We developed a robust computational statistical framework to identify RNA editing events from RNA-Seq data with high specificity. Our approach handles several outstanding challenges of genome-wide editing analyses, including the effect of editing on read alignment and the utilization of redundant reads. By applying this framework, we characterized the nuclear and cytosolic editomes of seven human cell lines. We found that 93.8-99.2% of the editing events are A-to-G (or A-to-I). Nuclear transcriptomes contain many more editing events than cytosolic transcriptomes. Most of the sites exhibiting nucleus-specific editing are in introns or novel intergenic transcripts that are preferentially localized in the nucleus regardless of their editing status, arguing against the role of editing in nuclear retention. In contrast, many sites that exhibit cytosol-specific editing show comparable nuclear and cytosolic expression, suggesting the differential subcellular compartmentalization of the edited and the unedited alleles. We found that RNA editing is globally associated with the modification of microRNA regulation in 3′ untranslated regions, whereas editing events in coding regions are rare and tend to be synonymous. Interestingly, A-to-G editing at derived alleles in the human lineage tends to result in reversion back to the ancestral forms at the RNA level. This suggests that editing can mediate RNA memory on evolutionary time-scales to maintain ancestral genetic information.high-throughput sequencing | nucleo-cytoplasmic localization A lthough high-throughput sequencing has facilitated the identification of genetic DNA variants, the identification of RNA editing is much more challenging owing to the uneven read distribution in RNA sequencing and the varied RNA editing rates. Errors in base calling and read alignment, the handling of redundant reads, and other systematic sequencing errors all hinder the single-nucleotide-level analysis of RNA editing. Early analyses of high-throughput sequencing data reported more than 10,000 exonic editing events, many of which were non-A-to-G (1). However, recent studies argued that many of these non-A-to-G editing events were false positives resulting from inappropriate bioinformatic analyses (2-4). To deal with multiple sources of potential errors, the existing tools for editing discovery (5-7) usually involve comprehensive pipelines packed with multiple read aligners, read simulations, and various filters. Meanwhile, many critical issues in editing discovery remain to be addressed more properly. For example, the existing methods remove a large number of redundant reads starting from the same positions, although in deep sequencing many redundant reads can result from true expression and are useful for estimating editing levels. Moreover, the effect of editing on read alignment has been commonly overlooked.Herein, we developed an efficient and robust computational statistical framework for RNA editing discovery. This framework considers the effect of editing on read alignment and hand...