Background: RNA molecules play crucial roles in various biological processes. Their regulation and function are mediated by interacting with other molecules. Among them RNA-RNA interactions (RRIs) are important in many basic cellular activities including transcription, RNA processing, localization, and translation. However, we just start to unveil the complexity of the knowledge and underlying mechanisms of RRIs. Results: In this review, we will summarize approaches for RRI identifications, including both conventional, focused biophysical and biochemical methods and recently developed large scale sequencing-based techniques. We will also discuss discoveries per RRI type revealed by using these technologies, as well as challenges towards a systematic and functional understanding of RRIs. Conclusions: The development of sequencing-based techniques has revolutionized the study of RRIs. Applying these techniques in multiple organisms has identified thousands of RRIs, many of which could potentially regulate multiple aspects of gene expression. However, despite the great breakthrough, the RNA-RNA interactome of any species remains far from complete due to intrinsic complex nature of RRI and limitations in current techniques. More efficient experimental methods and computational framework are needed to obtain the full image of RRI networks, and their possible regulatory roles in biology and medicine.

RNA-RNA interactions (RRIs) are essential to understanding the regulatory mechanisms of RNAs. Mapping RRIs in vivo in a transcriptome-wide manner remained challenging until the recent development of several sequencing-based technologies. However, RRIs generated from large-scale studies had not been systematically collected and analyzed before. This article introduces RISE, a database of the RNA Interactome from Sequencing Experiments. RISE provides a comprehensive collection of RRIs in human, mouse, and yeast, derived from transcriptome-wide sequencing experiments, as well as targeted sequencing studies and other public databases/datasets. To facilitate better understanding of the biological roles of these RRIs, RISE also offers rich functional annotations involving RNAs, and an interactive interface to explore the analysis results. Here, we provide a brief description of the RISE website and a step-by-step protocol for using RISE to study RRIs. C 2018 by John Wiley & Sons, Inc.Keywords: interaction r RISE r RNA r RNA-RNA r RNA structure r sequencing experiments