RNF26

RNF26 is an endoplasmic reticulum-anchored RING-type E3 ubiquitin ligase that organizes endolysosomal positioning, membrane contact sites, and proteostasis, and that acts more broadly as a substrate-selective ligase shaping innate immune and oncogenic signaling (PMID:11352657, PMID:33472082, PMID:37519262). At the ER membrane it pairs with the E2 enzyme UBE2J1 to ubiquitylate SQSTM1/p62 on K435, recruiting endosomal adaptors that immobilize endosomes in the perinuclear region and route activated EGFR toward lysosomal degradation, thereby terminating EGF-induced AKT signaling (PMID:33472082). Its perinuclear confinement is achieved through binding of the C-terminus of its RING domain to vimentin intermediate filaments, restricting RNF26 to perinuclear ER subdomains where it builds membrane contact sites that retain endolysosomes and support Sec62-mediated ER-phagy recovery from ER stress (PMID:37519262). In antiviral immunity, RNF26 catalyzes K11-linked polyubiquitination of MITA/STING at K150 to shield it from RNF5-driven degradation and promote early type I interferon induction, while later restraining the response by promoting autophagic degradation of IRF3 (PMID:25254379). Across cancer contexts RNF26 directs proteasomal turnover of multiple substrates—CBX7, p57/CDKN1C, TSC1, and TRIM21—to drive cell cycle progression, mTOR activity, and TNF/NF-κB signaling, and its activity is gated by CDK4-mediated phosphorylation and PTPRZ1-mediated dephosphorylation at Y432 (PMID:34650035, PMID:35342353, PMID:38890443, PMID:39443724, PMID:39267687). RNF26 also K48-ubiquitylates the ER chaperone GRP78 to sustain ER stress, reducing MHC-I antigen presentation and elevating PD-L1 to drive immune evasion in hepatocellular carcinoma (PMID:41687462).

1. 2001 Medium

   Established the protein architecture of RNF26, predicting E3 ligase function from its domain composition before any catalytic activity had been tested.

   Evidence Molecular cloning and sequence/domain analysis identifying an N-terminal leucine zipper and C-terminal C3HC5 RING finger

   PMID:11352657

   Open questions at the time

   • No in vitro ubiquitination assay demonstrating catalytic activity
   • No substrate or partner identified at this stage
2. 2014 High

   Defined the first physiological substrate and a biphasic role in antiviral signaling, showing RNF26 both stabilizes STING early and dampens the response late.

   Evidence Reciprocal Co-IP, K150 site-directed ubiquitination assays, knockdown and viral infection time-course assays

   PMID:25254379

   Open questions at the time

   • Mechanism of IRF3 autophagic targeting not fully elaborated
   • E2 partner for STING ubiquitination not defined in this context
3. 2021 High

   Identified the UBE2J1/RNF26 E2/E3 complex and its p62-K435 substrate as the machinery that anchors endosomes perinuclearly and controls EGFR/AKT signaling termination.

   Evidence Reciprocal Co-IP, K435 mutagenesis, live-cell imaging, fractionation, and AKT phosphorylation assays

   PMID:33472082

   Open questions at the time

   • Full set of endosomal adaptors recruited not enumerated
   • Structural basis of the E2/E3 pairing unresolved
4. 2021 Medium

   Connected RNF26 to cell cycle control via a FOXM1/MuvB transcriptional axis and p57/CDKN1C degradation in bladder cancer.

   Evidence ChIP for transcriptional regulation, Co-IP, and Western blot degradation and cell cycle assays

   PMID:34650035

   Open questions at the time

   • No in vitro ubiquitination of p57 demonstrated
   • Single lab, single tumor context
5. 2022 Medium

   Extended the substrate repertoire to CBX7, linking RNF26 to ETS1 de-repression and TNF pathway activation in ccRCC.

   Evidence Co-IP, ubiquitination assay, degradation Western blot, and proliferation assays

   PMID:35342353

   Open questions at the time

   • No in vitro reconstitution of CBX7 ubiquitination
   • Ubiquitin linkage type not defined
6. 2023 High

   Resolved how RNF26 is spatially confined, showing RING-domain binding to vimentin retains it at perinuclear ER and enables membrane contact sites supporting ER-phagy stress recovery.

   Evidence Co-IP, live-cell imaging, CLEM/EM, KO/knockdown, domain mapping, and ER stress recovery assays

   PMID:37519262

   Open questions at the time

   • How RING-domain vimentin binding is reconciled with catalytic ubiquitin transfer unclear
   • Regulation of MCS dynamics not detailed
7. 2023 Low

   Added RBM38 as a degradation target promoting pancreatic cancer proliferation.

   Evidence Interaction network analysis, Co-IP, and degradation Western blot with proliferation assays

   PMID:37099788

   Open questions at the time

   • No direct ubiquitination assay described
   • Single method for degradation, not independently confirmed
8. 2024 Medium

   Revealed kinase control of RNF26, with CDK4 phosphorylation enhancing TSC1 binding and CDK4/6 inhibitors stabilizing TSC1 to inactivate mTOR.

   Evidence Mass spectrometry, GST pull-down, Co-IP, phosphorylation analysis, and xenograft assays

   PMID:38890443

   Open questions at the time

   • Phosphosite on RNF26 not specified in this axis
   • Direct in vitro ubiquitination of TSC1 not shown
9. 2024 Medium

   Identified PTPRZ1-mediated Y432 dephosphorylation as a stabilizing input that boosts RNF26-driven TNF/NF-κB signaling in ccRCC.

   Evidence Mass spectrometry, Y432 site analysis, Co-IP, proteasome inhibitor Westerns, RNA-seq, and IHC

   PMID:39443724

   Open questions at the time

   • Kinase that phosphorylates Y432 not identified
   • Single lab, single tumor type
10. 2024 Medium

    Added TRIM21 as a K48-linked degradation substrate with ZHX3 as a downstream effector in bladder cancer.

    Evidence Co-IP, ubiquitination assay, degradation Western blot, and knockdown/overexpression assays

    PMID:39267687

    Open questions at the time

    • Direct enzymatic reconstitution not described
    • Mechanism linking TRIM21 loss to ZHX3 upregulation incomplete
11. 2026 High

    Linked RNF26 to tumor immune evasion by K48-ubiquitylating GRP78 to sustain ER stress, lowering MHC-I and raising PD-L1 to suppress CD8+ T cell infiltration.

    Evidence Interaction and ubiquitination assays, hepatocyte-specific Rnf26 KO mouse, 3D tumor-T cell co-culture, RNA-seq, and pharmacological ER stress inhibition

    PMID:41687462

    Open questions at the time

    • Site of GRP78 ubiquitination not mapped
    • Whether ER-positioning function contributes to the ER stress phenotype unclear
12. 2025 Low

    Implicated RNF26 in nuclear envelope condensate homeostasis through a phenotype resembling torsin deficiency.

    Evidence Genome-wide CRISPR/Cas9 screen with high-content imaging and ML-based condensate classification (preprint)

    PMID:bio_10.1101_2025.06.07.658469

    Open questions at the time

    • Molecular mechanism of condensate formation not established
    • Preprint, single genetic screen, awaits mechanistic validation

• How RNF26's ER-membrane positioning/contact-site function is mechanistically coordinated with its diverse substrate-degradation roles, and how a single ligase achieves substrate selectivity across immunity, cell cycle, and proteostasis, remains unresolved.
• No unifying model linking ER-anchored contact-site activity to cytosolic/nuclear substrate degradation
• Determinants of substrate and ubiquitin-linkage selectivity uncharacterized
• Structural basis of RING activity in the membrane context unknown