PU.1 represses and activates gene expression in early T cells by redirection of transcription factor ensembles [ChIP-Seq]

Transcription factors normally regulate gene expression through their action at sites where they bind to DNA. However, the balance of activating and repressive functions that a transcription factor can mediate is not completely understood. Here, we show that PU.1 regulates gene expression in early stages of T-cell development both by recruiting partner transcription factors to its own binding sites and by depleting them from the binding sites that they may prefer when PU.1 is absent. Importantly, the loss of partner factors Satb1 and Runx1 occurs primarily from sites where PU.1 itself does not establish any detectable local binding. Genes linked to sites of partner factor ‘theft’ are enriched for considerable subsets of the genes PU.1 represses both in a model cell-line system and in normal T-cell development. Thus, system-level competitive recruitment dynamics permit PU.1 to affect gene expression both through own target sites and through action at a distance. anti-Runx1 ChIP-seq on Lin- bone marrow DN1 or DN3 cells.