title: Evidence for a group II intron-like catalytic triplex in the spliceosome.
abstract: To catalyze pre-mRNA splicing, U6 small nuclear RNA positions two metals that interact directly with the scissile phosphates. U6 metal ligands correspond stereospecifically to metal ligands within the catalytic domain V of a group II self-splicing intron. Domain V ligands are organized by base-triple interactions, which also juxtapose the 3' splice site with the catalytic metals. However, in the spliceosome, the mechanism for organizing catalytic metals and recruiting the substrate has remained unclear. Here we show by genetics, cross-linking and biochemistry in yeast that analogous triples form in U6 and promote catalytic-metal binding and both chemical steps of splicing. Because the triples include an element that defines the 5' splice site, they also provide a mechanism for juxtaposing the pre-mRNA substrate with the catalytic metals. Our data indicate that U6 adopts a group II intron-like tertiary conformation to catalyze splicing.
authors.affiliation: Graduate Program in Cell and Molecular Biology, The University of Chicago, Chicago IL.|Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago IL.
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Fica
authors.affiliation: Committee on Genetics Genomics and Systems Biology, The University of Chicago, Chicago, IL.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Mefford
authors.affiliation: Department of Chemistry, The University of Chicago, Chicago IL.|Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Piccirilli
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago IL.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Staley
mesh_terms: D001483:Base Sequence; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry; D012326:RNA Splicing; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D017381:Spliceosomes / Q000737:chemistry*
chemical_list: D012313:RNA
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