The Intra-S Checkpoint Responses to DNA Damage

Iyer, Divya Ramalingam; Rhind, Nick

doi:10.3390/genes8020074

Cited by 92 publications

(79 citation statements)

References 277 publications

(373 reference statements)

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“…As such, fast modulation of DNA synthesis by the replisome seems to be a common strategy evolved in both eukaryotes and prokaryotes. It is tempting to speculate that replisome slowdown in eukaryotes precedes the global DNA damage response (DDR), mediated by protein kinases, which should take more time to be established (57).…”

Section: Discussionmentioning

confidence: 99%

Replisome activity slowdown after exposure to ultraviolet light in Escherichia coli

Soubry

Wang

Reyes‐Lamothe

2019

Proc. Natl. Acad. Sci. U.S.A.

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The replisome is a multiprotein machine that is responsible for replicating DNA. During active DNA synthesis, the replisome tightly associates with DNA. In contrast, after DNA damage, the replisome may disassemble, exposing DNA to breaks and threatening cell survival. Using live cell imaging, we studied the effect of UV light on the replisome of Escherichia coli. Surprisingly, our results showed an increase in Pol III holoenzyme (Pol III HE) foci post-UV that do not colocalize with the DnaB helicase. Formation of these foci is independent of active replication forks and dependent on the presence of the χ subunit of the clamp loader, suggesting recruitment of Pol III HE at sites of DNA repair. Our results also showed a decrease of DnaB helicase foci per cell after UV, consistent with the disassembly of a fraction of the replisomes. By labeling newly synthesized DNA, we demonstrated that a drop in the rate of synthesis is not explained by replisome disassembly alone. Instead, we show that most replisomes continue synthesizing DNA at a slower rate after UV. We propose that the slowdown in replisome activity is a strategy to prevent clashes with engaged DNA repair proteins and preserve the integrity of the replication fork.DNA replication | replisome | fluorescence microscopy | UV | Escherichia coli

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Section: Discussionmentioning

confidence: 99%

Replisome activity slowdown after exposure to ultraviolet light in Escherichia coli

Soubry

Wang

Reyes‐Lamothe

2019

Proc. Natl. Acad. Sci. U.S.A.

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“…We also detected hypermethylation of CHG sites in plants treated with HU, which causes replication stress by depleting cellular dNTP pools. HU-induced replication stress activates the S-phase checkpoint, resembling pol2a mutants where it is constitutively activated (40,54). The replication-stress response is mediated by the ATM-and Rad3-related (ATR) kinase, while ATAXIA TELANGIECTASIA MUTATED (ATM) is required for the response to double-strand breaks (DSBs) (55).…”

Section: Discussionmentioning

confidence: 99%

“…CHG methylation is likely maintained shortly after the passage of the replication fork as CMT3 is exclusively associated with H3.1 in vivo and is highly expressed in replicating cells (64). Increased CHG methylation in pol2a mutants and HU-treated plants correlates with Sphase checkpoint activation (15,40,65), upon which DNA replication is halted until checkpoint-dependent pathways restore cellular conditions suitable for replisome progression (54). We propose that replication arrest provides CMT3 and/or SUVH4/5/6 with a wider time-window to accomplish their enzymatic activities, resulting in more efficient maintenance and thus increased levels of CHG and H3K9 methylation.…”

Section: Discussionmentioning

confidence: 99%

DNA polymerase epsilon is a central coordinator of heterochromatin structure and function in Arabidopsis

Bourguet

López-González

Gómez-Zambrano

et al. 2020

Preprint

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BackgroundChromatin organizes the DNA molecule and regulates its transcriptional activity through epigenetic modifications. Heterochromatic regions of the genome are generally transcriptionally silent while euchromatin is more prone to transcription. During DNA replication, both genetic information and chromatin modifications must be faithfully passed on to daughter strands. There is evidence that DNA polymerases play a role in transcriptional silencing, but the extent of their contribution and how it relates to heterochromatin maintenance is unclear.ResultsWe isolate a strong hypomorphic Arabidopsis thaliana mutant of the POL2A catalytic subunit of DNA polymerase epsilon and show that POL2A is required to stabilize heterochromatin silencing genome wide, likely by preventing replicative stress. We reveal that POL2A inhibits DNA methylation and histone H3 lysine 9 methylation. Hence, release of heterochromatin silencing in POL2A deficient mutants paradoxically occurs in a chromatin context of increased level of these two repressive epigenetic marks. At the nuclear level, POL2A defect is associated with fragmentation of heterochromatin.ConclusionThese results indicate that POL2A is critical to secure both heterochromatin structure and function. We also reveal that unhindered replisome progression is required for the faithful propagation of DNA methylation through the cell cycle.

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“…The first responder to ssDNA exposure is RPA, which is an ssDNA‐binding protein essential for multiple DNA metabolic processes that produce ssDNA intermediates . RPA has a higher abundance and ssDNA affinity compared with other ssDNA‐binding proteins such as RAD51 and its paralogs; therefore, its assembly on ssDNA occurs earlier than that of other ssDNA‐binding proteins . The same is true at stalled replication forks, where RPA is quickly loaded onto the ssDNA to prevent formation of secondary structures that may block further fork processing .…”

Section: Ssdna Protectionmentioning

confidence: 99%

Mechanisms for stalled replication fork stabilization: new targets for synthetic lethality strategies in cancer treatments

et al. 2018

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Timely and faithful duplication of the entire genome depends on completion of replication. Replication forks frequently encounter obstacles that may cause genotoxic fork stalling. Nevertheless, failure to complete replication rarely occurs under normal conditions, which is attributed to an intricate network of proteins that serves to stabilize, repair and restart stalled forks. Indeed, many of the components in this network are encoded by tumour suppressor genes, and their loss of function by mutation or deletion generates genomic instability, a hallmark of cancer. Paradoxically, the same fork-protective network also confers resistance of cancer cells to chemotherapeutic drugs that induce high-level replication stress. Here, we review the mechanisms and major pathways rescuing stalled replication forks, with a focus on fork stabilization preventing fork collapse. A coherent understanding of how cells protect their replication forks will not only provide insight into how cells maintain genome stability, but also unravel potential therapeutic targets for cancers refractory to conventional chemotherapies.

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The Intra-S Checkpoint Responses to DNA Damage

Cited by 92 publications

References 277 publications

Replisome activity slowdown after exposure to ultraviolet light in Escherichia coli

Replisome activity slowdown after exposure to ultraviolet light in Escherichia coli

DNA polymerase epsilon is a central coordinator of heterochromatin structure and function in Arabidopsis

Mechanisms for stalled replication fork stabilization: new targets for synthetic lethality strategies in cancer treatments

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