title: Processing of yeast mitochondrial RNA: involvement of intramolecular hybrids in splicing of cob intron 4 RNA by mutation and reversion.
abstract: Revertants have been obtained from six mutants of the box9 cluster, which are supposed to be defective in RNA splicing as a result of alterations in a splice signal sequence. This sequence is in the 5' part of intron 4 of the cob gene, 330 to 340 bp downstream from the 5' splice site. Sequencing reveals that reversion to splicing competence is achieved by restoration of the wild-type box9 sequence; by creation of novel box9 sequences; and by introduction of a second site or suppressor mutation (sup-) compensating for the effect of the primary box9- mutation. The sup- mutation alters a sequence in intron 4,293 bp upstream from the box9- primary mutation. The box9 sequence and this upstream sequence can base pair to form an intramolecular hybrid in intron RNA in which box9- and sup- are compensatory base pair exchanges (G----A and C----U, respectively). Thus intramolecular hybrid structures of intron RNA are essential for RNA splicing.
mesh_terms: D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics; D008928:Mitochondria / Q000502:physiology*; D009154:Mutation; D009690:Nucleic Acid Conformation; D012323:RNA Processing, Post-Transcriptional; D012326:RNA Splicing; D012331:RNA, Fungal / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013489:Suppression, Genetic
chemical_list: D004272:DNA, Mitochondrial; D012331:RNA, Fungal