library_construction_protocol: NKX2-1 antibody (EMD Millipore, cat. #07-601) and SOX2 antibody (Abcam, cat. #ab97959) were used to perform ChIP-seq in 8 million SHP77 cells. ChIP DNA was decrosslinked at 65C overnight and purified with MinElute PCR purification kit (Qiagen, cat. #28006). ChIP-seq library was generated with Takara ThruPLEX DNA-seq kit (cat. #R400677) according to the manufacturer's protocol. SMARTer DNA Unique Dual Index Kit - 24U Set B (Takara, cat. #R400666) was used to index and multiplex the samples for sequencing. AMPure XP beads (Beckman Coulter, cat. #A63881) were used for library size selection to 200-500 bp and final library quality was evaluated on BioAnalyzer 2100 with Agilent high sensitivity DNA kit (cat. #5067-4626).