P19 embryonal carcinoma cells were cultured in DMEM with 10% fetal calf serum. The mouse P19ECs were obtained from ATCC and were cultured in DMEM, 10% fetal 655 calf serum, 2mM L-glutamine (Gibco) and 50 ug/ml penicillin/streptomycin (Gibco) P19ECs were stably transfected with AP2gamma. Cells were harvested and crosslinked with 1% formaldehyde. Phenol Chloroform extraction Performed ChIP according to: Magnusdottir, E. et al. Epidermal terminal differentiation depends on B lymphocyte912 induced maturation protein-1. Proceedings of the National Academy of Sciences of the United States of America 104, 14988-93 (2007). Libraries were generated using Nugene Ovation Ultralow Library Kit.