Project description:In Drosophila melanogaster, Hox genes are organized in an anterior and a posterior cluster, called Antennapedia complex and bithorax complex, located on the same chromosome arm and separated by 10 Mb of DNA. Both clusters are repressed by Polycomb group (PcG) proteins. Here, we show that genes of the two Hox complexes can interact within PcG bodies in the cell nucleus in tissues where they are corepressed. This colocalization increases during development and depends on PcG proteins. Hox gene contacts are part of a large gene interaction network that includes other PcG target genes. Moreover, they are conserved in the distantly related Drosophila virilis species, and mutations on one of the loci weaken silencing of genes in the other locus, resulting in the exacerbation of homeotic phenotypes in a sensitized genetic background. Thus, the three-dimensional organization of Polycomb target genes in the cell nucleus is an evolutionarily conserved phenomenon that stabilizes the maintenance of epigenetic gene silencing. Chromosome Conformation Capture on Chip (4C) was used to establish chromosomal interactions involving the Fab7 polycomb response element from the bithorax complex of Drosophila melanogaster. Larval brain and anterior discs from 3rd instar larvae were dissected to produce 2 replicate experiments with wild-type (WT-r1, WT-r2) and Fab-712 (F12-r1, F12-r2) fly lines. The 3C was performed as previously described (Hagege et al., 2007; Miele and Dekker, 2009) with the main differences being the use of DpnII (New England Biolabs), a 4 bp cutter restriction enzyme, and a fixation in 3% para-formaldehyde for 30 min, maximizing sensitivity and resolution of contact detection. The 4C DNA and DpnII digested genomic DNA (Control) samples were hybridized using a tiling array mapping the whole chromosome 3R which includes the antenapedia and bithorax hox clusters.
Project description:Chromosome conformation capture (4C-Seq) in Drosophila Twist-H2B embryos (carrying nuclear tag specifically in the mesoderm) during embryogenesis was performed, anchoring on 107 different viewpoints. Two timepoints (3-4hrs and 6-8hrs after egg laying) and two tissue context (whole embryo and mesoderm) were assayed. Two independent collections were performed at each timepoint.
Project description:Chromosome conformation capture (4C-Seq) in Drosophila embryos from a wild-type line and from transgenic fly lines carrying the E3 enhancer of twist at ectopic locations. Two time points (2-5 hrs and 5-8 hrs after egg lay) and two viewpoints located near the twist promoter were assayed. Two independent collections were performed at each timepoint and each viewpoint.
Project description:Polycomb group (PcG) proteins bind and regulate hundreds of genes. Previous evidence has suggested that long-range chromatin interactions may contribute to the regulation of PcG target genes. Here, we adapted the Chromosome Conformation Capture on Chip (4C) assay to systematically map chromosomal interactions in Drosophila melanogaster larval brain tissue. Our results demonstrate that PcG target genes interact extensively with each other in nuclear space. These interactions are highly specific for PcG target genes, because non-target genes with either low or high expression show distinct interactions. Notably, interactions are mostly limited to genes on the same chromosome arm, and we demonstrate that a topological rather than a sequence-based mechanism is responsible for this constraint. Our results demonstrate that many interactions among PcG target genes exist, and that these interactions are guided by overall chromosome architecture. We applied Chromosome Conformation Capture on Chip (4C) to map long-range chromatin interactions among PcDs on a genome-wide scale. Moreover, we implemented a modification of the 4C protocol in which the 4C PCR products are further amplified in a linear fashion using a T7 RNA amplification procedure. Finally, we fluorescently labeled the amplified products with dye and hybridized them to a specially designed microarray, which covers approximately 92% of the non-repetitive fly genome. In this way, we could identify all fragments that are in close contact with a chosen locus with limited material from a single fly tissue (i.e. larval brain).
Project description:To determine whether a TP63/KLF5-regulated super-enhancer region can impact SREBF1 transcription, circularized chromosome conformation capture (4C) assays were performed. 4C assays identified complex, extensive interactions between the SREBF1 promoter and the super-enhancer region Moreover, these DNA-DNA contacts were strictly confined within the super-enhancer region, highlighting the specificity of chromatin interactions
