Project description:Understanding the impact of cohesin mutations on HSPC chromatin structure We examined chromatin structure using ATAC-seq in CD34+ enriched-human HSPC that were transduced with either cohesin WT, mutant or empty vector controls
Project description:Transciptome analysis of CD34+ enriched human HSPC lentivirally transduced with cohesin WT or mutant CD34+ enriched HSPCs from cord blood were transduced with a constitutive lentiviral vector expressing cohesin WT or mutant tagged to GFP. After 72hrs cells were GFP+ sorted and subjected to downstream microarray protocol.
Project description:Cohesin complex members have recently been identified as putative tumor suppressors in hematologic and epithelial malignancies. The cohesin complex guides chromosome segregation, however cohesin-mutant leukemias do not show genomic instability. We hypothesized reduced cohesin function alters chromatin structure and disrupts cis-regulatory architecture of hematopoietic progenitors. We investigated the consequences of Smc3 deletion in normal and malignant hematopoiesis. Bi-allelic Smc3 loss induced bone marrow aplasia with premature sister chromatid separation, and revealed an absolute requirement for cohesin in hematopoietic stem cell function. In contrast, Smc3 haploinsufficiency increased self-renewal in vitro and in vivo including competitive transplantation. Smc3 haploinsufficiency reduced coordinated transcriptional output, including reduced expression of transcription factors and other genes associated with lineage commitment. Smc3 haploinsufficiency cooperated with Flt3-ITD to induce acute leukemia in vivo, with potentiated Stat5 signaling and altered nucleolar topology. These data establish a dose-dependency for cohesin in regulating chromatin structure and hematopoietic stem cell function. ATAC-seq in murine c-kit+ cells for the following genotypes: Smc3 fl/+, Smc3 del/+, Flt3-ITD, Smc3 fl/del Flt3-ITD
Project description:The functions of cohesin are central to genome integrity, chromosome organization, and transcription regulation through its prevention of premature sister-chromatid separation and the formation of DNA loops. The loading of cohesin onto chromatin depends on the Scc2-Scc4 complex, however, little is known about how it stimulates the cohesin loading activity. Here we determine the large “hook” structure of Scc2 responsible for catalyzing cohesin loading. We identify key Scc2 surfaces that are crucial for DNA binding and for cohesin loading in vivo. Using previously determined structures and modeling, we derive a pseudo-atomic structure of the full-length Scc2-Scc4 complex. Finally, our crosslinking and electron microscopy analyses reveal that Scc2-Scc4 utilizes its modular structure to make multiple contacts with a folded cohesin at an interface created by the cohesin head-hinge interaction.
Project description:Mammalian circadian rhythm is established by the negative feedback loops consisting of a set of clock genes, which lead to the circadian expression of thousands of downstream genes. As genome-wide transcription is organized under the high-order chromosome structure, it is unclear how circadian gene expression is influenced by chromosome structure. In this study, we focus on the function of chromatin structure proteins cohesin as well as CTCF (CCCTC-binding factor) in circadian rhythm. We analyzed the interactome of a Bmal1-bound enhancer upstream of a clock gene, Nr1d1, by 4C-seq and observed that cohesin binding sites are enriched in the interactome. Integrating circadian transcriptome data and cistrome data, we found that cohesin-CTCF co-binding sites tend to insulate the phases of circadian oscillating genes while cohesin-non-CTCF sites facilitate the interaction between circadian enhancer and promoter. A coarse-grained model integrating the long-range effect of cohesin and CTCF markedly improved our mechanistic understanding of circadian gene expression. This model is subsequently supported by our RNA-seq data from cohesin knockout cells. Cohesin is required at least in part for driving the circadian gene expression by facilitating the enhancer-promoter looping. Taken together, our study provided a novel insight into the relationship between circadian transcriptome and the high-order chromosome structure. 4C-seq of a Bmal1 enhancer in mouse liver
Project description:Mammalian circadian rhythm is established by the negative feedback loops consisting of a set of clock genes, which lead to the circadian expression of thousands of downstream genes. As genome-wide transcription is organized under the high-order chromosome structure, it is unclear how circadian gene expression is influenced by chromosome structure. In this study, we focus on the function of chromatin structure proteins cohesin as well as CTCF (CCCTC-binding factor) in circadian rhythm. We analyzed the interactome of a Bmal1-bound enhancer upstream of a clock gene, Nr1d1, by 4C-seq and observed that cohesin binding sites are enriched in the interactome. Integrating circadian transcriptome data and cistrome data, we found that cohesin-CTCF co-binding sites tend to insulate the phases of circadian oscillating genes while cohesin-non-CTCF sites facilitate the interaction between circadian enhancer and promoter. A coarse-grained model integrating the long-range effect of cohesin and CTCF markedly improved our mechanistic understanding of circadian gene expression. This model is subsequently supported by our RNA-seq data from cohesin knockout cells. Cohesin is required at least in part for driving the circadian gene expression by facilitating the enhancer-promoter looping. Taken together, our study provided a novel insight into the relationship between circadian transcriptome and the high-order chromosome structure. RNA-Seq in WT and Smc3-/- mouse embryonic fibroblast cells
Project description:Mammalian circadian rhythm is established by the negative feedback loops consisting of a set of clock genes, which lead to the circadian expression of thousands of downstream genes. As genome-wide transcription is organized under the high-order chromosome structure, it is unclear how circadian gene expression is influenced by chromosome structure. In this study, we focus on the function of chromatin structure proteins cohesin as well as CTCF (CCCTC-binding factor) in circadian rhythm. We analyzed the interactome of a Bmal1-bound enhancer upstream of a clock gene, Nr1d1, by 4C-seq and observed that cohesin binding sites are enriched in the interactome. Integrating circadian transcriptome data and cistrome data, we found that cohesin-CTCF co-binding sites tend to insulate the phases of circadian oscillating genes while cohesin-non-CTCF sites facilitate the interaction between circadian enhancer and promoter. A coarse-grained model integrating the long-range effect of cohesin and CTCF markedly improved our mechanistic understanding of circadian gene expression. This model is subsequently supported by our RNA-seq data from cohesin knockout cells. Cohesin is required at least in part for driving the circadian gene expression by facilitating the enhancer-promoter looping. Taken together, our study provided a novel insight into the relationship between circadian transcriptome and the high-order chromosome structure. Bmal1 ChIP-Seq in WT mouse embryonic fibroblast cells
Project description:Cohesin complex members have recently been identified as putative tumor suppressors in hematologic and epithelial malignancies. The cohesin complex guides chromosome segregation, however cohesin-mutant leukemias do not show genomic instability. We hypothesized reduced cohesin function alters chromatin structure and disrupts cis-regulatory architecture of hematopoietic progenitors. We investigated the consequences of Smc3 deletion in normal and malignant hematopoiesis. Bi-allelic Smc3 loss induced bone marrow aplasia with premature sister chromatid separation, and revealed an absolute requirement for cohesin in hematopoietic stem cell function. In contrast, Smc3 haploinsufficiency increased self-renewal in vitro and in vivo including competitive transplantation. Smc3 haploinsufficiency reduced coordinated transcriptional output, including reduced expression of transcription factors and other genes associated with lineage commitment. Smc3 haploinsufficiency cooperated with Flt3-ITD to induce acute leukemia in vivo, with potentiated Stat5 signaling and altered nucleolar topology. These data establish a dose-dependency for cohesin in regulating chromatin structure and hematopoietic stem cell function.
Project description:Although cohesin and CTCF are major determinants of interphase 3D genome organisation, their impact on the maintenance of transcriptional control, chromatin marks, and enhancer states appears surprisingly limited. Here we study how cohesin promotes the dynamics of eRNA transcription and enhancer states and facilitates the regulation of inducible inflammatory genes in macrophages.