Genome-scale analysis of metazoan replication origins reveals their organization in specific but flexible sites defined by conserved features.
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PROVIDER: PRJNA139989 | ENA |
REPOSITORIES: ENA
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Project description:In metazoans, thousands of DNA replication origins (Oris) are activated to replicate DNA at each cell cycle. Although their timing of activation is better understood, their genomic organization and their genetic nature remain elusive. Here, we identified Oris by nascent strand (NS) purification and characterized their common features by performing a genome-wide analysis in both Drosophila and mouse cell lines. We show that in both species most CpG islands (CGI) contain Oris, although methylation is nearly absent in Drosophila, suggesting that this epigenetic mark is not crucial for defining the initiation event. Moreover, nascent strands at the borders of CGIs show a striking bimodal distribution, suggestive of a dual initiation event. We also found that Oris contain a unique nucleotide skew around NS peaks, characterized by G/T and C/A over-representation at 5’ and 3’ of the Ori sites, respectively. GC-rich elements are detected, which are good predictors of Oris, in both mouse and Drosophila, suggesting that common sequence features are part of metazoan Oris. In the heterochromatic chromosome 4 of Drosophila, Oris are strongly correlated with HP1 binding sites. At the chromosome level, we show that Oris are organized in Ori-rich and -poor regions that co-localize with early and late replicating domains, respectively. Finally, the genome-wide analysis was coupled with a DNA combing analysis of the in-vivo spacing of replication origins. The results suggest that Oris are in large excess, and organized in groups of site-specific but flexible origins that define replicons, where a single origin is used in each group. This organization provides both site specificity and Ori firing flexibility in each replicon, allowing possible adaptation of DNA replication to environmental cues and cell fates.
2011-07-28 | GSE29183 | GEO
Project description:In metazoans, thousands of DNA replication origins (Oris) are activated at each cell cycle. Their genomic organization and their genetic nature remain elusive. Here, we characterized Oris by nascent strand (NS) purification and a genome-wide analysis in Drosophila and mouse cells. We show that in both species most CpG islands (CGI) contain Oris, although methylation is nearly absent in Drosophila, indicating that this epigenetic mark is not crucial for defining the activated origin. Initiation of DNA synthesis starts at the borders of CGI, resulting in a striking bimodal distribution of NS, suggestive of a dual initiation event. Oris contain a unique nucleotide skew around NS peaks, characterized by G/T and C/A overrepresentation at the 5' and 3' of Ori sites, respectively. Repeated GC-rich elements were detected, which are good predictors of Oris, suggesting that common sequence features are part of metazoan Oris. In the heterochromatic chromosome 4 of Drosophila, Oris correlated with HP1 binding sites. At the chromosome level, regions rich in Oris are early replicating, whereas Ori-poor regions are late replicating. The genome-wide analysis was coupled with a DNA combing analysis to unravel the organization of Oris. The results indicate that Oris are in a large excess, but their activation does not occur at random. They are organized in groups of site-specific but flexible origins that define replicons, where a single origin is activated in each replicon. This organization provides both site specificity and Ori firing flexibility in each replicon, allowing possible adaptation to environmental cues and cell fates.
| S-EPMC3166829 | biostudies-literature
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.
2015-04-23 | E-GEOD-65692 | biostudies-arrayexpress
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.
2015-04-23 | GSE65692 | GEO
Project description:Comparative population genomics in 76 metazoan species (popphyl project)
| PRJNA249058 | ENA
Project description:Hi-C sequencing of holozoan non-metazoan organisms
| PRJNA818537 | ENA
Project description:Dataset of metazoan identification using 18s eDNA metabarcoding from seawater in the Hybrid-Ocean Thermal Energy Conversion (H-OTEC) site of Peninsular Malaysia.
| PRJNA1163757 | ENA
Project description:DNA replication initiates at defined sites called origins, which serve as binding sites for initiator proteins that recruit the replicative machinery. Origins differ in number and structure across the three domains of life1 and their properties determine the dynamics of chromosome replication. Bacteria and some archaea replicate from single origins, whilst most archaea and all eukaryotes replicate using multiple origins. Initiation mechanisms that rely on homologous recombination operate in some viruses. Here we show that such mechanisms also operate in archaea. We have used deep sequencing to study replication in Haloferax volcanii. Four chromosomal origins of differing activity were identified. Deletion of individual origins resulted in perturbed replication dynamics and reduced growth. However, a strain lacking all origins has no apparent defects and grows significantly faster than wild-type. Origin-less cells initiate replication at dispersed sites rather than at discrete origins and have an absolute requirement for the recombinase RadA, unlike strains lacking individual origins. Our results demonstrate that homologous recombination alone can efficiently initiate the replication of an entire cellular genome. This raises the question of what purpose replication origins serve and why they have evolved. Measurement of replication dynamics (marker frequency analysis; MFA) for Haloferax volcanii strains, including wild-type, the laboratory strain, individual and combinations of replication origin deletions.
2013-11-03 | E-GEOD-41961 | biostudies-arrayexpress
Project description:DNA replication initiates at defined sites called origins, which serve as binding sites for initiator proteins that recruit the replicative machinery. Origins differ in number and structure across the three domains of life1 and their properties determine the dynamics of chromosome replication. Bacteria and some archaea replicate from single origins, whilst most archaea and all eukaryotes replicate using multiple origins. Initiation mechanisms that rely on homologous recombination operate in some viruses. Here we show that such mechanisms also operate in archaea. We have used deep sequencing to study replication in Haloferax volcanii. Four chromosomal origins of differing activity were identified. Deletion of individual origins resulted in perturbed replication dynamics and reduced growth. However, a strain lacking all origins has no apparent defects and grows significantly faster than wild-type. Origin-less cells initiate replication at dispersed sites rather than at discrete origins and have an absolute requirement for the recombinase RadA, unlike strains lacking individual origins. Our results demonstrate that homologous recombination alone can efficiently initiate the replication of an entire cellular genome. This raises the question of what purpose replication origins serve and why they have evolved.
2013-11-03 | GSE41961 | GEO
Project description:Background: The replication program of vertebrate genomes is driven by the chromosomal distribution and timing of activation of ten of thousands replication origins. Genome-wide studies have shown the frequent association of origins with promoters and CpG islands, and their enrichment in G-quadruplexes sequence motifs (G4). However the genetic determinants driving their activity remain poorly understood. To gain insight on functional constraints operating on replication origins and on their spatial distribution, we conduct the first evolutionary comparison of genome-wide origins maps across vertebrates. Results: We generated a high resolution genome-wide map of chicken replication origins (the first of a bird genome), and performed an extensive comparison with human and mouse maps. The analysis of intra-species polymorphism revealed a strong depletion of genetic diversity on a ∼ 40bp region centered on the replication initiation loci. Surprisingly, this depletion in genetic diversity is not linked to the presence of G4 motifs, nor to the association with promoters or CpG islands. In contrast, we also show that origins have experienced a rapid turnover during vertebrates evolution, since pairwise comparisons of origin maps revealed that only 4 to 24% of them are conserved between any two species. Conclusions: This study unravels the existence of a novel genetic determinant of replication origins, whose precise functional role remains to be determined. Despite the importance of replication initiation activity for the fitness of organisms, the distribution of replication origins along vertebrate chromosomes is highly flexible.
2019-03-06 | GSE119488 | GEO