Repair of synthetic oligonucleotides containing O6-methylguanine, O6-ethylguanine and O4-methylthymine, by O6-alkylguanine-DNA alkyltransferase.

32P-Labelled self-complementary oligonucleotides containing O6-methylguanine, O6-ethylguanine, and O4-methylthymine have been synthesized and used as substrates for the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AAT). The reaction was second-order with rate constants of 2.6 X 10(7) M-1 sec-1 for O6-methylguanine, 2.6 X 10(4) M-1 sec-1 for O6-ethylguanine and 2.5 X 10(3) M-1 sec-1 for O4-methylthymine. These oligomers should allow sensitive and specific assay of the mammalian enzyme.