m6A RNA Methylation Is Regulated by MicroRNAs and Promotes Reprogramming to Pluripotency

N(6)-methyladenosine (m(6)A) has been recently identified as a conserved epitranscriptomic modification of eukaryotic mRNAs, but its features, regulatory mechanisms, and functions in cell reprogramming are largely unknown. Here, we report m(6)A modification profiles in the mRNA transcriptomes of four cell types with different degrees of pluripotency. Comparative analysis reveals several features of m(6)A, especially gene- and cell-type-specific m(6)A mRNA modifications. We also show that microRNAs (miRNAs) regulate m(6)A modification via a sequence pairing mechanism. Manipulation of miRNA expression or sequences alters m(6)A modification levels through modulating the binding of METTL3 methyltransferase to mRNAs containing miRNA targeting sites. Increased m(6)A abundance promotes the reprogramming of mouse embryonic fibroblasts (MEFs) to pluripotent stem cells; conversely, reduced m(6)A levels impede reprogramming. Our results therefore uncover a role for miRNAs in regulating m(6)A formation of mRNAs and provide a foundation for future functional studies of m(6)A modification in cell reprogramming.