Unknown,Transcriptomics,Genomics,Proteomics

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Comparison of nucleosome occupancy and chromatin states between normal and cancer cell lines

ABSTRACT: Background: Epigenetic modification is a hallmark of cancer cells achieved through altered patterns of DNA methylation, histone modifications and nucleosome positions. These events have only been described in detail at gene promoters. Results: Here, we integrate multiple epigenome-wide maps to evaluate the scope of global epigenetic reprogramming in cancer cells at enhancers and insulators. Using high-resolution simultaneous mapping of global DNA methylation and nucleosome positions within individual DNA strands (NOMe-Seq), we observe a reorganization of the DNA methylome coupled with simultaneous modulation of nucleosome depleted regions (NDRs) at distal regulatory elements in cancer cells. We show that while NDRs are preferentially found at enhancers in normal breast and prostate epithelial cells, there are fewer NDRs coupled with increased DNA methylation detected at enhancersin cancer cells. Our data suggests that the acquisition of a nucleosome is key to DNA hypermethylation susceptibility and contributes to epigenetic silencing of enhancers in cancer, which can notably occur without loss of H3K4me1. Further we observe that NDRs are not necessary for peripheral phasing of adjacent nucleosomes, contrary to the common dogma, and show that nucleosomes remain organized and phased, even in the absence of a NDR as an anchor. Finally we observe the potential for transcription factors (TF) to organize NDRs genome-wide; all TF-binding sites are strongly hypomethylated and some show extensive peripheral nucleosome phasing. Conclusion: Together our findings suggest that, in addition to epigenetic alterations to promoter regions in cancer, there is substantial disruption to the distal regulatory architecture that provides an additional layer of epigenetic plasticity in malignancy. NOMe-seq, ChIP-seq for 5 marks and input control for breast normal (HMEC), breast cancer (MCF7), prostate normal (PrEC) and prostate cancer (PC3) cell lines

ORGANISM(S): Homo sapiens

SUBMITTER: Aaron Statham

PROVIDER: E-GEOD-57498 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Despite depression being one of the most prevalent and debilitating disorders worldwide, it has been difficult to understand its pathophysiology and to develop more effective treatments. Maladaptive transcriptional regulation within limbic neural circuits, including reward processing regions such as the nucleus accumbens (NAc), in response to chronic stress is thought to be a major contributor to the development of the syndrome. Epigenetic events?in particular, histone writers and erasers?that alter chromatin structure to regulate programs of gene expression have increasingly been associated with depression-related behavioral abnormalities in animal models and in depressed humans examined postmortem. However, very little is known about the ATP-dependent chromatin remodelers that control nucleosome positioning and the packing state of chromatin. Here we show that the ACF complex, part of the ISWI family of chromatin remodelers, is persistently and selectively upregulated in the NAc of mice that are susceptible to chronic social stress, as well as in the NAc of depressed human. We further establish that ACF induction is both necessary and sufficient for susceptibility to stress-induced depressive-like behaviors. Using ChIP-seq, we demonstrate that altered ACF binding after chronic stress is strongly correlated with altered nucleosome positioning, in particular, around the transcriptional start sites of affected genes. These alterations in ACF binding and nucleosome repositioning are associated with repressed expression of a subset of genes in animals that are susceptible to chronic stress. Together, these findings establish that active ATP-dependent chromatin remodeling by the ACF complex is a key regulator in the repression of genes that mediate susceptibility to social stress, and provide novel candidate targets for improved therapeutics of depression and other stress-related disorders. c57bl/6 mice underwent chronic social defeat stress (CSDS), and social interaction test was used to separate animals into control, susceptible and resilient groups. Nucleus accumbens (NAc) tissue was collected 48 hours after the last defeat session, and then Acf1, SNF2H ChIP-seq or H3 MNase-seq were performed based on the control, susceptible, and resilient groups. Three sequencing replicates were performed on each group.

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Comparison of nucleosome occupancy and chromatin states between normal and cancer cell lines

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