RNF25

RNF25 (AO7) is a RING-finger E3 ubiquitin ligase that operates at the intersection of NF-κB transcriptional control, targeted protein degradation, and the cellular response to genotoxic and replicative stress (PMID:12748188, PMID:26475854, PMID:40764480). Structurally, it engages the E2 enzyme UbcH5B through a unique "clamp": a dedicated UbcH5B-binding region (U5BR) joined by a short linker to the RING domain, which encircles the E2 with unusually high affinity by contacting its backside; paradoxically this clamp dampens basal ubiquitination by occluding the stimulatory non-covalent ubiquitin-binding surface of UbcH5B (PMID:26475854). As a ligase RNF25 drives proteasomal turnover of multiple substrates, including Naked2 (PMID:18757723), E-cadherin downstream of redox-activated PKA phosphorylating RNF25 at Ser450 (PMID:38286671), and FKBP8 within a circSATB1-assisted complex that relieves inhibition of mTOR signaling (PMID:39921520), and it also catalyzes non-degradative ubiquitination of TRIP4 at K135 and of ribosomal protein eS31 (PMID:40765826, PMID:41875887). Through TRIP4 ubiquitination it liberates p65 to activate NF-κB and induce anti-apoptotic effectors, consistent with its original identification as a p65/RelA transactivation-domain partner and NF-κB co-activator (PMID:12748188, PMID:40765826). RNF25 additionally performs functions fully separable from its ligase activity: it recruits REV7 to nascent DNA to protect reversed replication forks from MRE11/CtIP-mediated degradation (PMID:40764480), and it disrupts the Nkd1-Axin complex to potentiate Wnt signaling (PMID:27007149). By ubiquitylating eS31, RNF25 restrains GCN2-dependent integrated stress response hyperactivation when ribosomes stall on damaged mRNA (PMID:41875887).

1. 2003 High

   Established RNF25 as a nuclear RING-finger protein that physically couples to the NF-κB p65 transactivation domain and is required for p65-driven transcription, defining its first functional context.

   Evidence Yeast two-hybrid, reciprocal co-IP, reporter assays, and a RING/ubiquitination-defective dominant-negative mutant

   PMID:12748188

   Open questions at the time

   • Did not identify a ubiquitination substrate explaining the transcriptional effect
   • Mechanism linking RING activity to p65 transactivation unresolved at this stage
2. 2008 High

   Identified the first direct degradative substrate, showing RNF25 targets Naked2 for proteasomal turnover and that TGF-α stabilizes Naked2 by reducing RNF25 binding.

   Evidence Co-IP, knockdown/overexpression, proteasomal degradation and half-life assays

   PMID:18757723

   Open questions at the time

   • Ubiquitin chain linkage on Naked2 not characterized
   • E2 partner used in cells not defined here
3. 2015 High

   Resolved the structural basis of E2 engagement, revealing a high-affinity clamp around UbcH5B that counterintuitively suppresses ubiquitination by blocking backside ubiquitin binding.

   Evidence Co-crystallography of the RNF25 U5BR/RING-UbcH5B complex with in vitro ubiquitination and interface mutagenesis

   PMID:26475854

   Open questions at the time

   • Physiological consequence of clamp-mediated rate control on specific substrates untested
   • Whether other E2s are used in vivo unknown
4. 2016 Medium

   Demonstrated a ligase-independent role in Wnt signaling, with RNF25 disrupting the Nkd1-Axin inhibitory complex to potentiate Wnt target gene transcription.

   Evidence Co-IP, zebrafish rnf25 knockdown, Wnt reporter assays, and E3-dead mutant

   PMID:27007149

   Open questions at the time

   • Direct structural mechanism of Nkd1-Axin disruption not defined
   • Single-lab in vivo model
5. 2018 Medium

   Connected RNF25 to therapy resistance, showing it mediates NF-κB activation, IL-6 induction, and ERK reactivation that drives gefitinib resistance in EGFR-mutant NSCLC.

   Evidence Genome-wide RNAi screen with knockdown/overexpression, NF-κB reporter, cytokine and ERK phosphorylation readouts

   PMID:29789542

   Open questions at the time

   • Molecular substrate underlying NF-κB activation not identified in this work
   • Dependence on ligase activity not tested
6. 2024 High

   Defined a redox-PKA-RNF25 axis in which oxidative activation of PKA phosphorylates RNF25 at Ser450 to drive E-cadherin degradation and promote HCC metastasis.

   Evidence In vitro ubiquitination, Ser450 mutagenesis, co-IP, redox analysis, and in vivo metastasis models with RNF25 knockdown

   PMID:38286671

   Open questions at the time

   • Ubiquitin chain type on E-cadherin not specified
   • Whether Ser450 phosphorylation alters E2 clamp behavior unknown
7. 2025 Medium

   Provided a mechanism for RNF25's NF-κB co-activation: non-degradative K135 ubiquitination of TRIP4 disrupts TRIP4-p65 binding to liberate p65 and upregulate anti-apoptotic genes.

   Evidence Co-IP, ubiquitination with K135 mutagenesis, p65 interaction and NF-κB reporter assays, plus BAY11-7082 direct binding

   PMID:40765826

   Open questions at the time

   • Reciprocal validation of TRIP4-p65 displacement in vivo limited
   • Single-lab study
8. 2025 High

   Revealed a ligase-independent genome-protection function: RNF25 recruits REV7 to nascent DNA to shield reversed replication forks from MRE11/CtIP nucleolytic degradation.

   Evidence Unbiased genetic screen, DNA fiber analysis, co-IP, KO phenotyping, and ligase-dead separation-of-function mutant

   PMID:39829812 PMID:40764480

   Open questions at the time

   • How RNF25 is itself recruited to stressed forks unknown
   • Structural basis of RNF25-REV7 interaction undefined
9. 2025 Medium

   Identified FKBP8 as a degradative substrate within a circSATB1-scaffolded RNF25-FKBP8 complex, linking RNF25 to mTOR signaling and metastasis.

   Evidence Co-IP, ubiquitination assay, knockdown/overexpression, and in vitro/in vivo metastasis assays

   PMID:39921520

   Open questions at the time

   • Mechanism by which circSATB1 promotes complex formation not detailed
   • Single-lab study
10. 2026 High

    Placed RNF25 in the mRNA damage response, showing it ubiquitylates ribosomal protein eS31 to restrain GCN2-dependent integrated stress response when ribosomes stall on azacytidine-damaged mRNA.

    Evidence Genetic screens, in vitro ubiquitination of eS31, ISR/eIF2α readouts, GCN2 epistasis, and RNF25 KO phenotyping

    PMID:41875887

    Open questions at the time

    • Ubiquitin signal read by the ISR machinery not fully defined
    • Generality across other ribosome-stalling lesions untested

• How RNF25 partitions between its ligase-dependent and ligase-independent functions, and what governs substrate and effector selection across NF-κB, degradation, fork protection, and stress-response roles, remains unresolved.
• No unifying determinant of substrate choice identified
• Interplay between the UbcH5B clamp and physiological ubiquitination outputs not mapped
• Regulation of RNF25 localization between nucleus, forks, and cytoplasmic complexes unclear