library_construction_protocol: Add a final concentration of 1% formaldehyde solution for cross-linking DNA and protein. Stop the cross-linking reaction by adding a final concentration of 125 mM glycine. Extract chromatin from cross-linked cells by adding lysis buffer. Sonicate chromatin DNA to fragments ranging from 100 to 500 bp. Incubate chromatin DNA and antibody-associated beads overnight at 4°C to immunoprecipitate. Wash Dynabeads using an optimal method for eluting the immunoprecipitated protein-DNA complexes. Generate sequencing libraries of immunoprecipitated chromatin DNA using the NEBNext® Ultra™ DNA Library Prep Kit for Illumina. Add End Repair Reaction Buffer (10X) and End Prep Enzyme Mix for end repair under the following conditions: 20°C for 30 min, 65°C for 30 min. Add NEBNext Adaptor and Blunt/TA Ligase Master Mix to ligate the adaptor at 20°C for 15 min. Then add USER Enzyme to remove base U of the adaptor at 37°C for 5 min. After purification with beads, amplify the products with PCR under the following conditions: initial denaturation at 98°C for 10 sec; denaturation at 98°C for 10 sec, annealing at 65°C for 30 sec, and extension at 72°C for 30 sec. Select the library size and purify with AMPure XP Beads. Use Qubit for library quantification and a high-sensitivity DNA chip to test the library insert size. Sequence the libraries on an Illumina NovaSeq 6000 platform to generate 150 bp paired-end reads.