SCE formation after exposure of CHO cells prelabelled with BrdU or biotin-dUTP to various DNA-damaging agents.
Formation of sister chromatid exchanges (SCE) is a mechanism of repair or bypass of DNA damage during S phase. Although SCE have been studied for a long time, the types of DNA lesions involved and the role of 5-bromodeoxyuridine (BrdU) in SCE formation are a matter of debate. We have developed a novel method of differential labelling of sister chromatids with biotin-16-2'-deoxyuridine-5'-triphosphate (biotin-dUTP) and could show that a substantial proportion of radiation-induced SCE arise via damage to BrdU-moieties. The present investigations were performed to examine the role of BrdU in the formation of SCE by the endonucleases AluI and DNase I, as well as the alkylating agent mitomycin C (MMC). CHO cells unifilarily prelabelled with biotin-dUTP or BrdU were treated and the frequencies of SCE analysed in the first post-treatment mitoses. AluI induced similar frequencies of SCE in cells prelabelled with BrdU or biotin-dUTP. DNase I induced significantly more SCE in cells prelabelled with BrdU than with biotin-dUTP. MMC induced slightly more SCE in cells labelled with biotin-dUTP than BrdU, but the difference was not significant. The possible mechanisms responsible for the enhanced SCE frequency following DNase I treatment of cells prelabelled with BrdU are discussed.
Institute of Genetics, Department of Molecular Genetics, 1113 Sofia, Bulgaria.
Lubomir
L
Stoilov
Andrzej
A
Wojcik
Ashok K
AK
Giri
Günter
G
Obe
D000477:Alkylating Agents / Q000633:toxicity; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives* / Q000378:metabolism*; D001973:Bromodeoxyuridine / Q000378:metabolism*; D016466:CHO Cells / Q000187:drug effects; D006224:Cricetinae; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D003850:Deoxyribonuclease I / Q000633:toxicity; D015252:Deoxyribonucleases, Type II Site-Specific / Q000633:toxicity; D003856:Deoxyuracil Nucleotides / Q000378:metabolism*; D016685:Mitomycin / Q000633:toxicity; D012854:Sister Chromatid Exchange / Q000187:drug effects*; D014544:Uridine Triphosphate / Q000031:analogs & derivatives
D000477:Alkylating Agents; D001710:Biotin; D001973:Bromodeoxyuridine; D004247:DNA; D003850:Deoxyribonuclease I; D015252:Deoxyribonucleases, Type II Site-Specific; D003856:Deoxyuracil Nucleotides; D016685:Mitomycin; C087624:biotin-16-dUTP; D014544:Uridine Triphosphate; C024669:endodeoxyribonuclease AluI