library_construction_protocol: CTCF site 1 was purified using a GigaPrep kit (Qiagen), restriction enzyme digested, and purified by size exclusion chromatography. Chromatin was assembled using salt gradient dialysis Library preparation included DNA damage repair, end repair, blunt-end SMRTbell® ligation, Exonuclease treatment, and Ampure PB cleanup according to manufacturer's instruction. Library quality was assessed with Agilent Bioanalyzer High Sensitivity DNA kit or Agilent Tapestation D5000 Assay. PacBio SMRTbell® library preparation