The spatio-temporal program of DNA replication is driven by specific epigenetic signatures in human cells
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ABSTRACT: We report the application of single-molecule-based sequencing technology for high-throughput profiling of DNA replication origins in K562 mammalian cells. We have optimized a specific method of peak detection adapted to the signal produced by the sequencing of short nascent strands (SNS) that are specific of replication initiation, with the aim to have both a good sensitivity and specificity. We demonstrated the existence of the spatiao-temporal program of DNA replication driven by a specific epigenetic signature. K562 human cells; five samples subjected to SNS-Seq.
Project description:Short nascent strands purification coupled to next-generation sequencing allowed us to identify replication origins on human genome in an extensive way, by mapping replication origins in 4 different cell types, IMR-90 fibroblasts, hESC H9 cells, iPSC Th Cl-4 cells and HeLa cells. We demonstrated the existence of a cell type-specific reprogrammable signature of the cell identity revealed by specific efficiencies of conserved origin positions and not by the selection of cell-type specific subsets of origins. 4 different cell types were analyzed. For each cell types, 2 different biological replicates of short nascent strands at replication origins were purified. Each SNS sample was sequencing at least one time.
Project description:At every cell cycle, faithful inheritance of metazoan genomes requires the concerted activation of thousands of DNA replication origins. However, which genetic and chromatin features define metazoan replication start sites remains largely unknown. Here, we delineate the origin repertoire of the Drosophila genome at high resolution. We address the role of origin-proximal G-quadruplexes and show their ability to transiently stall replication forks in vivo. We dissect the chromatin configuration of replication origins and identify a rich spatial organization of chromatin features at initiation sites. DNA shape and chromatin configurations, not strict sequence specificity, mark and predict replication origins in higher eukaryotes. We further examine the link between transcription and origin firing and reveal that modulation of origin activity across cell types is intimately linked to cell-type-specific transcriptional programs. Our study unravels conserved origin features and provides unique insights into the relationship between DNA topology, chromatin, transcription and replication initiation across metazoa. Our dataset consists of SNS-Seq profiles in Drosophila S2 and Bg3 cells. Small nascent leading strands (SNS) have been purified with an enhanced sensitivity SNS purification protocol. For standard SNS-Seq experiments (from pooled gradient fractions, denoted as "pool"), SNS were purified from two biological replicates. For single-fraction SNS-Seq experiments, two libraries were prepared for each fraction. The genomic coordinates of S2 and Bg3 replication origins are also provided.
Project description:The goal of this study was to analyze global gene expression in specific populations of somatosensory neurons in the periphery, including major, non-overlapping populations that include nociceptors, pruriceptors, and prorioceptors. The mammalian somatosensory nervous system encodes the perception of specific environmental stimuli. The dorsal root ganglion (DRG) contains distinct somatosensory neuron subtypes that innervate diverse peripheral tissues, mediating the detection of thermal, mechanical, proprioceptive, pruriceptive, and nociceptive stimuli. We purified discrete subtypes of mouse DRG somatosensory neurons by flow cytometry using fluorescently labeled mouse lines (SNS-Cre/TdTomato, Parv-Cre/TdTomato) in combination with Isolectin B4-FITC surface staining (IB4). This allowed identification of transcriptional differences between these major populations, revealing enrichment of voltage-gated ion channels, TRP channels, G-protein coupled receptors, transcription factors, and other functionally important classes of genes within specific somatosensory neuron subsets. SNS-Cre mice were bred with Rosa26-TdTomato mice to generate SNS-Cre/TdTomato reporter mice. Parv-Cre mice were bred with Rosa26-TdTomato mice to generate Parv-Cre/TdTomato mice. Isolectin B4-FITC was used to stain the surface of SNS-Cre/TdTomato reporter mice. We used these strategies of fluorescent labeling to purify distinct murine sensory neuron subsets from the dorsal root ganglia (DRG) by fluorescence activated cell sorting (FACS). Neurons were sorted directly in Qiazol for total RNA extraction and microarray analysis. Whole DRG tissue was also included for transcriptome analysis to compare with purified neuronal populations.
Project description:Because of the lack of information, regulation of DNA replication initiation in mammals is still poorly understood. In order to identify general rules, we have mapped replication origins along 1% of the human genome in HeLa cells. We found large gene-poor regions lacking origin and G+C rich regions containing clusters of closely spaced origins. Half of the 283 origins mapped are within or near CpG islands. The connection with gene expression is further reinforced by the observation that most origins overlap with DNAseI hypersensitive sites found at transcriptional regulatory elements. We show, however, that this association is independent of chromatin structure and transcriptional activity. Replication timing analyses coupled to our origin mapping demonstrate that origin dense regions and isolated origins are replicated at every moment in S phase. All together, our data suggest that a relatively strict origin-timing programme regulates DNA replication of the human genome. Keywords: Nascent strands, ENCODE project, HeLAS3 cells, SNS-Chip Four independent preparations of Short Nascent Strands (SNS) were performed. In order to have enough material for microarray hybridisation, we coupled the stringent preparation of SNS with the TLAD method, a technique of linear amplification that can generate several µg of amplified material from 10-20 ng of DNA (Liu et al., 2003).Two were amplified by TLAD (experiments A and B) and hybridized on DNA microarrays, and the other two (experiments C and D) were used for the validation by real-time quantitative PCR (qPCR) of results obtained on micro-arrays. We performed also a gDNA/gDNA hybridization where gDNA are also amplified by TLAD to order to do a control.
Project description:High-grade serous ovarian cancers (HGSOC) are genomically complex, heterogeneous cancers with a high mortality rate, due to acquired chemoresistance and lack of targeted therapy options. Cyclin-dependent kinase inhibitors (CDKi) target the retinoblastoma (RB) signaling network, and have been successfully incorporated into treatment regimens for breast and other cancers. Here, we have compared mechanisms of response and resistance to three CDKi that target either CDK4/6 or CDK2 and abrogate E2F target gene expression. We identify CCNE1 gain and RB1 loss as mechanisms of resistance to CDK4/6 inhibition, whereas receptor tyrosine kinase (RTK) and RAS signaling is associated with CDK2 inhibitor resistance. Mechanistically, we show that ETS factors are mediators of RTK/RAS signaling that cooperate with E2F in cell cycle progression. Consequently, CDK2 inhibition sensitizes cyclin E1-driven but not RAS-driven ovarian cancer cells to platinum-based chemotherapy. In summary, this study outlines a rational approach for incorporating CDKi into treatment regimens for HGSOC. For parental HEY, two replicates per condition (control=10%, SNS032-treated, PD0332991-treated) were analyzed. For CDKi-resistant cells, two individual subclones derived from single cells were analyzed, except OAW28 sublines (two polyclonal populations per subline), OV90-PD/SNS-R (two polyclonal populations) and OV90-SNS-R-1 (polyclonal population, whereas OV90-SNS-R-2 is derived from a single colony).
Project description:Vaccinia virus is a large enveloped DNA virus, which, like all poxviruses, replicates in the cytoplasm of infected cells. Vaccinia was historically thought to encode all the proteins required for its replication. However, recent findings have shown that nuclear host proteins are redirected to the cytoplasm to facilitate viral replication. Among these, topoisomerase 2α (TOP2A) and 2β (TOP2B), which mediate nuclear transcription, DNA replication, and chromosome segregation are the most abundant host proteins associated with nascent viral genomes. Here, we investigate the mechanisms driving TOP2A and TOP2B cytoplasmic translocation and their role in viral replication. We found that early viral protein synthesis induces the cytosolic relocalization of both isoforms, which are subsequently recruited to viral factories by an interaction of their C-terminal domains with the viral ligase, A50. TOP2A promotes replication by interacting with the vaccinia DNA replication machinery. In contrast, TOP2B suppresses replication by enhancing the formation of double-stranded RNA and antiviral granules, containing components of the tRNA splicing ligase complex. Our analysis provides new insights into host-pathogen interactions during poxvirus infection and the role of topoisomerase 2 outside of the nucleus.
Project description:modENCODE_submission_2753 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We will precisely identify sequence elements that direct DNA replication by using chromatin immunoprecipitation of known replication initiation complexes. These experiments will be conducted in multiple cell types and developmental tissues. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: CHIP-seq EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Cell Line: S2-DRSC; Tissue: embryo-derived cell-line; Developmental Stage: late embryonic stage; Sex: Male; EXPERIMENTAL FACTORS: Antibody dORC2
Project description:modENCODE_submission_2754 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We will precisely identify sequence elements that direct DNA replication by using chromatin immunoprecipitation of known replication initiation complexes. These experiments will be conducted in multiple cell types and developmental tissues. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: CHIP-seq EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Cell Line: ML-DmBG3-c2; Tissue: CNS-derived cell-line; Developmental Stage: third instar larval stage; Genotype: y v f mal; Sex: Unknown; EXPERIMENTAL FACTORS: Antibody dORC2
Project description:modENCODE_submission_2755 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We will precisely identify sequence elements that direct DNA replication by using chromatin immunoprecipitation of known replication initiation complexes. These experiments will be conducted in multiple cell types and developmental tissues. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: CHIP-seq EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Cell Line: Kc167; Tissue: embryo-derived cell-line; Developmental Stage: late embryonic stage; Genotype: se/e; Sex: Female; EXPERIMENTAL FACTORS: Antibody dORC2
Project description:modENCODE_submission_2783 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: We will precisely identify sequence elements that direct DNA replication by using chromatin immunoprecipitation of known replication initiation complexes. These experiments will be conducted in multiple cell types and developmental tissues. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: CHIP-seq EXPERIMENT TYPE: CHIP-seq. BIOLOGICAL SOURCE: Cell Line: Kc167; Tissue: embryo-derived cell-line; Developmental Stage: late embryonic stage; Genotype: se/e; Sex: Female; EXPERIMENTAL FACTORS: Antibody Pan MCM2-7 Antibody