C to U editing stimulates A to I editing in the anticodon loop of a cytoplasmic threonyl tRNA in Trypanosoma brucei.
Rubio MA, Ragone FL, Gaston KW, Ibba M, Alfonzo JD.
Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, USA.
Abstract
Editing
of tRNAs is widespread in nature and either changes the decoding
properties or restores the folding of a tRNA. Unlike the
phylogenetically disperse adenosine (A) to inosine (I) editing, cytosine
(C) to uridine (U) editing has only been previously described in
organellar tRNAs. We have shown that cytoplasmic tRNA(Thr)(AGU)
undergoes two distinct editing events in the anticodon loop: C to U and A
to I. In vivo, every inosine-containing tRNA(Thr) is also C to U edited
at position 32. In vitro, C to U editing stimulates conversion of A to I
at the wobble base. Although the in vivo and in vitro requirements
differ, in both cases, the C to U change plays a key role in A to I
editing. Due to an unusual abundance of A34-containing tRNAs, our
results also suggest that the unedited and edited tRNAs are functional,
each dedicated to decoding a specific threonine codon. C to U editing of
cytoplasmic tRNA expands the editing repertoire in eukaryotic cells,
and when coupled to A to I changes, leads to an interrelation between
editing sites.
