Differential responses of nascent DNA synthesis and chain elongation in V79 and V79/79 cells exposed to u.v. light and chemical mutagens

DNA repair after u.v., N-methyl-N-nitrosourea (MNU) and ethylmethane sulphonate (EMS) in Chinese hamster V79 cells and the mutagen sensitive derivative V79/79 was investigated by measurement of five parameters: production of strand breaks in template DNA, incorporation of [3H]TdR, semi-conservative...

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Bibliographic Details
Published in:Carcinogenesis (New York) 1983, Vol.4 (3), p.261-268
Main Authors: Fox, Margaret, Bloomfield, Moira E., Hopkins, Josephine, Boyle, J.M.
Format: Article
Language:English
Subjects:
Animals
Cell Line
Cricetinae
Cricetulus
DNA - isolation & purification
DNA Replication - drug effects
DNA Replication - radiation effects
Ethyl Methanesulfonate - toxicity
Genetic Variation
Kinetics
Lung
Methylnitrosourea - toxicity
Molecular Weight
Mutagens
Mutation
Nitrosourea Compounds - toxicity
Ultraviolet Rays
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Summary:DNA repair after u.v., N-methyl-N-nitrosourea (MNU) and ethylmethane sulphonate (EMS) in Chinese hamster V79 cells and the mutagen sensitive derivative V79/79 was investigated by measurement of five parameters: production of strand breaks in template DNA, incorporation of [3H]TdR, semi-conservative and repair synthesis, molecular weights of pulse labelled DNA after mutagen exposure (nascent synthesis) and molecular weights of DNA pulse labelled and chased after mutagen exposure (elongation and ligation). Equal template strand breakage was evident in both cell lines immediately after MNU and EMS exposure and by 4–5 h after MNU the extent of fragmentation was greater in V79/79 cells. After u.v. irradiation template fragmentation was evident in V79/79 but not in V79 cells, even though V79/79 cells failed to excise cyclobutane dimers and repair synthesis was demonstable in V79 cells but not in V79/79 cells after exposure to all three mutagens. The rate of incorporation of [3H]TdR during semi-conservative DNA synthesis was inhibited equally in a dose dependent manner after u.v. and MNU exposure; incorporation by V79/79 cells was inhibited to a greater extent than by V79 cells after EMS exposure. Nascent DNA synthesis was suppressed more in V79/79 cells than in V79 cells after u.v. but to similar extents in both cell lines after MNU and EMS treatment. Pulse chase experiments indicated a lower rate of elongation of nascent DNA in V79/79 cells after MNU and u.v. exposure but little difference was detectable after EMS.
ISSN:0143-3334
1460-2180
DOI:10.1093/carcin/4.3.261