Enzymatic methylation of cytosine in DNA is prevented by adjacent O6-methylguanine residues.
J Biol Chem
; 266(13): 7985-7, 1991 May 05.
Article
em En
| MEDLINE
| ID: mdl-2022628
ABSTRACT
The effect of O6-alkylation of guanine residues on the enzymic methylation of cytosine has been studied using synthetic oligonucleotides in which all guanines in cytosine-guanine sequences at potentially methylatable sites are replaced by O6-methylguanine. In contrast with the unmodified forms, which showed high acceptance activity for methyl-3H-labeled groups from S-adenosyl-L-[methyl-3H]methionine in the presence of DNA methylase, the modified oligonucleotides were not substrates for the enzyme either in the single-stranded or annealed forms. In view of the importance of cytosine methylation in the down-regulation of certain genes, the potential to affect gene expression by this mechanism may be a contributory factor in the toxic and carcinogenic effects of chemical methylating agents.
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Base de dados:
MEDLINE
Assunto principal:
DNA Bacteriano
/
Citosina
/
Guanina
Idioma:
En
Ano de publicação:
1991
Tipo de documento:
Article