DTX2

DTX2 is a RING/WWE-domain E3 ubiquitin ligase that controls the abundance and activity of diverse substrates through both conventional lysine-linked polyubiquitin chains and unconventional ubiquitylation of ADP-ribose, thereby regulating ferroptosis, DNA repair, telomerase transcription, and Notch/RUNX signaling (PMID:38992439, PMID:40058099, PMID:35198878). Through its RING domain it assembles K48-linked chains that drive proteasomal degradation of NCOA4, HSD17B4, HLTF, and FTO, suppressing ferritinophagy-driven and peroxisomal lipid-dependent ferroptosis and modulating m6A demethylation (PMID:39366066, PMID:40058099, PMID:39661064, PMID:38163902). In contrast, DTX2-mediated K63-linked ubiquitination of the transcription factor NFIC promotes its binding to the hTERT promoter, sustaining telomerase activity and telomere length in cancer cells (PMID:35198878). DTX2 can also ubiquitinate substrates non-degradatively: it modifies RUNX1 to block its acetylation and induce cytoplasmic mislocalization, restraining RUNX1 transcriptional output (PMID:37500075). Its WWE/DELTEX ADP-ribose reader domains recruit DTX2 to poly-ADP-ribosylated DNA double-strand breaks, where it promotes BRCA1 foci formation and homologous recombination at the expense of NHEJ, sensitizing cells to PARP inhibition when depleted (PMID:38992439). The same ADP-ribose-recognition capacity enables a distinct chemistry in which DTX2 ubiquitylates ADP-ribose moieties directly — generating monoubiquitin-MAR marks on PARP7 and tankyrase and recognizing PARP7-installed ADP-ribosyl degrons on the androgen receptor to drive lysine-independent AR degradation [PMID:bio_10.1101_2025.05.11.653360, PMID:bio_10.1101_2025.04.09.648013, PMID:bio_10.1101_2024.12.21.629908]. DTX2 additionally influences Notch signaling outputs in cancer cell migration and zebrafish glial proliferation (PMID:37087577, PMID:39001828).

1. 2006 Low

   Established the basic architecture of DTX2 as a candidate E3 ligase, defining the domains that would later prove functionally central.

   Evidence RACE cDNA cloning, Northern blot, and bioinformatic domain analysis identifying two WWE domains and a C-terminal RING finger

   PMID:17286044

   Open questions at the time

   • No functional validation of ligase activity
   • No substrate or pathway identified
   • Tissue expression beyond heart not characterized
2. 2022 High

   Showed DTX2 uses K63-linked, non-degradative ubiquitination to activate a transcription factor, revealing it does more than mark proteins for destruction.

   Evidence CRISPR KO screen with hTERT reporter, BioID, K63-linkage ubiquitination assay, NFIC ChIP, and telomerase activity readouts

   PMID:35198878

   Open questions at the time

   • Ubiquitination site on NFIC not mapped
   • How K63 chains promote promoter binding mechanistically unresolved
3. 2023 High

   Demonstrated DTX2 can ubiquitinate substrates to alter their activity and localization rather than degrade them, expanding its regulatory repertoire into transcription factor control.

   Evidence AlphaScreen binding, in vitro ubiquitination, acetylation assay, MCSFR reporter, and localization/growth assays in RUNX1-dependent leukemia lines

   PMID:37500075

   Open questions at the time

   • Ubiquitin chain linkage on RUNX1 not defined
   • Mechanism linking ubiquitination to acetylation blockade unclear
4. 2023 Medium

   Linked DTX2 to Notch-pathway-dependent cancer cell migration, connecting it to canonical Notch signaling outputs.

   Evidence shRNA/overexpression, migration/invasion assays, Notch2/NICD/p-AKT/MMP western blots, and Notch2 siRNA epistasis in colorectal cancer cells

   PMID:37087577

   Open questions at the time

   • No direct molecular target of DTX2 in the Notch2 axis identified
   • Ligase-activity dependence not tested
5. 2024 High

   Established DTX2 as a PAR-recruited regulator of DNA double-strand break repair pathway choice, tying its WWE/DELTEX domains to genome stability and PARP-inhibitor sensitivity.

   Evidence Microirradiation localization screen, domain-deletion analysis, HR/NHEJ reporters, BRCA1/53BP1 foci imaging, and X-ray/PARPi sensitization with rescue

   PMID:38992439

   Open questions at the time

   • Direct substrate at DSBs not identified
   • Whether ligase catalytic activity is required for HR promotion unresolved
6. 2024 Medium

   Identified DTX2 as a suppressor of NCOA4-driven ferritinophagy and ferroptosis via K48-linked degradation, defining a ferroptosis-regulatory role.

   Evidence Co-IP, ubiquitination assay, and knockdown/overexpression with ferroptosis readouts in non-small cell lung cancer cells

   PMID:39366066

   Open questions at the time

   • NCOA4 ubiquitination site not mapped
   • Single study without reciprocal in vivo confirmation
7. 2024 High

   Extended the ferroptosis-suppressor role to a second substrate and metabolic axis, with DTX2 targeting HSD17B4 to limit peroxisomal lipid metabolism in drug-resistant tumors.

   Evidence CRISPR screen, in vitro/in vivo ubiquitination with K645 site mutagenesis, lipid metabolomics, DHA rescue, and STAT3 inhibition in hepatocellular carcinoma

   PMID:40058099

   Open questions at the time

   • Generality of JAK2-STAT3 induction across tumor types untested
   • Relative contribution of NCOA4 vs HSD17B4 axes not compared
8. 2024 High

   Showed DTX2 targets the m6A demethylase FTO for UFD1-coupled proteasomal degradation, connecting it to RNA modification and a small-molecule (VES) modulator.

   Evidence Co-IP, ubiquitination assay, VES binding assay, and in vivo FTO knockdown/VES treatment with m6A readouts

   PMID:39661064

   Open questions at the time

   • FTO ubiquitination site not mapped
   • Mechanism of UFD1 recruitment by DTX2 unresolved
9. 2024 Medium

   Demonstrated DTX2 targets HLTF for degradation to promote glioma growth, broadening its degradative substrate set in cancer.

   Evidence Co-IP, confocal co-localization, in vitro ubiquitination, proliferation/migration assays, and xenograft model

   PMID:38163902

   Open questions at the time

   • Ubiquitin linkage type on HLTF undefined
   • Single-lab study
10. 2024 Medium

    Provided an in vivo developmental context, showing Dtx2 restrains glial proliferation and spinal cord recovery through Notch-Rbpj signaling.

    Evidence Heterozygous dtx2 zebrafish, post-injury motor and proliferation assays, and dominant-negative Rbpj epistasis

    PMID:39001828

    Open questions at the time

    • Molecular substrate linking Dtx2 to Rbpj output unknown
    • Relationship to mammalian DTX2 function untested
11. 2025 Medium

    Revealed an unconventional catalytic activity in which DTX2 ubiquitylates ADP-ribose moieties directly, generating hybrid marks on PARP7, tankyrase, and the androgen receptor that govern protein stability and signaling feedback.

    Evidence Cell-based ubiquitination assays with catalytic/site mutants, chemoenzymatic Ub-ADPr probes, ADP-ribosylation site mapping, and AR Cys620 mutant analysis (preprints)

    PMID:bio_10.1101_2024.12.21.629908 PMID:bio_10.1101_2025.04.09.648013 PMID:bio_10.1101_2025.05.11.653360

    Open questions at the time

    • Findings remain in preprints not yet peer-reviewed
    • Structural basis for ADP-ribose-directed ubiquitin transfer unresolved
    • Generality of the MARUbe mechanism across substrates untested

• How DTX2 selects between K48 degradative, K63 non-degradative, and ADP-ribose-directed ubiquitylation on different substrates, and what governs its substrate specificity, remains unresolved.
• No structural model of substrate or ADP-ribose engagement
• Determinants of chain-type choice unknown
• Physiological hierarchy among the many reported substrates undefined