EEF1E1

EEF1E1 (AIMP3/p18) is a multifunctional scaffolding protein that bridges translation initiation, genome surveillance, and the p53 tumor-suppressor response (PMID:16849534, PMID:22867704). Within the translational machinery it specifically binds charged initiator Met-tRNA(i)(Met), discriminating it from elongator and uncharged species, and together with methionyl-tRNA synthetase (MetRS) non-competitively engages eIF2γ to transfer Met-tRNA(i)(Met) to the eIF2 complex for initiation (PMID:22867704). Its crystal structure resolves an N-terminal and a five-helix-bundle C-terminal domain, the latter carrying the binding surface required for ATM interaction and p53 activation (PMID:18343821). Through differential activation of ATM and ATR, EEF1E1 couples oncogenic and DNA-damage stress to p53, acting as a tumor suppressor whose allelic loss permits oncogene-induced transformation and chromosomal instability (PMID:16849534, PMID:18343821). It is additionally required for homologous-recombination repair of DNA double-strand breaks, with its loss causing accumulation of breaks, reduced RPA/Rad51 foci, and p53-dependent loss of stem-cell self-renewal (PMID:30250065, PMID:30302025). A distinct activity is its proofreading role: in cardiomyocytes EEF1E1 is essential for MetRS-mediated homocysteine editing—independent of aminoacylation or global translation—and its loss causes homocysteine accumulation, ROS, protein aggregation, and lethal cardiomyopathy (PMID:40562875). EEF1E1 overexpression also drives proteasome-dependent degradation of mature lamin A, producing nuclear morphology defects, cellular senescence, and a progeroid phenotype (PMID:20726853).

1. 2006 Medium

   Established that EEF1E1/AIMP3 functions as a stress-responsive tumor suppressor by linking oncogenic signaling to p53 activation, answering whether this aminoacyl-tRNA synthetase complex component has a role beyond translation.

   Evidence Genetic knockdown and heterozygous mouse cells with oncogene transformation and chromosomal instability assays

   PMID:16849534

   Open questions at the time

   • Did not define the structural basis of ATM/ATR engagement
   • Direct vs indirect activation of ATM/ATR not resolved
2. 2008 High

   Resolved the domain architecture of AIMP3 and pinpointed the C-terminal surface required for ATM binding and p53 activation, providing the structural basis for its tumor-suppressive activity.

   Evidence 2.0 Å X-ray crystallography with site-directed mutagenesis, ATM co-immunoprecipitation, and p53 activation assays

   PMID:18343821

   Open questions at the time

   • No co-structure with ATM
   • Does not address translation or HR functions
3. 2010 Medium

   Identified a senescence-promoting activity whereby AIMP3 selectively destabilizes mature lamin A, connecting the protein to nuclear architecture and aging.

   Evidence AIMP3 transgenic mice, western blotting, proteasome inhibition, and senescence/nuclear morphology assays

   PMID:20726853

   Open questions at the time

   • Mechanism by which AIMP3 targets lamin A to the proteasome unidentified
   • Whether endogenous AIMP3 regulates lamin A unknown
4. 2012 High

   Defined the molecular function of AIMP3 in translation initiation by showing it binds initiator Met-tRNA with strict specificity and channels it to eIF2 via MetRS and eIF2γ.

   Evidence In vitro filter-binding and pull-down assays with siRNA knockdown and protein synthesis measurement

   PMID:22867704

   Open questions at the time

   • Structural basis of tRNA discrimination not solved
   • In vivo requirement for initiation not tested in this study
5. 2018 Medium

   Established AIMP3 as a component of homologous-recombination DSB repair acting upstream of p53, explaining the chromosomal instability seen on its loss.

   Evidence Conditional knockout mESCs and adult mice, γH2AX/COMET assays, RPA/Rad51 foci, HR assays, and p53 epistasis

   PMID:30250065 PMID:30302025

   Open questions at the time

   • Direct molecular partner within the HR machinery not identified
   • Whether HR role is separable from translation/p53 roles unclear
6. 2019 Medium

   Linked AIMP3 to metabolic control of stem-cell senescence, showing it enhances mitochondrial respiration and suppresses autophagy under regulation by HIF1α and Notch3.

   Evidence RNA-seq, gain/loss-of-function in MSCs, mitochondrial respiration and autophagy flux assays with HIF1α/Notch3 manipulation

   PMID:30706629

   Open questions at the time

   • Molecular mechanism connecting AIMP3 to mitochondrial respiration not defined
   • Causal link to autophagy machinery associative
7. 2021 Low

   Extended the lamin A/senescence and p53-dependent tumor-suppressor models to vascular smooth muscle and lung adenocarcinoma, including regulation by miR-96-5p.

   Evidence AIMP3 overexpression in HASMCs and lung cancer cells, miR-96-5p targeting, p53 dependency, and xenograft assays

   PMID:33538115 PMID:34274427

   Open questions at the time

   • Largely overexpression-based without mechanistic dissection
   • miR-96-5p–AIMP3–p53 axis not validated by endogenous loss-of-function
8. 2023 Low

   Reported a context-dependent pro-tumor role in glioma and hepatocellular carcinoma via PTEN/AKT suppression and condensate formation, contrasting with the tumor-suppressor role in other tissues.

   Evidence siRNA knockdown, cell-cycle and proliferation assays, PTEN/AKT western blotting, LLPS visualization with 1,6-hexanediol, and xenografts

   PMID:37589446 PMID:39884379

   Open questions at the time

   • Direct mechanism of PTEN downregulation not shown
   • Causal basis and biophysical determinants of phase separation unresolved
9. 2024 Low

   Implicated EEF1E1 in myoblast senescence upstream of a SIRT1-autophagy axis, broadening its senescence role to skeletal muscle.

   Evidence siRNA knockdown and recombinant protein treatment with SA-β-gal, p21/p53/SIRT1 blotting, autophagy markers, and aged mouse model

   PMID:39276001

   Open questions at the time

   • Mechanistic link to SIRT1/autophagy is associative
   • Whether effect is translation- or p53-mediated not separated
10. 2025 High

    Revealed a translation-independent proofreading function: AIMP3 is essential for MetRS homocysteine editing, with loss causing mistranslation-driven lethal cardiomyopathy, redefining its role within the synthetase complex.

    Evidence Cardiomyocyte-specific conditional knockout mice with aminoacylation/localization controls, homocysteine editing, ROS, aggregation, and mitochondrial assays

    PMID:40562875

    Open questions at the time

    • Structural basis for how AIMP3 enables MetRS editing not defined
    • Relevance of editing function to non-cardiac tissues untested

• How AIMP3's distinct activities—initiator-tRNA channeling, MetRS proofreading, ATM/p53 signaling, HR repair, lamin A turnover, and context-dependent tumor roles—are partitioned and coordinated within a single protein remains unresolved.
• No unifying model linking the cytoplasmic synthetase functions to nuclear p53/HR functions
• Determinants of tumor-suppressor versus pro-tumor behavior across tissues unknown