Non-random alkylation of DNA sequences induced in vivo by chemical mutagens.
Previous studies of the interaction of alkylating agents on the eukaryotic genome support the idea that induction of DNA adducts is at specific genomic sites. Here we show molecular and cytological evidence that alkylation is rather specific. Mammalian cell cultures were exposed to different doses of mutagens and the DNA was analyzed by density gradient ultracentrifugation, hydroxylapatite fractionation, and by restriction enzyme analysis. Studies with the labelled mutagens N-ethyl-N-nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine show that there is a non-random distribution of the adducts. The adducts are found more frequently in A-T, G-C rich satellite DNA and highly repetitive sequences. Analysis with restriction enzymes shows that both methyl and ethyl groups influence the restriction patterns of the enzymes HpaII and MspI that recognize specific endogenous DNA methylation. These data suggest, as a subsequent mechanism, a modification in the pattern of the normal endogenous methylation of 5-methylcytosine.
Durante
M
M
Dipartimento di Biologia delle Piante Agrarie, Università di Pisa, Italy.
Geri
C
C
Bonatti
S
S
Parenti
R
R
D000478:Alkylation; D001482:Base Composition; D001483:Base Sequence; D002250:Carbon Radioisotopes; D002470:Cell Survival / Q000187:drug effects; D004273:DNA, Neoplasm / Q000302:isolation & purification / Q000378:metabolism*; D005038:Ethylnitrosourea / Q000378:metabolism* / Q000494:pharmacology; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008769:Methylnitronitrosoguanidine / Q000378:metabolism* / Q000494:pharmacology; D009153:Mutagens / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D015183:Restriction Mapping; D014316:Tritium
D002250:Carbon Radioisotopes; D004273:DNA, Neoplasm; D009153:Mutagens; D014316:Tritium; D008769:Methylnitronitrosoguanidine; D005038:Ethylnitrosourea