An adenosine-to-inosine tRNA-editing enzyme that can perform C-to-U deamination of DNA.
Rubio MA, Pastar I, Gaston KW, Ragone FL, Janzen CJ, Cross GA, Papavasiliou FN, Alfonzo JD.
Department of Microbiology and the Ohio State RNA Group, Ohio State University, Columbus, OH 43210, USA.
Abstract
Adenosine-to-inosine
editing in the anticodon of tRNAs is essential for viability. Enzymes
mediating tRNA adenosine deamination in bacteria and yeast contain
cytidine deaminase-conserved motifs, suggesting an evolutionary link
between the two reactions. In trypanosomatids, tRNAs undergo both
cytidine-to-uridine and adenosine-to-inosine editing, but the
relationship between the two reactions is unclear. Here we show that
down-regulation of the Trypanosoma brucei tRNA-editing enzyme by RNAi
leads to a reduction in both C-to-U and A-to-I editing of tRNA in vivo.
Surprisingly, in vitro, this enzyme can mediate A-to-I editing of tRNA
and C-to-U deamination of ssDNA but not both in either substrate. The
ability to use both DNA and RNA provides a model for a multispecificity
editing enzyme. Notably, the ability of a single enzyme to perform two
different deamination reactions also suggests that this enzyme still
maintains specificities that would have been found in the ancestor
deaminase, providing a first line of evidence for the evolution of
editing deaminases.
