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1.
J Phys Chem B ; 121(39): 9169-9174, 2017 10 05.
Article in English | MEDLINE | ID: mdl-28892627

ABSTRACT

The UVB irradiation of DNA labeled with 5-bromo-2'-deoxyuridine (BrdU) leads to single-strand breaks (SSBs) as a major photochemical damage. Some time ago, we demonstrated that SSB is a secondary damage forming due to thermal dissociation of 2'-deoxyribonolactone generated photochemically in DNA labeled with BrdU. For the first time, we study here the variation of the yield of UVB generated SSBs with the alteration of 3'-neighbor nucleobase of electron donor (2'-deoxyguanine (dG)) and acceptor (excited BrdU) in double-stranded DNA. We showed that the experimental damage yields can be explained by the calculated ionization potentials of dG and electron affinities of excited BrdU via a kinetic scheme based on the Marcus model of electron transfer (ET). Hence, our studies on the sequence dependence of photochemical damage in DNA labeled with BrdU constitute a further argument that photochemically generated SSBs occur as a result of long-range ET.


Subject(s)
Bromodeoxyuridine/radiation effects , DNA/radiation effects , Electrons , Light , DNA Damage/radiation effects , Electron Transport , Models, Biological
2.
Photochem Photobiol ; 79(2): 145-51, 2004 Feb.
Article in English | MEDLINE | ID: mdl-15068027

ABSTRACT

Mutagenic and carcinogenic UV-B radiation is known to damage DNA mostly through the formation of bipyrimidine photoproducts, including cyclobutane dimers (CPD) and (6-4) photoproducts ((6-4) PP). Using high-performance liquid chromatography coupled to tandem mass spectrometry, we investigated the formation and repair of thymine-thymine (TT) and thymine-cytosine (TC) CPD and (6-4) PP in the DNA of cultured human dermal fibroblasts. A major observation was that the rate of repair of the photoproducts did not depend on the identity of the modified pyrimidines. In addition, removal of CPD was found to significantly decrease with increasing applied UV-B dose, whereas (6-4) PP were efficiently repaired within less than 24 h, irrespective of the dose. As a result, a relatively large amount of CPD remained in the genome 48 h after the irradiation. Because the overall applied doses (<500 J m(-2)) were chosen to induce moderate cytotoxicity, fibroblasts could recover their proliferation capacities after transitory cell cycle arrest, as shown by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation and flow cytometry analysis. It could thus be concluded that UV-B-irradiated cultured primary human fibroblasts normally proliferate 48 h after irradiation despite the presence of high levels of CPD in their genome. These observations emphasize the role of CPD in the mutagenic effects of UV-B.


Subject(s)
DNA Damage , Pyrimidine Dimers/metabolism , Bromodeoxyuridine/analysis , Bromodeoxyuridine/metabolism , Bromodeoxyuridine/radiation effects , Cell Division/radiation effects , Cells, Cultured , Chromatography, High Pressure Liquid , DNA/metabolism , DNA/radiation effects , DNA Repair , Dose-Response Relationship, Radiation , Fibroblasts , Humans , Mass Spectrometry , Mutagenesis/radiation effects , Pyrimidine Dimers/analysis , Pyrimidine Dimers/radiation effects , Time Factors , Ultraviolet Rays
3.
Int J Radiat Biol ; 78(11): 953-66, 2002 Nov.
Article in English | MEDLINE | ID: mdl-12456283

ABSTRACT

PURPOSE: To estimate the enhancement of DNA strand breaks induced by low linear energy transfer (LET) radiation in the presence of halogenated pyrimidines and to examine complexity and clustering properties of damage that could provide a correlation between DNA damage and lethality. MATERIALS AND METHODS: Monte Carlo track structure methods were used to model and estimate the induction of strand breakage by X-ray photons with and without the incorporated Br/I deoxyuridine in cell-mimetic conditions. The increase of DNA strand break induction was modelled by taking into account the direct energy deposition and the reactions of radicals. The yield and spectrum of strand breaks were calculated at various degrees of Br/IdU incorporation. The excess strand breaks due to Br/IdU incorporation was assumed to be induced by highly reactive uracilyl radicals. Four mechanisms were considered for the production of uracilyl radicals classified into three groups, by hydrated electrons, by direct energy deposition, and by both hydrated electrons and direct energy depositions. In total, nine different models were considered to test the excess strand breaks by incorporated Br/IdU assuming different pathways. RESULTS: Model calculations show the following: the yield of strand breaks is enhanced by both the e(aq)(-) reaction and the direct energy deposition on base moiety; there is a significant contribution to the enhancement of yield of strand breaks due to energy transfer about four bases along the DNA to Br/IdU and DNA strand break complexity increases with degree of Br/IdU incorporation. Enhancement ratios of 1.8 and 2.5 for 40% Br/IdU substitution were obtained for single- and double-strand breaks, respectively. CONCLUSIONS: The increase in the yield of strand breaks due to Br/IdU incorporation could be explained by the mechanism of uracilyl radical production by e(aq)(-) and direct energy deposition. The importance of energy transfer along the DNA is demonstrated. It is shown that the incorporation of Br/IdU causes a spectral shift towards a greater complexity of clustered DNA damage.


Subject(s)
Bromodeoxyuridine/radiation effects , Computer Simulation , DNA/radiation effects , Idoxuridine/radiation effects , Models, Chemical , Base Sequence , Bromodeoxyuridine/chemistry , Chromosome Breakage , DNA/chemistry , DNA Damage , Dose-Response Relationship, Radiation , Free Radicals/chemistry , Idoxuridine/chemistry , Linear Energy Transfer , Models, Molecular , Molecular Sequence Data , Monte Carlo Method , Radiation Tolerance , Uracil/chemistry , Uracil/radiation effects , Water/chemistry
4.
J Immunol Methods ; 264(1-2): 89-93, 2002 Jun 01.
Article in English | MEDLINE | ID: mdl-12191513

ABSTRACT

A recently developed technology for the non-enzymatic detection of the thymidine analog 5-bromo-2-deoxyuridine (BrdU) has been evaluated. In contrast to previous enzymatic approaches, Ultraviolet-Induced Detection (UVID) of halogenated pyrimidines allows for a mild detection procedure which enables the simultaneous detection of cellular markers and DNA-synthesis without enzyme-specific disadvantages. Superantigen-stimulated peripheral blood mononuclear cells (PBMNCs) have been treated with two different inhibitors of proliferation and the cell cycle of different lymphocyte subsets has been analysed. Both pentoxifylline (POF) and 2-methoxyestradiol (2ME2) exhibited strong antiproliferative activity, but led to distinctive changes in the cell cycle distribution. This study shows that the UVID technology is a simple and viable method which should find a wide range of applications in immunological and pharmacodynamic assays.


Subject(s)
Bromodeoxyuridine/analysis , Cell Culture Techniques/methods , Estradiol/analogs & derivatives , Immunophenotyping/methods , Lymphocyte Subsets/cytology , Lymphocyte Subsets/drug effects , 2-Methoxyestradiol , Antigens, CD19/biosynthesis , Bromodeoxyuridine/radiation effects , CD4-Positive T-Lymphocytes/cytology , CD4-Positive T-Lymphocytes/drug effects , CD4-Positive T-Lymphocytes/metabolism , CD4-Positive T-Lymphocytes/radiation effects , CD8-Positive T-Lymphocytes/cytology , CD8-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/metabolism , CD8-Positive T-Lymphocytes/radiation effects , Cell Division/drug effects , Cell Division/immunology , Cell Division/radiation effects , Cells, Cultured , DNA/antagonists & inhibitors , DNA/biosynthesis , Estradiol/pharmacology , G1 Phase/drug effects , G1 Phase/radiation effects , Growth Inhibitors/pharmacology , Humans , Lymphocyte Count , Lymphocyte Subsets/metabolism , Lymphocyte Subsets/radiation effects , Pentoxifylline/pharmacology , Resting Phase, Cell Cycle/drug effects , Resting Phase, Cell Cycle/radiation effects , Ultraviolet Rays
5.
Chem Biol ; 6(7): 451-9, 1999 Jul.
Article in English | MEDLINE | ID: mdl-10381405

ABSTRACT

BACKGROUND: 5-Bromodeoxyuridine is a radiosensitizing agent that is currently being evaluated in clinical trials as an adjuvant in the treatment of a variety of cancers. gamma-Radiolysis and UV irradiation of oligonucleotides containing 5-bromodeoxyuridine result in the formation of direct strand breaks at the 5'-adjacent nucleotide by oxidation of the respective deoxyribose. We investigated the effects of DNA secondary structure and O2 on the induction of direct strand breaks in 5-bromodeoxyuridine-containing oligonucleotides. RESULTS: The efficiency of direct strand break formation in duplex DNA is dependent upon O2 and results in fragments containing 3'-phosphate and the labile 3'-ketodeoxyadenosine termini. The ratio of the 3'-termini is also dependent upon O2 and structure. Deuterium product isotope effects and tritium-transfer studies indicate that hydrogen-atom abstraction from the C1'- and C2'-positions occurs in an O2- and structure-dependent manner. CONCLUSIONS: The reaction mechanisms by which DNA containing 5-bromodeoxyuridine is sensitized to damage by UV irradiation are dependent upon whether the substrate is hybridized and upon the presence or absence of O2. Oxygen reduces the efficiency of direct strand break formation in duplex DNA, but does not affect the overall strand damage. It is proposed that the sigma radical abstracts hydrogen atoms from the C1'- and C2'-positions of the 5'-adjacent deoxyribose moiety, whereas the nucleobase peroxyl radical selectively abstracts the C1'-hydrogen atom from this site. This is the second example of DNA damage amplification by a nucleobase peroxyl radical, and might be indicative of a general reaction pattern for this family of reactive intermediates.


Subject(s)
Bromodeoxyuridine/radiation effects , DNA/radiation effects , Nucleic Acid Conformation/radiation effects , Oligonucleotides/radiation effects , Oxygen , Bromodeoxyuridine/chemistry , DNA/chemistry , DNA/drug effects , Deuterium/metabolism , Kinetics , Models, Chemical , Oligonucleotides/chemistry , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Ultraviolet Rays
6.
Mutat Res ; 403(1-2): 95-101, 1998 Jul 17.
Article in English | MEDLINE | ID: mdl-9726010

ABSTRACT

A phenomenon of spontaneous DNA instability displays itself as the low level of repair DNA synthesis that takes place during any cell cycle phases. However, there is a problem in detection of very low intensive repair DNA synthesis. This paper suggests two approaches to detect the spontaneous DNA instability. The first method involves a blockade of the DNA gaps sealing by a combination of inhibitors, hydroxyurea and arabinofuranosyl cytosine. An accumulation of single strand gaps leads to production of DNA double strand breaks and results to reproductive inactivation of cells. It was shown that registration of both these events by different methods (such as viscoelastometry of DNA, orthogonal pulse electrophoresis or comet assay for double strand breaks as well as effectiveness of colony growth for cell inactivation) may be used as suitable measure of the spontaneous DNA instability. The second approach bases on photolysis of bromodeoxyuridine incorporated into repair DNA patches during the spontaneous repair DNA synthesis. Long wave UV irradiation of cells containing bromodeoxyuridine labeled DNA stained with Hoechst 33342 causes their inactivation. Experimental results presented confirm that both methods actually detect the spontaneous DNA instability. It takes note of the spontaneous DNA instability varies for cells from different tissues and species and increases during aging.


Subject(s)
DNA Repair , DNA/genetics , DNA/metabolism , Benzimidazoles , Bromodeoxyuridine/metabolism , Bromodeoxyuridine/radiation effects , Cell Cycle , Cells, Cultured , Chromosome Breakage , Cytarabine/pharmacology , DNA/biosynthesis , DNA Repair/drug effects , DNA Repair/radiation effects , Drug Stability , Fluorescent Dyes , HeLa Cells , Humans , Hydroxyurea/pharmacology , Lymphocytes/drug effects , Lymphocytes/metabolism , Lymphocytes/radiation effects , Photolysis , Ultraviolet Rays
7.
Acta Oncol ; 35(7): 877-82, 1996.
Article in English | MEDLINE | ID: mdl-9004766

ABSTRACT

In order to investigate DNA damage due to Auger cascades in bromodeoxyuridine (BrdU), BrdU mixed with other nucleosides, as a model of DNA, was irradiated in solids by gamma-rays and monoenergetic x-rays at around the K-absorption edge of bromine (13.47 keV). The main products of BrdU were deoxyuridine produced through debromination, and bromouracil produced through the decomposition of a sugar group. The rates of the debromination and the nucleobases release of additives were markedly increased in the mixed sample. This observation indicated that the additives surrounding BrdU efficiently supplied protons and then decomposed. The major products by x-rays were the same as those by gamma-rays, indicating that Auger cascades in bromine atoms did not produce specific products. The production rates for all products from the mixed sample were about 2.5 times higher at 13.51 (above the K-absorption edge) keV than at 13.43-keV x-rays.


Subject(s)
Bromodeoxyuridine/radiation effects , Linear Energy Transfer , Bromodeoxyuridine/metabolism , Bromouracil/metabolism , Chromatography, High Pressure Liquid , Cobalt Radioisotopes/pharmacology , Deoxyuridine/metabolism , Magnetic Resonance Spectroscopy , X-Rays
8.
Mutagenesis ; 10(5): 453-6, 1995 Sep.
Article in English | MEDLINE | ID: mdl-8544761

ABSTRACT

In a recent publication we described a novel route for the introduction of DNA double-strand breaks (DSBs) into cellular DNA. This involved the labelling of cellular DNA with bromodeoxyuridine (BrdU) and exposure to UVA light in the presence of Hoechst dye No. 33258. Here, we report an extension of that work to the use of iododeoxyuridine (IdU); cells substituted with known levels of IdU were subjected to a similar photolysis treatment and analyzed for strand breaks by elution assays. Results indicate that both single-strand breaks (SSBs) and DSBs depend linearly on the level of IdU substitution and fluence of UVA light. The yields of SSBs and DSBs were found to be 3.5 x 10(-5) and 9.5 x 10(-7)/IdU moiety/kJm-2, respectively. These results indicate that approximately 15-fold less SSBs and 5-fold less DSBs are produced per IdU than per BrdU moiety.


Subject(s)
DNA Damage , DNA/drug effects , Idoxuridine/pharmacology , Photolysis , Photosensitizing Agents/pharmacology , Animals , Bisbenzimidazole/pharmacology , Bromodeoxyuridine/pharmacology , Bromodeoxyuridine/radiation effects , Cricetinae , Cricetulus , DNA/radiation effects , DNA, Single-Stranded/drug effects , DNA, Single-Stranded/radiation effects , Fibroblasts/drug effects , Fibroblasts/radiation effects , Ultraviolet Rays
9.
Somat Cell Mol Genet ; 17(6): 567-72, 1991 Nov.
Article in English | MEDLINE | ID: mdl-1767335

ABSTRACT

Somatic cell hybrids derived from the fusion of Chinese hamster ovary cells (CHO) and mutant Syrian hamster melanoma cells (2E) were tested for their ability to grow with all of the thymidine (dThd) in their DNA replaced with 5-bromo-2'-deoxyuridine (BrdU), a phenotypic capability of the 2E cells but not of the CHO cells. Under these conditions, the 2E cells survived and grew, all of the hybrid clones survived and grew to varying degrees, and the CHO cells did not survive at all. When 2E cells were tested, they were also found to be resistant to the toxic effects of BrdU substitution and white light irradiation, relative to CHO cells. Thus, when the DNAs of 2E and CHO cells were equally (50%) substituted with BrdU, and the two cell lines irradiated with identical doses of white light, the survival of CHO cells was reduced to less than 1% of that of unirradiated cells, while 40% of the 2E cells survived. The 2E x CHO hybrid clones were found to survive at values from 10% to 40% under these identical conditions. Thus, the phenotypic characteristics of 2E cells involving total substitution and resistance to the toxic effects of BrdU substitution and white light irradiation appear to be expressed in a codominant fashion in somatic cell hybrids.


Subject(s)
Bromodeoxyuridine/pharmacology , Drug Resistance/physiology , Animals , Bromodeoxyuridine/metabolism , Bromodeoxyuridine/radiation effects , Cell Line , Cell Survival/physiology , Clone Cells , Cricetinae , Cricetulus , Hybrid Cells/metabolism , Mesocricetus , Selection, Genetic
10.
Int J Radiat Biol ; 60(5): 757-68, 1991 Nov.
Article in English | MEDLINE | ID: mdl-1680947

ABSTRACT

The biological effects of inner-shell ionization in bromine atoms incorporated into DNA in the form of bromodeoxyuridine monophosphate (BrdUMP), induced by monochromatized synchrotron X-rays, were studied using a deoxythymidine monophosphate (dTMP)-permeable mutant of yeast, Saccharomyces cerevisiae. The BrdUMP-incorporated yeast cells were irradiated with monochromatic X-rays of 13.51 or 13.45 keV, between which the bromine K-absorption edge (13.47 keV) is located. The cells were 1.07 times more sensitive to irradiation by 13.51 keV X-rays than at 13.45 keV, while dTMP-incorporated cells did not show any difference in sensitivity. In the presence of a radioprotector during irradiation, BrdUMP-incorporated cells showed a larger enhancement (1.20). These enhancements observed in the bromine-incorporated cells cannot be explained only by an increase of the absorbed dose due to a substitution of CH3 group of thymine by bromine. It may be concluded that a major part of the enhancement was caused by inner-shell photoionization, followed by an Auger cascade of the bromine in the DNA. The quantum yield of lethality caused by the photoabsorption of bromine K-shell is not affected by the presence of cysteamine, suggesting the biological enhancement by the Auger processes may not be influenced by chemical protection.


Subject(s)
Bromodeoxyuridine/radiation effects , DNA, Fungal/radiation effects , Electrons , Saccharomyces cerevisiae/radiation effects , Cell Survival/drug effects , Cell Survival/radiation effects , DNA, Fungal/drug effects , Mutation , Particle Accelerators , Saccharomyces cerevisiae/cytology , Saccharomyces cerevisiae/drug effects , Thymidine Monophosphate/pharmacology
11.
Photochem Photobiol ; 53(5): 595-609, 1991 May.
Article in English | MEDLINE | ID: mdl-1881960

ABSTRACT

Several studies in the literature indicate that histones (lysine rich proteins found associated with DNA in eukaryotic chromatin), as well as poly-L-lysine, can be photocross-linked by ultraviolet (UV) light to DNA in which 5-bromo-2'-deoxyuridine has been substituted for thymidine. To gain some insight into the possible nature of this cross-linking, we have studied the photoreactions occurring in deoxygenated aqueous solutions containing 5-bromouracil (I) (BrUra) or 5-bromo-2'-deoxyuridine (III) (BrdUrd) and ethylamine, a lysine side chain analog. In the case of I this reaction produced the ring opened compound N-(N'-ethylcarbamoyl)-3-amino-2-bromoacrylamide (Ia). A small amount of N-(N'-ethylcarbamoyl)-3-ethylamino-2-bromoacrylamide (Ic) was also isolated. It was found that purified Ia, standing in the presence of ethylamine, was gradually converted to Ic in a dark reaction. The beta and alpha anomers of N-(N'-ethylcarbamoyl)-3-(2'deoxyribofuranos-1'-yl) amino-2-bromoacrylamide (IIIa and IIIb respectively) were isolated as products in the photoreaction of III with ethylamine; the alpha anomer was produced in a dark reaction from the beta anomer. The identity of these anomers was established by comparison of their proton NMR spectra with those of the four corresponding alpha and beta furanosyl and pyranosyl isomeric nucleosides of thymine, which are presented in the Appendix. A study was also made of the reaction of I with methylamine; a ring opened product analogous to Ia, viz. N-(N'-methylcarbamoyl)-3-amino-2-bromoacrylamide (IIa) was formed. A similar study with 5-bromo-1-methyluracil produced N-(N'-methylcarbamoyl)-3-methylamino-2-bromoacrylamide (IIc) as a product. Likewise, the reaction of 5-chlorouracil with ethylamine was studied and N-(N'-ethylcarbamoyl)-3-amino-2-chloroacrylamide (Ie), which is analogous in structure to Ia, was found to be produced. Structural identifications were made through use of UV spectroscopy, high resolution 1H-NMR spectroscopy, mass spectrometry and, in the case of Ia and IIa, 13C-NMR spectroscopy. In the BrUra and BrdUrd reaction systems, described above, dehalogenation reactions accounted for a major portion of the products. The yields of ring opened products, determined at pH 10, ranged from a high of 10.3% in the BrUra-ethylamine system to a low of 1.7% in the MeBrUra-methylamine system.(ABSTRACT TRUNCATED AT 400 WORDS)


Subject(s)
Amines/chemistry , Bromodeoxyuridine/chemistry , Bromouracil/chemistry , Amines/radiation effects , Bromodeoxyuridine/radiation effects , Bromouracil/radiation effects , Photochemistry , Structure-Activity Relationship
13.
Eksp Onkol ; 11(5): 14-6, 1989.
Article in Russian | MEDLINE | ID: mdl-2791951

ABSTRACT

5-bromodeoxyuridine (BUdR) injected to rats in the neonatal period is shown to produce a pronounced carcinogenic effect which brings about the appearance of various benign and malignant tumours. Exposure of females to X-ray total-body irradiation (1.5 Gy) was followed by intensification of the carcinogenic effect of BUdR. Assuming that this pyrimidine analog reacts solely with DNA substituting thymidine during DNA synthesis and induces point mutations due to tautomerization, the data obtained demonstrate the possibility of tumour induction by a selective DNA perturbation.


Subject(s)
Bromodeoxyuridine/toxicity , Cocarcinogenesis , Animals , Bromodeoxyuridine/radiation effects , DNA Damage , Female , Male , Neoplasms, Radiation-Induced , Rats , X-Rays
16.
J Virol ; 47(1): 151-70, 1983 Jul.
Article in English | MEDLINE | ID: mdl-6345803

ABSTRACT

We have carried out a series of experiments designed to characterize the impact of UV irradiation (260 nm) on 5-bromodeoxyuridine-labeled (heavy) T4 bacteriophage, both before and after infection of Escherichia coli. In many respects, these effects differ greatly from those previously described for non-density-labeled (light) phage. Moreover, our results have led us to propose a model for a novel mechanism of host-mediated repair synthesis, in which excision of UV-damaged areas is followed by initiation of replication, strand displacement, and a considerable amount of DNA replication. UV irradiation of 5-bromodeoxyuridine-labeled phage results in single-stranded breaks in a linear, dose-dependent manner (1.3 to 1.5 breaks per genomic strand per lethal hit). This damage does not interfere with injection of the phage genome, but some of the UV-irradiated heavy phage DNA undergoes additional intracellular breakdown (also dose dependent). However, a minority (25%) of the injected parental DNA is protected, maintaining its preinjection size. This protected moiety is associated with a replicative complex of DNA and proteins, and is more efficiently replicated than is the parental DNA not so associated. Most of the progeny DNA is also found with the replicative complex. The 5-bromodeoxyuridine of heavy phage DNA is debrominated by UV irradiation, resulting in uracil which is removed by host uracil glycosylase. Unlike the simple gap-filling repair synthesis after infection with UV-irradiated light phage, the repair replication of UV-irradiated heavy phage is extensive as determined by density shift of the parental label in CsC1 gradients. The newly synthesized segments are covalently attached to the parental fragments. The repair replication takes place even in the presence of chloramphenicol, a protein synthesis inhibitor, suggesting it is host mediated. Furthermore, the extent of the repair replication is greater at higher doses of UV irradiation applied to the heavy phage. This abundant synthesis results ultimately in dispersion of the parental sequences as short stretches in the midst of long segments of newly synthesized progeny DNA. Together, the extensive replication and the resulting distribution pattern of parental sequences, without significant solubilization of parental label, are most consistent with a model of repair synthesis in which the leading strand displaces, rather than ligates to, the encountered 5' end.


Subject(s)
Bromodeoxyuridine/radiation effects , Chlorides , DNA, Viral/radiation effects , T-Phages/radiation effects , Ultraviolet Rays , Centrifugation, Density Gradient , Cesium , Chloramphenicol/pharmacology , DNA Repair , DNA Replication/drug effects , DNA, Viral/isolation & purification , Escherichia coli/radiation effects , Models, Biological , Sucrose , Thymidine/metabolism
18.
Nucleic Acids Res ; 5(9): 3303-13, 1978 Sep.
Article in English | MEDLINE | ID: mdl-309109

ABSTRACT

Combinations of 5-bromodeoxyuridine (BrdUrd) and 3H-deoxyadenosine (3H-DAdo) short pulses were given in the synchronous DNA-replication period of Physarum polycephalum. After a chase period, UV-photolysis products were analyzed on alkaline sucrose gradients. This strategy has allowed the following conclusions. a) at the time of master-initiation of DNA replication, points separated by 1.1-2.2x10(7) daltons of single strand DNA may initiate DNA synthesis. b) among these, only selected groups of replicons actually proceed in DNA replication at this time, while others appear to hold (later temporal sets of replicons). The origins of the ones that proceed in replication are separated from each other by a distance corresponding to 1.1-2.x10(7) daltons. c) regions in actual replication are separated from each other by increasing distances (up to 1.5x10(8) daltons single strand DNA) at later times in S.


Subject(s)
DNA Replication , Physarum/genetics , Bromodeoxyuridine/radiation effects , DNA/radiation effects , Deoxyadenosines/metabolism , Kinetics , Molecular Weight , Photolysis , Ultraviolet Rays
19.
Nature ; 274(5668): 229-32, 1978 Jul 20.
Article in English | MEDLINE | ID: mdl-683303

ABSTRACT

Treatment of Syrian hamster embryo cells with 5-bromodeoxyuridine followed by near ultraviolet irradiation results in neoplastic transformation of these cells. This demonstrates that a direct perturbation of DNA is sufficient to initiate neoplastic transformation.


Subject(s)
Bromodeoxyuridine , Cell Transformation, Neoplastic/chemically induced , DNA/radiation effects , Bromodeoxyuridine/radiation effects , Cell Line , Cell Survival/drug effects , Mutation/drug effects , Mutation/radiation effects , Ultraviolet Rays
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