Effect of sequence contexts on misincorporation of nucleotides opposite 2-hydroxyadenine.

Twelve oligonucleotides containing 2-hydroxyadenine (2-OH-Ade) with different neighboring bases were used as templates in DNA polymerase reactions,and the effects of the sequence contexts were investigated. DNA polymerases alpha and beta inserted dTMP and dCMP opposite 2-OH-Ade in most of the oligonucleotides tested. The Klenow fragment of DNA polymerase I primarily incorporated dTMP and dGMP. Effects of the 5'-flanking base of 2-OH-Ade was found when the 3'-flanking base of 2-OH-Ade was A or C. Incorporation of dAMP occurred when the oxidized base was located in a 5' -TA*A- 3' (A* represents 2-OH-Ade) sequence. These results suggest that the formation of 2-OH-Ade in DNA may induce all the mutations involving A (A-->G transition, and A-->T and A-->C transversions) in cells.