title: Relevance of the branch point adenosine, coordination loop, and 3' exon binding site for in vivo excision of the Sinorhizobium meliloti group II intron RmInt1.
abstract: Excision of the bacterial group II intron RmInt1 has been demonstrated in vivo, resulting in the formation of both intron lariat and putative intron RNA circles. We show here that the bulged adenosine in domain VI of RmInt1 is required for splicing via the branching pathway, but branch site mutants produce small numbers of RNA molecules in which the first G residue of the intron is linked to the last C residue. Mutations in the coordination loop in domain I reduced splicing efficiency, but branched templates clearly predominated among splicing products. We also found that a single substitution at the EBS3 position (G329C), preventing EBS3-IBS3 pairing, resulted in the production of 50 to 100 times more RNA molecules in which the 5' and 3' extremities were joined. We provide evidence that these intron molecules may correspond to both, intron circles linked by a 2'-5' phosphodiester bond, and tandem, head-to-tail intron copies.
authors.affiliation: Grupo de Ecología Genética, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Calle Profesor Albareda 1, 18008 Granada, Spain.
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Molina-Sánchez
authors.forename: Antonio
authors.initials: A
authors.lastname: Barrientos-Durán
authors.forename: Nicolás
authors.initials: N
authors.lastname: Toro
mesh_terms: D000241:Adenosine / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D005091:Exons; D005798:Genes, Bacterial; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012329:RNA, Bacterial; D016337:RNA, Catalytic / Q000737:chemistry; D050436:Regulatory Elements, Transcriptional; D012261:Ribonucleoproteins / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000378:metabolism*
chemical_list: D012329:RNA, Bacterial; D016337:RNA, Catalytic; D012261:Ribonucleoproteins; D000241:Adenosine