{"uniprot":"Q6NSZ9","gene":"ZSCAN25","name":"Zinc finger and SCAN domain-containing protein 25","organism":"Homo sapiens (Human)","status":"dark","length":544,"sequence":"MLKEHPEMAEAPQQQLGIPVVKLEKELPWGRGREDPSPETFRLRFRQFRYQEAAGPQEALRELQELCRRWLRPELHTKEQILELLVLEQFLTILPREFYAWIREHGPESGKALAAMVEDLTERALEAKAVPCHRQGEQEETALCRGAWEPGIQLGPVEVKPEWGMPPGEGVQGPDPGTEEQLSQDPGDETRAFQEQALPVLQAGPGLPAVNPRDQEMAAGFFTAGSQGLGPFKDMALAFPEEEWRHVTPAQIDCFGEYVEPQDCRVSPGGGSKEKEAKPPQEDLKGALVALTSERFGEASLQGPGLGRVCEQEPGGPAGSAPGLPPPQHGAIPLPDEVKTHSSFWKPFQCPECGKGFSRSSNLVRHQRTHEEKSYGCVECGKGFTLREYLMKHQRTHLGKRPYVCSECWKTFSQRHHLEVHQRSHTGEKPYKCGDCWKSFSRRQHLQVHRRTHTGEKPYTCECGKSFSRNANLAVHRRAHTGEKPYGCQVCGKRFSKGERLVRHQRIHTGEKPYHCPACGRSFNQRSILNRHQKTQHRQEPLVQ","function_summary":"A nuclear transcriptional regulator that assembles oligomeric complexes via an N‑terminal oligomerization module, targets specific genomic sites through a C‑terminal array of zinc fingers, and recruits a repression cassette to silence nearby RNA polymerase II promoters and enhancers. By coupling SCAN-mediated assembly with a KRAB-driven co‑repressor platform, it concentrates chromatin-modifying machinery in the nucleoplasm to enforce stable transcriptional repression at selected loci.","plain_language":"ZSCAN25 has barely been studied. The model's best guess: A nuclear transcriptional regulator that assembles oligomeric complexes via an N‑terminal oligomerization module, targets specific genomic sites through a C‑terminal array of zinc fingers, and recruits a repression cassette to silence nearby RNA polymerase II promoters and enhancers. By coupling SCAN-mediated assembly with a KRAB-driven co‑repressor platform, it concentrates chromatin-modifying machinery in the nucleoplasm to enforce stable transcriptional repression at selected loci.","uniprot_summary":"May be involved in transcriptional regulation.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0000122","label":"negative regulation of transcription by RNA polymerase II"}],"cellular_component":[{"id":"GO:0005654","label":"nucleoplasm"}]},"interpro":[{"id":"IPR038269","name":"SCAN domain superfamily","type":"homologous_superfamily","start":34,"end":124},{"id":"IPR036051","name":"Krueppel-associated box domain superfamily","type":"homologous_superfamily","start":224,"end":258},{"id":"IPR036236","name":"Zinc finger C2H2 superfamily","type":"homologous_superfamily","start":346,"end":440},{"id":"IPR036236","name":"Zinc finger C2H2 superfamily","type":"homologous_superfamily","start":439,"end":532},{"id":"IPR003309","name":"SCAN domain","type":"domain","start":38,"end":151},{"id":"IPR001909","name":"Krueppel-associated box","type":"domain","start":231,"end":259},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":348,"end":375},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":375,"end":402},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":403,"end":430},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":431,"end":458},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":459,"end":485},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":486,"end":513},{"id":"IPR013087","name":"Zinc finger C2H2-type","type":"domain","start":514,"end":541}],"reasoning":"I begin by dissecting the domain architecture. The N-terminus carries IPR038269 (SCAN domain superfamily, residues 34–124) and a more specific IPR003309 (SCAN domain, residues 38–151). SCAN modules form oligomeric interfaces that drive homo- and hetero-assembly among SCAN-containing transcription factors, thereby creating higher-order regulatory complexes. Midway through the sequence sits IPR036051 (Krueppel-associated box domain superfamily, residues 224–258) together with IPR001909 (Krueppel-associated box, residues 231–259). The KRAB module is a canonical transcriptional repression cassette that recruits co-repressor machinery. The C-terminal half is dominated by a tandem array of C2H2 zinc fingers: IPR036236 (Zinc finger C2H2 superfamily, residues 346–440 and 439–532) encompasses multiple discrete C2H2 units annotated individually as IPR013087 (Zinc finger C2H2-type, residues 348–375; 375–402; 403–430; 431–458; 459–485; 486–541). This clustered array forms a high-specificity DNA-recognition platform that binds defined promoter or enhancer motifs and positions the KRAB repression machinery at target loci.\n\nThis ordered architecture—SCAN oligomerization module, KRAB repression cassette, and a multi-finger C2H2 DNA-binding array—causally establishes a transcriptional regulator that binds DNA and assembles repressive complexes. The SCAN and KRAB modules necessitate extensive macromolecular contacts with partner proteins, directly supporting GO:0005515 protein binding as a core molecular function. The C2H2 array dictates sequence-specific chromatin engagement, while KRAB converts binding into repression by recruiting co-repressors and chromatin modifiers.\n\nFrom this molecular function, the biological role follows: KRAB-mediated assembly of co-repressor complexes down-modulates transcription driven by RNA polymerase II. The zinc finger array targets specific regulatory DNA, and KRAB-dependent recruitment of silencing machinery reduces initiation and elongation outputs. This mechanism aligns with GO:0000122 negative regulation of transcription by RNA polymerase II.\n\nCellular localization is dictated by function and modules. DNA-targeting C2H2 fingers and KRAB-driven chromatin repression require a nuclear environment. The absence of transmembrane segments and the presence of chromatin-interacting modules point to a soluble nuclear pool, consistent with GO:0005654 nucleoplasm and a broader nuclear residency.\n\nMechanistically, the SCAN domain nucleates oligomeric assemblies that concentrate KRAB-containing complexes at specific genomic sites recognized by the C2H2 array. The KRAB region then recruits co-repressors that deposit repressive histone marks and compact chromatin, thereby silencing nearby Pol II promoters and enhancers. I hypothesize that SCAN-mediated oligomerization enhances avidity and locus selectivity, while KRAB-dependent pathways (for example, KAP1/TRIM28 scaffolding SETDB1 and HP1) execute stable repression. Likely interaction partners therefore include TRIM28/KAP1, SETDB1, HP1 family proteins, and NuRD/HDAC complexes, which together translate DNA targeting by the zinc fingers into durable transcriptional silencing within the nucleoplasm.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q6NSZ9.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q6NSZ9"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q6NSZ9/entry","atlas":"/p/Q6NSZ9"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}