scholarly journals Lesions induced in DNA by ultraviolet light are repaired at the nuclear cage

1984 ◽  
Vol 70 (1) ◽  
pp. 189-196
Author(s):  
S.J. McCready ◽  
P.R. Cook
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Nuclear Matrix ◽  
Ultraviolet Irradiation ◽  
Mammalian Cells ◽  
Nuclear Dna ◽  
S Phase ◽  
Unscheduled Dna Synthesis ◽  
Phase Synthesis

In mammalian cells, S-phase DNA synthesis occurs at sites fixed to a sub-nuclear structure, the nuclear matrix or cage. This is an ordered network of non-histone proteins, which maintains its essential morphology even in the absence of DNA. We show here that unscheduled DNA synthesis following exposure of HeLa cells to ultraviolet light also takes place at this sub-structure. We also show that ultraviolet irradiation grossly reorganizes nuclear DNA, arresting S-phase synthesis at the cage and leaving the residual synthesis highly localized.

Effects of ultraviolet light on synchronized Chinese hamster ovary cells; potentiation by hydroxyurea

1977 ◽  
Vol 28 (1) ◽  
pp. 29-48
Author(s):  
K. Burg ◽  
A.R. Collins ◽  
R.T. Johnson
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Chinese Hamster Ovary ◽  
Ultraviolet Irradiation ◽  
Chromosome Structure ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells

We have examined the effects of hydroxyurea on u.v.-irradiated Chinese hamster CHO-KI cells. Ultraviolet irradiation followed by incubation with hydroxyurea causes only slight disruption of DNA and chromosome structure in CHO-KI cells compared with HeLa cells. There is, however, a clear potentiation by hydroxyurea of the u.v. killing of CHO-KI cells, which is most pronounced at those points in the cycle which are reported to have small DNA precursor pools. This potentiation is reduced when DNA precursors are provided together with hydroxyurea. These data are discussed in terms of an uncoupling of excision and repair DNA synthesis.

Measurement of unscheduled DNA synthesis and S-phase synthesis in rodent hepatocytes following in vivo treatment: Testing of 24 compounds

1989 ◽  
Vol 14 (3) ◽  
pp. 155-164 ◽  
Author(s):  
Jon C. Mirsalis ◽  
C. Kim Tyson ◽  
Karen L. Steinmetz ◽  
Erica K. Loh ◽  
Carol M. Hamilton ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
S Phase ◽  
Unscheduled Dna Synthesis ◽  
Phase Synthesis ◽  
In Vivo Treatment

Changes in the organization of chromosomes during the cell cycle: response to ultraviolet light

1975 ◽  
Vol 17 (3) ◽  
pp. 539-565
Author(s):  
S.L. Schor ◽  
R.T. Johnson ◽  
C.A. Waldren
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Close Correlation ◽  
Chromosome Condensation ◽  
Unscheduled Dna Synthesis ◽  
Interphase Chromosome ◽  
Interphase Cells ◽  
Chromosome Decondensation

Fusion between mitotic and interphase cells results in the premature condensation of the interphase chromosomes into a morphology related to the position in the cell cycle at the time of fusion. These prematurely condensed chromosomes (PCC) have been used in conjunction with u.v. irradiation to examine the interphase chromosome condensation cycle of HeLa cells. The following observations have been made: (I) There is a progressive decondensation of the chromosomes during G1 which is accentuated by u.v. irradiation: (2) The chromosomes become more resistant to u.v.-induced decondensation during G2 and mitosis. (3) There is a close correlation between the degree of chromosome decondensation and the amount of unscheduled DNA synthesis induced by u.v. irradiation during G1 and mitosis: (4) Hydroxyurea enhances the ability of u.v. irradiation to promote the decondensation of chromosomes during G1, G2 and mitosis. Hydroxyurea also potentiates the lethal action of u.v. irradiation during mitosis and G1. These data are discussed in relation to the suggestion that chromosomes undergo a progressive decondensation during G1 and condensation during G2.

scholarly journals Differential Effect of Ethidium Bromide and Cytosine Arabinoside on Mitochondrial and Nuclear DNA Synthesis in HeLa Cells

1972 ◽  
Vol 27 (8) ◽  
pp. 989-991 ◽  
Author(s):  
Kenzo Kato ◽  
Klaus D. Radsak ◽  
Hilary Koprowski
Keyword(s):  
Hela Cell ◽  
Dna Synthesis ◽  
Ethidium Bromide ◽  
Hela Cells ◽  
Cytosine Arabinoside ◽  
Differential Effect ◽  
Mammalian Cells ◽  
Nuclear Dna ◽  
Circular Dna ◽  
Isopycnic Centrifugation

The effect of ethidium bromide (EB) on the synthesis of circular DNA of mammalian cells was studied by isopycnic centrifugation in a CsCl-EB solution. EB (0.1—0.5 μg/ml) interferes with the synthesis of newly-formed circular DNA of HeLa cell mitochondria and causes degradation of the pre-existing circular DNA, as well. Under the same conditions, nuclear DNA synthesis was not inhibited. This effect was not reversible at a concentration of 0.5 μg EB/ml or more. Cytosine arabinoside (ara-C) did not exhibit an effect similar to that of EB.

The influence of acridine dyes and caffeine on recovery from ultraviolet damage in Eudorina elegans

1975 ◽  
Vol 21 (11) ◽  
pp. 1849-1854 ◽  
Author(s):  
C. L. Kemp ◽  
K. M. Malloy
Keyword(s):  
Dna Synthesis ◽  
Acridine Orange ◽  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Repair Process ◽  
Repair System ◽  
Acridine Dyes ◽  
Dark Survival ◽  
High Doses ◽  
Ultraviolet Damage

Caffeine and the acridine dyes, acridine orange and acriflavine, were used to examine the repair potential in Eudorina elegans following ultraviolet irradiation. Acridines blocked photoreactivation primarily as a result of absorption of photoreactivating wavelengths, but acridines did not influence dark survival. Therefore, an acridine-sensitive excision–resynthesis–repair process is absent in Eudorina.Caffeine decreased both dark and light survival, the latter only after relatively high doses of ultraviolet light were used for inactivation. The caffeine-sensitive repair process appears to function most actively when the organisms are engaged in DNA synthesis, indicating that a postreplication–repair system exists in Eudorina. However, the data suggest that a repair system not associated with the DNA synthetic phases may also exist.

scholarly journals LIMITED DNA SYNTHESIS IN THE ABSENCE OF PROTEIN SYNTHESIS IN PHYSARUM POLYCEPHALUM

1966 ◽  
Vol 31 (3) ◽  
pp. 577-583 ◽  
Author(s):  
J. E. Cummins ◽  
H. P. Rusch
Keyword(s):  
Protein Synthesis ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Physarum Polycephalum ◽  
Nuclear Dna ◽  
S Phase ◽  
Early Prophase ◽  
Late Prophase ◽  
Removal Experiments ◽  
Inhibitor Of Protein Synthesis

Actidione (cycloheximide), an antibiotic inhibitor of protein synthesis, blocked the incorporation of leucine and lysine during the S phase of Physarum polycephalum. Actidione added during the early prophase period in which mitosis is blocked totally inhibited the initiation of DNA synthesis. Actidione treatment in late prophase, which permitted mitosis in the absence of protein synthesis, permitted initiation of a round of DNA replication making up between 20 and 30% of the unreplicated nuclear DNA. Actidione treatment during the S phase permitted a round of replication similar to the effect at the beginning of S. The DNA synthesized in the presence of actidione was replicated semiconservatively and was stable through at least the mitosis following antibiotic removal. Experiments in which fluorodeoxyuridine inhibition was followed by thymidine reversal in the presence of actidione suggest that the early rounds of DNA replication must be completed before later rounds are initiated.

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