GNL3/nucleostemin links DNA replication homeostasis and replication forks stability
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ABSTRACT:
PROVIDER: PRJNA749783 | ENA |
REPOSITORIES: ENA
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Project description:The regulation of replication forks stalling and replication origins firing must be tightly coordinated to prevents genomic instability. Here we show that GNL3/nucleostemin, a GTP-binding protein able to shuttle between the nucleolus and the nucleoplasm, limits replicative stress by limiting replication origins firing. GNL3 is in proximity of nascent DNA and its depletion reduces forks speed but increases forks density and replication origins firing. When subjected to exogenous replicative stress, cells impaired for GNL3 exhibits MRN-dependent resection and RPA phosphorylation. Strikingly, inhibition of origin firing using CDC7 inhibitor decreased resection in absence of GNL3 but not in absence of BRCA1, suggesting that GNL3 does not protect nascent strand directly from resection. Consistent with this, overexpression of GNL3 leads to an increased resection in response to replicative stress and enhanced origin firing efficiency. These data indicate that the probability of origins firing is tightly regulated by GNL3 to limit replicative stress. Finally, we show that ORC2 and GNL3 interacts together in the nucleolus. We propose a model where GNL3 level is crucial to determine the correct amount of ORC2 on chromatin by sequestrating it in the nucleolus thanks to the capacity of GNL3 to shuttle between nucleoplasm and nucleolus.
2023-07-01 | GSE180865 | GEO
Project description:Chromatin is dynamically reorganized when DNA replication forks are challenged. However, the process of epigenetic reorganization and its implication for fork stability is poorly understood. Here, we discover a checkpoint regulated cascade of chromatin signaling that activates the histone methyltransferase EHMT2/G9a to catalyze heterochromatin assembly at stressed replication forks. Using biochemical and single molecule chromatin fiber approaches, we show that G9a together with SUV39h1 induces chromatin condensation by accumulating the silent mark, H3K9me1/2/3, in the vicinity of stressed replication forks. This closed conformation is also favored by the G9a-dependent exclusion of the H3K9-demethylase JMJD1A/KDM3A, which facilitates heterochromatin disassembly upon fork restart. Untimely heterochromatin disassembly from stressed forks by KDM3A enables PRIMPOL access, triggering ssDNA gaps formation and sensitizing cells towards chemotherapeutic drugs. These findings may help explaining chemotherapy resistance and poor prognosis observed in cancer patients displaying elevated level of G9a/H3K9me3.modifications (PTMs) in a single mass spectrum. Combined with immunoprecipitation, Nuc-MS quantified nucleosome co-occupancy of histone H3.3 with variant H2A.Z (sixfold over bulk) and the co-occurrence of oncogenic H3.3K27M with euchromatic marks (for example, a >15-fold enrichment of dimethylated H3K79me2). Nuc-MS is highly concordant with chromatin immunoprecipitation-sequencing (ChIP-seq) and offers a new readout of nucleosome-level biology.
2024-11-30 | GSE220073 | GEO
Project description:DNA replication fidelity is essential for maintaining genetic stability. Forks arrested at replication fork barriers can be stabilised by the intra-S phase checkpoint, subsequently being rescued by a converging fork, or resuming when the barrier is removed. However, some arrested forks cannot be stabilised and fork convergence cannot rescue in all situations. Thus, cells have developed homologous recombination-dependent mechanisms to restart persistently inactive forks. To understand the dynamics of HR-restart, we visualized in vivo replication dynamics at an S. pombe replication barrier, RTS1, using polymerase usage sequencing and model replication dynamics by Monte Carlo simulation. We confirm that HR-restarted forks synthesise both strands with Pol d and that Pol a is not used significantly on either strand: the lagging strand template remains as a gap that is filled in later. We further demonstrate that HR-restarted forks progress for >30 kb kilobases without maturing to a d/e configuration and can progress through a fork barrier that arrests canonical forks. Finally, by manipulating lagging strand resection during HR-restart by deleting pku70, we show that the leading strand initiates replication at the same position, demonstrating the stability of the 3' single strand in the context of increased resection.
2020-07-03 | GSE153731 | GEO
Project description:Chromatin is dynamically reorganized when DNA replication forks are challenged. However, the process of epigenetic reorganization and its implication for fork stability is poorly understood. Here, we discover a checkpoint regulated cascade of chromatin signaling that activates 5 the histone methyltransferase EHMT2/G9a to catalyze heterochromatin assembly at stressed replication forks. Using biochemical and single molecule chromatin fiber approaches, we show that G9a together with SUV39h1 induces chromatin compaction by accumulating the repressive modifications, H3K9me1/me2/me3, in the vicinity of stressed replication forks. This closed conformation is also favored by the G9a-dependent exclusion of the H3K9-demethylase 10 JMJD1A/KDM3A, which facilitates heterochromatin disassembly upon fork restart. Untimely heterochromatin disassembly from stressed forks by KDM3A enables PRIMPOL access, triggering ssDNA gap formation and sensitizing cells towards chemotherapeutic drugs. These findings may help explaining chemotherapy resistance and poor prognosis observed in cancer patients displaying elevated level of G9a/H3K9me3.
2023-05-12 | PXD041742 | Pride
Project description:Faithful duplication of DNA is essential for the maintenance of genomic stability in all organisms. DNA synthesis proceeds bi-directionally with continuous synthesis of leading strand DNA and discontinuous synthesis of lagging strand DNA. Herein, we describe a method of enriching and Sequencing of Protein-Associated Nascent strand DNA (eSPAN) to detect whether a protein binds the leading- and lagging-strands of DNA replication forks. We show that Pol-epsilon, PCNA, Cdc45, Mcm6 and Mcm10 preferentially associate with leading strands, whereas Pol-alpha, Pol32, Pol-delta, Rfa1 and Rfc1 associate with lagging strands of hydroxyurea (HU)-stalled replication forks. In contrast, PCNA is enriched at lagging strands of normal replication forks in wild type cells and HU-stalled forks in cells lacking Elg1. These studies demonstrate a strategy to reveal proteins at leading and lagging strands of DNA replication forks, and suggest that the unloading of PCNA from lagging strands of HU-stalled replication forks helps maintain genome integrity.
2014-10-29 | GSE52614 | GEO
Project description:Faithful duplication of DNA is essential for the maintenance of genomic stability in all organisms. DNA synthesis proceeds bi-directionally with continuous synthesis of leading strand DNA and discontinuous synthesis of lagging strand DNA. Herein, we describe a method of enriching and Sequencing of Protein-Associated Nascent strand DNA (eSPAN) to detect whether a protein binds the leading- and lagging-strands of DNA replication forks. We show that Pol-epsilon, PCNA, Cdc45, Mcm6 and Mcm10 preferentially associate with leading strands, whereas Pol-alpha, Pol32, Pol-delta, Rfa1 and Rfc1 associate with lagging strands of hydroxyurea (HU)-stalled replication forks. In contrast, PCNA is enriched at lagging strands of normal replication forks in wild type cells and HU-stalled forks in cells lacking Elg1. These studies demonstrate a strategy to reveal proteins at leading and lagging strands of DNA replication forks, and suggest that the unloading of PCNA from lagging strands of HU-stalled replication forks helps maintain genome integrity. We synchronized yeast cells at G1 and released into early S phase in the presence of BrdU, a nucleotide analog that can be incorporated into newly synthesized DNA strand, and hydroxyurea (HU), a ribonucleotide reductase inhibitor. HU has no effect on initiation of DNA replication at early replication origins, but inhibit late replication firing. In addition, replication forks are stalled due to depletion of dNTPs. We then performed chromatin-immunoprecipitation of 12 proteins of interest following a standard procedure. Protein-bound DNAs were then reverse-crosslinked and double strand DNA was denatured. Nascent DNA was enriched by immunoprecipitation using anti-BrdU antibodies. The recovered ssDNA was first marked with ligation to one oligo at 3M-bM-^@M-^Y end before conversion to dsDNA for library preparation and sequencing. In this way, the directionality of ssDNA and therefore strand information of each sequenced DNA were known. The sequencing tag was mapped to both Watson (red) and Crick (blue) strands of the reference genome. In addition to ChIP-eSPAN, we also performed BrdU-IP and single strand DNA sequence (BrdU-ssSeq) and protein ChIP followed by single-strand DNA sequencing (ChIP-ssSeq) for each corresponding ChIP-eSPAN experiment. We also performed Mcm4 and Mcm6 ChIP-seq using cells synchronized at G1 phase of the cell cycle for identification of replication origins in comparison with published dataset. Some protein ChIP-ssSeq and ChIP-eSPAN experiments were repeated and the data fits well each other. Therefore, we did not repeat all protein ChIP-ssSeq and ChIP-eSPAN experiments.
2014-10-29 | E-GEOD-52614 | biostudies-arrayexpress
Project description:Chromosome duplication normally initiates via the assembly of replication fork complexes at defined origins. DNA synthesis by any one fork is thought to cease when it meets another travelling in the opposite direction, at which stage the replication machinery may simply dissociate before the nascent strands are finally ligated. But what actually happens is not clear. Here we present evidence consistent with the idea that every fork collision has the potential to trigger re-replication of the already replicated DNA, thus posing a threat to genomic integrity. In Escherichia coli this threat is kept at bay by the RecG DNA translocase. Without RecG, replication initiates where forks meet, establishing new forks with the potential to sustain cell growth and division in the absence of an active origin. The studies reported raise the question of how eukaryotic and archaeal cells are able to exploit multiple origins for the duplication of each chromosome without any apparent ill effect from the consequent multiple fork collisions. Measurement of replication dynamics (marker frequency analysis; MFA) for E. coli strains, including wild-type and various mutants.
2013-07-22 | E-GEOD-41975 | biostudies-arrayexpress
Project description:Here we analysed the role of yeast Senataxin (Sen1) in coordinating replication with transcription and in protecting genome integrity. Senataxin is mutated in the two severe neurodegenerative diseases AOA2 and ALS4. We show that a fraction of Sen1/Senataxin DNA/RNA helicase associates with replication forks and protects the integrity of those fork encountering highly expressed RNAPII genes. sen1 mutants accumulate aberrant DNA structures and RNA-DNA hybrids while forks clash head-on with RNAPII transcription units and counteract recombinogenic events and accumulation of checkpoint signals. Nrd1, which acts togheter with Sen1 in trascription temination, is not recruited at replication forks. nrd1 mutants does not display replication defects, high genome instability and checkpoint activation observed in sen1 mutants The Sen1 function in replication can be therefore separable from its role in RNA processing. We propose a role for Sen1/Senataxin during chromosome replication in facilitating replisome progression across RNAPII transcribed genes thus preventing DNA-RNA hybrids accumulation when forks encounter nascent transcripts on the lagging strand template. Chip on chip analysis was carried out as described (Bermejo et al., 2011), employing anti-Flag monoclonal antibody M2 (Sigma-Aldrich) Labelled probes were hybridized to Affymetrix S.cerevisiae Tiling 1.0 (P/N 900645) arrays and processed with TAS software.
2012-11-09 | E-GEOD-39139 | biostudies-arrayexpress
Project description:Replication fork reversal is a key protective mechanism against replication stress in higher eukaryotic cells and occurs via a series of coordinated enzymatic reactions. The Bloom syndrome gene product, BLM, is a member of the highly conserved RecQ helicase family and has been implicated in this process, but its precise regulation and role remain poorly understood. Here, we show that, upon replication stress, the GCFC domain-containing protein TFIP11 competes with the BLM helicase for association with stalled replication forks, thereby facilitates RAD51-mediated stalled fork reversal. Consequently, loss of TFIP11 results in aberrant accumulation of BLM at stalled forks, which in turn compromises RAD51 recruitment, impairs replication stress-induced fork reversal and slowing, hypersensitizes cells to replication stress-inducing agents, and enhances chromosomal instability. These findings reveal a previously unidentified regulatory mechanism that modulates the activities of BLM and RAD51 at stalled forks and thus genome integrity.
2024-05-24 | PXD042222 | Pride
Project description:Topological stress can cause replication forks to stall as they converge upon one another during termination of vertebrate DNA synthesis. However, replication forks ultimately overcome topological stress and complete DNA synthesis, suggesting that alternative mechanisms can overcome topological stress. We performed a proteomic analysis of converging replication forks that were stalled by topological stress induced by loss or inhibition of topoisomerase IIα (TOP2α). Plasmid DNA was replicated in mock- or TOP2α-depleted Xenopus egg extracts as previously described (Heintzman et al. 2019). In parallel, replication was performed in the presence of the TOP2 inhibitor ICRF-193 (‘TOP2-i’) as an alternate means of preventing TOP2 activity (Heintzman et al. 2019). Chromatinized plasmid DNA was recovered 18 minutes after the onset of DNA synthesis, when most forks have normally merged but are stalled when TOP2 activity is prevented (Heintzman et al. 2019). Chromatin-bound proteins were recovered (Larsen et al. 2019) then analyzed by chromatin mass spectrometry and quantified by label free quantification.
2023-02-21 | PXD031170 | Pride