Carcinogenic bacterial pathogen Helicobacter pylori triggers DNA double-strand breaks and a DNA damage response in its host cells

Abstract Background: Toxoplasma gondii (T. gondii) is an obligate parasite of the warm-blooded animals with a worldwide distribution. Once having entered a host cell, it manipulates host’s DNA damage response that is yet to be investigated. The objectives of the present study were three-fold: 1) to assess DNA damages in T. gondii-infected cells in vitro; 2) to ascertain sources causing DNA damage in T. gondii-infected cells; 3) to investigate activation of DNA damage response during T. gondii infection.Methods: HeLa, Vero and HEK293 cells were infected with T. gondii at multiplicity of infection (MOI) of 10:1. Infected cells at 10 h, 20 h or 30 h post infection were analyzed for a DNA double strand breaks (DSBs) biomarker γH2AX using Western blot and immunofluorescence assay. Reactive oxygen species (ROS) levels were examined using 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA), and the impact of ROS on DNA damage was assessed by inhibition using a ROS inhibitor N-acetylcysteine (NAC). Lastly, DNA damage response in these T. gondii-infected cells was evaluated by detecting the expression of active form of ataxia telangiectasia mutated/checkpoint kinase 2 (ATM/CHK2) with Western blot. Results: Compared to uninfected cells, γH2AX expression in the infected HeLa cells at 10 h, 20 h, and 30 h was increased over time during T. gondii infection. NAC treatment reduced ROS level in host cells and significantly decreased the expression of γH2AX. Expression of phosphorylated ATM/CHK2 was elevated in T. gondii-infected cells.Conclusion: T. gondii infection triggered DNA DSBs with ROS as a major player in host cells in vitro. It also concomitantly activated DNA damage response pathway ATM/CHK2. T. gondii struggles a balance between survival and apoptosis of its host cells for the benefit of its own survival.

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Sae2 antagonizes Rad9 accumulation at DNA double-strand breaks to attenuate checkpoint signaling and facilitate end resection

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1816539115 ◽

2018 ◽

Vol 115 (51) ◽

pp. E11961-E11969 ◽

Cited By ~ 14

Author(s):

Tai-Yuan Yu ◽

Michael T. Kimble ◽

Lorraine S. Symington

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Inhibitory Effects ◽

Checkpoint Signaling ◽

Synthetic Lethal ◽

Strand Breaks ◽

Damage Response ◽

End Resection

The Mre11-Rad50-Xrs2NBS1 complex plays important roles in the DNA damage response by activating the Tel1ATM kinase and catalyzing 5′–3′ resection at DNA double-strand breaks (DSBs). To initiate resection, Mre11 endonuclease nicks the 5′ strands at DSB ends in a reaction stimulated by Sae2CtIP. Accordingly, Mre11-nuclease deficient (mre11-nd) and sae2Δ mutants are expected to exhibit similar phenotypes; however, we found several notable differences. First, sae2Δ cells exhibit greater sensitivity to genotoxins than mre11-nd cells. Second, sae2Δ is synthetic lethal with sgs1Δ, whereas the mre11-nd sgs1Δ mutant is viable. Third, Sae2 attenuates the Tel1-Rad53CHK2 checkpoint and antagonizes Rad953BP1 accumulation at DSBs independent of Mre11 nuclease. We show that Sae2 competes with other Tel1 substrates, thus reducing Rad9 binding to chromatin and to Rad53. We suggest that persistent Sae2 binding at DSBs in the mre11-nd mutant counteracts the inhibitory effects of Rad9 and Rad53 on Exo1 and Dna2-Sgs1–mediated resection, accounting for the different phenotypes conferred by mre11-nd and sae2Δ mutations. Collectively, these data show a resection initiation independent role for Sae2 at DSBs by modulating the DNA damage checkpoint.

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Recent advances in the nucleolar responses to DNA double-strand breaks

Nucleic Acids Research ◽

10.1093/nar/gkaa713 ◽

2020 ◽

Vol 48 (17) ◽

pp. 9449-9461

Author(s):

Lea Milling Korsholm ◽

Zita Gál ◽

Blanca Nieto ◽

Oliver Quevedo ◽

Stavroula Boukoura ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Dna Damage Response ◽

Ribosomal Dna ◽

Repetitive Sequences ◽

Dna Lesions ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Damage Response

Abstract DNA damage poses a serious threat to human health and cells therefore continuously monitor and repair DNA lesions across the genome. Ribosomal DNA is a genomic domain that represents a particular challenge due to repetitive sequences, high transcriptional activity and its localization in the nucleolus, where the accessibility of DNA repair factors is limited. Recent discoveries have significantly extended our understanding of how cells respond to DNA double-strand breaks (DSBs) in the nucleolus, and new kinases and multiple down-stream targets have been identified. Restructuring of the nucleolus can occur as a consequence of DSBs and new data point to an active regulation of this process, challenging previous views. Furthermore, new insights into coordination of cell cycle phases and ribosomal DNA repair argue against existing concepts. In addition, the importance of nucleolar-DNA damage response (n-DDR) mechanisms for maintenance of genome stability and the potential of such factors as anti-cancer targets is becoming apparent. This review will provide a detailed discussion of recent findings and their implications for our understanding of the n-DDR. The n-DDR shares features with the DNA damage response (DDR) elsewhere in the genome but is also emerging as an independent response unique to ribosomal DNA and the nucleolus.

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DNA double-strand breaks in the Toxoplasma gondii-infected cells by the action of reactive oxygen species

Parasites & Vectors ◽

10.1186/s13071-020-04324-7 ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Haohan Zhuang ◽

Chaoqun Yao ◽

Xianfeng Zhao ◽

Xueqiu Chen ◽

Yimin Yang ◽

...

Keyword(s):

Dna Damage ◽

Toxoplasma Gondii ◽

Double Strand Breaks ◽

Host Cells ◽

Oxygen Species ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Damage Response ◽

Infected Cells

Abstract Background Toxoplasma gondii is an obligate parasite of all warm-blooded animals around the globe. Once infecting a cell, it manipulates the host’s DNA damage response that is yet to be elucidated. The objectives of the present study were three-fold: (i) to assess DNA damages in T. gondii-infected cells in vitro; (ii) to ascertain causes of DNA damage in T. gondii-infected cells; and (iii) to investigate activation of DNA damage responses during T. gondii infection. Methods HeLa, Vero and HEK293 cells were infected with T. gondii at a multiplicity of infection (MOI) of 10:1. Infected cells were analyzed for a biomarker of DNA double-strand breaks (DSBs) γH2AX at 10 h, 20 h or 30 h post-infection using both western blot and immunofluorescence assay. Reactive oxygen species (ROS) levels were measured using 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA), and ROS-induced DNA damage was inhibited by a ROS inhibitor N-acetylcysteine (NAC). Lastly, DNA damage responses were evaluated by detecting the active form of ataxia telangiectasia mutated/checkpoint kinase 2 (ATM/CHK2) by western blot. Results γH2AX levels in the infected HeLa cells were significantly increased over time during T. gondii infection compared to uninfected cells. NAC treatment greatly reduced ROS and concomitantly diminished γH2AX in host cells. The phosphorylated ATM/CHK2 were elevated in T. gondii-infected cells. Conclusions Toxoplasma gondii infection triggered DNA DSBs with ROS as a major player in host cells in vitro. It also activated DNA damage response pathway ATM/CHK2. Toxoplasma gondii manages to keep a balance between survival and apoptosis of its host cells for the benefit of its own survival.

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Heterochromatin and the DNA damage response: the need to relaxThis paper is one of a selection of papers in a Special Issue entitled 31st Annual International Asilomar Chromatin and Chromosomes Conference, and has undergone the Journal’s usual peer review process.

Biochemistry and Cell Biology ◽

10.1139/o10-113 ◽

2011 ◽

Vol 89 (1) ◽

pp. 45-60 ◽

Cited By ~ 72

Author(s):

Kendra L. Cann ◽

Graham Dellaire

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Chromatin Structure ◽

Peer Review Process ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Atm Kinase ◽

Strand Breaks ◽

Damage Response ◽

Chromosomal Mutations

Higher order chromatin structure has an impact on all nuclear functions, including the DNA damage response. Over the past several years, it has become increasingly clear that heterochromatin and euchromatin represent separate entities with respect to both damage sensitivity and repair. The chromatin compaction present in heterochromatin helps to protect this DNA from damage; however, when lesions do occur, the compaction restricts the ability of DNA damage response proteins to access the site, as evidenced by its ability to block the expansion of H2AX phosphorylation. As such, DNA damage in heterochromatin is refractory to repair, which requires the surrounding chromatin structure to be decondensed. In the case of DNA double-strand breaks, this relaxation is at least partially mediated by the ATM kinase phosphorylating and inhibiting the function of the transcriptional repressor KAP1. This review will focus on the functions of KAP1 and other proteins involved in the maintenance or restriction of heterochromatin, including HP1 and TIP60, in the DNA damage response. As heterochromatin is important for maintaining genomic stability, cells must maintain a delicate balance between allowing repair factors access to these regions and ensuring that these regions retain their organization to prevent increased DNA damage and chromosomal mutations.

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Real Estate in the DNA Damage Response: Ubiquitin and SUMO Ligases Home in on DNA Double-Strand Breaks

Frontiers in Genetics ◽

10.3389/fgene.2016.00058 ◽

2016 ◽

Vol 7 ◽

Cited By ~ 3

Author(s):

Nico P. Dantuma ◽

Annika Pfeiffer

Keyword(s):

Dna Damage ◽

Real Estate ◽

Dna Damage Response ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Damage Response

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Nuclear phosphorylated Dicer processes double-stranded RNA in response to DNA damage

The Journal of Cell Biology ◽

10.1083/jcb.201612131 ◽

2017 ◽

Vol 216 (8) ◽

pp. 2373-2389 ◽

Cited By ~ 32

Author(s):

Kaspar Burger ◽

Margarita Schlackow ◽

Martin Potts ◽

Svenja Hester ◽

Shabaz Mohammed ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Noncoding Rna ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Double Stranded Rna ◽

Strand Breaks ◽

Small Noncoding Rna ◽

Damage Response ◽

Carboxy Terminal

The endoribonuclease Dicer is a key component of the human RNA interference pathway and is known for its role in cytoplasmic microRNA production. Recent findings suggest that noncanonical Dicer generates small noncoding RNA to mediate the DNA damage response (DDR). Here, we show that human Dicer is phosphorylated in the platform–Piwi/Argonaute/Zwille–connector helix cassette (S1016) upon induction of DNA damage. Phosphorylated Dicer (p-Dicer) accumulates in the nucleus and is recruited to DNA double-strand breaks. We further demonstrate that turnover of damage-induced nuclear, double-stranded (ds) RNA requires additional phosphorylation of carboxy-terminal Dicer residues (S1728 and S1852). DNA damage-induced nuclear Dicer accumulation is conserved in mammals. Dicer depletion causes endogenous DNA damage and delays the DDR by impaired recruitment of repair factors MDC1 and 53BP1. Collectively, we place Dicer within the context of the DDR by demonstrating a DNA damage-inducible phosphoswitch that causes localized processing of nuclear dsRNA by p-Dicer to promote DNA repair.

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PARP activation regulates the RNA-binding protein NONO in the DNA damage response to DNA double-strand breaks

Nucleic Acids Research ◽

10.1093/nar/gks798 ◽

2012 ◽

Vol 40 (20) ◽

pp. 10287-10301 ◽

Cited By ~ 84

Author(s):

Jana Krietsch ◽

Marie-Christine Caron ◽

Jean-Philippe Gagné ◽

Chantal Ethier ◽

Julien Vignard ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Rna Binding ◽

Binding Protein ◽

Rna Binding Protein ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Parp Activation ◽

Strand Breaks ◽

Damage Response

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ATM-dependent formation of a novel chromatin compartment regulates the Response to DNA Double Strand Breaks and the biogenesis of translocations

10.1101/2021.11.07.467654 ◽

2021 ◽

Author(s):

Coline Arnould ◽

Vincent Rocher ◽

Aldo S Bader ◽

Emma Lesage ◽

Nadine Puget ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Mammalian Cells ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Chromosome Architecture ◽

Cancer Genomes ◽

Damage Response ◽

Induced Changes

DNA Double-Strand Breaks (DSBs) repair is essential to safeguard genome integrity but the contribution of chromosome folding into this process remains elusive. Here we unveiled basic principles of chromosome dynamics upon DSBs in mammalian cells, controlled by key kinases from the DNA Damage Response. We report that ATM is responsible for the reinforcement of topologically associating domains (TAD) that experience a DSB. ATM further drives the formation of a new chromatin sub-compartment (″D″ compartment) upon clustering of damaged TADs decorated with γH2AX and 53BP1. ″D″ compartment formation mostly occurs in G1, is independent of cohesin and is enhanced upon DNA-PK pharmacological inhibition. Importantly, a subset of DNA damage responsive genes that are upregulated following DSBs also physically localize in the D sub-compartment and this ensures their optimal activation, providing a function for DSB clustering in activating the DNA Damage Response. However, these DSB-induced changes in genome organization also come at the expense of an increased translocations rate, which we could also detect on cancer genomes. Overall, our work provides a function for DSB-induced compartmentalization in orchestrating the DNA Damage Response and highlights the critical impact of chromosome architecture in genomic instability.

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