The Induction of Thymine Dimers by U.V. Light as a Function of Cell Stage

Clarkson, Judith M.

doi:10.1080/09553007814551261

Cited by 11 publications

(2 citation statements)

References 19 publications

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“…Results from assays that measured the induction and removal of lesions from synchronous cells irradiated throughout the cell cycle yielded similar results to those from asynchronous V-79 cells (Table 1). These results confirm the results of Clarkson (1978), who found no alteration in the number of lesions induced throughout the CHO cell cycle. These data extend the results of Clarkson (1978) in that they show no alterations in the extent of excision as a function of position in the cell cycle at the time of irradiation.…”

Section: Hours Post Treatmentsupporting

confidence: 92%

“…These results confirm the results of Clarkson (1978), who found no alteration in the number of lesions induced throughout the CHO cell cycle. These data extend the results of Clarkson (1978) in that they show no alterations in the extent of excision as a function of position in the cell cycle at the time of irradiation. Kaufman et al (1980) and Kaufman and Cleaver (1981) demonstrated an inhibition of replicon initiation events occurred in human cells exposed to low levels of UV light (<2 J/m2) using velocity sedimentation in alkaline sucrose gradients.…”

Section: Hours Post Treatmentsupporting

confidence: 92%

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Recovery of Subchromosomal Dna Synthesis in Synchronous V‐79 Chinese Hamster Cells After Ultraviolet Light Exposure

Meechan

Carpenter

Griffiths

1986

Photochem & Photobiology

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Abstract— Previous work obtained from Chinese hamster V‐79 cells indicated that, immediately following exposure, UV‐induced lesions acted as blocks to elongation of nascent strands, but gradually lost that ability over a 10 h period after exposure to 10 J/m2. The work reported herein attempted to examine possible cell cycle mediated alterations in the recovery of DNA synthesis. Kinetic incorporation of radiolabeled thymidine studies indicated that there may have been a more rapid recovery of DNA synthesis in cells irradiated in G1 or G2vs cells irradiated in S phase. DNA fiber autoradiograms prepared from synchronous cells indicated that after irradiation in any phase of the cell cycle, the length of newly synthesized DNA was equal to control lengths 1 h after exposure to 5.0 J/m2 (or 1 h after entering S phase for cells irradiated in G1 or G2). This observed recovery was not solely due to an excision process. No cell cycle mediated difference in the number of dimers induced or removed as a function of cell cycle position was observed. These results appear to be consistent with a continuum of effects, with initiation effects dominating the response at low fluences, gapped synthesis at intermediate fluences and elongation inhibition at high fluences. The fluences at which each event dominates may be cell‐line specific.

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Section: Hours Post Treatmentsupporting

confidence: 92%

Section: Hours Post Treatmentsupporting

confidence: 92%

Recovery of Subchromosomal Dna Synthesis in Synchronous V‐79 Chinese Hamster Cells After Ultraviolet Light Exposure

Meechan

Carpenter

Griffiths

1986

Photochem & Photobiology

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Cell cycle‐related variations in UV damage and repair capacity in chinese hamster (CHO‐K1) cells

Collins

Downes

Johnson

1980

Journal Cellular Physiology

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UV damage to CHO cell DNA, measured by formation of thymine-containing dimers, increases from mitosis to early S phase. Computer simulation of UV absorption by the DNA of an idealized CHO cell at different stages in the cell cycle resembles the cycle dependence of UV damage. Incision at UV damage sites, measured by the accumulation of breaks in preexisting DNA during 30 minutes' post-irradiation incubation with the DNA synthesis inhibitors 1-beta-D arabinofuranosylcytosine and hydroxyurea, increases from mitosis to interphase. Analysis of the dose dependence of DNA break accumulation indicates that both the affinity of the endonuclease for dimer sites and the maximum enzyme activity at saturating levels of dimers are significantly lower in mitosis than in interphase. The killing of CHO cells by UV is enhanced if repair is temporarily inhibited by are C. The DNA gyrase inhibitor novobiocin prevents UV-induced incision.

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DNA supercoiling and repair in peripheral lymphocytes as a measure of acute radiation response after radiotherapy

Rosemann

Schulze²,

Abel³

1994

Radation Oncology Invest

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DNA supercoiling density and incision kinetics during ultraviolet (UV) excision repair hav been measured in lymphocytes from 20 cancer patients and 17 healthy donors. Nucleoid sedimentation was used, which allows the sensitive detection of both DNA damage and alterations in chromatin structure. The release of DNA supercoiling after ethidium bromide intercalation and the kinetics of the incision step following UV irradiation were compared in lymphocytes derived from cancer patients and those from normal donors. The classification into lymphocytes with normal or reduced repair and normal or altered supercoiling, respectively, revealed that reduced repair as well as altered chromatin structure occurred more frequently in lymphocytes derived from patients (40% and 85%, respectively) than in those from healthy donors (35% and 23%, respectively). Even more striking was the simultaneous occurrence of both characteristics in tumor patients: in 34% of all cases reduced repair was associated with altered supercoiling density, whereas among healthy donors this association occurred in only 18% of all cases. Supercoiling density may be related to functional integrity of lymphocytes and repair capacity to recovery after radiation damage. Since both parameters are important for the radiation response of normal tissue, we consider these measurements a potential prognostic assay aimed at reducing acute reaction of the normal tissue.

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The Induction of Thymine Dimers by U.V. Light as a Function of Cell Stage

Cited by 11 publications

References 19 publications

Recovery of Subchromosomal Dna Synthesis in Synchronous V‐79 Chinese Hamster Cells After Ultraviolet Light Exposure

Recovery of Subchromosomal Dna Synthesis in Synchronous V‐79 Chinese Hamster Cells After Ultraviolet Light Exposure

Cell cycle‐related variations in UV damage and repair capacity in chinese hamster (CHO‐K1) cells

DNA supercoiling and repair in peripheral lymphocytes as a measure of acute radiation response after radiotherapy

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