scholarly journals Deoxyguanosine enhances the cytotoxicity of the topoisomerase I inhibitor camptothecin by reducing the repair of double-strand breaks induced in replicating DNA

1991 ◽  
Vol 100 (4) ◽  
pp. 883-893 ◽  
Author(s):  
S. Squires ◽  
A.J. Ryan ◽  
H.L. Strutt ◽  
P.J. Smith ◽  
R.T. Johnson
Keyword(s):  
Topoisomerase I ◽  
S Phase ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Pulse Field ◽  
Dependent Manner ◽  
Chromosomal Dna ◽  
Dna Breaks ◽  
Strand Breaks ◽  
Single Strand Breaks

Deoxyguanosine (dG) enhances the S phase cytotoxicity of camptothecin (CPT), a topoisomerase I (topo I) inhibitor, but by contrast does not affect the toxicity of VM26, a topoisomerase II inhibitor. The 80% survival of S phase human fibroblasts after a 60 min exposure to 0.2 microM CPT is reduced by half in the presence of 25 microM dG. G1 cells are resistant to CPT toxicity, though the levels of the single-strand DNA breaks induced by the drug are similar in G1 and S phase cells. Higher concentrations of dG retard the recovery of RNA and DNA synthesis and inhibit recovery from the S-G2 cycle block after CPT removal. At 100 microM dG the number of CPT-induced protein-linked single-strand DNA breaks is almost doubled, suggestive of a direct effect of dG on the cellular activity of topo I. In the presence or absence of dG, single-strand breaks disappear within minutes of the removal of CPT. We found that the inhibition of topo I by CPT induces the formation of double as well as single-strand breaks in the chromosomal DNA. Previously we have shown, using a pulse-field gel electrophoresis technique, that the double-strand breaks (DSBs) are generated predominantly at sites of replication and not in the bulk DNA. A number of these DSBs are long-lived. The present study shows that dG affects the repair of these DSBs in a dose-dependent manner, and that a higher proportion of the initial lesions induced in nascent DNA remain 24 h after removal of CPT. We suggest that the long-lived double-strand breaks, formed in replicating DNA at the time of CPT exposure, are the lethal drug-induced lesions, which explains both the selective cytotoxicity of CPT towards S phase cells and the enhancement of CPT cytotoxicity by dG.

scholarly journals From single-strand breaks to double-strand breaks during S-phase: a new mode of action of theEscherichia coli Cytolethal Distending Toxin

2012 ◽  
Vol 15 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Y. Fedor ◽  
J. Vignard ◽  
M.-L. Nicolau-Travers ◽  
E. Boutet-Robinet ◽  
C. Watrin ◽  
...  
Keyword(s):  
Mode Of Action ◽  
S Phase ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Cytolethal Distending Toxin ◽  
Strand Breaks ◽  
Single Strand Breaks

scholarly journals DNA DAMAGE AND REPAIR IN EUKARYOTIC CELLS

Genetics ◽  
1974 ◽  
Vol 78 (1) ◽  
pp. 139-148
Author(s):  
R B Painter
Keyword(s):  
Ionizing Radiation ◽  
Excision Repair ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Premature Aging ◽  
Cross Linking ◽  
Base Damage ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Post Replication Repair

ABSTRACT Damage in DNA after irradiation can be classified into five kinds: base damage, single-strand breaks, double-strand breaks, DNA-DNA cross-linking, and DNA-protein cross-linking. Of these, repair of base damage is the best understood. In eukaryotes, at least three repair systems are known that can deal with base damage: photoreactivation, excision repair, and post-replication repair. Photoreactivation is specific for UV-induced damage and occurs widely throughout the biosphere, although it seems to be absent from placental mammals. Excision repair is present in prokaryotes and in animals but does not seem to be present in plants. Post-replication repair is poorly understood. Recent reports indicate that growing points in mammalian DNA simply skip past UV-induced lesions, leaving gaps in newly made DNA that are subsequently filled in by de novo synthesis. Evidence that this concept is oversimplified or incorrect is presented.—Single-strand breaks are induced by ionizing radiation but most cells can rapidly repair most or all of them, even after supralethal doses. The chemistry of the fragments formed when breaks are induced by ionizing radiation is complex and poorly understood. Therefore, the intermediate steps in the repair of single-strand breaks are unknown. Double-strand breaks and the two kinds of cross-linking have been studied very little and almost nothing is known about their mechanisms for repair.—The role of mammalian DNA repair in mutations is not known. Although there is evidence that defective repair can lead to cancer and/or premature aging in humans, the relationship between the molecular defects and the diseased state remains obscure.

Matching of single-strand breaks to form double-strand breaks in DNA

Biopolymers ◽  
1969 ◽  
Vol 7 (5) ◽  
pp. 681-693 ◽  
Author(s):  
David Freifelder ◽  
Bruce Trumbo
Keyword(s):  
Double Strand Breaks ◽  
Single Strand ◽  
Strand Breaks ◽  
Single Strand Breaks

scholarly journals Artificial and Solar UV Radiation Induces Strand Breaks and Cyclobutane Pyrimidine Dimers in Bacillus subtilis Spore DNA

2000 ◽  
Vol 66 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Tony A. Slieman ◽  
Wayne L. Nicholson
Keyword(s):  
Bacillus Subtilis ◽  
Uv Irradiation ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Complex Spectrum ◽  
Cyclobutane Pyrimidine Dimers ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Pyrimidine Dimers ◽  
Solar Uv

ABSTRACT The loss of stratospheric ozone and the accompanying increase in solar UV flux have led to concerns regarding decreases in global microbial productivity. Central to understanding this process is determining the types and amounts of DNA damage in microbes caused by solar UV irradiation. While UV irradiation of dormant Bacillus subtilis endospores results mainly in formation of the “spore photoproduct” 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221–2227, 1996). We examined the occurrence of double-strand breaks, single-strand breaks, cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore DNA under several UV irradiation conditions by using enzymatic probes and neutral or alkaline agarose gel electrophoresis. DNA from spores irradiated with artificial 254-nm UV-C radiation accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, while DNA from spores exposed to artificial UV-B radiation (wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and UV-A radiation) accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to sunlight from which the UV-B component had been removed with a filter (“UV-A sunlight”) accumulated only single-strand breaks and double-strand breaks. Apurinic-apyrimidinic sites were not detected in spore DNA under any of the irradiation conditions used. Our data indicate that there is a complex spectrum of UV photoproducts in DNA of bacterial spores exposed to solar UV irradiation in the environment.

scholarly journals Manipulating chromosome structure and metaphase status with ultraviolet light and repair synthesis inhibitors

1985 ◽  
Vol 73 (1) ◽  
pp. 159-186
Author(s):  
A.M. Mullinger ◽  
R.T. Johnson
Keyword(s):  
Simian Virus 40 ◽  
Human Cells ◽  
Single Strand ◽  
Dna Breaks ◽  
Intact Cells ◽  
Repair Synthesis ◽  
Single Strand Break ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Chromosome Decondensation

DNA repair occurs in metaphase-arrested cells in response to ultraviolet irradiation. In the presence of the repair synthesis inhibitors hydroxyurea and 1-beta-D-arabinofuranosylcytosine the chromosomes of such cells, as seen in Carnoy-fixed preparations, are decondensed. The extent of decondensation is related to both the u.v. dose and the duration of incubation in the presence of inhibitors. For any particular cell type there is a reasonable correlation between the amount of decondensation and the number of single-strand DNA breaks generated by the repair process under the same inhibitory conditions, though the chromosome changes continue after the number of single-strand breaks has reached a plateau. The dose response of chromosome decondensation varies between different cell types but is in general correlated with differences in levels of single-strand breaks accumulated under comparable inhibitory conditions. Decondensation can be detected after 0.5 Jm-2 in repair-competent human cells. In human cells defective in excision repair there is much less chromosome decondensation in response to the same u.v. dose and time of repair inhibition. However, a simian virus 40-transformed muntjac cell displays pronounced chromosome decondensation but has limited incision ability. Both chromosome decondensation and single-strand break accumulation in the presence of inhibitors are reversed when DNA precursors are provided, but reversal after higher u.v. doses and longer periods of incubation leads to recondensed chromosomes that are fragmented. Elution of the DNA from such cells through polycarbonate filters under non-denaturing conditions reveals that double-strand DNA breaks are generated during the period of incubation with inhibitors. Although the chromosomes of repair-inhibited metaphase cells are decondensed in fixed preparations, their morphology appears normal in intact cells. The cells also retain a capacity to induce prematurely condensed chromosomes (PCC) when fused with interphase cells: compared with control mitotic cells, the speed of induction is sometimes reduced but the final amount of PCC produced is similar.

scholarly journals Novel approach reveals genomic landscapes of single-strand DNA breaks with nucleotide resolution in human cells

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Huifen Cao ◽  
Lorena Salazar-García ◽  
Fan Gao ◽  
Thor Wahlestedt ◽  
Chun-Lin Wu ◽  
...  
Keyword(s):  
Regulatory Elements ◽  
Single Strand ◽  
Dna Breaks ◽  
Strand Breaks ◽  
Template Strand ◽  
Naturally Occurring ◽  
Single Strand Breaks ◽  
Novel Approach ◽  
Genome Wide ◽  
Nucleotide Resolution

AbstractSingle-strand breaks (SSBs) represent the major form of DNA damage, yet techniques to map these lesions genome-wide with nucleotide-level precision are limited. Here, we present a method, termed SSiNGLe, and demonstrate its utility to explore the distribution and dynamic changes in genome-wide SSBs in response to different biological and environmental stimuli. We validate SSiNGLe using two very distinct sequencing techniques and apply it to derive global profiles of SSBs in different biological states. Strikingly, we show that patterns of SSBs in the genome are non-random, specific to different biological states, enriched in regulatory elements, exons, introns, specific types of repeats and exhibit differential preference for the template strand between exons and introns. Furthermore, we show that breaks likely contribute to naturally occurring sequence variants. Finally, we demonstrate strong links between SSB patterns and age. Overall, SSiNGLe provides access to unexplored realms of cellular biology, not obtainable with current approaches.

UV-induzierte Brüche in 5-Bromuracil-substituierter DNS des Phagen T1 / UV-Induced Strand Breaks in 5-Bromouracil Substituted DNA of Phage T1

1970 ◽  
Vol 25 (9) ◽  
pp. 1037-1042 ◽  
Author(s):  
G. Stephan ◽  
H. G. Miltenburger ◽  
G. Hotz
Keyword(s):  
Biological Activity ◽  
Uv Irradiation ◽  
Uv Light ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Radical Scavenger ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Phage Dna ◽  
Site Of Action

Phage Tl and BU-Τ1 (phage DNA substituted with 5-bromouracil) were inactivated by UV-light (2537 A). After irradiation DNA was extracted and its sedimentation behaviour studied by zone centrifugation in neutral and alkaline sucrose gradients, respectively. In the DNA of unsubstituted phage no double-strand breaks and only a small number of single-strand breaks per inactivation dose could be detected after high UV-doses. However, after irradiation of phage BU-T1 double- and single-strand breaks were observed at an increased rate. UV-irradiation in the presence of a radical scavenger (0.01 M cysteamine) prevented the occurrence of double- but not of single strand breaks. The relevance of these breaks attributable to BU-incorporation for the biological activity (plaque forming ability) of the phage and the site of action of cysteamine are discussed.

Change in DNA after Exposure to Hydrogen Atoms.

1969 ◽  
Vol 24 (12) ◽  
pp. 1565-1573 ◽  
Author(s):  
H. Jung, ◽  
U. Hagen, ◽  
M. Ullrich, ◽  
E. E. Petersen
Keyword(s):  
Hydrogen Bonds ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Dna Double Strand Breaks ◽  
Hydrogen Atoms ◽  
Γ Irradiation ◽  
Base Damage ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Single Breaks

The action of hydrogen atoms — generated in an electrodeless high frequency gas discharge — on calf thymus DNA in aqueous solution was investigated. The loss of priming activity was compared with the appearance of single strand breaks in native and denatured DNA, double strand breaks, denatured zones, base damage and rupture of hydrogen bonds. The primary lesions after exposure to H atoms and gamma radiation, respectively, are single strand breaks and base damage. Double strand breaks originating from accumulation of single breaks, and rupture of hydrogen bonds caused by single breaks and base damage, were identified as secondary lesions. In relation to strand breaks arising from radical attack on the sugar-phosphate backbone of the DNA molecule, base damage is about 12.5 times more frequent after Η-exposure than after γ-irradiation. It is concluded from this observation, that single strand breaks are the predominant critical lesions responsible for the loss of the functional activity of DNA.

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