title: The Mrs1 splicing factor binds the bI3 group I intron at each of two tetraloop-receptor motifs.
abstract: Most large ribozymes require protein cofactors in order to function efficiently. The yeast mitochondrial bI3 group I intron requires two proteins for efficient splicing, Mrs1 and the bI3 maturase. Mrs1 has evolved from DNA junction resolvases to function as an RNA cofactor for at least two group I introns; however, the RNA binding site and the mechanism by which Mrs1 facilitates splicing were unknown. Here we use high-throughput RNA structure analysis to show that Mrs1 binds a ubiquitous RNA tertiary structure motif, the GNRA tetraloop-receptor interaction, at two sites in the bI3 RNA. Mrs1 also interacts at similar tetraloop-receptor elements, as well as other structures, in the self-folding Azoarcus group I intron and in the RNase P enzyme. Thus, Mrs1 recognizes general features found in the tetraloop-receptor motif. Identification of the two Mrs1 binding sites now makes it possible to create a model of the complete six-component bI3 ribonucleoprotein. All protein cofactors bind at the periphery of the RNA such that every long-range RNA tertiary interaction is stabilized by protein binding, involving either Mrs1 or the bI3 maturase. This work emphasizes the strong evolutionary pressure to bolster RNA tertiary structure with RNA-binding interactions as seen in the ribosome, spliceosome, and other large RNA machines.
authors.affiliation: Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States of America.
authors.forename: Caia D S
authors.initials: CD
authors.lastname: Duncan
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Weeks
mesh_terms: D020627:Azoarcus / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D004722:Endoribonucleases / Q000235:genetics*; D007438:Introns / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009713:Nucleotidyltransferases / Q000235:genetics*; D011485:Protein Binding; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D043262:Ribonuclease P / Q000235:genetics; D012261:Ribonucleoproteins / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C078505:MRS1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D012329:RNA, Bacterial; D012331:RNA, Fungal; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; D009713:Nucleotidyltransferases; C034038:mRNA maturase; D004722:Endoribonucleases; D043262:Ribonuclease P