{"rfam": {"acc": "RF00015", "id": "U4", "description": "U4 spliceosomal RNA", "comment": "U4 small nuclear RNA (U4 snRNA) is a component of the major U2-dependent spliceosome. It forms a duplex with U6, and with each splicing round, it is displaced from U6 (and the spliceosome) in an ATP-dependent manner, allowing U6 to re-fold and create the active site for splicing catalysis. A recycling process involving protein Prp24 re-anneals U4 and U6. U4/U6 di-snRNA is conserved in eukaryotes and is part of the large ribonucleoprotein complex: U4 / U6.U5 tri-snRNP [5,8]. The structure of U4 snRNA from yeast[5,6,8,9,11] and human[2,7,10,12,13] has been reported. U4 snRNA present two regions where U4 and U6 form helixes (stem II and stem I share helixes) and two stem loops (5p-SL and 3p-SL), in human, is also present an extra SL in the 3p end. U4 snRNA presents a k-turn RNA motif in the 5p-SL related to recognition of Snu13 protein [8]. The structure of U4 spliceosomal RNA has been reported in PDBs: 2N7M, 3JCM, 3JCR, 5GAN, 5GAP, 5NRL, 5O9Z, 5ZWM, 5ZWO, 6AH0, 6AHD, AQW6, 6QX9 [5-13]", "curation": {"author": "Griffiths-Jones SR, Ontiveros-Palacios N", "seed_source": "Zwieb C, The uRNA database, PMID:9016512", "num_seed": 177, "num_full": 32178, "num_species": 2547, "type": "Gene; snRNA; splicing;", "structure_source": "Published; PMID:2339054; Griffiths-Jones SR"}, "cm": {"build_command": "cmbuild -F CM SEED", "calibrate_command": "cmcalibrate --mpi CM", "search_command": "cmsearch --cpu 4 --verbose --nohmmonly -T 30.00 -Z 2958934 CM SEQDB", "cutoffs": {"gathering": 46.0, "trusted": 46.0, "noise": 45.9}}, "release": {"date": "2026-01-16", "number": "15.1"}, "clan": {"acc": "CL00007", "id": "U4"}}}