Cell lysates were sonicated for 30 minutes and PU.1/Spi-B-DNA complexes were isolated with an anti-FLAG antibody. Fragmented DNA was quantified using 2100 Bioanalyzer (Agilent Technologies). Libraries were generated robotically with 10 ng of fragmented DNA (range 100-300 bp) using the Kapa HTP Library Preparation Kit (Kapa Biosystems) as per the manufacturer’s recommendations except that adapters and PCR primers were diluted 100-fold, the size selection step was done after the PCR step and the number of PCR cycles increased by 6. Adapters and PCR primers were purchased from Integrated DNA Technologies) whereas size selection has been performed on a Pippin Prep instrument (SAGE Biosciences Inc). Libraries were quantified using the Quant-iT™ PicoGreen® dsDNA Assay Kit (Life Technologies) and the Kapa Illumina GA with Revised Primers-SYBR Fast Universal kit (D-Mark). Average size fragment was determined using a LaChip GX (PerkinElmer) instrument. Libraries were sequenced on a SR100 run on a HiSeq2000 (Illumina).