MicroRNA biogenesis: Epigenetic modifications as another layer of complexity to the microRNA expression regulation

Since their discovery, microRNAs have led to a huge shift in our understanding of the regulation of key biological processes. The discovery of epigenetic modifications that affect microRNA expression has added another layer of complexity to the already tightly controlled regulatory machinery. Modifications like uridylation, adenylation and RNA editing have been shown to have variable effects on miRNA biogenesis and action. Methylation of the N6 adenosine has been studied extensively in mRNA. Presence of the N6-methyl-adenosine (m 6 A) mark and its critical importance in miRNA biogenesis in animals adds to our understanding of the regulatory mechanisms, while its effect on miRNA biogenesis in plants is yet to be understood.