For calibrated ChIP-seq 2 million human HEK293T cells were mixed with 50 million B3 cells prior to fixation. Cells were fixed at room temperature in 10ml PBS with 1mM DSG (ThermoFisher 20593) for 30 min followed by addition of 1% formaldehyde (ThermoFisher 28908) and incubated for a further 10min. The reaction was quenched with 125mM glycine. Chromatin was digested by sonication or MNase to obtain fragments between 100-300bp. A small aliquot was reserved for the Input sample, and chromatin equivalent to 4 million cells was used per IP. HA-Ikaros-ERt2 ChIP performed using overnight incubation with Pierce magnetic anti-HA beads (Pierce 88836). For H3K27ac (Active Motif 39133) and CHD4 (Abcam ab70469), 4-6 mg of antibodies were incubated with each reaction overnight, followed by 2h of incubating with magnetic Prot A/G Dynabeads (ThermoFisher 10001D, 10003D). Washes were performed for 5 min rotating in the cold room twice with each buffer, Low Salt Buffer, High Salt Buffer, LiCl Buffer and TE. DNA was eluted with 1% SDS and 0.1M NaHCO3. For reverse crosslink, NaCl was added to a final concentration of 0.2M, and samples were incubated at 65°C shaking overnight, following by 2h of RNaseA and 2h of Proteinase K treatment. NEBNext® Ultra™ II DNA Library Prep Kit for Illumina® (E7645S) was used for all ChIP-seq libraries with PCR amplification of 5-8 cycles. Clean-up was performed with Ampure beads and quantification and quality control of libraries was performed using DNA Qubit and HS DNA Bioanalyser.