Unknown,Transcriptomics,Genomics,Proteomics

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Genome-wide maps of chromatin state in HSC, Pro B and mature B cells

ABSTRACT: We have used a genome-wide ChIP-sequencing approach to define and investigate the dynamics of the cis-regulatory landscape in three developmental stages of the murine hematopoietic system. To this end, we have compared the profiles of H3K4me3, H3K4me1, H3K27ac, H3K27me3 and H3K9me2 in HSCs, committed pro-B and splenic mature B cells. We find the enhancer repertoire to be dynamically reshaped during hematopoiesis progression, surprisingly only a small fraction of primed enhancers in HSCs or committed progenitors become activated in subsequent stages. In turn, the majority of active enhancers in terminally differentiated cells are not primed in earlier stages. We also found that The heterochromatin mark H3K9me2 covers large domains that remain largerly invariant across the three stages and are depleted in both active chromatin marks and the Polycomb related mark H3K27me3. Investigating enhancer dynamics in 3 different stages of B cell development

ORGANISM(S): Mus musculus

SUBMITTER: Mohamed-Amin choukrallah

PROVIDER: E-GEOD-60005 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Missense mutations in the TP53 gene are frequent genetic alterations in human tumor tissue and cell lines. In contrast to wild-type p53, the mutant p53 (mutp53) protein has lost the transcriptional activity towards pro-apoptotic and growth arrest genes, but retained the property to interact with DNA in a structure-specific fashion. Expression of mutp53 is advantageous for tumor cells, however the molecular mechanism of mutp53 action is still not known. We used the glioblastoma-derived U-251 MG human cell line to analyze DNA binding of mutant p53 (R273H mutation) on a Nimblegen custom 135k tiling array and to correlate mutp53 binding regions with the epigenetic state and occupation by other transcription factors (ETS1 and SP1). We found that mutp53-binding regions are G/C-rich and are located around transcriptional start sites (TSS) of many protein-coding genes, which in most cases are active, but are not always regulated upon transient mutp53 depletion. We propose a model which does not only rely on interactions of mutp53 with diverse transcriptional regulators at active promoters, but primarily is based on a DNA binding activity of mutp53. We designed a Nimblegen custom 135k tiling array that covers a large set of putative and known p53 (wild-type and mutant) target genes in the human genome. For analysis of the epigenetic state of genes covered by the tiling array in control and mutant p53-depleted U251 cells we focused on changes in active histone marks, H3K4me3 and H3K9Ac, and RNA polymerase II recruitment and processivity. H3K4me3 and H3K9Ac marks are enriched in active promoter regions and the phosphorylation of serine 5 (S5-P) and serine 2 (S2-P) in the CTD of RNA polymerase II have been described to define initiated and elongating complexes, respectively. We performed the ChIP-chip experiments for H3K4me3, H3K9Ac, RNA polymerase II (S5-P) and RNA polymerase II (S2-P) from U251 cells transfected with p53-specific siRNA or control siRNA (2 biological replicates each). To analyze binding of mutant p53 to the genes covered by the tiling array we performed mutant p53 ChIP-chip experiments in 4 biological replicates of. In addition, we analyzed the distribution of SP1 and ETS1 binding sites in 3 biological replicates.

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Genome-wide maps of chromatin state in HSC, Pro B and mature B cells

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