RNA <i>N</i>⁶-methyladenosine methylation in post-transcriptional gene expression regulation

N(6)-methyladenosine (m(6)A) is the most prevalent and internal modification that occurs in the messenger RNAs (mRNA) of most eukaryotes, although its functional relevance remained a mystery for decades. This modification is installed by the m(6)A methylation "writers" and can be reversed by demethylases that serve as "erasers." In this review, we mainly summarize recent progress in the study of the m(6)A mRNA methylation machineries across eukaryotes and discuss their newly uncovered biological functions. The broad roles of m(6)A in regulating cell fates and embryonic development highlight the existence of another layer of epigenetic regulation at the RNA level, where mRNA is subjected to chemical modifications that affect protein expression.