The identification of m ⁶ A demethylases and high-throughput sequencing analysis of methylated transcriptome corroborated m ⁶ A RNA epigenetic modification as a dynamic regulation process, and reignited its investigation in the past few years. Many basic concepts of cytogenetics have been revolutionized by the growing understanding of the fundamental role of m ⁶ A in RNA splicing, degradation and translation. In this review, we summarize typical features of methylated transcriptome in mammals, and highlight the ‘writers’, ‘erasers’ and ‘readers’ of m ⁶ A RNA modification. Moreover, we emphasize recent advances of biological functions of m ⁶ A and conceive the possible roles of m ⁶ A in the regulation of immune response and related diseases.