RNA Editing Accessory Factors — the Example of mHel61p

Abstract

The majority of mitochondrial pre-messenger RNAs in kinetoplastid protozoa are substrates of a U nucleotide-specific, insertion/deletion-type RNA editing reaction. The process converts nonfunctional pre-mRNAs into translatable molecules, and can generate protein diversity by alternative editing. A high molecular mass enzyme complex, the editosome, catalyzes the reaction. Editosomes provide a molecular platform for the individual catalytic steps of the reaction cycle. While the molecular composition of the editosome has been studied in detail, dynamic aspects of the reaction have by and large been ignored. Here, we focus on accessory proteins that bind to the editosome only at defined steps of the reaction cycle, thereby modulating the structure and function of the catalytic machinery. As an example, we concentrate on the mitochondrial DExH/D protein mHel61p, a putative RNA helicase and/or RNPase. We summarize the current structural, genetic and biochemical knowledge on mHel61p, and provide an outlook onto dynamic processes of the editing reaction.