E3 SUMO-protein ligase; has a preference for SUMO2 and SUMO3 and facilitates UBE2I/UBC9-mediated sumoylation of target proteins (PubMed:26524493, PubMed:26524494). Plays a role in protein SUMO2 modification in response to stress caused by DNA damage and by proteasome inhibitors (in vitro). Required for MCM4 sumoylation (By similarity). Has no activity with SUMO1 (PubMed:26524493). Preferentially transfers an additional SUMO2 chain onto the SUMO2 consensus site 'Lys-11' (PubMed:26524493). Negatively regulates transcriptional activation mediated by the SMAD4 complex in response to TGF-beta signaling. Inhibits EP300-mediated acetylation of histone H3 at 'Lys-9' (PubMed:24324267). Plays a role in regulating the transcription of AR targets (PubMed:18656483). Protein modification; protein sumoylation. Homooligomer. Interacts (via N-terminal region) with SUMO1 (PubMed:18656483). Interacts (via N-terminal region) with SUMO2 (PubMed:18656483, PubMed:26524494). Interacts simultaneously with two SUMO2 chains (PubMed:26524493, PubMed:26524494). Identified in a complex with SUMO2 and UBE2I/UBC9, where one ZNF451 interacts with one UBE2I/UBC9 and two SUMO2 chains, one bound to the UBE2I/UBC9 active site and the other to another region of the same UBE2I/UBC9 molecule (PubMed:26524493, PubMed:26524494). Interacts (via C-terminus) with ubiquitin (PubMed:18656483). Interacts (via N-terminal zinc-finger domains) with SMAD4 (via MH2 domain). Interacts with SMAD2 and SMAD3. Identified in a complex that contains at least ZNF451, SMAD2, SMAD3 and SMAD4. Interacts with EP300. Inhibits interaction between EP300 and the SMAD4 complex (PubMed:24324267). Colocalizes with UBE2I/UBC9, SUMO1 and SUMO2 in nuclear granules; this probably requires sumoylation. Desumoylation leads to diffuse nucleoplasmic location. Binds UBE2I/UBC9 and two SUMO2 molecules via its N-terminus. The most N-terminal region interacts with the SUMO2 chain that is covalently bound to the UBE2I/UBC9 active site, while the second region interacts with another SUMO2 that is non-covalently associated with the same UBE2I/UBC9 chain. Sumoylated. Predominantly sumoylated on the N-terminal region that is important for interaction with SUMO1 and SUMO2 (PubMed:18656483, PubMed:26524493, PubMed:26524494). Sumoylation is important for localization in nuclear granules; desumoylation leads to diffuse nucleoplasmic location (PubMed:18656483). Autosumoylated (in vitro) (PubMed:26524493, PubMed:26524494). Sumoylation enhances E3 SUMO-protein ligase activity (PubMed:26524494). Belongs to the krueppel C2H2-type zinc-finger protein family. Intron retention. Contaminating sequence. Contaminating sequence.