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Defining the molecular mechanisms underlying immunological memory in T cells (DNase-Hypersensitivity)

ABSTRACT: Immunological memory is a defining feature of animal development, allowing rapid responses to repeat infections, yet the very basis of T cell-dependent memory remains poorly understood. Here we demonstrate that the critical steps in the acquisition of T cell memory occur not after completion of T cell differentiation but during the initial activation phase of naïve T cells, when extensive chromatin remodelling reprograms immune response genes towards a stably maintained primed state. During this process, inducible factors including AP-1 create hundreds of DNase I hypersensitive sites (DHSs), allowing the recruitment of ETS1 and RUNX1 to sites that were previously inaccessible. Significantly, these DHSs remain temporally and mitotically stable long after cessation of AP-1 activation, and function to maintain regions of active chromatin in the vicinity of genes that regulate immune responses. This priming enables increased accessibility and the accelerated induction of other inducible regulatory elements in previously activated T cells.

ORGANISM(S): Mus musculus

PROVIDER: GSE67451 | GEO | 2016/02/02

SECONDARY ACCESSION(S): PRJNA279990

REPOSITORIES: GEO

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Project description:Nucleosome positioning dictates the DNA accessibility for regulatory proteins, and thus is critical for gene expression and regulation. It has been well documented that only a subset of nucleosomes are reproducibly positioned (phased) in eukaryotic genomes. The most prominent example of phased nucleosomes is the context of genes, where phased nucleosomes flank the transcriptional starts sites (TSSs). It is unclear, however, what factors influence nucleosome phasing in regions that are not close to genes. We performed a combinational mapping of nucleosome positioning and DNase I hypersensitive sites (DHSs) across the rice genome. We discovered that DHSs located in a variety of contexts, both genic and intergenic, were flanked by strongly phased nucleosome arrays. Our results support the barrier model for nucleosome organization as a general feature of eukaryote genomes, including plant genomes, and not limited to TSSs. Specifically, regions bound with regulatory proteins, including intergenic regions, can serve as barriers that organize phased nucleosome arrays on both sides. Our results also suggest that rice DHSs often span a single, phased nucleosome, similar to the H2A.Z-containing nucleosomes observed in DHSs in the human genome. We propose that genome-wide nucleosome positioning in the eukaryotic genomes is orchestrated by genomic regions associated with regulatory proteins. Rice chromatin was digested by micrococcal nuclease (MNase) into mono-nucleosome size. Mono-nucleosomal DNA was isolated and sequenced (MNase-seq) using Illumina sequencing platforms. We obtained a total of 38 million (M) single-end reads from our first MNase-seq experiment and mapped ~26 M to unique positions in the rice genome. We also conducted pair-end sequencing of an independent MNase-seq library, obtained 274 M paired-end reads, and mapped ~231 M read pairs to unique positions in the rice genome.We applied a strategy of combinational mapping of nucleosome positioning and DHSs (GSE26610) to examine whether nucleosome positioning is associated with all cis-regulatory elements in the rice genome. All datasets used in the analysis were developed using rice leaf tissue in the same developmental stage

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Defining the molecular mechanisms underlying immunological memory in T cells (DNase-Hypersensitivity)

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