from Jonatha M. Gott writing in RNA Editing: Current Research and Future Trends:

Mitochondrial RNAs in the acellular slime mold Physarum polycephalum are subject to the widest range of editing events observed thus far. Mitochondrial RNAs differ from the mitochondrial genome at over 1300 sites, and both coding (mRNAs) and non-coding RNAs (rRNAs and tRNAs) are affected. At least three distinct editing mechanisms are needed to account for the different forms of editing observed in the mitochondrial transcriptome: nucleotide insertions and deletions, C to U changes, and specific alterations at the 5' end of tRNAs. Nucleotide insertions are co-transcriptional and require flanking regions of the template, but the exact signals that specify the site of nucleotide insertion and the identity of the nucleotide to be added remain an enigma. The rare instances of base changes and replacement of the first nucleotide of mitochondrial tRNAs are not directly linked to transcription and are likely to occur via processes related to those previously described in other mitochondrial editing systems.

Further reading: RNA Editing: Current Research and Future Trends

from Meng How Tan and Jin Billy Li writing in RNA Editing: Current Research and Future Trends:

RNA editing is a post-transcriptional mechanism whereby genomically encoded information is altered at the level of the transcript. We describe in this review how RNA editing sites can be identified. The pace of discovery in the past few decades was dependent on the sequencing technologies available at a particular time. At the beginning when DNA sequencing had just been developed and automated, the identification of RNA editing sites was slow and often occurred by chance. Over time, as more and more sequences were deposited in databases, it became possible for scientists to computationally mine the databases for more editing sites. In recent years, with the development of ultra-high throughput sequencing technologies whereby millions to billions of DNA molecules are sequenced simultaneously, scientists can now uncover RNA editing sites in a genome-wide manner. However, extra care has to be taken during the analysis process to remove artifacts and to ensure that true editing sites are identified.

Further reading: RNA Editing: Current Research and Future Trends

from Harold C. Smith writing in RNA Editing: Current Research and Future Trends:

Two decades of research revealed the mechanism for site-specific, apolipoprotein B (apoB) mRNA C to U editing and its developmental and metabolic regulation. The field began to lose momentum while many open questions remained. This was due to perceived impasses in translational research endpoints: (1) liver is the most significant organ in the metabolism of cholesterol- and triglyceride-rich lipoproteins and despite active and regulated hepatic editing in rodent models, human liver does not express the cytidine deaminase APOBEC1 required for apoB mRNA editing. (2) Mammals express APOBEC1 in their small intestines where 100% of the apoB mRNA is edited in adults but this activity is constitutive. (3) Expression of APOBEC1 is not essential for life in mice. In the past few years there has been a resurgence in interest because: (1) APOBEC1 edits the 3' UTRs of multiple mRNAs and either alone or together with its RNA-binding cofactor, A1CF, may regulate mRNA stability and translation in diverse tissues. (2) A1CF is required for embryological development, acting through a mechanism that may be unrelated to APOBEC1. (3) Discovery of dC to dU DNA mutational activity by APOBEC1 raises new questions of its oncogenic potential. This review will consider past and current discoveries relative to the exciting new research opportunities in the field.

Further reading: RNA Editing: Current Research and Future Trends

from Jorge Cruz-Reyes and Laurie K. Read writing in RNA Editing: Current Research and Future Trends:

The extraordinary RNA editing by U insertion and U deletion in mitochondrial mRNAs is arguably the best characterized process in kinetoplastids. However, much less is known about ancilliary factors of the editing multiprotein enzyme core. This enzyme architecture and basic catalysis guided by small non-coding gRNAs have enjoyed central stage, compared to other aspects in the biology of editing substrates, from biogenesis to translation. Many mRNAs and thousands of gRNAs are undoubtedly targeted by numerous factors that regulate unwinding, annealing, stability, assembly into editing enzymes, and translation. Recent years have seen a virtual explosion in the discovery of editing accessory factors. This review discusses the progress in this area, and frames a working model whereby the editing machinery is functionally and physically linked to pre and post editing events through a dynamic higher-order network of protein and RNA interactions.

Further reading: RNA Editing: Current Research and Future Trends

from Sara Tomaselli, Federica Galeano, Franco Locatelli and Angela Gallo writing in RNA Editing: Current Research and Future Trends:

All viruses that have dsRNA structures at any stages of their life cycle may potentially undergo RNA editing mediated by ADAR enzymes. Indeed, a number of reports describe A-to-I sequence changes in viral genomes and/or transcripts that are consistent with ADAR activity. These modifications can appear as either hyperediting during persistent viral infections or specific RNA editing events in viral dsRNAs. It is now well established that ADAR enzymes can affect virus interaction with their host in both an editing-dependent and -independent manner, with ADARs playing for both sides: the host and the virus. Despite the discovery of editing events on viral RNA dates back to thirty years ago, the biological consequences of A-to-I changes during viral infection is still far to be completely elucidated. In particular, the proviral role played by ADAR1, partly due to PKR inhibition, together with its antiviral effect following hyperediting events, put in evidence the complex role played by RNA editing in the regulation of viral infections and innate immune response.

Further reading: RNA Editing: Current Research and Future Trends