{"uniprot":"Q9NXX6","gene":"NSMCE4A","name":"Non-structural maintenance of chromosomes element 4 homolog A","organism":"Homo sapiens (Human)","status":"dark","length":385,"sequence":"MSGDSSGRGPEGRGRGRDPHRDRTRSRSRSRSPLSPRSRRGSARERREAPERPSLEDTEPSDSGDEMMDPASLEAEADQGLCRQIRHQYRALINSVQQNREDILNAGDKLTEVLEEANTLFNEVSRAREAVLDAHFLVLASDLGKEKAKQLRSDLSSFDMLRYVETLLTHMGVNPLEAEELIRDEDSPDFEFIVYDSWKITGRTAENTFNKTHTFHFLLGSIYGECPVPKPRVDRPRKVPVIQEERAMPAQLRRMEESHQEATEKEVERILGLLQTYFREDPDTPMSFFDFVVDPHSFPRTVENIFHVSFIIRDGFARIRLDQDRLPVIEPVSINEENEGFEHNTQVRNQGIIALSYRDWEEIVKTFEISEPVITPSQRQQKPSA","function_summary":"A nuclear adaptor that scaffolds genome-maintenance assemblies. It organizes non-enzymatic subunits that build and regulate a chromosome-protective complex, thereby enhancing cellular responses to DNA damage and supporting repair-coupled chromatin remodeling. By concentrating repair factors within nuclear bodies and stabilizing higher-order assemblies, it promotes efficient lesion processing and preserves genome integrity through targeted protein–protein interactions rather than direct catalysis.","plain_language":"NSMCE4A has barely been studied. The model's best guess: A nuclear adaptor that scaffolds genome-maintenance assemblies. It organizes non-enzymatic subunits that build and regulate a chromosome-protective complex, thereby enhancing cellular responses to DNA damage and supporting repair-coupled chromatin remodeling.","uniprot_summary":"Contributes to the repair of DNA damage and the maintenance of genomic stability.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:2001022","label":"positive regulation of response to DNA damage stimulus"}],"cellular_component":[{"id":"GO:0016604","label":"nuclear body"},{"id":"GO:0030915","label":"Smc5-Smc6 complex"}]},"interpro":[{"id":"IPR029225","name":"Nse4/EID protein, Nse3/MAGE-binding domain","type":"domain","start":133,"end":187},{"id":"IPR014854","name":"Non-structural maintenance of chromosome element 4, C-terminal","type":"domain","start":285,"end":374},{"id":"IPR027786","name":"Nse4/EID family","type":"family","start":28,"end":378}],"reasoning":"I begin with the InterPro architecture. The polypeptide carries IPR029225 (Nse4/EID protein, Nse3/MAGE-binding domain, residues 133–187), followed by IPR014854 (Non-structural maintenance of chromosome element 4, C-terminal domain, residues 285–374). The entire core of the protein is encompassed by IPR027786 (Nse4/EID family, residues 28–378). This ordered layout—an internal Nse3/MAGE-binding module feeding into a conserved Nse4 C-terminal scaffold—defines a non-enzymatic adaptor that organizes macromolecular assemblies. The Nse3/MAGE-binding domain dictates selective protein–protein recognition, while the C-terminal Nse4 module stabilizes higher-order complexes. This architecture causes a primary molecular function of multivalent protein binding, aligning with GO:0005515 protein binding.\n\nFrom this binding-centric scaffold, I infer the biological role. Nse4-family scaffolds nucleate the non-enzymatic cap of the Smc5–Smc6 complex and couple it to DNA repair pathways. By stabilizing Smc5–Smc6 and recruiting auxiliary factors, this adaptor enhances genome maintenance pathways that respond to genotoxic stress. Such assembly and targeting of repair modules mechanistically produce positive regulation of the cellular response to DNA damage, consistent with GO:2001022 positive regulation of response to DNA damage stimulus. The same scaffold can bridge to SUMO machinery and chromatin-associated modules, explaining how the protein promotes repair-associated chromatin remodeling and lesion processing.\n\nCellular localization follows from the complex it builds and the chromatin it serves. The Nse4/EID architecture is a hallmark of nuclear genome-maintenance assemblies, placing the protein in nuclear substructures that concentrate repair and replication factors. This supports residence in nuclear bodies (GO:0016604 nuclear body) and direct association with the Smc5–Smc6 complex (GO:0030915 Smc5-Smc6 complex). The experimentally observed nuclear localization is therefore causally explained by its role in assembling and operating within chromatin-associated nuclear compartments.\n\nMechanistically, I hypothesize that the Nse3/MAGE-binding domain recruits specific partners to tune Smc5–Smc6 activity at damaged chromatin. By docking Nse3 and other repair adaptors, the protein forms a platform that enhances lesion processing and coordinates with SUMOylation pathways. Likely interaction partners include the Smc5–Smc6 core and its Nse subunits, as well as SUMO E3 modules and DNA repair effectors that localize to nuclear bodies where DNA damage signaling and repair are orchestrated.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q9NXX6.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q9NXX6"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q9NXX6/entry","atlas":"/p/Q9NXX6"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}