Insight into m6A methylation from occurrence to functions.

RNA m6A methylation is a post-transcriptional modification that occurs at the nitrogen-6 position of adenine. This dynamically reversible modification is installed, removed and recognized by methyltransferases, demethylases and readers, respectively. This modification has been found in most eukaryotic mRNA, tRNA, rRNA and other non-coding RNA. Recent studies have revealed important regulatory functions of the m6A including effects on gene expression regulation, organism development and cancer development. In this review, we summarize the discovery and features of m6A, and briefly introduce the mammalian m6A writers, erasers and readers. Finally, we discuss progress in identifying additional functions of m6A and the outstanding questions about the regulatory effect of this widespread modification.