scholarly journals TOR Signaling Is a Determinant of Cell Survival in Response to DNA Damage

2007 ◽  
Vol 27 (20) ◽  
pp. 7007-7017 ◽  
Author(s):  
Changxian Shen ◽  
Cynthia S. Lancaster ◽  
Bin Shi ◽  
Hong Guo ◽  
Padma Thimmaiah ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Survival ◽  
Genotoxic Stress ◽  
S Phase ◽  
Yeast Cells ◽  
Tor Signaling ◽  
Dna Damaging Agents ◽  
Survival Pathway ◽  
Dependent Cell ◽  
Induced Mutagenesis

ABSTRACT The conserved TOR (target of rapamycin) kinase is part of a TORC1 complex that regulates cellular responses to environmental stress, such as amino acid starvation and hypoxia. Dysregulation of Akt-TOR signaling has also been linked to the genesis of cancer, and thus, this pathway presents potential targets for cancer chemotherapeutics. Here we report that rapamycin-sensitive TORC1 signaling is required for the S-phase progression and viability of yeast cells in response to genotoxic stress. In the presence of the DNA-damaging agent methyl methanesulfonate (MMS), TOR-dependent cell survival required a functional S-phase checkpoint. Rapamycin inhibition of TORC1 signaling suppressed the Rad53 checkpoint-mediated induction of ribonucleotide reductase subunits Rnr1 and Rnr3, thereby abrogating MMS-induced mutagenesis and enhancing cell lethality. Moreover, cells deleted for RNR3 were hypersensitive to rapamycin plus MMS, providing the first demonstration that Rnr3 contributes to the survival of cells exposed to DNA damage. Our findings support a model whereby TORC1 acts as a survival pathway in response to genotoxic stress by maintaining the deoxynucleoside triphosphate pools necessary for error-prone translesion DNA polymerases. Thus, TOR-dependent cell survival in response to DNA-damaging agents coincides with increased mutation rates, which may contribute to the acquisition of chemotherapeutic drug resistance.

scholarly journals Protein Phosphatase Pph3 and Its Regulatory Subunit Psy2 Regulate Rad53 Dephosphorylation and Cell Morphogenesis during Recovery from DNA Damage in Candida albicans

2011 ◽  
Vol 10 (11) ◽  
pp. 1565-1573 ◽  
Author(s):  
Ling Ling Sun ◽  
Wan Jie Li ◽  
Hai Tao Wang ◽  
Jie Chen ◽  
Ping Deng ◽  
...  
Keyword(s):  
Dna Damage ◽  
Candida Albicans ◽  
Uv Light ◽  
Pathogenic Fungus ◽  
Genotoxic Stress ◽  
Filamentous Growth ◽  
Yeast Cells ◽  
Regulatory Subunit ◽  
Content Type ◽  
Dna Damaging Agents

ABSTRACT The ability of the pathogenic fungus Candida albicans to switch cellular morphologies is important for infection and virulence. Recent studies have revealed that C. albicans yeast cells can switch to filamentous growth under genotoxic stress in a manner dependent on the DNA replication/damage checkpoint. Here, we have investigated the functions of Pph3 (orf19.4378) and Psy2 (orf19.3685), whose orthologues in Saccharomyces cerevisiae mediate the dephosphorylation of the DNA damage checkpoint kinase Rad53 and the histone variant H2AX during recovery from DNA damage. Deleting PPH3 or PSY2 causes hypersensitivity to DNA-damaging agents, including cisplatin, methylmethane sulfonate (MMS), and UV light. In addition, pph3 Δ and psy2 Δ cells exhibit strong filamentous growth under genotoxic stress. Flow cytometry analysis shows that the mutant cells have lost the ability to adapt to genotoxic stress and remain arrested even after the stress is withdrawn. Furthermore, we show that Pph3 and Psy2 are required for the dephosphorylation of Rad53, but not H2AX, during DNA damage recovery. Taken together, these results show that C. albicans Pph3 and Psy2 have important roles in mediating genotoxin-induced filamentous growth and regulating Rad53 dephosphorylation.

scholarly journals Regulation of p53 by Hypoxia: Dissociation of Transcriptional Repression and Apoptosis from p53-Dependent Transactivation

2001 ◽  
Vol 21 (4) ◽  
pp. 1297-1310 ◽  
Author(s):  
Constantinos Koumenis ◽  
Rodolfo Alarcon ◽  
Ester Hammond ◽  
Patrick Sutphin ◽  
William Hoffman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Target Genes ◽  
P53 Protein ◽  
Genotoxic Stress ◽  
Protein Accumulation ◽  
Dependent Cell ◽  
Apoptotic Activity ◽  
Induced Apoptosis

ABSTRACT Hypoxic stress, like DNA damage, induces p53 protein accumulation and p53-dependent apoptosis in oncogenically transformed cells. Unlike DNA damage, hypoxia does not induce p53-dependent cell cycle arrest, suggesting that p53 activity is differentially regulated by these two stresses. Here we report that hypoxia induces p53 protein accumulation, but in contrast to DNA damage, hypoxia fails to induce endogenous downstream p53 effector mRNAs and proteins. Hypoxia does not inhibit the induction of p53 target genes by ionizing radiation, indicating that p53-dependent transactivation requires a DNA damage-inducible signal that is lacking under hypoxic treatment alone. At the molecular level, DNA damage induces the interaction of p53 with the transcriptional activator p300 as well as with the transcriptional corepressor mSin3A. In contrast, hypoxia primarily induces an interaction of p53 with mSin3A, but not with p300. Pretreatment of cells with an inhibitor of histone deacetylases that relieves transcriptional repression resulted in a significant reduction of p53-dependent transrepression and hypoxia-induced apoptosis. These results led us to propose a model in which different cellular pools of p53 can modulate transcriptional activity through interactions with transcriptional coactivators or corepressors. Genotoxic stress induces both kinds of interactions, whereas stresses that lack a DNA damage component as exemplified by hypoxia primarily induce interaction with corepressors. However, inhibition of either type of interaction can result in diminished apoptotic activity.

scholarly journals RAD51 localization and activation following DNA damage

2004 ◽  
Vol 359 (1441) ◽  
pp. 87-93 ◽  
Author(s):  
Madalena Tarsounas ◽  
Adelina A. Davies ◽  
Stephen C. West
Keyword(s):  
Dna Damage ◽  
Genome Stability ◽  
Critical Role ◽  
S Phase ◽  
Double Strand Breaks ◽  
Focus Formation ◽  
Rad51 Protein ◽  
Strand Breaks ◽  
Dna Damaging Agents ◽  
Binding Level

The efficient repair of double–strand breaks in DNA is critical for the maintenance of genome stability. In response to ionizing radiation and other DNA–damaging agents, the RAD51 protein, which is essential for homologous recombination, relocalizes within the nucleus to form distinct foci that can be visualized by microscopy and are thought to represent sites where repair reactions take place. The formation of RAD51 foci in response to DNA damage is dependent upon BRCA2 and a series of proteins known as the RAD51 paralogues (RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3), indicating that the components present within foci assemble in a carefully orchestrated and ordered manner. By contrast, RAD51 foci that form spontaneously as cells undergo DNA replication at S phase occur without the need for BRCA2 or the RAD51 paralogues. It is known that BRCA2 interacts directly with RAD51 through a series of degenerative motifs known as the BRC repeats. These interactions modulate the ability of RAD51 to bind DNA. Taken together, these observations indicate that BRCA2 plays a critical role in controlling the actions of RAD51 at both the microscopic (focus formation) and molecular (DNA binding) level.

scholarly journals Microtubule dynamics drive enhanced chromatin motion and mobilize telomeres in response to DNA damage

2017 ◽  
Vol 28 (12) ◽  
pp. 1701-1711 ◽  
Author(s):  
Josh Lawrimore ◽  
Timothy M. Barry ◽  
Raymond M. Barry ◽  
Alyssa C. York ◽  
Brandon Friedman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Nuclear Envelope ◽  
Strand Break ◽  
Single Particle Tracking ◽  
Microtubule Dynamics ◽  
Yeast Cells ◽  
Dna Damaging Agents ◽  
Polymer Models ◽  
Chromosomal Loci ◽  
Microtubule Function

Chromatin exhibits increased mobility on DNA damage, but the biophysical basis for this behavior remains unknown. To explore the mechanisms that drive DNA damage–induced chromosome mobility, we use single-particle tracking of tagged chromosomal loci during interphase in live yeast cells together with polymer models of chromatin chains. Telomeres become mobilized from sites on the nuclear envelope and the pericentromere expands after exposure to DNA-damaging agents. The magnitude of chromatin mobility induced by a single double-strand break requires active microtubule function. These findings reveal how relaxation of external tethers to the nuclear envelope and internal chromatin–chromatin tethers, together with microtubule dynamics, can mobilize the genome in response to DNA damage.

scholarly journals A Role for Saccharomyces cerevisiae Chk1p in the Response to Replication Blocks

2004 ◽  
Vol 15 (9) ◽  
pp. 4051-4063 ◽  
Author(s):  
Kaila L. Schollaert ◽  
Julie M. Poisson ◽  
Jennifer S. Searle ◽  
Jennifer A. Schwanekamp ◽  
Craig R. Tomlinson ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Damage ◽  
Transcriptional Response ◽  
S Phase ◽  
Yeast Cells ◽  
Dna Damage Checkpoint ◽  
Checkpoint Kinases ◽  
Checkpoint Pathway ◽  
Dna Replication And Repair ◽  
S Phase Checkpoint

Replication blocks and DNA damage incurred during S phase activate the S-phase and intra-S-phase checkpoint responses, respectively, regulated by the Atrp and Chk1p checkpoint kinases in metazoans. In Saccharomyces cerevisiae, these checkpoints are regulated by the Atrp homologue Mec1p and the kinase Rad53p. A conserved role of these checkpoints is to block mitotic progression until DNA replication and repair are completed. In S. cerevisiae, these checkpoints include a transcriptional response regulated by the kinase Dun1p; however, dun1Δ cells are proficient for the S-phase-checkpoint-induced anaphase block. Yeast Chk1p kinase regulates the metaphase-to-anaphase transition in the DNA-damage checkpoint pathway via securin (Pds1p) phosphorylation. However, like Dun1p, yeast Chk1p is not required for the S-phase-checkpoint-induced anaphase block. Here we report that Chk1p has a role in the intra-S-phase checkpoint activated when yeast cells replicate their DNA in the presence of low concentrations of hydroxyurea (HU). Chk1p was modified and Pds1p was transiently phosphorylated in this response. Cells lacking Dun1p were dependent on Chk1p for survival in HU, and chk1Δ dun1Δ cells were defective in the recovery from replication interference caused by transient HU exposure. These studies establish a relationship between the S-phase and DNA-damage checkpoint pathways in S. cerevisiae and suggest that at least in some genetic backgrounds, the Chk1p/securin pathway is required for the recovery from stalled or collapsed replication forks.

scholarly journals The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor

2013 ◽  
Vol 24 (21) ◽  
pp. 3350-3357 ◽  
Author(s):  
Tsvetomira Ivanova ◽  
Isabel Alves-Rodrigues ◽  
Blanca Gómez-Escoda ◽  
Chaitali Dutta ◽  
James A. DeCaprio ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Fission Yeast ◽  
Yeast Cells ◽  
Replication Checkpoint ◽  
Dna Damaging Agents ◽  
Dna Replication Checkpoint ◽  
Transcriptional Complex ◽  
Carboxy Terminal ◽  
Cycle Regulation

In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)–dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex.

Genotoxicity of Chemical Compounds Identification and Assessment by Yeast Cells Transformed With GFP Reporter Constructs Regulated by the PLM2 or DIN7 Promoter

2015 ◽  
Vol 34 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Van Ngoc Bui ◽  
Thi Thu Huyen Nguyen ◽  
Yvan Bettarel ◽  
Thi Hoai Thu Nguyen ◽  
Thuy Linh Pham ◽  
...  
Keyword(s):  
Dna Damage ◽  
High Throughput Screening ◽  
Fluorescent Protein ◽  
Chemical Compounds ◽  
Cost Effective ◽  
Yeast Cells ◽  
Fluorescence Signal ◽  
Inducible Promoters ◽  
Dna Damaging Agents ◽  
Green Fluorescent

Yeast cells transformed with high-copy number plasmids comprising a green fluorescent protein (GFP)-encoding gene optimized for yeast under the control of the new DIN7 or PLM2 and the established RNR2 and RAD54 promoters were used to assess the genotoxic potential of chemical compounds. The activity of potential DNA-damaging agents was investigated by genotoxicity assays and by OxoPlate assay in the presence of various test compounds. The fluorescence signal generated by GFP in response to DNA damage was related to the different concentrations of analytes and the analyte-dependent GFP synthesis. The use of distinct DNA damage-inducible promoters presents alternative genotoxicity testing strategies by selective induction of promoters in response to DNA damage. The new DIN7 and PLM2 systems show higher sensitivity than the RNR2 and RAD54 systems in detecting 4-nitroquinoline- N-oxide and actinomycin D. Both DIN7 and PLM2 systems are able to detect camptothecin while RNR2 and RAD54 systems are not. Automated laboratory systems with assay performance on 384-well microplates provide for cost-effective high-throughput screening of DNA-damaging agents, reducing compound consumption to about 53% as compared with existing eukaryotic genotoxicity bioassays.

scholarly journals Topoisomerase III Acts Upstream of Rad53p in the S-Phase DNA Damage Checkpoint

2001 ◽  
Vol 21 (21) ◽  
pp. 7150-7162 ◽  
Author(s):  
Ronjon K. Chakraverty ◽  
Jonathan M. Kearsey ◽  
Thomas J. Oakley ◽  
Muriel Grenon ◽  
Maria-Angeles de la Torre Ruiz ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cellular Response ◽  
Cell Cycle Progression ◽  
Uv Light ◽  
S Phase ◽  
Dna Damaging Agents ◽  
Topoisomerase Iii ◽  
Rad53 Kinase ◽  
S Phase Checkpoint

ABSTRACT Deletion of the Saccharomyces cerevisiae TOP3gene, encoding Top3p, leads to a slow-growth phenotype characterized by an accumulation of cells with a late S/G2content of DNA (S. Gangloff, J. P. McDonald, C. Bendixen, L. Arthur, and R. Rothstein, Mol. Cell. Biol. 14:8391–8398, 1994). We have investigated the function of TOP3 during cell cycle progression and the molecular basis for the cell cycle delay seen in top3Δ strains. We show that top3Δ mutants exhibit a RAD24-dependent delay in the G2 phase, suggesting a possible role for Top3p in the resolution of abnormal DNA structures or DNA damage arising during S phase. Consistent with this notion,top3Δ strains are sensitive to killing by a variety of DNA-damaging agents, including UV light and the alkylating agent methyl methanesulfonate, and are partially defective in the intra-S-phase checkpoint that slows the rate of S-phase progression following exposure to DNA-damaging agents. This S-phase checkpoint defect is associated with a defect in phosphorylation of Rad53p, indicating that, in the absence of Top3p, the efficiency of sensing the existence of DNA damage or signaling to the Rad53 kinase is impaired. Consistent with a role for Top3p specifically during S phase, top3Δ mutants are sensitive to the replication inhibitor hydroxyurea, expression of the TOP3 mRNA is activated in late G1 phase, and DNA damage checkpoints operating outside of S phase are unaffected by deletion of TOP3. All of these phenotypic consequences of loss of Top3p function are at least partially suppressed by deletion of SGS1, the yeast homologue of the human Bloom's and Werner's syndrome genes. These data implicate Top3p and, by inference, Sgs1p in an S-phase-specific role in the cellular response to DNA damage. A model proposing a role for these proteins in S phase is presented.

scholarly journals Pedigree analyses of yeast cells recovering from DNA damage allow assignment of lethal events to individual post-treatment generations.

Genetics ◽  
1990 ◽  
Vol 124 (1) ◽  
pp. 57-65
Author(s):  
F Klein ◽  
A Karwan ◽  
U Wintersberger
Keyword(s):  
Dna Damage ◽  
Post Treatment ◽  
Yeast Cells ◽  
Dependent Manner ◽  
The Third ◽  
Lethal Mutations ◽  
Dna Damaging Agents ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Insight Into

Abstract Haploid cells of Saccharomyces cerevisiae were treated with different DNA damaging agents at various doses. A study of the progeny of individual such cells (by pedigree analyses up to the third generation) allowed the assignment of lethal events to distinct post treatment generations. By microscopically inspecting those cells which were not able to form visible colonies we could discriminate between cells dying from immediately effective lethal hits and those generating microcolonies (three to several hundred cells) probably as a consequence of lethal mutation(s). The experimentally obtained numbers of lethal events (which we call apparent lethal fixations) were mathematically transformed into mean probabilities of lethal fixations as taking place in cells of certain post treatment generations. Such analyses give detailed insight into the kinetics of lethality as a consequence of different kinds of DNA damage. For example, X-irradiated cells lost viability mainly by lethal hits (which we call 00-fixations); only at a higher dose also lethal mutations fixed in the cells that were in direct contact with the mutagen (which we call 0-fixations), but not in later generations, occurred. Ethyl methanesulfonate (EMS)-treated cells were hit by 00-fixations in a dose dependent manner; 0-fixations were not detected for any dose of EMS applied; the probability for fixation of lethal mutations was found equally high for cells of the first and second post treatment generation and, unexpectedly, was well above control in the third post-treatment generation. The distribution of all sorts of lethal fixations taken together, which occurred in the EMS-damaged cell families, was not random.(ABSTRACT TRUNCATED AT 250 WORDS)

A Role for NIPA in DNA Damage Response.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1265-1265
Author(s):  
Christine von Klitzing ◽  
Florian Bassermann ◽  
Stephan W. Morris ◽  
Christian Peschel ◽  
Justus Duyster
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Damage Response ◽  
Phosphorylation Site ◽  
Genotoxic Stress ◽  
S Phase ◽  
Damage Response ◽  
A Cell ◽  
Cycle Dependent

Abstract The nuclear interaction partner of ALK (NIPA) is a nuclear protein identified by our group in a screen for NPM-ALK interaction partners. We recently reported that NIPA is an F-box protein that assembles with SKP1, Cul1 and Roc1 to establish a novel SCF-type E3 ubiquitin ligase. The formation of the SCFNIPA complex is regulated by cell cycle-dependent phosphorylation of NIPA that restricts SCFNIPA assembly from G1- to late S-phase, thus allowing its substrates to be active from late S-phase throughout mitosis. Proteins involved in cell cycle regulation frequently play a role in DNA damage checkpoints. We therefore sought to determine whether NIPA has a function in the cellular response to genotoxic stress. For this reason we treated NIH/3T3 cells with various DNA-damaging agents. Surprisingly, we observed phosphorylation of NIPA in response to some of these agents, including UV radiation. This phosphorylation was cell cycle phase independent and thus independent of the physiological cell cycle dependent phosphorylation of NIPA. The relevant phosphorylation site is identical to the respective site in the course of cell cycle-dependent phosphorylation of NIPA. Thus, phosphorylation of NIPA upon genotoxic stress would inactivate the SCFNIPA complex in a cell cycle independent manner. Interestingly, this phosphorylation site lies within a consensus site of the Chk1/Chk2 checkpoint kinases. These kinases are central to DNA damage checkpoint signaling. Chk1 is activated by ATR in response to blocked replication forks as they occur after treatment with UV. We performed experiments using the ATM/ATR inhibitor caffeine and the Chk1 inhibitor SB218078 to investigate a potential role of Chk1 in NIPA phosphorylation. Indeed, we found both inhibitors to prevent UV-induced phosphorylation of NIPA. Current experiments applying Chk1 knock-out cells will unravel the role of Chk1 in NIPA phosphorylation. Additional experiments were performed to investigate a function for NIPA in DNA-damage induced apoptosis. In this regard, we observed overexpression of NIPA WT to induce apoptosis in response to UV, whereas no proapoptotic effect was seen with the phosphorylation deficient NIPA mutant. Therefore, the phosphorylated form of NIPA may be involved in apoptotic signaling pathways. In summary, we present data suggesting a cell cycle independent function for NIPA. This activity is involved in DNA damage response and may be involved in regulating apoptosis upon genotoxic stress.

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