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.

scholarly journals Critical Role for Mouse Hus1 in an S-Phase DNA Damage Cell Cycle Checkpoint

2003 ◽  
Vol 23 (3) ◽  
pp. 791-803 ◽  
Author(s):  
Robert S. Weiss ◽  
Philip Leder ◽  
Cyrus Vaziri
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Synthesis ◽  
Critical Role ◽  
S Phase ◽  
Cell Cycle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Null Mouse ◽  
Cycle Checkpoint ◽  
S Phase Checkpoint

ABSTRACT Mouse Hus1 encodes an evolutionarily conserved DNA damage response protein. In this study we examined how targeted deletion of Hus1 affects cell cycle checkpoint responses to genotoxic stress. Unlike hus1− fission yeast (Schizosaccharomyces pombe) cells, which are defective for the G2/M DNA damage checkpoint, Hus1-null mouse cells did not inappropriately enter mitosis following genotoxin treatment. However, Hus1-deficient cells displayed a striking S-phase DNA damage checkpoint defect. Whereas wild-type cells transiently repressed DNA replication in response to benzo(a)pyrene dihydrodiol epoxide (BPDE), a genotoxin that causes bulky DNA adducts, Hus1-null cells maintained relatively high levels of DNA synthesis following treatment with this agent. However, when treated with DNA strand break-inducing agents such as ionizing radiation (IR), Hus1-deficient cells showed intact S-phase checkpoint responses. Conversely, checkpoint-mediated inhibition of DNA synthesis in response to BPDE did not require NBS1, a component of the IR-responsive S-phase checkpoint pathway. Taken together, these results demonstrate that Hus1 is required specifically for one of two separable mammalian checkpoint pathways that respond to distinct forms of genome damage during S phase.

scholarly journals DNA replication is required for the checkpoint response to damaged DNA in Xenopus egg extracts

2002 ◽  
Vol 158 (5) ◽  
pp. 863-872 ◽  
Author(s):  
Matthew P. Stokes ◽  
Ruth Van Hatten ◽  
Howard D. Lindsay ◽  
W. Matthew Michael
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Alkylating Agents ◽  
Dna Damage Checkpoint ◽  
Checkpoint Activation ◽  
Checkpoint Response ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
Damaged Dna

Alkylating agents, such as methyl methanesulfonate (MMS), damage DNA and activate the DNA damage checkpoint. Although many of the checkpoint proteins that transduce damage signals have been identified and characterized, the mechanism that senses the damage and activates the checkpoint is not yet understood. To address this issue for alkylation damage, we have reconstituted the checkpoint response to MMS in Xenopus egg extracts. Using four different indicators for checkpoint activation (delay on entrance into mitosis, slowing of DNA replication, phosphorylation of the Chk1 protein, and physical association of the Rad17 checkpoint protein with damaged DNA), we report that MMS-induced checkpoint activation is dependent upon entrance into S phase. Additionally, we show that the replication of damaged double-stranded DNA, and not replication of damaged single-stranded DNA, is the molecular event that activates the checkpoint. Therefore, these data provide direct evidence that replication forks are an obligate intermediate in the activation of the DNA damage checkpoint.

scholarly journals Artemis Is a Phosphorylation Target of ATM and ATR and Is Involved in the G2/M DNA Damage Checkpoint Response

2004 ◽  
Vol 24 (20) ◽  
pp. 9207-9220 ◽  
Author(s):  
Xiaoshan Zhang ◽  
Janice Succi ◽  
Zhaohui Feng ◽  
Sheela Prithivirajsingh ◽  
Michael D. Story ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Severe Combined Immunodeficiency ◽  
Cell Cycle Checkpoint ◽  
End Joining ◽  
M Cell ◽  
Checkpoint Kinase ◽  
Checkpoint Response ◽  
Cell Extracts ◽  
Cycle Checkpoint

ABSTRACT Mutations in Artemis in both humans and mice result in severe combined immunodeficiency due to a defect in V(D)J recombination. In addition, Artemis mutants are radiosensitive and chromosomally unstable, which has been attributed to a defect in nonhomologous end joining (NHEJ). We show here, however, that Artemis-depleted cell extracts are not defective in NHEJ and that Artemis-deficient cells have normal repair kinetics of double-strand breaks after exposure to ionizing radiation (IR). Artemis is shown, however, to interact with known cell cycle checkpoint proteins and to be a phosphorylation target of the checkpoint kinase ATM or ATR after exposure of cells to IR or UV irradiation, respectively. Consistent with these findings, our results also show that Artemis is required for the maintenance of a normal DNA damage-induced G2/M cell cycle arrest. Artemis does not appear, however, to act either upstream or downstream of checkpoint kinase Chk1 or Chk2. These results define Artemis as having a checkpoint function and suggest that the radiosensitivity and chromosomal instability of Artemis-deficient cells may be due to defects in cell cycle responses after DNA damage.

Development of Cell Cycle Active Drugs for the Treatment of Gastrointestinal Cancers: A New Approach to Cancer Therapy

2005 ◽  
Vol 23 (20) ◽  
pp. 4499-4508 ◽  
Author(s):  
Gary K. Schwartz
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Arrest ◽  
Tumor Cells ◽  
Genotoxic Stress ◽  
Cell Cycle Checkpoint ◽  
Gastrointestinal Cancers ◽  
Cycle Arrest ◽  
Cycle Checkpoint ◽  
Damaged Dna

The cell cycle represents a series of tightly integrated events that allow the cell to grow and proliferate. An essential part of the cell cycle machinery is the cyclin-dependent kinases (CDKs). When activated, the CDKs provide a means for the cell to move from one phase of the cell cycle to the next (G1 to S or G2 to M). The cell cycle serves to protect the cell from genotoxic stress. In the setting of DNA damage, the CDKs are inhibited and the cell undergoes cell-cycle arrest. This provides the cell the opportunity to repair its own damaged DNA before it resumes cell proliferation. If a cell continues to cycle with its damaged DNA intact, the apoptotic machinery is triggered and the cell will undergo apoptosis. In essence, cell cycle arrest at these critical checkpoints represents a survival mechanism, which provides the tumor cell the opportunity to escape the effects of lethal DNA damage induced by chemotherapy. Over the past several years, a series of new targeted agents has been developed that promote apoptosis of DNA damaged tumor cells either during cell cycle arrest or following premature cell cycle checkpoint exit, such that tumor cells re-enter the cell cycle before DNA repair is complete. An understanding of the cell cycle and its relationship to p53 are critical for the successful clinical development of these agents for the treatment of patients with gastrointestinal cancers.

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 PEA15 Regulates the DNA Damage-Induced Cell Cycle Checkpoint and Oncogene-Directed Transformation

2014 ◽  
Vol 34 (12) ◽  
pp. 2264-2282 ◽  
Author(s):  
A. Nagarajan ◽  
S. K. Dogra ◽  
A. Y. Liu ◽  
M. R. Green ◽  
N. Wajapeyee
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Checkpoint ◽  
Cycle Checkpoint ◽  
Directed Transformation

scholarly journals Abnormal Micronuclear Telomeres Lead to an Unusual Cell Cycle Checkpoint and Defects in Tetrahymena Oral Morphogenesis

2008 ◽  
Vol 7 (10) ◽  
pp. 1712-1723 ◽  
Author(s):  
Karen E. Kirk ◽  
Christina Christ ◽  
Jennifer M. McGuire ◽  
Arun G. Paul ◽  
Mithaq Vahedi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Cell Cycle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Telomeric Dna ◽  
Spindle Apparatus ◽  
Cycle Checkpoint

ABSTRACT Telomere mutants have been well studied with respect to telomerase and the role of telomere binding proteins, but they have not been used to explore how a downstream morphogenic event is related to the mutated telomeric DNA. We report that alterations at the telomeres can have profound consequences on organellar morphogenesis. Specifically, a telomerase RNA mutation termed ter1-43AA results in the loss of germ line micronuclear telomeres in the binucleate protozoan Tetrahymena thermophila. These cells also display a micronuclear mitotic arrest, characterized by an extreme delay in anaphase with an elongated, condensed chromatin and a mitotic spindle apparatus. This anaphase defect suggests telomere fusions and consequently a spindle rather than a DNA damage checkpoint. Most surprisingly, these mutants exhibit unique, dramatic defects in the formation of the cell's oral apparatus. We suggest that micronuclear telomere loss leads to a “dynamic pause” in the program of cortical development, which may reveal an unusual cell cycle checkpoint.

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