library_construction_protocol: 100,000 cells were spun down at 500 xg for 5min at 4 C. The pellet was washed once with 500 ul of cold 1x PBS and spun down again at 500 xg for 5min at 4 C. Pellet was resuspended in 450 ul of cold hypotonic buffer (10 mM Tris-HCl, pH 7.4, 10 mM NaCl, 3 mM MgCl2) and immediately added 50 ul of 1% IGEPAL CA-630 (0.1% final), inverting to mix. Cells were incubated on ice for 15 min before spinning down at 500 xg for 10 min at 4 C. Pellet was set on ice, and the transposition reaction was performed following the ATAC-seq Kit instructions (Cell Biologics, Cat No. CB6936). Pelleted cells were resuspended in 50 ul of transposition reaction mix (25 ul 2X Reaction Buffer, 2.5ul Transposome, 22.5ul Nuclease free water) and incubated at 37 C for 1 hour. DNA was purified using Qiagen MinElute kit (Qiagen, #28004) and eluted in 15 ul of Elution Buffer, followed by library generation to amplify transposed DNA fragments. 10 ul of transposed DNA, 10 ul of nuclease free water, 2.5 ul of Ad1.noMX (Oligo 1), 2.5 ul Ad2._Barcode (Oligo 2) and 25 ul of High Fidelity 2x PCR Master Mix was run on a thermocycler using the following cycle: 98 C 30 sec, (98 C 10 sec, 63 C 30 sec, 72 C 1 min) x 10 times and held at 4 C.  For double-sided bead purification (to remove primer dimers and large >1,000 bp fragments), each PCR sample was transferred to a 1.5 ml tube and 0.5X volume (25ul) of AMPure XP beads was added, mixed by pipetting 10 times before incubation at room temperature for 10 min. Tubes were placed in a magnetic rack for 5 min, and the supernatant was transferred to a new tube. 1.3X of the original volume (65ul) of AMPure XP beads was added, mixed by pipetting 10x, and incubated at room temperature for 10 min. Tubes were placed in a magnetic rack for 5 min, supernatant was discarded, and beads were washed with 200 ul 80% EtOH. EtOH was removed, and tubes were left on magnetic rack with cap open for 10 min or until the pellet was totally dry. Beads were resuspended in 20 ul of nuclease-free water and mixed thoroughly, and then tubes were placed in the magnetic rack for 5 min before the supernatant was transferred to a new tube.