Processing of the Intron-Encoded U18 Small Nucleolar RNA in the Yeast Saccharomyces cerevisiae Relies on Both Exo- and Endonucleolytic Activities

摘要: Many small nucleolar RNAs (snoRNAs) are encoded within introns of protein-encoding genes and released by processing their host pre-mRNA. We have investigated the mechanism yeast U18 snoRNA, which is found in intron gene coding for translational elongation factor EF-1β. focused our analysis on relationship between splicing EF-1β pre-mRNA production mature snoRNA. Mutations inhibiting been shown to produce normal snoRNA levels together with accumulation intermediates deriving from pre-mRNA, thus indicating that precursor an efficient substrate. Inhibition 5′→3′ exonucleases obtained insertion G cassettes or use a rat1-1 xrn1Δ mutant strain does not impair release. In Exo− strain, 3′ cutoff products, diagnostic endonuclease-mediated pathway, were detected. Our data indicate biosynthesis relies two different pathways, depending both exonucleolytic endonucleolytic activities: major pathway based conversion debranched minor one acting cleavage