MicroRNAs: Mechanisms, Functions and Progress

In 1993 when Ambros and co-workers [1] discovered that a mysterious Caenorhabditis elegans gene, lin-4, does not encode a protein, but acts in the form of a small RNA and represses the expression of its target gene, lin-14, through base-pairing with its 30 untranslated region (30UTR), nobody would imagine that 20 years later, this category of small RNAs – now widely known as microRNAs (or miRNAs), has 2000 known members in the human genome (and counting), and that miRNA-mediated gene regulation is deeply involved in virtually all important biological processes in animals and plants. There is little doubt that recent advances in genomics and bioinformatics technologies and methodologies have made considerable contributions to our understanding of miRNAs [2]. We present this special issue as an attempt to bring readers an update on the current understanding of the biogenesis and targeting of miRNAs, and some of the most recent developments in the exciting field of miRNA research. Grave and Zeng’s review entitled “Biogenesis of mammalian microRNAs: a global view” [3] offers an upto-date overview of the mechanisms by which a miRNA executes its function. Reyes-Herrera and Ficarra’s “One decade of development and evolution of microRNA target prediction algorithms” [4] and Ding et al.’s “Finding miRNA targets in plants: current status and perspectives” [5] provide a comprehensive survey of the current methods for the identification of miRNA targets in animals and plants, respectively. In addition, Li and Kowdley [6] bring us an up-to-date review about the involvement of miRNAs in human diseases.