Affinage

EIF2B3

Translation initiation factor eIF2B subunit gamma · UniProt Q9NR50

Length
452 aa
Mass
50.2 kDa
Annotated
2026-06-09
13 papers in source corpus 5 papers cited in narrative 5 extracted findings
Cross-family judge vs UniProt: UniProt preferred faithfulness: 4/4 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

EIF2B3 (eIF2Bγ) is a subunit of the guanine nucleotide exchange factor eIF2B that supports cap-independent, HCV IRES-mediated translation and, when disrupted, perturbs glial development and cellular stress tolerance (PMID:10900014, PMID:33517449). In hepatocyte models, EIF2B3 acts as a cofactor required for HCV IRES-driven core protein synthesis and for chronic HCV replication, selectively affecting IRES translation without impairing cap-dependent translation or cell growth (PMID:10900014, PMID:23207339). Disease-associated EIF2B3 mutation impairs oligodendrocyte survival under ER stress by depressing autophagy flux, with reduced Atg3 and Atg7 expression, and pharmacological autophagy induction rescues mutant cell viability, placing EIF2B3 upstream of autophagy-mediated ER stress tolerance (PMID:26625702). In vivo, CRISPR ablation of eif2b3 in zebrafish disrupts myelin development and glial differentiation, induces integrated stress response genes, and drives ectopic VEGF-dependent angiogenesis reversible by VEGF receptor inhibition, a model that validated pathogenicity of human EIF2B3 disease variants (PMID:33517449). Beyond these findings, the biochemical mechanism of EIF2B3 within the eIF2B nucleotide exchange complex has not been directly characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 2000 Medium

    Established that EIF2B3 is specifically required for HCV IRES-mediated translation, distinguishing it from general cap-dependent initiation in this context.

    Evidence Ribozyme library screen in HeLa cells with a bicistronic HCV IRES reporter, validated with multiple independent ribozymes

    PMID:10900014

    Open questions at the time
    • Does not define the biochemical step at which EIF2B3 acts on IRES translation
    • No reconstitution or direct binding to the IRES complex
  2. 2012 Medium

    Extended the HCV requirement from reporter translation to functional viral replication, confirming EIF2B3 supports chronic infection in hepatocytes.

    Evidence siRNA knockdown in Huh7-HCV cells with qPCR and western blot readouts for HCV RNA and core protein

    PMID:23207339

    Open questions at the time
    • Single lab, single study
    • Mechanism linking EIF2B3 to viral replication versus translation not separated
  3. 2015 Medium

    Linked a disease-associated EIF2B3 mutation to oligodendrocyte vulnerability via autophagy, framing EIF2B3 as upstream of autophagy-mediated ER stress tolerance.

    Evidence Transfection of mutant vs wild-type EIF2B3 in an oligodendrocyte cell line with viability, apoptosis, autophagy flux, and pharmacological induction/inhibition

    PMID:26625702

    Open questions at the time
    • Mechanism connecting EIF2B3 loss to reduced Atg3/Atg7 unknown
    • Single mutation tested in a cell line
  4. 2021 Medium

    Provided in vivo evidence that EIF2B3 loss disrupts myelination and glial differentiation while activating the integrated stress response and VEGF-driven angiogenesis, and validated human variant pathogenicity.

    Evidence Two independent CRISPR zebrafish alleles, SU5416 pharmacological rescue, and complementation of human disease variants

    PMID:33517449

    Open questions at the time
    • Causal chain from ISR activation to VEGF induction not resolved
    • Cell-type-specific contributions not dissected
  5. 2021 Low

    Identified a C-terminally truncated EIF2B3 isoform from intronic polyadenylation predicted to alter EIF2:EIF2B complex equilibrium, implicating isoform-level regulation of complex stability.

    Evidence Transcript and protein detection of the IPA isoform plus computational structural modeling of EIF2Bγ–EIF2γ interactions

    PMID:34796993

    Open questions at the time
    • Interaction effect is computational with no direct binding assay
    • Functional consequence of the isoform on translation not measured

Open questions

Synthesis pass · forward-looking unresolved questions
  • The direct biochemical role of EIF2B3 within the eIF2B guanine nucleotide exchange complex and its molecular link to ER stress and angiogenesis remain undefined.
  • No direct enzymatic or binding mechanism established
  • Connection between translation initiation role and downstream stress/myelin phenotypes unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Partners
EIF2S3
Complex memberships
eIF2B

Evidence

Reading pass · 5 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 eIF2Bγ (EIF2B3) was identified as a cofactor required for hepatitis C virus IRES-mediated translation. Ribozymes targeting EIF2B3 mRNA inhibited HCV IRES-driven translation of core protein without affecting cap-dependent translation or cell growth, establishing EIF2B3 as specifically involved in HCV IRES function. Functional genomics ribozyme library screen in HeLa cells with bicistronic HCV IRES reporter; validation with independent ribozymes targeting multiple sites in EIF2B3 mRNA Proceedings of the National Academy of Sciences of the United States of America Medium 10900014
2012 siRNA-mediated knockdown of eIF2Bγ (EIF2B3) in Huh7 cells chronically infected with HCV inhibited HCV replication and reduced core protein expression, confirming EIF2B3 as a co-factor supporting HCV chronic infection in a hepatocyte cell model. siRNA knockdown in Huh7-HCV cells; quantitative PCR and western blotting for HCV RNA and core antigen Zhonghua gan zang bing za zhi Medium 23207339
2015 Oligodendrocytes transfected with mutant EIF2B3 (c.1037T>C) showed decreased cell viability and increased apoptosis under endoplasmic reticulum stress compared to wild-type. Autophagy flux was depressed in mutant cells at baseline and after ER stress, with reduced expression of Atg3 and Atg7. Autophagy inducers rescued cell viability in mutant cells, while autophagy inhibitors aggravated apoptosis, placing EIF2B3 function upstream of autophagy-mediated ER stress tolerance in oligodendrocytes. Oligodendrocyte cell line transfection with mutant vs. wild-type EIF2B3; cell viability assay, apoptosis measurement, autophagy flux analysis, pharmacological modulation with autophagy inducers/inhibitors Brain & development Medium 26625702
2021 CRISPR knockout of eif2b3 in zebrafish caused defects in myelin development and glial cell differentiation, increased expression of integrated stress response pathway genes, and ectopic angiogenesis with increased VEGF expression. Ectopic angiogenesis was reduced by VEGF receptor inhibitor SU5416, placing EIF2B3 loss upstream of VEGF-driven angiogenesis. The model was used to validate pathogenicity of 18 known and one novel EIF2B3 human disease variant. CRISPR mutagenesis in zebrafish (two independent alleles); in silico protein modeling; pharmacological rescue with SU5416; functional complementation of human variants Human molecular genetics Medium 33517449
2021 An intronic polyadenylation (IPA) isoform of EIF2B3 is translated into a C-terminus truncated EIF2Bγ protein. Structural modeling predicts this truncated protein has unfavorable interactions with EIF2γ, potentially destabilizing the nonproductive EIF2:EIF2B complex and shifting the equilibrium between productive and nonproductive states of EIF2:EIF2B. The IPA isoform is expressed in breast cancer cells and normal tissues. Transcript and protein level analyses confirming IPA mRNA and truncated protein; structural modeling of EIF2Bγ–EIF2γ interactions Proteins Low 34796993

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2000 Identification of eIF2Bgamma and eIF2gamma as cofactors of hepatitis C virus internal ribosome entry site-mediated translation using a functional genomics approach. Proceedings of the National Academy of Sciences of the United States of America 75 10900014
2012 Adult-onset vanishing white matter disease due to a novel EIF2B3 mutation. Archives of neurology 27 22312164
2012 A 66-year-old patient with vanishing white matter disease due to the p.Ala87Val EIF2B3 mutation. Neurology 18 23115207
2021 Eif2b3 mutants recapitulate phenotypes of vanishing white matter disease and validate novel disease alleles in zebrafish. Human molecular genetics 13 33517449
2015 Endoplasmic reticulum stress intolerance in EIF2B3 mutant oligodendrocytes is modulated by depressed autophagy. Brain & development 12 26625702
2021 Identification of a Missense Variant in the EIF2B3 Gene Causing Vanishing White Matter Disease with Antenatal-Onset but Mild Symptoms and Long-Term Survival. Journal of molecular neuroscience : MN 8 33687620
2017 Postmortem Whole Exome Sequencing Identifies Novel EIF2B3 Mutation With Prenatal Phenotype in 2 Siblings. Journal of child neurology 7 28597716
2017 Case of Childhood Ataxia with Central Nervous System Hypomyelination with a Novel Mutation in EIF2B3 gene. Journal of pediatric neurosciences 6 28904586
2024 Adult-onset leukoencephalopathy with vanishing white matter with compound heterozygous EIF2B3 gene variants. BMC neurology 4 38872124
2021 A C-term truncated EIF2Bγ protein encoded by an intronically polyadenylated isoform introduces unfavorable EIF2Bγ-EIF2γ interactions. Proteins 4 34796993
2019 Correlation Between Vanishing White Matter Disease and Novel Heterozygous EIF2B3 Variants Using Next-Generation Sequencing: A Case Report. Annals of rehabilitation medicine 4 31072091
2012 Childhood Ataxia with Cerebral Hypomyelination Syndrome: a Variant of Patient with Early Childhood Onset Related to EIF2B3 Mutation. A Case Report. The neuroradiology journal 2 24028880
2012 [siRNAs targeting La, hVAP-33, eIF2Bgamma, and HCV IRES inhibit the replication and expression of HCV in Huh7 cells]. Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 0 23207339

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