ZNF451

ZNF451 (ZATT) is a SUMO2/3-specific E3 ligase that operates at the interface of SUMO conjugation, genome maintenance, and transcriptional control (PMID:26524494, PMID:28912134). Its catalytic activity resides in an N-terminal module of tandem SUMO-interaction motifs bridged by a Pro-Leu-Arg-Pro (PLRP) element: the first SIM and PLRP engage thioester-charged E2~SUMO while the second SIM binds a second SUMO on the back face of the E2, stabilizing the closed conformation that drives transfer (PMID:26524494). Through this chemistry ZNF451 modifies multiple substrates and assembles SUMO-based recognition platforms. In DNA repair, it resolves trapped topoisomerase-2 DNA-protein cross-links both by directly facilitating proteasome-independent TDP2 hydrolase activity and by SUMOylating TOP2 to create a 'split-SIM' SUMO2 platform for TDP2 recruitment (PMID:28912134); under replication stress it SUMOylates TOP2A to recruit the translocase PICH and drive fork reversal (PMID:33296677); and it SUMOylates RNF168 at damage sites to stabilize it and amplify downstream H2A/H2AX ubiquitination during double-strand break repair (PMID:40055579). ZNF451 localizes to PML nuclear bodies, where it acts as a SUMO2/3 E3 for PML and cooperates with RNF4 to set physiological PML levels (PMID:18656483, PMID:27343429). Beyond genome maintenance it stabilizes substrates such as TWIST2 by blocking its ubiquitin-dependent degradation to promote mesenchymal phenotypes (PMID:33791162) and serves as a transcriptional co-regulator, supporting androgen-receptor target gene expression and partnering with SLUG to recruit PCAF and selectively activate CCL5 (PMID:18656483, PMID:37342906). In vivo, ZNF451 loss exacerbates bleomycin-induced pulmonary fibrosis through PDGFB/PI3K-Akt-driven fibroblast activation (PMID:38600524).

1. 2008 Medium

   Established ZNF451 as a SUMO-pathway protein by showing it localizes to PML bodies, binds Ubc9 and SUMO, is itself SUMOylated, and influences androgen-receptor target gene expression — the first functional placement of the protein.

   Evidence Co-IP, immunofluorescence, sumoylation and reporter assays, siRNA knockdown in prostate cancer cells

   PMID:18656483

   Open questions at the time

   • Did not define catalytic E3 activity or mechanism
   • SUMO sites mapped only as non-consensus, not residue-resolved
   • AR co-regulation correlative, no direct enzymatic link
2. 2015 High

   Resolved the catalytic mechanism, showing ZNF451's N-terminal tandem-SIM/PLRP module stabilizes the E2~SUMO closed configuration and confers SUMO2 specificity, defining it as a bona fide SUMO E3 ligase.

   Evidence Crystal structure with in vitro biochemistry and mutagenesis of the catalytic module

   PMID:26524494

   Open questions at the time

   • Physiological substrate repertoire not addressed structurally
   • Contribution of ZNF451 auto-SUMOylation to activity inferred, not quantified
3. 2016 Medium

   Identified PML and PML body components as cellular SUMO2/3 substrates of ZNF451 and placed it alongside RNF4 in regulating PML homeostasis.

   Evidence In vitro SUMO E3 ligase assays, mutational analysis, RNAi knockdown with IF/WB readouts

   PMID:27343429

   Open questions at the time

   • Arsenic-induced PML degradation shown ZNF451-independent, leaving trigger specificity open
   • Direct vs indirect cooperation with RNF4 not mechanistically dissected
4. 2017 High

   Defined ZATT/ZNF451 as a topoisomerase-2 cleavage-complex repair factor that both potentiates TDP2 hydrolase activity directly and builds a split-SIM SUMO2 platform to recruit TDP2 to SUMOylated TOP2.

   Evidence Biochemical reconstitution, Co-IP, in vitro TDP2 activity assays, cell-based repair assays, mutagenesis

   PMID:28912134

   Open questions at the time

   • Relative in vivo weight of catalytic vs non-catalytic resolution unresolved
   • Substrate specificity across TOP2 isoforms not delineated
5. 2020 High

   Extended ZATT into replication-stress responses, showing TOP2A SUMOylation recruits PICH to drive a defined step of fork reversal, linking SUMO ligase activity to genome stability at stalled forks.

   Evidence Co-IP, SUMO modification assays, replication fork EM/fiber analysis, genetic epistasis in KO/KD lines

   PMID:33296677

   Open questions at the time

   • Trigger for ZATT engagement at forks not defined
   • Interplay with the upstream HLTF/ZRANB3/SMARCAL1 step mechanistically incomplete
6. 2021 Medium

   Broadened the substrate scope beyond genome maintenance by showing ZNF451 SUMOylates TWIST2 at K129 to block its degradation and promote mesenchymal phenotypes.

   Evidence Co-IP, in vitro SUMOylation and ubiquitination assays, K129 mutagenesis, overexpression/knockdown with EMT marker readouts

   PMID:33791162

   Open questions at the time

   • Mechanism by which SUMOylation blocks ubiquitination not resolved
   • In vivo relevance to EMT/tumor progression not tested
7. 2023 Medium

   Demonstrated a non-catalytic, TDP2-independent role in TOP2 stability and etoposide survival, mapping the TOP2 interaction to residues 1-168 and showing additive sensitivity in ZATT/TDP2 double knockouts.

   Evidence Genome-wide CRISPR screens, deletion-mutant Co-IP, CHX-chase stability assays, double-KO epistasis

   PMID:37047518

   Open questions at the time

   • Molecular basis of ZATT-mediated TOP2 stabilization unknown
   • Whether stabilization is SUMO-dependent not established
8. 2023 Medium

   Revealed a chromatin co-regulator function in which ZNF451 partners with SLUG to recruit PCAF to the CCL5 promoter, coupling the protein to tumor-immune microenvironment signaling.

   Evidence Co-IP, ChIP, luciferase reporters, peptide competition, macrophage migration/activation assays

   PMID:37342906

   Open questions at the time

   • Role of SUMO ligase activity in this transcriptional function untested
   • Generality beyond the CCL5 locus unknown
9. 2025 Medium

   Connected ZNF451 to double-strand break signaling by showing it SUMOylates and stabilizes RNF168, amplifying H2A/H2AX ubiquitination, and that it co-regulates RNF168 with RNF8 in a competitive-cooperative manner.

   Evidence Co-IP, in-cell SUMOylation assays, IF at damage sites, KO/KD epistasis of ZNF451/RNF8/RNF168, ubiquitination assays

   PMID:40055579

   Open questions at the time

   • Structural basis of mutual ZNF451/RNF8 inhibition not defined
   • RNF168 SUMO acceptor sites not mapped
10. 2024 Medium

    Implicated ZNF451 in tissue protection in vivo, showing its downregulation drives fibroblast activation via PDGFB/PI3K-Akt and that knockout worsens while overexpression protects against pulmonary fibrosis.

    Evidence ZNF451 knockout mice, lentiviral overexpression rescue, RNA-seq, migration assays, immunoblot

    PMID:38600524

    Open questions at the time

    • Whether the fibrosis phenotype depends on SUMO ligase activity unknown
    • Direct molecular target linking ZNF451 to PDGFB not identified
11. 2024 Low

    Proposed a topological transcriptional role in which ZATT inhibits TOP2B catalytic activity during estrogen signaling to shape chromatin contacts.

    Evidence ChIP, topoisomerase activity assays, KO/KD epistasis, 3D genome contact analysis, transcriptional assays (preprint)

    PMID:38328138

    Open questions at the time

    • Preprint, not peer reviewed
    • Mechanism of supercoiling accumulation inferred, not directly measured
    • Requirement for ZATT catalytic activity vs scaffolding not separated

• How ZNF451's diverse substrate targeting is selected and regulated — and which of its many roles depend on SUMO ligase activity versus non-catalytic scaffolding — remains unresolved.
• No unifying model for substrate selection across DNA repair, transcription, and EMT
• Catalytic vs scaffolding requirements not systematically dissected
• Upstream signals that recruit ZNF451 to specific complexes unknown