{"uniprot":"Q5VT52","gene":"RPRD2","name":"Regulation of nuclear pre-mRNA domain-containing protein 2","organism":"Homo sapiens (Human)","status":"dark","length":1461,"sequence":"MAAGGGGGSSKASSSSASSAGALESSLDRKFQSVTNTMESIQGLSSWCIENKKHHSTIVYHWMKWLRRSAYPHRLNLFYLANDVIQNCKRKNAIIFRESFADVLPEAAALVKDPSVSKSVERIFKIWEDRNVYPEEMIVALREALSTTFKTQKQLKENLNKQPNKQWKKSQTSTNPKAALKSKIVAEFRSQALIEELLLYKRSEDQIELKEKQLSTMRVDVCSTETLKCLKDKTGGKKFSKEFEEASSKLEEFVNGLDKQVKNGPSLTEALENAGIFYEAQYKEVKVVANAYKTFANRVNNLKKKLDQLKSTLPDPEESPVPSPSMDAPSPTGSESPFQGMGGEESQSPTMESEKSATPEPVTDNRDVEDMELSDVEDDGSKIIVEDRKEKPAEKSAVSTSVPTKPTENISKASSCTPVPVTMTATPPLPKPVNTSLSPSPALALPNLANVDLAKISSILSSLTSVMKNTGVSPASRPSPGTPTSPSNLTSGLKTPAPATTTSHNPLANILSKVEITPESILSALSKTQTQSAPALQGLSSLLQSVTGNPVPASEAASQSTSASPANTTVSTIKGRNLPSSAQPFIPKSFNYSPNSSTSEVSSTSASKASIGQSPGLPSTTFKLPSNSLGFTATHNTSPAAPPTEVTICQSSEVSKPKLESESTSPSLEMKIHNFLKGNPGFSGLNLNIPILSSLGSSAPSESHPSDFQRGPTSTSIDNIDGTPVRDERSGTPTQDEMMDKPTSSSVDTMSLLSKIISPGSSTPSSTRSPPPGRDESYPRELSNSVSTYRPFGLGSESPYKQPSDGMERPSSLMDSSQEKFYPDTSFQEDEDYRDFEYSGPPPSAMMNLEKKPAKSILKSSKLSDTTEYQPILSSYSHRAQEFGVKSAFPPSVRALLDSSENCDRLSSSPGLFGAFSVRGNEPGSDRSPSPSKNDSFFTPDSNHNSLSQSTTGHLSLPQKQYPDSPHPVPHRSLFSPQNTLAAPTGHPPTSGVEKVLASTISTTSTIEFKNMLKNASRKPSDDKHFGQAPSKGTPSDGVSLSNLTQPSLTATDQQQQEEHYRIETRVSSSCLDLPDSTEEKGAPIETLGYHSASNRRMSGEPIQTVESIRVPGKGNRGHGREASRVGWFDLSTSGSSFDNGPSSASELASLGGGGSGGLTGFKTAPYKERAPQFQESVGSFRSNSFNSTFEHHLPPSPLEHGTPFQREPVGPSSAPPVPPKDHGGIFSRDAPTHLPSVDLSNPFTKEAALAHAAPPPPPGEHSGIPFPTPPPPPPPGEHSSSGGSGVPFSTPPPPPPPVDHSGVVPFPAPPLAEHGVAGAVAVFPKDHSSLLQGTLAEHFGVLPGPRDHGGPTQRDLNGPGLSRVRESLTLPSHSLEHLGPPHGGGGGGGSNSSSGPPLGPSHRDTISRSGIILRSPRPDFRPREPFLSRDPFHSLKRPRPPFARGPPFFAPKRPFFPPRY","function_summary":"A nuclear adaptor that uses a helical solenoid scaffold with a CID module to organize protein assemblies controlling late stages of transcript maturation. By forming multivalent interfaces in the nucleoplasm, it binds and stabilizes transcription- and RNA-processing–associated complexes near the polymerase machinery, thereby coordinating mRNA 3′-end formation and associated termination steps through non-enzymatic, high-avidity interactions.","plain_language":"RPRD2 has barely been studied. The model's best guess: A nuclear adaptor that uses a helical solenoid scaffold with a CID module to organize protein assemblies controlling late stages of transcript maturation. By forming multivalent interfaces in the nucleoplasm, it binds and stabilizes transcription- and RNA-processing–associated complexes near the polymerase machinery, thereby coordinating mRNA 3′-end formation and associated termination steps through non-enzymatic, high-avidity interactions.","uniprot_summary":"May be involved in mRNA biogenesis.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0031124","label":"mRNA 3'-end processing"}],"cellular_component":[{"id":"GO:0005654","label":"nucleoplasm"},{"id":"GO:0016591","label":"RNA polymerase II, holoenzyme"}]},"interpro":[{"id":"IPR008942","name":"ENTH/VHS","type":"homologous_superfamily","start":17,"end":161},{"id":"IPR006569","name":"CID domain","type":"domain","start":19,"end":149},{"id":"IPR047885","name":"RPRD2, CID domain","type":"domain","start":27,"end":146}],"reasoning":"I begin with the InterPro architecture. The core of the protein is a contiguous ENTH/VHS-like fold annotated as IPR008942 (ENTH/VHS homologous_superfamily, residues 17–161). Nested within this scaffold are two overlapping cargo-adaptor signatures: IPR006569 (CID domain, residues 19–149) and the lineage-specific IPR047885 (RPRD2, CID domain, residues 27–146). The ordered layout—an ENTH/VHS-type helical solenoid that houses a CID module—creates a compact, non-enzymatic interaction platform. ENTH/VHS folds typically mediate avid, surface-driven binding to partner proteins and sometimes nucleic acids, while CID domains specialize in recognizing C-terminal heptad repeats and low-complexity segments of transcription and RNA-processing factors. This architecture dictates a primary molecular function of multivalent protein binding (GO:0005515), rather than catalysis.\n\nFrom this binding-centric core, I infer the biological role by considering what assemblies this fold is predisposed to organize. CID-bearing adaptors frequently dock onto the C-terminal domain of RNA polymerase II and associated termination/processing machineries. The ENTH/VHS scaffold provides the avidity and geometry to stabilize transient assemblies that finalize transcript maturation. Such assemblies naturally converge on mRNA 3′-end formation, aligning with the process of mRNA 3′-end processing (GO:0031124). The absence of catalytic motifs and the presence of a CID module argue that the protein acts as a regulatory adaptor that times and stabilizes processing steps rather than executing cleavage or polyadenylation chemistry directly.\n\nCellular localization follows from the assembly context. A CID-centered adaptor that coordinates RNA polymerase II–coupled maturation must operate in the soluble nuclear phase where transcription and RNA-processing complexes exchange partners. This places the protein in the nucleoplasm (GO:0005654). Its role in organizing polymerase-associated processing further situates it in proximity to the RNA polymerase II holoenzyme (GO:0016591), where it can bridge transcription with downstream RNA biogenesis.\n\nMechanistically, the ENTH/VHS–CID tandem forms a bipartite interaction hub that captures CTD-associated factors and 3′-end processing modules, thereby stabilizing the handoff from elongation to cleavage/polyadenylation. By concentrating these factors in the nucleoplasm, the protein likely tunes termination efficiency and RNA surveillance. I hypothesize that it transiently binds the RNA polymerase II CTD and recruits cleavage/polyadenylation assemblies (e.g., CPSF and CstF), as well as termination adaptors, to enforce orderly mRNA 3′-end maturation. This model predicts preferential associations with nuclear RNA-processing complexes and explains a nucleoplasmic residency adjacent to the polymerase holoenzyme.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q5VT52.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q5VT52"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q5VT52/entry","atlas":"/p/Q5VT52"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}