DTX2

DTX2 is a RING-finger E3 ubiquitin ligase whose WWE domains read ADP-ribose modifications, enabling it to couple ADP-ribosylation signaling to ubiquitin-dependent substrate fate decisions across DNA repair, telomere maintenance, ferroptosis regulation, and Notch signaling. At DNA double-strand breaks, DTX2 is recruited in a poly-ADP-ribosylation-dependent manner and promotes homologous recombination by facilitating BRCA1 focus formation while limiting 53BP1 accumulation (PMID:38992439). DTX2 catalyzes K48-linked ubiquitination of substrates including NCOA4, HSD17B4, FTO, and HLTF to target them for proteasomal degradation—thereby suppressing ferroptosis, modulating m6A RNA methylation, and influencing tumor progression—and performs K63-linked ubiquitination of NFIC to promote hTERT transcription and telomerase activity (PMID:39366066, PMID:40058099, PMID:39661064, PMID:38163902, PMID:35198878). DTX2 also catalyzes non-canonical ubiquitin conjugation directly onto ADP-ribose moieties (MARUbylation), as demonstrated on PARP7 and the androgen receptor, linking mono-ADP-ribosylation to proteasomal degradation (PMID:38992439, PMID:37500075).

1. 2006 Medium

   Identification of DTX2 as a WWE- and RING-domain-containing protein established it as a member of the Deltex E3 ligase family, providing the structural framework for all subsequent functional studies.

   Evidence cDNA cloning, RACE, and Northern blot from human fetal/adult tissues

   PMID:17286044

   Open questions at the time

   • No enzymatic activity demonstrated at this stage
   • Substrate specificity unknown
   • Role of WWE domains not yet functionally defined
2. 2022 High

   Discovery that DTX2 promotes hTERT transcription by K63-linked ubiquitination of NFIC revealed that DTX2 can perform non-degradative ubiquitination to regulate transcription factor activity, establishing its first defined substrate and cellular function.

   Evidence CRISPR/Cas9 reporter screen, BioID proximity labeling, ChIP, ubiquitination assay, telomerase activity and telomere length measurements

   PMID:35198878

   Open questions at the time

   • How K63-linked ubiquitination of NFIC mechanistically enhances promoter binding is unclear
   • Whether DTX2 regulation of telomerase is cell-type-specific was not assessed
3. 2023 Medium

   Demonstration that DTX2 binds RUNX1, induces its non-degradative ubiquitination, blocks acetylation, and causes cytoplasmic mislocalization showed DTX2 can inhibit transcription factor activity through a ubiquitin-dependent but non-proteolytic mechanism.

   Evidence AlphaScreen binding assay, Co-IP, luciferase reporter, ubiquitination assay, immunofluorescence in leukemia cells

   PMID:37500075

   Open questions at the time

   • Ubiquitin chain type on RUNX1 not determined
   • In vivo relevance to leukemia not tested
   • Whether DTX2 similarly regulates RUNX2/RUNX3 function in physiological contexts is unresolved
4. 2024 High

   Recruitment of DTX2 to DNA double-strand breaks via PAR-dependent WWE domain binding, and its requirement for efficient homologous recombination and BRCA1 focus formation, established DTX2 as a DNA damage response factor linking ADP-ribosylation to repair pathway choice.

   Evidence Microirradiation-based localization screen, domain deletions, HR/NHEJ reporter assays, 53BP1/BRCA1 foci analysis, clonogenic survival after X-rays and PARPi

   PMID:38992439

   Open questions at the time

   • Direct ubiquitination substrate(s) at DSBs not identified
   • Whether DTX2 catalytic activity or scaffolding is required for HR promotion is unresolved
   • Relationship between DTX2 and other PAR-dependent repair factors not mapped
5. 2024 High

   Identification of DTX2 as the E3 ligase mediating K48-linked ubiquitination and degradation of multiple substrates—NCOA4, HLTF, and FTO—expanded the catalog of DTX2 targets and connected it to ferroptosis suppression, glioma progression, and m6A RNA methylation regulation.

   Evidence Co-IP, in vitro ubiquitination assays, knockdown/overexpression, xenograft models, VES binding assays, m6A profiling

   PMID:38163902 PMID:39366066 PMID:39661064

   Open questions at the time

   • HLTF ubiquitination chain linkage type not specified
   • Whether DTX2-mediated NCOA4 degradation operates via WWE-ADP-ribose recognition or direct binding is unclear
   • Physiological regulation of DTX2 expression/activity beyond JAK2-STAT3 is largely unexplored
6. 2024 Medium

   Zebrafish genetic experiments showed Dtx2 acts as a negative regulator of Notch-Rbpj signaling in spinal cord regeneration, placing DTX2 upstream of Notch in an in vivo neural context distinct from mammalian cancer settings.

   Evidence Heterozygous dtx2 mutant zebrafish, dominant-negative Rbpj epistasis, immunohistochemistry, motor function assay

   PMID:39001828

   Open questions at the time

   • Direct biochemical mechanism by which Dtx2 restrains Notch-Rbpj signaling not identified
   • Whether this reflects conserved mammalian biology is uncertain
7. 2025 High

   DTX2 was shown to catalyze K48-linked ubiquitination and degradation of HSD17B4 at K645, reducing DHA-containing PUFAs and suppressing ferroptosis in drug-resistant hepatocellular carcinoma, with DTX2 transcription activated by the JAK2-STAT3 pathway.

   Evidence CRISPR screen, in vitro ubiquitination with K645 mutagenesis, lipidomics, in vivo xenograft, DHA supplementation rescue

   PMID:40058099

   Open questions at the time

   • Whether DTX2-HSD17B4 axis operates in non-cancer ferroptosis contexts is untested
   • Structural basis for HSD17B4 recognition by DTX2 is unknown
8. 2025 Medium

   The discovery that DTX2 catalyzes monoubiquitylation directly on ADP-ribose moieties (MARUbylation) of PARP7—creating a hybrid Ub-ADP-ribose mark subsequently extended by RNF114—established a non-canonical ubiquitin conjugation mechanism and unified the WWE-domain ADP-ribose reader function with catalytic output.

   Evidence (preprint) Cellular ubiquitination assay with PARP7 catalytic mutant, click chemistry probe, Co-IP

   PMID:bio_10.1101_2025.05.11.653360

   Open questions at the time

   • Preprint not yet peer-reviewed
   • In vitro reconstitution with purified components not yet shown
   • Breadth of MARUbylation substrates beyond PARP7 not systematically surveyed

• Key open questions include: the structural basis for DTX2 WWE domain recognition of mono- versus poly-ADP-ribose, the full scope of MARUbylation substrates, the identity of DTX2 ubiquitination targets at DNA damage sites that mediate HR pathway choice, and the physiological contexts governing whether DTX2 performs canonical versus non-canonical ubiquitination.
• No crystal or cryo-EM structure of DTX2 WWE domains bound to ADP-ribose
• No systematic proteomics of DTX2-dependent ubiquitination events at DSBs
• Regulatory inputs controlling DTX2 beyond JAK2-STAT3 are largely unknown