TRIM35

TRIM35 is a RING-domain E3 ubiquitin ligase that functions as a broad regulator of cancer metabolism, innate immune signaling, cardiac remodeling, and epigenetic transcription through ubiquitin-dependent control of diverse substrates. It catalyzes K48-linked polyubiquitination and proteasomal degradation of metabolic regulators (PKM2, IRF5, PDK1, EIF3E, CLOCK, TIGAR) and immune signaling factors (IRF7, adenovirus E1A), suppressing glycolysis/Warburg effect and modulating interferon responses (PMID:25263439, PMID:36196894, PMID:25907537, PMID:37578239, PMID:35081724, PMID:37594849). TRIM35 also mediates K63-linked non-degradative ubiquitination of LSD1 (repressing its demethylase activity to enhance IFN-γ signaling), TRAF3 (promoting IFN-β production), and RelB (maintaining nuclear retention to suppress NF-κB–driven MMP10 transcription), and removes K63-linked ubiquitin from STING to attenuate cGAS-STING signaling (PMID:37979167, PMID:34626690, PMID:39865905, PMID:39088122). In cardiomyocytes, TRIM35 monoubiquitinates histone H2B at K120 to remodel chromatin and activate P53-dependent transcription, and ubiquitinates nuclear PKM2 to destabilize GATA4/6, with cardiomyocyte-specific overexpression sufficient to induce dilated cardiomyopathy in mice (PMID:38860363, PMID:36322626).

1. 2003 Medium

   The initial characterization of HLS5/TRIM35 established it as a cytoplasmic- and nuclear-body-localized protein with growth-suppressive and anti-tumorigenic activity, setting the stage for identifying its molecular substrates.

   Evidence Microscopy and colony formation/xenograft assays in HeLa cells

   PMID:14662771

   Open questions at the time

   • No molecular substrate or E3 ligase activity identified
   • Mechanism of growth suppression unknown
2. 2007 High

   Discovery that HLS5/TRIM35 dynamically relocalizes from cytoplasmic granules to the nucleus under GATA-1 influence and suppresses GATA-1 transactivation by reducing its DNA binding revealed TRIM35 as a context-dependent transcriptional modulator in erythroid differentiation.

   Evidence Co-IP of HLS5 with GATA-1/FOG-1, reporter transactivation assays, DNA-binding assays in erythroid cells

   PMID:18063753

   Open questions at the time

   • Whether TRIM35 ubiquitinates GATA-1 or FOG-1 was not tested
   • Physiological role in erythropoiesis in vivo not established
3. 2014 High

   Identification of PKM2 as a direct TRIM35-interacting partner via its coiled-coil domain established the first mechanistic link between TRIM35 and cancer metabolism, showing that TRIM35 suppresses PKM2 Y105 phosphorylation and the Warburg effect in hepatocellular carcinoma.

   Evidence Mass spectrometry, Co-IP, coiled-coil domain deletion mutants, in vitro phosphorylation assays in HCC cells

   PMID:25263439

   Open questions at the time

   • Whether TRIM35 directly ubiquitinates PKM2 was not yet demonstrated
   • Upstream regulation of TRIM35 expression unknown
4. 2015 High

   Demonstration that TRIM35 catalyzes K48-linked ubiquitination of IRF7 for proteasomal degradation defined TRIM35 as a bona fide E3 ubiquitin ligase and revealed its role as a negative feedback regulator of TLR7/9-mediated type I interferon production.

   Evidence Co-IP, K48-linkage-specific ubiquitination assay, proteasome inhibitor rescue, IFN-β reporter in TLR-stimulated cells

   PMID:25907537

   Open questions at the time

   • In vivo relevance for antiviral immunity not shown
   • Structural basis for IRF7 recognition unknown
5. 2021 Medium

   Extension to innate immune signaling via porcine TRAF3 (K63-linked ubiquitination promoting IFN-β) and to cancer biology via CLOCK degradation in DLBCL showed TRIM35 can employ both K48 and K63 linkages on distinct substrates to achieve opposing outcomes on immune and proliferative pathways.

   Evidence Co-IP, linkage-specific ubiquitination assays, domain deletion mutants (RING, PRY/SPRY), IFN-β reporter, immune infiltration analysis

   PMID:34124276 PMID:34626690

   Open questions at the time

   • TRAF3 work in porcine system not validated in human cells
   • CLOCK ubiquitination linkage type not specified
   • In vivo immune phenotype for TRAF3 not tested
6. 2022 Medium

   A suite of studies identified additional TRIM35 degradation substrates—PKM2 (now shown to be directly ubiquitinated), PDK1, and TIGAR—demonstrating TRIM35's broad role in controlling cancer metabolism, AKT signaling, and mitochondrial homeostasis through K48-linked proteasomal pathways.

   Evidence Ubiquitination assays, Co-IP, metabolic readouts, apoptosis assays, xenograft models (breast cancer), renal ischemia-reperfusion injury models

   PMID:35081724 PMID:35421414 PMID:36196894

   Open questions at the time

   • Each substrate studied by a single lab without independent replication
   • Structural basis for multi-substrate recognition unresolved
   • TIGAR ubiquitination linkage type not specified
7. 2022 High

   In vivo demonstration that TRIM35 ubiquitinates nuclear PKM2 (S37-phosphorylated form) at K48 linkage in cardiomyocytes, destabilizing GATA4/6 and activating P53 to cause dilated cardiomyopathy, established TRIM35 as a pathogenic driver in heart failure using cardiomyocyte-specific transgenic/knockout mouse models and patient samples.

   Evidence Cardiomyocyte-specific TRIM35 overexpression and KO mice, echocardiography, Co-IP, ubiquitination assay, patient DCM samples

   PMID:36322626

   Open questions at the time

   • Whether cardiac TRIM35 upregulation is cause or consequence in human DCM requires longitudinal data
   • Therapeutic targetability not explored
8. 2023 High

   Discovery that TRIM35 catalyzes K63-linked ubiquitination of LSD1 at K422 to repress its demethylase activity, leading to ERGIC1-dependent autophagy inhibition and IFNGR1 stabilization that enhances MHC-I-mediated immune surveillance, connected TRIM35's epigenetic and immune functions in a single mechanistic cascade in NSCLC.

   Evidence Site-directed mutagenesis (K422), linkage-specific ubiquitination, LSD1 demethylase activity assay, flow cytometry for MHC-I

   PMID:37979167

   Open questions at the time

   • In vivo anti-tumor immune efficacy not tested with TRIM35 modulation
   • Whether LSD1 K63-ubiquitination is reversible by a specific DUB unknown
9. 2023 Medium

   Identification of IRF5 as a TRIM35 substrate linked ubiquitin-mediated IRF5 degradation to suppression of LDHA-driven glycolysis in HCC, extending TRIM35's metabolic regulatory reach to IRF family members beyond IRF7.

   Evidence Co-IP, ubiquitination assay, glycolysis metabolite readouts, patient IHC in HCC

   PMID:37594849

   Open questions at the time

   • Single lab, not independently replicated
   • IRF5 ubiquitination linkage and site not mapped
10. 2023 High

    TRIM35 was shown to target adenovirus E1A oncoprotein at K253 and K285 for K48-linked ubiquitination and degradation, establishing a direct antiviral effector function.

    Evidence Co-IP, ubiquitination with E1A lysine mutants (K253A, K285A), viral replication assays

    PMID:37578239

    Open questions at the time

    • Whether TRIM35 is IFN-induced during adenovirus infection not determined
    • Breadth of antiviral activity beyond adenovirus untested
11. 2024 High

    TRIM35 was found to directly monoubiquitinate histone H2B at K120 in cardiomyocytes, opening chromatin for P53 transcriptional activation and contributing to heart failure, establishing TRIM35 as a histone-modifying E3 ligase with epigenetic function in vivo.

    Evidence In vitro ubiquitination assay (H2BK120), ChIP-seq, RNA-seq, TRIM35 transgenic mice, patient DCM samples

    PMID:38860363

    Open questions at the time

    • Whether TRIM35 acts as a general H2BK120 ubiquitin ligase outside the heart is unknown
    • Relationship to canonical H2BK120 writers (RNF20/40) not addressed
12. 2024 High

    Discovery that TRIM35 removes K63-linked ubiquitin from STING via its RING domain (C36/C44), disrupting STING–TBK1/IKKε interaction and attenuating cGAS-STING-mediated IFN-β production, revealed an unexpected deubiquitinase-like activity for this RING E3 ligase.

    Evidence Co-IP, colocalization, deubiquitination assay, RING domain mutagenesis (C36A, C44A), TBK1/IKKε interaction mapping

    PMID:39088122

    Open questions at the time

    • Deubiquitinase mechanism for a RING E3 ligase is biochemically unusual and requires reconstitution with purified components
    • Whether this is direct catalytic DUB activity or facilitated by a DUB partner is unresolved
13. 2024 High

    In cardiac fibroblasts, TRIM35 ubiquitinates the amino acid transporter SLC7A5, upregulating it to activate mTORC1 signaling and promote fibroblast-driven cardiac remodeling, extending TRIM35's cardiac pathology from cardiomyocytes to fibroblasts.

    Evidence LC-MS/MS substrate identification, Co-IP, fibroblast-specific Trim35 KO mice under TAC, rapamycin rescue

    PMID:39304904

    Open questions at the time

    • How TRIM35-mediated ubiquitination upregulates (rather than degrades) SLC7A5 is mechanistically unclear
    • Whether non-degradative ubiquitination stabilizes or traffics SLC7A5 not resolved
14. 2025 Medium

    TRIM35 was shown to ubiquitinate histone H3 non-proteolytically, recruiting p300 for H3K27 acetylation and activating HSPA6 transcription, and separately to ubiquitinate RelB via K63 linkage to maintain its nuclear retention and suppress NF-κB-driven vascular calcification, consolidating TRIM35's role as an epigenetic and transcriptional regulator beyond degradation.

    Evidence ChIP-PCR, Co-IP, H3K27ac ChIP, p300 recruitment assay (breast cancer); conditional endothelial TRIM35 KO mice in arterial isograft model, nuclear fractionation (vascular calcification)

    PMID:39865905 PMID:41136372

    Open questions at the time

    • H3 ubiquitination site not mapped to a specific lysine
    • H3 ubiquitination claim from single lab awaits independent replication
    • How TRIM35 directly binds DNA promoters despite lacking a canonical DNA-binding domain is unexplained

• Key unresolved questions include the structural basis for TRIM35's remarkably broad substrate repertoire, how it switches between K48-linked degradative, K63-linked non-degradative, monoubiquitinating, and apparent deubiquitinating activities, and whether TRIM35 itself is regulated by post-translational modification or cofactor association in a tissue-specific manner.
• No crystal or cryo-EM structure available
• Mechanism of activity-type switching (K48 vs K63 vs monoUb vs deubiquitination) unknown
• Upstream regulatory inputs controlling TRIM35 expression and activity not systematically defined