However, PAR-CLIP is limited to cultured cells, and nucleoside cytotoxicity is a concern; it has been reported that 4-SU inhibits ribosomal RNA synthesis, induces a nucleolar stress response, and reduces cell proliferation.
Recently, PAR-CLIP has been employed to determine the transcriptome-wide binding sites of several known RBPs and microRNA-containing ribonucleoprotein complexes at high resolution.