Genome access is transcription factor specific and defined by nucleosome position [ChIP-Seq]

Mammalian gene expression is controlled by transcription factors (TFs) that engage sequence motifs in a chromatinized genome, where nucleosomes can restrict DNA access. Yet, how nucleosomes affect individual TFs remains unclear. Here, we measure the ability of over one hundred TF motifs to recruit TFs in a defined chromosomal locus in mouse embryonic stem cells. This identifies a set sufficient to enable binding of TFs with diverse tissue specificities, functions, and DNA binding domains. These chromatin-competent factors are further classified when challenged to engage motifs within a highly-phased nucleosome. The pluripotency factors OCT4- SOX2 preferentially engage non-nucleosomal and entry-exit motifs, but not nucleosome internal sites, a preference that also guides binding genome-wide. By contrast, factors such as BANP, REST, or CTCF, engage throughout causing nucleosomal displacement.This reveals that TFs vary widely in their sensitivity to nucleosomes and that genome access is TF-specific and influenced by nucleosome position in the cell. Overall design: Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) of the transcriptionf factor OCT4 in WT and SNF2H KO mouse embryonic stem cells.