Population cells were sorted by FACS and RNA was isolated using Trizol reagent. Single cells were sorted by FACS and single cells were isolated using C1 Single-Cell Auto Prep System by Fluidigm. Chromatin immunoprecipitation followed published methods (Lee et al 2006) with the exception of FOS dual crosslink with Formaldehyde and DSG. Briefly, cells were fixed 11% formaldehyde at room temperature on a rotating platform for 10min. Formaldehyde was quenched by adding of 125nM of glicyne. Chromatin was sheared and immunoprecipitated with the antobody of interest.A control sample consisting of sonicated chromatin thta has not been immunoprecipitated was also sequenced. For ChIP-seq, libraries were prepared using either KAPA Hyper Prep kit or NEBNext ChIP-seq Library Prep Master Mix for Illumina according to the manufacturer's guidelines. Libraries were size-selected on a 2% agarose gel for a 200-400bp fragments.