Project description:The impact of signal dependent transcription factors, such as glucocorticoid receptor (GR) and NFκB on the three-dimensional organization of chromatin remains a topic of discussion. The possible scenarios range from remodeling of higher order chromatin architecture by activated transcription factors to recruitment of activated transcription factors to pre-established long-range interactions. Using 4C-seq and high-resolution ChIA-PET analysis of P300 we observed agonist-induced changes in long-range chromatin interactions, and uncovered interconnected enhancer-enhancer hubs spanning up to one megabase. The vast majority of activated GR and NFκB appears to join pre-existing P300 enhancer hubs without affecting the chromatin conformation. In contrast, binding of the activated transcription factors to loci with their consensus response elements leads to increased formation of an active epigenetic state of enhancers and a significant increase in long-range interactions within pre-existing enhancer networks. De novo enhancers or ligand-responsive enhancer hubs preferentially interact with ligand-induced genes. We demonstrate that, at a subset of genomic loci, ligand-mediated induction leads to active enhancer formation and an increase in long-range interactions, facilitating efficient regulation of target genes. Therefore, our data suggest an active role of signal dependent transcription factors in chromatin and long-range interaction remodeling.
