Project description:DNA replication is a tightly regulated process that ensures the precise duplication of the genome during cell cycle. Licensing and activation of eukaryotic replication origins are controlled primarily by chromatin. However, the chromatin features involved and the regulatory mechanism remain largely unknown. In this study, we found that H2A.Z binds Suv420H1 directly to promote H4K20me2 deposition on nucleosome both in vitro and in vivo. ORC1 is subsequently recruited to chromatin for licensing and activation of early replication origins. Depletion of H2A.Z results in defects of DNA replication and cell proliferation in both HeLa cells and T cells. Thus, our results provide novel mechanistic insights that the histone variant H2A.Z epigenetically regulates licensing and activation of the early DNA replication origins through the Suv420H1-H4K20me2-ORC1 pathway.
Project description:Cyclin-dependent kinases (CDKs) coordinate DNA replication and cell division, and play key roles in tissue homeostasis, genome stability and cancer development. The first step in replication is origin licensing, when minichromosome maintenance (MCM) helicases are loaded onto DNA by CDC6, CDT1 and the origin recognition complex (ORC). In yeast, origin licensing starts when CDK activity plummets in G1 phase, reinforcing the view that CDKs inhibit licensing. Here we show that, in human cells, CDK4/6 activity promotes origin licensing. By combining rapid protein degradation and time-resolved EdU-sequencing, we find that CDK4/6 activity acts epistatically to CDC6 and CDT1 in G1 phase and counteracts RB pocket proteins to promote origin licensing. Therapeutic CDK4/6 inhibitors block MCM and ORC6 loading, which we exploit to trigger mitosis with unreplicated DNA in p53-deficient cells. The CDK4/6-RB axis thus links replication licensing to proliferation, which has implications for human cell fate control and cancer therapy design.
Project description:Genomic integrity requires faithful chromosome duplication. Origins of replication are the genomic sites where DNA replication initiates in every cell cycle. There are multiple origins scattered throughout the eukaryotic genome whose genome-wide identification has been a hard challenge, especially in multicellular organisms. Thus, very little is known on the distinctive features of origins in terms of DNA sequence and chromatin context at a genomic scale. Here we have profiled origins in Arabidopsis thaliana by high-throughput sequencing of purified nascent DNA strands. We have identified 1543 replication origins, which were uniformly distributed across the Arabidopsis genome and enriched in binding signals of two replication initiation proteins, CDC6 and ORC1. We have also analyzed novel epigenome maps of various histone modifications and found links between origins and epigenetic signatures, which differ from or have not been reported for other eukaryotic systems. Arabidopsis origins tend to be embedded in G+C-rich regions within the 5M-bM-^@M-^Y half of genes, enriched in histone H2A.Z, H3K4me2/3 and acetylated H4, and depleted of H3K4me1 and H3K9me2. Our data establish the basis for the understanding of the epigenetic specification of origins of replication in Arabidopsis and have implications for the mechanisms of origin specification in other eukaryotes. This SuperSeries is composed of the following subset Series: GSE21781: Mapping origins of replication in Arabidopsis thaliana: Examination of BrdU labelled DNA and unlabelled DNA in one cell type GSE21827: Mapping origins of replication in Arabidopsis thaliana: H3K4ac ChIP vs. unmodified H3 ChIP Refer to individual Series
Project description:Genomic integrity requires faithful chromosome duplication. Origins of replication are the genomic sites where DNA replication initiates in every cell cycle. There are multiple origins scattered throughout the eukaryotic genome whose genome-wide identification has been a hard challenge, especially in multicellular organisms. Thus, very little is known on the distinctive features of origins in terms of DNA sequence and chromatin context at a genomic scale. Here we have profiled origins in Arabidopsis thaliana by high-throughput sequencing of purified nascent DNA strands. We have identified 1543 replication origins, which were uniformly distributed across the Arabidopsis genome and enriched in binding signals of two replication initiation proteins, CDC6 and ORC1. We have also analyzed novel epigenome maps of various histone modifications and found links between origins and epigenetic signatures, which differ from or have not been reported for other eukaryotic systems. Arabidopsis origins tend to be embedded in G+C-rich regions within the 5’ half of genes, enriched in histone H2A.Z, H3K4me2/3 and acetylated H4, and depleted of H3K4me1 and H3K9me2. Our data establish the basis for the understanding of the epigenetic specification of origins of replication in Arabidopsis and have implications for the mechanisms of origin specification in other eukaryotes. This SuperSeries is composed of the SubSeries listed below.
Project description:modENCODE_submission_709 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: Early origins of replication were identified by treating cells with hydroxyurea (HU), a potent inhibitor of nucleotide synthesis, in the presence of the nucleotide analogue BrdU. Treatment of synchronized Kc167 cells with HU stalls replication forks and activates the intra S-phase checkpoint, thereby limiting BrdU incorporation to those sequences immediately adjacent to early activating replication origins. BrdU enriched sequences surrounding early origins of replication are then enriched by immunoprecipitation with an anti-BrdU antibody. Early origins are then detected by hybridization to Agilent genomic tiling arrays. Peaks are called using MA2C (http://liulab.dfci.harvard.edu/MA2C/MA2C.htm) Keywords: CHIP-chip For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf EXPERIMENT TYPE: CHIP-chip. BIOLOGICAL SOURCE: Cell Line: Kc167; Tissue: embryo-derived cell-line; Genotype: se/e; Sex: Female NUMBER OF REPLICATES: 4; EXPERIMENTAL FACTORS: Cell Line Kc167
Project description:modENCODE_submission_709 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: Early origins of replication were identified by treating cells with hydroxyurea (HU), a potent inhibitor of nucleotide synthesis, in the presence of the nucleotide analogue BrdU. Treatment of synchronized Kc167 cells with HU stalls replication forks and activates the intra S-phase checkpoint, thereby limiting BrdU incorporation to those sequences immediately adjacent to early activating replication origins. BrdU enriched sequences surrounding early origins of replication are then enriched by immunoprecipitation with an anti-BrdU antibody. Early origins are then detected by hybridization to Agilent genomic tiling arrays. Peaks are called using MA2C (http://liulab.dfci.harvard.edu/MA2C/MA2C.htm) Keywords: CHIP-chip For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf
Project description:modENCODE_submission_710 This submission comes from a modENCODE project of David MacAlpine. For full list of modENCODE projects, see http://www.genome.gov/26524648 Project Goal: Early origins of replication were identified by treating cells with hydroxyurea (HU), a potent inhibitor of nucleotide synthesis, in the presence of the nucleotide analogue BrdU. Treatment of synchronized S2-DRSC cells with HU stalls replication forks and activates the intra S-phase checkpoint, thereby limiting BrdU incorporation to those sequences immediately adjacent to early activating replication origins. BrdU enriched sequences surrounding early origins of replication are then enriched by immunoprecipitation with an anti-BrdU antibody. Early origins are then detected by hybridization to Agilent genomic tiling arrays. Peaks are called using MA2C (http://liulab.dfci.harvard.edu/MA2C/MA2C.htm) Keywords: CHIP-chip For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf EXPERIMENT TYPE: CHIP-chip. BIOLOGICAL SOURCE: Cell Line: S2-DRSC; Tissue: embryo-derived cell-line; Sex: Male NUMBER OF REPLICATES: 3; EXPERIMENTAL FACTORS: Cell Line S2-DRSC
Project description:Genomic integrity requires faithful chromosome duplication. Origins of replication are the genomic sites where DNA replication initiates in every cell cycle. There are multiple origins scattered throughout the eukaryotic genome whose genome-wide identification has been a hard challenge, especially in multicellular organisms. Thus, very little is known on the distinctive features of origins in terms of DNA sequence and chromatin context at a genomic scale. Here we have profiled origins in Arabidopsis thaliana by high-throughput sequencing of purified nascent DNA strands. We have identified 1543 replication origins, which were uniformly distributed across the Arabidopsis genome and enriched in binding signals of two replication initiation proteins, CDC6 and ORC1. We have also analyzed novel epigenome maps of various histone modifications and found links between origins and epigenetic signatures, which differ from or have not been reported for other eukaryotic systems. Arabidopsis origins tend to be embedded in G+C-rich regions within the 5M-bM-^@M-^Y half of genes, enriched in histone H2A.Z, H3K4me2/3 and acetylated H3 and H4, and depleted of H3K4me1 and H3K9me2. Our data establish the basis for the understanding of the epigenetic specification of origins of replication in Arabidopsis and have implications for the mechanisms of origin specification in other eukaryotes. H4K5ac ChIP vs. unmodified H3 ChIP. Our study utilizes the following datasets in addition to the data we generated: H3K4me1: GSM343141 H3K4me2: GSM343143 H3K4me3: GSM343144 H3K9me2: GSM310840 H2AZ: GSM307373