title: RNA catalyses nuclear pre-mRNA splicing.
abstract: In nuclear pre-messenger RNA splicing, introns are excised by the spliceosome, a dynamic machine composed of both proteins and small nuclear RNAs (snRNAs). Over thirty years ago, after the discovery of self-splicing group II intron RNAs, the snRNAs were proposed to catalyse splicing. However, no definitive evidence for a role of either RNA or protein in catalysis by the spliceosome has been reported so far. By using metal rescue strategies in spliceosomes from budding yeast, here we show that the U6 snRNA catalyses both of the two splicing reactions by positioning divalent metals that stabilize the leaving groups during each reaction. Notably, all of the U6 catalytic metal ligands we identified correspond to the ligands observed to position catalytic, divalent metals in crystal structures of a group II intron RNA. These findings indicate that group II introns and the spliceosome share common catalytic mechanisms and probably common evolutionary origins. Our results demonstrate that RNA mediates catalysis within the spliceosome.
authors.affiliation: 1] Graduate Program in Cell and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA [2] Department of Molecular Genetics and Cell Biology, Cummings Life Sciences Center, 920 East 58th Street, The University of Chicago, Chicago, Illinois 60637, USA [3].
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Fica
authors.forename: Nicole
authors.initials: N
authors.lastname: Tuttle
authors.forename: Thaddeus
authors.initials: T
authors.lastname: Novak
authors.forename: Nan-Sheng
authors.initials: NS
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Prakash
authors.initials: P
authors.lastname: Koodathingal
authors.forename: Qing
authors.initials: Q
authors.lastname: Dai
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Staley
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Piccirilli
mesh_terms: D002384:Catalysis; D002467:Cell Nucleus / Q000378:metabolism; D007438:Introns / Q000235:genetics; D008670:Metals / Q000378:metabolism; D008954:Models, Biological; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012331:RNA, Fungal / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D008670:Metals; D012322:RNA Precursors; D012331:RNA, Fungal; D012342:RNA, Small Nuclear; C405486:U6 small nuclear RNA