Treated cells in culture were cross-linked with 1% formaldehyde for 10 minutes and then queched with glycine. Washed cells were lysed and sonicated, followed by antibody immunoprecipitation. DNA libraries for ChIP-seq were prepared using Ovation Ultralow DR Multiplex System kits (0330-32, NuGEN) followed by Illumina sequencing at the MIT BioMicro Center.