For crosslinked MNase ChIP, cells were crosslinked (1% formaldehyde, 10mins) and digested with microccocal nuclease, nuclei were then isolated and flash frozen. For native ChIP, flash frozen cell pellets were lysed with hypotonic buffer and digested with micrococcal nuclease. Protein:DNA complexes were immunoprecipitated with specific antibodies pre-bound to protein A/G or goat anti-mouse IgG magnetic beads. Eluted DNA underwent crosslink reversal, if necessary, were RNAse treated followed by phenol:choloroform cleanup. Cells harvested and flash frozen using liquid nitrogen. RNA was then extracted using Sigma GenElute Mammalian Total RNA Extraction Kit RNA-seq libraries were prepared from mRNA as described in Morin et al from 10ug of DnaseI treated total RNA (Morin R, Bainbridge M, Fejes A, Hirst M, Krzywinski M, Pugh T, McDonald H, Varhol R, Jones S, Marra M: Profiling the HeLa S3 transcriptome using randomly primed cDNA and massively parallel short-read sequencing. BioTechniques 2008, 45:81-94.) Adaptor ligation based library construction for paired-end Illumina sequencing