Probing the microRNA pathway with small molecules.

MicroRNA (miRNA)/RNA interference (RNAi) is recognized as one of the most important mechanisms regulating gene expression at the posttranscriptional level in eukaryotic cells. The main components within the miRNA/RNAi pathway are now known and well characterized, but studies on the molecular mechanisms that regulate the activity of the miRNA/RNAi pathway are just beginning to emerge. High-throughput reporter assays have been developed to monitor the activity of the miRNA/RNAi pathway and applied in a proof-of-concept pilot screening, which has led to the identification of some inhibitors and activators that either generally or specifically regulate the activity of the miRNA/RNAi pathway. In addition, combined with multidisciplinary approaches like proteomics, biochemistry, and genetics, some protein co-factors were found to play important roles in the regulation of the miRNA/RNAi pathway. Herein we highlight the high-throughput reporter assays developed in recent years and the resulting discovery of miRNA/RNAi enhancers and inhibitors.