library_construction_protocol: For PAR-CLIP samples, RNA was subsequently purified with acidic phenol:chloroform and ethanol precipitation. PAR-CLIP DNA library was constructed by a SMART-Seq® Stranded Kit according to the manufacturer's instructions. For PAR-CLIP experiment, the final purified library was evaluated using the Agilent 2100 TapeStation and diluted for cluster generation and high-throughput sequencing (2 × 150 bp) on NovaSeq 6000 (Illumina).