title: Protein-dependent splicing of a group I intron in ribonucleoprotein particles and soluble fractions.
abstract: The group I intron in the Neurospora mitochondrial large rRNA gene is not self-splicing in vitro. Here, we show that this intron can be spliced from 35S pre-rRNA in RNPs or from deproteinized 35S pre-rRNA or in vitro transcripts by a soluble activity that is present in mitochondrial lysates and can be released from RNPs. Splicing occurs by the same guanosine-initiated transesterification mechanism characteristic of self-splicing group I introns, but is absolutely dependent upon proteins that are presumably required for correct folding of the pre-rRNA. The soluble splicing activity is not simply associated with large subunit ribosomal proteins. Nuclear mutant cyt18-1, which is defective in splicing a number of group I introns in vivo, is grossly deficient in the soluble splicing activity. Our results suggest that the cyt18 gene encodes or regulates a component of an activity that functions in splicing group I introns in Neurospora mitochondria.
mesh_terms: D001483:Base Sequence; D005656:Fungal Proteins / Q000502:physiology*; D008928:Mitochondria / Q000201:enzymology; D009491:Neurospora / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009694:Nucleic Acid Precursors / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012322:RNA Precursors; D012326:RNA Splicing; D012331:RNA, Fungal / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D009694:Nucleic Acid Precursors; D012322:RNA Precursors; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D012261:Ribonucleoproteins; D012313:RNA