The ChIP assay was performed using the EZ-Magna ChIPTM A (Upstate-Millipore, Billerica, MA, USA). Cells were cross-linked in 1% formaldehyde (Sigma-Aldrich, St Louis, MO, USA) for 30 minutes. Nuclear lysates were extracted and the chromatin fraction was sheared to 200- to 500-bp fragments using an ultrasonic probe (Labsonic M, Sartorius, Tagelswangen, Switzerland). Immunoprecipitations were performed using 1 μg of anti-MYCN antibody (Abcam, Cambridge, UK) or 1 μg of anti-mouse IgG1κ antibody (Abcam) as control overnight at 4°C. After washed off unspecific DNA binding, the protein/DNA complexes were eluted and reverse corsslinked to free DNA fragments as described in manual. Purified fragmented DNA was subjected to ChIP-seq analysis for determining MYCN binding regions. Then DNA fragments 150–400 bp long were gel purified following the adaptor ligation step. The PCR-amplified DNA libraries were quantified on an Agilent 2100 Bioanalyzer (Agilent Technologies, Palo Alto, CA, USA) and diluted for cluster generation. The ChIP-seq libraries assayed by single-end sequencing on an Illumina HiSeq platform sequencing in Beijing Genomics Institute (BGI).