Misincorporation of dNTPs opposite 1,N2-ethenoguanine and 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine in oligonucleotides by Escherichia coli polymerases I exo- and II exo-, T7 polymerase exo-, human immunodeficiency virus-1 reverse transcriptase, and rat polymerase beta.

1,N2-Ethenoguanine (1,N2-e-Gua) and 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine (HO-ethanoGua) are two modified bases formed in the reaction of DNA with 2-chlorooxirane, the epoxide derivative of vinyl chloride. The oligonucleotides (19-mers), 5‘-CAGTGGGTG*TCCGAATTGA-3‘, were prepared, with each of these modified bases substituted for G at G*. HO-ethanodeoxyguanosine exists predominantly as a mixture of diastereomers of the closed cyclic hemiaminal form, 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine, shown by H218O experiments to be in equilibrium with the open form, N2-(2-oxoethyl)Gua. Both adducts retarded the 3‘-extension of a complementary 10-mer primer by all of the polymerases examined, but in every case, some full-length product was obtained. Nucleotide sequence analysis indicated misincorporation of dGTP and dATP across from both 1,N2-e-Gua and HO-ethanoGua, with the extent varying considerably among the polymerases. Similar results were obtained when the abilities of the polym...