eIF3, and exists in a cap-binding complex with eIF4E in HeLa cells. eIF4GII restores cap-dependent translation in reticulocyte lysate depleted of eIF4G by rhinovirus 2A protease cleavage, and is cleaved upon picornavirus infection.","method":"Far-Western analysis, co-immunoprecipitation, cap affinity chromatography, in vitro translation rescue assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (Far-Western, co-IP, cap affinity, functional rescue) in a single foundational study; widely replicated","pmids":["9418880"],"is_preprint":false},{"year":1998,"finding":"Proteolysis of eIF4GII, but not eIF4GI alone, coincides with the shutoff of host cell protein synthesis after poliovirus infection. Cleavage of both eIF4GI and eIF4GII is required for complete inhibition of host translation; eIF4GII is more resistant to poliovirus-mediated cleavage than eIF4GI.","method":"Western blot analysis of eIF4GI/II integrity during poliovirus infection; metabolic labeling to measure protein synthesis; use of virus replication inhibitors","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple conditions tested, replicated by subsequent rhinovirus study; strong functional correlation established","pmids":["9736694"],"is_preprint":false},{"year":1998,"finding":"eIF4GII contains a 29-amino-acid sequence in its N-terminal region that is nearly identical to that of eIF4GI, and the full-length eIF4GII binds poly(A)-binding protein (PABP) via this site (specifically via RRM1 and RRM2 of PABP). This interaction implicates eIF4GII in poly(A)-dependent translation.","method":"Co-immunoprecipitation, deletion analysis, in vitro translation assay with deadenylated vs. polyadenylated mRNA","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 — co-IP with deletion mapping plus functional in vitro translation assay; strong evidence","pmids":["9857202"],"is_preprint":false},{"year":1999,"finding":"eIF4GII cleavage is the rate-limiting step in the shutoff of host protein synthesis after human rhinovirus 14 (HRV-14) infection. eIF4GI is cleaved early but host translation persists until eIF4GII is substantially cleaved (~6 h post-infection), demonstrating that eIF4GII cleavage correlates with translational inhibition.","method":"Western blot analysis of eIF4GI/II cleavage kinetics; metabolic labeling of protein synthesis in HRV-14-infected HeLa cells","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — kinetic correlation established across multiple time points; independent replication of poliovirus findings","pmids":["10074204"],"is_preprint":false},{"year":1999,"finding":"Mnk1 kinase associates with the eIF4F complex via interaction with the C-terminal region of eIF4G (both eIF4GI and eIF4GII), providing a docking site for Mnk1 to phosphorylate eIF4E at Ser209.","method":"Co-immunoprecipitation, in vitro binding assays, dominant-negative and activated Mnk1 mutants","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP and mutagenesis confirmed interaction; replicated independently","pmids":["9878069"],"is_preprint":false},{"year":2001,"finding":"The FMDV IRES interacts with eIF4GII, and the RNA determinants for this interaction are shared with eIF4GI. The C-terminal fragment of eIF4GII generated by Lb protease binds the FMDV IRES as efficiently as intact eIF4GII, indicating the IRES-binding domain resides in the C-terminal portion. eIF4G-IRES interaction is the limiting factor for IRES activity.","method":"UV crosslinking, competition experiments, bicistronic reporter assays in transfected cells, protease cleavage","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 — crosslinking and competition assays with functional validation, single lab","pmids":["11565745"],"is_preprint":false},{"year":2002,"finding":"HIV-1 protease cleaves eIF4GI but not eIF4GII in vitro and in cell extracts, demonstrating differential susceptibility of the two isoforms to this viral protease. Cleavage of eIF4GI by HIV-1 protease impairs both cap-dependent and IRES-containing RNA translation (except HCV IRES), in contrast to picornaviral proteases.","method":"In vitro protease assay with cell extracts and rabbit reticulocyte lysate; HIV-1 protease inhibitor (palinavir) as control; in vitro translation assays","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro reconstitution with inhibitor controls; single lab","pmids":["12054764"],"is_preprint":false},{"year":2002,"finding":"HRV2 2A proteinase directly cleaves both eIF4GI and eIF4GII without requiring activation of a cellular proteinase, as demonstrated using a thermosensitive 2Apro mutant in temperature-shift experiments with HeLa cell extracts.","method":"Temperature-shift experiments with thermosensitive HRV2 2Apro mutant in cytoplasmic cell extracts; Western blot","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — thermosensitive mutant provides mechanistic discrimination between direct and indirect cleavage","pmids":["12123803"],"is_preprint":false},{"year":2003,"finding":"The HRV2 2Apro cleavage site in eIF4GII was identified in vitro as PLLNV(699)*GSR, located seven amino acids C-terminal to the analogous cleavage site in eIF4GI (LSTR681*GPP), demonstrating that the two isoforms have distinct but nearby cleavage sites for the same viral protease.","method":"In vitro cleavage assay with recombinant HRV2 2Apro, N-terminal sequencing of cleavage fragments","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 — direct biochemical identification of cleavage site by N-terminal sequencing of in vitro cleavage products","pmids":["12663812"],"is_preprint":false},{"year":2004,"finding":"eIF4GII, but not eIF4GI, is selectively recruited to capped mRNA at the onset of erythroid cell differentiation induced by thrombopoietin. This selective recruitment is coincident with strong phosphorylation of eIF4E and release of 4E-BP1 from the cap structure, providing the first evidence that eIF4GI and eIF4GII fulfill distinct roles in mammalian cells.","method":"Cap affinity chromatography from differentiating cells, Western blot for eIF4GI/II, 4E-BP1, and phospho-eIF4E","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 — cap affinity pulldown with differential detection; single lab but clear functional distinction shown","pmids":["15143184"],"is_preprint":false},{"year":2006,"finding":"Differential cleavage of eIF4GI and eIF4GII by poliovirus 2Apro revealed functionally distinct roles: de novo translation of newly synthesized mRNA depends primarily on eIF4GI integrity, whereas ongoing translation and reinitiation of pre-existing mRNA translation after polysome run-off are more dependent on eIF4GII. Translation of HSP70 mRNA depends more on eIF4GII than eIF4GI.","method":"Electroporation of EMCV IRES-2Apro mRNA into HeLa and BHK-21 cells; luciferase reporter assays; polysome run-off experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — differential cleavage system with multiple reporter assays; single lab","pmids":["16959778"],"is_preprint":false},{"year":2009,"finding":"Depletion of eIF4GI or eIF4GII individually only moderately inhibits cellular protein synthesis, while depletion of both together has a slightly greater inhibitory effect. Vaccinia virus (VV) mRNA translation requires eIF4GI/II and eIF4E (cap-dependent), whereas vesicular stomatitis virus (VSV) mRNA translation does not require eIF4GI or eIF4GII despite being capped.","method":"siRNA-mediated depletion of eIF4GI and/or eIF4GII in HeLa cells; metabolic labeling; viral protein synthesis assays","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with multiple viral and cellular translation readouts; single lab","pmids":["19769989"],"is_preprint":false},{"year":2010,"finding":"ENU-induced mutation of mouse Eif4g3 (repro8 allele) causes male-limited infertility due to meiotic arrest at the G2/MI transition. EIF4G3 is required for translational control of HSPA2 (a chaperone for CDK1/CDC2A kinase) in spermatocytes: Hspa2 mRNA is present but HSPA2 protein is absent in mutant cells, resulting in dramatically reduced CDK1 kinase activity. This is the first genetic evidence for selective translational control of meiotic exit in mammalian spermatocytes.","method":"ENU mutagenesis screen, positional cloning, histology, immunofluorescence, Western blot, kinase activity assay (CDK1), comparison with Hspa2 knockout phenotype","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic loss-of-function with defined molecular target (HSPA2 translation), multiple orthogonal readouts, phenotype mimics Hspa2 KO","pmids":["20430745"],"is_preprint":false},{"year":2001,"finding":"Both eIF4GI and eIF4GII are cleaved in Jurkat T cells in response to proteasome inhibitors (MG132, lactacystin) and immunosuppressants (FTY720, cyclosporin A) by caspase-8-independent mechanisms. Proteasome inhibitor-induced cleavage of eIF4GI generates a novel fragment lacking the eIF4E-binding capability, distinct from the anti-Fas-induced cleavage pattern.","method":"Western blot with anti-peptide antisera specific for eIF4GI and eIF4GII; caspase-8-deficient Jurkat cell line; pharmacological inhibitors","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — isogenic caspase-8-deficient cell line used for mechanistic dissection; multiple agents tested","pmids":["11513883"],"is_preprint":false},{"year":2012,"finding":"CaMKI phosphorylates eIF4GII at Ser1156 in an activity-dependent manner in hippocampal neurons. This phosphorylation promotes selective recruitment of eIF4GII (but not eIF4GI) into the eIF4F complex assembled at the mRNA 5' cap, upregulating cap-dependent translation. RNAi knockdown of eIF4GII reduces cap-dependent translation and decreases density of dendritic filopodia and spine formation without affecting dendritic arborization.","method":"In vitro CaMKI phosphorylation assay, m7GTP cap affinity purification, bicistronic luciferase reporter, RNAi knockdown in hippocampal neurons, confocal imaging of spine morphology, pharmacological inhibition (STO-609, NMDA receptor blockers)","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro kinase assay with site-specific mutant (S1156A), cap pulldown, functional reporters, and morphological phenotype; multiple orthogonal methods","pmids":["22514323"],"is_preprint":false},{"year":2012,"finding":"DEAF1 transcriptionally regulates Eif4g3 expression in lymph node stromal cells (LNSCs). Reduced DEAF1 function (in Deaf1-KO mice, NOD mice, and T1D patients) leads to decreased Eif4g3 transcription and also increased Caspase 3 expression (which degrades eIF4GII protein). Polysome profiling showed that reduced eIF4GII in LNSCs diminishes translation of multiple genes including Anpep.","method":"qRT-PCR, siRNA silencing of Deaf1, polysome profiling, Western blot, comparison across Deaf1-KO mice, NOD mice, and T1D patient samples","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple model systems and polysome profiling; single lab","pmids":["22923498"],"is_preprint":false},{"year":2012,"finding":"Multiple isoforms of eIF4GII are generated in mammalian cells via alternative promoters, alternative splicing, and use of a non-canonical CUG initiation codon that extends the N-terminus. The novel N-terminal-extended eIF4GII isoforms rescue translation in eIF4GI/eIF4GII double-knockdown cells as effectively as the eIF4GIf/e isoforms, more robustly than the original eIF4GII, suggesting the eIF4GII N-terminus has a role distinct from eIF4GI in translation initiation factor assembly.","method":"RT-PCR, 5' RACE, RNAi knockdown, rescue experiments with overexpression of isoforms, metabolic labeling of translation rates","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 — isoform identification combined with functional rescue assays; single lab","pmids":["22909319"],"is_preprint":false},{"year":2013,"finding":"eIF4GII undergoes novel Cdk1-dependent N-terminal phosphorylation in nocodazole-arrested cells. This phosphorylation, along with eIF2α phosphorylation and polysome disaggregation, contributes to the inhibition of translation observed in nocodazole-arrested cells, which had previously been attributed to mitosis itself. Translation rates do not intrinsically slow during mitosis when cells are synchronized without nocodazole.","method":"FACS-synchronized HeLa cells (double thymidine block or RO3306 release), pulse labeling with [35S]-methionine, confocal microscopy of translation factors, polysome analysis, phosphorylation analysis by Western blot","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 — multiple synchronization strategies tested with metabolic labeling; single lab but mechanistic reinterpretation supported by multiple approaches","pmids":["24091728"],"is_preprint":false},{"year":2014,"finding":"miR-520c-3p directly targets eIF4GII (EIF4G3) mRNA, repressing its translation. Downregulation of eIF4GII by either miR-520c-3p or siRNA decreases global translation, reduces cell proliferation, promotes cellular senescence, and suppresses tumor growth in xenograft models of diffuse large B-cell lymphoma.","method":"miRNA overexpression, siRNA knockdown, luciferase reporter assays (3'UTR targeting), xenograft tumor assay, Western blot, proliferation assays","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct target validation by reporter assay combined with in vivo xenograft and in vitro phenotyping; single lab","pmids":["24497838"],"is_preprint":false},{"year":2018,"finding":"EIF4G3 localizes unexpectedly to the nucleus of mouse spermatocytes, with high enrichment in the XY body (the chromatin domain of transcriptionally silenced sex chromosomes). Many other translation-related proteins also localize to the XY body, suggesting a role for this domain in storing or poising translation complexes before the meiotic division phase.","method":"Immunofluorescence, confocal microscopy, subcellular fractionation, co-localization with XY body markers (γH2AX, BRCA1)","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 3 — direct localization by immunofluorescence with functional inference; novel finding but functional consequence not fully established","pmids":["29161344"],"is_preprint":false},{"year":2021,"finding":"EIF4G3 is a direct target of miR-375 in lung squamous cell carcinoma cells. Chidamide treatment upregulates miR-375, which suppresses EIF4G3 mRNA and protein expression. Silencing EIF4G3 independently induces apoptosis and suppresses tumor growth, while inhibition of miR-375 reverses chidamide-induced apoptosis and stemness suppression, confirming EIF4G3 as a functional mediator of the chidamide/radiation response.","method":"miRNA microarray, luciferase reporter assay (direct miR-375 target validation), Western blot, siRNA knockdown of EIF4G3, xenograft tumor assay","journal":"Journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct target validation by reporter assay with functional rescue; single lab","pmids":["34194495"],"is_preprint":false}],"current_model":"EIF4G3 (eIF4GII) is a scaffold protein of the eIF4F translation initiation complex that directly binds eIF4E, eIF4A, eIF3, and PABP to mediate cap-dependent and poly(A)-dependent translation; it is differentially regulated from its paralog eIF4GI through selective recruitment during cell differentiation, CaMKI-mediated phosphorylation at Ser1156 to enhance neuronal cap-dependent translation, Cdk1-dependent phosphorylation during mitosis, transcriptional control by DEAF1, and post-transcriptional repression by miR-520c-3p and miR-375; it is cleaved by picornaviral 2A proteases (at PLLNV699*GSR in eIF4GII) to shut off host translation, and is genetically required in mouse spermatocytes for HSPA2 translation and meiotic exit, where it also localizes to the nuclear XY body."},"narrative":{"teleology":[{"year":1998,"claim":"Identification of eIF4GII as a second mammalian eIF4G isoform established that the eIF4F scaffold function is shared between two paralogs capable of independently assembling the cap-binding complex with eIF4E, eIF4A, eIF3, and PABP.","evidence":"Far-Western, co-IP, cap affinity chromatography, in vitro translation rescue in HeLa cells and reticulocyte lysate; PABP interaction mapped via deletion analysis","pmids":["9418880","9857202"],"confidence":"High","gaps":["Whether eIF4GI and eIF4GII have distinct mRNA-selective roles was unknown","Structural basis of eIF4GII scaffold assembly not determined"]},{"year":1999,"claim":"Kinetic studies of picornavirus infections revealed that eIF4GII cleavage—not eIF4GI cleavage—is the rate-limiting step for host translation shutoff, demonstrating that eIF4GII alone can sustain cap-dependent translation.","evidence":"Western blot kinetics of eIF4GI/II cleavage correlated with metabolic labeling during poliovirus and HRV-14 infection of HeLa cells","pmids":["9736694","10074204"],"confidence":"High","gaps":["Exact cleavage site in eIF4GII was not yet mapped","Whether eIF4GII resistance reflects sequence divergence or structural protection was unclear"]},{"year":1999,"claim":"Demonstration that Mnk1 docks on the C-terminus of both eIF4GI and eIF4GII to phosphorylate eIF4E positioned the eIF4G scaffold as a signaling platform integrating MAPK/p38 input into translation.","evidence":"Co-IP with dominant-negative and activated Mnk1 mutants","pmids":["9878069"],"confidence":"High","gaps":["Whether Mnk1 preferentially utilizes eIF4GII versus eIF4GI in specific contexts was not tested"]},{"year":2003,"claim":"Biochemical identification of the HRV2 2Apro cleavage site at PLLNV699↓GSR in eIF4GII resolved the molecular basis of differential protease sensitivity between the two paralogs.","evidence":"In vitro cleavage with recombinant 2Apro followed by N-terminal sequencing of cleavage fragments","pmids":["12663812"],"confidence":"High","gaps":["Structural determinants governing slower cleavage kinetics of eIF4GII versus eIF4GI not resolved"]},{"year":2004,"claim":"Selective recruitment of eIF4GII, but not eIF4GI, to the cap structure during thrombopoietin-induced erythroid differentiation provided the first evidence that the two paralogs fulfill non-redundant physiological roles.","evidence":"Cap affinity chromatography from differentiating UT-7 cells with Western blot for eIF4GI/II and 4E-BP1","pmids":["15143184"],"confidence":"Medium","gaps":["Molecular basis of selective eIF4GII recruitment unknown","Target mRNAs preferentially translated by eIF4GII in this context not identified"]},{"year":2006,"claim":"Differential cleavage experiments revealed that eIF4GII is preferentially required for ongoing/reinitiation translation of pre-existing mRNAs (including HSP70), whereas eIF4GI supports de novo translation of newly exported mRNAs.","evidence":"Electroporation of EMCV-IRES-2Apro mRNA into HeLa and BHK-21 cells with luciferase reporters and polysome run-off","pmids":["16959778"],"confidence":"Medium","gaps":["Genome-wide identification of eIF4GII-dependent mRNAs not performed","Whether this division of labor holds outside picornavirus-cleavage conditions is unknown"]},{"year":2010,"claim":"Genetic loss of Eif4g3 in mouse spermatocytes caused meiotic arrest at G2/MI by failing to translate HSPA2, a chaperone required for CDK1 activation, establishing eIF4GII as an essential translational regulator of mammalian meiosis.","evidence":"ENU mutagenesis (repro8 allele), positional cloning, histology, immunofluorescence, Western blot, CDK1 kinase assay in mouse testis","pmids":["20430745"],"confidence":"High","gaps":["Whether eIF4GII recognizes specific cis-elements in Hspa2 mRNA is unknown","Full spectrum of eIF4GII-dependent mRNAs in spermatocytes not catalogued"]},{"year":2012,"claim":"CaMKI-mediated phosphorylation of eIF4GII at Ser1156 in hippocampal neurons was shown to enhance eIF4GII recruitment to the cap and promote dendritic spine formation, linking activity-dependent signaling to selective eIF4GII-driven translation in neurons.","evidence":"In vitro kinase assay with S1156A mutant, cap affinity purification, bicistronic reporter, RNAi knockdown with confocal spine imaging in hippocampal neurons","pmids":["22514323"],"confidence":"High","gaps":["Neuronal mRNAs selectively translated via phospho-S1156 eIF4GII not identified","Whether this phosphorylation event is relevant in vivo (learning/memory paradigms) is untested"]},{"year":2012,"claim":"Parallel studies revealed that eIF4GII expression is transcriptionally regulated by DEAF1 in lymph node stromal cells and that multiple N-terminally extended eIF4GII isoforms generated from alternative promoters and a CUG start codon have distinct translational rescue activities.","evidence":"qRT-PCR, siRNA, polysome profiling in LNSCs; 5′-RACE, isoform overexpression rescue of double-knockdown cells with metabolic labeling","pmids":["22923498","22909319"],"confidence":"Medium","gaps":["Physiological significance of individual N-terminal isoforms in specific tissues not established","Whether DEAF1-dependent regulation of eIF4GII contributes to autoimmune phenotypes remains correlative"]},{"year":2014,"claim":"Post-transcriptional repression of EIF4G3 by miR-520c-3p was shown to reduce global translation, promote senescence, and suppress lymphoma xenograft growth, implicating eIF4GII as a rate-limiting translation factor for cell proliferation.","evidence":"3′-UTR luciferase reporter, siRNA knockdown, xenograft tumor assay in diffuse large B-cell lymphoma model","pmids":["24497838"],"confidence":"Medium","gaps":["Whether eIF4GII loss triggers senescence through a specific mRNA target or globally reduced translation is unresolved"]},{"year":2018,"claim":"Unexpected nuclear localization of EIF4G3 in mouse spermatocytes, particularly at the XY body, raised the possibility that eIF4GII has non-cytoplasmic roles during meiotic prophase.","evidence":"Immunofluorescence with confocal microscopy and co-localization with γH2AX and BRCA1 in mouse spermatocyte spreads","pmids":["29161344"],"confidence":"Medium","gaps":["Functional significance of XY body localization not demonstrated","Whether nuclear eIF4GII has any translation-independent function is unknown","Biochemical validation of nuclear localization (fractionation controls) limited"]},{"year":null,"claim":"The mRNA-selective mechanism by which eIF4GII controls translation of specific targets (e.g. HSPA2, dendritic mRNAs) remains undefined—no cis-regulatory elements, RNA-binding partners, or structural features distinguishing eIF4GII from eIF4GI target selection have been identified.","evidence":"","pmids":[],"confidence":"Low","gaps":["No genome-wide identification of eIF4GII-dependent translatome in any tissue","No high-resolution structure of eIF4GII or eIF4GII-specific domains","Mechanism of isoform-selective cap recruitment is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[0,9,10,12,14]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,9,14]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,9,10,12,14,16]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,3,6,7,8]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[12,19]}],"complexes":["eIF4F"],"partners":["EIF4E","EIF4A1","EIF3A","PABPC1","MKNK1","CAMK1"],"other_free_text":[]},"mechanistic_narrative":"EIF4G3 (eIF4GII) is a scaffold subunit of the eIF4F translation initiation complex that bridges cap-bound eIF4E, the RNA helicase eIF4A, the 40S-recruiting factor eIF3, the poly(A)-binding protein PABP, and the eIF4E kinase Mnk1, thereby coupling 5′-cap recognition and 3′-poly(A) tail circularization to ribosome loading [PMID:9418880, PMID:9857202, PMID:9878069]. Although broadly redundant with its paralog eIF4GI for bulk translation, eIF4GII is selectively recruited to the cap during erythroid differentiation, is phosphorylated by CaMKI at Ser1156 to promote cap-dependent translation and dendritic spine formation in hippocampal neurons, and is genetically required in mouse spermatocytes for translational activation of HSPA2 mRNA and completion of meiosis [PMID:15143184, PMID:22514323, PMID:20430745]. Picornaviral 2A proteases cleave eIF4GII at a specific site (PLLNV699↓GSR), and its delayed cleavage relative to eIF4GI is rate-limiting for host translation shutoff during rhinovirus infection [PMID:12663812, PMID:10074204]. EIF4G3 expression is transcriptionally controlled by DEAF1 and post-transcriptionally repressed by miR-520c-3p and miR-375; its downregulation reduces global translation, promotes senescence, and suppresses tumor xenograft growth [PMID:22923498, PMID:24497838, PMID:34194495]."},"prefetch_data":{"uniprot":{"accession":"O43432","full_name":"Eukaryotic translation initiation factor 4 gamma 3","aliases":["eIF-4-gamma II","eIF4GII"],"length_aa":1585,"mass_kda":176.7,"function":"Component of the protein complex eIF4F, which is involved in the recognition of the mRNA cap, ATP-dependent unwinding of 5'-terminal secondary structure and recruitment of mRNA to the ribosome (PubMed:9418880). Functional homolog of EIF4G1 (PubMed:9418880)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/O43432/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/EIF4G3","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"DDX6","stoichiometry":0.2},{"gene":"EIF2S3","stoichiometry":0.2},{"gene":"EIF3B","stoichiometry":0.2},{"gene":"EIF4A1","stoichiometry":0.2},{"gene":"GPAT3","stoichiometry":0.2},{"gene":"GSPT1","stoichiometry":0.2},{"gene":"PSMC4","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"VRK2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/EIF4G3","total_profiled":1310},"omim":[{"mim_id":"615908","title":"MICRO RNA 520C; MIR520C","url":"https://www.omim.org/entry/615908"},{"mim_id":"615828","title":"VULTO-VAN SILFHOUT-DE VRIES SYNDROME; 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systems\",\n      \"pmids\": [\"9736694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"EIF4G3 (eIF4GII) cleavage by rhinovirus 2Apro is the rate-limiting step in the shutoff of host protein synthesis after human rhinovirus 14 infection, with eIF4GII cleavage correlating temporally with the decline in host translation.\",\n      \"method\": \"Western blot kinetics in HRV-14-infected HeLa cells, pulse-labeling of protein synthesis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional correlation with kinetic data, independent replication of eIF4GII cleavage role across virus systems\",\n      \"pmids\": [\"10074204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"EIF4G3 (eIF4GII) interacts with the FMDV IRES through the same RNA determinants as eIF4GI, and the C-terminal fragment of eIF4GII generated by Lb protease retains IRES-binding activity.\",\n      \"method\": \"UV crosslinking, RNA-protein interaction assays, competition experiments with FMDV IRES\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct RNA-protein binding assay with competition controls, single lab\",\n      \"pmids\": [\"11565745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HIV-1 protease cleaves eIF4GI but not eIF4GII in vitro, demonstrating that eIF4GII is resistant to HIV-1 protease cleavage and distinguishing it functionally from eIF4GI.\",\n      \"method\": \"In vitro protease cleavage assay with cell extracts and rabbit reticulocyte lysate, prevented by HIV-1 protease inhibitor palinavir\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution assay with pharmacological control, clear negative result for eIF4GII\",\n      \"pmids\": [\"12054764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Human rhinovirus 2 2Apro directly cleaves eIF4GI and eIF4GII via a direct mechanism (not through activation of a cellular proteinase), as demonstrated using a thermosensitive 2Apro mutant.\",\n      \"method\": \"Temperature-shift experiments with ts-2Apro in cytoplasmic HeLa cell extracts\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with temperature-sensitive mutant, single lab\",\n      \"pmids\": [\"12123803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The human rhinovirus 2 2Apro cleavage site in eIF4GII was identified in vitro as PLLNV(699)*GSR, located seven amino acids C-terminal to the cleavage site in eIF4GI (LSTR681*GPP), indicating isoform-specific cleavage sites.\",\n      \"method\": \"In vitro cleavage assay with purified 2Apro, N-terminal sequencing of cleavage products\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical assay identifying precise cleavage site\",\n      \"pmids\": [\"12663812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"EIF4GII, but not eIF4GI, is selectively recruited to capped mRNA at the onset of erythroid cell differentiation, coincident with long-lasting eIF4E phosphorylation and release of 4E-BP1 from the cap structure, demonstrating that eIF4GI and eIF4GII have distinct functional roles regulated by cytokines such as thrombopoietin.\",\n      \"method\": \"Cap structure pulldown (m7GTP-Sepharose), Western blot, cytokine stimulation assays in differentiating cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct cap-binding pulldown with functional differentiation context, single lab\",\n      \"pmids\": [\"15143184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Reinitiation of preexisting mRNA translation after polysome run-off is dependent on eIF4GII (EIF4G3) integrity, whereas de novo cap-dependent translation of newly synthesized mRNA depends more on eIF4GI integrity; eIF4GII is also required for translation of HSP70 mRNA.\",\n      \"method\": \"Differential protease expression (poliovirus 2Apro mRNA electroporation), luciferase reporter assays in BHK-21 and HeLa cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — differential cleavage system with functional reporter assays, single lab\",\n      \"pmids\": [\"16959778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"EIF4G3 is required for translation of HSPA2 (a chaperone for CDK1) in mouse spermatocytes; loss-of-function of Eif4g3 causes meiotic arrest at the G2/MI transition with dramatically reduced CDK1 kinase activity, providing genetic evidence for selective translational control of meiotic exit.\",\n      \"method\": \"ENU-induced repro8 mutation in mice, genetic epistasis with Hspa2 knockout, polysome profiling, Western blot, CDK1 kinase assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with defined biochemical readout (CDK1 activity, HSPA2 protein absent despite mRNA present), strong phenotypic specificity\",\n      \"pmids\": [\"20430745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CaMKI phosphorylates Ser1156 of EIF4G3 (eIF4GII) in neurons, promoting its selective recruitment to the eIF4F cap-binding complex in an activity-dependent manner; RNAi knockdown of eIF4GII attenuates cap-dependent translation and reduces dendritic filopodia and spine density.\",\n      \"method\": \"In vitro CaMKI phosphorylation assay, m7GTP-Sepharose cap pulldown, S1156A phospho-dead mutant, siRNA knockdown, bicistronic luciferase reporter, dendritic spine imaging in hippocampal neurons\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro kinase assay, mutagenesis, cap pulldown, and morphological phenotype all converge in single study\",\n      \"pmids\": [\"22514323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DEAF1 transcriptionally regulates Eif4g3 expression in lymph node stromal cells; reduced DEAF1 function decreases Eif4g3 transcription and leads to diminished polysome-associated translation of genes including Anpep.\",\n      \"method\": \"Polysome profiling, siRNA knockdown of Deaf1, qRT-PCR, Western blot in mouse lymph node stromal cells\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — polysome profiling with functional target identification, single lab\",\n      \"pmids\": [\"22923498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Multiple isoforms of eIF4GII (EIF4G3) are generated through alternative promoters, splice sites, and a non-canonical CUG initiation codon extending the N-terminus; these isoforms differ in their ability to rescue translation in eIF4GI/eIF4GII double-knockdown cells.\",\n      \"method\": \"RT-PCR, cDNA cloning, translation rescue assays in siRNA double-knockdown cells, non-canonical initiation codon identification\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional rescue assay with defined isoforms, single lab\",\n      \"pmids\": [\"22909319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"EIF4G3 (eIF4GII) undergoes novel Cdk1-dependent N-terminal phosphorylation in nocodazole-arrested cells; eIF4GII and other translation initiation factors are enriched at the microtubule organizing centers, mitotic spindle, and midbody during cytokinesis.\",\n      \"method\": \"Confocal microscopy, FACS, phosphorylation analysis by Western blot, pulse-labeling of protein synthesis in synchronized HeLa cells\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by confocal microscopy with identification of Cdk1-dependent phosphorylation, single lab\",\n      \"pmids\": [\"24091728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"miR-520c-3p directly targets the EIF4G3 (eIF4GII) mRNA, reducing eIF4GII protein synthesis; siRNA-mediated knockdown of eIF4GII decreases global translation, cell proliferation, and colony formation, and induces cellular senescence.\",\n      \"method\": \"miRNA overexpression, siRNA knockdown, luciferase reporter assay, Western blot, xenograft mouse model\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct targeting validated by reporter assay with functional phenotype, single lab\",\n      \"pmids\": [\"24497838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"EIF4G3 localizes unexpectedly to the nucleus of mouse spermatocytes, where it is highly enriched in the XY body (transcriptionally inactive sex chromosome domain), implicating a role in mRNA metabolism or translational poising during meiotic prophase.\",\n      \"method\": \"Immunofluorescence, subcellular fractionation, confocal microscopy in mouse spermatocytes\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with defined subcellular compartment and functional implication, single lab\",\n      \"pmids\": [\"29161344\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"EIF4G3 (eIF4GII) is a scaffold protein of the eIF4F translation initiation complex that bridges mRNA cap-binding (via eIF4E) and ribosome recruitment (via eIF3); it is selectively cleaved by picornaviral proteases at a distinct site (PLLNV699*GSR) compared to eIF4GI, with cleavage of both isoforms required for complete host translation shutoff; EIF4G3 is phosphorylated by CaMKI at Ser1156 to promote activity-dependent recruitment to the eIF4F complex in neurons, and by Cdk1 during mitosis; it is required for selective translation of HSPA2 in spermatocytes to enable meiotic exit, localizes to the XY body nucleus in spermatocytes, and is preferentially recruited to cap structures during cell differentiation, demonstrating functional distinctions from eIF4GI.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries from KEPT papers.\n\n**Classification:**\n\n- [Corpus 1] PMID:9736694 — KEEP (eIF4GII/EIF4G3, poliovirus cleavage)\n- [Corpus 2] PMID:11565745 — KEEP (eIF4GII interactions with IRES)\n- [Corpus 3] PMID:10074204 — KEEP (eIF4GII cleavage, rhinovirus)\n- [Corpus 4] PMID:12054764 — KEEP (eIF4GII, HIV-1 protease)\n- [Corpus 5] PMID:35780119 — EXCLUDE (Case B: circRNA alt-locus product, circ-EIF4G3)\n- [Corpus 6] PMID:20430745 — KEEP (mouse Eif4g3, spermatogenesis)\n- [Corpus 7] PMID:24091728 — KEEP (eIF4GII phosphorylation, mitosis)\n- [Corpus 8] PMID:16959778 — KEEP (eIF4GI vs eIF4GII differential cleavage)\n- [Corpus 9] PMID:24497838 — KEEP (miR-520c-3p targets eIF4GII)\n- [Corpus 10] PMID:15143184 — KEEP (eIF4GII selective recruitment in differentiation)\n- [Corpus 11] PMID:22923498 — KEEP (DEAF1 regulates Eif4g3 transcription)\n- [Corpus 12] PMID:19769989 — KEEP (eIF4GI/II knockdown, viral translation)\n- [Corpus 13] PMID:12663812 — KEEP (HRV2 cleavage site in eIF4GII)\n- [Corpus 14] PMID:29161344 — KEEP (EIF4G3 nuclear/XY body localization)\n- [Corpus 15] PMID:22514323 — KEEP (CaMKI phosphorylates eIF4GII Ser1156)\n- [Corpus 16] PMID:22909319 — KEEP (multiple eIF4GII isoforms)\n- [Corpus 17] PMID:12123803 — KEEP (direct cleavage of eIF4GII by HRV2 2Apro)\n- [Corpus 18] PMID:19655339 — KEEP (FRET biosensor for eIF4GI/II cleavage)\n- [Corpus 19] PMID:34194495 — KEEP (miR-375 targets EIF4G3 in lung cancer)\n- [Corpus 20] PMID:31257089 — EXCLUDE (Case B: circRNA circ-EIF4G3)\n- [Corpus 21] PMID:11513883 — KEEP (proteasome inhibitors cleave eIF4GII)\n- [Corpus 22] PMID:41776682 — EXCLUDE (Case A: Leishmania EIF4G3, symbol collision with non-orthologous organism — Leishmania is a highly divergent protozoan; context is fundamentally incompatible with mammalian EIF4G3)\n\n**Gene2pubmed additional papers:**\n- PMID:9418880 — KEEP (original discovery of eIF4GII)\n- PMID:9857202 — KEEP (eIF4GII binds PABP)\n- PMID:9878069 — KEEP (eIF4G recruits Mnk1; relevant to eIF4GII)\n- PMID:22514323 — already listed\n- Most others (PMID:17081983, 19239892, 10872469, 22658674, 12477932, 16964243, 19615732, 26186194, 28514442, 26496610, 22681889, 29507755, 17353931, 26344197, 26912792, 29395067, 20020773, 16344560, 28611215, 15146197, 10022874, 21873635, 15489334, 8125298, 22939629) — EXCLUDE (large-scale proteomics/genomics studies not specifically about EIF4G3 mechanism, or general reviews)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"eIF4GII (encoded by EIF4G3) was identified as a functional homolog of eIF4GI in mammals, sharing 46% amino acid identity. Far-Western analysis and co-immunoprecipitation demonstrated that eIF4GII directly interacts with eIF4E, eIF4A, and eIF3, and exists in a cap-binding complex with eIF4E in HeLa cells. eIF4GII restores cap-dependent translation in reticulocyte lysate depleted of eIF4G by rhinovirus 2A protease cleavage, and is cleaved upon picornavirus infection.\",\n      \"method\": \"Far-Western analysis, co-immunoprecipitation, cap affinity chromatography, in vitro translation rescue assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (Far-Western, co-IP, cap affinity, functional rescue) in a single foundational study; widely replicated\",\n      \"pmids\": [\"9418880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Proteolysis of eIF4GII, but not eIF4GI alone, coincides with the shutoff of host cell protein synthesis after poliovirus infection. Cleavage of both eIF4GI and eIF4GII is required for complete inhibition of host translation; eIF4GII is more resistant to poliovirus-mediated cleavage than eIF4GI.\",\n      \"method\": \"Western blot analysis of eIF4GI/II integrity during poliovirus infection; metabolic labeling to measure protein synthesis; use of virus replication inhibitors\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple conditions tested, replicated by subsequent rhinovirus study; strong functional correlation established\",\n      \"pmids\": [\"9736694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"eIF4GII contains a 29-amino-acid sequence in its N-terminal region that is nearly identical to that of eIF4GI, and the full-length eIF4GII binds poly(A)-binding protein (PABP) via this site (specifically via RRM1 and RRM2 of PABP). This interaction implicates eIF4GII in poly(A)-dependent translation.\",\n      \"method\": \"Co-immunoprecipitation, deletion analysis, in vitro translation assay with deadenylated vs. polyadenylated mRNA\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — co-IP with deletion mapping plus functional in vitro translation assay; strong evidence\",\n      \"pmids\": [\"9857202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"eIF4GII cleavage is the rate-limiting step in the shutoff of host protein synthesis after human rhinovirus 14 (HRV-14) infection. eIF4GI is cleaved early but host translation persists until eIF4GII is substantially cleaved (~6 h post-infection), demonstrating that eIF4GII cleavage correlates with translational inhibition.\",\n      \"method\": \"Western blot analysis of eIF4GI/II cleavage kinetics; metabolic labeling of protein synthesis in HRV-14-infected HeLa cells\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — kinetic correlation established across multiple time points; independent replication of poliovirus findings\",\n      \"pmids\": [\"10074204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mnk1 kinase associates with the eIF4F complex via interaction with the C-terminal region of eIF4G (both eIF4GI and eIF4GII), providing a docking site for Mnk1 to phosphorylate eIF4E at Ser209.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assays, dominant-negative and activated Mnk1 mutants\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP and mutagenesis confirmed interaction; replicated independently\",\n      \"pmids\": [\"9878069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The FMDV IRES interacts with eIF4GII, and the RNA determinants for this interaction are shared with eIF4GI. The C-terminal fragment of eIF4GII generated by Lb protease binds the FMDV IRES as efficiently as intact eIF4GII, indicating the IRES-binding domain resides in the C-terminal portion. eIF4G-IRES interaction is the limiting factor for IRES activity.\",\n      \"method\": \"UV crosslinking, competition experiments, bicistronic reporter assays in transfected cells, protease cleavage\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — crosslinking and competition assays with functional validation, single lab\",\n      \"pmids\": [\"11565745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HIV-1 protease cleaves eIF4GI but not eIF4GII in vitro and in cell extracts, demonstrating differential susceptibility of the two isoforms to this viral protease. Cleavage of eIF4GI by HIV-1 protease impairs both cap-dependent and IRES-containing RNA translation (except HCV IRES), in contrast to picornaviral proteases.\",\n      \"method\": \"In vitro protease assay with cell extracts and rabbit reticulocyte lysate; HIV-1 protease inhibitor (palinavir) as control; in vitro translation assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with inhibitor controls; single lab\",\n      \"pmids\": [\"12054764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HRV2 2A proteinase directly cleaves both eIF4GI and eIF4GII without requiring activation of a cellular proteinase, as demonstrated using a thermosensitive 2Apro mutant in temperature-shift experiments with HeLa cell extracts.\",\n      \"method\": \"Temperature-shift experiments with thermosensitive HRV2 2Apro mutant in cytoplasmic cell extracts; Western blot\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — thermosensitive mutant provides mechanistic discrimination between direct and indirect cleavage\",\n      \"pmids\": [\"12123803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The HRV2 2Apro cleavage site in eIF4GII was identified in vitro as PLLNV(699)*GSR, located seven amino acids C-terminal to the analogous cleavage site in eIF4GI (LSTR681*GPP), demonstrating that the two isoforms have distinct but nearby cleavage sites for the same viral protease.\",\n      \"method\": \"In vitro cleavage assay with recombinant HRV2 2Apro, N-terminal sequencing of cleavage fragments\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biochemical identification of cleavage site by N-terminal sequencing of in vitro cleavage products\",\n      \"pmids\": [\"12663812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"eIF4GII, but not eIF4GI, is selectively recruited to capped mRNA at the onset of erythroid cell differentiation induced by thrombopoietin. This selective recruitment is coincident with strong phosphorylation of eIF4E and release of 4E-BP1 from the cap structure, providing the first evidence that eIF4GI and eIF4GII fulfill distinct roles in mammalian cells.\",\n      \"method\": \"Cap affinity chromatography from differentiating cells, Western blot for eIF4GI/II, 4E-BP1, and phospho-eIF4E\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cap affinity pulldown with differential detection; single lab but clear functional distinction shown\",\n      \"pmids\": [\"15143184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Differential cleavage of eIF4GI and eIF4GII by poliovirus 2Apro revealed functionally distinct roles: de novo translation of newly synthesized mRNA depends primarily on eIF4GI integrity, whereas ongoing translation and reinitiation of pre-existing mRNA translation after polysome run-off are more dependent on eIF4GII. Translation of HSP70 mRNA depends more on eIF4GII than eIF4GI.\",\n      \"method\": \"Electroporation of EMCV IRES-2Apro mRNA into HeLa and BHK-21 cells; luciferase reporter assays; polysome run-off experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — differential cleavage system with multiple reporter assays; single lab\",\n      \"pmids\": [\"16959778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Depletion of eIF4GI or eIF4GII individually only moderately inhibits cellular protein synthesis, while depletion of both together has a slightly greater inhibitory effect. Vaccinia virus (VV) mRNA translation requires eIF4GI/II and eIF4E (cap-dependent), whereas vesicular stomatitis virus (VSV) mRNA translation does not require eIF4GI or eIF4GII despite being capped.\",\n      \"method\": \"siRNA-mediated depletion of eIF4GI and/or eIF4GII in HeLa cells; metabolic labeling; viral protein synthesis assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with multiple viral and cellular translation readouts; single lab\",\n      \"pmids\": [\"19769989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ENU-induced mutation of mouse Eif4g3 (repro8 allele) causes male-limited infertility due to meiotic arrest at the G2/MI transition. EIF4G3 is required for translational control of HSPA2 (a chaperone for CDK1/CDC2A kinase) in spermatocytes: Hspa2 mRNA is present but HSPA2 protein is absent in mutant cells, resulting in dramatically reduced CDK1 kinase activity. This is the first genetic evidence for selective translational control of meiotic exit in mammalian spermatocytes.\",\n      \"method\": \"ENU mutagenesis screen, positional cloning, histology, immunofluorescence, Western blot, kinase activity assay (CDK1), comparison with Hspa2 knockout phenotype\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with defined molecular target (HSPA2 translation), multiple orthogonal readouts, phenotype mimics Hspa2 KO\",\n      \"pmids\": [\"20430745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Both eIF4GI and eIF4GII are cleaved in Jurkat T cells in response to proteasome inhibitors (MG132, lactacystin) and immunosuppressants (FTY720, cyclosporin A) by caspase-8-independent mechanisms. Proteasome inhibitor-induced cleavage of eIF4GI generates a novel fragment lacking the eIF4E-binding capability, distinct from the anti-Fas-induced cleavage pattern.\",\n      \"method\": \"Western blot with anti-peptide antisera specific for eIF4GI and eIF4GII; caspase-8-deficient Jurkat cell line; pharmacological inhibitors\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — isogenic caspase-8-deficient cell line used for mechanistic dissection; multiple agents tested\",\n      \"pmids\": [\"11513883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CaMKI phosphorylates eIF4GII at Ser1156 in an activity-dependent manner in hippocampal neurons. This phosphorylation promotes selective recruitment of eIF4GII (but not eIF4GI) into the eIF4F complex assembled at the mRNA 5' cap, upregulating cap-dependent translation. RNAi knockdown of eIF4GII reduces cap-dependent translation and decreases density of dendritic filopodia and spine formation without affecting dendritic arborization.\",\n      \"method\": \"In vitro CaMKI phosphorylation assay, m7GTP cap affinity purification, bicistronic luciferase reporter, RNAi knockdown in hippocampal neurons, confocal imaging of spine morphology, pharmacological inhibition (STO-609, NMDA receptor blockers)\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro kinase assay with site-specific mutant (S1156A), cap pulldown, functional reporters, and morphological phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"22514323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"DEAF1 transcriptionally regulates Eif4g3 expression in lymph node stromal cells (LNSCs). Reduced DEAF1 function (in Deaf1-KO mice, NOD mice, and T1D patients) leads to decreased Eif4g3 transcription and also increased Caspase 3 expression (which degrades eIF4GII protein). Polysome profiling showed that reduced eIF4GII in LNSCs diminishes translation of multiple genes including Anpep.\",\n      \"method\": \"qRT-PCR, siRNA silencing of Deaf1, polysome profiling, Western blot, comparison across Deaf1-KO mice, NOD mice, and T1D patient samples\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple model systems and polysome profiling; single lab\",\n      \"pmids\": [\"22923498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Multiple isoforms of eIF4GII are generated in mammalian cells via alternative promoters, alternative splicing, and use of a non-canonical CUG initiation codon that extends the N-terminus. The novel N-terminal-extended eIF4GII isoforms rescue translation in eIF4GI/eIF4GII double-knockdown cells as effectively as the eIF4GIf/e isoforms, more robustly than the original eIF4GII, suggesting the eIF4GII N-terminus has a role distinct from eIF4GI in translation initiation factor assembly.\",\n      \"method\": \"RT-PCR, 5' RACE, RNAi knockdown, rescue experiments with overexpression of isoforms, metabolic labeling of translation rates\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — isoform identification combined with functional rescue assays; single lab\",\n      \"pmids\": [\"22909319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"eIF4GII undergoes novel Cdk1-dependent N-terminal phosphorylation in nocodazole-arrested cells. This phosphorylation, along with eIF2α phosphorylation and polysome disaggregation, contributes to the inhibition of translation observed in nocodazole-arrested cells, which had previously been attributed to mitosis itself. Translation rates do not intrinsically slow during mitosis when cells are synchronized without nocodazole.\",\n      \"method\": \"FACS-synchronized HeLa cells (double thymidine block or RO3306 release), pulse labeling with [35S]-methionine, confocal microscopy of translation factors, polysome analysis, phosphorylation analysis by Western blot\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple synchronization strategies tested with metabolic labeling; single lab but mechanistic reinterpretation supported by multiple approaches\",\n      \"pmids\": [\"24091728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"miR-520c-3p directly targets eIF4GII (EIF4G3) mRNA, repressing its translation. Downregulation of eIF4GII by either miR-520c-3p or siRNA decreases global translation, reduces cell proliferation, promotes cellular senescence, and suppresses tumor growth in xenograft models of diffuse large B-cell lymphoma.\",\n      \"method\": \"miRNA overexpression, siRNA knockdown, luciferase reporter assays (3'UTR targeting), xenograft tumor assay, Western blot, proliferation assays\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct target validation by reporter assay combined with in vivo xenograft and in vitro phenotyping; single lab\",\n      \"pmids\": [\"24497838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"EIF4G3 localizes unexpectedly to the nucleus of mouse spermatocytes, with high enrichment in the XY body (the chromatin domain of transcriptionally silenced sex chromosomes). Many other translation-related proteins also localize to the XY body, suggesting a role for this domain in storing or poising translation complexes before the meiotic division phase.\",\n      \"method\": \"Immunofluorescence, confocal microscopy, subcellular fractionation, co-localization with XY body markers (γH2AX, BRCA1)\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct localization by immunofluorescence with functional inference; novel finding but functional consequence not fully established\",\n      \"pmids\": [\"29161344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"EIF4G3 is a direct target of miR-375 in lung squamous cell carcinoma cells. Chidamide treatment upregulates miR-375, which suppresses EIF4G3 mRNA and protein expression. Silencing EIF4G3 independently induces apoptosis and suppresses tumor growth, while inhibition of miR-375 reverses chidamide-induced apoptosis and stemness suppression, confirming EIF4G3 as a functional mediator of the chidamide/radiation response.\",\n      \"method\": \"miRNA microarray, luciferase reporter assay (direct miR-375 target validation), Western blot, siRNA knockdown of EIF4G3, xenograft tumor assay\",\n      \"journal\": \"Journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct target validation by reporter assay with functional rescue; single lab\",\n      \"pmids\": [\"34194495\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"EIF4G3 (eIF4GII) is a scaffold protein of the eIF4F translation initiation complex that directly binds eIF4E, eIF4A, eIF3, and PABP to mediate cap-dependent and poly(A)-dependent translation; it is differentially regulated from its paralog eIF4GI through selective recruitment during cell differentiation, CaMKI-mediated phosphorylation at Ser1156 to enhance neuronal cap-dependent translation, Cdk1-dependent phosphorylation during mitosis, transcriptional control by DEAF1, and post-transcriptional repression by miR-520c-3p and miR-375; it is cleaved by picornaviral 2A proteases (at PLLNV699*GSR in eIF4GII) to shut off host translation, and is genetically required in mouse spermatocytes for HSPA2 translation and meiotic exit, where it also localizes to the nuclear XY body.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"EIF4G3 (eIF4GII) is a scaffold subunit of the eIF4F translation initiation complex that bridges cap-bound eIF4E and ribosome-recruiting eIF3, with functionally distinct roles from its paralog eIF4GI in selective mRNA translation during differentiation, stress, and meiosis. EIF4G3 is preferentially recruited to capped mRNA during erythroid differentiation and neuronal activity—the latter regulated by CaMKI phosphorylation at Ser1156—and is specifically required for translational control of HSPA2 in spermatocytes, where its loss causes meiotic arrest at the G2/MI transition due to diminished CDK1 activity [PMID:15143184, PMID:22514323, PMID:20430745]. Picornaviral 2A proteases directly cleave EIF4G3 at a site (PLLNV699*GSR) distinct from the eIF4GI cleavage site, and cleavage of both isoforms is required for complete host translation shutoff; EIF4G3 is notably resistant to HIV-1 protease, further distinguishing it from eIF4GI [PMID:9736694, PMID:12663812, PMID:12054764]. In spermatocytes, EIF4G3 localizes to the nucleus and is enriched in the XY body, and during mitosis it undergoes Cdk1-dependent phosphorylation and localizes to the mitotic spindle and midbody [PMID:29161344, PMID:24091728].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that eIF4GII is a second, functionally important eIF4F scaffold whose cleavage—along with eIF4GI—is required for complete picornaviral shutoff of host translation resolved why eIF4GI cleavage alone was insufficient to inhibit cap-dependent translation.\",\n      \"evidence\": \"Western blot and pulse-labeling kinetics in poliovirus-infected HeLa cells with virus replication inhibitors\",\n      \"pmids\": [\"9736694\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of eIF4GI vs eIF4GII to basal translation not quantified\", \"No structural model of eIF4GII at this stage\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrating that eIF4GII cleavage is the rate-limiting step for host translation shutoff during rhinovirus infection established eIF4GII as the kinetically dominant target in picornaviral translational inhibition.\",\n      \"evidence\": \"Kinetic Western blot and pulse-labeling in HRV-14-infected HeLa cells\",\n      \"pmids\": [\"10074204\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether rate-limiting cleavage generalizes beyond rhinovirus was unclear\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showing that eIF4GII binds FMDV IRES via the same RNA determinants as eIF4GI, and that its C-terminal cleavage fragment retains IRES-binding activity, established that viral IRES elements can co-opt both eIF4G isoforms.\",\n      \"evidence\": \"UV crosslinking and competition RNA-protein interaction assays with FMDV IRES\",\n      \"pmids\": [\"11565745\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of eIF4GII fragment-IRES binding on viral translation not directly measured\", \"Only FMDV IRES tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The finding that HIV-1 protease cleaves eIF4GI but not eIF4GII revealed isoform-specific protease susceptibility and explained why HIV-1 does not fully shut off host translation in the manner of picornaviruses.\",\n      \"evidence\": \"In vitro protease cleavage assay with reticulocyte lysate and HIV-1 protease inhibitor control\",\n      \"pmids\": [\"12054764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance during HIV-1 infection not demonstrated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapping the precise 2Apro cleavage site in eIF4GII (PLLNV699*GSR) revealed it lies seven residues C-terminal to the eIF4GI site, defining the molecular basis for isoform-specific cleavage kinetics.\",\n      \"evidence\": \"In vitro cleavage with purified 2Apro and N-terminal sequencing of products\",\n      \"pmids\": [\"12663812\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the shifted cleavage site explains slower eIF4GII cleavage kinetics was not mechanistically resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Selective recruitment of eIF4GII—but not eIF4GI—to the cap structure upon cytokine-driven erythroid differentiation established that the two isoforms are differentially regulated and have non-redundant roles in cell fate transitions.\",\n      \"evidence\": \"m7GTP-Sepharose pulldown and Western blot in thrombopoietin-stimulated differentiating cells\",\n      \"pmids\": [\"15143184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis for selective eIF4GII recruitment over eIF4GI unknown\", \"Target mRNAs selectively translated by eIF4GII in differentiation not identified\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that eIF4GII is specifically required for reinitiation of translation on preexisting mRNAs (including HSP70) after polysome run-off, while eIF4GI supports de novo translation, defined complementary but non-redundant functions for the two isoforms.\",\n      \"evidence\": \"Differential cleavage via 2Apro electroporation and luciferase reporter assays in BHK-21 and HeLa cells\",\n      \"pmids\": [\"16959778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether reinitiation selectivity reflects direct mRNA preference or kinetic availability of eIF4GII not resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Genetic loss-of-function in mice revealed that Eif4g3 is essential for spermatocyte meiotic exit by controlling translation of HSPA2, a chaperone for CDK1, providing the first in vivo evidence of eIF4GII-specific translational selectivity for a defined mRNA target.\",\n      \"evidence\": \"ENU-induced repro8 mutation, genetic epistasis with Hspa2 KO, polysome profiling, CDK1 kinase assay in mouse spermatocytes\",\n      \"pmids\": [\"20430745\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How eIF4GII selectively recognizes HSPA2 mRNA is mechanistically undefined\", \"Whether other meiotic mRNAs depend on eIF4GII is unexplored\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Multiple converging studies in 2012 established that eIF4GII exists as multiple isoforms with distinct translational capacities, is transcriptionally regulated by DEAF1, and is phosphorylated by CaMKI at Ser1156 in neurons to control activity-dependent cap-complex assembly and dendritic spine morphogenesis—broadening its roles beyond viral biology to neuronal plasticity and transcriptional regulation.\",\n      \"evidence\": \"In vitro CaMKI kinase assay, S1156A mutagenesis, cap pulldown and siRNA in hippocampal neurons (PMID:22514323); isoform cloning and double-knockdown rescue (PMID:22909319); polysome profiling after Deaf1 knockdown (PMID:22923498)\",\n      \"pmids\": [\"22514323\", \"22909319\", \"22923498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream mRNA targets of CaMKI-activated eIF4GII in neurons not identified\", \"Functional significance of individual isoforms in vivo unknown\", \"DEAF1 regulation of Eif4g3 demonstrated only in lymph node stromal cells\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Cdk1-dependent phosphorylation and localization of eIF4GII to the mitotic spindle and midbody established a mitotic role, suggesting localized translation at these structures.\",\n      \"evidence\": \"Confocal microscopy and phosphorylation analysis in nocodazole-arrested synchronized HeLa cells\",\n      \"pmids\": [\"24091728\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of mitotic phosphorylation on eIF4GII activity not tested\", \"Whether localized translation at the midbody depends on eIF4GII is not demonstrated\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of miR-520c-3p as a direct negative regulator of EIF4G3 mRNA, with eIF4GII knockdown reducing global translation and inducing senescence, linked eIF4GII dosage to proliferative capacity and tumor biology.\",\n      \"evidence\": \"miRNA overexpression, luciferase reporter validation, siRNA knockdown, xenograft model\",\n      \"pmids\": [\"24497838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-520c-3p regulation of eIF4GII is relevant in non-tumor contexts unclear\", \"Senescence mechanism downstream of eIF4GII depletion not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Nuclear localization of eIF4GII in spermatocytes, with enrichment in the transcriptionally silent XY body, suggested an unexpected non-cytoplasmic function in mRNA metabolism or translational poising during meiotic prophase.\",\n      \"evidence\": \"Immunofluorescence and subcellular fractionation in mouse spermatocytes\",\n      \"pmids\": [\"29161344\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Function of eIF4GII in the XY body is unknown\", \"Whether nuclear localization involves RNA binding or a non-canonical role is untested\", \"No interacting partners in the nucleus identified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular basis by which eIF4GII selectively recognizes specific mRNAs (e.g., HSPA2) over eIF4GI, and the functional significance of its nuclear localization in spermatocytes, remain major unresolved questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of eIF4GII explaining isoform-specific mRNA selectivity\", \"Nuclear function and interactome of eIF4GII in spermatocytes uncharacterized\", \"Comprehensive identification of eIF4GII-dependent translatome in any cell type is lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 8, 9]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [7, 8, 9, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 6, 9]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 7, 8, 9, 11]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [8, 12]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [8, 14]}\n    ],\n    \"complexes\": [\n      \"eIF4F\"\n    ],\n    \"partners\": [\n      \"EIF4E\",\n      \"EIF3\",\n      \"CAMK1\",\n      \"CDK1\",\n      \"HSPA2\",\n      \"DEAF1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"EIF4G3 (eIF4GII) is a scaffold subunit of the eIF4F translation initiation complex that bridges cap-bound eIF4E, the RNA helicase eIF4A, the 40S-recruiting factor eIF3, the poly(A)-binding protein PABP, and the eIF4E kinase Mnk1, thereby coupling 5′-cap recognition and 3′-poly(A) tail circularization to ribosome loading [PMID:9418880, PMID:9857202, PMID:9878069]. Although broadly redundant with its paralog eIF4GI for bulk translation, eIF4GII is selectively recruited to the cap during erythroid differentiation, is phosphorylated by CaMKI at Ser1156 to promote cap-dependent translation and dendritic spine formation in hippocampal neurons, and is genetically required in mouse spermatocytes for translational activation of HSPA2 mRNA and completion of meiosis [PMID:15143184, PMID:22514323, PMID:20430745]. Picornaviral 2A proteases cleave eIF4GII at a specific site (PLLNV699↓GSR), and its delayed cleavage relative to eIF4GI is rate-limiting for host translation shutoff during rhinovirus infection [PMID:12663812, PMID:10074204]. EIF4G3 expression is transcriptionally controlled by DEAF1 and post-transcriptionally repressed by miR-520c-3p and miR-375; its downregulation reduces global translation, promotes senescence, and suppresses tumor xenograft growth [PMID:22923498, PMID:24497838, PMID:34194495].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Identification of eIF4GII as a second mammalian eIF4G isoform established that the eIF4F scaffold function is shared between two paralogs capable of independently assembling the cap-binding complex with eIF4E, eIF4A, eIF3, and PABP.\",\n      \"evidence\": \"Far-Western, co-IP, cap affinity chromatography, in vitro translation rescue in HeLa cells and reticulocyte lysate; PABP interaction mapped via deletion analysis\",\n      \"pmids\": [\"9418880\", \"9857202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether eIF4GI and eIF4GII have distinct mRNA-selective roles was unknown\",\n        \"Structural basis of eIF4GII scaffold assembly not determined\"\n      ]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Kinetic studies of picornavirus infections revealed that eIF4GII cleavage—not eIF4GI cleavage—is the rate-limiting step for host translation shutoff, demonstrating that eIF4GII alone can sustain cap-dependent translation.\",\n      \"evidence\": \"Western blot kinetics of eIF4GI/II cleavage correlated with metabolic labeling during poliovirus and HRV-14 infection of HeLa cells\",\n      \"pmids\": [\"9736694\", \"10074204\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Exact cleavage site in eIF4GII was not yet mapped\",\n        \"Whether eIF4GII resistance reflects sequence divergence or structural protection was unclear\"\n      ]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstration that Mnk1 docks on the C-terminus of both eIF4GI and eIF4GII to phosphorylate eIF4E positioned the eIF4G scaffold as a signaling platform integrating MAPK/p38 input into translation.\",\n      \"evidence\": \"Co-IP with dominant-negative and activated Mnk1 mutants\",\n      \"pmids\": [\"9878069\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether Mnk1 preferentially utilizes eIF4GII versus eIF4GI in specific contexts was not tested\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Biochemical identification of the HRV2 2Apro cleavage site at PLLNV699↓GSR in eIF4GII resolved the molecular basis of differential protease sensitivity between the two paralogs.\",\n      \"evidence\": \"In vitro cleavage with recombinant 2Apro followed by N-terminal sequencing of cleavage fragments\",\n      \"pmids\": [\"12663812\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural determinants governing slower cleavage kinetics of eIF4GII versus eIF4GI not resolved\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Selective recruitment of eIF4GII, but not eIF4GI, to the cap structure during thrombopoietin-induced erythroid differentiation provided the first evidence that the two paralogs fulfill non-redundant physiological roles.\",\n      \"evidence\": \"Cap affinity chromatography from differentiating UT-7 cells with Western blot for eIF4GI/II and 4E-BP1\",\n      \"pmids\": [\"15143184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular basis of selective eIF4GII recruitment unknown\",\n        \"Target mRNAs preferentially translated by eIF4GII in this context not identified\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Differential cleavage experiments revealed that eIF4GII is preferentially required for ongoing/reinitiation translation of pre-existing mRNAs (including HSP70), whereas eIF4GI supports de novo translation of newly exported mRNAs.\",\n      \"evidence\": \"Electroporation of EMCV-IRES-2Apro mRNA into HeLa and BHK-21 cells with luciferase reporters and polysome run-off\",\n      \"pmids\": [\"16959778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Genome-wide identification of eIF4GII-dependent mRNAs not performed\",\n        \"Whether this division of labor holds outside picornavirus-cleavage conditions is unknown\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Genetic loss of Eif4g3 in mouse spermatocytes caused meiotic arrest at G2/MI by failing to translate HSPA2, a chaperone required for CDK1 activation, establishing eIF4GII as an essential translational regulator of mammalian meiosis.\",\n      \"evidence\": \"ENU mutagenesis (repro8 allele), positional cloning, histology, immunofluorescence, Western blot, CDK1 kinase assay in mouse testis\",\n      \"pmids\": [\"20430745\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether eIF4GII recognizes specific cis-elements in Hspa2 mRNA is unknown\",\n        \"Full spectrum of eIF4GII-dependent mRNAs in spermatocytes not catalogued\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"CaMKI-mediated phosphorylation of eIF4GII at Ser1156 in hippocampal neurons was shown to enhance eIF4GII recruitment to the cap and promote dendritic spine formation, linking activity-dependent signaling to selective eIF4GII-driven translation in neurons.\",\n      \"evidence\": \"In vitro kinase assay with S1156A mutant, cap affinity purification, bicistronic reporter, RNAi knockdown with confocal spine imaging in hippocampal neurons\",\n      \"pmids\": [\"22514323\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Neuronal mRNAs selectively translated via phospho-S1156 eIF4GII not identified\",\n        \"Whether this phosphorylation event is relevant in vivo (learning/memory paradigms) is untested\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Parallel studies revealed that eIF4GII expression is transcriptionally regulated by DEAF1 in lymph node stromal cells and that multiple N-terminally extended eIF4GII isoforms generated from alternative promoters and a CUG start codon have distinct translational rescue activities.\",\n      \"evidence\": \"qRT-PCR, siRNA, polysome profiling in LNSCs; 5′-RACE, isoform overexpression rescue of double-knockdown cells with metabolic labeling\",\n      \"pmids\": [\"22923498\", \"22909319\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Physiological significance of individual N-terminal isoforms in specific tissues not established\",\n        \"Whether DEAF1-dependent regulation of eIF4GII contributes to autoimmune phenotypes remains correlative\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Post-transcriptional repression of EIF4G3 by miR-520c-3p was shown to reduce global translation, promote senescence, and suppress lymphoma xenograft growth, implicating eIF4GII as a rate-limiting translation factor for cell proliferation.\",\n      \"evidence\": \"3′-UTR luciferase reporter, siRNA knockdown, xenograft tumor assay in diffuse large B-cell lymphoma model\",\n      \"pmids\": [\"24497838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether eIF4GII loss triggers senescence through a specific mRNA target or globally reduced translation is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Unexpected nuclear localization of EIF4G3 in mouse spermatocytes, particularly at the XY body, raised the possibility that eIF4GII has non-cytoplasmic roles during meiotic prophase.\",\n      \"evidence\": \"Immunofluorescence with confocal microscopy and co-localization with γH2AX and BRCA1 in mouse spermatocyte spreads\",\n      \"pmids\": [\"29161344\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional significance of XY body localization not demonstrated\",\n        \"Whether nuclear eIF4GII has any translation-independent function is unknown\",\n        \"Biochemical validation of nuclear localization (fractionation controls) limited\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mRNA-selective mechanism by which eIF4GII controls translation of specific targets (e.g. HSPA2, dendritic mRNAs) remains undefined—no cis-regulatory elements, RNA-binding partners, or structural features distinguishing eIF4GII from eIF4GI target selection have been identified.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No genome-wide identification of eIF4GII-dependent translatome in any tissue\",\n        \"No high-resolution structure of eIF4GII or eIF4GII-specific domains\",\n        \"Mechanism of isoform-selective cap recruitment is unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [0, 9, 10, 12, 14]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 9, 14]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 9, 10, 12, 14, 16]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 3, 6, 7, 8]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [12, 19]}\n    ],\n    \"complexes\": [\n      \"eIF4F\"\n    ],\n    \"partners\": [\n      \"EIF4E\",\n      \"EIF4A1\",\n      \"EIF3A\",\n      \"PABPC1\",\n      \"MKNK1\",\n      \"CAMK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}