Project description:3D-topology of DNA in the cell nucleus provides a level of transcription regulation beyond the sequence of the linear DNA. To study the relationship between transcriptional activity and spatial environment of a gene, we have used allele-specific 4C-technology to produce high-resolution topology maps of the active and inactive X-chromosomes in female cells. We found that loci on the active X form multiple long-range interactions, with spatial segregation of active and inactive chromatin. On the inactive X, silenced loci lack preferred interactions, suggesting a unique random organization inside the inactive territory. However, escapees, among which is Xist, are engaged in long-range contacts with each other, enabling identification of novel escapees. Deletion of Xist results in partial re-folding of the inactive X into a conformation resembling the active X, without affecting gene silencing or DNA methylation. Our data point to a role for Xist RNA in shaping the conformation of the inactive X-chromosome independently of transcription. Five or six 4C viewpoints were applied on the mouse female wild type active X-chromosome, the wild type inactive X-chromosome, the conditional Xist X-chromosome and the Xist knock out X-chromosome
Project description:3D-topology of DNA in the cell nucleus provides a level of transcription regulation beyond the sequence of the linear DNA. To study the relationship between transcriptional activity and spatial environment of a gene, we have used allele-specific 4C-technology to produce high-resolution topology maps of the active and inactive X-chromosomes in female cells. We found that loci on the active X form multiple long-range interactions, with spatial segregation of active and inactive chromatin. On the inactive X, silenced loci lack preferred interactions, suggesting a unique random organization inside the inactive territory. However, escapees, among which is Xist, are engaged in long-range contacts with each other, enabling identification of novel escapees. Deletion of Xist results in partial re-folding of the inactive X into a conformation resembling the active X, without affecting gene silencing or DNA methylation. Our data point to a role for Xist RNA in shaping the conformation of the inactive X-chromosome independently of transcription.
Project description:Recent epigenomic studies have predicted thousands of potential enhancers in the human genome. However, there has not been systematic characterization of target promoters for these potential enhancers. Using H3K4me2 as a mark for active enhancers, we identified genome-wide enhancer-promoter interactions in human CD4+ T cells. Among the 6,520 long-distance chromatin interactions, we identify 2,067 enhancers that interact with 1,619 promoters and enhance their expression. These enhancers exist in accessible chromatin regions and are associated with various histone modifications and Pol II binding. The promoters with interacting enhancers are expressed at higher levels than those without interacting enhancers and their expression levels are positively correlated with the number of interacting enhancers. Interestingly, interacting promoters are co-expressed in a tissue-specific manner. We also find that chromosomes are organized into multiple levels of interacting domains. Our results define a global view of enhancer-promoter interactions and provide a dataset to further understand mechanisms of enhancer targeting and long-range chromatin organization. Two biological replicates of ChIA-PET (Chromatin Interaction Analysis by Paired-End Tag Sequencing) experiment in CD4+ T cells
Project description:ChIP-seq was performed using Drosophila Kc167 cells using antibodies against H3K4me3 to identify active promoters and H3K4me1 to identify active enhancers. H3K27ac ChIPseq was performed to identify active promoters and enhancers. Once enhancers and promoters were identified, JIL-1 and histone phosphorylation, H3K9acS10ph and H3K27acS28ph, ChIP-seq was performed to look at binding trends. JIL-1 and phosphoacetlation is found at low levels at inactive enhancers and shows increase at active enhancers and promoters. Here we examine histone phosphorylation by JIL-1 and acetylation of H3K27ac by CBP at transcriptionally active vs. inactive promoters and enhancers. ChIP-seq is performed in Kc167 Drosophila cells using antibodies against JIL-1, H3K27acS28ph, H3K9acS10ph, H3K4me3, H3K4me1, and H3K27ac.
Project description:The spatial organization of DNA in the cell nucleus is an emerging key contributor to genomic function. We have developed 4C technology, or 3C-on-chip, which allows for an unbiased genome-wide search for DNA loci that contact a given locus in the nuclear space. We demonstrate here that active and inactive genes are engaged in many long-range intrachromosomal interactions and can also form interchromosomal contacts. The active b-globin locus in fetal liver contacts mostly transcribed, but not necessarily tissue-specific, loci elsewhere on chromosome 7, while the inactive locus in fetal brain contacts different, transcriptionally silent, loci. A housekeeping gene in a gene dense region on chromosome 8 forms long-range contacts predominantly with other active gene clusters, both in cis and in trans, and many of these intra- and interchromosomal interactions are conserved between the tissues analyzed. Our data demonstrate that chromosomes fold into areas of active chromatin and areas of inactive chromatin and establish 4C technology as a powerful tool to study nuclear architecture. Keywords: 4C technology
Project description:EVI1 expression is associated with poor prognosis in myeloid leukaemia. Aberrant expression can result from Chr.3q alterations, which cause juxtaposition of enhancers that induce EVI1 activation via long-range chromatin interactions. More often, however, EVI1 expression occurs unrelated to 3q alterations, and it is unclear if its expression underlies similar dependencies as 3q+ cells. As enhancers regulate promoters by physical interaction/chromatin looping, we explored if the EVI1 promoter in EVI1+3q- cells interacts with distally located chromatin and if these intereactions promote EVI1 expression. To monitor TF binding sites at interactions involving active chromatin, we performed ATAC-Seq.