Unknown,Transcriptomics,Genomics,Proteomics

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TNFalpha signaling primes chromatin for NF-kappaB binding and induces rapid and widespread nucleosome repositioning

ABSTRACT: Background 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 the establishment of new transcriptional programs. Results 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 alpha (TNFalpha) - a proinflammatory cytokine that signals through nuclear factor kappaB (NF-kappaB). Within 10 minutes, nucleosomes reposition at regions both proximal and distal to NF-kappaB binding sites, before the transcription factor quantitatively binds thereon. Similarly, in long TNFalpha-responsive genes, repositioning precedes transcription by pioneering elongating polymerases and appears to nucleate from intragenic enhancer clusters resembling super-enhancers. By 30 minutes, widespread repositioning occurs throughout Mbp-long chromosomal segments, with consequential effects on 3D structure, detected using chromosome conformation capture. Conclusions Whilst nucleosome repositioning is viewed as a local phenomenon, our results point to effects occurring over multiple scales. Here, we present data in support of a TNFalpha-induced priming mechanism, mostly independent of NF-kappaB binding and/or elongating RNA polymerases, leading to a plastic network of interactions that affects DNA accessibility over large domains. MNase-Seq of HUVEC cells after stimulation with TNFÎ± for 0, 10 or 30 min. Biological replicates for 0 and 30 min.

ORGANISM(S): Homo sapiens

SUBMITTER: Sarah Diermeier

PROVIDER: E-GEOD-53343 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Signal transduction by the NF-kappaB pathway is a key regulator of a host of cellular responses to extracellular and intracellular messages. The NEMO adaptor protein lies at the top of this pathway and serves as a molecular conduit, connecting signals transmitted from upstream sensors to the downstream NF-kappaB transcription factor and subsequent gene activation. The position of NEMO within this pathway makes it an attractive target from which to search for new proteins that link NF-kappaB signaling to additional pathways and upstream effectors. In this work, we have used protein microarrays to identify novel NEMO interactors. A total of 112 protein interactors were identified, with the most statistically significant hit being the canonical NEMO interactor IKKbeta, with IKKalpha also being identified. Of the novel interactors, more than 30% were kinases, while at least 25% were involved in signal transduction. Binding of NEMO to several interactors, including CALB1, CDK2, SAG, SENP2 and SYT1, was confirmed using GST pulldown assays and coimmunoprecipitation, validating the initial screening approach. Overexpression of CALB1, CDK2 and SAG was found to stimulate transcriptional activation by NF-kappaB, while SYT1 overexpression repressed TNFalpha-dependent NF-kappaB transcriptional activation in human embryonic kidney cells. Corresponding with this finding, RNA silencing of CDK2, SAG and SENP2 reduced NF-kappaB transcriptional activation, supporting a positive role for these proteins in the NF-kappaB pathway. The identification of a host of new NEMO interactors opens up new research opportunities to improve understanding of this essential cell signaling pathway. For microarray screening, Invitrogen Protoarray v4.0 protein microarrays were used. Human NEMO expressed as a C-terminal GST fusion was purified from E. coli lysates and labelled with biotin. NEMO or biotinylated GST were applied to the microarrays and binding partners detected using streptavidin-Alexa Fluor 647. Significant interactors on both arrays were detected using Invitrogen Protoarray Prospector software and a Z-score cutoff of 3.0. Following subtraction of interactors present on the GST control array, a final set of significant NEMO interactors was derived. Full experimental details are supplied in Fenner, B. J., Scannell, M. & Prehn, J. H. M. (2010). Expanding the substantial interactome of NEMO using protein microarrays. PLoS ONE (in press).

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TNFalpha signaling primes chromatin for NF-kappaB binding and induces rapid and widespread nucleosome repositioning

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