Checkpoint-mediated DNA polymerase e exonuclease activity curbing counteracts resection-driven fork collapse
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ABSTRACT:
PROVIDER: PRJNA658081 | ENA |
REPOSITORIES: ENA
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Project description:DNA polymerase epsilon (Pole) carries out leading strand synthesis with high fidelity owing to its exonuclease activity. Pole polymerase and exonuclease activities are in balance, due to partitioning of nascent strands between catalytic sites, so that net end resection occurs when synthesis is impaired. Stalling of chromosomal DNA synthesis activates replication checkpoint kinases, required to preserve the functional integrity of replication forks. We found that Pole is phosphorylated in a Rad53CHK1-dependent manner upon fork stalling, likely to limit Pole-driven nascent strand resection that causes replication fork collapse. In stress conditions Pole phosphorylation occurs on serine 430 of the Pol2 catalytic subunit. A S430 phosphomimic limits strand partitioning and exonucleolytic processivity, while non-phosphorylatable Pol2-S430A bypasses checkpoint regulation causing stalled fork resection and collapse. We propose that checkpoint kinases switch Pole to an exonuclease-safe mode by curbing active site partitioning thus preventing nascent strand resection and stabilizing stalled replication forks.
2021-04-30 | GSE156480 | GEO
Project description:DNA polymerase ε (Polε) carries out high-fidelity leading strand synthesis owing to its exonuclease activity. Polε polymerase and exonuclease activities are balanced, because of partitioning of nascent DNA strands between catalytic sites, so that net resection occurs when synthesis is impaired. In vivo, DNA synthesis stalling activates replication checkpoint kinases, which act to preserve the functional integrity of replication forks. We show that stalled Polε drives nascent strand resection causing fork functional collapse, averted via checkpoint-dependent phosphorylation. Polε catalytic subunit Pol2 is phosphorylated on serine 430, influencing partitioning between polymerase and exonuclease active sites. A phosphormimetic S430D change reduces exonucleolysis in vitro and counteracts fork collapse. Conversely, non-phosphorylatable pol2-S430A expression causes resection-driven stressed fork defects. Our findings reveal that checkpoint kinases switch Polε to an exonuclease-safe mode preventing nascent strand resection and stabilizing stalled replication forks. Elective partitioning suppression has implications for the diverse Polε roles in genome integrity maintenance.
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Project description:Transient obstruction of DNA polymerase progression activates the ATR checkpoint kinase, which suppresses fork breakage, strand resection, and RPA accumulation. Herein, we use RPA ChIP-Seq to identify replication-problematic loci (RPLs) across the mammalian genome from ATR inhibition.
2018-10-04 | GSE100790 | GEO
Project description:Transient obstruction of DNA polymerase progression activates the ATR checkpoint kinase, which suppresses fork breakage, strand resection, and RPA accumulation. Herein, we use a developed DNA break-detection assay, BrITL, to identify replication-problematic loci (RPLs) that become processed into persistent double-strand breaks across the mammalian genome from ATR inhibition.
2018-10-04 | GSE115624 | GEO
Project description:During genome replication, the leading strand DNA polymerase conducts continuous synthesis over long stretches of DNA within each replicon. Processive DNA synthesis supports symmetric progression of sister replication forks and efficient genome duplication. To address the mechanisms underlying leading strand polymerase-mediated synthesis, we examine one of its conserved domains, referred to as POPS, in the budding yeast Pol2 enzyme. We provide evidence that POPS supports replication fork symmetry and efficient genome replication via balancing the function of the Pol2 exonuclease domain. We found that the defective growth, slow S phase progression, and impaired genome synthesis associated with a POPS mutation were rescued by abolishing the Pol2 exonuclease activity. The suppressive effects further extended to the increased DNA re-arrangements in the POPS mutant and its negative genetic interactions with mutants of other genome maintenance factors. Significantly, our single molecule replicon-seq data demonstrate that the POPS mutant exhibited genome-wide replication fork asymmetry, and this defect was improved by eliminating the Pol2 exonuclease activity, thus providing a basis for its rescuing of a range of POPS mutant phenotypes. Collectively, these data suggest a model in which balanced activity between a unique Pol2 catalytic domain, and its exonuclease domain facilitates replication fork symmetry and genome maintenance.
2022-09-02 | GSE212101 | GEO
Project description:Transient obstruction of DNA polymerase progression activates the ATR checkpoint kinase, which suppresses fork breakage, strand resection, and RPA accumulation. Herein, we use a developed DNA break-detection assay, BrITL, to identify replication-problematic loci that become processed into persistent double-strand breaks across the human genome from ATR inhibition.
2018-10-04 | GSE115623 | GEO
Project description:The proteins from the Fanconi Anemia (FA) pathway of DNA repair maintain DNA replication fork integrity by preventing the unscheduled degradation of nascent DNA at regions of stalled replication forks. Here, we ask if the bacterial pathogen H. pylori exploits the fork stabilisation machinery to generate double stand breaks (DSBs) and genomic instability. Specifically, we study if the H. pylori virulence factor CagA generates host genomic DSBs through replication fork destabilisation and collapse. An inducible gastric cancer model was used to examine global CagA-dependent transcriptomic and proteomic alterations, using RNA sequencing and SILAC-based mass spectrometry, respectively. The transcriptional alterations were confirmed in gastric cancer cell lines infected with H. pylori. Functional analysis was performed using chromatin fractionation, pulsed-field gel electrophoresis (PFGE), and single molecule DNA replication/repair fiber assays. We found a core set of 31 DNA repair factors including the FA genes FANCI, FANCD2, BRCA1, and BRCA2 that were downregulated following CagA expression. H. pylori infection of gastric cancer cell lines showed downregulation of the aforementioned FA genes in a CagA-dependent manner. Consistent with FA pathway downregulation, chromatin purification studies revealed impaired levels of Rad51 but higher recruitment of the nuclease MRE11 on the chromatin of CagA-expressing cells, suggesting impaired fork protection. In line with the above data, fibre assays revealed higher fork degradation, lower fork speed, daughter strands gap accumulation, and impaired re-start of replication forks in the presence of CagA, indicating compromised genome stability. By downregulating the expression of key DNA repair genes such as FANCI, FANCD2, BRCA1, and BRCA2, H. pylori CagA compromises host replication fork stability and induces DNA DSBs through fork collapse. These data unveil an intriguing example of a bacterial virulence factor that induces genomic instability by interfering with the host replication fork stabilisation machinery.
2022-02-22 | PXD031168 | Pride
Project description:Genome-wide fork-collapse sites in MEFs from ATR inhibition [mouse]
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Project description:Dual Roles of Poly(dA:dT) Tracts in Replication Initiation and Fork Collapse
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Project description:Genome-wide fork-collapse sites in MDA-MB-231 cells from ATR inhibition [human]
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