Mechanisms and origins of RNA editing

RNA editing is an essential post-transcriptional process that has been identified in an increasing number of eukaryotic organisms. In the past year, progress has been made in the development of in vitro systems to study the mechanism of RNA editing. Analysis of nucleotide insertion/deletion editing in trypanosome mitochondria has revealed the existence of putative editing intermediates in vivo and in vitro. The development of an in vitro editing system for mammalian apolipoprotein B mRNA has allowed the elucidation of both the sequence requirements and the biochemical mechanism of this form of RNA editing. In addition, recent work has underscored the diversity of RNAs whose structure and function are altered by post-translational editing reactions.