scholarly journals CtIP-dependent DNA resection is required for DNA damage checkpoint maintenance but not initiation

2012 ◽  
Vol 197 (7) ◽  
pp. 869-876 ◽  
Author(s):  
Arne Nedergaard Kousholt ◽  
Kasper Fugger ◽  
Saskia Hoffmann ◽  
Brian D. Larsen ◽  
Tobias Menzel ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Progression ◽  
Dna Lesions ◽  
Cell Cycle Checkpoint ◽  
Dna Breaks ◽  
Checkpoint Signaling ◽  
Cycle Checkpoint ◽  
Dna End Resection ◽  
End Resection

To prevent accumulation of mutations, cells respond to DNA lesions by blocking cell cycle progression and initiating DNA repair. Homology-directed repair of DNA breaks requires CtIP-dependent resection of the DNA ends, which is thought to play a key role in activation of ATR (ataxia telangiectasia mutated and Rad3 related) and CHK1 kinases to induce the cell cycle checkpoint. In this paper, we show that CHK1 was rapidly and robustly activated before detectable end resection. Moreover, we show that the key resection factor CtIP was dispensable for initial ATR–CHK1 activation after DNA damage by camptothecin and ionizing radiation. In contrast, we find that DNA end resection was critically required for sustained ATR–CHK1 checkpoint signaling and for maintaining both the intra–S- and G2-phase checkpoints. Consequently, resection-deficient cells entered mitosis with persistent DNA damage. In conclusion, we have uncovered a temporal program of checkpoint activation, where CtIP-dependent DNA end resection is required for sustained checkpoint signaling.

scholarly journals Acceleration or Brakes: Which Is Rational for Cell Cycle-Targeting Neuroblastoma Therapy?

Biomolecules ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 750
Author(s):  
Kiyohiro Ando ◽  
Akira Nakagawara
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Progression ◽  
Parp Inhibitors ◽  
Cell Cycle Checkpoint ◽  
Mitotic Catastrophe ◽  
Malignant Neoplasms ◽  
Checkpoint Kinases ◽  
Molecular Features ◽  
Cycle Checkpoint

Unrestrained proliferation is a common feature of malignant neoplasms. Targeting the cell cycle is a therapeutic strategy to prevent unlimited cell division. Recently developed rationales for these selective inhibitors can be subdivided into two categories with antithetical functionality. One applies a “brake” to the cell cycle to halt cell proliferation, such as with inhibitors of cell cycle kinases. The other “accelerates” the cell cycle to initiate replication/mitotic catastrophe, such as with inhibitors of cell cycle checkpoint kinases. The fate of cell cycle progression or arrest is tightly regulated by the presence of tolerable or excessive DNA damage, respectively. This suggests that there is compatibility between inhibitors of DNA repair kinases, such as PARP inhibitors, and inhibitors of cell cycle checkpoint kinases. In the present review, we explore alterations to the cell cycle that are concomitant with altered DNA damage repair machinery in unfavorable neuroblastomas, with respect to their unique genomic and molecular features. We highlight the vulnerabilities of these alterations that are attributable to the features of each. Based on the assessment, we offer possible therapeutic approaches for personalized medicine, which are seemingly antithetical, but both are promising strategies for targeting the altered cell cycle in unfavorable neuroblastomas.

scholarly journals Undamaged DNA Transmits and Enhances DNA Damage Checkpoint Signals in Early Embryos

2007 ◽  
Vol 27 (19) ◽  
pp. 6852-6862 ◽  
Author(s):  
Aimin Peng ◽  
Andrea L. Lewellyn ◽  
James L. Maller
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Nuclear Dna ◽  
Cell Cycle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Checkpoint Response ◽  
Egg Extracts ◽  
Cycle Checkpoint ◽  
Damaged Dna

ABSTRACT In Xenopus laevis embryos, the midblastula transition (MBT) at the 12th cell division marks initiation of critical developmental events, including zygotic transcription and the abrupt inclusion of gap phases into the cell cycle. Interestingly, although an ionizing radiation-induced checkpoint response is absent in pre-MBT embryos, introduction of a threshold amount of undamaged plasmid or sperm DNA allows a DNA damage checkpoint response to be activated. We show here that undamaged threshold DNA directly participates in checkpoint signaling, as judged by several dynamic changes, including H2AX phosphorylation, ATM phosphorylation and loading onto chromatin, and Chk1/Chk2 phosphorylation and release from nuclear DNA. These responses on physically separate threshold DNA require γ-H2AX and are triggered by an ATM-dependent soluble signal initiated by damaged DNA. The signal persists in egg extracts even after damaged DNA is removed from the system, indicating that the absence of damaged DNA is not sufficient to end the checkpoint response. The results identify a novel mechanism by which undamaged DNA enhances checkpoint signaling and provide an example of how the transition to cell cycle checkpoint activation during development is accomplished by maternally programmed increases in the DNA-to-cytoplasm ratio.

Spermidine/spermine N1-acetyltransferase overexpression in kidney epithelial cells disrupts polyamine homeostasis, leads to DNA damage, and causes G2 arrest

2007 ◽  
Vol 292 (3) ◽  
pp. C1204-C1215 ◽  
Author(s):  
Kamyar Zahedi ◽  
John J. Bissler ◽  
Zhaohui Wang ◽  
Anuradha Josyula ◽  
Lu Lu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Dna Damage ◽  
Dna Repair ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Dna Lesions ◽  
Cell Cycle Checkpoint ◽  
Cycle Checkpoint

Expression of spermidine/spermine N1-acetyltransferase (SSAT) increases in kidneys subjected to ischemia-reperfusion injury (IRI). Increased expression of SSAT in vitro leads to alterations in cellular polyamine content, depletion of cofactors and precursors of polyamine synthesis, and reduced cell proliferation. In our model system, a >28-fold increase in SSAT levels in HEK-293 cells leads to depletion of polyamines and elevation in the enzymatic activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase, suggestive of a compensatory reaction to increased polyamine catabolism. Increased expression of SSAT also led to DNA damage and G2 arrest. The increased DNA damage was primarily due to the depletion of polyamines. Other factors such as increased production of H2O2 due to polyamine oxidase activity may play a secondary role in the induction of DNA lesions. In response to DNA damage the ATM/ATR → Chk1/2 DNA repair and cell cycle checkpoint pathways were activated, mediating the G2 arrest in SSAT-expressing cells. In addition, the activation of ERK1 and ERK2, which play integral roles in the G2/M transition, is impaired in cells expressing SSAT. These results indicate that the disruption of polyamine homeostasis due to enhanced SSAT activity leads to DNA damage and reduced cell proliferation via activation of DNA repair and cell cycle checkpoint and disruption of Raf → MEK → ERK pathways. We propose that in kidneys subjected to IRI, one mechanism through which increased expression of SSAT may cause cellular injury and organ damage is through induction of DNA damage and the disruption of cell cycle.

scholarly journals Predisposition to cancer and radiosensitivity

2000 ◽  
Vol 23 (4) ◽  
pp. 1101-1105 ◽  
Author(s):  
P. Pichierri ◽  
A. Franchitto ◽  
F. Palitti
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Interindividual Variability ◽  
Peripheral Blood Lymphocytes ◽  
Dna Lesions ◽  
Cell Cycle Checkpoint ◽  
Large Variability ◽  
New Approach ◽  
Cycle Checkpoint ◽  
Homogeneous Cell

Many cancer-prone diseases have been shown to be radiosensitive. The radiosensitivity has been attributed to pitfalls in the mechanisms of repair of induced DNA lesions or to an impaired cell cycle checkpoint response. Although discrepancies exist in the results obtained by various authors on the radiosensitivity of individuals affected by the same disease, these can be attributed to the large variability observed already in the response to radiation of normal individuals. To date three test are commonly used to assess radiosensitivity in human cells: survival, micronucleous and G2 chromosomal assay. The three tests may be performed using either fibroblasts or peripheral blood lymphocytes and all the three tests share large interindividual variability. In this regard a new approach to the G2 chromosomal assay which takes into account the eventual differences in cell cycle progression among individuals has been developed. This new approach is based on the analysis of G2 homogeneous cell populations. Cells irradiated are immediately challenged with medium containing bromodeoxyuridine (BrdUrd). Then cells are sampled at different post-irradiation times and BrdUrd incorporation detected on metaphases spread and the scoring is done only at time points showing similar incidence of labelled cells among the different donors. Using this approach it has been possible to reduce the interindividual variability of the G2 chromosomal assay.

scholarly journals ZGRF1 promotes end resection of DNA homologous recombination via forming complex with BRCA1/EXO1

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Shuang Yan ◽  
Man Song ◽  
Jie Ping ◽  
Shu-ting Lai ◽  
Xiao-yu Cao ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Homologous Recombination ◽  
Mammalian Cells ◽  
Cell Cycle Checkpoint ◽  
Dependent Manner ◽  
Dna Breaks ◽  
M Cell ◽  
End Resection

AbstractTo maintain genomic stability, the mammalian cells has evolved a coordinated response to DNA damage, including activation of DNA repair and cell cycle checkpoint processes. Exonuclease 1 (EXO1)-dependent excision of DNA ends is important for the initiation of homologous recombination (HR) repair of DNA breaks, which is thought to play a key role in activating the ATR-CHK1 pathway to induce G2/M cell cycle arrest. But the mechanism is still not fully understood. Here, we report that ZGRF1 forms complexes with EXO1 as well as other repair proteins and promotes DNA repair through HR. ZGRF1 is recruited to DNA damage sites in a MDC1-RNF8-BRCA1 dependent manner. Furthermore, ZGRF1 is important for the recruitment of RPA2 to DNA damage sites and the following ATR-CHK1 mediated G2/M checkpoint in response to irradiation. ZGRF1 null cells show increased sensitivity to many DNA-damaging agents, especially PARPi and irradiation. Collectively,our findings identify ZGRF1 as a novel regulator of DNA end resection and G2/M checkpoint. ZGRF1 is a potential target of radiation and PARPi cancer therapy.

scholarly journals Sensitivity of cells to ATR and CHK1 inhibitors requires hyperactivation of CDK2 rather than endogenous replication stress or ATM dysfunction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jennifer P. Ditano ◽  
Katelyn L. Donahue ◽  
Laura J. Tafe ◽  
Charlotte F. McCleery ◽  
Alan Eastman
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Lines ◽  
Cell Cycle Progression ◽  
Single Agent ◽  
Replication Stress ◽  
Cell Cycle Checkpoint ◽  
High Threshold ◽  
Cycle Checkpoint ◽  
Atm Signaling

AbstractDNA damage activates cell cycle checkpoint proteins ATR and CHK1 to arrest cell cycle progression, providing time for repair and recovery. Consequently, inhibitors of ATR (ATRi) and CHK1 (CHK1i) enhance damage-induced cell death. Intriguingly, both CHK1i and ATRi alone elicit cytotoxicity in some cell lines. Sensitivity has been attributed to endogenous replications stress, but many more cell lines are sensitive to ATRi than CHK1i. Endogenous activation of the DNA damage response also did not correlate with drug sensitivity. Sensitivity correlated with the appearance of γH2AX, a marker of DNA damage, but without phosphorylation of mitotic markers, contradicting suggestions that the damage is due to premature mitosis. Sensitivity to ATRi has been associated with ATM mutations, but dysfunction in ATM signaling did not correlate with sensitivity. CHK1i and ATRi circumvent replication stress by reactivating stalled replicons, a process requiring a low threshold activity of CDK2. In contrast, γH2AX induced by single agent ATRi and CHK1i requires a high threshold activity CDK2. Hence, phosphorylation of different CDK2 substrates is required for cytotoxicity induced by replication stress plus ATRi/CHK1i as compared to their single agent activity. In summary, sensitivity to ATRi and CHK1i as single agents is elicited by premature hyper-activation of CDK2.

scholarly journals DHX9-dependent recruitment of BRCA1 to RNA promotes DNA end resection in homologous recombination

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Prasun Chakraborty ◽  
Kevin Hiom
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Rna Polymerase Ii ◽  
Critical Role ◽  
Dna Breaks ◽  
Double Stranded Dna ◽  
Recombination Repair ◽  
Dna End Resection ◽  
End Resection ◽  
Rna Polymerase Ii Transcription

AbstractDouble stranded DNA Breaks (DSB) that occur in highly transcribed regions of the genome are preferentially repaired by homologous recombination repair (HR). However, the mechanisms that link transcription with HR are unknown. Here we identify a critical role for DHX9, a RNA helicase involved in the processing of pre-mRNA during transcription, in the initiation of HR. Cells that are deficient in DHX9 are impaired in the recruitment of RPA and RAD51 to sites of DNA damage and fail to repair DSB by HR. Consequently, these cells are hypersensitive to treatment with agents such as camptothecin and Olaparib that block transcription and generate DSB that specifically require HR for their repair. We show that DHX9 plays a critical role in HR by promoting the recruitment of BRCA1 to RNA as part of the RNA Polymerase II transcription complex, where it facilitates the resection of DSB. Moreover, defects in DHX9 also lead to impaired ATR-mediated damage signalling and an inability to restart DNA replication at camptothecin-induced DSB. Together, our data reveal a previously unknown role for DHX9 in the DNA Damage Response that provides a critical link between RNA, RNA Pol II and the repair of DNA damage by homologous recombination.

scholarly journals The Interactions of DNA Repair, Telomere Homeostasis, and p53 Mutational Status in Solid Cancers: Risk, Prognosis, and Prediction

Cancers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 479
Author(s):  
Pavel Vodicka ◽  
Ladislav Andera ◽  
Alena Opattova ◽  
Ludmila Vodickova
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Repair ◽  
Dna Lesions ◽  
Cell Cycle Checkpoint ◽  
Solid Cancer ◽  
Genomic Integrity ◽  
Repair Capacity ◽  
Mutational Status ◽  
Telomere Homeostasis

The disruption of genomic integrity due to the accumulation of various kinds of DNA damage, deficient DNA repair capacity, and telomere shortening constitute the hallmarks of malignant diseases. DNA damage response (DDR) is a signaling network to process DNA damage with importance for both cancer development and chemotherapy outcome. DDR represents the complex events that detect DNA lesions and activate signaling networks (cell cycle checkpoint induction, DNA repair, and induction of cell death). TP53, the guardian of the genome, governs the cell response, resulting in cell cycle arrest, DNA damage repair, apoptosis, and senescence. The mutational status of TP53 has an impact on DDR, and somatic mutations in this gene represent one of the critical events in human carcinogenesis. Telomere dysfunction in cells that lack p53-mediated surveillance of genomic integrity along with the involvement of DNA repair in telomeric DNA regions leads to genomic instability. While the role of individual players (DDR, telomere homeostasis, and TP53) in human cancers has attracted attention for some time, there is insufficient understanding of the interactions between these pathways. Since solid cancer is a complex and multifactorial disease with considerable inter- and intra-tumor heterogeneity, we mainly dedicated this review to the interactions of DNA repair, telomere homeostasis, and TP53 mutational status, in relation to (a) cancer risk, (b) cancer progression, and (c) cancer therapy.

scholarly journals A DNA-Damage-Induced Cell Cycle Checkpoint in Arabidopsis

Genetics ◽  
2003 ◽  
Vol 164 (1) ◽  
pp. 323-334
Author(s):  
S B Preuss ◽  
A B Britt
Keyword(s):  
Cell Cycle ◽  
Gamma Radiation ◽  
Cell Cycle Progression ◽  
Cell Cycle Checkpoint ◽  
Phase Cell ◽  
Cycle Arrest ◽  
Cycle Checkpoint ◽  
Radiation Induced ◽  
High Doses ◽  
Regulation Of Cell Cycle

Abstract Although it is well established that plant seeds treated with high doses of gamma radiation arrest development as seedlings, the cause of this arrest is unknown. The uvh1 mutant of Arabidopsis is defective in a homolog of the human repair endonuclease XPF, and uvh1 mutants are sensitive to both the toxic effects of UV and the cytostatic effects of gamma radiation. Here we find that gamma irradiation of uvh1 plants specifically triggers a G2-phase cell cycle arrest. Mutants, termed suppressor of gamma (sog), that suppress this radiation-induced arrest and proceed through the cell cycle unimpeded were recovered in the uvh1 background; the resulting irradiated plants are genetically unstable. The sog mutations fall into two complementation groups. They are second-site suppressors of the uvh1 mutant's sensitivity to gamma radiation but do not affect the susceptibility of the plant to UV radiation. In addition to rendering the plants resistant to the growth inhibitory effects of gamma radiation, the sog1 mutation affects the proper development of the pollen tetrad, suggesting that SOG1 might also play a role in the regulation of cell cycle progression during meiosis.

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