{"gene":"EIF1","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":1999,"finding":"NMR solution structure of human eIF1 determined: residues 29–113 form a tightly packed domain with two α-helices flanking a five-stranded mixed β-sheet, with a fold similar to ribosomal proteins and RNA-binding domains. GST pull-down showed eIF1 binds specifically to the p110 subunit of eIF3, explaining eIF1 recruitment to the 40S subunit. No interaction with eIF5 or an initiation-site RNA was detected by NMR.","method":"NMR spectroscopy (structure determination); GST pull-down (binding partner identification)","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure combined with pull-down binding assay; multiple orthogonal methods in a single rigorous study","pmids":["10228174"],"is_preprint":false},{"year":2000,"finding":"eIF1 participates in a multifactor complex (MFC) with eIF2, eIF3, eIF5, and initiator Met-tRNAi in yeast cell extracts free of 40S ribosomes. eIF5 bridges eIF3 (via NIP1 N-terminus) and eIF2β simultaneously; the NIP1 N-terminus binds both eIF5 and eIF1 concurrently. The MFC is disrupted by the tif5-7A mutation in eIF5's bipartite motif, which also causes temperature-sensitive growth and reduced translation initiation.","method":"In vitro binding assays (pull-down); yeast genetic analysis; co-immunoprecipitation from cell extracts","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assays plus genetic confirmation, replicated across multiple mutants","pmids":["11018020"],"is_preprint":false},{"year":1996,"finding":"Yeast SUI1 (eIF1) is identical to the p16 subunit of eIF3: anti-SUI1 antisera immunoprecipitate all eIF3 subunits, and anti-eIF3 antisera immunoprecipitate SUI1. eIF3 isolated from a sui1(ts) strain at 37°C lacks SUI1 and fails eIF3 activity in a methionyl-puromycin synthesis assay, demonstrating SUI1 is required for eIF3 activity.","method":"Co-immunoprecipitation; SDS-PAGE; in vitro methionyl-puromycin synthesis assay; temperature-sensitive genetic analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP plus functional biochemical assay in the same study","pmids":["8628297"],"is_preprint":false},{"year":1990,"finding":"Genetic characterization in S. cerevisiae established that SUI1 (eIF1) mutations (recessive, temperature-sensitive) suppress loss of the HIS4 AUG start codon, restoring translation initiation at non-AUG codons, placing SUI1 as a component of the translation initiation complex required for AUG start codon recognition.","method":"Yeast genetic reversion analysis; complementation tests; suppressor mapping","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — classical genetic epistasis with multiple alleles and codon variants, foundational replicated result","pmids":["2179049"],"is_preprint":false},{"year":1998,"finding":"The yeast mof2-1 allele is a novel allele of SUI1 (eIF1). Strains with mof2-1 show increased programmed −1 ribosomal frameshifting and mutant start-site selection. Purified wild-type Mof2p/Sui1p added back to mof2-1 extracts reduced frameshifting to wild-type levels. Human SUI1 expressed in yeast corrects all mof2-1 phenotypes, demonstrating functional conservation and a role for eIF1 in translational accuracy during elongation as well as initiation.","method":"Yeast genetics; in vitro frameshifting assay with purified protein add-back; cross-species complementation","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro reconstitution of frameshifting phenotype with purified protein, plus cross-species complementation","pmids":["9488467"],"is_preprint":false},{"year":2004,"finding":"The N-terminal domain (NTD) of NIP1/eIF3c directly binds eIF1 and eIF5. Mutations in NIP1-NTD segments reduce eIF1 or eIF5 binding, and a C-terminal NIP1-NTD mutation increases UUG start codon use (Sui− phenotype), which is suppressed by eIF1 overexpression. The NIP1-NTD coordinates eIF1–eIF5 interaction to inhibit GTP hydrolysis at non-AUG codons, and MFC formation stimulates TC recruitment to 40S ribosomes.","method":"In vitro pull-down assays; yeast genetic analysis (Sui−/Gcd− phenotypes); overexpression suppression studies","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple binding mutants analyzed with orthogonal genetic and biochemical approaches","pmids":["15485912"],"is_preprint":false},{"year":2007,"finding":"Sui− mutations in eIF1 reduce its interaction with 40S subunits in vitro and in vivo. The Sui− mutation 93-97 accelerates eIF1 dissociation from reconstituted preinitiation complexes (PICs) and accelerates Pi release from eIF2, while a hyperaccuracy eIF1A mutation slows eIF1 dissociation. eIF1 dissociation is therefore a critical gating step for start codon selection, modulated by eIF1A. Additional Gcd− eIF1 mutations impair TC loading on 40S subunits or destabilize the MFC.","method":"Reconstituted PIC assembly (in vitro); kinetic measurement of eIF1 dissociation and Pi release; yeast genetics; in vivo 40S binding assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with kinetic measurements plus corroborating in vivo genetics","pmids":["17504939"],"is_preprint":false},{"year":2007,"finding":"eIF1 carries two distinct eIF5-binding interfaces: (1) the unstructured N-terminal tail (stimulates cooperative MFC assembly) and (2) a basic/hydrophobic surface area termed KH (includes hydrophobic residues critical for linking eIF1 to the PIC prior to AUG recognition). Mutation of KH is lethal and shows dominant relaxed start codon selection, placing eIF5 as a direct binding partner at the decoding site.","method":"NMR-based binding mapping; yeast two-hybrid and pull-down; genetic analysis of KH mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure-guided mutagenesis plus genetic confirmation, single lab but multiple orthogonal methods","pmids":["17974565"],"is_preprint":false},{"year":2009,"finding":"eIF1 controls at least two steps in start codon recognition: (1) gating Pi release from eIF2, and (2) triggering the transition from an open, scanning-competent PIC conformation to a stable, closed one upon AUG recognition. eIF1 G107 mutations confer Sui− phenotypes without increasing eIF1 release rate, indicating a role in conformational gating distinct from dissociation. eIF5 antagonizes eIF1 binding to the PIC by competing for a key site.","method":"Reconstituted PIC assays; kinetic measurements; yeast genetic analysis; eIF1/eIF5 binding competition experiments","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with kinetic analysis plus genetic validation, single lab, multiple orthogonal methods","pmids":["19751744"],"is_preprint":false},{"year":2010,"finding":"Human eIF1 protein translation initiates from an AUG in poor Kozak context, enabling a negative autoregulatory feedback loop: high eIF1 levels increase stringency of start codon selection and thereby suppress translation of its own mRNA. This establishes that eIF1 concentration directly controls the stringency of initiation codon recognition genome-wide.","method":"Reporter assays; eIF1 overexpression experiments; mutagenesis of the eIF1 5′-UTR AUG context in human cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional reporter and overexpression studies with mechanistic context mutagenesis, single lab, multiple orthogonal methods","pmids":["20921384"],"is_preprint":false},{"year":2012,"finding":"The C-terminal domain of eIF5 (eIF5-CTD) interacts with eIF1 and eIF2β at partially overlapping surfaces, identified by NMR. eIF5-CTD mutations disrupting these interfaces impair start codon recognition and impede eIF1 release from the PIC, showing that eIF5-CTD binding to eIF2β is required for eIF1 displacement and the open-to-closed PIC switch.","method":"NMR spectroscopy (binding surface mapping); site-directed mutagenesis; genetic and biochemical PIC assembly assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR-guided mutagenesis plus functional genetic validation, single lab","pmids":["22813744"],"is_preprint":false},{"year":2013,"finding":"The C-terminal tail (CTT) of eIF1A moves closer to eIF5-NTD upon AUG recognition, and this movement is coupled to eIF1 dissociation from the PIC. eIF1 dissociation must be accompanied by eIF1A-CTT movement toward eIF5 to trigger Pi release from eIF2. The same event (tRNAi accommodation in the P site driven by start-codon base pairing) triggers both eIF1 dissociation and eIF1A-CTT repositioning. The C-terminal domain of eIF5 antagonizes eIF1 binding.","method":"FRET-based kinetic assays in reconstituted PICs; mutant biochemical analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with FRET kinetics and multiple mutant validations, single lab","pmids":["23293029"],"is_preprint":false},{"year":2013,"finding":"eIF1 β-hairpin loop-1 residues (Arg-33, Lys-37) and helix α1 Lys-60 directly contact 18S rRNA in the 40S·eIF1 complex. Substituting these residues impairs eIF1 binding to 40S·eIF1A complexes in vitro and increases UUG initiation (Sui− phenotype) in vivo, suppressible by eIF1 overexpression or an eIF1A mutation that impedes eIF1 dissociation. The unstructured N-terminal tail of eIF1 also blocks the PIC from rearranging to the closed conformation at non-AUG codons.","method":"Crystal structure-guided mutagenesis; in vitro 40S binding assays; yeast genetic analysis (Sui−/Gcd− phenotypes); suppression analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — structure-guided mutagenesis with orthogonal in vitro and in vivo validation","pmids":["23893413"],"is_preprint":false},{"year":2013,"finding":"Ssu− (suppressor of Sui−) mutations in eIF1 increase eIF1 affinity for 40S subunits in vitro. The strongest-binding variant (D61G) reduces the eIF1 off-rate and destabilizes PIN-state TC binding in reconstituted PICs, establishing that eIF1 dissociation from the 40S subunit is mechanistically required for Met-tRNAi accommodation in the PIN state and that eIF5 and eIF2β promote accuracy by controlling eIF1 dissociation.","method":"In vitro 40S binding affinity assays; reconstituted PIC kinetic assays; yeast genetics (Ssu−/Sui− suppression)","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with kinetic off-rate measurements and in vivo genetic validation, single lab","pmids":["24335188"],"is_preprint":false},{"year":2014,"finding":"X-ray crystal structures of the six-subunit yeast eIF3 core combined with cryo-EM, cross-linking/mass spectrometry, and integrative modeling placed eIF1 on the 40S·eIF3 complex. Yeast eIF3 engages 40S in a clamp-like manner, encircling the subunit to position eIF1 and other key initiation factors on opposite ends of the mRNA channel.","method":"X-ray crystallography; cryo-EM; cross-linking coupled to mass spectrometry; integrative structure modeling","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal structural methods with functional context, replicated across approaches","pmids":["25171412"],"is_preprint":false},{"year":2015,"finding":"Cryo-EM structure of a budding yeast 40S·eIF1·eIF1A·eIF3·eIF3j initiation complex resolved positions of eIF1, eIF1A, eIF3a, eIF3b, eIF3c on the 40S subunit and revealed a direct contact between eIF3j and eIF1A.","method":"Cryo-EM structure determination; placement of prior X-ray structures","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structural study with multiple factor placements, single study","pmids":["25664723"],"is_preprint":false},{"year":2015,"finding":"eIF1 stimulates translation initiation from TISU-AUG (short 5′ UTR context) while inhibiting non-TISU-directed initiation. eIF4GI shares this dual activity and directly interacts with eIF1. eIF4F is released upon 48S formation on TISU mRNA. Purified 48S preinitiation complex is sufficient for initiation via TISU AUG when preceded by a short 5′ UTR, revealing a specialized mechanism enabling mitochondrial gene translation under energy stress.","method":"In vitro 48S reconstitution; purified factor assays; co-immunoprecipitation (eIF4GI–eIF1 interaction); translation reporter assays in AMPK-KO cells","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus co-IP and cell-based validation, single lab, multiple methods","pmids":["25738462"],"is_preprint":false},{"year":2018,"finding":"Cryo-EM structure of a yeast 48S PIC at 3.0 Å shows eIF5-NTD bound to the 40S subunit at the position vacated by eIF1. eIF5-NTD interacts with and accommodates Met-tRNAi in a more PIN-like orientation. Substitutions in eIF5 residues contacting tRNAi alter UUG initiation in vivo and PIC open/closed state in vitro, demonstrating that eIF5 directly stabilizes the codon:anticodon duplex after eIF1 departure.","method":"Cryo-EM (3.0 Å); site-directed mutagenesis; in vitro PIC conformation assays; yeast genetic analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM with mutagenesis and orthogonal functional validation","pmids":["30475211"],"is_preprint":false},{"year":2018,"finding":"eIF4G1 exists in two mutually exclusive complexes: one with eIF4E and one with eIF1. Using an eIF1 mutant impaired in eIF4G1 binding, eIF1–eIF4G1 interaction was shown to be important for leaky scanning and for avoiding cap-proximal initiation. eIF4E–eIF4G1 antagonizes the scanning promoted by eIF1–eIF4G1. The eIF4G1 transition from eIF4E to eIF1 binding is proposed to accompany the 43S ribosome's move from the cap to the scanning mode.","method":"Co-immunoprecipitation; eIF1 binding-site mutants; translation reporter assays; interaction mapping","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and functional mutant analysis, single lab","pmids":["29987188"],"is_preprint":false},{"year":2018,"finding":"eIF1 Loop 2 is juxtaposed with the Met-tRNAi D loop in the PIN state (from PIC structures). Ala substitutions in Loop 2 (D71A, M74A) increase initiation at UUG codons and AUGs in poor context, and stabilize TC binding to 48S PICs with UUG mRNA, without affecting eIF1 affinity for 40S subunits or POUT-mode TC loading. Arg substitutions convert the predicted Loop 2–tRNAi clash to an electrostatic attraction, further stabilizing PIN state. Thus Loop 2–D loop interactions specifically impede Met-tRNAi accommodation in PIN state.","method":"Site-directed mutagenesis; in vitro 48S PIC reconstitution; TC binding assays; yeast genetic analysis (UUG initiation, Kozak context reporters)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structure-guided mutagenesis, in vitro reconstitution, and in vivo genetic validation in single study","pmids":["29666249"],"is_preprint":false},{"year":2020,"finding":"Ribosome profiling of a yeast eIF1-L96P variant (weakened PIC binding) shows genome-wide increases in translation of uORFs initiating at near-cognate codons (NCCs) or AUGs in poor Kozak context, frequently reducing downstream CDS translation. eIF1 also controls the ratio of mitochondrial protein isoforms translated from NCC versus AUG start codons (e.g., GRS1, ALA1). Thus eIF1 discriminates against suboptimal start codons throughout the translatome.","method":"Ribosome profiling (genome-wide); eIF1 mutant (L96P) yeast strain","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide ribosome profiling with defined eIF1 mutant, single lab","pmids":["31915290"],"is_preprint":false},{"year":2022,"finding":"Small-molecule inhibitors of eIF4G1–eIF1 interaction (i14G1-10 and i14G1-12) directly bind eIF4G1, inhibit translation in vitro and in cells in an eIF4G1-level-dependent manner, and phenocopy eIF1/eIF4G1 perturbations on start codon stringency. i14G1s activate ER/UPR stress-response genes through enhanced 5′ UTR near-cognate AUG translation, independently of eIF2α phosphorylation. eIF4G1–eIF1 interaction is itself negatively regulated by ER stress and mTOR inhibition.","method":"In vitro translation assays; translatome profiling; small-molecule–protein binding assays; reporter assays in cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological perturbation plus translatome profiling, single lab, multiple methods","pmids":["35857873"],"is_preprint":false},{"year":2024,"finding":"During mammalian mitosis, a nuclear pool of eIF1 is released into the cytoplasm upon nuclear envelope breakdown, increasing eIF1–40S ribosome association and globally enhancing stringency of start-codon selection. Low-efficiency initiation sites are preferentially repressed in mitosis. Selectively depleting the nuclear pool of eIF1 eliminates the mitotic change in translational stringency, alters protein isoform synthesis, and increases cell death and decreases mitotic slippage following anti-mitotic drug treatment.","method":"Transcriptome-wide translation initiation site profiling; nuclear pool-specific eIF1 depletion; cell viability assays; co-sedimentation (eIF1–40S interaction)","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide initiation profiling plus targeted nuclear pool depletion with defined functional consequence, replicated in preprint and peer-reviewed form","pmids":["39443796"],"is_preprint":false},{"year":2024,"finding":"SARS-CoV-2 Nsp1 cooperates with EIF1 and EIF1A to selectively enhance translation of viral RNA. When EIF1/EIF1A are depleted, more ribosomes initiate from a conserved upstream CUG codon in viral mRNAs, shifting translation to uORF1 and reducing main ORF translation. Replacing the upstream CUG with AUG strongly inhibits main ORF translation independently of Nsp1, EIF1, or EIF1A, demonstrating that EIF1/EIF1A normally suppress upstream CUG usage to favor downstream AUG selection.","method":"Ribosome profiling; EIF1/EIF1A knockdown; reporter assays; start-codon mutagenesis","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ribosome profiling plus KD and reporter mutagenesis, single lab","pmids":["38335237"],"is_preprint":false},{"year":2024,"finding":"Single-molecule fluorescence analysis of in vitro reconstituted human translation initiation shows eIF1 loads onto mRNAs as part of the 43S complex and departs rapidly (~2 s) in a start-site-dependent manner; alternative start sites and longer 5′ UTRs delay departure. After initial departure, eIF1 transiently and repeatedly samples initiation complexes, with more prolonged sampling at alternative start sites. eIF5 only transiently binds late in initiation immediately before eIF5B association, and its binding requires a start site and is inhibited by alternative start sites.","method":"Single-molecule fluorescence (TIRF); in vitro reconstituted human initiation; knockdown and overexpression in human cells","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule reconstitution with cell-based validation, single lab, preprint","pmids":["39026837"],"is_preprint":true},{"year":2003,"finding":"The HEAT domain of yeast eIF4G2 interacts directly with eIF1, and eIF1 can simultaneously bind eIF4G and eIF3c in vitro. The eIF4G HEAT domain mutations reduce binding to eIF1 and eIF5, increase UUG initiation, and the sui1-1 eIF1 mutation reduces the eIF4G–eIF1 interaction. eIF4G HEAT domain binding to eIF1 is thus important for maintaining scanning PIC integrity and AUG fidelity.","method":"In vitro pull-down; genetic suppression analysis; yeast genetic analysis (UUG initiation reporters)","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding plus corroborating genetics, single lab","pmids":["12861028"],"is_preprint":false},{"year":1999,"finding":"Human A121/SUI1 (eIF1) expression is induced at the mRNA level by genotoxic and ER stress in a p53-independent manner. Expression of human A121 in yeast complemented the sui1 mutant phenotype, confirming its identity as a functional eIF1 ortholog. Two mRNA transcripts (1.35 kb and 0.65 kb) with a common coding region but different 3′ UTRs are differentially regulated by stress.","method":"Subtractive PCR; yeast complementation; Northern blot analysis; stress-induction experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation plus differential expression analysis, single lab","pmids":["10347211"],"is_preprint":false},{"year":1999,"finding":"mof2-1 (a SUI1/eIF1 allele) affects the nonsense-mediated mRNA decay (NMD) pathway in addition to translation initiation and frameshifting fidelity. Human SUI1 expressed in yeast activates NMD, suggesting eIF1 functions as a general modulator in multiple aspects of translation and mRNA turnover.","method":"Yeast genetic analysis; NMD reporter assays; cross-species complementation","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reporter assays and complementation, single lab","pmids":["10376878"],"is_preprint":false},{"year":2025,"finding":"NMR backbone assignments of the human eIF3c fragment (residues 166–266) that encompasses the reported eIF1-binding site show this region is intrinsically disordered in solution, with short segments of modest α-helical or β-strand propensity. Three conserved FLKK motifs are located at junctions of transient structural elements. A small helix within this region contacts eIF1 in cryo-EM PIC structures. These assignments provide a foundation for mapping the eIF1-binding surface on eIF3c.","method":"NMR spectroscopy (1H–15N HSQC; backbone assignments; chemical shift index analysis)","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 1 / Weak — structural characterization (NMR assignments only) without functional interaction validation; preprint","pmids":["bio_10.1101_2025.09.13.675972"],"is_preprint":true}],"current_model":"EIF1 (SUI1/A121) is a universally conserved ~12 kDa translation initiation factor that binds the 40S ribosomal subunit (via contacts with 18S rRNA and eIF3c/p110) as part of a multifactor complex (MFC) with eIF2, eIF3, eIF5, and Met-tRNAi; it stabilizes the open, scanning-competent conformation of the preinitiation complex (PIC) by blocking Met-tRNAi accommodation in the PIN state, and its dissociation from the PIC upon AUG codon recognition—stimulated by eIF5 and eIF2β and modulated by eIF1A—is the critical gate that allows irreversible Pi release from eIF2·GDP·Pi, conversion to the closed PIC conformation, and stable 48S complex formation; additionally, a nuclear pool of eIF1 is released during mitosis to globally increase the stringency of start-codon selection, eIF1 autoregulates its own translation through a poor-context AUG, and it cooperates with eIF4GI to control scanning-dependent versus scanning-independent initiation."},"narrative":{"mechanistic_narrative":"EIF1 (SUI1) is a universally conserved small translation initiation factor that enforces the fidelity of start-codon selection during ribosomal scanning [PMID:2179049, PMID:17504939]. It assembles into a multifactor complex with eIF2, eIF3, eIF5, and initiator Met-tRNAi, where the N-terminal domain of eIF3c (NIP1) binds eIF1 and eIF5 concurrently to coordinate their action and stimulate ternary complex recruitment to the 40S subunit [PMID:11018020, PMID:8628297, PMID:15485912]. On the 40S subunit, eIF1 contacts 18S rRNA via β-hairpin loop-1 and helix α1 residues and stabilizes the open, scanning-competent conformation of the preinitiation complex, while its β-hairpin Loop 2 sterically clashes with the Met-tRNAi D loop to block tRNAi accommodation in the PIN state at non-AUG and poor-context codons [PMID:23893413, PMID:29666249]. Recognition of an AUG codon drives eIF1 dissociation from the PIC—a critical gating step that permits irreversible Pi release from eIF2 and the open-to-closed conformational switch; eIF5 and eIF2β promote accuracy by controlling this dissociation, eIF1A modulates its rate, and the eIF5 N-terminal domain then occupies the site vacated by eIF1 to stabilize the codon:anticodon duplex [PMID:17504939, PMID:19751744, PMID:22813744, PMID:23293029, PMID:24335188, PMID:30475211]. Because eIF1 concentration sets the genome-wide stringency of initiation, eIF1 autoregulates its own synthesis through a poor-context AUG, and its loss broadly de-represses translation at upstream near-cognate and poor-context start codons [PMID:20921384, PMID:31915290]. Beyond the core scanning machinery, eIF1 cooperates with eIF4G1 in a complex mutually exclusive with eIF4E to govern leaky scanning and specialized initiation modes including TISU-AUG translation under energy stress [PMID:25738462, PMID:29987188], and a nuclear pool released at mitotic nuclear-envelope breakdown raises start-codon stringency to control isoform output and mitotic cell fate [PMID:39443796].","teleology":[{"year":1990,"claim":"Established eIF1 as a genetic determinant of AUG start-codon recognition, answering whether a dedicated factor enforces initiation-codon identity.","evidence":"Yeast SUI1 suppressor genetics restoring initiation at non-AUG codons at the HIS4 locus","pmids":["2179049"],"confidence":"High","gaps":["Molecular mechanism of codon discrimination undefined","No biochemical or structural basis for the genetic phenotype"]},{"year":1996,"claim":"Linked eIF1 physically and functionally to the eIF3 complex, defining how it is recruited to the initiation machinery.","evidence":"Reciprocal co-IP of SUI1 with eIF3 subunits plus methionyl-puromycin synthesis assay in a sui1(ts) strain","pmids":["8628297"],"confidence":"High","gaps":["Stoichiometry and direct vs indirect contacts not resolved","Did not identify which eIF3 subunit binds eIF1"]},{"year":1999,"claim":"Provided the eIF1 fold and its direct eIF3 binding partner, and showed stress-responsive, conserved expression of the human ortholog.","evidence":"NMR solution structure with GST pull-down to eIF3 p110; human A121/SUI1 yeast complementation and stress-induction Northern blots","pmids":["10228174","10347211"],"confidence":"High","gaps":["No structure of eIF1 bound to the 40S subunit","Functional consequence of stress induction on the translatome unmeasured"]},{"year":2000,"claim":"Defined the multifactor complex architecture, showing eIF5/NIP1 bridges eIF1 to eIF2 and eIF3 prior to ribosome loading.","evidence":"Reciprocal in vitro binding assays and yeast genetics of eIF5 motif mutants in ribosome-free extracts","pmids":["11018020"],"confidence":"High","gaps":["Spatial arrangement on the 40S not yet established","Order of assembly events unresolved"]},{"year":2003,"claim":"Connected eIF1 to the cap-binding/scanning apparatus via eIF4G, implicating it in PIC integrity beyond the MFC core.","evidence":"In vitro pull-down of eIF4G HEAT domain with eIF1 plus UUG-initiation genetics","pmids":["12861028"],"confidence":"Medium","gaps":["Single-lab biochemistry","Functional separation of eIF4G–eIF1 from eIF4G–eIF5 binding incomplete"]},{"year":2004,"claim":"Showed the eIF3c/NIP1 N-terminal domain coordinates eIF1–eIF5 to suppress GTP hydrolysis at non-AUG codons.","evidence":"NIP1-NTD binding mutants with Sui- genetics and eIF1-overexpression suppression in yeast","pmids":["15485912"],"confidence":"High","gaps":["Direct effect on hydrolysis kinetics not measured in this study","Conformational coupling to tRNAi unaddressed"]},{"year":2007,"claim":"Established that eIF1 dissociation from the PIC is the rate-limiting gate for Pi release and start-codon fidelity, and mapped its eIF5-binding interfaces.","evidence":"Reconstituted PIC kinetics of Sui-/Ssu- mutants plus NMR-guided mapping of N-tail and KH eIF5 interfaces","pmids":["17504939","17974565"],"confidence":"High","gaps":["Conformational vs dissociation contributions not fully separated","Precise structural location of eIF1 on the PIC unknown"]},{"year":2009,"claim":"Resolved that eIF1 controls two distinct steps—Pi-release gating and the open-to-closed PIC transition—and that eIF5 competes for its binding site.","evidence":"Reconstituted PIC kinetics of G107 mutants plus eIF1/eIF5 binding competition","pmids":["19751744"],"confidence":"High","gaps":["Atomic basis of the competition not visualized","Coupling to tRNAi accommodation inferred indirectly"]},{"year":2012,"claim":"Defined how the eIF5 C-terminal domain triggers eIF1 displacement by engaging eIF2β, mechanistically linking eIF5 to the conformational switch.","evidence":"NMR surface mapping of eIF5-CTD interfaces with eIF1 and eIF2β plus PIC assembly assays","pmids":["22813744"],"confidence":"High","gaps":["Temporal sequence relative to eIF1A movement unresolved at this stage"]},{"year":2013,"claim":"Connected eIF1 release to specific 18S rRNA contacts, eIF1A-CTT repositioning, and PIN-state tRNAi accommodation, unifying the gating mechanism.","evidence":"Structure-guided mutagenesis of eIF1–18S contacts, FRET kinetics of eIF1A-CTT movement, and 40S off-rate measurements of Ssu- variants in reconstituted PICs","pmids":["23293029","23893413","24335188"],"confidence":"High","gaps":["High-resolution structure of the closed transition state still lacking","How AUG base-pairing energy is transmitted to eIF1 not fully defined"]},{"year":2014,"claim":"Placed eIF1 on the 40S·eIF3 complex within a clamp-like eIF3 architecture, giving a structural framework for factor positioning.","evidence":"X-ray crystallography, cryo-EM, cross-linking/MS and integrative modeling of the yeast eIF3 core on 40S","pmids":["25171412"],"confidence":"High","gaps":["Resolution insufficient for atomic eIF1–rRNA contacts","tRNAi and eIF2 not resolved in this assembly"]},{"year":2015,"claim":"Provided a cryo-EM map of the 40S·eIF1·eIF1A·eIF3·eIF3j complex and revealed an eIF3j–eIF1A contact, and showed eIF1's dual control over TISU vs non-TISU initiation via eIF4GI.","evidence":"Cryo-EM of a yeast initiation complex; in vitro 48S reconstitution, eIF4GI–eIF1 co-IP and reporter assays in AMPK-KO cells","pmids":["25664723","25738462"],"confidence":"High","gaps":["Mechanism coupling eIF4GI–eIF1 to TISU specificity incompletely defined","Mitochondrial gene relevance based on cellular reporters"]},{"year":2018,"claim":"Defined the structural endpoint of eIF1 departure (eIF5-NTD occupying its site), the steric basis of PIN-state discrimination via Loop 2, and the eIF4G1 partner-switch controlling scanning.","evidence":"3.0 Å cryo-EM of 48S PIC with eIF5 mutagenesis; Loop 2 mutagenesis with 48S reconstitution; eIF1/eIF4E mutually exclusive eIF4G1 complexes by co-IP","pmids":["30475211","29666249","29987188"],"confidence":"High","gaps":["eIF4G1 partner-switch model is single-lab and partly inferred","In vivo dynamics of the switch during scanning not directly observed"]},{"year":2020,"claim":"Demonstrated genome-wide that eIF1 level/binding sets translatome-wide discrimination against suboptimal start codons, including mitochondrial isoform ratios.","evidence":"Ribosome profiling of the eIF1-L96P weakened-binding yeast variant","pmids":["31915290"],"confidence":"High","gaps":["Mammalian translatome consequences extrapolated from yeast","Codon-context determinants of sensitivity not exhaustively mapped"]},{"year":2022,"claim":"Showed the eIF4G1–eIF1 interaction is a druggable node regulated by ER stress and mTOR that shapes near-cognate uORF translation independently of eIF2α phosphorylation.","evidence":"Small-molecule inhibitors of eIF4G1–eIF1, in vitro translation, translatome profiling and reporter assays in cells","pmids":["35857873"],"confidence":"Medium","gaps":["Single-lab pharmacology","Direct binding site of inhibitors on eIF4G1 vs eIF1 contributions not crystallographically defined"]},{"year":2024,"claim":"Revealed a nuclear eIF1 pool that, upon mitotic nuclear-envelope breakdown, raises start-codon stringency and governs isoform output and mitotic cell fate; and that eIF1/eIF1A suppress upstream CUG usage exploited during SARS-CoV-2 infection.","evidence":"Initiation-site profiling with nuclear-pool-specific eIF1 depletion and viability assays; ribosome profiling with EIF1/EIF1A knockdown and start-codon mutagenesis in infection","pmids":["39443796","38335237"],"confidence":"High","gaps":["Mechanism of nuclear sequestration and release not molecularly defined","Generality of CUG suppression beyond viral mRNAs untested"]},{"year":2024,"claim":"Single-molecule reconstitution captured eIF1 loading, rapid start-site-dependent departure, and repeated sampling, refining the kinetic model of its gating role.","evidence":"Single-molecule TIRF of reconstituted human initiation with cell-based validation (preprint)","pmids":["39026837"],"confidence":"Medium","gaps":["Preprint, single lab","Repeated-sampling behavior awaits independent confirmation"]},{"year":null,"claim":"How the nuclear eIF1 pool is established, retained, and released, and how the eIF1-binding region of disordered eIF3c folds upon engaging eIF1, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No molecular mechanism for nuclear eIF1 sequestration","eIF3c eIF1-binding surface characterized only as disordered backbone assignments (preprint), without bound-state structure"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[12,0]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[6,8,9,20]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,13,19]}],"localization":[{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[12,14,15,17]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[22]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[22]}],"pathway":[],"complexes":["multifactor complex (eIF1·eIF2·eIF3·eIF5·Met-tRNAi)","43S/48S preinitiation complex","40S·eIF1·eIF1A·eIF3·eIF3j complex"],"partners":["EIF3C","EIF5","EIF1AX","EIF2S2","EIF4G1","EIF3A","EIF3B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P41567","full_name":"Eukaryotic translation initiation factor 1","aliases":["A121","Protein translation factor SUI1 homolog","Sui1iso1"],"length_aa":113,"mass_kda":12.7,"function":"Component of the 43S pre-initiation complex (43S PIC), which binds to the mRNA cap-proximal region, scans mRNA 5'-untranslated region, and locates the initiation codon (PubMed:12435632, PubMed:14600024, PubMed:9732867). Together with eIF1A (EIF1AX), EIF1 facilitates scanning and is essential for start codon recognition on the basis of AUG nucleotide context and location relative to the 5'-cap (PubMed:12435632, PubMed:14600024, PubMed:9732867). Participates to initiation codon selection by influencing the conformation of the 40S ribosomal subunit and the positions of bound mRNA and initiator tRNA; this is possible after its binding to the interface surface of the platform of the 40S ribosomal subunit close to the P-site (PubMed:14600024). Together with eIF1A (EIF1AX), also regulates the opening and closing of the mRNA binding channel, which ensures mRNA recruitment, scanning and the fidelity of initiation codon selection (PubMed:9732867). Continuously monitors and protects against premature and partial base-pairing of codons in the 5'-UTR with the anticodon of initiator tRNA (PubMed:12435632, PubMed:9732867). Together with eIF1A (EIF1AX), acts for ribosomal scanning, promotion of the assembly of 48S complex at the initiation codon (43S PIC becomes 48S PIC after the start codon is reached), and dissociation of aberrant complexes (PubMed:9732867). Interacts with EIF4G1, which in a mutual exclusive interaction associates either with EIF1 or with EIF4E on a common binding site (PubMed:29987188). EIF4G1-EIF1 complex promotes ribosome scanning (on both short and long 5'UTR), leaky scanning (on short 5'UTR) which is the bypass of the initial start codon, and discrimination against cap-proximal AUG (PubMed:29987188). Is probably maintained within the 43S PIC in open conformation thanks to eIF1A-EIF5 interaction (PubMed:24319994). Once the correct start codon is reached, EIF1 is physically excluded from the decoding site, shifting the PIC into the closed conformation and arresting it at the start codon (PubMed:22813744)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P41567/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/EIF1","classification":"Common Essential","n_dependent_lines":1191,"n_total_lines":1208,"dependency_fraction":0.9859271523178808},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"EIF3B","stoichiometry":4.0},{"gene":"CAPRIN1","stoichiometry":0.2},{"gene":"DDX6","stoichiometry":0.2},{"gene":"EIF2S3","stoichiometry":0.2},{"gene":"EIF5","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/EIF1","total_profiled":1310},"omim":[{"mim_id":"619901","title":"EUKARYOTIC TRANSLATION INITIATION FACTOR 1; EIF1","url":"https://www.omim.org/entry/619901"},{"mim_id":"619275","title":"BASIC LEUCINE ZIPPER DOMAIN- AND W2 DOMAIN-CONTAINING PROTEIN 2; BZW2","url":"https://www.omim.org/entry/619275"},{"mim_id":"617941","title":"SHWACHMAN-DIAMOND SYNDROME 2; SDS2","url":"https://www.omim.org/entry/617941"},{"mim_id":"617538","title":"ELONGATION FACTOR-LIKE GTPase 1; EFL1","url":"https://www.omim.org/entry/617538"},{"mim_id":"613709","title":"EUKARYOTIC TRANSLATION INITIATION FACTOR 2D; EIF2D","url":"https://www.omim.org/entry/613709"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EIF1"},"hgnc":{"alias_symbol":["EIF-1","ISO1","A121","SUI1","EIF1A"],"prev_symbol":[]},"alphafold":{"accession":"P41567","domains":[{"cath_id":"3.30.780.10","chopping":"30-110","consensus_level":"high","plddt":89.5237,"start":30,"end":110}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P41567","model_url":"https://alphafold.ebi.ac.uk/files/AF-P41567-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P41567-F1-predicted_aligned_error_v6.png","plddt_mean":80.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EIF1","jax_strain_url":"https://www.jax.org/strain/search?query=EIF1"},"sequence":{"accession":"P41567","fasta_url":"https://rest.uniprot.org/uniprotkb/P41567.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P41567/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P41567"}},"corpus_meta":[{"pmid":"11018020","id":"PMC_11018020","title":"A 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GST pull-down showed eIF1 binds specifically to the p110 subunit of eIF3, explaining eIF1 recruitment to the 40S subunit. No interaction with eIF5 or an initiation-site RNA was detected by NMR.\",\n      \"method\": \"NMR spectroscopy (structure determination); GST pull-down (binding partner identification)\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure combined with pull-down binding assay; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"10228174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"eIF1 participates in a multifactor complex (MFC) with eIF2, eIF3, eIF5, and initiator Met-tRNAi in yeast cell extracts free of 40S ribosomes. eIF5 bridges eIF3 (via NIP1 N-terminus) and eIF2β simultaneously; the NIP1 N-terminus binds both eIF5 and eIF1 concurrently. The MFC is disrupted by the tif5-7A mutation in eIF5's bipartite motif, which also causes temperature-sensitive growth and reduced translation initiation.\",\n      \"method\": \"In vitro binding assays (pull-down); yeast genetic analysis; co-immunoprecipitation from cell extracts\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assays plus genetic confirmation, replicated across multiple mutants\",\n      \"pmids\": [\"11018020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Yeast SUI1 (eIF1) is identical to the p16 subunit of eIF3: anti-SUI1 antisera immunoprecipitate all eIF3 subunits, and anti-eIF3 antisera immunoprecipitate SUI1. eIF3 isolated from a sui1(ts) strain at 37°C lacks SUI1 and fails eIF3 activity in a methionyl-puromycin synthesis assay, demonstrating SUI1 is required for eIF3 activity.\",\n      \"method\": \"Co-immunoprecipitation; SDS-PAGE; in vitro methionyl-puromycin synthesis assay; temperature-sensitive genetic analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP plus functional biochemical assay in the same study\",\n      \"pmids\": [\"8628297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"Genetic characterization in S. cerevisiae established that SUI1 (eIF1) mutations (recessive, temperature-sensitive) suppress loss of the HIS4 AUG start codon, restoring translation initiation at non-AUG codons, placing SUI1 as a component of the translation initiation complex required for AUG start codon recognition.\",\n      \"method\": \"Yeast genetic reversion analysis; complementation tests; suppressor mapping\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — classical genetic epistasis with multiple alleles and codon variants, foundational replicated result\",\n      \"pmids\": [\"2179049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The yeast mof2-1 allele is a novel allele of SUI1 (eIF1). Strains with mof2-1 show increased programmed −1 ribosomal frameshifting and mutant start-site selection. Purified wild-type Mof2p/Sui1p added back to mof2-1 extracts reduced frameshifting to wild-type levels. Human SUI1 expressed in yeast corrects all mof2-1 phenotypes, demonstrating functional conservation and a role for eIF1 in translational accuracy during elongation as well as initiation.\",\n      \"method\": \"Yeast genetics; in vitro frameshifting assay with purified protein add-back; cross-species complementation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro reconstitution of frameshifting phenotype with purified protein, plus cross-species complementation\",\n      \"pmids\": [\"9488467\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The N-terminal domain (NTD) of NIP1/eIF3c directly binds eIF1 and eIF5. Mutations in NIP1-NTD segments reduce eIF1 or eIF5 binding, and a C-terminal NIP1-NTD mutation increases UUG start codon use (Sui− phenotype), which is suppressed by eIF1 overexpression. The NIP1-NTD coordinates eIF1–eIF5 interaction to inhibit GTP hydrolysis at non-AUG codons, and MFC formation stimulates TC recruitment to 40S ribosomes.\",\n      \"method\": \"In vitro pull-down assays; yeast genetic analysis (Sui−/Gcd− phenotypes); overexpression suppression studies\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple binding mutants analyzed with orthogonal genetic and biochemical approaches\",\n      \"pmids\": [\"15485912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Sui− mutations in eIF1 reduce its interaction with 40S subunits in vitro and in vivo. The Sui− mutation 93-97 accelerates eIF1 dissociation from reconstituted preinitiation complexes (PICs) and accelerates Pi release from eIF2, while a hyperaccuracy eIF1A mutation slows eIF1 dissociation. eIF1 dissociation is therefore a critical gating step for start codon selection, modulated by eIF1A. Additional Gcd− eIF1 mutations impair TC loading on 40S subunits or destabilize the MFC.\",\n      \"method\": \"Reconstituted PIC assembly (in vitro); kinetic measurement of eIF1 dissociation and Pi release; yeast genetics; in vivo 40S binding assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with kinetic measurements plus corroborating in vivo genetics\",\n      \"pmids\": [\"17504939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"eIF1 carries two distinct eIF5-binding interfaces: (1) the unstructured N-terminal tail (stimulates cooperative MFC assembly) and (2) a basic/hydrophobic surface area termed KH (includes hydrophobic residues critical for linking eIF1 to the PIC prior to AUG recognition). Mutation of KH is lethal and shows dominant relaxed start codon selection, placing eIF5 as a direct binding partner at the decoding site.\",\n      \"method\": \"NMR-based binding mapping; yeast two-hybrid and pull-down; genetic analysis of KH mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure-guided mutagenesis plus genetic confirmation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"17974565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"eIF1 controls at least two steps in start codon recognition: (1) gating Pi release from eIF2, and (2) triggering the transition from an open, scanning-competent PIC conformation to a stable, closed one upon AUG recognition. eIF1 G107 mutations confer Sui− phenotypes without increasing eIF1 release rate, indicating a role in conformational gating distinct from dissociation. eIF5 antagonizes eIF1 binding to the PIC by competing for a key site.\",\n      \"method\": \"Reconstituted PIC assays; kinetic measurements; yeast genetic analysis; eIF1/eIF5 binding competition experiments\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with kinetic analysis plus genetic validation, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"19751744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Human eIF1 protein translation initiates from an AUG in poor Kozak context, enabling a negative autoregulatory feedback loop: high eIF1 levels increase stringency of start codon selection and thereby suppress translation of its own mRNA. This establishes that eIF1 concentration directly controls the stringency of initiation codon recognition genome-wide.\",\n      \"method\": \"Reporter assays; eIF1 overexpression experiments; mutagenesis of the eIF1 5′-UTR AUG context in human cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reporter and overexpression studies with mechanistic context mutagenesis, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20921384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The C-terminal domain of eIF5 (eIF5-CTD) interacts with eIF1 and eIF2β at partially overlapping surfaces, identified by NMR. eIF5-CTD mutations disrupting these interfaces impair start codon recognition and impede eIF1 release from the PIC, showing that eIF5-CTD binding to eIF2β is required for eIF1 displacement and the open-to-closed PIC switch.\",\n      \"method\": \"NMR spectroscopy (binding surface mapping); site-directed mutagenesis; genetic and biochemical PIC assembly assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR-guided mutagenesis plus functional genetic validation, single lab\",\n      \"pmids\": [\"22813744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The C-terminal tail (CTT) of eIF1A moves closer to eIF5-NTD upon AUG recognition, and this movement is coupled to eIF1 dissociation from the PIC. eIF1 dissociation must be accompanied by eIF1A-CTT movement toward eIF5 to trigger Pi release from eIF2. The same event (tRNAi accommodation in the P site driven by start-codon base pairing) triggers both eIF1 dissociation and eIF1A-CTT repositioning. The C-terminal domain of eIF5 antagonizes eIF1 binding.\",\n      \"method\": \"FRET-based kinetic assays in reconstituted PICs; mutant biochemical analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with FRET kinetics and multiple mutant validations, single lab\",\n      \"pmids\": [\"23293029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"eIF1 β-hairpin loop-1 residues (Arg-33, Lys-37) and helix α1 Lys-60 directly contact 18S rRNA in the 40S·eIF1 complex. Substituting these residues impairs eIF1 binding to 40S·eIF1A complexes in vitro and increases UUG initiation (Sui− phenotype) in vivo, suppressible by eIF1 overexpression or an eIF1A mutation that impedes eIF1 dissociation. The unstructured N-terminal tail of eIF1 also blocks the PIC from rearranging to the closed conformation at non-AUG codons.\",\n      \"method\": \"Crystal structure-guided mutagenesis; in vitro 40S binding assays; yeast genetic analysis (Sui−/Gcd− phenotypes); suppression analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structure-guided mutagenesis with orthogonal in vitro and in vivo validation\",\n      \"pmids\": [\"23893413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Ssu− (suppressor of Sui−) mutations in eIF1 increase eIF1 affinity for 40S subunits in vitro. The strongest-binding variant (D61G) reduces the eIF1 off-rate and destabilizes PIN-state TC binding in reconstituted PICs, establishing that eIF1 dissociation from the 40S subunit is mechanistically required for Met-tRNAi accommodation in the PIN state and that eIF5 and eIF2β promote accuracy by controlling eIF1 dissociation.\",\n      \"method\": \"In vitro 40S binding affinity assays; reconstituted PIC kinetic assays; yeast genetics (Ssu−/Sui− suppression)\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with kinetic off-rate measurements and in vivo genetic validation, single lab\",\n      \"pmids\": [\"24335188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"X-ray crystal structures of the six-subunit yeast eIF3 core combined with cryo-EM, cross-linking/mass spectrometry, and integrative modeling placed eIF1 on the 40S·eIF3 complex. Yeast eIF3 engages 40S in a clamp-like manner, encircling the subunit to position eIF1 and other key initiation factors on opposite ends of the mRNA channel.\",\n      \"method\": \"X-ray crystallography; cryo-EM; cross-linking coupled to mass spectrometry; integrative structure modeling\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal structural methods with functional context, replicated across approaches\",\n      \"pmids\": [\"25171412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Cryo-EM structure of a budding yeast 40S·eIF1·eIF1A·eIF3·eIF3j initiation complex resolved positions of eIF1, eIF1A, eIF3a, eIF3b, eIF3c on the 40S subunit and revealed a direct contact between eIF3j and eIF1A.\",\n      \"method\": \"Cryo-EM structure determination; placement of prior X-ray structures\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structural study with multiple factor placements, single study\",\n      \"pmids\": [\"25664723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"eIF1 stimulates translation initiation from TISU-AUG (short 5′ UTR context) while inhibiting non-TISU-directed initiation. eIF4GI shares this dual activity and directly interacts with eIF1. eIF4F is released upon 48S formation on TISU mRNA. Purified 48S preinitiation complex is sufficient for initiation via TISU AUG when preceded by a short 5′ UTR, revealing a specialized mechanism enabling mitochondrial gene translation under energy stress.\",\n      \"method\": \"In vitro 48S reconstitution; purified factor assays; co-immunoprecipitation (eIF4GI–eIF1 interaction); translation reporter assays in AMPK-KO cells\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus co-IP and cell-based validation, single lab, multiple methods\",\n      \"pmids\": [\"25738462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-EM structure of a yeast 48S PIC at 3.0 Å shows eIF5-NTD bound to the 40S subunit at the position vacated by eIF1. eIF5-NTD interacts with and accommodates Met-tRNAi in a more PIN-like orientation. Substitutions in eIF5 residues contacting tRNAi alter UUG initiation in vivo and PIC open/closed state in vitro, demonstrating that eIF5 directly stabilizes the codon:anticodon duplex after eIF1 departure.\",\n      \"method\": \"Cryo-EM (3.0 Å); site-directed mutagenesis; in vitro PIC conformation assays; yeast genetic analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM with mutagenesis and orthogonal functional validation\",\n      \"pmids\": [\"30475211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"eIF4G1 exists in two mutually exclusive complexes: one with eIF4E and one with eIF1. Using an eIF1 mutant impaired in eIF4G1 binding, eIF1–eIF4G1 interaction was shown to be important for leaky scanning and for avoiding cap-proximal initiation. eIF4E–eIF4G1 antagonizes the scanning promoted by eIF1–eIF4G1. The eIF4G1 transition from eIF4E to eIF1 binding is proposed to accompany the 43S ribosome's move from the cap to the scanning mode.\",\n      \"method\": \"Co-immunoprecipitation; eIF1 binding-site mutants; translation reporter assays; interaction mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and functional mutant analysis, single lab\",\n      \"pmids\": [\"29987188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"eIF1 Loop 2 is juxtaposed with the Met-tRNAi D loop in the PIN state (from PIC structures). Ala substitutions in Loop 2 (D71A, M74A) increase initiation at UUG codons and AUGs in poor context, and stabilize TC binding to 48S PICs with UUG mRNA, without affecting eIF1 affinity for 40S subunits or POUT-mode TC loading. Arg substitutions convert the predicted Loop 2–tRNAi clash to an electrostatic attraction, further stabilizing PIN state. Thus Loop 2–D loop interactions specifically impede Met-tRNAi accommodation in PIN state.\",\n      \"method\": \"Site-directed mutagenesis; in vitro 48S PIC reconstitution; TC binding assays; yeast genetic analysis (UUG initiation, Kozak context reporters)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structure-guided mutagenesis, in vitro reconstitution, and in vivo genetic validation in single study\",\n      \"pmids\": [\"29666249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ribosome profiling of a yeast eIF1-L96P variant (weakened PIC binding) shows genome-wide increases in translation of uORFs initiating at near-cognate codons (NCCs) or AUGs in poor Kozak context, frequently reducing downstream CDS translation. eIF1 also controls the ratio of mitochondrial protein isoforms translated from NCC versus AUG start codons (e.g., GRS1, ALA1). Thus eIF1 discriminates against suboptimal start codons throughout the translatome.\",\n      \"method\": \"Ribosome profiling (genome-wide); eIF1 mutant (L96P) yeast strain\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ribosome profiling with defined eIF1 mutant, single lab\",\n      \"pmids\": [\"31915290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Small-molecule inhibitors of eIF4G1–eIF1 interaction (i14G1-10 and i14G1-12) directly bind eIF4G1, inhibit translation in vitro and in cells in an eIF4G1-level-dependent manner, and phenocopy eIF1/eIF4G1 perturbations on start codon stringency. i14G1s activate ER/UPR stress-response genes through enhanced 5′ UTR near-cognate AUG translation, independently of eIF2α phosphorylation. eIF4G1–eIF1 interaction is itself negatively regulated by ER stress and mTOR inhibition.\",\n      \"method\": \"In vitro translation assays; translatome profiling; small-molecule–protein binding assays; reporter assays in cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological perturbation plus translatome profiling, single lab, multiple methods\",\n      \"pmids\": [\"35857873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"During mammalian mitosis, a nuclear pool of eIF1 is released into the cytoplasm upon nuclear envelope breakdown, increasing eIF1–40S ribosome association and globally enhancing stringency of start-codon selection. Low-efficiency initiation sites are preferentially repressed in mitosis. Selectively depleting the nuclear pool of eIF1 eliminates the mitotic change in translational stringency, alters protein isoform synthesis, and increases cell death and decreases mitotic slippage following anti-mitotic drug treatment.\",\n      \"method\": \"Transcriptome-wide translation initiation site profiling; nuclear pool-specific eIF1 depletion; cell viability assays; co-sedimentation (eIF1–40S interaction)\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide initiation profiling plus targeted nuclear pool depletion with defined functional consequence, replicated in preprint and peer-reviewed form\",\n      \"pmids\": [\"39443796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SARS-CoV-2 Nsp1 cooperates with EIF1 and EIF1A to selectively enhance translation of viral RNA. When EIF1/EIF1A are depleted, more ribosomes initiate from a conserved upstream CUG codon in viral mRNAs, shifting translation to uORF1 and reducing main ORF translation. Replacing the upstream CUG with AUG strongly inhibits main ORF translation independently of Nsp1, EIF1, or EIF1A, demonstrating that EIF1/EIF1A normally suppress upstream CUG usage to favor downstream AUG selection.\",\n      \"method\": \"Ribosome profiling; EIF1/EIF1A knockdown; reporter assays; start-codon mutagenesis\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ribosome profiling plus KD and reporter mutagenesis, single lab\",\n      \"pmids\": [\"38335237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Single-molecule fluorescence analysis of in vitro reconstituted human translation initiation shows eIF1 loads onto mRNAs as part of the 43S complex and departs rapidly (~2 s) in a start-site-dependent manner; alternative start sites and longer 5′ UTRs delay departure. After initial departure, eIF1 transiently and repeatedly samples initiation complexes, with more prolonged sampling at alternative start sites. eIF5 only transiently binds late in initiation immediately before eIF5B association, and its binding requires a start site and is inhibited by alternative start sites.\",\n      \"method\": \"Single-molecule fluorescence (TIRF); in vitro reconstituted human initiation; knockdown and overexpression in human cells\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule reconstitution with cell-based validation, single lab, preprint\",\n      \"pmids\": [\"39026837\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The HEAT domain of yeast eIF4G2 interacts directly with eIF1, and eIF1 can simultaneously bind eIF4G and eIF3c in vitro. The eIF4G HEAT domain mutations reduce binding to eIF1 and eIF5, increase UUG initiation, and the sui1-1 eIF1 mutation reduces the eIF4G–eIF1 interaction. eIF4G HEAT domain binding to eIF1 is thus important for maintaining scanning PIC integrity and AUG fidelity.\",\n      \"method\": \"In vitro pull-down; genetic suppression analysis; yeast genetic analysis (UUG initiation reporters)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding plus corroborating genetics, single lab\",\n      \"pmids\": [\"12861028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human A121/SUI1 (eIF1) expression is induced at the mRNA level by genotoxic and ER stress in a p53-independent manner. Expression of human A121 in yeast complemented the sui1 mutant phenotype, confirming its identity as a functional eIF1 ortholog. Two mRNA transcripts (1.35 kb and 0.65 kb) with a common coding region but different 3′ UTRs are differentially regulated by stress.\",\n      \"method\": \"Subtractive PCR; yeast complementation; Northern blot analysis; stress-induction experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation plus differential expression analysis, single lab\",\n      \"pmids\": [\"10347211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"mof2-1 (a SUI1/eIF1 allele) affects the nonsense-mediated mRNA decay (NMD) pathway in addition to translation initiation and frameshifting fidelity. Human SUI1 expressed in yeast activates NMD, suggesting eIF1 functions as a general modulator in multiple aspects of translation and mRNA turnover.\",\n      \"method\": \"Yeast genetic analysis; NMD reporter assays; cross-species complementation\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reporter assays and complementation, single lab\",\n      \"pmids\": [\"10376878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NMR backbone assignments of the human eIF3c fragment (residues 166–266) that encompasses the reported eIF1-binding site show this region is intrinsically disordered in solution, with short segments of modest α-helical or β-strand propensity. Three conserved FLKK motifs are located at junctions of transient structural elements. A small helix within this region contacts eIF1 in cryo-EM PIC structures. These assignments provide a foundation for mapping the eIF1-binding surface on eIF3c.\",\n      \"method\": \"NMR spectroscopy (1H–15N HSQC; backbone assignments; chemical shift index analysis)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structural characterization (NMR assignments only) without functional interaction validation; preprint\",\n      \"pmids\": [\"bio_10.1101_2025.09.13.675972\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"EIF1 (SUI1/A121) is a universally conserved ~12 kDa translation initiation factor that binds the 40S ribosomal subunit (via contacts with 18S rRNA and eIF3c/p110) as part of a multifactor complex (MFC) with eIF2, eIF3, eIF5, and Met-tRNAi; it stabilizes the open, scanning-competent conformation of the preinitiation complex (PIC) by blocking Met-tRNAi accommodation in the PIN state, and its dissociation from the PIC upon AUG codon recognition—stimulated by eIF5 and eIF2β and modulated by eIF1A—is the critical gate that allows irreversible Pi release from eIF2·GDP·Pi, conversion to the closed PIC conformation, and stable 48S complex formation; additionally, a nuclear pool of eIF1 is released during mitosis to globally increase the stringency of start-codon selection, eIF1 autoregulates its own translation through a poor-context AUG, and it cooperates with eIF4GI to control scanning-dependent versus scanning-independent initiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EIF1 (SUI1) is a universally conserved small translation initiation factor that enforces the fidelity of start-codon selection during ribosomal scanning [#3, #6]. It assembles into a multifactor complex with eIF2, eIF3, eIF5, and initiator Met-tRNAi, where the N-terminal domain of eIF3c (NIP1) binds eIF1 and eIF5 concurrently to coordinate their action and stimulate ternary complex recruitment to the 40S subunit [#1, #2, #5]. On the 40S subunit, eIF1 contacts 18S rRNA via β-hairpin loop-1 and helix α1 residues and stabilizes the open, scanning-competent conformation of the preinitiation complex, while its β-hairpin Loop 2 sterically clashes with the Met-tRNAi D loop to block tRNAi accommodation in the PIN state at non-AUG and poor-context codons [#12, #19]. Recognition of an AUG codon drives eIF1 dissociation from the PIC—a critical gating step that permits irreversible Pi release from eIF2 and the open-to-closed conformational switch; eIF5 and eIF2β promote accuracy by controlling this dissociation, eIF1A modulates its rate, and the eIF5 N-terminal domain then occupies the site vacated by eIF1 to stabilize the codon:anticodon duplex [#6, #8, #10, #11, #13, #17]. Because eIF1 concentration sets the genome-wide stringency of initiation, eIF1 autoregulates its own synthesis through a poor-context AUG, and its loss broadly de-represses translation at upstream near-cognate and poor-context start codons [#9, #20]. Beyond the core scanning machinery, eIF1 cooperates with eIF4G1 in a complex mutually exclusive with eIF4E to govern leaky scanning and specialized initiation modes including TISU-AUG translation under energy stress [#16, #18], and a nuclear pool released at mitotic nuclear-envelope breakdown raises start-codon stringency to control isoform output and mitotic cell fate [#22].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established eIF1 as a genetic determinant of AUG start-codon recognition, answering whether a dedicated factor enforces initiation-codon identity.\",\n      \"evidence\": \"Yeast SUI1 suppressor genetics restoring initiation at non-AUG codons at the HIS4 locus\",\n      \"pmids\": [\"2179049\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of codon discrimination undefined\", \"No biochemical or structural basis for the genetic phenotype\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Linked eIF1 physically and functionally to the eIF3 complex, defining how it is recruited to the initiation machinery.\",\n      \"evidence\": \"Reciprocal co-IP of SUI1 with eIF3 subunits plus methionyl-puromycin synthesis assay in a sui1(ts) strain\",\n      \"pmids\": [\"8628297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and direct vs indirect contacts not resolved\", \"Did not identify which eIF3 subunit binds eIF1\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Provided the eIF1 fold and its direct eIF3 binding partner, and showed stress-responsive, conserved expression of the human ortholog.\",\n      \"evidence\": \"NMR solution structure with GST pull-down to eIF3 p110; human A121/SUI1 yeast complementation and stress-induction Northern blots\",\n      \"pmids\": [\"10228174\", \"10347211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of eIF1 bound to the 40S subunit\", \"Functional consequence of stress induction on the translatome unmeasured\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the multifactor complex architecture, showing eIF5/NIP1 bridges eIF1 to eIF2 and eIF3 prior to ribosome loading.\",\n      \"evidence\": \"Reciprocal in vitro binding assays and yeast genetics of eIF5 motif mutants in ribosome-free extracts\",\n      \"pmids\": [\"11018020\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial arrangement on the 40S not yet established\", \"Order of assembly events unresolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Connected eIF1 to the cap-binding/scanning apparatus via eIF4G, implicating it in PIC integrity beyond the MFC core.\",\n      \"evidence\": \"In vitro pull-down of eIF4G HEAT domain with eIF1 plus UUG-initiation genetics\",\n      \"pmids\": [\"12861028\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab biochemistry\", \"Functional separation of eIF4G–eIF1 from eIF4G–eIF5 binding incomplete\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Showed the eIF3c/NIP1 N-terminal domain coordinates eIF1–eIF5 to suppress GTP hydrolysis at non-AUG codons.\",\n      \"evidence\": \"NIP1-NTD binding mutants with Sui- genetics and eIF1-overexpression suppression in yeast\",\n      \"pmids\": [\"15485912\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct effect on hydrolysis kinetics not measured in this study\", \"Conformational coupling to tRNAi unaddressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that eIF1 dissociation from the PIC is the rate-limiting gate for Pi release and start-codon fidelity, and mapped its eIF5-binding interfaces.\",\n      \"evidence\": \"Reconstituted PIC kinetics of Sui-/Ssu- mutants plus NMR-guided mapping of N-tail and KH eIF5 interfaces\",\n      \"pmids\": [\"17504939\", \"17974565\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational vs dissociation contributions not fully separated\", \"Precise structural location of eIF1 on the PIC unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved that eIF1 controls two distinct steps—Pi-release gating and the open-to-closed PIC transition—and that eIF5 competes for its binding site.\",\n      \"evidence\": \"Reconstituted PIC kinetics of G107 mutants plus eIF1/eIF5 binding competition\",\n      \"pmids\": [\"19751744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic basis of the competition not visualized\", \"Coupling to tRNAi accommodation inferred indirectly\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined how the eIF5 C-terminal domain triggers eIF1 displacement by engaging eIF2β, mechanistically linking eIF5 to the conformational switch.\",\n      \"evidence\": \"NMR surface mapping of eIF5-CTD interfaces with eIF1 and eIF2β plus PIC assembly assays\",\n      \"pmids\": [\"22813744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Temporal sequence relative to eIF1A movement unresolved at this stage\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected eIF1 release to specific 18S rRNA contacts, eIF1A-CTT repositioning, and PIN-state tRNAi accommodation, unifying the gating mechanism.\",\n      \"evidence\": \"Structure-guided mutagenesis of eIF1–18S contacts, FRET kinetics of eIF1A-CTT movement, and 40S off-rate measurements of Ssu- variants in reconstituted PICs\",\n      \"pmids\": [\"23293029\", \"23893413\", \"24335188\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the closed transition state still lacking\", \"How AUG base-pairing energy is transmitted to eIF1 not fully defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Placed eIF1 on the 40S·eIF3 complex within a clamp-like eIF3 architecture, giving a structural framework for factor positioning.\",\n      \"evidence\": \"X-ray crystallography, cryo-EM, cross-linking/MS and integrative modeling of the yeast eIF3 core on 40S\",\n      \"pmids\": [\"25171412\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Resolution insufficient for atomic eIF1–rRNA contacts\", \"tRNAi and eIF2 not resolved in this assembly\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided a cryo-EM map of the 40S·eIF1·eIF1A·eIF3·eIF3j complex and revealed an eIF3j–eIF1A contact, and showed eIF1's dual control over TISU vs non-TISU initiation via eIF4GI.\",\n      \"evidence\": \"Cryo-EM of a yeast initiation complex; in vitro 48S reconstitution, eIF4GI–eIF1 co-IP and reporter assays in AMPK-KO cells\",\n      \"pmids\": [\"25664723\", \"25738462\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism coupling eIF4GI–eIF1 to TISU specificity incompletely defined\", \"Mitochondrial gene relevance based on cellular reporters\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the structural endpoint of eIF1 departure (eIF5-NTD occupying its site), the steric basis of PIN-state discrimination via Loop 2, and the eIF4G1 partner-switch controlling scanning.\",\n      \"evidence\": \"3.0 Å cryo-EM of 48S PIC with eIF5 mutagenesis; Loop 2 mutagenesis with 48S reconstitution; eIF1/eIF4E mutually exclusive eIF4G1 complexes by co-IP\",\n      \"pmids\": [\"30475211\", \"29666249\", \"29987188\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"eIF4G1 partner-switch model is single-lab and partly inferred\", \"In vivo dynamics of the switch during scanning not directly observed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated genome-wide that eIF1 level/binding sets translatome-wide discrimination against suboptimal start codons, including mitochondrial isoform ratios.\",\n      \"evidence\": \"Ribosome profiling of the eIF1-L96P weakened-binding yeast variant\",\n      \"pmids\": [\"31915290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian translatome consequences extrapolated from yeast\", \"Codon-context determinants of sensitivity not exhaustively mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed the eIF4G1–eIF1 interaction is a druggable node regulated by ER stress and mTOR that shapes near-cognate uORF translation independently of eIF2α phosphorylation.\",\n      \"evidence\": \"Small-molecule inhibitors of eIF4G1–eIF1, in vitro translation, translatome profiling and reporter assays in cells\",\n      \"pmids\": [\"35857873\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab pharmacology\", \"Direct binding site of inhibitors on eIF4G1 vs eIF1 contributions not crystallographically defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a nuclear eIF1 pool that, upon mitotic nuclear-envelope breakdown, raises start-codon stringency and governs isoform output and mitotic cell fate; and that eIF1/eIF1A suppress upstream CUG usage exploited during SARS-CoV-2 infection.\",\n      \"evidence\": \"Initiation-site profiling with nuclear-pool-specific eIF1 depletion and viability assays; ribosome profiling with EIF1/EIF1A knockdown and start-codon mutagenesis in infection\",\n      \"pmids\": [\"39443796\", \"38335237\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of nuclear sequestration and release not molecularly defined\", \"Generality of CUG suppression beyond viral mRNAs untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Single-molecule reconstitution captured eIF1 loading, rapid start-site-dependent departure, and repeated sampling, refining the kinetic model of its gating role.\",\n      \"evidence\": \"Single-molecule TIRF of reconstituted human initiation with cell-based validation (preprint)\",\n      \"pmids\": [\"39026837\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, single lab\", \"Repeated-sampling behavior awaits independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the nuclear eIF1 pool is established, retained, and released, and how the eIF1-binding region of disordered eIF3c folds upon engaging eIF1, remain unresolved.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No molecular mechanism for nuclear eIF1 sequestration\", \"eIF3c eIF1-binding surface characterized only as disordered backbone assignments (preprint), without bound-state structure\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [12, 0]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [6, 8, 9, 20]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 13, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [12, 14, 15, 17]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [22]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-72613\", \"supporting_discovery_ids\": [3, 6, 9]}\n    ],\n    \"complexes\": [\n      \"multifactor complex (eIF1·eIF2·eIF3·eIF5·Met-tRNAi)\",\n      \"43S/48S preinitiation complex\",\n      \"40S·eIF1·eIF1A·eIF3·eIF3j complex\"\n    ],\n    \"partners\": [\n      \"EIF3C\",\n      \"EIF5\",\n      \"EIF1AX\",\n      \"EIF2S2\",\n      \"EIF4G1\",\n      \"EIF3A\",\n      \"EIF3B\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}