Identification of miRNA-Target RNA Interactions Using CLASH.

We present a detailed protocol for the experimental identification of miRNA-target RNA interaction sites using cross-linking, ligation, and sequencing of hybrids (CLASH). The basis of the technique is the purification of UV-stabilized Argonaute (AGO)-RNA complexes assembled in living cells, with subsequent ligation of AGO-associated RNA-RNA duplexes to form chimeric RNAs. Following cDNA synthesis, DNA library preparation and high-throughput sequencing, interacting RNA molecules are unambiguously identified as chimeric reads in bioinformatic analysis of sequencing data. CLASH potentially recovers any RNA duplex that is bound by RNA-binding protein, so modified approaches would be suitable for the identification of many other inter- and intramolecular RNA-RNA interactions. Since CLASH analysis is independent of bioinformatic predictions it allows the identification and analysis of RNA targeting rules in an unbiased way.