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Radioresistant DNA synthesis can also be used for NBS.

T1 - Ataxia-telangiectasia cell extracts confer radioresistant DNA synthesis on control cells

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Radioresistant DNA Synthesis | Scientist Solutions

PubMed=; DOI=
Kraakman-van der Zwet M., Overkamp W.J.I., van Lange R.E.E., Essers J., van Duijn-Goedhart A., Wiggers I., Swaminathan S., van Buul P.P.W., Errami A., Tan R.T.L., Jaspers N.G.J., Sharan S.K., Kanaar R., Zdzienicka M.Z.
Brca2 (XRCC11) deficiency results in radioresistant DNA synthesis and a higher frequency of spontaneous deletions.
Mol. Cell. Biol. 22:669-679(2002)

Radioresistant DNA synthesis in cells of patients …

The checkpoint kinase Chk2 has a key role in delaying cell cycle progression in response to DNA damage. Upon activation by low-dose ionizing radiation (IR), which occurs in an ataxia telangiectasia mutated (ATM)-dependent manner, Chk2 can phosphorylate the mitosis-inducing phosphatase Cdc25C on an inhibitory site, blocking entry into mitosis, and p53 on a regulatory site, causing G1 arrest. Here we show that the ATM-dependent activation of Chk2 by γ- radiation requires Nbs1, the gene product involved in the Nijmegen breakage syndrome (NBS), a disorder that shares with AT a variety of phenotypic defects including chromosome fragility, radiosensitivity, and radioresistant DNA synthesis. Thus, whereas in normal cells Chk2 undergoes a time-dependent increased phosphorylation and induction of catalytic activity against Cdc25C, in NBS cells null for Nbs1 protein, Chk2 phosphorylation and activation are both defective. Importantly, these defects in NBS cells can be complemented by reintroduction of wild-type Nbs1, but neither by a carboxy-terminal deletion mutant of Nbs1 at amino acid 590, unable to form a complex with and to transport Mre11 and Rad50 in the nucleus, nor by an Nbs1 mutated at Ser343 (S343A), the ATM phosphorylation site. Chk2 nuclear expression is unaffected in NBS cells, hence excluding a mislocalization as the cause of failed Chk2 activation in Nbs1-null cells. Interestingly, the impaired Chk2 function in NBS cells correlates with the inability, unlike normal cells, to stop entry into mitosis immediately after irradiation, a checkpoint abnormality that can be corrected by introduction of the wild-type but not the S343A mutant form of Nbs1. Altogether, these findings underscore the crucial role of a functional Nbs1 complex in Chk2 activation and suggest that checkpoint defects in NBS cells may result from the inability to activate Chk2.

transduction pathways and radioresistant DNA synthesis

First trimester prenatal diagnosis of the Nijmege breakage syndrome and ataxia telengictasia using an assay of radioresistant DNA synthesis.

N2 - We have investigated in greater detail the radioresistant DNA synthesis universally observed in cells from patients with ataxia-telangiectasia (A-T). The approach employed in this study was to permeabilize cells with lysolecithin after γ-irradiation and thus facilitate the introduction of cell extract into these cells. This permeabilization can be reversed by diluting the cells in growth medium. Cells treated in this way show the characteristic inhibition (control cells) or lack of it (A-T cells) after exposure to ionizing radiation. Introduction of A-T cells extracts into control cells prevented the radiationinduced inhibition of DNA synthesis normally observed in these cells. A-T cell extracts did not change the level of radioresistant DNA synthesis in A-T cells. Control cell extracts on the other hand did not influence the pattern of inhibition of DNA synthesis in either cell type. It seems likely that the agent involved is a protein because of its heat lability and sensitivity to trypsin digestion. It has a molecular weight (MW) in the range 20-30000 D. The development of this assay system for a factor conferring radioresistant DNA synthesis on control cells provides a means of purifying this factor, and ultimately an approach to identifying the gene responsible.

We have investigated in greater detail the radioresistant DNA synthesis universally observed in cells from patients with ataxia-telangiectasia (A-T). The approach employed in this study was to permeabilize cells with lysolecithin after γ-irradiation and thus facilitate the introduction of cell extract into these cells. This permeabilization can be reversed by diluting the cells in growth medium. Cells treated in this way show the characteristic inhibition (control cells) or lack of it (A-T cells) after exposure to ionizing radiation. Introduction of A-T cells extracts into control cells prevented the radiationinduced inhibition of DNA synthesis normally observed in these cells. A-T cell extracts did not change the level of radioresistant DNA synthesis in A-T cells. Control cell extracts on the other hand did not influence the pattern of inhibition of DNA synthesis in either cell type. It seems likely that the agent involved is a protein because of its heat lability and sensitivity to trypsin digestion. It has a molecular weight (MW) in the range 20-30000 D. The development of this assay system for a factor conferring radioresistant DNA synthesis on control cells provides a means of purifying this factor, and ultimately an approach to identifying the gene responsible.

Radioresistant DNA synthesis can also ..

First trimester prenatal diagnosis of AT is also possible now biochemically by an assay of radioresistant DNA synthesis(3).

The pH step alkaline elution and alkaline sucrose gradient techniques were utilized to evaluate alterations in DNA replication (initiation and elongation) induced by heat and low dose X-irradiation in synchronized Chinese hamster ovary cells. The initiation and elongation processes of DNA synthesis were radioresistant at the G1/S boundary (4 hours after mitosis) while in mid S phase (9 hours after mitosis) DNA initiation and elongation were sensitive to X-irradiation. The initiation and elongation processes of DNA synthesis which were radiation resistant at the G1/S boundary could be inhibited by a hyperthermia treatment (43°C for 1 hour beginning at 4 hours after mitosis). The impairment of initiation in the heated cells was maintained through late S phase while that of elongation was reversible as judged by full recovery at 15 hours after mitosis. These data suggest that the known synergistic lethality of heat and radiation may be mediated by an impairment of initiation of DNA synthesis.

N2 - Members of the phosphatidylinositol-3 kinase related kinase (PIKK) family function in both cell cycle progression and DNA damage-induced cell cycle checkpoints. The fungal metabolite, wortmannin, is an effective radiosensitizer that irreversibly inhibits certain members of the PIKK family. Based on their roles in DNA damage responses, several PIKKs, DNA- dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM) and the ataxia- and Rad3-related protein (ATR), are potential targets for the radiosensitizing effect of wortmannin. In this report, we demonstrate that wortmannin is a relatively potent inhibitor of DNA-PK (IC 50, 16 nM) and ATM (IC 50, 150 nM) activities, whereas ATR activity is significantly less sensitive to this drug (IC 50 1.8 μM). In intact A549 lung adenocarcinoma cells, wortmannin inhibited both DNA-PK and ATM at concentrations that correlated closely with those required for radiosensitization. Furthermore, pretreatment of A549 cells with wortmannin resulted in radioresistant DNA synthesis, a characteristic abnormality of ATM-deficient cells. These results identify wortmannin as an inhibitor of ATM activity and suggest that ATM and DNA-PK are relevant targets for the radiosensitizing effect of this drug in cancer cells.

In a molecular genetic approach the features of radioresistant DNA synthesis (RDS) have been effectively used(13).
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  • and radioresistant DNA synthesis.

    ATLD exhibits hypersensitivity to ionizing radiation and radioresistant DNA synthesis.

  • Similar radioresistant DNA synthesis occurs in …

    This pathway was proven by the presence of radioresistant DNA synthesis, ..

  • Adaptive response: some underlying mechanisms and …

    This property is usually referred to as “radioresistant DNA synthesis” (RDS), a ..

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MRE11 Gene - GeneCards | MRE11 Protein | MRE11 …

N2 - The pH step alkaline elution and alkaline sucrose gradient techniques were utilized to evaluate alterations in DNA replication (initiation and elongation) induced by heat and low dose X-irradiation in synchronized Chinese hamster ovary cells. The initiation and elongation processes of DNA synthesis were radioresistant at the G1/S boundary (4 hours after mitosis) while in mid S phase (9 hours after mitosis) DNA initiation and elongation were sensitive to X-irradiation. The initiation and elongation processes of DNA synthesis which were radiation resistant at the G1/S boundary could be inhibited by a hyperthermia treatment (43°C for 1 hour beginning at 4 hours after mitosis). The impairment of initiation in the heated cells was maintained through late S phase while that of elongation was reversible as judged by full recovery at 15 hours after mitosis. These data suggest that the known synergistic lethality of heat and radiation may be mediated by an impairment of initiation of DNA synthesis.

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AB - The pH step alkaline elution and alkaline sucrose gradient techniques were utilized to evaluate alterations in DNA replication (initiation and elongation) induced by heat and low dose X-irradiation in synchronized Chinese hamster ovary cells. The initiation and elongation processes of DNA synthesis were radioresistant at the G1/S boundary (4 hours after mitosis) while in mid S phase (9 hours after mitosis) DNA initiation and elongation were sensitive to X-irradiation. The initiation and elongation processes of DNA synthesis which were radiation resistant at the G1/S boundary could be inhibited by a hyperthermia treatment (43°C for 1 hour beginning at 4 hours after mitosis). The impairment of initiation in the heated cells was maintained through late S phase while that of elongation was reversible as judged by full recovery at 15 hours after mitosis. These data suggest that the known synergistic lethality of heat and radiation may be mediated by an impairment of initiation of DNA synthesis.

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AB - Members of the phosphatidylinositol-3 kinase related kinase (PIKK) family function in both cell cycle progression and DNA damage-induced cell cycle checkpoints. The fungal metabolite, wortmannin, is an effective radiosensitizer that irreversibly inhibits certain members of the PIKK family. Based on their roles in DNA damage responses, several PIKKs, DNA- dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM) and the ataxia- and Rad3-related protein (ATR), are potential targets for the radiosensitizing effect of wortmannin. In this report, we demonstrate that wortmannin is a relatively potent inhibitor of DNA-PK (IC 50, 16 nM) and ATM (IC 50, 150 nM) activities, whereas ATR activity is significantly less sensitive to this drug (IC 50 1.8 μM). In intact A549 lung adenocarcinoma cells, wortmannin inhibited both DNA-PK and ATM at concentrations that correlated closely with those required for radiosensitization. Furthermore, pretreatment of A549 cells with wortmannin resulted in radioresistant DNA synthesis, a characteristic abnormality of ATM-deficient cells. These results identify wortmannin as an inhibitor of ATM activity and suggest that ATM and DNA-PK are relevant targets for the radiosensitizing effect of this drug in cancer cells.

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