ELOC

ELOC (elongin C, TCEB1) is an adaptor subunit of cullin-RING E3 ubiquitin ligase complexes, most prominently the VCB-CR/VBC complex (pVHL–elongin C–elongin B–cullin 2–RBX1) that mediates oxygen sensing and degradation of hypoxia-inducible factors (PMID:35323939). Within this complex ELOC bridges VHL to the cullin scaffold through hydrophobic contacts, and germline and somatic hotspot mutations at residues such as Y79 and E92 disrupt the ELOC–VHL interface; combined with chromosome 8 loss of heterozygosity, biallelic ELOC inactivation phenocopies VHL loss, drives convergent HIF pathway activation, and causes renal cell carcinoma and a VHL-disease-like syndrome that regresses under HIF-2α inhibition (PMID:35323939, PMID:41224595, PMID:37088333, PMID:31813809). ELOC additionally serves as an adaptor in CUL5-based complexes: as part of the HIV Vif–CBFβ–ELOB–ELOC–CUL5 assembly it directly impedes APOBEC3G DNA deamination independently of proteasomal degradation (PMID:38740386). The ELOC binding surfaces for CUL2 and CUL5 are spatially distinct, allowing selective small-molecule modulation of CRL2 versus CRL5 assembly (PMID:39881207). Beyond its E3 adaptor role, ELOC expression promotes cancer cell invasion and anchorage-independent growth through transcriptional regulation of pro-invasive genes (PMID:18844214), and its protein level is controlled post-transcriptionally by Staufen1-mediated decay of TCEB1 mRNA, which derepresses HIF-1α (PMID:34163032).

1. 2009 Medium

   Before its tumor-suppressor role was defined, ELOC was tested directly for a pro-tumorigenic cellular function, establishing that ELOC expression supports invasion and growth.

   Evidence shRNA knockdown and overexpression with Matrigel invasion, anchorage-independent growth, and transcriptional profiling in prostate cancer and NIH 3T3 cells

   PMID:18844214

   Open questions at the time

   • Does not identify the molecular activity of ELOC mediating the invasive transcriptional program
   • No link to E3 ligase function established here
2. 2014 Low

   To explain how viral hijacking of ELOC occurs, the Vif binding mode was modeled, indicating that BC-box leucines engage ELOC by hydrophobic interactions.

   Evidence Ab initio modeling (Rosetta), docking, and molecular dynamics of the Vif-EloBC complex

   PMID:24586532

   Open questions at the time

   • Purely computational with no experimental validation of the interface
   • Does not assay complex function or ubiquitination activity
3. 2019 Medium

   It was unknown whether ELOC mutations in RCC act as drivers; clonal and copy-number analysis established biallelic ELOC inactivation at the VHL-binding hotspot as a tumor-suppressor mechanism.

   Evidence Somatic mutation, copy number, and cancer cell fraction analysis of RCC tumors

   PMID:31813809

   Open questions at the time

   • Hydrophobic interaction disruption inferred from mutation position, not directly assayed
   • No functional rescue or HIF readout in this study
4. 2022 Medium

   Whether a germline ELOC variant could cause disease by mimicking VHL deficiency was open; a de novo Y79C variant was shown to recapitulate pVHL-deficient hypoxic signalling.

   Evidence Trio whole-exome sequencing, paired tumor/blood analysis, IHC for hypoxia-responsive proteins, RCC dataset bioinformatics

   PMID:35323939

   Open questions at the time

   • Single proband study
   • Direct biochemical demonstration of disrupted VCB-CR assembly not performed
5. 2023 Medium

   To distinguish ELOC-driven from VHL-driven RCC, mutual exclusivity and downstream HIF output were compared, showing convergent HIF pathway activation despite reduced ELOC expression.

   Evidence OncoScan copy number, WES, HADDOCK docking of an ELOC duplication, and hyper reaction monitoring mass spectrometry of CA9/VEGF-A

   PMID:37088333

   Open questions at the time

   • Structural disruption modeled computationally, not by experimental structure
   • Single-lab proteomic cohort
6. 2024 Medium

   It was unclear whether the ELOC-containing Vif-CUL5 complex acted only through degradation; functional assays revealed a direct, degradation-independent inhibition of APOBEC3G deamination.

   Evidence SELEX aptamer selection against the VβBCC complex and DNA deamination activity/inhibition assays

   PMID:38740386

   Open questions at the time

   • Mechanism of direct A3G inhibition by the complex not structurally resolved here
   • Contribution of ELOC specifically versus other subunits not isolated
7. 2025 Medium

   Two advances clarified ELOC druggability and disease genetics: a multigenerational E92G family established ELOC as a VHL-disease gene rescuable by HIF-2α inhibition, and fragment screening defined a ligandable ELOC pocket distinguishing CUL2 from CUL5 binding.

   Evidence Germline co-segregation, tumor LOH, belzutifan clinical response (family study); fragment screening with binding-site/interface mapping of the VBC complex

   PMID:39881207 PMID:41224595

   Open questions at the time

   • Family study is a single pedigree
   • Fragment-binding structural method not explicitly defined and selective CRL2 modulation only inferred from interface overlap

• How ELOC's invasion-promoting transcriptional role mechanistically relates to its E3 adaptor function remains unresolved.
• No molecular link between ELOC E3 adaptor activity and the pro-invasive transcriptional program
• No experimental high-resolution structure of mutant ELOC interfaces in the corpus