{"gene":"EIF4E2","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":1998,"finding":"4EHP (EIF4E2) was cloned and characterized as a novel cap-binding protein with 30% identity to eIF4E. It binds specifically to capped RNA in an ATP- and divalent ion-independent manner. Homology modeling and site-directed mutagenesis strongly suggest it shares with eIF4E a common mechanism for cap binding, but unlike eIF4E, 4EHP does not interact with eIF4G and therefore cannot stimulate translation.","method":"Biochemical cap-binding assay, homology modeling, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro cap-binding assay combined with site-directed mutagenesis, foundational characterization paper replicated in subsequent studies","pmids":["9582349"],"is_preprint":false},{"year":2005,"finding":"Drosophila 4EHP (d4EHP) specifically interacts with Bicoid (Bcd) protein to suppress caudal (cad) mRNA translation. d4EHP binds the 5' cap structure while Bcd simultaneously binds the Bicoid binding region (BBR) in the cad 3'UTR, effectively tethering the 5' and 3' ends of cad mRNA to render it translationally inactive. This defines a new paradigm for cap-dependent translational inhibition not mediated by canonical eIF4E.","method":"Genetic and biochemical assays in Drosophila embryos, cap-binding assays, interaction assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution of translational repression with defined molecular interactions, multiple orthogonal methods, seminal paper subsequently replicated across labs","pmids":["15882623"],"is_preprint":false},{"year":2007,"finding":"4EHP binds cap analogs m7GpppG and m7GTP with 30- and 100-fold lower affinity than eIF4E, respectively, as measured by fluorescence titration and stopped-flow measurements. This low binding affinity explains why 4EHP cannot compete with eIF4E for the cap of most mRNAs and thus does not inhibit general translation.","method":"Fluorescence titration, stopped-flow kinetic measurements","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — two orthogonal quantitative biophysical methods in a single focused study establishing cap-binding affinity differences","pmids":["17369309"],"is_preprint":false},{"year":2007,"finding":"4EHP is modified by ISG15 (ISGylation), and ISGylated 4EHP has significantly higher cap structure-binding activity than unmodified 4EHP. ISGylation of 4EHP is activated by interferon, genotoxic stress, and pathogen infection.","method":"ISGylation assay, cap-binding activity assay comparing modified vs. unmodified 4EHP","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical modification assay with functional readout (cap-binding enhancement), single lab but two orthogonal methods","pmids":["17289916"],"is_preprint":false},{"year":2003,"finding":"HHARI (human homologue of ariadne) interacts with 4EHP via its N-terminal RING1 finger. Overexpression of 4EHP and HHARI in mammalian cells leads to polyubiquitylation of 4EHP, suggesting HHARI promotes ubiquitin-mediated degradation of 4EHP. HHARI, 4EHP, and UbcH7 do not form a stable heterotrimeric complex as 4EHP cannot immunoprecipitate UbcH7 even in the presence of HHARI.","method":"Co-immunoprecipitation, overexpression-based ubiquitylation assay in mammalian cells","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP and ubiquitylation assay, single lab, two complementary methods","pmids":["14623119"],"is_preprint":false},{"year":2004,"finding":"4E-BP1 binds to 4EHP via the same interface used for eIF4E binding; eIF4E-binding mutants of 4E-BP1 (Y54A and L59A) fail to form complexes with 4EHP, and the W95A mutant of 4EHP inhibits its binding to 4E-BP1. Overexpression of 4EHP triggers a negative feedback loop inhibiting upstream signaling to 4E-BP1 and S6K1, dependent on the 4E-BP1 binding interaction.","method":"Co-immunoprecipitation, site-directed mutagenesis, overexpression with signaling readouts","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis combined with co-IP and signaling assay, single lab, multiple approaches","pmids":["15094042"],"is_preprint":false},{"year":2009,"finding":"Mammalian 4EHP co-localizes and interacts with the homeodomain transcription factor Prep1 in the cytosol of mouse oocytes. Prep1 contains a functional 4EHP-binding motif (identified by mutagenesis). Prep1 inhibits (>95%) in vitro translation of a luciferase reporter fused to the Hoxb4 3'UTR in the presence of 4EHP, and Prep1 binds the Hoxb4 3'UTR directly (EMSA), suggesting a 5'-3' mRNA tethering mechanism.","method":"Confocal microscopy, co-immunoprecipitation, pull-down, site-directed mutagenesis of binding motif, in vitro translation assay, RNA EMSA","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, in vitro translation, EMSA) in a single lab","pmids":["19365557"],"is_preprint":false},{"year":2012,"finding":"Mammalian 4EHP forms a complex with GIGYF2 and ZNF598. GIGYF2 directly interacts with 4EHP, and this interaction is required for stabilization of both proteins. Disruption of the m4EHP-GIGYF2 complex leads to increased translation and perinatal lethality in mice, establishing the complex as a physiologically essential translational repressor.","method":"Co-immunoprecipitation, mass spectrometry, mouse knockout/genetic disruption with translational and developmental phenotype readouts","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, MS identification of complex, in vivo genetic disruption with defined molecular and developmental phenotype","pmids":["22751931"],"is_preprint":false},{"year":2015,"finding":"Upon DNA damage, ARIH1 E3 ubiquitin ligase associates with 4EHP and promotes its non-degradative ubiquitination. This leads to enrichment of ARIH1 in perinuclear ribosome-containing regions and 4EHP association with the mRNA 5' cap, triggering mRNA translation arrest in an ARIH1-dependent manner. Restoration of translation arrest in ARIH1-depleted cells via an eIF2 inhibitor was sufficient to reinstate resistance to genotoxic stress.","method":"RNAi screen, co-immunoprecipitation, ubiquitination assay, cap-binding assay, polysome profiling, epistasis rescue experiment","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical assays and epistasis, single lab","pmids":["25624349"],"is_preprint":false},{"year":2016,"finding":"The 4EHP-GYF2 (GIGYF2) complex acts as a cofactor of tristetraprolin (TTP) for translational repression and mRNA decay of AU-rich element (ARE)-containing mRNAs. TTP directly interacts with GIGYF2 via conserved tetraproline motifs. Mutant TTP with diminished 4EHP-GYF2 binding is impaired in repressing ARE-mRNAs, and 4EHP knockout MEFs show increased induction and slower turnover of TTP-target mRNAs.","method":"Co-immunoprecipitation, in vitro pull-down, mutational analysis, luciferase reporter assay, 4EHP knockout MEFs","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, in vitro pull-down, mutagenesis, reporter assay, and knockout cell lines across multiple orthogonal approaches","pmids":["26763119"],"is_preprint":false},{"year":2017,"finding":"Crystal structures of the 4EHP-binding regions of GIGYF1 and GIGYF2 in complex with 4EHP reveal the molecular basis for selective binding of GIGYF1/2 to 4EHP but not eIF4E. Structure-guided mutants in complementation assays in GIGYF1/2-null cells demonstrate that 4EHP requires interactions with GIGYF1/2 for repressive activity on target mRNAs.","method":"X-ray crystallography, structure-based mutagenesis, complementation assay in knockout cell line","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with structure-based mutagenesis and functional complementation assay","pmids":["28698298"],"is_preprint":false},{"year":2017,"finding":"4EHP is an integral component of the miRNA-mediated silencing machinery. 4EHP cap-binding activity contributes to translational silencing by miRNAs through the CCR4-NOT complex. 4EHP competes with eIF4E for binding to 4E-T, and this interaction increases 4EHP's affinity for the cap. A closed-loop mRNA conformation via the 4E-T/4EHP interaction is proposed to block translational initiation of miRNA targets.","method":"Co-immunoprecipitation, cap-binding assay, reporter assay (tethering and miRNA-mediated silencing), loss-of-function experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, cap-binding, reporter assays, knockdown) across different experimental contexts","pmids":["28487484"],"is_preprint":false},{"year":2017,"finding":"TNRC6A (a GW182 family protein) interacts with 4EHP/EIF4E2 to inhibit translation of miRNA target mRNAs. Downregulation of 4EHP/EIF4E2 relieved miRNA repression of reporter constructs and increased protein levels of endogenous miRNA targets (IMP1, PTEN, PDCD4). miRNA enhances 4EHP association with target mRNA.","method":"Co-immunoprecipitation, reporter assay, siRNA knockdown, endogenous protein level analysis","journal":"Protein & cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus functional reporter assays and endogenous target validation, single lab","pmids":["28755203"],"is_preprint":false},{"year":2018,"finding":"4EHP translationally represses Dusp6 mRNA (encoding ERK phosphatase) via miR-145, promoting ERK1/2 phosphorylation, augmented cell growth, and reduced apoptosis. Ribosome profiling identified a subset of mRNAs translationally controlled by 4EHP, placing 4EHP/miRISC in the ERK signaling cascade.","method":"Ribosome profiling, reporter assay, western blot for ERK phosphorylation, 4EHP knockout/knockdown with cellular phenotype readouts","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — ribosome profiling combined with reporter assay, signaling readout, and knockout validation, multiple orthogonal approaches","pmids":["29412140"],"is_preprint":false},{"year":2018,"finding":"GIGYF2 has two distinct mechanisms of mRNA repression: one depends on 4EHP binding and mainly affects translation; the other is 4EHP-independent and involves recruitment of the CCR4/NOT complex through multiple interfaces leading to deadenylation. Three independent domains of GIGYF2 have repressive activity in tethering reporter assays. GIGYF2 is an RNA-binding protein with identifiable endogenous mRNA targets.","method":"Tethering reporter assay, domain mutagenesis, co-immunoprecipitation, RNA-binding protein assay, endogenous mRNA target identification","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple domains tested by mutagenesis combined with reporter assays and co-IP, single lab","pmids":["29554310"],"is_preprint":false},{"year":2013,"finding":"Human 4EHP/eIF4E2 binds 4E-T via the canonical YX4Lφ sequence, and this interaction recruits 4EHP to P-bodies in mammalian cells. 4EHP does not redistribute to stress granules in arsenite-treated cells or to P-bodies in Actinomycin D-treated cells (unlike eIF4E1). 4EHP shuttles through the nucleus in a Crm1-dependent but 4E-T-independent manner.","method":"Yeast two-hybrid, pull-down assay, indirect immunofluorescence, cellular fractionation, drug treatment (leptomycin B for Crm1 inhibition)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple localization methods (immunofluorescence, Y2H, pull-down) in a single lab; localization tied to functional context","pmids":["23991149"],"is_preprint":false},{"year":2014,"finding":"eIF4E2 is activated under hypoxia to drive cap-dependent translation of a subset of mRNAs in cancer cells. eIF4E2-depleted cancer cells cannot survive or proliferate in low oxygen, cannot form a hypoxic tumor core in spheroids, and fail to form tumors in xenograft assays, whereas they are indistinguishable from controls under normoxia.","method":"siRNA knockdown, in vitro spheroid assay, in vivo xenograft assay, polysome profiling under hypoxia","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with defined molecular mechanism in both in vitro and in vivo models, multiple complementary assays","pmids":["24408918"],"is_preprint":false},{"year":2019,"finding":"Drosophila GIGYF, when in complex with 4EHP, elicits both translational repression and mRNA decay via recruitment of Me31B/DDX6 (RNA helicase), HPat (decapping activator), and the CCR4-NOT deadenylase complex. Discrete binding motifs in GIGYF conserved among metazoan GIGYF proteins are required for Me31B and HPat recruitment and for downregulation of mRNA expression.","method":"Co-immunoprecipitation, tethering reporter assay, mutagenesis of binding motifs, mRNA decay assay","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus mutagenesis and reporter assay, single lab with multiple orthogonal approaches","pmids":["31114929"],"is_preprint":false},{"year":2019,"finding":"Crystal structure (2.4 Å) of the GIGYF-Me31B/DDX6 complex reveals that the GIGYF motif arranges into a coil connected to a β hairpin, binding conserved hydrophobic patches on the Me31B RecA2 domain. Structure-guided mutants confirm that 4EHP-GIGYF-DDX6 complex assembly is required for tristetraprolin-mediated down-regulation of an AU-rich mRNA.","method":"X-ray crystallography (2.4 Å), structure-based mutagenesis, mRNA reporter assay","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure combined with structure-based mutagenesis and functional assay","pmids":["31439631"],"is_preprint":false},{"year":2020,"finding":"4EHP and GIGYF2 form a negative feedback loop that inhibits translation initiation on mRNAs that have undergone failed translation (ribosome-associated quality control). CRISPR-Cas9 screens identified GIGYF2 and 4EHP as mediators of this feedback; loss of these factors leads to accumulation of partially synthesized toxic polypeptides from defective mRNAs.","method":"CRISPR-Cas9-based genetic screen, model substrate assays, growth-based assays, translation initiation assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide CRISPR screen followed by mechanistic validation with model substrates and growth assays","pmids":["32726578"],"is_preprint":false},{"year":2020,"finding":"4EHP-GIGYF1/2 complexes trigger co-translational mRNA decay. Human cells lacking these proteins accumulate mRNAs with ribosome pausing, including transcripts encoding secretory/membrane proteins and tubulin. 4EHP-GIGYF1/2-mediated mRNA decay requires cap structure interaction, DDX6 interaction, ZNF598 interaction, and is dependent on ribosome stalling; GIGYF1/2 co-translational binding marks transcripts with perturbed elongation for decay.","method":"Ribosome profiling, mRNA stability assay, co-immunoprecipitation, knockout cell lines","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — ribosome profiling combined with knockout cell lines and multiple interaction/functional assays","pmids":["33053355"],"is_preprint":false},{"year":2021,"finding":"4EHP suppresses IFN-β production by mediating miR-34a-induced translational silencing of Ifnb1 mRNA. miR-34a is upregulated by RNA virus infection and IFN-β, creating a negative feedback loop that represses IFN-β expression via 4EHP. 4EHP knockout mice show elevated IFN-β and altered virus replication, establishing an in vivo role for 4EHP in antiviral immunity.","method":"4EHP knockout mice, reporter assay, polysome profiling, in vivo viral infection, cytokine measurement","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout with defined molecular mechanism (miR-34a/Ifnb1 axis), multiple orthogonal methods including viral infection models","pmids":["33581076"],"is_preprint":false},{"year":2022,"finding":"METTL16 interacts with 4EHP/eIF4E2 in the cytoplasm. This interaction impedes the recruitment of 4EHP to the 5' cap structure, thereby promoting cap recognition by eIF4E and selective protein synthesis. METTL16 depletion attenuates protein synthesis, and this effect is mediated through 4EHP, not METTL16's methyltransferase activity.","method":"Co-immunoprecipitation, cap-binding assay, translation reporter assay, METTL16 depletion/overexpression with polysome analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with functional cap-binding and translation assays, single lab with multiple orthogonal approaches","pmids":["36840945"],"is_preprint":false},{"year":2022,"finding":"4EHP/eIF4E2 interacts with GSK3β and maintains basal proline-directed serine/threonine (S/T-P) phosphorylation of p53 and other targets, thereby resisting cellular senescence under hypoxia. Peptides blocking the eIF4E2-GSK3β interaction inhibit S/T-P phosphorylation and induce senescence. Hypoxia inhibits this pathway through S-nitrosylation of GSK3β.","method":"Co-immunoprecipitation, kinase activity assay, peptide inhibition, senescence assays, in vivo mouse liver model, S-nitrosylation assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP combined with functional kinase assay and multiple cellular/in vivo readouts, single lab","pmids":["35568694"],"is_preprint":false},{"year":2022,"finding":"SARS-CoV-2 NSP2 physically associates with both 4EHP and GIGYF2 (binding a central segment of GIGYF2) in the cytoplasm, and impairs GIGYF2-mediated translation repression as shown by reporter-based assays.","method":"In vitro interaction assay, reporter-based translational repression assay","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct interaction and functional reporter assay, single lab, two orthogonal methods","pmids":["35756894"],"is_preprint":false},{"year":2020,"finding":"4EHP is expressed in excitatory neurons and synaptosomes, and its abundance increases during development. Conditional knockout of 4EHP in excitatory forebrain neurons results in exaggerated mGluR-LTD and impaired social behavior, without affecting global protein synthesis, indicating that 4EHP regulates translation of specific mRNAs to mediate synaptic plasticity.","method":"Conditional knockout mouse model, electrophysiology (mGluR-LTD), behavioral assays, polysome profiling","journal":"Molecular autism","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional knockout with defined electrophysiological and behavioral phenotypes, multiple orthogonal methods","pmids":["33225984"],"is_preprint":false},{"year":2017,"finding":"eIF4E2 drives hypoxia-specific translation of cadherin-22 mRNA through an mTORC1-independent mechanism. Silencing eIF4E2 or cadherin-22 significantly impaired cancer cell migration and invasion only under hypoxic conditions; reintroduction of the respective exogenous gene restored normal phenotype.","method":"siRNA knockdown, rescue overexpression, migration/invasion assay under normoxia and hypoxia, spheroid formation assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and rescue experiments with specific phenotypic readouts under defined conditions, single lab","pmids":["28991229"],"is_preprint":false},{"year":2024,"finding":"4EHP controls replication of DNA viruses by mediating translational repression of Cgas mRNA (encoding the DNA viral sensor cGAS) triggered by miR-23a. 4EHP deficiency bolsters innate immune responses against HSV-1 and Vaccinia Virus and reduces their replication in vitro and in vivo.","method":"4EHP knockout cells and mice, viral infection assays, reporter assay for miR-23a/Cgas, innate immune cytokine measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout in vitro and in vivo with viral infection, miRNA-mediated translational repression assay, multiple DNA viruses tested","pmids":["39560640"],"is_preprint":false},{"year":2025,"finding":"4EHP ISGylation at K134 and K222 (mediated by HERC5) enhances the eIF4E2-GSK3β interaction and suppresses proline-directed serine/threonine phosphorylation across multiple targets in the eIF4E2-GSK3β pathway, conferring cytoprotection against oxygen-glucose deprivation/reoxygenation stress.","method":"NITAC (Nanobody-based ISGylation Targeting Chimera) tool, site-specific ISGylation, kinase activity assay, OGD/R stress assay, mass spectrometry","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — engineered tool enabling site-specific ISGylation with functional kinase and cytoprotection readouts, single lab, novel method","pmids":["41022323"],"is_preprint":false},{"year":2025,"finding":"4EHP is required for ATF4 signaling in Drosophila larval fat body. In a TRIBE screen, NELF-E mRNA was identified as a top 4EHP-interacting target. Knockdown of either 4EHP or NELF-E reduces multiple 40S ribosomal subunit proteins and eIF3 subunits, and suppresses expression of ATF4 and its target genes, placing 4EHP in an ATF4 regulatory network with NELF-E, 40S ribosome, and eIF3.","method":"TRIBE (Targets of RNA Binding through Editing) screen, quantitative proteomics, genetic knockdown of pathway components in Drosophila","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TRIBE screen combined with quantitative proteomics and genetic epistasis, in vivo Drosophila model, single lab","pmids":["41436469"],"is_preprint":false},{"year":2023,"finding":"Conditional knockout of 4EHP in excitatory (CaMKIIα) or inhibitory (GAD65) neurons impairs spatial working memory in the T-maze task. This impairment is associated with dramatically reduced phosphorylation of ribosomal protein S6 (a measure of mTORC1 activity) in the CA1 hippocampus of 4EHP-cKOexc mice, linking 4EHP-mediated translational control to mTORC1 regulation in working memory.","method":"Conditional knockout mouse, behavioral assays (T-maze, fear conditioning, Morris water maze), immunostaining for pS6 as mTORC1 readout","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific knockout with behavioral and molecular readouts, single lab, limited mechanistic depth","pmids":["36650535"],"is_preprint":false},{"year":2025,"finding":"ZC3H7A and ZC3H7B RNA-binding proteins interact with the GIGYF2/4EHP translation repressor complex to block translation initiation of mRNAs enriched in non-optimal A/U3 codons. Depletion of 4EHP impairs repression of non-optimal A/U3-rich mRNAs, placing 4EHP downstream of ZC3H7A/B in a codon-optimality-linked translational control pathway.","method":"Co-immunoprecipitation, reporter assay, RNA-seq, ribosome profiling, 4EHP depletion","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, co-IP and reporter/ribosome profiling, single lab, not yet peer-reviewed; 4EHP finding is supportive but secondary","pmids":[],"is_preprint":true}],"current_model":"EIF4E2 (4EHP) is a cytoplasmic cap-binding protein with ~30-fold lower cap affinity than eIF4E that cannot bind eIF4G; it acts primarily as a translational repressor by competing with eIF4E for the 5' cap of specific mRNAs, to which it is recruited through direct interactions with adapter proteins including GIGYF1/2 (which are required for repressive activity), Bicoid/Prep1, TTP, and miRISC components (4E-T, TNRC6A), and its activity is modulated by post-translational modifications including ISGylation (enhancing cap binding) and non-degradative ubiquitination by ARIH1 (promoting translation arrest); physiologically, 4EHP-GIGYF1/2 complexes mediate co-translational mRNA decay, ribosome-associated quality control, miRNA-induced gene silencing, hypoxia-specific protein synthesis, antiviral innate immune regulation (repressing Ifnb1 via miR-34a and Cgas via miR-23a), and synaptic plasticity underlying social behavior and working memory in mice."},"narrative":{"mechanistic_narrative":"EIF4E2 (4EHP) is a cytoplasmic cap-binding protein that functions as a sequence- and context-specific translational repressor, acting as a functional antagonist of the canonical initiation factor eIF4E [PMID:9582349, PMID:17369309]. It recognizes the m7G cap through a mechanism shared with eIF4E but binds cap analogs with ~30–100-fold lower affinity and, critically, cannot bind eIF4G, so it cannot stimulate translation [PMID:9582349, PMID:17369309]. Repression is achieved by recruitment to specific mRNAs through adapter proteins that tether the 5' cap to the 3'UTR or to silencing machinery: Drosophila Bicoid and mammalian Prep1 link 4EHP-bound caps to 3'UTR elements in a closed-loop mechanism [PMID:15882623, PMID:19365557], while the obligate partners GIGYF1/2 — whose binding is structurally selective for 4EHP over eIF4E and is required for repressive activity — couple it to a broad repression network [PMID:22751931, PMID:28698298]. 4EHP-GIGYF1/2 complexes integrate multiple regulatory outputs, including miRNA-induced silencing via 4E-T, TNRC6A, and the CCR4-NOT/DDX6 machinery [PMID:28487484, PMID:28755203, PMID:31439631], tristetraprolin-directed decay of ARE-containing mRNAs [PMID:26763119, PMID:31439631], and ribosome-stalling-coupled co-translational mRNA decay and ribosome-associated quality control through ZNF598 and DDX6 [PMID:32726578, PMID:33053355]. Cap-binding activity is tuned by post-translational modification, with ISGylation enhancing cap affinity [PMID:17289916] and non-degradative ubiquitination by ARIH1 triggering translation arrest under genotoxic stress [PMID:25624349]. Physiologically, 4EHP drives hypoxia-specific, mTORC1-independent translation of select mRNAs required for cancer cell survival, migration, and tumor formation [PMID:24408918, PMID:28991229], represses antiviral genes Ifnb1 (via miR-34a) and Cgas (via miR-23a) to restrain innate immunity [PMID:33581076, PMID:39560640], and controls translation of specific neuronal mRNAs underlying synaptic plasticity, social behavior, and working memory in mice [PMID:33225984, PMID:36650535].","teleology":[{"year":1998,"claim":"Established the founding paradox: a second cap-binding protein exists that, unlike eIF4E, cannot engage eIF4G and therefore cannot promote translation, implying a repressive rather than activating role.","evidence":"In vitro cap-binding assay, homology modeling and site-directed mutagenesis of recombinant 4EHP","pmids":["9582349"],"confidence":"High","gaps":["No cellular mRNA targets identified","Mechanism of recruitment to specific transcripts unknown"]},{"year":2005,"claim":"Defined the first concrete repression mechanism — cap-dependent translational inhibition via 5'-3' tethering — showing 4EHP is recruited to a specific mRNA by a sequence-specific 3'UTR-binding adapter.","evidence":"Genetic and biochemical assays in Drosophila embryos with Bicoid and cad mRNA, cap-binding and interaction assays","pmids":["15882623"],"confidence":"High","gaps":["Generality to mammalian systems unproven at the time","Did not identify other adapter proteins"]},{"year":2007,"claim":"Quantified why 4EHP does not block general translation, showing its much lower cap affinity restricts competition with eIF4E to contexts where it is locally concentrated by adapters.","evidence":"Fluorescence titration and stopped-flow kinetics on m7GpppG and m7GTP","pmids":["17369309"],"confidence":"High","gaps":["Did not address how affinity is boosted on target mRNAs in cells"]},{"year":2007,"claim":"Identified ISGylation as a regulatory switch that raises 4EHP cap-binding activity, linking its repressive function to interferon, genotoxic stress, and infection.","evidence":"ISGylation assay with cap-binding readout comparing modified vs unmodified 4EHP","pmids":["17289916"],"confidence":"Medium","gaps":["Modified residues not mapped at the time","Downstream translational consequences not defined"]},{"year":2003,"claim":"Implicated ARIH1/HHARI-family ubiquitin ligase machinery in 4EHP regulation, initially interpreted as degradative ubiquitination.","evidence":"Co-IP and overexpression ubiquitylation assay in mammalian cells","pmids":["14623119"],"confidence":"Medium","gaps":["Degradative interpretation later revised","No physiological trigger identified"]},{"year":2012,"claim":"Identified GIGYF2 as a direct, mutually stabilizing 4EHP partner whose complex is physiologically essential, shifting the field from isolated adapters to a core repressor module.","evidence":"Reciprocal co-IP, mass spectrometry, mouse genetic disruption with translational and developmental readouts","pmids":["22751931"],"confidence":"High","gaps":["Structural basis of selectivity not yet known","Spectrum of regulated mRNAs undefined"]},{"year":2017,"claim":"Provided the structural basis for why GIGYF1/2 bind 4EHP but not eIF4E and proved that GIGYF1/2 engagement is required for 4EHP repressive activity.","evidence":"X-ray crystallography of GIGYF1/2-4EHP, structure-guided mutagenesis, complementation in knockout cells","pmids":["28698298"],"confidence":"High","gaps":["Did not define how the complex is delivered to specific transcripts"]},{"year":2016,"claim":"Connected the 4EHP-GIGYF2 module to ARE-mediated mRNA fate by showing it acts as a cofactor for tristetraprolin in repression and decay of ARE-containing transcripts.","evidence":"Co-IP, in vitro pull-down, mutagenesis of TTP tetraproline motifs, reporter assays, 4EHP-knockout MEFs","pmids":["26763119"],"confidence":"High","gaps":["Relative contribution of repression vs decay not resolved"]},{"year":2017,"claim":"Placed 4EHP within the miRNA silencing pathway, showing 4E-T and TNRC6A recruit it to miRNA targets and that 4E-T binding raises its cap affinity, enabling a closed-loop block of initiation.","evidence":"Co-IP, cap-binding and tethering/miRNA reporter assays, knockdown with endogenous target analysis","pmids":["28487484","28755203"],"confidence":"High","gaps":["Quantitative contribution of 4EHP to global miRNA silencing unclear"]},{"year":2018,"claim":"Dissected GIGYF2 as having both 4EHP-dependent (translational) and 4EHP-independent (CCR4-NOT/deadenylation) repressive arms, defining 4EHP as one of several GIGYF2 effector routes.","evidence":"Tethering reporter assays, domain mutagenesis, co-IP, RNA-binding and endogenous target analysis","pmids":["29554310"],"confidence":"Medium","gaps":["Coordination between the two arms in vivo not resolved"]},{"year":2018,"claim":"Identified specific endogenous targets and a signaling output, showing 4EHP/miRISC represses Dusp6 via miR-145 to modulate ERK signaling, cell growth, and apoptosis.","evidence":"Ribosome profiling, reporter assay, ERK phosphorylation western blot, knockout/knockdown phenotypes","pmids":["29412140"],"confidence":"High","gaps":["Breadth of the 4EHP-controlled translatome only partially mapped"]},{"year":2019,"claim":"Resolved the molecular architecture linking 4EHP-GIGYF to mRNA decay, showing GIGYF recruits DDX6/Me31B, HPat, and CCR4-NOT and that complex assembly is required for TTP-mediated repression.","evidence":"Co-IP, tethering and decay assays, motif mutagenesis, and a 2.4 Å GIGYF-DDX6 crystal structure with structure-guided mutants","pmids":["31114929","31439631"],"confidence":"High","gaps":["In vivo stoichiometry and dynamics of the assembled complex unknown"]},{"year":2015,"claim":"Reframed ARIH1 ubiquitination of 4EHP as non-degradative, showing it drives 4EHP cap association and translation arrest as a genotoxic stress response.","evidence":"RNAi screen, co-IP, ubiquitination and cap-binding assays, polysome profiling, epistasis rescue","pmids":["25624349"],"confidence":"Medium","gaps":["Ubiquitin chain topology and recognition partner not fully defined"]},{"year":2020,"claim":"Established 4EHP-GIGYF1/2 as the effector that couples ribosome stalling to translational shutoff and co-translational mRNA decay, integrating it into ribosome-associated quality control.","evidence":"Genome-wide CRISPR screens, ribosome profiling, mRNA stability assays, co-IP, knockout cells with ZNF598/DDX6 dependence","pmids":["32726578","33053355"],"confidence":"High","gaps":["Signal that triggers GIGYF recruitment to stalled ribosomes incompletely defined"]},{"year":2014,"claim":"Revealed a distinct activating role under hypoxia, where 4EHP drives mTORC1-independent cap-dependent translation of a subset of mRNAs required for cancer cell survival and tumor formation.","evidence":"siRNA knockdown, hypoxic polysome profiling, spheroid and xenograft assays; with cadherin-22 identified as a hypoxic target driving migration/invasion","pmids":["24408918","28991229"],"confidence":"High","gaps":["Molecular switch converting 4EHP from repressor to hypoxic activator not defined"]},{"year":2020,"claim":"Demonstrated an in vivo neuronal role, showing 4EHP loss in forebrain excitatory neurons exaggerates mGluR-LTD and impairs social behavior without altering global translation.","evidence":"Conditional knockout mice, electrophysiology, behavioral assays, polysome profiling","pmids":["33225984"],"confidence":"High","gaps":["Specific neuronal mRNA targets not identified"]},{"year":2021,"claim":"Established 4EHP as an antiviral immune regulator, repressing Ifnb1 translation via a virus-induced miR-34a negative feedback loop in vivo.","evidence":"4EHP knockout mice, reporter assays, polysome profiling, viral infection and cytokine measurement","pmids":["33581076"],"confidence":"High","gaps":["Cell types responsible for the in vivo phenotype not fully resolved"]},{"year":2022,"claim":"Extended 4EHP control to non-cap-binding functions, showing it interacts with GSK3β to sustain proline-directed phosphorylation of p53 and resist hypoxic senescence.","evidence":"Co-IP, kinase activity and peptide inhibition assays, senescence and in vivo liver assays, S-nitrosylation analysis","pmids":["35568694"],"confidence":"Medium","gaps":["How a cap-binding protein scaffolds a kinase pathway mechanistically unclear","Single-lab finding"]},{"year":2022,"claim":"Identified METTL16 as a cytoplasmic regulator that, independent of its methyltransferase activity, blocks 4EHP cap recruitment to favor eIF4E-driven selective translation.","evidence":"Co-IP, cap-binding and translation reporter assays, depletion/overexpression with polysome analysis","pmids":["36840945"],"confidence":"Medium","gaps":["Which mRNAs are switched between 4EHP and eIF4E not defined","Single-lab finding"]},{"year":2022,"claim":"Showed viral subversion of the complex, with SARS-CoV-2 NSP2 binding 4EHP and GIGYF2 to impair GIGYF2-mediated repression.","evidence":"In vitro interaction and reporter-based repression assays","pmids":["35756894"],"confidence":"Medium","gaps":["Consequences for host translation during infection not mapped","Single-lab finding"]},{"year":2024,"claim":"Defined a second antiviral axis, with 4EHP repressing Cgas via miR-23a to restrain DNA-virus sensing both in vitro and in vivo.","evidence":"4EHP knockout cells and mice, HSV-1 and Vaccinia infection, miR-23a/Cgas reporter assays, cytokine measurement","pmids":["39560640"],"confidence":"High","gaps":["Whether the miR-23a/Cgas axis operates in all relevant cell types unclear"]},{"year":2025,"claim":"Mapped 4EHP ISGylation to K134/K222 by HERC5 and linked it to enhanced GSK3β engagement and cytoprotection against ischemic stress, refining the earlier ISGylation observation.","evidence":"NITAC site-specific ISGylation tool, kinase activity assay, OGD/R stress assay, mass spectrometry","pmids":["41022323"],"confidence":"Medium","gaps":["Interplay between ISGylation and cap-binding vs GSK3β arms not reconciled","Single-lab finding"]},{"year":2025,"claim":"Connected 4EHP to ATF4 stress signaling, showing in Drosophila that it binds NELF-E mRNA and supports expression of 40S/eIF3 components and ATF4 targets.","evidence":"TRIBE screen, quantitative proteomics, genetic epistasis in Drosophila fat body","pmids":["41436469"],"confidence":"Medium","gaps":["Conservation of the ATF4/NELF-E network in mammals untested","Direct vs indirect effects on ribosomal subunit expression unresolved"]},{"year":null,"claim":"It remains unclear what molecular switch converts 4EHP between its dominant repressor mode and its hypoxic translational-activator mode, and how its diverse adapter, modification, and kinase-scaffolding functions are coordinated on individual transcripts in vivo.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model reconciling repressor and activator activities","Determinants of target mRNA selection across pathways not defined","Structural basis of the GSK3β scaffolding function unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,2,14]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[1,7,11,20]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,10,22]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,6,11]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6,15,22]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[15]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[9,11,20]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,7,19]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[21,27]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[8,16,19]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[25,30]}],"complexes":["4EHP-GIGYF2 complex","4EHP-GIGYF-DDX6 (Me31B) complex"],"partners":["GIGYF2","GIGYF1","4E-T","TNRC6A","ZNF598","DDX6","ARIH1","GSK3B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60573","full_name":"Eukaryotic translation initiation factor 4E type 2","aliases":["Eukaryotic translation initiation factor 4E homologous protein","Eukaryotic translation initiation factor 4E-like 3","eIF4E-like protein 4E-LP","mRNA cap-binding protein 4EHP","h4EHP","mRNA cap-binding protein type 3"],"length_aa":245,"mass_kda":28.4,"function":"Recognizes and binds the 7-methylguanosine-containing mRNA cap during an early step in the initiation. Acts as a repressor of translation initiation (PubMed:17368478, PubMed:22751931, PubMed:25624349, PubMed:33581076, PubMed:9582349). In contrast to EIF4E, it is unable to bind eIF4G (EIF4G1, EIF4G2 or EIF4G3), suggesting that it acts by competing with EIF4E and block assembly of eIF4F at the cap (By similarity). In P-bodies, component of a complex that promotes miRNA-mediated translational repression (PubMed:28487484). Involved in virus-induced host response by mediating miRNA MIR34A-induced translational silencing which controls IFNB1 production by a negative feedback mechanism (PubMed:28487484, PubMed:33581076) Component of the 4EHP-GYF2 complex, a multiprotein complex that acts as a repressor of translation initiation (PubMed:22751931, PubMed:35878012). In association with GIGYF2, assists ribosome-associated quality control (RQC) by sequestering the mRNA cap, blocking ribosome initiation and decreasing the translational load on problematic messages. Part of a pathway that works in parallel to RQC-mediated degradation of the stalled nascent polypeptide. GIGYF2 and EIF4E2 work downstream and independently of ZNF598, which seems to work as a scaffold that can recruit them to faulty mRNA even if alternative recruitment mechanisms may exist (PubMed:32726578) (Microbial infection) Upon SARS coronavirus-2/SARS-CoV-2 infection, the interaction with non-structural protein 2 (nsp2) with GIGYF2 enhances GIGYF2 binding to EIF4E2 and increases repression of translation initiation of genes involved in antiviral innate immune response such as IFNB1","subcellular_location":"Cytoplasm; Cytoplasm, P-body","url":"https://www.uniprot.org/uniprotkb/O60573/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/EIF4E2","classification":"Not Classified","n_dependent_lines":214,"n_total_lines":1208,"dependency_fraction":0.1771523178807947},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RACK1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/EIF4E2","total_profiled":1310},"omim":[{"mim_id":"617508","title":"ZINC FINGER PROTEIN 598; ZNF598","url":"https://www.omim.org/entry/617508"},{"mim_id":"612003","title":"GRB10-INTERACTING GYF PROTEIN 2; GIGYF2","url":"https://www.omim.org/entry/612003"},{"mim_id":"605895","title":"EUKARYOTIC TRANSLATION INITIATION FACTOR 4E FAMILY, MEMBER 2; EIF4E2","url":"https://www.omim.org/entry/605895"},{"mim_id":"603349","title":"ENDOTHELIAL PAS DOMAIN PROTEIN 1; EPAS1","url":"https://www.omim.org/entry/603349"},{"mim_id":"602571","title":"RNA-BINDING MOTIF PROTEIN 4; RBM4","url":"https://www.omim.org/entry/602571"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EIF4E2"},"hgnc":{"alias_symbol":["IF4e","4EHP"],"prev_symbol":["EIF4EL3"]},"alphafold":{"accession":"O60573","domains":[{"cath_id":"3.30.760.10","chopping":"54-218","consensus_level":"high","plddt":94.6165,"start":54,"end":218}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60573","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60573-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60573-F1-predicted_aligned_error_v6.png","plddt_mean":80.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EIF4E2","jax_strain_url":"https://www.jax.org/strain/search?query=EIF4E2"},"sequence":{"accession":"O60573","fasta_url":"https://rest.uniprot.org/uniprotkb/O60573.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60573/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60573"}},"corpus_meta":[{"pmid":"15882623","id":"PMC_15882623","title":"A new paradigm for 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cap-binding protein with 30% identity to eIF4E. It binds specifically to capped RNA in an ATP- and divalent ion-independent manner. Homology modeling and site-directed mutagenesis strongly suggest it shares with eIF4E a common mechanism for cap binding, but unlike eIF4E, 4EHP does not interact with eIF4G and therefore cannot stimulate translation.\",\n      \"method\": \"Biochemical cap-binding assay, homology modeling, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro cap-binding assay combined with site-directed mutagenesis, foundational characterization paper replicated in subsequent studies\",\n      \"pmids\": [\"9582349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Drosophila 4EHP (d4EHP) specifically interacts with Bicoid (Bcd) protein to suppress caudal (cad) mRNA translation. d4EHP binds the 5' cap structure while Bcd simultaneously binds the Bicoid binding region (BBR) in the cad 3'UTR, effectively tethering the 5' and 3' ends of cad mRNA to render it translationally inactive. This defines a new paradigm for cap-dependent translational inhibition not mediated by canonical eIF4E.\",\n      \"method\": \"Genetic and biochemical assays in Drosophila embryos, cap-binding assays, interaction assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution of translational repression with defined molecular interactions, multiple orthogonal methods, seminal paper subsequently replicated across labs\",\n      \"pmids\": [\"15882623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"4EHP binds cap analogs m7GpppG and m7GTP with 30- and 100-fold lower affinity than eIF4E, respectively, as measured by fluorescence titration and stopped-flow measurements. This low binding affinity explains why 4EHP cannot compete with eIF4E for the cap of most mRNAs and thus does not inhibit general translation.\",\n      \"method\": \"Fluorescence titration, stopped-flow kinetic measurements\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — two orthogonal quantitative biophysical methods in a single focused study establishing cap-binding affinity differences\",\n      \"pmids\": [\"17369309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"4EHP is modified by ISG15 (ISGylation), and ISGylated 4EHP has significantly higher cap structure-binding activity than unmodified 4EHP. ISGylation of 4EHP is activated by interferon, genotoxic stress, and pathogen infection.\",\n      \"method\": \"ISGylation assay, cap-binding activity assay comparing modified vs. unmodified 4EHP\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical modification assay with functional readout (cap-binding enhancement), single lab but two orthogonal methods\",\n      \"pmids\": [\"17289916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HHARI (human homologue of ariadne) interacts with 4EHP via its N-terminal RING1 finger. Overexpression of 4EHP and HHARI in mammalian cells leads to polyubiquitylation of 4EHP, suggesting HHARI promotes ubiquitin-mediated degradation of 4EHP. HHARI, 4EHP, and UbcH7 do not form a stable heterotrimeric complex as 4EHP cannot immunoprecipitate UbcH7 even in the presence of HHARI.\",\n      \"method\": \"Co-immunoprecipitation, overexpression-based ubiquitylation assay in mammalian cells\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP and ubiquitylation assay, single lab, two complementary methods\",\n      \"pmids\": [\"14623119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"4E-BP1 binds to 4EHP via the same interface used for eIF4E binding; eIF4E-binding mutants of 4E-BP1 (Y54A and L59A) fail to form complexes with 4EHP, and the W95A mutant of 4EHP inhibits its binding to 4E-BP1. Overexpression of 4EHP triggers a negative feedback loop inhibiting upstream signaling to 4E-BP1 and S6K1, dependent on the 4E-BP1 binding interaction.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis, overexpression with signaling readouts\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis combined with co-IP and signaling assay, single lab, multiple approaches\",\n      \"pmids\": [\"15094042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Mammalian 4EHP co-localizes and interacts with the homeodomain transcription factor Prep1 in the cytosol of mouse oocytes. Prep1 contains a functional 4EHP-binding motif (identified by mutagenesis). Prep1 inhibits (>95%) in vitro translation of a luciferase reporter fused to the Hoxb4 3'UTR in the presence of 4EHP, and Prep1 binds the Hoxb4 3'UTR directly (EMSA), suggesting a 5'-3' mRNA tethering mechanism.\",\n      \"method\": \"Confocal microscopy, co-immunoprecipitation, pull-down, site-directed mutagenesis of binding motif, in vitro translation assay, RNA EMSA\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, in vitro translation, EMSA) in a single lab\",\n      \"pmids\": [\"19365557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mammalian 4EHP forms a complex with GIGYF2 and ZNF598. GIGYF2 directly interacts with 4EHP, and this interaction is required for stabilization of both proteins. Disruption of the m4EHP-GIGYF2 complex leads to increased translation and perinatal lethality in mice, establishing the complex as a physiologically essential translational repressor.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, mouse knockout/genetic disruption with translational and developmental phenotype readouts\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, MS identification of complex, in vivo genetic disruption with defined molecular and developmental phenotype\",\n      \"pmids\": [\"22751931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Upon DNA damage, ARIH1 E3 ubiquitin ligase associates with 4EHP and promotes its non-degradative ubiquitination. This leads to enrichment of ARIH1 in perinuclear ribosome-containing regions and 4EHP association with the mRNA 5' cap, triggering mRNA translation arrest in an ARIH1-dependent manner. Restoration of translation arrest in ARIH1-depleted cells via an eIF2 inhibitor was sufficient to reinstate resistance to genotoxic stress.\",\n      \"method\": \"RNAi screen, co-immunoprecipitation, ubiquitination assay, cap-binding assay, polysome profiling, epistasis rescue experiment\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical assays and epistasis, single lab\",\n      \"pmids\": [\"25624349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The 4EHP-GYF2 (GIGYF2) complex acts as a cofactor of tristetraprolin (TTP) for translational repression and mRNA decay of AU-rich element (ARE)-containing mRNAs. TTP directly interacts with GIGYF2 via conserved tetraproline motifs. Mutant TTP with diminished 4EHP-GYF2 binding is impaired in repressing ARE-mRNAs, and 4EHP knockout MEFs show increased induction and slower turnover of TTP-target mRNAs.\",\n      \"method\": \"Co-immunoprecipitation, in vitro pull-down, mutational analysis, luciferase reporter assay, 4EHP knockout MEFs\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, in vitro pull-down, mutagenesis, reporter assay, and knockout cell lines across multiple orthogonal approaches\",\n      \"pmids\": [\"26763119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structures of the 4EHP-binding regions of GIGYF1 and GIGYF2 in complex with 4EHP reveal the molecular basis for selective binding of GIGYF1/2 to 4EHP but not eIF4E. Structure-guided mutants in complementation assays in GIGYF1/2-null cells demonstrate that 4EHP requires interactions with GIGYF1/2 for repressive activity on target mRNAs.\",\n      \"method\": \"X-ray crystallography, structure-based mutagenesis, complementation assay in knockout cell line\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with structure-based mutagenesis and functional complementation assay\",\n      \"pmids\": [\"28698298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"4EHP is an integral component of the miRNA-mediated silencing machinery. 4EHP cap-binding activity contributes to translational silencing by miRNAs through the CCR4-NOT complex. 4EHP competes with eIF4E for binding to 4E-T, and this interaction increases 4EHP's affinity for the cap. A closed-loop mRNA conformation via the 4E-T/4EHP interaction is proposed to block translational initiation of miRNA targets.\",\n      \"method\": \"Co-immunoprecipitation, cap-binding assay, reporter assay (tethering and miRNA-mediated silencing), loss-of-function experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, cap-binding, reporter assays, knockdown) across different experimental contexts\",\n      \"pmids\": [\"28487484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TNRC6A (a GW182 family protein) interacts with 4EHP/EIF4E2 to inhibit translation of miRNA target mRNAs. Downregulation of 4EHP/EIF4E2 relieved miRNA repression of reporter constructs and increased protein levels of endogenous miRNA targets (IMP1, PTEN, PDCD4). miRNA enhances 4EHP association with target mRNA.\",\n      \"method\": \"Co-immunoprecipitation, reporter assay, siRNA knockdown, endogenous protein level analysis\",\n      \"journal\": \"Protein & cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus functional reporter assays and endogenous target validation, single lab\",\n      \"pmids\": [\"28755203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"4EHP translationally represses Dusp6 mRNA (encoding ERK phosphatase) via miR-145, promoting ERK1/2 phosphorylation, augmented cell growth, and reduced apoptosis. Ribosome profiling identified a subset of mRNAs translationally controlled by 4EHP, placing 4EHP/miRISC in the ERK signaling cascade.\",\n      \"method\": \"Ribosome profiling, reporter assay, western blot for ERK phosphorylation, 4EHP knockout/knockdown with cellular phenotype readouts\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ribosome profiling combined with reporter assay, signaling readout, and knockout validation, multiple orthogonal approaches\",\n      \"pmids\": [\"29412140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GIGYF2 has two distinct mechanisms of mRNA repression: one depends on 4EHP binding and mainly affects translation; the other is 4EHP-independent and involves recruitment of the CCR4/NOT complex through multiple interfaces leading to deadenylation. Three independent domains of GIGYF2 have repressive activity in tethering reporter assays. GIGYF2 is an RNA-binding protein with identifiable endogenous mRNA targets.\",\n      \"method\": \"Tethering reporter assay, domain mutagenesis, co-immunoprecipitation, RNA-binding protein assay, endogenous mRNA target identification\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domains tested by mutagenesis combined with reporter assays and co-IP, single lab\",\n      \"pmids\": [\"29554310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Human 4EHP/eIF4E2 binds 4E-T via the canonical YX4Lφ sequence, and this interaction recruits 4EHP to P-bodies in mammalian cells. 4EHP does not redistribute to stress granules in arsenite-treated cells or to P-bodies in Actinomycin D-treated cells (unlike eIF4E1). 4EHP shuttles through the nucleus in a Crm1-dependent but 4E-T-independent manner.\",\n      \"method\": \"Yeast two-hybrid, pull-down assay, indirect immunofluorescence, cellular fractionation, drug treatment (leptomycin B for Crm1 inhibition)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple localization methods (immunofluorescence, Y2H, pull-down) in a single lab; localization tied to functional context\",\n      \"pmids\": [\"23991149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"eIF4E2 is activated under hypoxia to drive cap-dependent translation of a subset of mRNAs in cancer cells. eIF4E2-depleted cancer cells cannot survive or proliferate in low oxygen, cannot form a hypoxic tumor core in spheroids, and fail to form tumors in xenograft assays, whereas they are indistinguishable from controls under normoxia.\",\n      \"method\": \"siRNA knockdown, in vitro spheroid assay, in vivo xenograft assay, polysome profiling under hypoxia\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with defined molecular mechanism in both in vitro and in vivo models, multiple complementary assays\",\n      \"pmids\": [\"24408918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Drosophila GIGYF, when in complex with 4EHP, elicits both translational repression and mRNA decay via recruitment of Me31B/DDX6 (RNA helicase), HPat (decapping activator), and the CCR4-NOT deadenylase complex. Discrete binding motifs in GIGYF conserved among metazoan GIGYF proteins are required for Me31B and HPat recruitment and for downregulation of mRNA expression.\",\n      \"method\": \"Co-immunoprecipitation, tethering reporter assay, mutagenesis of binding motifs, mRNA decay assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus mutagenesis and reporter assay, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"31114929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystal structure (2.4 Å) of the GIGYF-Me31B/DDX6 complex reveals that the GIGYF motif arranges into a coil connected to a β hairpin, binding conserved hydrophobic patches on the Me31B RecA2 domain. Structure-guided mutants confirm that 4EHP-GIGYF-DDX6 complex assembly is required for tristetraprolin-mediated down-regulation of an AU-rich mRNA.\",\n      \"method\": \"X-ray crystallography (2.4 Å), structure-based mutagenesis, mRNA reporter assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure combined with structure-based mutagenesis and functional assay\",\n      \"pmids\": [\"31439631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"4EHP and GIGYF2 form a negative feedback loop that inhibits translation initiation on mRNAs that have undergone failed translation (ribosome-associated quality control). CRISPR-Cas9 screens identified GIGYF2 and 4EHP as mediators of this feedback; loss of these factors leads to accumulation of partially synthesized toxic polypeptides from defective mRNAs.\",\n      \"method\": \"CRISPR-Cas9-based genetic screen, model substrate assays, growth-based assays, translation initiation assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide CRISPR screen followed by mechanistic validation with model substrates and growth assays\",\n      \"pmids\": [\"32726578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"4EHP-GIGYF1/2 complexes trigger co-translational mRNA decay. Human cells lacking these proteins accumulate mRNAs with ribosome pausing, including transcripts encoding secretory/membrane proteins and tubulin. 4EHP-GIGYF1/2-mediated mRNA decay requires cap structure interaction, DDX6 interaction, ZNF598 interaction, and is dependent on ribosome stalling; GIGYF1/2 co-translational binding marks transcripts with perturbed elongation for decay.\",\n      \"method\": \"Ribosome profiling, mRNA stability assay, co-immunoprecipitation, knockout cell lines\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ribosome profiling combined with knockout cell lines and multiple interaction/functional assays\",\n      \"pmids\": [\"33053355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"4EHP suppresses IFN-β production by mediating miR-34a-induced translational silencing of Ifnb1 mRNA. miR-34a is upregulated by RNA virus infection and IFN-β, creating a negative feedback loop that represses IFN-β expression via 4EHP. 4EHP knockout mice show elevated IFN-β and altered virus replication, establishing an in vivo role for 4EHP in antiviral immunity.\",\n      \"method\": \"4EHP knockout mice, reporter assay, polysome profiling, in vivo viral infection, cytokine measurement\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout with defined molecular mechanism (miR-34a/Ifnb1 axis), multiple orthogonal methods including viral infection models\",\n      \"pmids\": [\"33581076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"METTL16 interacts with 4EHP/eIF4E2 in the cytoplasm. This interaction impedes the recruitment of 4EHP to the 5' cap structure, thereby promoting cap recognition by eIF4E and selective protein synthesis. METTL16 depletion attenuates protein synthesis, and this effect is mediated through 4EHP, not METTL16's methyltransferase activity.\",\n      \"method\": \"Co-immunoprecipitation, cap-binding assay, translation reporter assay, METTL16 depletion/overexpression with polysome analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with functional cap-binding and translation assays, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"36840945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"4EHP/eIF4E2 interacts with GSK3β and maintains basal proline-directed serine/threonine (S/T-P) phosphorylation of p53 and other targets, thereby resisting cellular senescence under hypoxia. Peptides blocking the eIF4E2-GSK3β interaction inhibit S/T-P phosphorylation and induce senescence. Hypoxia inhibits this pathway through S-nitrosylation of GSK3β.\",\n      \"method\": \"Co-immunoprecipitation, kinase activity assay, peptide inhibition, senescence assays, in vivo mouse liver model, S-nitrosylation assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP combined with functional kinase assay and multiple cellular/in vivo readouts, single lab\",\n      \"pmids\": [\"35568694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SARS-CoV-2 NSP2 physically associates with both 4EHP and GIGYF2 (binding a central segment of GIGYF2) in the cytoplasm, and impairs GIGYF2-mediated translation repression as shown by reporter-based assays.\",\n      \"method\": \"In vitro interaction assay, reporter-based translational repression assay\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct interaction and functional reporter assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"35756894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"4EHP is expressed in excitatory neurons and synaptosomes, and its abundance increases during development. Conditional knockout of 4EHP in excitatory forebrain neurons results in exaggerated mGluR-LTD and impaired social behavior, without affecting global protein synthesis, indicating that 4EHP regulates translation of specific mRNAs to mediate synaptic plasticity.\",\n      \"method\": \"Conditional knockout mouse model, electrophysiology (mGluR-LTD), behavioral assays, polysome profiling\",\n      \"journal\": \"Molecular autism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional knockout with defined electrophysiological and behavioral phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"33225984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"eIF4E2 drives hypoxia-specific translation of cadherin-22 mRNA through an mTORC1-independent mechanism. Silencing eIF4E2 or cadherin-22 significantly impaired cancer cell migration and invasion only under hypoxic conditions; reintroduction of the respective exogenous gene restored normal phenotype.\",\n      \"method\": \"siRNA knockdown, rescue overexpression, migration/invasion assay under normoxia and hypoxia, spheroid formation assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and rescue experiments with specific phenotypic readouts under defined conditions, single lab\",\n      \"pmids\": [\"28991229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"4EHP controls replication of DNA viruses by mediating translational repression of Cgas mRNA (encoding the DNA viral sensor cGAS) triggered by miR-23a. 4EHP deficiency bolsters innate immune responses against HSV-1 and Vaccinia Virus and reduces their replication in vitro and in vivo.\",\n      \"method\": \"4EHP knockout cells and mice, viral infection assays, reporter assay for miR-23a/Cgas, innate immune cytokine measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout in vitro and in vivo with viral infection, miRNA-mediated translational repression assay, multiple DNA viruses tested\",\n      \"pmids\": [\"39560640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"4EHP ISGylation at K134 and K222 (mediated by HERC5) enhances the eIF4E2-GSK3β interaction and suppresses proline-directed serine/threonine phosphorylation across multiple targets in the eIF4E2-GSK3β pathway, conferring cytoprotection against oxygen-glucose deprivation/reoxygenation stress.\",\n      \"method\": \"NITAC (Nanobody-based ISGylation Targeting Chimera) tool, site-specific ISGylation, kinase activity assay, OGD/R stress assay, mass spectrometry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — engineered tool enabling site-specific ISGylation with functional kinase and cytoprotection readouts, single lab, novel method\",\n      \"pmids\": [\"41022323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"4EHP is required for ATF4 signaling in Drosophila larval fat body. In a TRIBE screen, NELF-E mRNA was identified as a top 4EHP-interacting target. Knockdown of either 4EHP or NELF-E reduces multiple 40S ribosomal subunit proteins and eIF3 subunits, and suppresses expression of ATF4 and its target genes, placing 4EHP in an ATF4 regulatory network with NELF-E, 40S ribosome, and eIF3.\",\n      \"method\": \"TRIBE (Targets of RNA Binding through Editing) screen, quantitative proteomics, genetic knockdown of pathway components in Drosophila\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TRIBE screen combined with quantitative proteomics and genetic epistasis, in vivo Drosophila model, single lab\",\n      \"pmids\": [\"41436469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Conditional knockout of 4EHP in excitatory (CaMKIIα) or inhibitory (GAD65) neurons impairs spatial working memory in the T-maze task. This impairment is associated with dramatically reduced phosphorylation of ribosomal protein S6 (a measure of mTORC1 activity) in the CA1 hippocampus of 4EHP-cKOexc mice, linking 4EHP-mediated translational control to mTORC1 regulation in working memory.\",\n      \"method\": \"Conditional knockout mouse, behavioral assays (T-maze, fear conditioning, Morris water maze), immunostaining for pS6 as mTORC1 readout\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific knockout with behavioral and molecular readouts, single lab, limited mechanistic depth\",\n      \"pmids\": [\"36650535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ZC3H7A and ZC3H7B RNA-binding proteins interact with the GIGYF2/4EHP translation repressor complex to block translation initiation of mRNAs enriched in non-optimal A/U3 codons. Depletion of 4EHP impairs repression of non-optimal A/U3-rich mRNAs, placing 4EHP downstream of ZC3H7A/B in a codon-optimality-linked translational control pathway.\",\n      \"method\": \"Co-immunoprecipitation, reporter assay, RNA-seq, ribosome profiling, 4EHP depletion\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, co-IP and reporter/ribosome profiling, single lab, not yet peer-reviewed; 4EHP finding is supportive but secondary\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"EIF4E2 (4EHP) is a cytoplasmic cap-binding protein with ~30-fold lower cap affinity than eIF4E that cannot bind eIF4G; it acts primarily as a translational repressor by competing with eIF4E for the 5' cap of specific mRNAs, to which it is recruited through direct interactions with adapter proteins including GIGYF1/2 (which are required for repressive activity), Bicoid/Prep1, TTP, and miRISC components (4E-T, TNRC6A), and its activity is modulated by post-translational modifications including ISGylation (enhancing cap binding) and non-degradative ubiquitination by ARIH1 (promoting translation arrest); physiologically, 4EHP-GIGYF1/2 complexes mediate co-translational mRNA decay, ribosome-associated quality control, miRNA-induced gene silencing, hypoxia-specific protein synthesis, antiviral innate immune regulation (repressing Ifnb1 via miR-34a and Cgas via miR-23a), and synaptic plasticity underlying social behavior and working memory in mice.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EIF4E2 (4EHP) is a cytoplasmic cap-binding protein that functions as a sequence- and context-specific translational repressor, acting as a functional antagonist of the canonical initiation factor eIF4E [#0, #2]. It recognizes the m7G cap through a mechanism shared with eIF4E but binds cap analogs with ~30–100-fold lower affinity and, critically, cannot bind eIF4G, so it cannot stimulate translation [#0, #2]. Repression is achieved by recruitment to specific mRNAs through adapter proteins that tether the 5' cap to the 3'UTR or to silencing machinery: Drosophila Bicoid and mammalian Prep1 link 4EHP-bound caps to 3'UTR elements in a closed-loop mechanism [#1, #6], while the obligate partners GIGYF1/2 — whose binding is structurally selective for 4EHP over eIF4E and is required for repressive activity — couple it to a broad repression network [#7, #10]. 4EHP-GIGYF1/2 complexes integrate multiple regulatory outputs, including miRNA-induced silencing via 4E-T, TNRC6A, and the CCR4-NOT/DDX6 machinery [#11, #12, #18], tristetraprolin-directed decay of ARE-containing mRNAs [#9, #18], and ribosome-stalling-coupled co-translational mRNA decay and ribosome-associated quality control through ZNF598 and DDX6 [#19, #20]. Cap-binding activity is tuned by post-translational modification, with ISGylation enhancing cap affinity [#3] and non-degradative ubiquitination by ARIH1 triggering translation arrest under genotoxic stress [#8]. Physiologically, 4EHP drives hypoxia-specific, mTORC1-independent translation of select mRNAs required for cancer cell survival, migration, and tumor formation [#16, #26], represses antiviral genes Ifnb1 (via miR-34a) and Cgas (via miR-23a) to restrain innate immunity [#21, #27], and controls translation of specific neuronal mRNAs underlying synaptic plasticity, social behavior, and working memory in mice [#25, #30].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established the founding paradox: a second cap-binding protein exists that, unlike eIF4E, cannot engage eIF4G and therefore cannot promote translation, implying a repressive rather than activating role.\",\n      \"evidence\": \"In vitro cap-binding assay, homology modeling and site-directed mutagenesis of recombinant 4EHP\",\n      \"pmids\": [\"9582349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No cellular mRNA targets identified\", \"Mechanism of recruitment to specific transcripts unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the first concrete repression mechanism — cap-dependent translational inhibition via 5'-3' tethering — showing 4EHP is recruited to a specific mRNA by a sequence-specific 3'UTR-binding adapter.\",\n      \"evidence\": \"Genetic and biochemical assays in Drosophila embryos with Bicoid and cad mRNA, cap-binding and interaction assays\",\n      \"pmids\": [\"15882623\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality to mammalian systems unproven at the time\", \"Did not identify other adapter proteins\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Quantified why 4EHP does not block general translation, showing its much lower cap affinity restricts competition with eIF4E to contexts where it is locally concentrated by adapters.\",\n      \"evidence\": \"Fluorescence titration and stopped-flow kinetics on m7GpppG and m7GTP\",\n      \"pmids\": [\"17369309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address how affinity is boosted on target mRNAs in cells\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified ISGylation as a regulatory switch that raises 4EHP cap-binding activity, linking its repressive function to interferon, genotoxic stress, and infection.\",\n      \"evidence\": \"ISGylation assay with cap-binding readout comparing modified vs unmodified 4EHP\",\n      \"pmids\": [\"17289916\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Modified residues not mapped at the time\", \"Downstream translational consequences not defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Implicated ARIH1/HHARI-family ubiquitin ligase machinery in 4EHP regulation, initially interpreted as degradative ubiquitination.\",\n      \"evidence\": \"Co-IP and overexpression ubiquitylation assay in mammalian cells\",\n      \"pmids\": [\"14623119\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Degradative interpretation later revised\", \"No physiological trigger identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified GIGYF2 as a direct, mutually stabilizing 4EHP partner whose complex is physiologically essential, shifting the field from isolated adapters to a core repressor module.\",\n      \"evidence\": \"Reciprocal co-IP, mass spectrometry, mouse genetic disruption with translational and developmental readouts\",\n      \"pmids\": [\"22751931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of selectivity not yet known\", \"Spectrum of regulated mRNAs undefined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided the structural basis for why GIGYF1/2 bind 4EHP but not eIF4E and proved that GIGYF1/2 engagement is required for 4EHP repressive activity.\",\n      \"evidence\": \"X-ray crystallography of GIGYF1/2-4EHP, structure-guided mutagenesis, complementation in knockout cells\",\n      \"pmids\": [\"28698298\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how the complex is delivered to specific transcripts\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected the 4EHP-GIGYF2 module to ARE-mediated mRNA fate by showing it acts as a cofactor for tristetraprolin in repression and decay of ARE-containing transcripts.\",\n      \"evidence\": \"Co-IP, in vitro pull-down, mutagenesis of TTP tetraproline motifs, reporter assays, 4EHP-knockout MEFs\",\n      \"pmids\": [\"26763119\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of repression vs decay not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed 4EHP within the miRNA silencing pathway, showing 4E-T and TNRC6A recruit it to miRNA targets and that 4E-T binding raises its cap affinity, enabling a closed-loop block of initiation.\",\n      \"evidence\": \"Co-IP, cap-binding and tethering/miRNA reporter assays, knockdown with endogenous target analysis\",\n      \"pmids\": [\"28487484\", \"28755203\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of 4EHP to global miRNA silencing unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Dissected GIGYF2 as having both 4EHP-dependent (translational) and 4EHP-independent (CCR4-NOT/deadenylation) repressive arms, defining 4EHP as one of several GIGYF2 effector routes.\",\n      \"evidence\": \"Tethering reporter assays, domain mutagenesis, co-IP, RNA-binding and endogenous target analysis\",\n      \"pmids\": [\"29554310\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Coordination between the two arms in vivo not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified specific endogenous targets and a signaling output, showing 4EHP/miRISC represses Dusp6 via miR-145 to modulate ERK signaling, cell growth, and apoptosis.\",\n      \"evidence\": \"Ribosome profiling, reporter assay, ERK phosphorylation western blot, knockout/knockdown phenotypes\",\n      \"pmids\": [\"29412140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Breadth of the 4EHP-controlled translatome only partially mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved the molecular architecture linking 4EHP-GIGYF to mRNA decay, showing GIGYF recruits DDX6/Me31B, HPat, and CCR4-NOT and that complex assembly is required for TTP-mediated repression.\",\n      \"evidence\": \"Co-IP, tethering and decay assays, motif mutagenesis, and a 2.4 Å GIGYF-DDX6 crystal structure with structure-guided mutants\",\n      \"pmids\": [\"31114929\", \"31439631\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo stoichiometry and dynamics of the assembled complex unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Reframed ARIH1 ubiquitination of 4EHP as non-degradative, showing it drives 4EHP cap association and translation arrest as a genotoxic stress response.\",\n      \"evidence\": \"RNAi screen, co-IP, ubiquitination and cap-binding assays, polysome profiling, epistasis rescue\",\n      \"pmids\": [\"25624349\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin chain topology and recognition partner not fully defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established 4EHP-GIGYF1/2 as the effector that couples ribosome stalling to translational shutoff and co-translational mRNA decay, integrating it into ribosome-associated quality control.\",\n      \"evidence\": \"Genome-wide CRISPR screens, ribosome profiling, mRNA stability assays, co-IP, knockout cells with ZNF598/DDX6 dependence\",\n      \"pmids\": [\"32726578\", \"33053355\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal that triggers GIGYF recruitment to stalled ribosomes incompletely defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed a distinct activating role under hypoxia, where 4EHP drives mTORC1-independent cap-dependent translation of a subset of mRNAs required for cancer cell survival and tumor formation.\",\n      \"evidence\": \"siRNA knockdown, hypoxic polysome profiling, spheroid and xenograft assays; with cadherin-22 identified as a hypoxic target driving migration/invasion\",\n      \"pmids\": [\"24408918\", \"28991229\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular switch converting 4EHP from repressor to hypoxic activator not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated an in vivo neuronal role, showing 4EHP loss in forebrain excitatory neurons exaggerates mGluR-LTD and impairs social behavior without altering global translation.\",\n      \"evidence\": \"Conditional knockout mice, electrophysiology, behavioral assays, polysome profiling\",\n      \"pmids\": [\"33225984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific neuronal mRNA targets not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established 4EHP as an antiviral immune regulator, repressing Ifnb1 translation via a virus-induced miR-34a negative feedback loop in vivo.\",\n      \"evidence\": \"4EHP knockout mice, reporter assays, polysome profiling, viral infection and cytokine measurement\",\n      \"pmids\": [\"33581076\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell types responsible for the in vivo phenotype not fully resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended 4EHP control to non-cap-binding functions, showing it interacts with GSK3β to sustain proline-directed phosphorylation of p53 and resist hypoxic senescence.\",\n      \"evidence\": \"Co-IP, kinase activity and peptide inhibition assays, senescence and in vivo liver assays, S-nitrosylation analysis\",\n      \"pmids\": [\"35568694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a cap-binding protein scaffolds a kinase pathway mechanistically unclear\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified METTL16 as a cytoplasmic regulator that, independent of its methyltransferase activity, blocks 4EHP cap recruitment to favor eIF4E-driven selective translation.\",\n      \"evidence\": \"Co-IP, cap-binding and translation reporter assays, depletion/overexpression with polysome analysis\",\n      \"pmids\": [\"36840945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which mRNAs are switched between 4EHP and eIF4E not defined\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed viral subversion of the complex, with SARS-CoV-2 NSP2 binding 4EHP and GIGYF2 to impair GIGYF2-mediated repression.\",\n      \"evidence\": \"In vitro interaction and reporter-based repression assays\",\n      \"pmids\": [\"35756894\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Consequences for host translation during infection not mapped\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a second antiviral axis, with 4EHP repressing Cgas via miR-23a to restrain DNA-virus sensing both in vitro and in vivo.\",\n      \"evidence\": \"4EHP knockout cells and mice, HSV-1 and Vaccinia infection, miR-23a/Cgas reporter assays, cytokine measurement\",\n      \"pmids\": [\"39560640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the miR-23a/Cgas axis operates in all relevant cell types unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mapped 4EHP ISGylation to K134/K222 by HERC5 and linked it to enhanced GSK3β engagement and cytoprotection against ischemic stress, refining the earlier ISGylation observation.\",\n      \"evidence\": \"NITAC site-specific ISGylation tool, kinase activity assay, OGD/R stress assay, mass spectrometry\",\n      \"pmids\": [\"41022323\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interplay between ISGylation and cap-binding vs GSK3β arms not reconciled\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected 4EHP to ATF4 stress signaling, showing in Drosophila that it binds NELF-E mRNA and supports expression of 40S/eIF3 components and ATF4 targets.\",\n      \"evidence\": \"TRIBE screen, quantitative proteomics, genetic epistasis in Drosophila fat body\",\n      \"pmids\": [\"41436469\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conservation of the ATF4/NELF-E network in mammals untested\", \"Direct vs indirect effects on ribosomal subunit expression unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unclear what molecular switch converts 4EHP between its dominant repressor mode and its hypoxic translational-activator mode, and how its diverse adapter, modification, and kinase-scaffolding functions are coordinated on individual transcripts in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model reconciling repressor and activator activities\", \"Determinants of target mRNA selection across pathways not defined\", \"Structural basis of the GSK3β scaffolding function unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 2, 14]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [1, 7, 11, 20]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 10, 22]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 6, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6, 15, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [9, 11, 20]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 7, 19]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [21, 27]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [8, 16, 19]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [25, 30]}\n    ],\n    \"complexes\": [\n      \"4EHP-GIGYF2 complex\",\n      \"4EHP-GIGYF-DDX6 (Me31B) complex\"\n    ],\n    \"partners\": [\n      \"GIGYF2\",\n      \"GIGYF1\",\n      \"4E-T\",\n      \"TNRC6A\",\n      \"ZNF598\",\n      \"DDX6\",\n      \"ARIH1\",\n      \"GSK3B\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}