Structure and in vitro replication of DNA templates containing 7,8-dihydro-8-oxoadenine

Abstract

Adenine residues in DNA are oxidized under the action of ionizing radiation at the C-B position to give 7,8-dihydro-8-oxoadenine. The formation of this lesion can be considered a cause of mutations and carcinogenesis. Oligodeoxyrlbonucleotides 39 and 47 bases long containing a single 7,8-dihydro-8- oxoadenine (8-hydroxyadenine) residue were synthesized by using nucieoside phosphoramidites. They were used as templates to study the copies obtained in vitro by the Kienow fragment and the thermostable Taq DNA poiymerase. 7,8-Dihydro-8- oxoadenine does not block the replication and thymine is incorporated opposite the damage. The modifications of the DNA duplex conformation provoked by 7,8-dihydro-8-oxoadenine are minor. 1H NMR spectroscopy shows that the duplex is in a B form, the sugar in a normal position in the helix and the modified base in the anti position. NMR confirms that 7,8-dihydro-8-oxoadenine exists predominantly in the keto form. © 1991 Oxford University Press.