Fig. 2
From: Small RNA modifications: regulatory molecules and potential applications
The m6A modification in miRNA. A. The chemical structure of adenosine and the site of methylation on N6 are shown alongside the enzymes (writers, eraser and readers) known to be involved. B. The m6A modification of pri-miRNA mediated by METTL3 or METTL14 is recognized by HNRNPA2/B1, so as to promote the interaction between DGCR8 and pri-miRNA, leading to acceleration of miRNA biosynthesis. On the contrary, ALKBH15 demethylates pri-miRNA, preventing DGCR8 from interacting with pri-miRNA, and this results in blockade of mature miRNA synthesis. HNR-: HNRNPA2/B1. C. The m6A modification in pre-miRNA mediated by METTL3 promotes the binding of Dicer to pre-miRNA which, in turn, accelerates the biosynthesis of miRNA (note that the specific m6A modification sites remain unknown). D. While studies have found that m6A modifications can be detected on mature miRNAs, the origin and biological relevance of such modifications remains to be better characterized