DNA Repair Monitored by an Enzymatic Assay in Multinucleate Xeroderma Pigmentosum Cells after Fusion

Paterson, Malcolm C.; Lohman, P.H.M.; Westerveld, A.; Sluyter, M.L.

doi:10.1038/248050a0

Cited by 21 publications

(9 citation statements)

References 13 publications

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“…That the UV-induced unscheduled DNA synthesis we observed in complementing binuclear XP fibroblasts represents DNA repair replication is supported by resistance of the unscheduled DNA synthesis to hydroxyurea and by experiments that indicate that such complementing, fused XP cells have normal repair replication (19), thymine dimer excision (20), and hostcell reactivation of UV-damaged adenovirus 2 (R. S. Day, III, K. H. Kraemer, and J. H. Robbins, unpublished data).…”

Section: Discussionmentioning

confidence: 97%

National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014, USA.

Kraemer¹,

Coon²,

Petinga³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

150

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Fibroblast strains from 12 patients with xeroderma pigmentosum had lower than normal rates of DNA repair, as determined by autoradiographic studies of ultraviolet-induced unscheduled nuclear DNA synthesis. The nuclei in binuclear cells, obtained by fusing fibroblasts from certain pairs of these strains, had a greater rate of DNA On coverslip cultures not treated with virus, grains over "lightly labeled" (1, 2, 5, 6) nuclei from 100 consecutively observed mononuclear cells were counted. Virus-treated coverslips were scamied under low power for areas containing multinucleate cells that had the most light labeling. In such an area, grains were counted over the 100 nuclei of 50 consecu-59 Abbreviations: XP, xeroderma pigmentosum; UV, ultraviolet.

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Section: Discussionmentioning

confidence: 97%

National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014, USA.

Kraemer¹,

Coon²,

Petinga³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

150

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“…These were correctly diagnosed after a single "blind" experiment. DISCUSSION Cells from the majority of XP patients are partly or wholly lacking in the ability to remove pyrimidine dimers from their DNA, although there are at least four genetically distinct classes as determined by complementation tests on fused cells (3)(4)(5)(6)(7)(8). These classes also differ in their levels of unscheduled DNA synthesis and repair replication (14).…”

Section: Resultsmentioning

confidence: 99%

“…Recently, complementation studies have shown that there are several genetically different forms of XP, all deficient in excision-repair (3)(4)(5)(6)(7)(8). In addition there is a further class of XP patients (termed "XP variants" in this communication) which, while exhibiting the usual clinical symptoms, seem to be completely normal in excision-repair of pyrimidine dimers (9)(10)(11)(12)(13)(14).…”

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confidence: 99%

Xeroderma pigmentosum cells with normal levels of excision repair have a defect in DNA synthesis after UV-irradiation.

Lehmann¹,

Kirk-Bell²,

Arlett³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

523

241

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Cells cultured from most patients suffering from the sunlight-sensitive hereditary disorder xeroderma pigmentosum are defective in the ability to excise ultraviolet light (UV)-induced pyrimidine dimers from their DNA. There is, however,-one class of these patients whose cells are completely normal in this excision repair process. We have found that these cells have an abnormality in the manner in which DNA is synthesized after UVirradiation. The time taken to convert initially lowmolecular-weight DNA synthesized in UV-irradiated cells into high-molecular-weight DNA similar in size to that in untreated cells is much greater in these variants than in normal cells. Furthermore, this slow conversion of low to high-molecular-weight newly synthesized DNA is drastically inhibited by caffeine, which has no effect in normal cells. Recently, complementation studies have shown that there are several genetically different forms of XP, all deficient in excision-repair (3)(4)(5)(6)(7)(8). In addition there is a further class of XP patients (termed "XP variants" in this communication) which, while exhibiting the usual clinical symptoms, seem to be completely normal in excision-repair of pyrimidine dimers (9-14). All XP lines examined have normal rates of rejoining of DNA single-strand breaks induced by ionizing radiation (14).Despite very low levels of excision-repair in cells from most XP patients (and also in rodent cell lines), they can nevertheless tolerate the production in their DNA of over 105 pyrimi- In this communication we show that fibroblast cultures from three XP variants have normal levels of excision-repair, but are abnormal in postreplication repair. After UV-irradiation, the time taken for the newly synthesized DNA to attain a high molecular weight similar to that in unirradiated controls is much longer than in normal cells. Furthermore, this conversion of low-to high-molecular weight DNA is drastically inhibited by caffeine, which has very little effect in normal human cells. MATERIALS AND METHODSCell Lines used in these experiments were primary fibroblasts from healthy donors and XP patients listed in Table 1.Excision of Pyrimidine Dimers Measured by Loss of UVEndonuclease-Susceptible Sites. This procedure has been described in detail (24). Briefly; fibroblast cells cultured as described in ref. 24 were labeled with [3H]thymidine, UVirradiated, and incubated in the absence of radioactive label for various times. They were then mixed with an equal volume of unirradiated cells whose DNA had been labeled with [14C]-dT. DNA was extracted from the mixed cell population and incubated with or without the UV-specific endonuclease from Micrococcus luteus, which'specifically nicks DNA near pyrimidine dimers (24,25). The DNA products resulting from enzymic attack were centrifuged through 5-20% alkaline sucrose gradients at 40,000 rpm for 135 min at 210 in an SW56 rotor. After centrifugation, fractions were collected, radioactivity was determined, and the weight-average molecular weight of the DNA distributions ...

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“…1985) (table 5) . Further work demonstrated that these cellular fusion products are also capable of repair replication, reactivation of UV-irradiated viruses and loss of endonuclease-sensitive sites at close to normal levels (De WeerdKastelein et , Paterson et al 1974, Day et al 1975 .…”

Section: Int J Radiat Biol Downloaded From Informahealthcarecom By Qmentioning

confidence: 97%

The Molecular Genetics of the Incision Step in the DNA Excision Repair Process

Rubin

1988

International Journal of Radiation Biology

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This review describes the evolution of research into the genetic basis of how different organisms use the process of excision repair to recognize and remove lesions from their cellular DNA. One particular aspect of excision repair, DNA incision, and how it is controlled at the genetic level in bacteriophage, bacteria, S. cerevisae, D. melanogaster, rodent cells and humans is examined. In phage T4, DNA is incised by a DNA glycosylase-AP endonuclease that is coded for by the denV gene. In E. coli, the products of three genes, uvrA, uvrB and uvrC, are required to form the UVRABC excinuclease that cleaves DNA and releases a fragment 12-13 nucleotides long containing the site of damage. In S. cerevisiae, genes complementing five mutants of the RAD3 epistasis group, rad1, rad2, rad3, rad4 and rad10 have been cloned and analyzed. Rodent cells sensitive to a variety of mutagenic agents and deficient in excision repair are being used in molecular studies to identify and clone human repair genes (e.g. ERCC1) capable of complementing mammalian repair defects. Most studies of the human system, however, have been done with cells isolated from patients suffering from the repair defective, cancer-prone disorder, xeroderma pigmentosum, and these cells are now beginning to be characterized at the molecular level. Studies such as these that provide a greater understanding of the genetic basis of DNA repair should also offer new insights into other cellular processes, including genetic recombination, differentiation, mutagenesis, carcinogenesis and aging.

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DNA Repair Monitored by an Enzymatic Assay in Multinucleate Xeroderma Pigmentosum Cells after Fusion

Cited by 21 publications

References 13 publications

National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014, USA.

National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014, USA.

Xeroderma pigmentosum cells with normal levels of excision repair have a defect in DNA synthesis after UV-irradiation.

The Molecular Genetics of the Incision Step in the DNA Excision Repair Process

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