Effect of N-methyl-N'-nitro-N-nitrosoguanidine on DNA polymerases alpha and beta in vitro

DNA polymerases alpha and beta were treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The activities of the modified DNA polymerase were decreased and the degree of lowered activity varied with the template employed. However, no decrease in fidelity was observed in DNA synthesis by the MNNG-treated polymerases. It is suggested that direct modification of the DNA polymerase molecule by MNNG is not the cause of carcinogenesis.