scholarly journals Tight Interplay between Replication Stress and Competence Induction in Streptococcus pneumoniae

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1938
Author(s):  
Vanessa Khemici ◽  
Marc Prudhomme ◽  
Patrice Polard
Keyword(s):  
Streptococcus Pneumoniae ◽  
Gene Dosage ◽  
Sos Response ◽  
Replication Stress ◽  
Strand Break ◽  
Recombinational Repair ◽  
Replication Forks ◽  
Genome Damage ◽  
Initiation Of Replication ◽  
Competence Induction

Cells respond to genome damage by inducing restorative programs, typified by the SOS response of Escherichia coli. Streptococcus pneumoniae (the pneumococcus), with no equivalent to the SOS system, induces the genetic program of competence in response to many types of stress, including genotoxic drugs. The pneumococcal competence regulon is controlled by the origin-proximal, auto-inducible comCDE operon. It was previously proposed that replication stress induces competence through continued initiation of replication in cells with arrested forks, thereby increasing the relative comCDE gene dosage and expression and accelerating the onset of competence. We have further investigated competence induction by genome stress. We find that absence of RecA recombinase stimulates competence induction, in contrast to SOS response, and that double-strand break repair (RexB) and gap repair (RecO, RecR) initiation effectors confer a similar effect, implying that recombinational repair removes competence induction signals. Failure of replication forks provoked by titrating PolC polymerase with the base analogue HPUra, over-supplying DnaA initiator, or under-supplying DnaE polymerase or DnaC helicase stimulated competence induction. This induction was not correlated with concurrent changes in origin-proximal gene dosage. Our results point to arrested and unrepaired replication forks, rather than increased comCDE dosage, as a basic trigger of pneumococcal competence.

scholarly journals DNA2 in Chromosome Stability and Cell Survival—Is It All about Replication Forks?

2021 ◽  
Vol 22 (8) ◽  
pp. 3984
Author(s):  
Jessica J. R. Hudson ◽  
Ulrich Rass
Keyword(s):  
Replication Stress ◽  
Strand Break ◽  
Replication Forks ◽  
Phenotypic Data ◽  
Checkpoint Activation ◽  
Dna Double Strand Break ◽  
Promising Target ◽  
Anti Cancer ◽  
Okazaki Fragment Processing ◽  
Response And Recovery

The conserved nuclease-helicase DNA2 has been linked to mitochondrial myopathy, Seckel syndrome, and cancer. Across species, the protein is indispensable for cell proliferation. On the molecular level, DNA2 has been implicated in DNA double-strand break (DSB) repair, checkpoint activation, Okazaki fragment processing (OFP), and telomere homeostasis. More recently, a critical contribution of DNA2 to the replication stress response and recovery of stalled DNA replication forks (RFs) has emerged. Here, we review the available functional and phenotypic data and propose that the major cellular defects associated with DNA2 dysfunction, and the links that exist with human disease, can be rationalized through the fundamental importance of DNA2-dependent RF recovery to genome duplication. Being a crucial player at stalled RFs, DNA2 is a promising target for anti-cancer therapy aimed at eliminating cancer cells by replication-stress overload.

scholarly journals 53BP1 Mediates ATR-Chk1 Signaling and Protects Replication Forks under Conditions of Replication Stress

2018 ◽  
Vol 38 (8) ◽  
Author(s):  
Joonyoung Her ◽  
Chandni Ray ◽  
Jake Altshuler ◽  
Haiyan Zheng ◽  
Samuel F. Bunting
Keyword(s):  
Cell Death ◽  
Cellular Response ◽  
Ex Vivo ◽  
Replication Stress ◽  
Strand Break ◽  
Replication Forks ◽  
P53 Signaling ◽  
Dna Double Strand Break ◽  
Short Term Exposure ◽  
Stress Signal

ABSTRACTComplete replication of the genome is an essential prerequisite for normal cell division, but a variety of factors can block the replisome, triggering replication stress and potentially causing mutation or cell death. The cellular response to replication stress involves recruitment of proteins to stabilize the replication fork and transmit a stress signal to pause the cell cycle and allow fork restart. We find that the ubiquitously expressed DNA damage response factor 53BP1 is required for the normal response to replication stress. Using primary,ex vivoB cells, we showed that a population of 53BP1−/−cells in early S phase is hypersensitive to short-term exposure to three different agents that induce replication stress. 53BP1 localizes to a subset of replication forks following induced replication stress, and an absence of 53BP1 leads to defective ATR-Chk1-p53 signaling and caspase 3-mediated cell death. Nascent replicated DNA additionally undergoes degradation in 53BP1−/−cells. These results show that 53BP1 plays an important role in protecting replication forks during the cellular response to replication stress, in addition to the previously characterized role of 53BP1 in DNA double-strand break repair.

scholarly journals The RECQL helicase prevents replication fork collapse during replication stress

2020 ◽  
Vol 3 (10) ◽  
pp. e202000668
Author(s):  
Bente Benedict ◽  
Marit AE van Bueren ◽  
Frank PA van Gemert ◽  
Cor Lieftink ◽  
Sergi Guerrero Llobet ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Replication Fork ◽  
Critical Role ◽  
Replication Stress ◽  
Strand Break ◽  
Replication Forks ◽  
Replication Fork Progression ◽  
Dna Dsbs ◽  
Fork Stalling ◽  
Stalled Replication Forks

Most tumors lack the G1/S phase checkpoint and are insensitive to antigrowth signals. Loss of G1/S control can severely perturb DNA replication as revealed by slow replication fork progression and frequent replication fork stalling. Cancer cells may thus rely on specific pathways that mitigate the deleterious consequences of replication stress. To identify vulnerabilities of cells suffering from replication stress, we performed an shRNA-based genetic screen. We report that the RECQL helicase is specifically essential in replication stress conditions and protects stalled replication forks against MRE11-dependent double strand break (DSB) formation. In line with these findings, knockdown of RECQL in different cancer cells increased the level of DNA DSBs. Thus, RECQL plays a critical role in sustaining DNA synthesis under conditions of replication stress and as such may represent a target for cancer therapy.

scholarly journals Proteome dynamics at broken replication forks reveal a distinct ATM-directed repair response suppressing DNA double-strand break ubiquitination

2021 ◽  
Author(s):  
Kyosuke Nakamura ◽  
Georg Kustatscher ◽  
Constance Alabert ◽  
Martina Hödl ◽  
Ignasi Forne ◽  
...  
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Replication Forks ◽  
Dna Double Strand Break

scholarly journals The Bloom syndrome complex senses RPA-coated single-stranded DNA to restart stalled replication forks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ann-Marie K. Shorrocks ◽  
Samuel E. Jones ◽  
Kaima Tsukada ◽  
Carl A. Morrow ◽  
Zoulikha Belblidia ◽  
...  
Keyword(s):  
Replication Stress ◽  
Bloom Syndrome ◽  
Holliday Junctions ◽  
Replication Forks ◽  
Single Stranded Dna ◽  
Ssdna Binding ◽  
Ssdna Binding Protein ◽  
Dna Replication Stress ◽  
Dna End Resection ◽  
Stalled Replication Forks

AbstractThe Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1 and RMI2 to form the BTR complex, which dissolves double Holliday junctions to produce non-crossover homologous recombination (HR) products. BLM also promotes DNA-end resection, restart of stalled replication forks, and processing of ultra-fine DNA bridges in mitosis. How these activities of the BTR complex are regulated in cells is still unclear. Here, we identify multiple conserved motifs within the BTR complex that interact cooperatively with the single-stranded DNA (ssDNA)-binding protein RPA. Furthermore, we demonstrate that RPA-binding is required for stable BLM recruitment to sites of DNA replication stress and for fork restart, but not for its roles in HR or mitosis. Our findings suggest a model in which the BTR complex contains the intrinsic ability to sense levels of RPA-ssDNA at replication forks, which controls BLM recruitment and activation in response to replication stress.

scholarly journals Why Do Centromeres Evolve So Fast: BIR Replication, Hypermutation, Transposition, and Molecular-Drive

2020 ◽  
Author(s):  
William Rice
Keyword(s):  
Rapid Evolution ◽  
Evolutionary Process ◽  
Epigenetic Mark ◽  
Replication Forks ◽  
Nucleotide Substitutions ◽  
Molecular Drive ◽  
Repeat Structure ◽  
Repeat Units ◽  
Initiation Of Replication ◽  
Genomic Regions

Centromeres are among the fastest evolving genomic regions in a diverse array of organisms. The evolutionary process driving this rapid evolution has not been unambiguously established. Here I integrate diverse information to motivate a model in which centromeres evolve rapidly because of their intrinsic molecular phenotype: they tightly bind centromeric proteins throughout the cell cycle. DNA-bound proteins have been shown to cause stalling and collapse of DNA replication forks in many genomic regions, including centromeres. Collapsed replication forks generate one-sided double strand breaks (DSBs) that are repaired by the Break-Induced Repair (BIR) pathway. Here I show why this repair is expected to generate tandem repeat structure and three key features at centromeres: i) increased nucleotide substitution mutation rates, ii) out-of- register re-initiation of replication that leads to indels spanning one or more repeat units, and iii) elevated rates of large and small transpositions within centromeres and between genomic regions. These phenotypes lead to: i) a rapid rate of nucleotide substitutions within a clade of centromeric sequences, ii) continual turnover of monomers within centromeres that fosters molecular-drift and molecular-drive, and iii) recurrent quantum leaps in centromere sequence due to the formation of mosaic monomers and new sequences transposed into non-homologous centromeres. These features are plausibly the major reason centromeres evolve so rapidly. I also speculate on how the DNA sequence of centromeres might perpetually coevolve with the protein sequence of histone CENH3 –the major epigenetic mark of centromeres.

scholarly journals DDX11 loss causes replication stress and pharmacologically exploitable DNA repair defects

2021 ◽  
Vol 118 (17) ◽  
pp. e2024258118
Author(s):  
Nanda Kumar Jegadesan ◽  
Dana Branzei
Keyword(s):  
Dna Repair ◽  
Cancer Cells ◽  
Drug Hypersensitivity ◽  
Replication Stress ◽  
Strand Break ◽  
Parp Inhibitors ◽  
Dna Helicase ◽  
Brca1 And Brca2 ◽  
Focus Formation ◽  
Chemotherapy Drug

DDX11 encodes an iron–sulfur cluster DNA helicase required for development, mutated, and overexpressed in cancers. Here, we show that loss of DDX11 causes replication stress and sensitizes cancer cells to DNA damaging agents, including poly ADP ribose polymerase (PARP) inhibitors and platinum drugs. We find that DDX11 helicase activity prevents chemotherapy drug hypersensitivity and accumulation of DNA damage. Mechanistically, DDX11 acts downstream of 53BP1 to mediate homology-directed repair and RAD51 focus formation in manners nonredundant with BRCA1 and BRCA2. As a result, DDX11 down-regulation aggravates the chemotherapeutic sensitivity of BRCA1/2-mutated cancers and resensitizes chemotherapy drug–resistant BRCA1/2-mutated cancer cells that regained homologous recombination proficiency. The results further indicate that DDX11 facilitates recombination repair by assisting double strand break resection and the loading of both RPA and RAD51 on single-stranded DNA substrates. We propose DDX11 as a potential target in cancers by creating pharmacologically exploitable DNA repair vulnerabilities.

scholarly journals RAD50 Is Required for Efficient Initiation of Resection and Recombinational Repair at Random, γ-Induced Double-Strand Break Ends

PLoS Genetics ◽  
2009 ◽  
Vol 5 (9) ◽  
pp. e1000656 ◽  
Author(s):  
Jim Westmoreland ◽  
Wenjian Ma ◽  
Yan Yan ◽  
Kelly Van Hulle ◽  
Anna Malkova ◽  
...  
Keyword(s):  
Strand Break ◽  
Double Strand Break ◽  
Recombinational Repair

scholarly journals XLF and H2AX function in series to promote replication fork stability

2019 ◽  
Vol 218 (7) ◽  
pp. 2113-2123 ◽  
Author(s):  
Bo-Ruei Chen ◽  
Annabel Quinet ◽  
Andrea K. Byrum ◽  
Jessica Jackson ◽  
Matteo Berti ◽  
...  
Keyword(s):  
Replication Fork ◽  
Strand Break ◽  
Replication Forks ◽  
End Joining ◽  
Replication Fork Progression ◽  
In Series ◽  
Non Homologous End Joining ◽  
C Complex ◽  
Factor C ◽  
Atr Kinase

XRCC4-like factor (XLF) is a non-homologous end joining (NHEJ) DNA double strand break repair protein. However, XLF deficiency leads to phenotypes in mice and humans that are not necessarily consistent with an isolated defect in NHEJ. Here we show that XLF functions during DNA replication. XLF undergoes cell division cycle 7–dependent phosphorylation; associates with the replication factor C complex, a critical component of the replisome; and is found at replication forks. XLF deficiency leads to defects in replication fork progression and an increase in fork reversal. The additional loss of H2AX, which protects DNA ends from resection, leads to a requirement for ATR to prevent an MRE11-dependent loss of newly synthesized DNA and activation of DNA damage response. Moreover, H2ax−/−:Xlf−/− cells exhibit a marked dependence on the ATR kinase for survival. We propose that XLF and H2AX function in series to prevent replication stress induced by the MRE11-dependent resection of regressed arms at reversed replication forks.

scholarly journals Physiological and Pathological Roles of RAD52 at DNA Replication Forks

Cancers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 402 ◽  
Author(s):  
Eva Malacaria ◽  
Masayoshi Honda ◽  
Annapaola Franchitto ◽  
Maria Spies ◽  
Pietro Pichierri
Keyword(s):  
Dna Replication ◽  
Cancer Cells ◽  
Molecular Mechanisms ◽  
Full Range ◽  
Therapeutic Targets ◽  
Replication Stress ◽  
Replication Forks ◽  
Dna Double Strand Breaks ◽  
Rad52 Protein ◽  
New Biomarkers

Understanding basic molecular mechanisms underlying the biology of cancer cells is of outmost importance for identification of novel therapeutic targets and biomarkers for patient stratification and better therapy selection. One of these mechanisms, the response to replication stress, fuels cancer genomic instability. It is also an Achille’s heel of cancer. Thus, identification of pathways used by the cancer cells to respond to replication-stress may assist in the identification of new biomarkers and discovery of new therapeutic targets. Alternative mechanisms that act at perturbed DNA replication forks and involve fork degradation by nucleases emerged as crucial for sensitivity of cancer cells to chemotherapeutics agents inducing replication stress. Despite its important role in homologous recombination and recombinational repair of DNA double strand breaks in lower eukaryotes, RAD52 protein has been considered dispensable in human cells and the full range of its cellular functions remained unclear. Very recently, however, human RAD52 emerged as an important player in multiple aspects of replication fork metabolism under physiological and pathological conditions. In this review, we describe recent advances on RAD52’s key functions at stalled or collapsed DNA replication forks, in particular, the unexpected role of RAD52 as a gatekeeper, which prevents unscheduled processing of DNA. Last, we will discuss how these functions can be exploited using specific inhibitors in targeted therapy or for an informed therapy selection.

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