PRJNA255939
Homo sapiens
The rearrangement of nucleosomes along the DNA fiber profoundly affects gene expression, but little is known about how signaling reshapes the chromatin landscape, in 3D space and over time, to allow establishment of new transcriptional programs. Using micrococcal nuclease treatment and high-throughput sequencing, we map genome-wide changes in nucleosome positioning in primary human endothelial cells stimulated with tumour necrosis factor a (TNFa)—a cytokine that signals through nuclear factor ?B (NF-?B). Within 10 min, nucleosomes reposition at regions both proximal and distal to NF-?B binding sites, before the transcription factor quantitatively binds thereon. Similarly, in long TNFa-responsive genes repositioning precedes transcription by pioneering elongating polymerases and appears to nucleate from intragenic enhancer clusters. By 30 min, widespread repositioning throughout Mbp-long chromosomal segments, with consequential effects on 3D structure (detected using chromosome conformation capture). Whilst nucleosome repositioning is viewed as a local phenomenon, our results point to effects occurring over multiple scales. We present data in support of TNFa-induced priming, mostly independent of NF-?B binding and/or elongating RNA polymerases, leading to a plastic network of interactions that affects DNA accessibility over large domains.