library_construction_protocol: Total RNA was rRNA depleted with Ribo-zero (Illumina) and then subjected to immunoprecipitation with the GenSeqTM ac4C-IP Kit (GenSeq Inc., China) by following the manufacturer's instructions. RNA was randomly fragmented to ~200 nt by RNA Fragmentation Reagents. Protein A/G beads were coupled to the ac4C antibody by rotating at room temperature for 1 h. The RNA fragments were incubated with the bead-linked antibodies and rotated at 4°C for 4 h. The RNA/antibody complexes are then digested with Proteinase K and the eluted RNA is purified by phenol:chloroform extraction. RNA libraries for IP and input samples were then constructed with NEBNext® Ultra II Directional RNA Library Prep Kit (New England Biolabs, Inc., USA) by following the manufacturer's instructions. Libraries were qualified using Agilent 2100 bioanalyzer and then sequenced in a HiSeq platform (Illumina) ac4c RIP-seq