Alkali-sensitive sites in DNA from human cells treated with ultraviolet light, 1'-acetoxysafrole or 1'-acetoxyestragole
The formation and repair of alkali-labile sites in the DNA of human cells treated with 254 nm u.v. light, 1'-acetoxyestragole (1'-AcO-E) or 1'-acetoxysafrole (1'-AcO-S) have been studied. DNA was analysed by sedimentation in alkaline sucrose gradients after the cells had been layered on the gradients in lysis solution for 15 h (long lysis) or for only 0.75 h (short lysis). With the long lysis technique, a dose of 20 J/m2 resulted in 0.2-0.4 strand breaks/10(8) daltons while treatment of cells with 0.5 mM 1'-AcO-E or 1'-AcO-S caused 0.1-0.3 strand breaks/10(8) daltons. In excision repair proficient T98G cells, one third to two thirds of these strand breaks disappeared upon 4 h incubation after exposure to each of the three agents. In excision repair deficient xeroderma pigmentosum fibroblasts (XPA), the alkali-labile sites produced by 1'-AcO-E or 1'-AcO-S were still repaired, although those resulting from u.v.-irradiation were not. Similar characteristics were observed after the short lysis period. The sedimentation velocities of nucleoids, prepared from treated XPA cells, in neutral sucrose gradients containing ethidium bromide, did not reveal the presence of overt strand breaks in the DNA, suggesting that the lesions were of a type in which the sugar-phosphate backbone was intact but sensitive to hydrolysis by alkali. The contribution of this type of damage to the total DNA damage produced by the agents was estimated to be less than 1% for u.v., and less than 2.5% for 1'-AcO-E and 1'-AcO-S.
- Research Organization:
- Department of Biological Sciences, Stanford University, Stanford, CA
- OSTI ID:
- 6491034
- Journal Information:
- Carcinogenesis (N.Y.); (United States), Journal Name: Carcinogenesis (N.Y.); (United States) Vol. 3:8; ISSN CRNGD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560121 -- Radiation Effects on Cells-- External Source-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMAL CELLS
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BIOSYNTHESIS
CELL CULTURES
CONNECTIVE TISSUE CELLS
DNA
ELECTROMAGNETIC RADIATION
FIBROBLASTS
MAMMALS
MAN
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PRIMATES
RADIATION EFFECTS
RADIATIONS
RADIOINDUCTION
RECOVERY
REPAIR
SOMATIC CELLS
STRAND BREAKS
SYNTHESIS
ULTRAVIOLET RADIATION
VERTEBRATES