O6-methylguanine inibits the binding of transcription factors to DNA

Abstract

To study the effect of methylation of 06-guanine on the binding of cellular factors to different DNA sequences, modified oligonucleotides were constructed, in which O6-Methylguanine (06-MeG) replaced some guanines. The DNA sequences utilized were: the region of the cfos promoter containing the binding site for serum response factor (SRF); the region of the HIV LTR containing two binding sites for the transcription factor NFχB; the region of the HIV LTR containing three binding sites for the cellular factor sp1. After incubation of labeled oligonucleotides, either unmodified or containing 06-MeG, with nuclear extracts obtained from different cell lines, gel retardation assays indicated that the presence of 06-MeG resulted in inhibition of binding of cellular factors to DNA sequences located in the promoter regions of genes. This inhibition was not the same for all modified oligonucleotides but dependent on the position in which 06-MeG was located. The results obtained indicate the alkylation of 06-guanine affects the binding of transcription factors and thereby possibly the regulation of genes expression. © 1991 Oxford University Press.