library_construction_protocol: Cells were fixed with 2% paraformaldehyde for 10 minutes at room temperature, quenched with 10 ml of cold 0.13 M glycine, and lysed using cell lysis buffer comprising 1M Tris-HCl, NP-40, Triton X-100, 5M NaCl, 0.5M EDTA, and 100X proteinase inhibitor. The mixture was shaken on ice for 15 minutes, then scraped and shaken for another 5 minutes on ice. The nuclei were collected by centrifugation at 500g for 5 minutes at 4oC, resuspended in 1.2X restriction enzyme buffer, and treated with 0.3% SDS and 2.5% Triton X-100, with incubation at 37oC for 1 hour. Then clean up DNA by DNA precipitation. Chromatin was fragmented by subjecting isolated nuclei to primary restriction enzyme digestion overnight with shaking at 750rpm, using the 4-bp cutter restriction enzyme to achieve optimal contact-mapping resolution, followed by in situ ligation in a reaction mix containing ligase buffer and ligase, incubated overnight at 16oC. Post-ligation, cross-links were reversed by overnight incubation with Proteinase K at 65oC. DNA was purified using SPRI beads and subjected to a second 4-bp cutter restriction enzyme digestion. The digested DNA was then ligated again, and the resulting 3C templates were purified using SPRI beads, and quantified using the Qubit dsDNA BR Assay Kit. Next, two rounds of PCR amplification were conducted: an inverse PCR to amplify captured regions, followed by an indexing PCR to generate sequencing-ready libraries.