[RNA editing in eukaryotic genome expression]

The present review surveys the available data on the involvement of adenine deamination in RNA molecules in the formation of structurally and functionally diverse RNA and protein subforms in eukaryotic cells. Deamination of adenine by adenosine deaminases that act on RNA (ADARs) leads to the conversion of adenine into inosine (A-I editing) recognized by the splicing and translation systems as guanine. This may modify splicing sites in pre-mRNA and codons in translated regions ofmRNA and also affect the RNA secondary structure. Apart from mRNA, editing also involves microRNAs whose regulatory functions in multicellular animals are associated with the inhibition of transcription of target genes or with the degradation of certain RNA transcripts. ADARs can inhibit the production of mature microRNAs or modify microRNAs so that their specificity to target genes is altered. Adenosine deaminases editing adenines in transport RNAs (ADATs) convert adenine into inosine in tRNAs of all eukaryotes; as a result, the diversity of tRNA forms in the cell increases.