scholarly journals The Ulp2 SUMO Protease Is Required for Cell Division following Termination of the DNA Damage Checkpoint

2007 ◽  
Vol 27 (19) ◽  
pp. 6948-6961 ◽  
Author(s):  
David C. Schwartz ◽  
Rachael Felberbaum ◽  
Mark Hochstrasser
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Strand Break ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Sumo Protease ◽  
Checkpoint Pathway ◽  
Show Evidence ◽  
A Cell

ABSTRACT Eukaryotic genome integrity is maintained via a DNA damage checkpoint that recognizes DNA damage and halts the cell cycle at metaphase, allowing time for repair. Checkpoint signaling is eventually terminated so that the cell cycle can resume. How cells restart cell division following checkpoint termination is poorly understood. Here we show that the SUMO protease Ulp2 is required for resumption of cell division following DNA damage-induced arrest in Saccharomyces cerevisiae, although it is not required for DNA double-strand break repair. The Rad53 branch of the checkpoint pathway generates a signal countered by Ulp2 activity following DNA damage. Interestingly, unlike previously characterized adaptation mutants, ulp2Δ mutants do not show persistent Rad53 phosphorylation following DNA damage, suggesting checkpoint signaling has been terminated and no longer asserts an arrest in these cells. Using Cdc14 localization as a cell cycle indicator, we show that nearly half of cells lacking Ulp2 can escape a checkpoint-induced metaphase arrest despite their inability to divide again. Moreover, half of permanently arrested ulp2Δ cells show evidence of an aberrant mitotic spindle, suggesting that Ulp2 is required for proper spindle dynamics during cell cycle resumption following a DNA damage-induced cell cycle arrest.

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 Regulatory networks integrating cell cycle control with DNA damage checkpoints and double-strand break repair

2011 ◽  
Vol 366 (1584) ◽  
pp. 3562-3571 ◽  
Author(s):  
Petra Langerak ◽  
Paul Russell
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Regulatory Networks ◽  
Cell Cycle Progression ◽  
Cell Cycle Control ◽  
Strand Break ◽  
Dsb Repair ◽  
Cycle Progression ◽  
Non Homologous End Joining

Double-strand breaks (DSBs), arising from exposure to exogenous clastogens or as a by-product of endogenous cellular metabolism, pose grave threats to genome integrity. DSBs can sever whole chromosomes, leading to chromosomal instability, a hallmark of cancer. Healing broken DNA takes time, and it is therefore essential to temporarily halt cell division while DSB repair is underway. The seminal discovery of cyclin-dependent kinases as master regulators of the cell cycle unleashed a series of studies aimed at defining how the DNA damage response network delays cell division. These efforts culminated with the identification of Cdc25, the protein phosphatase that activates Cdc2/Cdk1, as a critical target of the checkpoint kinase Chk1. However, regulation works both ways, as recent studies have revealed that Cdc2 activity and cell cycle position determine whether DSBs are repaired by non-homologous end-joining or homologous recombination (HR). Central to this regulation are the proteins that initiate the processing of DNA ends for HR repair, Mre11–Rad50–Nbs1 protein complex and Ctp1/Sae2/CtIP, and the checkpoint kinases Tel1/ATM and Rad3/ATR. Here, we review recent findings and provide insight on how proteins that regulate cell cycle progression affect DSB repair, and, conversely how proteins that repair DSBs affect cell cycle progression.

scholarly journals Disruption of Mechanisms That Prevent Rereplication Triggers a DNA Damage Response

2005 ◽  
Vol 25 (15) ◽  
pp. 6707-6721 ◽  
Author(s):  
Vincent Archambault ◽  
Amy E. Ikui ◽  
Benjamin J. Drapkin ◽  
Frederick R. Cross
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Damage Response ◽  
Origin Recognition Complex ◽  
Strand Break ◽  
Minichromosome Maintenance ◽  
Damage Response ◽  
Similar Phenotype ◽  
A Cell ◽  
Prereplicative Complex

ABSTRACT Eukaryotes replicate DNA once and only once per cell cycle due to multiple, partially overlapping mechanisms efficiently preventing reinitiation. The consequences of reinitiation are unknown. Here we show that the induction of rereplication by mutations in components of the prereplicative complex (origin recognition complex [ORC], Cdc6, and minichromosome maintenance proteins) causes a cell cycle arrest with activated Rad53, a large-budded morphology, and an undivided nucleus. Combining a mutation disrupting the Clb5-Orc6 interaction (ORC6-rxl) and a mutation stabilizing Cdc6 (CDC6ΔNT) causes a cell cycle delay with a similar phenotype, although this background is only partially compromised for rereplication control and does not exhibit overreplication detectable by fluorescence-activated cell sorting. We conducted a systematic screen that identified genetic requirements for the viability of these cells. ORC6-rxl CDC6ΔNT cells depend heavily on genes required for the DNA damage response and for double-strand-break repair by homologous recombination. Our results implicate an Mre11-Mec1-dependent pathway in limiting the extent of rereplication.

scholarly journals The G(2) DNA damage checkpoint targets both Wee1 and Cdc25

2000 ◽  
Vol 113 (10) ◽  
pp. 1727-1736 ◽  
Author(s):  
J.M. Raleigh ◽  
M.J. O'Connell
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Progression ◽  
Dna Damage Checkpoint ◽  
Checkpoint Control ◽  
Down Regulation ◽  
Cycle Progression ◽  
Cycle Arrest ◽  
Checkpoint Pathway

The onset of mitosis is controlled by the cyclin dependent kinase Cdc2p. Cdc2p activity is controlled through the balance of phosphorylation and dephosphorylation of tyrosine-15 (Y15) by the Wee1p kinase and Cdc25p phosphatase. In the fission yeast Schizosaccharomyces pombe, detection of DNA damage in G(2) activates a checkpoint that prevents entry into mitosis through the maintenance of Y15 phosphorylation of Cdc2p, thus ensuring DNA repair precedes chromosome segregation. The protein kinase Chk1p is the endpoint of this checkpoint pathway. We have previously reported that overexpression of Chk1p causes a wee1(+)-dependent G(2) arrest, and this or irradiation leads to hyperphosphorylation of Wee1p. Moreover, Chk1p directly phosphorylates Wee1p in vitro. These data suggested that Wee1p is a key target of Chk1p action in checkpoint control. However, cells lacking wee1(+) are checkpoint proficient and sustained Chk1p overexpression arrests cell cycle progression independently of Wee1p. Therefore, up-regulation of Wee1p alone cannot enforce a checkpoint arrest. Chk1p can also phosphorylate Cdc25p in vitro. These phosphorylation events are thought to promote the interaction with 14–3-3 proteins the cytoplasmic retention of the 14–3-3/Cdc25p complexes. However, we show here that the G(2) DNA damage checkpoint is intact in cells that regulate mitotic entry independently of Cdc25p. Further, these cells are still sensitive to Chk1p-mediated arrest, and so down-regulation of Cdc25p is also insufficient to regulate checkpoint arrest. Conversely, inactivation of both wee1(+) and cdc25(+)abolishes checkpoint control. We also show that activation of the G(2) DNA damage checkpoint induces a transient increase in Wee1p levels. We conclude that the G(2) DNA damage checkpoint simultaneously signals via both up-regulation of Wee1p and down-regulation of Cdc25p, thus providing a double-lock mechanism to ensure cell cycle arrest and genomic stability.

scholarly journals Pds1p, an inhibitor of anaphase in budding yeast, plays a critical role in the APC and checkpoint pathway(s).

1996 ◽  
Vol 133 (1) ◽  
pp. 99-110 ◽  
Author(s):  
A Yamamoto ◽  
V Guacci ◽  
D Koshland
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Gamma Irradiation ◽  
Critical Role ◽  
Dna Damage Checkpoint ◽  
Microtubule Inhibitors ◽  
Cycle Arrest ◽  
Isolation And Characterization ◽  
Checkpoint Pathway ◽  
Cycle Regulation

We report the isolation and characterization of pds1 mutants in Saccharomyces cerevisiae. The initial pds1-1 allele was identified by its inviability after transient exposure to microtubule inhibitors and its precocious dissociation of sister chromatids in the presence of these microtubule inhibitors. These findings suggest that pds1 mutants might be defective in anaphase arrest that normally is imposed by a spindle-damage checkpoint. To further examine a role for Pds1p in anaphase arrest, we compared the cell cycle arrest of pds1 mutants and PDS1 cells after: (a) the inactivation of Cdc16p or Cdc23p, two proteins that are required for the degradation of mitotic cyclins and are putative components of the yeast anaphase promoting complex (APC); (b) the inactivation of Cdc20p, another protein implicated in the degradation of mitotic cyclins; and (c) the inactivation of Cdc13 protein or gamma irradiation, two circumstances that induce a DNA-damage checkpoint. Under all these conditions, anaphase is inhibited in PDS1 cells but not in pds1 mutants. From these results we suggest that Pds1 protein is an anaphase inhibitor in PDS1 cells but not in pds1 mutants. From these results we suggest that Pds1 protein is an anaphase inhibitor that plays a critical role in the control of anaphase by both APC and checkpoints. We also show that pds1 mutants exit mitosis and initiate new rounds of cell division after gamma irradiation and Cdc13p inactivation but no after nocodazole-treatment or inactivation of Cdc16p, Cdc20p or Cdc23p function. Therefore, in the DNA-damage checkpoint, Pds1p is required for the inhibition of cytokinesis and DNA replication as well as anaphase. The role of Pds1 protein in anaphase inhibition and general cell cycle regulation is discussed.

scholarly journals Adaptation to DNA damage as a bet-hedging mechanism in a fluctuating environment

2021 ◽  
Author(s):  
Pierre Roux ◽  
Delphine Salort ◽  
Zhou Xu
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Cell Survival ◽  
Genome Instability ◽  
Population Level ◽  
Signalling Pathway ◽  
Genome Integrity ◽  
Dna Damage Checkpoint ◽  
Bet Hedging

AbstractIn response to DNA damage, efficient repair is essential for cell survival and genome integrity. In eukaryotes, the DNA damage checkpoint is a signalling pathway that coordinates this response and arrests the cell cycle to provide time for repair. However, when repair fails or when the damage is not repairable, cells can eventually bypass the DNA damage checkpoint and undergo cell division despite persistent damage, a process called adaptation to DNA damage. Interestingly, adaptation occurs with a delayed timing compared to repair and shows a large variation in time, two properties that may provide a survival advantage at the population level without interfering with repair. Here, we explore this idea by mathematically modelling cell survival in response to DNA damage and focusing on adaptation parameters. We find that the delayed adaptation timing indeed maximizes survival, but its heterogeneity is beneficial only in a fluctuating damage-inducing environment. Finally, we show that adaptation does not only contribute to survival but also to genome instability and mutations, which might represent another criterion for its selection through-out evolution. Overall, we propose that adaptation can act as a bet-hedging mechanism for cell survival in response to DNA damage.

scholarly journals Adaptation to DNA damage as a bet-hedging mechanism in a fluctuating environment

2021 ◽  
Vol 8 (8) ◽  
pp. 210460
Author(s):  
Pierre Roux ◽  
Delphine Salort ◽  
Zhou Xu
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Cell Survival ◽  
Genome Instability ◽  
Population Level ◽  
Signalling Pathway ◽  
Genome Integrity ◽  
Dna Damage Checkpoint ◽  
Bet Hedging

In response to DNA damage, efficient repair is essential for cell survival and genome integrity. In eukaryotes, the DNA damage checkpoint is a signalling pathway that coordinates this response and arrests the cell cycle to provide time for repair. However, when repair fails or when the damage is not repairable, cells can eventually bypass the DNA damage checkpoint and undergo cell division despite persistent damage, a process called adaptation to DNA damage. Interestingly, adaptation occurs with a delayed timing compared with repair and shows a large variation in time, two properties that may provide a survival advantage at the population level without interfering with repair. Here, we explore this idea by mathematically modelling cell survival in response to DNA damage and focusing on adaptation parameters. We find that the delayed adaptation timing indeed maximizes survival, but its heterogeneity is beneficial only in a fluctuating damage-inducing environment. Finally, we show that adaptation does not only contribute to survival but also to genome instability and mutations, which might represent another criterion for its selection throughout evolution. Overall, we propose that adaptation can act as a bet-hedging mechanism for cell survival in response to DNA damage.

scholarly journals Orchestration of the S-phase and DNA damage checkpoint pathways by replication forks from early origins

2008 ◽  
Vol 180 (6) ◽  
pp. 1073-1086 ◽  
Author(s):  
Julie M. Caldwell ◽  
Yinhuai Chen ◽  
Kaila L. Schollaert ◽  
James F. Theis ◽  
George F. Babcock ◽  
...  
Keyword(s):  
Dna Damage ◽  
Replication Fork ◽  
S Phase ◽  
Dna Damage Checkpoint ◽  
Replication Forks ◽  
Checkpoint Signaling ◽  
Checkpoint Pathway ◽  
Origin Licensing ◽  
Pause Site ◽  
S Phase Checkpoint

The S-phase checkpoint activated at replication forks coordinates DNA replication when forks stall because of DNA damage or low deoxyribonucleotide triphosphate pools. We explore the involvement of replication forks in coordinating the S-phase checkpoint using dun1Δ cells that have a defect in the number of stalled forks formed from early origins and are dependent on the DNA damage Chk1p pathway for survival when replication is stalled. We show that providing additional origins activated in early S phase and establishing a paused fork at a replication fork pause site restores S-phase checkpoint signaling to chk1Δ dun1Δ cells and relieves the reliance on the DNA damage checkpoint pathway. Origin licensing and activation are controlled by the cyclin–Cdk complexes. Thus, oncogene-mediated deregulation of cyclins in the early stages of cancer development could contribute to genomic instability through a deficiency in the forks required to establish the S-phase checkpoint.

scholarly journals The Role of MRN in the S-Phase DNA Damage Checkpoint Is Independent of Its Ctp1-dependent Roles in Double-Strand Break Repair and Checkpoint Signaling

2009 ◽  
Vol 20 (7) ◽  
pp. 2096-2107 ◽  
Author(s):  
Mary E. Porter-Goff ◽  
Nicholas Rhind
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Strand Break ◽  
Double Strand Break ◽  
S Phase ◽  
Double Strand Break Repair ◽  
Dna Damage Checkpoint ◽  
Checkpoint Signaling ◽  
Break Repair ◽  
S Phase Checkpoint

The Mre11-Rad50-Nbs1 (MRN) complex has many biological functions: processing of double-strand breaks in meiosis, homologous recombination, telomere maintenance, S-phase checkpoint, and genome stability during replication. In the S-phase DNA damage checkpoint, MRN acts both in activation of checkpoint signaling and downstream of the checkpoint kinases to slow DNA replication. Mechanistically, MRN, along with its cofactor Ctp1, is involved in 5′ resection to create single-stranded DNA that is required for both signaling and homologous recombination. However, it is unclear whether resection is essential for all of the cellular functions of MRN. To dissect the various roles of MRN, we performed a structure–function analysis of nuclease dead alleles and potential separation-of-function alleles analogous to those found in the human disease ataxia telangiectasia-like disorder, which is caused by mutations in Mre11. We find that several alleles of rad32 (the fission yeast homologue of mre11), along with ctp1Δ, are defective in double-strand break repair and most other functions of the complex, but they maintain an intact S phase DNA damage checkpoint. Thus, the MRN S-phase checkpoint role is separate from its Ctp1- and resection-dependent role in double-strand break repair. This observation leads us to conclude that other functions of MRN, possibly its role in replication fork metabolism, are required for S-phase DNA damage checkpoint function.

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