On the origin, evolution, and maintenance of RNA editing.

A newly published review by Bendich and Rogers (The biological and evolutionary consequences of competition between DNA sequences that benefit the cell and DNA sequences that benefit themselves. Nucleic Acids Research2025;53:gkaf589.) discusses the origin of RNA editing as a defense against mobile genetic elements (MGEs) and points out that many recent reviews, including ours, failed to recognize this fundamental issue. In this article, we expand on this perspective by examining the mechanistic and theoretical gaps regarding whether RNA editing suppresses or tolerates TE proliferation. We highlight the relevance of constructive neutral evolution (CNE) theory, suggesting that regardless of whether the editing machinery has arisen via CNE, specific editing sites do exhibit CNE signals. Additionally, we explore why certain A-to-I recoding sites are selectively maintained without being replaced with genomic G, reinforcing their indispensable regulatory role. Taken together, while acknowledging the plausibility of the MGE-related origin, we advocate for a broader view of RNA editing that includes multiple fascinating functions like proteome diversification and mutation correction.