PAR-CLIP (photoactivatable ribonucleoside–enhanced cross-linking and immunoprecipitation) is a biochemical method used for identifying the binding sites of cellular RNA-binding proteins (RBPs) and microRNA-containing ribonucleoprotein complexes (miRNPs). The method relies on the incorporation of photoreactive ribonucleoside analogs, such as 4-thiouridine (4-SU) and 6-thioguanosine (6-SG) into nascent RNA transcripts by living cells. Irradiation of the cells by UV light of 365 nm induces efficient cross-linking of photoreactive nucleoside-labeled cellular RNAs to interacting RBPs. Immunoprecipitation of the RBP of interest is followed by the isolation of the cross-linked and co-immunoprecipitated RNA. The isolated RNA is converted into a cDNA library and deep sequenced using high-throughput sequencing technology. Cross-linking the 4-SU and 6-SG analogs results in thymidine to cytidine, and guanosine to adenosine transitions respectively. As a result, PAR-CLIP can identify binding site locations with high accuracy.