title: Trypanosoma brucei RNA editing: coupled cycles of U deletion reveal processive activity of the editing complex.
abstract: RNA editing in Trypanosoma brucei is posttranscriptional uridylate removal/addition, generally at vast numbers of pre-mRNA sites, but to date, only single editing cycles have been examined in vitro. We here demonstrate achieving sequential cycles of U deletion in vitro, with editing products confirmed by sequence analysis. Notably, the subsequent editing cycle is much more efficient and occurs far more rapidly than single editing cycles; plus, it has different recognition requirements. This indicates that the editing complex acts in a concerted manner and does not dissociate from the RNA substrate between these cycles. Furthermore, the multicycle substrate exhibits editing that is unexpected from a strictly 3'-to-5' progression, reminiscent of the unexpected editing that has been shown to occur frequently in T. brucei mRNAs edited in vivo. This unexpected editing is most likely due to alternate mRNA:guide RNA (gRNA) alignment forming a hyphenated anchor; its having only a 2-bp proximal duplex helps explain the prevalence of unexpected editing in vivo. Such unexpected editing was not previously reported in vitro, presumably because the common use of artificially tight mRNA:gRNA base pairing precludes alternate alignments. The multicycle editing and unexpected editing presented in this paper bring in vitro reactions closer to reproducing the in vivo editing process.
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Vadim S
authors.initials: VS
authors.lastname: Alatortsev
authors.forename: Jorge
authors.initials: J
authors.lastname: Cruz-Reyes
authors.forename: Alevtina G
authors.initials: AG
authors.lastname: Zhelonkina
authors.forename: Barbara
authors.initials: B
authors.lastname: Sollner-Webb
mesh_terms: D000818:Animals; D020137:Base Pair Mismatch; D001483:Base Sequence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000502:physiology; D017393:RNA Editing; D017394:RNA, Guide, Kinetoplastida / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000235:genetics*; D014529:Uridine / Q000378:metabolism*
chemical_list: D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D014529:Uridine; D017394:RNA, Guide, Kinetoplastida