{"rfam": {"acc": "RF00003", "id": "U1", "description": "U1 spliceosomal RNA", "comment": "U1 is a small nuclear RNA (snRNA) component of the spliceosome (involved in pre-mRNA splicing). Its 5' end forms complementary base pairs with the 5' splice junction, thus defining the 5' donor site of an intron. There are significant differences in sequence and secondary structure between metazoan and yeast U1 snRNAs, the latter being much longer (568 nucleotides as compared to 164 nucleotides in human). Nevertheless, secondary structure predictions suggest that all U1 snRNAs share a 'common core' consisting of helices I, II, the proximal region of III, and IV [1]. This family does not contain the larger yeast sequences. The structure of U1 spliceosomal RNA has been reported in [5,6]. It present 4 Stem loops (SL1, SL2, SL3, and SL4) and a region call Helix H. SL1, SL2, and SL3 are join for the Helix H, forming a four-helix junction that are separated of SL4. U1 snRNA is important in the precatalytic spliceosome, where the 5' splice site (5'SS) of the pre-mRNA is recognized by pairing with 5'-U1 snRNA. Where spliceosome activation is initiated by a disruption of the 5\u00e2\u20ac\u00b2SS\u00e2\u20ac\u201cU1 snRNP interaction by the DEAD-box helicase Prp28 [6]. The structure of U1 small nucleolar RNA was reported in PDB:6QX9", "curation": {"author": "Griffiths-Jones SR, Mifsud W, Moxon SJ, Ontiveros-Palacios N", "seed_source": "Zwieb C, The uRNA database, PMID:9016512", "num_seed": 100, "num_full": 40184, "num_species": 1499, "type": "Gene; snRNA; splicing;", "structure_source": "Published; PMID:2405391"}, "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": 69.5, "trusted": 69.5, "noise": 69.4}}, "release": {"date": "2026-01-16", "number": "15.1"}, "clan": {"acc": "CL00005", "id": "U1"}}}