title: Trypanosoma brucei RNA editing complex: band II is structurally critical and maintains band V ligase, which is nonessential.
abstract: Maturation of Trypanosoma brucei mitochondrial mRNA involves massive posttranscriptional insertion and deletion of uridine residues. This RNA editing utilizes an enzymatic complex with seven major proteins, band I through band VII. We here use RNA interference (RNAi) to examine the band II and band V proteins. Band II is found essential for viability; it is needed to maintain the normal structure of the editing complex and to retain the band V ligase protein. Previously, band III was found essential for certain activities, including maintenance of the editing complex and retention of the band IV ligase protein. Thus, band II and band V form a protein pair with features analogous to the band III/band IV ligase pair. Since band V is specific for U insertion and since band IV is needed for U deletion, their parallel organization suggests that the editing complex has a pseudosymmetry. However, unlike the essential band IV ligase, RNAi to band V has only a morphological but no growth rate effect, suggesting that it is stimulatory but nonessential. Indeed, in vitro analysis of band V RNAi cell extract demonstrates that band IV can seal U insertion when band V is lacking. Thus, band IV ligase is the first activity of the basic editing complex shown able to serve in both forms of editing. Our studies also indicate that the U insertional portion may be less central in the editing complex than the corresponding U deletional portion.
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Sean F
authors.initials: SF
authors.lastname: O'Hearn
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Huang
authors.forename: Mike
authors.initials: M
authors.lastname: Hemann
authors.forename: Alevtina
authors.initials: A
authors.lastname: Zhelonkina
authors.forename: Barbara
authors.initials: B
authors.lastname: Sollner-Webb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017125:Genes, Protozoan; D046911:Macromolecular Substances; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011118:Polynucleotide Ligases / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017393:RNA Editing; D034622:RNA Interference; D016053:RNA, Protozoan / Q000378:metabolism*; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D016053:RNA, Protozoan; D011118:Polynucleotide Ligases; C436705:band V ligase