RNA Editing

RNA editing is one of the most striking phenomena observed in the mitochondria of kinetoplastids including Trypanosoma and Leishmania. In this process, mitochondrial (mt) pre-mRNA, encoded by the kinetoplast DNA (kDNA) maxicircles, is posttranscriptionally modified by insertion and deletion of uridine nucleotide (U) residues under the direction of small RNAs, termed guide RNAs (gRNAs). It is a form of RNA processing that finally results in the formation of mature translatable mRNA, but it is distinct from the widely occurring RNA splicing and other types of RNA processing, since additional sequences in the form of U residues are created after transcription. Trypanosome RNA editing is catalyzed by multiprotein complexes (editosomes) and occurs at multiple sites, contributing over half of the protein-coding residues of certain mRNAs. The number of minicircles present in kDNA is sufficient to encode all the gRNAs required for editing of the mitochondrial transcripts. Trypanosoma brucei...