| 1999 |
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. |
NMR spectroscopy (structure determination); GST pull-down (binding partner identification) |
The EMBO journal |
High |
10228174
|
| 2000 |
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. |
In vitro binding assays (pull-down); yeast genetic analysis; co-immunoprecipitation from cell extracts |
Genes & development |
High |
11018020
|
| 1996 |
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. |
Co-immunoprecipitation; SDS-PAGE; in vitro methionyl-puromycin synthesis assay; temperature-sensitive genetic analysis |
Molecular and cellular biology |
High |
8628297
|
| 1990 |
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. |
Yeast genetic reversion analysis; complementation tests; suppressor mapping |
Genetics |
High |
2179049
|
| 1998 |
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. |
Yeast genetics; in vitro frameshifting assay with purified protein add-back; cross-species complementation |
Molecular and cellular biology |
High |
9488467
|
| 2004 |
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. |
In vitro pull-down assays; yeast genetic analysis (Sui−/Gcd− phenotypes); overexpression suppression studies |
Molecular and cellular biology |
High |
15485912
|
| 2007 |
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. |
Reconstituted PIC assembly (in vitro); kinetic measurement of eIF1 dissociation and Pi release; yeast genetics; in vivo 40S binding assays |
Genes & development |
High |
17504939
|
| 2007 |
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. |
NMR-based binding mapping; yeast two-hybrid and pull-down; genetic analysis of KH mutants |
The Journal of biological chemistry |
High |
17974565
|
| 2009 |
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. |
Reconstituted PIC assays; kinetic measurements; yeast genetic analysis; eIF1/eIF5 binding competition experiments |
Journal of molecular biology |
High |
19751744
|
| 2010 |
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. |
Reporter assays; eIF1 overexpression experiments; mutagenesis of the eIF1 5′-UTR AUG context in human cells |
Proceedings of the National Academy of Sciences of the United States of America |
High |
20921384
|
| 2012 |
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. |
NMR spectroscopy (binding surface mapping); site-directed mutagenesis; genetic and biochemical PIC assembly assays |
Cell reports |
High |
22813744
|
| 2013 |
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. |
FRET-based kinetic assays in reconstituted PICs; mutant biochemical analysis |
The Journal of biological chemistry |
High |
23293029
|
| 2013 |
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. |
Crystal structure-guided mutagenesis; in vitro 40S binding assays; yeast genetic analysis (Sui−/Gcd− phenotypes); suppression analysis |
The Journal of biological chemistry |
High |
23893413
|
| 2013 |
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. |
In vitro 40S binding affinity assays; reconstituted PIC kinetic assays; yeast genetics (Ssu−/Sui− suppression) |
RNA (New York, N.Y.) |
High |
24335188
|
| 2014 |
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. |
X-ray crystallography; cryo-EM; cross-linking coupled to mass spectrometry; integrative structure modeling |
Cell |
High |
25171412
|
| 2015 |
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. |
Cryo-EM structure determination; placement of prior X-ray structures |
Nature structural & molecular biology |
High |
25664723
|
| 2015 |
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. |
In vitro 48S reconstitution; purified factor assays; co-immunoprecipitation (eIF4GI–eIF1 interaction); translation reporter assays in AMPK-KO cells |
Cell metabolism |
High |
25738462
|
| 2018 |
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. |
Cryo-EM (3.0 Å); site-directed mutagenesis; in vitro PIC conformation assays; yeast genetic analysis |
eLife |
High |
30475211
|
| 2018 |
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. |
Co-immunoprecipitation; eIF1 binding-site mutants; translation reporter assays; interaction mapping |
Molecular and cellular biology |
Medium |
29987188
|
| 2018 |
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. |
Site-directed mutagenesis; in vitro 48S PIC reconstitution; TC binding assays; yeast genetic analysis (UUG initiation, Kozak context reporters) |
Proceedings of the National Academy of Sciences of the United States of America |
High |
29666249
|
| 2020 |
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. |
Ribosome profiling (genome-wide); eIF1 mutant (L96P) yeast strain |
RNA (New York, N.Y.) |
High |
31915290
|
| 2022 |
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. |
In vitro translation assays; translatome profiling; small-molecule–protein binding assays; reporter assays in cells |
Proceedings of the National Academy of Sciences of the United States of America |
Medium |
35857873
|
| 2024 |
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. |
Transcriptome-wide translation initiation site profiling; nuclear pool-specific eIF1 depletion; cell viability assays; co-sedimentation (eIF1–40S interaction) |
Nature |
High |
39443796
|
| 2024 |
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. |
Ribosome profiling; EIF1/EIF1A knockdown; reporter assays; start-codon mutagenesis |
PLoS pathogens |
Medium |
38335237
|
| 2024 |
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. |
Single-molecule fluorescence (TIRF); in vitro reconstituted human initiation; knockdown and overexpression in human cells |
bioRxivpreprint |
Medium |
39026837
|
| 2003 |
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. |
In vitro pull-down; genetic suppression analysis; yeast genetic analysis (UUG initiation reporters) |
Molecular and cellular biology |
Medium |
12861028
|
| 1999 |
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. |
Subtractive PCR; yeast complementation; Northern blot analysis; stress-induction experiments |
The Journal of biological chemistry |
Medium |
10347211
|
| 1999 |
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. |
Yeast genetic analysis; NMD reporter assays; cross-species complementation |
RNA (New York, N.Y.) |
Medium |
10376878
|
| 2025 |
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. |
NMR spectroscopy (1H–15N HSQC; backbone assignments; chemical shift index analysis) |
bioRxivpreprint |
Low |
bio_10.1101_2025.09.13.675972
|