scholarly journals Spontaneous Chromosome Loss in Saccharomyces cerevisiae Is Suppressed by DNA Damage Checkpoint Functions

Genetics ◽  
2001 ◽  
Vol 159 (4) ◽  
pp. 1501-1509 ◽  
Author(s):  
Hannah L Klein
Keyword(s):  
Dna Damage ◽  
Genomic Instability ◽  
Recessive Gene ◽  
Causative Factor ◽  
S Phase ◽  
Dna Damage Checkpoint ◽  
Chromosome Loss ◽  
Yeast Strains ◽  
Dna Damage Checkpoints ◽  
Spontaneous Chromosome

Abstract Genomic instability is one of the hallmarks of cancer cells and is often the causative factor in revealing recessive gene mutations that progress cells along the pathway to unregulated growth. Genomic instability can take many forms, including aneuploidy and changes in chromosome structure. Chromosome loss, loss and reduplication, and deletions are the majority events that result in loss of heterozygosity (LOH). Defective DNA replication, repair, and recombination can significantly increase the frequency of spontaneous genomic instability. Recently, DNA damage checkpoint functions that operate during the S-phase checkpoint have been shown to suppress spontaneous chromosome rearrangements in haploid yeast strains. To further study the role of DNA damage checkpoint functions in genomic stability, we have determined chromosome loss in DNA damage checkpoint-deficient yeast strains. We have found that the DNA damage checkpoints are essential for preserving the normal chromosome number and act synergistically with homologous recombination functions to ensure that chromosomes are segregated correctly to daughter cells. Failure of either of these processes increases LOH events. However, loss of the G2/M checkpoint does not result in an increase in chromosome loss, suggesting that it is the various S-phase DNA damage checkpoints that suppress chromosome loss. The mec1 checkpoint function mutant, defective in the yeast ATR homolog, results in increased recombination through a process that is distinct from that operative in wild-type cells.

scholarly journals DNA damage checkpoint dynamics drive cell cycle phase transitions

2017 ◽  
Author(s):  
Hui Xiao Chao ◽  
Cere E. Poovey ◽  
Ashley A. Privette ◽  
Gavin D. Grant ◽  
Hui Yan Chao ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Phase Transitions ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Dna Damage Checkpoint ◽  
Cycle Progression ◽  
Dna Damage Checkpoints

ABSTRACTDNA damage checkpoints are cellular mechanisms that protect the integrity of the genome during cell cycle progression. In response to genotoxic stress, these checkpoints halt cell cycle progression until the damage is repaired, allowing cells enough time to recover from damage before resuming normal proliferation. Here, we investigate the temporal dynamics of DNA damage checkpoints in individual proliferating cells by observing cell cycle phase transitions following acute DNA damage. We find that in gap phases (G1 and G2), DNA damage triggers an abrupt halt to cell cycle progression in which the duration of arrest correlates with the severity of damage. However, cells that have already progressed beyond a proposed “commitment point” within a given cell cycle phase readily transition to the next phase, revealing a relaxation of checkpoint stringency during later stages of certain cell cycle phases. In contrast to G1 and G2, cell cycle progression in S phase is significantly less sensitive to DNA damage. Instead of exhibiting a complete halt, we find that increasing DNA damage doses leads to decreased rates of S-phase progression followed by arrest in the subsequent G2. Moreover, these phase-specific differences in DNA damage checkpoint dynamics are associated with corresponding differences in the proportions of irreversibly arrested cells. Thus, the precise timing of DNA damage determines the sensitivity, rate of cell cycle progression, and functional outcomes for damaged cells. These findings should inform our understanding of cell fate decisions after treatment with common cancer therapeutics such as genotoxins or spindle poisons, which often target cells in a specific cell cycle phase.

scholarly journals Checkpoint Adaptation Precedes Spontaneous and Damage-Induced Genomic Instability in Yeast

2001 ◽  
Vol 21 (5) ◽  
pp. 1710-1718 ◽  
Author(s):  
David J. Galgoczy ◽  
David P. Toczyski
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Genomic Instability ◽  
Cell Cycle Progression ◽  
Repair Process ◽  
Yeast Cells ◽  
Chromosome Loss ◽  
Checkpoint Adaptation ◽  
Block Cell Cycle Progression ◽  
Break Induced Replication

ABSTRACT Despite the fact that eukaryotic cells enlist checkpoints to block cell cycle progression when their DNA is damaged, cells still undergo frequent genetic rearrangements, both spontaneously and in response to genotoxic agents. We and others have previously characterized a phenomenon (adaptation) in which yeast cells that are arrested at a DNA damage checkpoint eventually override this arrest and reenter the cell cycle, despite the fact that they have not repaired the DNA damage that elicited the arrest. Here, we use mutants that are defective in checkpoint adaptation to show that adaptation is important for achieving the highest possible viability after exposure to DNA-damaging agents, but it also acts as an entrée into some forms of genomic instability. Specifically, the spontaneous and X-ray-induced frequencies of chromosome loss, translocations, and a repair process called break-induced replication occur at significantly reduced rates in adaptation-defective mutants. This indicates that these events occur after a cell has first arrested at the checkpoint and then adapted to that arrest. Because malignant progression frequently involves loss of genes that function in DNA repair, adaptation may promote tumorigenesis by allowing genomic instability to occur in the absence of repair.

MDC1 is required for the intra-S-phase DNA damage checkpoint

Nature ◽  
2003 ◽  
Vol 421 (6926) ◽  
pp. 952-956 ◽  
Author(s):  
Michal Goldberg ◽  
Manuel Stucki ◽  
Jacob Falck ◽  
Damien D'Amours ◽  
Dinah Rahman ◽  
...  
Keyword(s):  
Dna Damage ◽  
S Phase ◽  
Dna Damage Checkpoint

scholarly journals DNA Damage Checkpoint Responses in the S Phase of Synchronized Diploid Human Fibroblasts

2014 ◽  
Vol 91 (1) ◽  
pp. 109-116 ◽  
Author(s):  
Paul D. Chastain ◽  
Bruna P. Brylawski ◽  
Yingchun C. Zhou ◽  
Shangbang Rao ◽  
Haitao Chu ◽  
...  
Keyword(s):  
Dna Damage ◽  
Human Fibroblasts ◽  
S Phase ◽  
Dna Damage Checkpoint

scholarly journals When heat casts a spell on the DNA damage checkpoints

Open Biology ◽  
2014 ◽  
Vol 4 (3) ◽  
pp. 140008 ◽  
Author(s):  
Thomas Turner ◽  
Thomas Caspari
Keyword(s):  
Dna Damage ◽  
Ataxia Telangiectasia ◽  
Current Knowledge ◽  
Dna Damage Checkpoint ◽  
Ataxia Telangiectasia Mutated ◽  
Patron Saint ◽  
Checkpoint Kinases ◽  
Dna Damage Checkpoints ◽  
Heat Response ◽  
Elevated Body Temperature

Peregrine Laziosi (1265–1345), an Italian priest, became the patron saint of cancer patients when the tumour in his left leg miraculously disappeared after he developed a fever. Elevated body temperature can cause tumours to regress and sensitizes cancer cells to agents that break DNA. Why hyperthermia blocks the repair of broken chromosomes by changing the way that the DNA damage checkpoint kinases ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) are activated is an unanswered question. This review discusses the current knowledge of how heat affects the ATR–Chk1 and ATM–Chk2 kinase networks, and provides a possible explanation of why homeothermal organisms such as humans still possess this ancient heat response.

Reducing MCM Loading Causes Chromosomal Aneuploidy.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3349-3349
Author(s):  
Stephen J. Orr ◽  
Terry Gaymes ◽  
Rong Wang ◽  
Barbara Czepulkowski ◽  
Darius Ladon ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
T Cells ◽  
Dna Replication ◽  
Genomic Instability ◽  
Chromosomal Abnormalities ◽  
S Phase ◽  
Human T Cells ◽  
Dna Damage Responses ◽  
Mcm Proteins

Abstract Normal DNA replication must be accurate and occur only once per cell cycle. Sites of DNA replication are specified by binding the origin recognition complex, that includes minichromosome maintenance (MCM) proteins. Paradoxically, in higher eukaryotes MCM proteins are present in >20 fold excess of that required for DNA replication. They are also downregulated by elevated expression of proteins such as cyclin E that occurs in cancers, including AML and breast cancer. We investigated why human cells need “excess” MCM proteins and whether the reduction of MCM protein levels might contribute to a malignant phenotype. We determined the consequences of reducing the levels of MCM proteins in primary human T cells in which cell cycle controls and DNA damage responses are normal. Mass spectrometry sequencing of chromatin/nuclear matrix-bound proteins and western blotting identified that Mcm7 is not present in quiescent, normal primary human T cells. Mcm7 is induced in mid G1after the G0→G1 commitment point, the point beyond which T cells are committed to entering the cell cycle. Reduction of Mcm7 with siRNA to <5% of normal during G0→G1→S-phase reduces chromatin-binding of each of the MCM proteins that form the DNA helicase. However, these cells still enter S-phase and replicate DNA. Reducing MCM levels by titrating siRNA causes dose-dependent DNA-damage responses involving activation of ATR & ATM and Chk1 & Chk2. However, cells depleted of Mcm7 do not undergo apoptosis, rather reducing MCM levels even by 50% causes gross non-clonal chromosomal abnormalities normally found in genomic instability syndromes. M-FISH identified chromosome translocations, as well as loss and gain of individual chromosomes, which can occur individually or together in the same cell. Reducing MCM levels also causes misrepair by non-homologous end joining (NHEJ), and both NHEJ and homologous recombination (HR) are necessary for chromosomal abnormalities to occur. Therefore, “excess” MCM proteins that are present in a normal, proliferating cell are necessary for maintaining genome stability and reduction of MCM loading onto DNA that occurs in cancers is sufficient to cause genomic instability.

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.

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