ELOA

ELOA (Elongin A) is a transcription elongation factor that sustains RNA polymerase II (RNAPII) processivity, particularly across the 3' ends of genes (PMID:41418754). ELOA occupies transcription end site (TES)-proximal chromatin, and its acute depletion reduces RNAPII processivity at gene 3' ends and curtails progression of RNAPII past TESs; genetic suppressor screens place ELOA downstream of NELF/SPT6 depletion-induced growth arrest and pre-mRNA processing defects (PMID:41418754). Structurally, ELOA engages the RPB1 jaw domain of RNAPII, competing with IWS1 for this site [PMID:bio_10.1101_2025.08.28.672863]. Beyond its core elongation role, ELOA acts as a sequence-directed transcriptional activator at specific promoters, binding and activating the LHPP and RBP1 promoters; loss of LHPP activation downstream of ELOA degradation derepresses AKT signaling in colorectal cancer cells, while RBP1 mediates ELOA's tumor-promoting effect in gastric cancer (PMID:36376892, PMID:37694492). ELOA protein abundance is controlled by Trim21-mediated ubiquitination and proteasomal degradation, an event promoted by physical interaction with the lncRNA DLGAP1-AS2 (PMID:36376892). ELOA additionally has a context-dependent cytoplasmic function: during platinum treatment in ovarian cancer cells its cytoplasmic pool increases and it serves as an E3 ligase recognition subunit targeting MCL-1 for ubiquitination and degradation (PMID:38661028). Functionally, ELOA promotes PMA-induced megakaryocytic polyploidization through enhanced ERK1/2 phosphorylation, a phenotype requiring its RNAPII elongation activity (PMID:34697988), and its loss confers a growth advantage to aging primary fibroblasts, linking ELOA-dependent elongation/processing to senescence (PMID:41418754).

1. 2003 Medium

   Established an early physical interaction partner for ELOA, identifying its N-terminal region as a protein-binding module engaging an exonuclease domain-containing protein in the nucleus.

   Evidence Yeast two-hybrid, in vitro binding, and double immunofluorescence in COS7 cells

   PMID:12943681

   Open questions at the time

   • Functional consequence of the ELOA–EloA-BP1 interaction not reconstituted
   • No link drawn to ELOA's elongation or ubiquitination roles
   • Interaction shown in heterologous systems only
2. 2021 Medium

   Connected ELOA's elongation activity to a cellular differentiation phenotype, showing it drives megakaryocytic polyploidization via the ERK1/2 cascade.

   Evidence shRNA knockdown, RNA-seq, ERK1/2 phospho-Western, MEK/ERK inhibitors, and elongation-competent ELOA mutant rescue in HEL cells

   PMID:34697988

   Open questions at the time

   • Direct ELOA targets within the ERK1/2 cascade not defined
   • Mechanism linking Pol II elongation to ERK activation unresolved
   • Single cell-line model
3. 2022 Medium

   Defined ELOA as a promoter-binding transcriptional activator and revealed how its degradation rewires oncogenic signaling, with lncRNA-directed Trim21 ubiquitination controlling its levels.

   Evidence ChIP, luciferase reporter, RNA-seq, RNA pull-down/RIP, ubiquitination and rescue assays in colorectal cancer cells

   PMID:36376892

   Open questions at the time

   • In vitro reconstitution of Trim21-mediated ubiquitination not performed
   • Direct vs. indirect promoter binding to LHPP not structurally resolved
   • Generality of DLGAP1-AS2 regulation beyond CRC unknown
4. 2023 Medium

   Extended ELOA's promoter-activator role to a second target gene, RBP1, in a distinct cancer context.

   Evidence RNA-seq, ChIP, dual luciferase reporter, and RBP1-knockdown epistasis in gastric cancer cells

   PMID:37694492

   Open questions at the time

   • Whether RBP1 activation reflects direct elongation enhancement or specific recruitment is unclear
   • No structural basis for promoter selectivity
5. 2024 Medium

   Revealed a non-transcriptional, cytoplasmic moonlighting function for ELOA as an E3 ligase recognition subunit targeting MCL-1 under genotoxic stress.

   Evidence Ubiquitination assay, subcellular fractionation, Western blot, knockdown/overexpression during platinum treatment in ovarian cancer cells

   PMID:38661028

   Open questions at the time

   • E3 activity not reconstituted in vitro
   • Trigger and machinery for ELOA cytoplasmic relocalization undefined
   • Whether MCL-1 is a direct ELOA substrate not structurally shown
6. 2025 High

   Pinned down ELOA's core mechanism as a TES-proximal factor maintaining RNAPII processivity at gene 3' ends and placed it genetically downstream of NELF/SPT6, also linking its loss to senescence.

   Evidence Auxin-inducible degron acute depletion, long/short-read RNA-seq, RNAPII ChIP-seq, genetic suppressor screen, and knockout in primary fibroblasts

   PMID:41418754

   Open questions at the time

   • Molecular basis of TES-proximal recruitment not fully resolved
   • How processivity defects translate into senescence outcomes unclear
7. 2025 Medium

   Provided a structural anchor point for ELOA on the elongation complex, showing it binds the RPB1 jaw domain in competition with IWS1.

   Evidence Cryo-EM structural mapping and binding competition assays (preprint)

   PMID:bio_10.1101_2025.08.28.672863

   Open questions at the time

   • ELOA finding is ancillary to an IWS1-focused study and is a preprint
   • Functional consequence of ELOA–IWS1 competition for ELOA-specific roles not established

• How ELOA's distinct activities — core elongation processivity, promoter-specific activation, and cytoplasmic E3 substrate recognition — are mechanistically partitioned and coordinated remains unresolved.
• No unified model linking nuclear elongation and cytoplasmic ubiquitination roles
• Determinants of ELOA promoter selectivity unknown
• Signals controlling nuclear vs. cytoplasmic partitioning undefined