Notch interaction with RUNX factors regulates initiation of the T-lineage program [ChIP-seq]

RUNX factors play an essential role in the development of T cell. Dynamic interacting partner switching of RUNX1 induces the redeployment of RUNX1 at the T-lineage commitment checkpoint. Here, we attempted to reveal functional differences in RUNX factors between lymphoid progenitor (LP) and Noth-stimulated the earliest T progenitor stage, phase1. We identified CTCF as a LP-specific RUNX1-interacting partner. Indeed, LP-specific RUNX1 binding genomic sites had significantly enriched CTCF consensus motif and co-occupied with CTCF. After Notch stimulation, Notch1-IC directly interacted with RUNX1 and recruited it to the Notch-regulated T-signature gene loci with the Mediator/p300 transcriptional activation complex. CRISPR/Cas9-mediated stage-specific deletion of RUNX factors and its binding partners revealed that the RUNX1/CTCF complex in LP and the RUNX1/Mediator/p300 complex in phase1 negatively and positively regulate T-signature genes expression, respectively. Our results indicate that the Notch-mediated functional conversion of RUNX factors; re-organization of protein complexes and redeployment of genomic binding sites, has a crucial role in the initiation of T-lineage program.