The cellular response to DNA damage is critical for maintenance of genomic integrity and inhibition of tumorigenesis. Mutations or aberrant expression of the E3 ubiquitin ligase EDD have been observed in a number of carcinomas and we recently reported that EDD modulates activity of the DNA damage checkpoint kinase, CHK2. Here, we demonstrate that EDD is necessary for G(1)/S and intra S phase DNA damage checkpoint activation and for the maintenance of G(2)/M arrest after double strand DNA breaks. Defective checkpoint activation in EDD-depleted cells led to radio-resistant DNA synthesis, premature entry into mitosis, accumulation of polyploid cells, and cell death via mitotic catastrophe. In addition to decreased CHK2 activation in EDD-depleted cells, the expression of several key cell cycle mediators including Cdc25A/C and E2F1 was altered, suggesting that these checkpoint defects may be both CHK2-dependent and -independent. These data support a role for EDD in the maintenance of genomic stability,
DNA damage plays a causal role in numerous human pathologies including cancer, premature aging and chronic inflammatory conditions. In response to genotoxic insults, the DNA damage response (DDR) orchestrates DNA damage checkpoint activation and facilitates the removal of DNA lesions. The DDR can also arouse the immune system by for example inducing the expression of antimicrobial peptides as well as ligands for receptors found on immune cells. The activation of immune signalling is triggered by different components of the DDR including DNA damage sensors, transducer kinases, and effectors. In this review, we describe recent advances on the understanding of the role of DDR in activating immune signalling. We highlight evidence gained into (i) which molecular and cellular pathways of DDR activate immune signalling, (ii) how DNA damage drives chronic inflammation, and (iii) how chronic inflammation causes DNA damage and pathology in humans.
One function of cell cycle checkpoints is to integrate cell cycle progression with DNA replication and repair. Therefore, the integrity of these checkpoints is considered essential in maintaining genetic stability. Mutations in checkpoint components may lead to aberrant cell cycle progression and, in the presence of DNA damage, may lead to subsequent genetic instability. DNA damage triggers a variety of cellular responses, including activation of DNA damage response pathways. In fission yeast, genetic evidence pointed to a model in which five checkpoint Rad proteins, Rad1, Rad9, Rad17, Rad26, and Hus1, sense DNA alterations and then cooperate to send a signal through Rad3 (1) . Rad3 can also function in the absence of several of these Rad genes, suggesting that Rad3 may interact with other proteins involved in the DNA damage response (4) .. In S. pombe the cell cycle checkpoint gene Rad1 is required to ensure that mitosis does not occur in the presence of DNA damage (8 , 9) . X-Spy1 was ...
Proteins involved in the DNA damage response accumulate as microscopically-visible nuclear foci on the chromatin flanking DNA double-strand breaks (DSBs). As growth of ionizing radiation (IR)-induced foci amplifies the ATM-dependent DNA damage signal, the formation of discrete foci plays a crucial role in cell cycle checkpoint activation, especially in cells exposed to lower doses of IR. However, there is no quantitative parameter for the foci which considers both the number and their size. Therefore, we have developed a novel parameter for DNA damage signal based on the image analysis of the foci and quantified the amount of the signal sufficient for G2 arrest. The parameter that we have developed here was designated as SOID. SOID is an abbreviation of Sum Of Integrated Density, which represents the sum of fluorescence of each focus within one nucleus. The SOID was calculated for individual nucleus as the sum of (area (total pixel numbers) of each focus) x (mean fluorescence intensity per pixel of each
Daily exposure to environmental agents (reactive oxygen species, methylating agents, UV light, and other ionizing radiation) and normal physiological processes (replication and recombination) all damage DNA. Cells must repair DNA damage to prevent mutations from propagating and accumulating, and to maintain genome integrity and stability. The ATM and ATR genes often initiate the DNA damage response, activating signal transduction pathways that arrest the cell cycle and increase the expression of DNA repair genes. Enzymes involved in base-excision, nucleotide excision, mismatch, double-strand break, and other DNA repair processes all respond in a pre- and post-transcriptionally regulated fashion to DNA damage. Incomplete DNA repair normally activates cell death pathways such as apoptosis. Cells unable to sense and repair DNA damage may continue to grow and divide, eventually causing cellular dysfunction and death, a hallmark of diseases such as neurological defects and infertility. However, ...
DNA damage (alkaline filter elution) and sister chromatid exchange (SCE) frequencies were measured in lymphocytes of 39 welders and 39 controls. The welders showed a significantly higher rate of DNA single-strand breakages and significantly elevated SCE values. These results are not in accordance with those of a former study in which only DNA-protein cross-links were measured. The different results may be explained on the basis of different exposure levels for chromium(VI) and nickel. Both methods are not specific but sensitive enough to measure genotoxic damage after occupational exposure to chromium(VI) and nickel in the range of threshold values for the workplace on a collective basis. Additionally, the results indicate that DNA single-strand breakage and DNA-protein cross-links show different increases depending on the exposure levels for chromium and nickel. ...
TY - JOUR. T1 - Attenuating the DNA damage response to double-strand breaks restores function in models of CNS neurodegeneration. AU - Tuxworth , Richard AU - Taylor, Matthew AU - Anduaga, Ane Martin AU - Hussien-Ali, Al. AU - Chatzimatthaiou, Sotiroula AU - Longland, Joanne AU - Thompson, Adam. AU - Almutiri, Sharif AU - Alifragis, Pavlos. AU - Kyriacou, Charalambos AU - Kysela, Boris AU - Ahmed, Zubair PY - 2019/7/2. Y1 - 2019/7/2. N2 - DNA double-strand breaks are a feature of many acute and long-term neurological disorders, including neurodegeneration, following neurotrauma and after stroke. Persistent activation of the DNA damage response in response to double-strand breaks contributes to neural dysfunction and pathology as it can force post-mitotic neurons to re-enter the cell cycle leading to senescence or apoptosis. Mature, non-dividing neurons may tolerate low levels of DNA damage, in which case muting the DNA damage response might be neuroprotective. Here, we show that attenuating the ...
Faithful duplication and segregation of undamaged DNA is critical to the survival of all organisms and prevention of oncogenesis in multicellular organisms. To ensure inheritance of intact DNA, cells rely on checkpoints. Checkpoints alter cellular processes in the presence of DNA damage preventing cell cycle transitions until replication is completed or DNA damage is repaired. Several checkpoints are specific to S-phase. The S-M replication checkpoint prevents mitosis in the presence of unreplicated DNA. Rather than outright halting replication, the S-phase DNA damage checkpoint slows replication in response to DNA damage. This checkpoint utilizes two general mechanisms to slow replication. First, this checkpoint prevents origin firing thus limiting the number of replication forks traversing the genome in the presence of damaged DNA. Second, this checkpoint slows the progression of the replication forks. Inhibition of origin firing in response to DNA damage is well established, however when this thesis
In light of the studies discussed above (and below), we suggest a revised model of the DNA damage response (Fig. 2). In this model, DNA damage is initially detected by specific repair factor(s) that have an affinity for specific types of primary DNA lesion. In some cases, the lesion may be relatively easy to repair so that the DNA damage becomes rapidly reversed after initial detection. Under these circumstances, repair would occur sufficiently quickly to prevent recognition by components of the Mec1p/Tel1p signaling network and initiation of the DNA damage response. Consistent with this, it has been reported that HO-induced DSBs only trigger Rad53p activation when repair of these lesions is prevented by inactivation of HR (50). Similarly, even though hydrogen peroxide-induced DNA base damage does not trigger Rad53p activation during G1 or G2 in wild-type yeast cells, decreasing the efficiency of BER allows Rad53p activation in response to this type of DNA damage (51). Furthermore, when ...
As part of the heterotrimeric replication protein A complex (RPA/RP-A), binds and stabilizes single-stranded DNA intermediates, that form during DNA replication or upon DNA stress. It prevents their reannealing and in parallel, recruits and activates different proteins and complexes involved in DNA metabolism. Thereby, it plays an essential role both in DNA replication and the cellular response to DNA damage. In the cellular response to DNA damage, the RPA complex controls DNA repair and DNA damage checkpoint activation. Through recruitment of ATRIP activates the ATR kinase a master regulator of the DNA damage response. It is required for the recruitment of the DNA double-strand break repair factors RAD51 and RAD52 to chromatin in response to DNA damage. Also recruits to sites of DNA damage proteins like XPA and XPG that are involved in nucleotide excision repair and is required for this mechanism of DNA repair. Plays also a role in base excision repair (BER) probably through interaction with ...
The vast majority of DNA damage affects the primary structure of the double helix in which the bases are chemically modified. These modifications can in turn disrupt the molecules regular helical structure by introducing non-native chemical bonds or bulky adducts that do not fit in the standard double helix. DNA damages that are naturally occurring due to metabolism and its byproducts occur at a high rate in the body. Most of these damages to DNA from naturally occurring metabolism are repaired. However, there may remain some DNA damage despite the action of repair processes. These remaining DNA damages accumulate in the tissues.. There are a number of sources that contribute to DNA damage. DNA damage can be subdivided into two main types, either endogenous damage from naturally occurring metabolic processes and/or exogenous damage caused by external agents.. Endogenous damage caused by metabolic byproducts (naturally occurring):. ...
TY - JOUR. T1 - Undamaged DNA transmits and enhances DNA damage checkpoint signals in early embryos. AU - Peng, Aimin. AU - Lewellyn, Andrea L.. AU - Maller, James L.. PY - 2007/10/1. Y1 - 2007/10/1. N2 - 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 ...
Background Dot1L, a histone methyltransferase that targets histone H3 lysine 79 (H3K79), has been implicated in gene regulation and the DNA damage response although its functions in these processes remain poorly defined. Methodology/Principal Findings Using the chicken DT40 model system, we generated cells in which the Dot1L gene is disrupted to examine the function and focal recruitment of the 53Bp1 DNA damage response protein. Detailed kinetic and dose response assays demonstrate that, despite the absence of H3K79 methylation demonstrated by mass spectrometry, 53Bp1 focal recruitment is not compromised in these cells. We also describe, for the first time, the phenotypes of a cell line lacking both Dot1L and 53Bp1. Dot1L¿/¿ and wild type cells are equally resistant to ionising radiation, whereas 53Bp1¿/¿/Dot1L¿/¿ cells display a striking DNA damage resistance phenotype. Dot1L and 53Bp1 also affect the expression of many genes. Loss of Dot1L activity dramatically alters the mRNA levels of ...
The DNA damage response (DDR) is a signal transduction pathway that decides the cells fate either to repair DNA damage or to undergo apoptosis if there is too much damage. Post-translational modifications modulate the assembly and activity of protein complexes during the DDR pathways. MicroRNAs (miRNAs) are emerging as a class of endogenous gene modulators that control protein levels, thereby adding a new layer of regulation to the DDR. In this review, we describe a new role for miRNAs in regulating the cellular response to DNA damage with a focus on DNA double-strand break damage. We also discuss the implications of miRNAs role in the DDR to stem cells, including embryonic stem cells and cancer stem cells, stressing the potential applications for miRNAs to be used as sensitizers for cancer radiotherapy and chemotherapy.
The circadian control of an organisms response to DNA damage response rests upon circadian proteins which play important roles in the processes of cell proliferation and control of response to genotoxic stress both at the cellular and organismal levels [83]. DNA damage triggers cellular stress response pathways which may result in checkpoint cell cycle arrest, apoptosis or DNA repair. DNA damage leads to activation of critical components of cellular stress response pathways including ATM/ATR (ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related) and CHK1/2 (checkpoint kinase1/2) which in turn activates tumour suppressor protein p53 and subsequently causes cell cycle arrest or apoptosis [84]. It has been shown that Bmal1-deficient human cells are unable to undergo growth arrest on p53 activation by DNA damage. Contrary to in vivo mouse data connecting BMAL1-dependent delay in G1 progression to upregulation of p21 [82], radiation induced growth arrest in Bmal1-deficient human ...
One function of cell cycle checkpoints is to integrate cell cycle progression with DNA replication and repair. Therefore, the integrity of these checkpoints is considered essential in maintaining genetic stability. Mutations in checkpoint components may lead to aberrant cell cycle progression and, in the presence of DNA damage, may lead to subsequent genetic instability. DNA damage triggers a variety of cellular responses, including activation of DNA damage response pathways. In fission yeast, genetic evidence pointed to a model in which five checkpoint Rad proteins, Rad1, Rad9, Rad17, Rad26, and Hus1, sense DNA alterations and then cooperate to send a signal through Rad3 (1) . Rad3 can also function in the absence of several of these Rad genes, suggesting that Rad3 may interact with other proteins involved in the DNA damage response (4) .. In S. pombe the cell cycle checkpoint gene Rad1 is required to ensure that mitosis does not occur in the presence of DNA damage (8 , 9) . X-Spy1 was ...
PubMedID: 23220418 | Dimer exchange and cleavage specificity of the DNA damage response protein UmuD. | Biochimica et biophysica acta | 2/1/2013
CRISPR/Cas9 induces DNA double-strand breaks that are repaired by cell-autonomous repair pathways, namely, non-homologous end-joining (NHEJ), or homology-directed repair (HDR). While HDR is absent in G1, NHEJ is active throughout the cell cycle and, thus, is largely favored over HDR. We devised a strategy to increase HDR by directly synchronizing the expression of Cas9 with cell-cycle progression. Fusion of Cas9 to the N-terminal region of human Geminin converted this gene-editing protein into a substrate for the E3 ubiquitin ligase complex APC/Cdh1, resulting in a cell-cycle-tailored expression with low levels in G1 but high expression in S/G2/M. Importantly, Cas9-hGem(1/110) increased the rate of HDR by up to 87% compared to wild-type Cas9. Future developments may enable high-resolution expression of genome engineering proteins, which might increase HDR rates further, and may contribute to a better understanding of DNA repair pathways due to spatiotemporal control of DNA damage induction ...
The kinase ATM is classically known for its role in coordinating the response to DNA damage. DNA damage is caused by various intracellular and extracellular stimuli, including oxidative stress and free radicals. Lee et al. found critical amino acid residues that enable ATM to coordinate a response to DNA damage that is independent of its response to oxidative stress. Activation of ATM by either pathway promoted mitochondrial function and autophagy, thus mediating cell survival through metabolic changes. ATM activation via oxidative stress additionally promoted the clearance of toxic protein aggregates. These findings expand the roles of ATM and suggest that the loss of ATM function, such as in the neurodegenerative disease ataxia telangiectasia (A-T), causes broader cellular stress than that limited to a defective DNA damage response. ...
DNA damage (or RNA damage in the case of some virus genomes) appears to be a fundamental problem for life. As noted by Haynes,[14] the subunits of DNA are not endowed with any peculiar kind of quantum mechanical stability, and thus DNA is vulnerable to all the "chemical horrors" that might befall any such molecule in a warm aqueous medium. These chemical horrors are DNA damages that include various types of modification of the DNA bases, single- and double-strand breaks, and inter-strand cross-links (see DNA damage (naturally occurring). DNA damages are distinct from mutations although both are errors in the DNA. Whereas DNA damages are abnormal chemical and structural alterations, mutations ordinarily involve the normal four bases in new arrangements. Mutations can be replicated, and thus inherited when the DNA replicates. In contrast, DNA damages are altered structures that cannot, themselves, be replicated. Several different repair processes can remove DNA damages (see chart in DNA repair). ...
Time resolved data of DNA damage and repair after radiotherapy elucidates the relation between damage, repair, and cell survival. While well characterized in vitro, little is known about the time-course of DNA damage response in tumors sampled from individual patients. Kinetics of DNA damage after radiotherapy was assessed in eight dogs using repeated in vivo samples of tumor and co-irradiated normal tissue analyzed with comet assay and phosphorylated H2AX (γH2AX) immunohistochemistry. In vivo results were then compared (in silico) with a dynamic mathematical model for DNA damage formation and repair. Maximum %DNA in tail was observed at 15-60 min after irradiation, with a rapid decrease. Time-courses of γH2AX-foci paralleled these findings with a small time delay and were not influenced by covariates. The evolutionary parameter search based on %DNA in tail revealed a good fit of the DNA repair model to in vivo data for pooled sarcoma time-courses, but fits for individual sarcoma time-courses suffer
By Kristian Moss Bendtsen, Jeppe Juul, Ala Trusina. DNA damages, as well as mutations, increase with age. It is believed that these result from increased genotoxic stress and decreased capacity for DNA repair. The two causes are not independent, DNA damage can, for example, through mutations, compromise the capacity for DNA repair, which in turn increases the amount of unrepaired DNA damage. Despite this vicious circle, we ask, can cells maintain a high DNA repair capacity for some time or is repair capacity bound to continuously decline with age? We here present a simple mathematical model for ageing in multicellular systems where cells subjected to DNA damage can undergo full repair, go apoptotic, or accumulate mutations thus reducing DNA repair capacity. Our model predicts that at the tissue level repair rate does not continuously decline with age, but instead has a characteristic extended period of high and non-declining DNA repair capacity, followed by a rapid decline. Furthermore, the time ...
Upon viral infection, the major defense mounted by the host innate immune system is activation of the IFN- and apoptosis-mediated antiviral pathway. In order to complete their life cycle, viruses that are obligatory intracellular parasites must modulate these host immune responses. We have previously shown that the γHV68 latency-associated M2 protein effectively downregulates STAT1 and STAT2, resulting in the inhibition of type I and II IFN-mediated transcriptional activation. Here, we demonstrate that M2 interacts with ATM, a DNA damage signal transducer, and the DDB1/COP9/cullin DNA damage effector complex. This interaction blocked DNA damage-sensing activity as well as DNA damage repair activity, thereby rendering cells resistant to DNA damage-induced apoptosis. These results indicate that γHV68 encodes M2, a latency-associated gene, to antagonize both IFN- and apoptosis-mediated host innate immunities and thus is important in establishing and maintaining viral latency in infected ...
MCC is a potential tumor suppressor gene, which is silenced by promoter hypermethylation in a subset of colorectal cancers. However, its functions have remained poorly understood. In the present study, we describe a novel function of MCC in the DNA damage response. Several novel phosphorylation sites were identified by mass spectrometry, including 2 highly conserved ATM/ATR consensus sites at serine 118 and serine 120. In addition, exposure to ultraviolet radiation (UV), but not phleomycin, caused PI3K-dependent phosphorylation of MCC and its nuclear localization. Re-expression of MCC in HCT15 colorectal cancer cells led to a G2/M arrest, and MCC knockdown impaired the induction of a G2/M arrest following UV radiation. Finally, mutation of S118/120 to alanine did not affect MCC nuclear shuttling following UV but did impair MCC G2/M checkpoint activity. Thus, these results suggest that MCC is a novel target of the DNA damage checkpoint and that MCC is required for the complete cell cycle arrest in the G2
The 25 gene deletions that conferred increased Dna2 foci were strongly enriched for genes involved in DNA repair and DNA damage response (Figure 4B) (P = 2×10−17 and P = 5×10−16). We compared these genes to those identified in a recent "constitutive RNR3 expression" screen (Hendry et al. 2015) and found significant overlap (16 genes, hypergeometric P = 4×10−21), suggesting the presence of increased spontaneous DNA damage in these mutants, as expression of RNR3 responds specifically to DNA damage (Elledge and Davis 1990). We compared the genes that, when deleted, caused increased Dna2 foci to those that cause increased Rad52 foci (Alvaro et al. 2007), again finding significant overlap (10 genes, hypergeometric P = 2×10−11). Finally, we compared the set of genes with negative genetic interactions with dna2-1 or dna2-2 (Budd et al. 2005), which could indicate spontaneous damage that requires Dna2 for its repair. We noted a significant overlap (10 genes, hypergeometric P = 2×10−14). ...
Stem cell dysfunction is closely linked to tissue and organismal aging and age-related diseases, and heavily influenced by the niche cells environment. The DNA damage response (DDR) is a key pathway for tissue degeneration and organismal aging; however, the precise protective role of DDR in stem cell/niche aging is unclear. The Drosophila midgut is an excellent model to study the biology of stem cell/niche aging because of its easy genetic manipulation and its short lifespan. Here, we showed that deficiency of DDR in Drosophila enterocytes (ECs) accelerates intestinal stem cell (ISC) aging. We generated flies with knockdown of Mre11, Rad50, Nbs1, ATM, ATR, Chk1, and Chk2, which decrease the DDR system in ECs. EC-specific DDR depletion induced EC death, accelerated the aging of ISCs, as evidenced by ISC hyperproliferation, DNA damage accumulation, and increased centrosome amplification, and affected the adult flys survival. Our data
Stem cell dysfunction is closely linked to tissue and organismal aging and age-related diseases, and heavily influenced by the niche cells environment. The DNA damage response (DDR) is a key pathway for tissue degeneration and organismal aging; however, the precise protective role of DDR in stem cell/niche aging is unclear. The Drosophila midgut is an excellent model to study the biology of stem cell/niche aging because of its easy genetic manipulation and its short lifespan. Here, we showed that deficiency of DDR in Drosophila enterocytes (ECs) accelerates intestinal stem cell (ISC) aging. We generated flies with knockdown of Mre11, Rad50, Nbs1, ATM, ATR, Chk1, and Chk2, which decrease the DDR system in ECs. EC-specific DDR depletion induced EC death, accelerated the aging of ISCs, as evidenced by ISC hyperproliferation, DNA damage accumulation, and increased centrosome amplification, and affected the adult flys survival. Our data
In mammalian cells, RB/E2F and p53 are intimately connected, and crosstalk between these pathways is critical for the induction of cell cycle arrest or cell death in response to cellular stresses. Here we have investigated the genetic interactions between RBF/E2F and p53 pathways during Drosophila development. Unexpectedly, we find that the pro-apoptotic activities of E2F and p53 are independent of one another when examined in the context of Drosophila development: apoptosis induced by the deregulation of dE2F1, or by the overexpression of dE2F1, is unaffected by the elimination of dp53; conversely, dp53-induced phenotypes are unaffected by the elimination of dE2F activity. However, dE2F and dp53 converge in the context of a DNA damage response. Both dE2F1/dDP and dp53 are required for DNA damage-induced cell death, and the analysis of rbf1 mutant eye discs indicates that dE2F1/dDP and dp53 cooperatively promote cell death in irradiated discs. In this context, the further deregulation in the expression
Radiotherapy resistance is one of the major factors limiting the efficacy of radiotherapy in lung cancer patients. The extensive investigations indicate the diversity in the mechanisms underlying radioresistance. Here, we revealed that DNA damage binding protein 2 (DDB2) is a potential regulator in the radiosensitivity of non-small cell lung cancer (NSCLC) cells. DDB2, originally identified as a DNA damage recognition factor in the nucleotide excision repair, promotes the survival and inhibits the apoptosis of NSCLC cell lines upon ionizing radiation (IR). Mechanistic investigations demonstrated that DDB2 is able to facilitate IR-induced phosphorylation of Chk1, which plays a critical role in the cell cycle arrest and DNA repair in response to IR-induced DNA double-strand breaks (DSBs). Indeed, knockdown of DDB2 compromised the G2 arrest in the p53-proficient A549 cell line and reduced the efficiency of homologous recombination (HR) repair. Taken together, our data indicate that the expression of DDB2
Stress overload of the DDR pathway should also show efficacy in cancer treatment. Although it is not clear why DNA damaging agents, such as IR and chemotherapy, are effective cancer therapies, it is possible that these are examples of stress overload, where cancer cells with already elevated levels of DNA damage and replication stress cannot repair the additional damage inflicted by these agents. An alternative explanation is that during tumorigenesis, the persistence of DNA damage selects for cells with mutations that abrogate part of the DDR pathway and therefore cannot properly sense and respond to DNA damage. These cells with a partially defective DDR might therefore be more vulnerable to the extensive DNA damage resulting from radiation or chemotherapy that is lethal without a normal DDR pathway. In this context, DNA damage exploits a stress phenotype of tumors that is analogous to non-oncogene addition.. Given the sensitivity of many cancers to DNA damaging agents, there should exist genes ...
Research has indicated that oxidative stress is the cause of many serious diseases such as cancer, Alzheimers, arteriosclerosis and diabetes.
Cells of metazoan organisms respond to DNA damage by arresting their cell cycle to repair DNA, or they undergo apoptosis. Two protein kinases, ataxia-telangiectasia mutated (ATM) and ATM and Rad-3 related (ATR), are sensors for DNA damage. In humans, ATM is mutated in patients with ataxia-telangiectasia (A-T), resulting in hypersensitivity to ionizing radiation (IR) and increased cancer susceptibility. Cells from A-T patients exhibit chromosome aberrations and excessive spontaneous apoptosis. We used Drosophila as a model system to study ATM function. Previous studies suggest that mei-41 corresponds to ATM in Drosophila; however, it appears that mei-41 is probably the ATR ortholog. Unlike mei-41 mutants, flies deficient for the true ATM ortholog, dATM, die as pupae or eclose with eye and wing abnormalities. Developing larval discs exhibit substantially increased spontaneous chromosomal telomere fusions and p53-dependent apoptosis. These developmental phenotypes are unique to dATM, and both dATM ...
Glioblastoma multiforme (GBM) is the most common form of brain tumor with a poor prognosis and resistance to radiotherapy. Recent evidence suggests that glioma-initiating cells play a central role in radioresistance through DNA damage checkpoint activation and enhanced DNA repair. To investigate this in more detail, we compared the DNA damage response in nontumor forming neural progenitor cells (NPC) and glioma-initiating cells isolated from GBM patient specimens. As observed for GBM tumors, initial characterization showed that glioma-initiating cells have long-term self-renewal capacity. They express markers identical to NPCs and have the ability to form tumors in an animal model. In addition, these cells are radioresistant to varying degrees, which could not be explained by enhanced nonhomologous end joining (NHEJ). Indeed, NHEJ in glioma-initiating cells was equivalent, or in some cases reduced, as compared with NPCs. However, there was evidence for more efficient homologous recombination ...
Cancer treatments such as radiotherapy and most of the chemotherapies act by damaging DNA of cancer cells. Upon DNA damage, cells stop proliferation at cell cycle checkpoints, which provides them time for DNA repair. Inhibiting the checkpoint allows entry to mitosis despite the presence of DNA damage and can lead to cell death. Importantly, as cancer cells exhibit increased levels of endogenous DNA damage due to an excessive replication stress, inhibiting the checkpoint kinases alone could act as a directed anti-cancer therapy. Here, we review the current status of inhibitors targeted towards the checkpoint effectors and discuss mechanisms of their actions in killing of cancer cells.
Dr. Meyer studies the effects of genotoxic agents on human and wildlife health. He is interested in understanding the mechanisms by which environmental agents cause DNA damage, the molecular processes that organisms employ to protect prevent and repair DNA damage, and genetic differences that may lead to increased or decreased sensitivity to DNA damage. Mitochondrial DNA damage and repair are a particular focus. He studies DNA repair and other responses to DNA damage via PCR-based analysis of DNA damage and repair, genomic and systems biology approaches, and organismal-level responses.
DNA damage is a natural byproduct of cell division because it is impossible to faithfully copy each of the 3 billion nucleotides that make up our genomes without making at least a few errors. Damage can also be caused by exposure to certain chemical agents, ultraviolet light and ionizing radiation.. Most of the time these problems are recognized and quickly repaired by the cell. Thats where p53 comes in. When it is doing its job, p53 recognizes and responds to DNA damage by increasing the expression of genes involved in DNA repair and cell division. In this way it functions as a tumor suppressor. When mutated, however, p53 loses its ability to modulate the cells response to DNA damage. Mutations in p53 are among the most common causes of many types of cancer.. Chang and his collaborators found that p53 also increases the expression of DINO. DINO, in turn, binds to and stabilizes p53 in a kind of positive feedback loop, amplifying its signal throughout the nucleus.. ...
Biological Process: autophagy; base-excision repair; cell aging; cell cycle arrest; cell differentiation; cell proliferation; cellular response to DNA damage stimulus; cellular response to gamma radiation; cellular response to glucose starvation; cellular response to heat; cellular response to hypoxia; cellular response to ionizing radiation; cellular response to reactive oxygen species; cellular response to UV; chromatin assembly; circadian behavior; determination of adult lifespan; DNA damage response, signal transduction by p53 class mediator; DNA damage response, signal transduction by p53 class mediator resulting in cell cycle arrest; DNA damage response, signal transduction by p53 class mediator resulting in transcription of p21 class mediator; DNA strand renaturation; entrainment of circadian clock by photoperiod; ER overload response; G1 DNA damage checkpoint; intrinsic apoptotic signaling pathway by p53 class mediator; intrinsic apoptotic signaling pathway in response to DNA damage by ...
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14-3-3σ has been implicated in the development of chemo and radiation resistance and in poor prognosis of multiple human cancers. While it has been postulated that 14-3-3σ contributes to these resistances via inhibiting apoptosis and arresting cells in G2-M phase of the cell cycle, the molecular basis of this regulation is currently unknown. In this study, we tested the hypothesis that 14-3-3σ causes resistance to DNA-damaging treatments by enhancing DNA repair in cells arrested in G2-M phase following DNA-damaging treatments. We showed that 14-3-3σ contributed to ionizing radiation (IR) resistance by arresting cancer cells in G2-M phase following IR and by increasing non-homologous end joining (NHEJ) repair of the IR-induced DNA double strand breaks (DSB). The increased NHEJ repair activity was due to 14-3-3σ-mediated upregulation of PARP1 expression that promoted the recruitment of DNA-PKcs to the DNA damage sites for repair of DSBs. On the other hand, the increased G2-M arrest following ...
Our results indicate that serum 8-OHdG is increased already in prediabetes suggesting oxidative DNA damage to be present with minor elevation of blood glucose levels (BGLs). The statistically significant positive correlation between serum 8-OHdG and body mass index in the diabetic group indicates that obesity has an additive effect to increased BGL contributing to oxidative DNA damage ...
The identification of hundreds of somatic mutations in cancer genomes has raised critical questions as to their functional relevance. Despite efforts to analyse such mutations computationally, our work demonstrates the importance of direct functional testing, in particular of large genes mutated at moderate levels. Our work shows, by robust genetic characterisation, that Huwe1 is a tumour suppressor in the small intestine and colon. Together with our identification of HUWE1 mutations present in human CRC that perturb its ubiquitin ligase activity, this strongly suggests it is a bona fide colonic tumour suppressor gene.. This is particularly important as previous work on HUWE1s tumourigenic role had proven controversial. HUWE1 is an E3 ubiquitin ligase that controls the stability of MCL1, MYC and MYCN functions which would suggest a tumour‐suppressive role. Indeed, work using chemically induced skin cancer mouse models has indicated this is the case (Inoue et al, 2013). However, via ...
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Oxidative stress damages DNA. Researchers in the Vetsuisse Faculty have now decoded the mechanism that repairs DNA damaged in this way. This repair mechanism could lead to less invasive approaches in cancer therapy and contribute ...
phdthesis{4879304f-922e-405b-a92f-9f49b1b22a49, abstract = {Primary Sjögrens syndrome (SS) is a chronic autoimmune disease of unknown etiology. The disease primarily involves lachrymal and salivary glands, leading to dryness of the eyes and mouth, but a wide spectrum of exocrine and non-exocrine disease manifestations may be seen. A characteristic property of primary SS is the production of autoantibodies directed against intracellular, often DNA/RNA-modifying, proteins. The hypothesis initiating the present studies was that these autoantibodies reflect some alteration of the antigen, causing not only increased immunogenicity but possibly also abnormal DNA/RNA processing, for instance during repair of DNA damage. Accordingly, this thesis was conducted to explore whether an abnormal DNA damage response is involved in the pathogenesis of primary SS.,br/,,br, ,br/,,br, Initially, the mutations formed in a DNA-damaged shuttle vector plasmid repaired and replicated by SS B cell lines were found to ...
Scientists at the University of Sussex are to create a portfolio of new cancer drugs which exploit our DNA damage response (DDR) system in order to kill cancer cells - in a bid to revolutionise treatment for the disease.. The £6 million project, funded by the Wellcome Trust and in collaboration with the pharmaceutical company AstraZeneca, brings together Sussex scientists deep understanding of the ways cells respond to DNA damage with cutting edge techniques of modern drug discovery to generate a powerful new approach to treating cancer.. DNA in healthy cells is damaged thousands of times daily, but the impact is reduced by the DDR system - a network of cellular pathways which identifies and repairs the damage. However, many cancers are known to have defects within these pathways - which enable cancerous cells to grow and divide.. The University of Sussex aims to harness its detailed understanding of DDR to discover drugs which can maximise DNA damage, or prevent its repair. AstraZeneca will ...
Reactive oxygen species (ROS)-induced oxidative stress is well known to play a major role in male infertility. Sperm are sensitive to ROS damaging effects because as male germ cells form mature sperm they progressively lose the ability to repair DNA damage. However, how oxidative DNA lesions in sperm affect early embryonic development remains elusive. Using cattle as model, we show that fertilization using sperm exposed to oxidative stress caused a major developmental arrest at the time of embryonic genome activation. The levels of DNA damage response did not directly correlate with the degree of developmental defects. The early cellular response for DNA damage, γH2AX, is already present at high levels in zygotes that progress normally in development and did not significantly increase at the paternal genome containing oxidative DNA lesions. Moreover, XRCC1, a factor implicated in the last step of base excision repair (BER) pathway, was recruited to the damaged paternal genome, indicating that the
DNA base damage was assayed using gas chromatography/ mass spectrometry with selected ion monitoring (GC/MS-SIM) in renal and hepatic chromatin of male F344 rats up to 14 days after a single i.p. injection of 90 micromol Ni(II) acetate/kg body wt. Ten different damaged bases were quantified. No damage was found in either organ 12 h after Ni(II) treatment. The damage became significant only from day 1, with magnitude and persistence depending on the organ and base. In livers, levels of five DNA base products were significantly elevated over those in control rats. They were: 8-oxoguanine (by 46% at day 1 postinjection); 2,6-diamino-4-hydroxy-5-formamidopyrimidine (by 107% at day 1); 5-(hydroxymethyl)uracil (by 94% at day 1); 5,6-dihydroxyuracil (by 128% at day 1); and 5-hydroxyhydantoin (by 39% in terms of the overall adjusted means for days 1-14 post-injection). The elevation was highest at day 1 post-injection followed by a decrease at later days, except for 5-hydroxyhydantoin. In kidneys, the ...
Embryonic stem cells {ESCs} are isolated from the inner cell mass of the blastocyst. These cells are responsible for the development of the embryo proper. Accumulation of DNA damage at this stage of development would affect multiple / all lineages of the embryo which may poses danger to the health or survival of the organism and could be passed on through the germ line. One of the most threatening DNA lesions to the cell is DNA doublestrand break {DSB}. The repair of these DNA lesions in mouse ESCs {mESCs} is carried out mainly by homologous recombination {HR}. When using the correct DNA sequence as a template for DNA DSB repair, HR is of a high fidelity, otherwise it may lead to chromosomal aberrations. The low level of mutation rate measured in mESCs coupled with high rate of efficient HR during gene replacement / genome modulation experiments showed by these cells suggested that mESCs might use inter-sister recombination for repairing DNA DSBs in favour of the inter-homologue mitotic ...
Cancer is the second leading cause of deaths in the United States. This thesis focuses on two research project (1) development of novel LC-MS/MS methodology to screen chemicals and their metabolites for DNA damaging effects which might eventually lead to cancer and (2) development of automated and 3D printed elecrochemical biosensors to detect panels of prostate cancer biomarkers for early diagnosis and to differentiate aggressive and non-aggressive versions of prostate cancer. Chapter 1 gives a brief introduction and describes goals and significance of the thesis. It also gives an overview of genotoxicity, DNA damaging events, xenobiotics, and cytochrome P450 enzymes and their role in reactive metabolite formation. A brief description of P53 tumor suppressor gene and its role in cancer and organ specific cancer is also included. Chapter 2 describes the first ever restriction enzyme-assisted LC-MS/MS methodology for sequence specific DNA damage by chemical metabolites on exon 7 fragment of P53 gene. It
Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Endocrinology & Metabolism, BIOCHEMISTRY & MOLECULAR BIOLOGY, ENDOCRINOLOGY & METABOLISM, DNA damage, DNA repair, base excision repair, oxidation, hydroxyl radical, singlet oxygen, antioxidants, free radicals, BASE EXCISION-REPAIR, MAMMALIAN-CELLS, ESCHERICHIA-COLI, STRAND BREAKS, VITAMIN-C, CANCER, OXYGEN, ANTIOXIDANTS, PATHWAY ...
FUNCTION: Serine/threonine protein kinase which activates checkpoint signaling upon genotoxic stresses such as ionizing radiation (IR), ultraviolet light (UV), or DNA replication stalling, thereby acting as a DNA damage sensor. Recognizes the substrate consensus sequence [ST]-Q. Recruited in complex with protein LCD1 by the single-strand-binding protein complex RPA to DNA lesions in order to initiate the DNA repair by homologous recombination, after the MRX-complex and TEL1 are displaced. Phosphorylates LCD1 and RPA2, a subunit of RPA, involved in DNA replication, repair and recombination. Phosphorylates RAD9, CHK1 and RAD53, which leads to the activation of the CHK1 and RAD53 kinases involved in DNA damage repair cascade. Phosphorylates histone H2A to form H2AS128ph (gamma-H2A) at sites of DNA damage, also involved in the regulation of DNA damage response mechanism. Phosphorylates also SLX4 and RTT107 which are proteins involved in genome stability. Required for cell growth and meiotic ...
Human serum albumin (HSA) is an effective therapeutic agent that protects neurons after cerebral ischemia or related injuries by means of its antioxidant capacity. Our aim was to test whether bovine serum albumin (BSA) might also provide protection, especially against DNA damage. Rat cortical neurons were cultured in both the presence and absence of BSA.. To test the neuroprotective role of BSA against DNA damage and neuronal death, primary cultures were investigated using both gamma-H2AX and pATM immunocytochemistry, and the TUNEL assay, respectively. Quantitative analyses revealed that the cultures in the absence of BSA had a higher number of apoptotic neurons. Additionally, neurons showing DNA strand breaks were fewer when BSA was added to the medium. BSA acts as a neuroprotective molecule, reducing both the DNA damage and apoptosis rates. This effect is similar to that described for HSA, probably due to its antioxidant activity. Hence, we have demonstrated that BSA provides a neuroprotective ...
SRA737 is a highly selective, orally bioavailable small molecule inhibitor of Checkpoint kinase 1 (Chk1), a key regulator of important cell cycle checkpoints and central mediator of the DNA Damage Response network. In cancer cells, replication stress induced by oncogenes (e.g., MYC and RAS) or genetic mutations in DNA repair machinery (e.g. BRCA1 and FA) combined with loss of function in tumor suppressors (e.g., TP53 and ATM) results in persistent DNA damage and genomic instability leading to an increased dependency on Chk1 for survival. Targeted inhibition of Chk1 by SRA737 may therefore be synthetically lethal to these cancer cells.. The study has been designed to investigate the safety and tolerability of SRA737; to determine the pharmacokinetics of SRA737; to identify the optimal dose, schedule, and maximum tolerated dose (MTD); to obtain preliminary evidence of activity; and to evaluate preliminary efficacy in prospectively-screened, genetically-selected subjects.. This clinical study ...
The cellular genome is continuously exposed to various sources of DNA damage. Cells respond to DNA damage using extensive surveillance and repair mechanisms mediated largely by protein kinases and phosphatases. In multi-cellular organisms, the accumulation of DNA damaged cells is avoided either through the activation of cell cycle checkpoints allowing for DNA repair or through the elimination of damaged cells by apoptosis. To date, the study of the signaling mechanisms that govern the DNA damage response have focused on delineating the molecules involved in specific DNA damage response pathways. However, to develop a comprehensive understanding of how the cell responds to DNA damage, dynamic measurements of signals within each specific pathway and across pathways, encompassing the entire relevant signal transduction network, is necessary. In this work we will focus on gaining insight into the relationship between the molecular signaling and cellular response to a therapeutically relevant DNA ...
After DNA damage, cell cycle checkpoints are activated. Checkpoint activation pauses the cell cycle and gives the cell time to repair the damage before continuing to divide. DNA damage checkpoints occur at the G1/S and G2/M boundaries. An intra-S checkpoint also exists. Checkpoint activation is controlled by two master kinases, ATM and ATR. ATM responds to DNA double-strand breaks and disruptions in chromatin structure, whereas ATR primarily responds to stalled replication forks. These kinases phosphorylate downstream targets in a signal transduction cascade, eventually leading to cell cycle arrest. A class of checkpoint mediator proteins including BRCA1, MDC1, and 53BP1 has also been identified. These proteins seem to be required for transmitting the checkpoint activation signal to downstream proteins. p53 is an important downstream target of ATM and ATR, as it is required for inducing apoptosis following DNA damage.[33] At the G1/S checkpoint, p53 functions by deactivating the CDK2/cyclin E ...
TY - JOUR. T1 - Transforming growth factor-β1 mediates cellular response to DNA damage in situ. AU - Ewan, Kenneth B.. AU - Henshall-Powell, Rhonda L.. AU - Ravani, Shraddha A.. AU - Pajares, Maria Jose. AU - Arteaga, Carlos. AU - Warters, Ray. AU - Akhurst, Rosemary J.. AU - Barcellos-Hoff, Mary Helen. PY - 2002/10/15. Y1 - 2002/10/15. N2 - Transforming growth factor (TGF)-β1 is rapidly activated after ionizing radiation, but its specific role in cellular responses to DNA damage is not known. Here we use Tgfβ1 knockout mice to show that radiation-induced apoptotic response is TGF-β1 dependent in the mammary epithelium, and that both apoptosis and inhibition of proliferation in response to DNA damage decrease as a function of TGF-β1 gene dose in embryonic epithelial tissues. Because apoptosis in these tissues has been shown previously to be p53 dependent, we then examined p53 protein activation. TGF-β1 depletion, by either gene knockout or by using TGF-β neutralizing antibodies, resulted ...
Here, we show that the naphthoquinone napabucasin can be bioactivated by the cellular reductases NQO1 and, to a lesser extent, POR, resulting in the production of ROS and disruption of the cellular redox balance, resulting in DNA damage-induced cell death. Although traditionally ROS are considered to be toxic molecules causing indiscriminate damage to proteins, nucleic acids, and lipids, it is increasingly recognized that they also play a significant role as secondary messengers in cellular signaling (37). A number of transcription factors contain redox-sensitive cysteine residues at their DNA binding sites, including NF-κB, HIF-1, and p53. In addition, ROS can either inhibit or activate protein function through altering their phosphorylation status via thiol oxidation of either tyrosine phosphatases or kinases (1, 38, 39). Similar to previous reports (21-23), we observed a decrease in STAT3 phosphorylation upon treatment with napabucasin in pancreatic and breast cancer cells. However, the ...
VANCOUVER, Sept. 27, 2016- ProNAi Licenses Oncology Drug Targeting DNA Damage Response Checkpoint Kinase 1 (Chk1) from CRT Pioneer Fund, UK.
We use human primary fibroblasts for comparing plasma and gamma rays induced DNA damage. In both cases, DNA strand breaks occur, but of fundamentally different nature. Unlike gamma exposure, contact with plasma predominantly leads to single strand breaks and base-damages, while double strand breaks are mainly consequence of the cell repair mechanisms. Different cell signaling mechanisms are detected confirming this (ataxia telangiectasia mutated - ATM and ataxia telangiectasia and Rad3 related - ATR, respectively). The effective plasma doses can be tuned to match the typical therapeutic doses of 2 Gy. Tailoring the effective dose through plasma power and duration of the treatment enables safety precautions mainly by inducing apoptosis and consequently reduced frequency of micronuclei. ...
Apoptosis is a form of programmed cell death that is required for organisms to grow and develop properly and to maintain body tissues. This process is initiated when a cell is damaged or infected. DNA damage or oncogene expression, among other stimuli, can induce cell cycle arrest through the activation of special proteins involved in cell cycle checkpoints. When arrested, DNA damage can be repaired and the cell cycle can re-start. If damage persists, cells undergo apoptosis.. A hallmark of human cancer is the intrinsic or acquired resistance to cell death. Cancer cells are able to bypass apoptosis by altering the mechanisms that detect damage or abnormalities. This means that proper signalling does not occur. As a result, unrepaired damage accumulates, giving rise to mutations that allow cells to become malignant. This knowledge has been exploited for the purpose of therapy design. Several anti-cancer drugs impair the DNA damage response, thereby leading to the accumulation of cytotoxic damage, ...
by David L. Lewis, PhD Published on May 29, 2016 Persistent DNA damage causes new mutations to occur during prenatal development that can lead to the types of neurological problems associated with autism. Error-prone DNA repair processes can create new mutations that never existed in either parent. These changes, which
The cellular response to genotoxic stress is mediated by a well-characterized network of DNA surveillance pathways. The contribution of posttranscriptional gene regulatory networks to the DNA damage response (DDR) has not been extensively studied. Here, we systematically identified RNA-binding proteins differentially interacting with polyadenylated transcripts upon exposure of human breast carcinoma cells to ionizing radiation (IR). Interestingly, more than 260 proteins including many nucleolar proteins showed increased binding to poly(A) RNA in IR-exposed cells. The functional analysis of DDX54, a candidate genotoxic stress responsive RNA helicase, revealed that this protein is an immediate-to-early DDR regulator required for the splicing efficacy of its target IR-induced pre-mRNAs. Upon IR exposure, DDX54 acts by increased interaction with a well-defined class of pre-mRNAs which harbor introns with weak acceptor splice sites, as well as by protein-protein contacts within components of U2 snRNP ...
Exposure to hypoxia-induced replication arrest initiates a DNA damage response which includes both ATR and ATM-mediated signalling. DNA fiber analysis was used to show that these conditions lead to a replication arrest during both the initiation and elongation phases and that this correlated with decreased levels of nucleotides. The DNA damage response induced by hypoxia is distinct from the classical pathways induced by damaging agents primarily due to the lack of detectable DNA damage but also due to the coincident repression of DNA repair in hypoxic conditions. The principle aims of the hypoxia-induced DNA damage response appear to be the induction of p53-dependent apoptosis or the preservation of replication fork integrity. The latter is of particular importance should reoxygenation occur. Tumor reoxygenation occurs as a result of spontaneous changes in blood flow and also therapy. Cells experiencing hypoxia/reoxygenation are therefore sensitive to loss or inhibition of components of the DNA ...
We are interested in signaling pathways that contribute to the maintenance of genomic stability in our cells and prevent cancer susceptibility in humans. We are studying DNA repair pathways that are activated during the S-phase of the cell cycle when chromosomes replicate. Our research centers on the Fanconi Anemia (FA) and Breast Cancer associated (BRCA1, BRCA2) repair pathways that are suspected have crucial functions in DNA repair and cell cycle checkpoint activation during S-phase. Humans born with mutations in FA genes have a highly elevated risk to develop certain types of cancers including acute myeloid leukemia (AML) and various types of solid tumors. Acquired mutations and silencing of FA genes have been found in different cancers in the general population and the FA genes are thus considered "caretakers" of our genome. Our goal is to understand the molecular functions of the FA/BRCA proteins (currently 15 FA/BRCA genes are known) and to elucidate how these proteins communicate with ...
In international research, the primary focus has been on the core histones and their functionality, whereas little attention has been paid to the H1 histone, simply because we werent aware that it too influenced the repair process.". "Having discovered this function in H1 constitutes an important piece of the puzzle of how cells protect their DNA, and it opens a door onto hitherto unknown and highly interesting territory," Mailand said.. He expects the discovery to lead to increased research into Histone H1 worldwide, which will lead to increased knowledge of cells abilities to repair possible damage to their DNA and thus increase our knowledge of the basis for diseases caused by cellular changes.. The findings were published in the latest issue of scientific journal Nature.. ...
Accumulation of DNA mutations or impaired DNA damage repair upon aging has been seen as a critical causal contributor to aging of differentiated cells and stem cells and thus ultimately tissues. Experimental evidence though on the role of DNA damage and repair upon aging, however, remains controversial with respect to this paradigm. These data demonstrate an unexpected loss of the DNA damage induced G1-S checkpoint in both young and aged hematopoietic stem and progenitor cells (HSPCs). Induction of chronic double strand breaks via a zinc-finger nuclease further demonstrated that HSPCs strictly avoid accumulation of mutations by undergoing apoptosis rather than repair. Interestingly, aging does not alter the DNA damage response to DSBs in HSPCs and, most importantly, does not result in an elevated DNA mutational load in hematopoiesis in vivo upon repair of DNA damage. These data demonstrate a strong resilience of both the young and the aged hematopoietic system against acquiring DNA mutations in ...
Acquired and de novo resistance of tumor cells to DNA-damaging modalities (e.g., irradiation, chemotherapeutics) can be the result of alterations to DNA damage signaling and repair. Treatments targeting components of these pathways such as poly (ADP-ribose) polymerase (PARP) and the CHK1/CHK2 proteins have been explored extensively (42, 43). Preclinical and clinical studies have showed that HDAC inhibitors potentiate the effects of DNA damage inducing therapies and may contribute to overcoming therapy resistance (20, 44). As single agents, however, HDAC inhibitors have limited therapeutic efficacy against solid tumors, despite their effects on chromatin stability and transcription. Baseline HDAC2 expression correlates with response to HDAC inhibitor-anthracycline based regimens and plays an important role in chromatin regulation (11, 31). The mechanism of potentiation by HDAC inhibitors is not yet fully understood. Furthermore, the lack of predictive markers in the clinical setting has hindered ...
The multifunctional protein kinase CK2 is involved in several aspects of the DNA damage response (DDR) in mammals. To gain insight into the role of CK2 in plant genome maintenance, we studied the response to genotoxic agents of an Arabidopsis CK2 dominant-negative mutant (CK2mut plants). CK2mut plants were hypersensitive to a wide range of genotoxins that produce a variety of DNA lesions. However, they were able to activate the DDR after exposure to γ irradiation, as shown by accumulation of phosphorylated histone H2AX and up-regulation of sets of radio-modulated genes. Moreover, functional assays showed that mutant plants quickly repair the DNA damage produced by genotoxins, and that they exhibit preferential use of non-conservative mechanisms, which may explain plant lethality. The chromatin of CK2mut plants was more sensitive to digestion with micrococcal nuclease, suggesting compaction changes that agreed with the transcriptional changes detected for a number of genes involved in chromatin ...
Question: What do you think about this enclosed newspaper clipping of a recent announcement in the London Times that researchers have found that 500 mg dosages of vitamin C damages genes?. Answer: The study is real, but the conclusion that vitamin C is dangerous is unwarranted by the evidence presented. Of about 20 types of DNA damage that have been documented so far by scientists, only two types of DNA damage were measured. One increased while the other decreased. What does this mean? We dont know, for several reasons.. First, the increase in 8-oxoadenine levels (a marker of damage to adenine A nucleotides) was offset by a decrease in damage to 8-oxoguanine levels (which is a much better-researched marker of DNA damage to guanine G nucleotides). With offsetting trends, the net effect is not clear.. Second, DNA damage is an incredibly complicated process that is balanced by DNA repair mechanisms. According to estimates [Ames and Gold, 1991], each cell in the body can be expected to suffer ...
Cells continuously encounter a wide variety of intrinsic and extrinsic stresses that damage the integrity of DNA (Lindahl and Barnes, 2000). Mitochondrial respiratory chain generates reactive oxygen species (ROS), which are the most prevalent intrinsic source of DNA damage. Extrinsic sources of DNA damage are ionizing radiation (IR), ultraviolet (UV), and genotoxic chemical agents, including chemotherapeutic drugs (e.g., camptothecin, doxorubicin, and etoposide). Both of the sources attack DNA and produce DNA lesions or breaks (Dipple, 1995). If not properly repaired, these damages are capable of blocking DNA replication and transcription, leading to mutations or genome aberrations, which consequently give rise to various human diseases, such as cancer.. To maintain genome stability against the stresses, cells operate DNA damage response (DDR) to detect DNA lesions, signal their presence, and promote their repair (Harrison and Haber, 2006; Harper and Elledge, 2007; Rouse and Jackson, 2002). If ...
The goal of this study was to evaluate the preclinical efficacy of VEDT, a naturally occurring dietary product, alone and in combination with gemcitabine, a commonly used chemotherapeutic agent against pancreatic cancer, in a highly relevant and aggressive model of pancreatic cancer (KPC mouse model). We recently reported in our chemoprevention study that VEDT prevented pancreatic intraepithelial neoplasia lesions and increased survival in the conditional Kras mouse model of pancreatic cancer (14). In the present study, we found that VEDT augmented gemcitabine inhibition of tumor growth (tumor weight and proliferation index) and increased survival in the KPC mouse model.. The mechanisms for the chemopreventive effects of VEDT include a protective role against oxidative stress-induced DNA damage (11), enhancement of the immune response (30), and elimination of cancer stem cells (31). One intriguing finding that has been shown consistently by us and others is the selective killing effect of VEDT ...
Cell survival requires mechanisms to recognize and repair DNA damage. The mechanisms involved in DNA damage response (DDR) have been intensively studied and comprise ATM-, ATR- and DNA-PK-dependent pathways, which can in severe cases initiate apoptosis. Modulation of chromatin structure is a critical step for DNA repair proteins gaining access to the DNA. A recently identified modulator of chromatin structure is the Survival-time associated PHD protein in Ovarian Cancer 1 (SPOC1). SPOC1 complexes with the cellular co-repressor KRAB-associated Protein 1 (KAP1) as well as with Histone Methyltransferases (HMTs) and the Nucleosome Remodeling and Deacetylase Complex (NuRD), resulting in chromatin condensation and heterochromatin formation after the repair of DNA double strand breaks (DSBs). KAP1 function is known to be regulated via several posttranslational modifications (PTMs), such as phosphorylation and SUMOylation. In this context, KAP1 is phosphorylated and deSUMOylated upon DSBs, leading to the
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Howard Hughes Medical Institute (HHMI) researchers have identified 27 genes in brain stem cells that are prone to a type of DNA damage. The fragility of those genes could explain why they are often mutated or deleted in cancers and neuropsychiatric disorders such as schizophrenia. But their tendency to break could also benefit the brain by providing a way to produce a greater diversity of neurons.. "We found a class of DNA breaks that nobody expected," says HHMI investigator Frederick Alt of Boston Childrens Hospital who performed the research along with a team that included his colleague Bjoern Schwer, postdoctoral researcher Pei-Chi Wei, and graduate student Amelia Chang. The scientists published their results on February 11, 2016 in the journal Cell.. Broken DNA sounds like a disaster for a cell-and it often is. Unrepaired DNA damage can kill the cell or cause it to become cancerous. But broken DNA isnt all bad. As the B cells of the immune system prepare to manufacture antibodies to fight ...
The protein encoded by this gene belongs the PI3/PI4-kinase family, and is most closely related to ATM, a protein kinase encoded by the gene mutated in ataxia telangiectasia. This protein and ATM share similarity with Schizosaccharomyces pombe rad3, a cell cycle checkpoint gene required for cell cycle arrest and DNA damage repair in response to DNA damage. This kinase has been shown to phosphorylate checkpoint kinase CHK1, checkpoint proteins RAD17, and RAD9, as well as tumor suppressor protein BRCA1. Mutations of this gene are associated with Seckel syndrome. An alternatively spliced transcript variant of this gene has been reported, however, its full length nature is not known. Transcript variants utilizing alternative polyA sites exist. [provided by RefSeq, Jul 2008 ...
A model for Sml1 regulation in response to DNA damage. Prior to modification, Sml1 is bound to Rnr1 and inhibits RNR activity. Following DNA damage, Dun1 is act
Biochemical action shots with SLACs X-ray laser could help scientists develop synthetic enzymes for medicine and answer fundamental questions about how enzymes change during chemical reactions.
Such an assay has many obvious potential uses," Kastan said, "including the assessment of exposure to dangerous agents in the environment." Another potential clinical benefit of these discoveries applies to cancer prevention. Since damage to the DNA appears to contribute to the vast majority of human cancers, enhancing the response of cells to DNA damage could reduce cancer development, Kastan noted. Therefore, the discovery of how ATM is activated could help guide the development of ways to improve cellular responses to DNA damage, including responses to oxidative stress that are either induced or natural ...
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Structure of PARP1 damage recognition module (rainbow coloured) binding to a break in one strand of a DNA double helix. Scientists at the University of Sussex have solved a 30-year genetic puzzle that could help enhance treatment for certain types of "inherited" cancers.. The findings relate to an enzyme that plays an important role in the repair of DNA - the genetic blueprint for all life which in mutated form leads to the uncontrolled reproduction of cells and the development of cancers.. The enzyme - PARP1 - was first identified as a DNA damage sensor by Professor Sydney Shall in research undertaken at Sussex in the 1980s. Its discovery led to the development of drugs that blocked the DNA repair mechanism in breast, prostate and ovarian cancers found in people who have a family history of those diseases.. But for the past three decades scientists have not known exactly how the enzyme recognised and repaired DNA damage. The Cancer Research UK-funded study by the Genome Damage and Stability ...
In this study, we addressed two aspects of the role of MEI-41 in DSB repair: (1) which specific DSB repair processes are influenced by loss of MEI-41 and (2) whether the checkpoint function of MEI-41 accounts for defects in repair observed in mei-41 mutants. Our results indicate that loss of MEI-41 affects repair by HR, but not by NHEJ, and that the disruption of HR cannot be explained entirely by loss of the GRP/LOK-mediated G2-M DNA damage checkpoint. This suggests that MEI-41 regulates repair through a mechanism independent of the GRP/LOK-mediated checkpoint response.. Evidence that the effect of loss of MEI-41 is specific to HR comes from our finding that lethality of mei-41 mutants undergoing P-element excision is eliminated through use of spn-A mutations. A previous study suggested that repair of DSBs generated by P-element excision in somatic tissues occurs primarily through NHEJ (Gloor et al. 2000), but our results indicate that repair by HR is also important, at least in some essential ...
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The gene p53 suppresses cancer and inflammation in the body, and NIEHS investigators speculate that changes in p53 lead to changes in inflammation and the ability to repair DNA damage. This study wants blood samples from participants to find out how the changes in p53 lead to these conditions.. Research has shown that certain proteins in cells may be linked to higher risk of developing inflammation, tumors, and other medical problems. By examining how the blood cells of healthy volunteers respond to environmental exposures, researchers hope to better understand the relationship of genes, environmental factors, and human diseases.. For more information on this study, please visit the Clinical Trials Study page.. ...
Mutation or inactivation of RB occurs in most human tumors and results in the deregulation of several E2F family transcription factors. Among the E2F family, E2F3 has been implicated as a key regulator of cell proliferation and E2f3 gene amplification and overexpression is detected in some human tumors. To study the role of E2F3a in tumor development, we established a transgenic mouse model expressing E2F3a in a number of epithelial tissues via a keratin 5 (K5) promoter. Transgenic expression of E2F3a leads to hyperproliferation, hyperplasia and increased levels of p53-independent apoptosis in transgenic epidermis. Consistent with data from human cancers, the E2f3a transgene is found to have a weak oncogenic activity on its own and to enhance the response to a skin carcinogenesis protocol. While E2F3a induces apoptosis in the absence of p53, the inactivation of both p53 and p73, but not p73 alone, significantly impairs apoptosis induced by E2F3a. This suggests that both p53 and p73 contribute to ...
In response to genotoxic stress, the DNA damage response, which is governed primarily by the ATM-CHK2, ATR-CHK1, and p38-MK2 (also known as MAPKAPK2) checkpoint effector pathways, becomes activated in order to slow cell-cycle progression and allow time for DNA repair. The CHK1 and MK2 pathways converge on inhibition of cell division cycle 25 (CDC25)-mediated activation of cyclin-dependent kinases, prompting Dietlein and colleagues to hypothesize that simultaneous small-molecule inhibition of CHK1 and MK2 may synergistically silence the DNA damage checkpoint. To systematically characterize combinatorial drug-inhibitor relationships, 96 cancer cell lines were screened with various concentrations of the CHK1 inhibitor PF477736 and the MK2 inhibitor PF3644022, and PreCISE (predictor of chemical inhibitor synergistic effects) software was used to calculate synergism scores based on GI50 drug curves. Synergistic effects between PF477736 and PF3644022 were observed in 33 of 96 cell lines and were ...
Sigma-Aldrich offers abstracts and full-text articles by [Alessandra Cataldo, Douglas G Cheung, Andrea Balsari, Elda Tagliabue, Vincenzo Coppola, Marilena V Iorio, Dario Palmieri, Carlo M Croce].
We extended the model of Proctor & Gray (2008) [26] to include details of p53 and Mdm2 ubiquitination, the interaction of p53 with GSK3β and the activity of GSK3β. As we had used SBML to build the models, it was straight forward to make the necessary modifications. As in our previous model, we find that a sudden increase in DNA damage leads to oscillations of p53 and Mdm2. Our new model shows that the disruption of the Mdm2/p53 complex, allows the formation of GSK3β/p53 complexes which results in increased transcriptional activity of p53 and increased kinase activity of GSK3β. The result is an increase in Aβ production, an increase in Mdm2 mRNA and an increase in tau phosphorylation. Under normal conditions, the model predicts that Aβ is cleared from cells and so does not accumulate, and tau is dephosphorylated to maintain the correct balance of phosphorylated and unphosphorylated tau. However, after a stress event, the DNA damage response leads to increased activity of p53 and GSK3β ...
Mammalian cells have developed complex mechanisms to identify DNA damage and activate the required response to maintain genome integrity. Those mechanisms include DNA damage detection, DNA repair, cell cycle arrest and apoptosis which operate together to protect the conceptus from DNA damage origina …
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The incidence of abnormal FFRCT and the relationship of lesion-specific ischemia to subject demographics, symptoms, and degree of stenosis in the multicenter, prospective ADVANCE registry.(J Cardiovasc Comput Tomogr 2018 Feb 2)
The regenerative capacity of hematopoietic stem cells (HSCs) is limited by the accumulation of DNA damage. Conditional mutagenesis of the histone 3 lysine 4 (H3K4) methyltransferase, Setd1a, revealed that it is required for the expression of DNA damage recognition and repair pathways in HSCs. Specific deletion of Setd1a in adult long-term (LT)-HSCs is compatible with adult life and has little effect on the maintenance of phenotypic LT-HSCs in the bone marrow. However, SETD1A-deficient LT-HSCs lose their transcriptional cellular identity accompanied by loss of their proliferative capacity and stem cell function under replicative stress in situ and after transplantation. In response to inflammatory stimulation in vivo SETD1A protects HSCs and progenitors from activation-induced attrition. The comprehensive regulation of DNA damage responses by SETD1A in HSCs is clearly distinct from the key roles played by other epigenetic regulators including the major leukemogenic H3K4 methyltransferase, MLL1, ...
DNA damage induces a variety of responses including, oxidative stress, apoptosis and premature senescence. These responses have been implicated both in aging an...
TY - JOUR. T1 - Inter-individual and inter-cell type variation in residual DNA damage after in vivo irradiation of human skin. AU - Chua, Melvin Lee Kiang. AU - Somaiah, Navita. AU - Bourne, Sara. AU - Daley, Frances. AU - AHern, Roger. AU - Nuta, Otilia. AU - Davies, Sue. AU - Herskind, Carsten. AU - Pearson, Ann. AU - Warrington, Jim. AU - Helyer, Sarah. AU - Owen, Roger. AU - Yarnold, John. AU - Rothkamm, Kai. PY - 2011/5. Y1 - 2011/5. N2 - Purpose: The aim of this study was to compare inter-individual and inter-cell type variation in DNA double-strand break (DSB) repair following in vivo irradiation of human skin. Materials and methods: Duplicate 4 mm core biopsies of irradiated and unirradiated skin were collected from 35 patients 24 h after 4 Gy exposure using 6 MeV electrons. Residual DSB were quantified by scoring 53BP1 foci in dermal fibroblasts, endothelial cells, superficial keratinocytes and basal epidermal cells. Results: Coefficients of inter-individual variation for levels of ...
To change the message: RNA editing for neurodegenerative disorders. RNA has long been sought as a therapeutic target to provide transient amelioration of disease status without making permeant changes to the genetic markup. The recently reported RNA Editing for Programmable A-to-I Replacement (REPAIR) system is an ingenious combination of gRNA-mediated RNA-binding capability of a kinase domain-dead Cas13b and an adenosine deaminase to achieve single-base-pair RNA editing (a term coined way back at 1986). Such a system offers a highly efficient RNA editing tool to repair single-nucleotide mutations, so the bad message can be changed and "lost in translation.". REPAIR is especially advantageous for studying pathogenesis and the development of gene therapy for neurodegenerative disorders. First, because the REPAIR system does not need to involve the endogenous DNA damage repair mechanisms, such as non-homologous end-joining or homology-directed repair, it provides more efficient editing in ...
Reactome is pathway database which provides intuitive bioinformatics tools for the visualisation, interpretation and analysis of pathway knowledge.
View Notes - Lecture 4 from MCDB 144 at UCLA. Lecture #4 DNA Repair MBOC (old) Page 267-285 MBOC (new) Page 295-311 Concepts What can induce DNA Damage Describe repair mechanisms for the following
The cells machinery is ultimately controlled by the way specific genes of the cells DNA are expressed to produce proteins. So the reason a cell initially becomes improperly regulated is usually the occurrence of fresh damage to the cells DNA. Its true that problematic DNA mutations can be inherited from parents, such as the well-known breast cancer genes BRCA1 and BRCA2. Signifcantly, the normal function of both these genes, when not mutated, is to produce proteins whose job is to detect and/or repair DNA damage or to arrest cell proliferation if DNA damage is detected but cant be repaired. So mutated versions of these genes do not exactly "cause" cancer themselves, since some mutation to other genes that actively induce excessive cell proliferation is also required. The potential for cancer may simply remains latent for awhile in cells with mutated genes, regardless of whether the mutation was inherited or occurred much later in life ...
doc,The major effort in the lab is directed towards investigating how tumor-specific dysregulation of the pRB signaling pathway affects downstream gene expression and the cellular response to DNA damage. Four projects are currently underway. First, we are utilizing a modified chromatin immunoprecipitation approach to capture and identify genomic DNA target sequences conditionally associated with pRB-containing complexes recovered from intact chromatin in untransformed primary human cells. Second, we are investigating functional heterogeneity amongst closely related components in the pRB pathway. Specifically, we are conducting comparative analyses of the INK4 proteins p16INK4a and p18INK4c and their preferred target kinases, the cyclin dependent kinases cdk4 and cdk6. Third, in collaboration with Dr. Jeff Marks, we are developing a mammary gland organoid approach to quantitate and analyze parity-dependent DNA damage checkpoint responses in the context of the primary human mammary tissue. ...
If you are capable of generating a Damage effect it is in addition to, and separate from, the Damage Type done by the weapon blow itself. All blows do 1 point of damage, the damage effect will never add another point of damage to the blow although it may negate the damage, or convert the point of damage into destroying a location or armour instead. E.g. If you are struck by a Normal Harm on an armoured location the Harm converts the normal point of damage into an effect that destroys the location but does not damage the armour.. Some of the damage effects only work on a specific Target Group. If the Target Group is not on a lammie (inc. your character card) or on a loresheet, then it is considered to be a blow of the damage type used (Normal if no other damage type is called), unless you are told otherwise by a Referee or Marshal. Note that everyone defaults to the Target Group, Living, unless otherwise specified on a lammie or loresheet.. Any effect listed in Section Four can also be used as a ...
DNA Damage Control Everyday SPF 40+ and Active SPF 40+ are treatment sunscreens that provide DNA repair technology to help inhibit, guard and reverse past, present and future sun damage.