title: Selection of circularization sites in a group I IVS RNA requires multiple alignments of an internal template-like sequence.
abstract: Circularization and reverse circularization of the Tetrahymena thermophila rRNA intervening sequence resemble the first and second steps in splicing, respectively. However, site-specific base substitutions show that different nucleotides are involved in selection of the 5' splice site and the circularization sites. Furthermore, a substitution at the major circularization site that prevents circularization can be suppressed by second substitutions at two different nucleotide positions. A model is proposed in which adjacent and overlapping sequences can function as a binding site, forming a short duplex with the sequence at the circularization site and thus directing circularization and reverse circularization. Because the 5' exon-binding site and three potential circularization binding sites fall within a contiguous eight nucleotide region, this sequence may translocate relative to the catalytic core of the ribozyme in a template-like manner.
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D007438:Introns; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D012313:RNA / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D000079962:RNA, Circular; D012335:RNA, Ribosomal / Q000378:metabolism*; D013698:Templates, Genetic; D013768:Tetrahymena / Q000378:metabolism*
chemical_list: D000079962:RNA, Circular; D012335:RNA, Ribosomal; D012313:RNA