EIF6

EIF6 (p27BBP/ITGB4BP) is a 60S ribosomal subunit-binding factor whose control over 80S ribosome assembly couples ribosome biogenesis to the regulation of translation [PMID:17507929, PMID:bio_10.1101_2024.06.24.600220]. As an anti-association factor, eIF6 occupies the 60S subunit to block productive 80S formation, and a separation-of-function mutant (N106S) that disrupts eIF6–60S binding increases vacant 80S ribosomes, establishing that its anti-association activity is mechanistically distinct from its role in 60S biogenesis [PMID:bio_10.1101_2024.06.24.600220]. By limiting the active ribosomal pool, eIF6 governs accurate translation of mitotic factors and transcripts with long 3′UTRs; its dysregulation causes chromosome segregation defects, mitotic exit delays, and mitotic catastrophe [PMID:bio_10.1101_2024.06.24.600220]. The same anti-association property underlies a conserved role in miRNA-mediated silencing: eIF6 co-purifies with human RISC alongside MOV10 and 60S subunit proteins, and its depletion in human cells and C. elegans abrogates miRNA-mediated repression of target protein and mRNA levels (PMID:17507929). eIF6 is delivered to the nucleolus through binding of the lncRNA CRNDE UCE during 60S biogenesis [PMID:bio_10.1101_2024.07.23.604857], and it physically interacts with the small protein P311 (PMID:22365962).

1. 2001 Medium

   Before functional studies, it was unclear whether eIF6 was a uniform housekeeping factor; this work showed its expression is cell-specific in vivo despite constitutive expression in culture, implying regulation by tissue-specific and protein-synthesis-linked factors.

   Evidence Immunohistochemistry, qRT-PCR, and serum-starvation/heat-shock treatment of cultured cells

   PMID:11290417

   Open questions at the time

   • No functional manipulation linking expression level to translation or biogenesis
   • Regulatory factors driving tissue specificity not identified
2. 2007 High

   Addressed how a ribosome anti-association factor participates in gene silencing by showing eIF6 is a RISC-associated component required for miRNA-mediated repression, extending its anti-80S-assembly function to post-transcriptional control.

   Evidence Biochemical co-purification of RISC with MOV10 and 60S proteins plus eIF6 depletion in human cells and C. elegans with miRNA target readouts

   PMID:17507929

   Open questions at the time

   • Direct molecular mechanism by which eIF6 within RISC blocks 80S assembly on target mRNAs not resolved
   • Whether eIF6's silencing role is identical to its biogenesis pool unclear
3. 2012 Medium

   Identified a physical partner of eIF6 outside the ribosome, linking it to the small protein P311, though without a downstream functional mechanism.

   Evidence Yeast two-hybrid, FRET in pulmonary adenocarcinoma tissue, and co-immunoprecipitation in HEK293 cells

   PMID:22365962

   Open questions at the time

   • Functional consequence of the eIF6–P311 interaction unknown
   • No structural or stoichiometric characterization of the interaction
4. 2024 Medium

   Resolved whether eIF6's anti-association activity is separable from 60S biogenesis and connected ribosome availability to mitosis, using a binding-disruptive mutant to show increased vacant 80S, deregulated mitotic-factor translation, and mitotic defects.

   Evidence N106S point mutant, ribosome sedimentation, Ribo-Seq, and live-cell imaging of mitotic phenotypes (preprint)

   PMID:bio_10.1101_2024.06.24.600220

   Open questions at the time

   • Single preprint, not peer-reviewed
   • Mechanism coupling 80S availability specifically to mitotic transcript selection not fully defined
5. 2024 Low

   Began to define how eIF6 reaches its site of action, showing the lncRNA CRNDE UCE binds eIF6 and facilitates its nucleolar delivery during 60S biogenesis.

   Evidence CRISPRi screens, nucleolar localization assays, and CRNDE UCE–eIF6 RNA-protein binding assays (preprint)

   PMID:bio_10.1101_2024.07.23.604857

   Open questions at the time

   • Single preprint; mechanistic details of delivery incompletely characterized
   • Binding element mapped only adjacent to the UCE without structural detail
6. 2024 Low

   Began to connect eIF6 to stress-responsive translational control, with redox proteomics detecting cysteine oxidation on eIF6 and inferred complex disruption under oxidative stress.

   Evidence DIA-MS-based redox proteomics (DIALRP) in DU145 prostate cancer cells (preprint)

   PMID:bio_10.1101_2024.12.16.626735

   Open questions at the time

   • Single proteomic screen without functional validation
   • Direct effect of cysteine oxidation on eIF6–60S binding not demonstrated

• How eIF6 release from the 60S subunit is triggered and coordinated between its biogenesis, silencing, and mitotic-control functions remains unresolved.
• No molecular trigger for eIF6 release defined in the corpus
• Whether distinct eIF6 pools serve RISC versus biogenesis is unknown
• Structural basis of the anti-association mechanism not characterized