Unusual Noncanonical Intron Editing Is Important for tRNA Splicing in Trypanosoma brucei

• Published in: Molecular cell 2013-10, Vol.52 (2), p.184-192
• Main Authors: Rubio, Mary Anne T, Paris, Zdeněk, Gaston, Kirk W, Fleming, Ian M.C, Sample, Paul, Trotta, Christopher R, Alfonzo, Juan D
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Archaea; Base Sequence; Blotting, Northern; codons; Endoribonucleases - genetics; Endoribonucleases - metabolism; eukaryotic cells; introns; Introns - genetics; Molecular Sequence Data; Nucleic Acid Conformation; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA Editing; RNA Interference; RNA Precursors - genetics; RNA Precursors - metabolism; RNA Processing, Post-Transcriptional; RNA Splicing; RNA, Protozoan - genetics; RNA, Protozoan - metabolism; RNA, Transfer, Tyr - chemistry; RNA, Transfer, Tyr - genetics; RNA, Transfer, Tyr - metabolism; Sequence Homology, Amino Acid; transfer RNA; Trypanosoma brucei; Trypanosoma brucei brucei - genetics; Trypanosoma brucei brucei - metabolism; tyrosine; viability
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2013.08.042

In cells, tRNAs are synthesized as precursor molecules bearing extra sequences at their 5′ and 3′ ends. Some tRNAs also contain introns, which, in archaea and eukaryotes, are cleaved by an evolutionarily conserved endonuclease complex that generates fully functional mature tRNAs. In addition, tRNAs undergo numerous posttranscriptional nucleotide chemical modifications. In Trypanosoma brucei, the single intron-containing tRNA (tRNAᵀʸʳ GUA) is responsible for decoding all tyrosine codons; therefore, intron removal is essential for viability. Using molecular and biochemical approaches, we show the presence of several noncanonical editing events, within the intron of pre-tRNAᵀʸʳ GUA, involving guanosine-to-adenosine transitions (G to A) and an adenosine-to-uridine transversion (A to U). The RNA editing described here is required for proper processing of the intron, establishing the functional significance of noncanonical editing with implications for tRNA processing in the deeply divergent kinetoplastid lineage and eukaryotes in general.