The microRNA-17∼92 cluster Still a miRacle?

MicroRNAs (miRs) are small non-coding RNAs that regulate gene expression by binding to target mRNAs, leading to translational repression or degradation. The polycistronic microRNA cluster comprises seven mature microRNAs (miR-17-5p and -3p, miR-18a, miR-19a and b, miR-20a and miR-92a) and has initially been linked to tumorigenesis. Meanwhile, additional functions have been assigned to the cluster such as the regulation of hematopoiesis and immune functions. Recently, loss-off-function studies revealed a critically role of the miR-17 similar to 92 cluster in heart and lung development and the individual miRNAs encoded by the cluster such as miR-17 and miR-92a were shown to control lung development and postnatal neovascularization, respectively. The present article summarizes the functions of the miR-17 similar to 92 cluster in health and disease and discusses the specific contribution and the targets of the individual miRNAs encoded by the cluster.