Total RNA was extracted from human samples using TRIzol reagent. RNA concentration, purity and integrity were assessed via NanoDrop ND-1000 and agarose gel electrophoresis. Qualified RNA was used for BID-seq library construction. 3' and 5' adapters were sequentially ligated to fragmented RNA using the GenSeq Small RNA Library Prep Kit (GenSeq, Inc.). One portion of adapter-ligated RNA was used to construct Input libraries (Control1-Control5, PH1-PH5). The remaining RNA was incubated with bisulfite reagent at 70 °C for 3 hours, followed by desulfonation in RNA Desulphonation Buffer (Zymo Research) at room temperature for 1 hour to generate treated samples (Control1-Control5, PH1-PH5). Both Input and treated RNA were used for cDNA synthesis and PCR amplification. Libraries were purified by gel extraction and sequenced on Illumina platform with 150 bp single-end mode.