title: Trans-splicing and RNA editing of LSU rRNA in Diplonema mitochondria.
abstract: Mitochondrial ribosomal RNAs (rRNAs) often display reduced size and deviant secondary structure, and sometimes are fragmented, as are their corresponding genes. Here we report a mitochondrial large subunit rRNA (mt-LSU rRNA) with unprecedented features. In the protist Diplonema, the rnl gene is split into two pieces (modules 1 and 2, 534- and 352-nt long) that are encoded by distinct mitochondrial chromosomes, yet the rRNA is continuous. To reconstruct the post-transcriptional maturation pathway of this rRNA, we have catalogued transcript intermediates by deep RNA sequencing and RT-PCR. Gene modules are transcribed separately. Subsequently, transcripts are end-processed, the module-1 transcript is polyuridylated and the module-2 transcript is polyadenylated. The two modules are joined via trans-splicing that retains at the junction ∼ 26 uridines, resulting in an extent of insertion RNA editing not observed before in any system. The A-tail of trans-spliced molecules is shorter than that of mono-module 2, and completely absent from mitoribosome-associated mt-LSU rRNA. We also characterize putative antisense transcripts. Antisense-mono-modules corroborate bi-directional transcription of chromosomes. Antisense-mt-LSU rRNA, if functional, has the potential of guiding concomitantly trans-splicing and editing of this rRNA. Together, these findings open a window on the investigation of complex regulatory networks that orchestrate multiple and biochemically diverse post-transcriptional events.
authors.affiliation: Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada.
authors.forename: Matus
authors.initials: M
authors.lastname: Valach
authors.forename: Sandrine
authors.initials: S
authors.lastname: Moreira
authors.forename: Georgette N
authors.initials: GN
authors.lastname: Kiethega
authors.forename: Gertraud
authors.initials: G
authors.lastname: Burger
mesh_terms: D001483:Base Sequence; D056898:Euglenozoa / Q000235:genetics*; D008928:Mitochondria / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017393:RNA Editing; D016372:RNA, Antisense / Q000032:analysis; D000077278:RNA, Mitochondrial; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism; D020040:Trans-Splicing
chemical_list: D016372:RNA, Antisense; D000077278:RNA, Mitochondrial; D012335:RNA, Ribosomal; D012313:RNA