Functions and mechanisms of RNA editing

RNA editing can be broadly defined as any site-specific alteration in an RN A sequence that could have been copied from the template, excluding changes due to processes such as RNA splicing and polyadenylation. Changes in gene expression attributed to editing have been described in organisms from uni cellular protozoa to man, and can affect the mRNAs, tRNAs, and rRNAs presen t in all cellular compartments. These sequence revisions, which include bot h the insertion and deletion of nucleotides, and the conversion of one base to another, involve a wide range of largely unrelated mechanisms. Recent a dvances in the development of in vitro editing and transgenic systems for t hese varied modifications have provided a better understanding of similarit ies and differences between the biochemical strategies, regulatory sequence s, and cellular factors responsible for such RNA processing events.