RNA Editing Adds Flavor to Complexity

A-to-I RNA editing results in the conversion of single adenosines into inosines, which alters coding and non-coding sequences in RNA molecules, increasing the complexity of the transcriptome. This modification is vital in a number of brain-specific coding transcripts, where the introduced alternative amino acids impact protein function substantially. Indeed, deviations from normal editing levels have been detected in tissues from individuals affected by neurological diseases and cancer, underscoring the importance of correct and regulated editing. Since the discovery of A-to-I RNA editing, considerable effort has been made to uncover additional editing targets and analyze the subsequent functional consequences for the recoded substrates. The effects of editing on non-coding RNAs (ncRNAs) such as microRNAs (miRNAs) or long ncRNAs are less well explored. ncRNAs act as regulators of gene expression through chromatin modification, imprinting, alternative splicing, and mRNA translation and stability. Editing has the potential to dynamically alter and diversify ncRNAs, thereby redirecting their functions. How editing intersects, interferes with, and modulates the roles of ncRNAs, possibly in response to external stimuli, therefore warrants a deeper look. This review discusses recent advances and new insights in the field.