Incorporation of noncomplementary nucleotides at high frequencies by ribodeoxyvirus DNA polymerases and Escherichia coli DNA polymerase I

Abstract

The fidelity of DNA synthesis with synthetic homopolymer templates by two ribodeoxyvirus DNA polymerases and E. coli DNA polymerase I was examined by nearest neighbor frequency analyses. The experiments were designed to favor the incorporation of noncomplementary nucleotides, and the reactions were carried out only for short periods of time. All incorporations were template dependent. The frequency of incorporation of noncomplementary nucleotides next to complementary nucleotides by all three of these DNA polymerases significantly varied, depending on the conditions, from almost none (less than 0.2%) to 100% of the incorporation of the complementary nucleotide. In general, there was more incorporation of noncomplementary nucleotides in the presence of Mn2+ than in the presence of Mg2+ and with ribohomopolymer templates than with deoxyribohomopolymer templates. With a heteropolymer RNA template, the infidelity of DNA synthesis by one of the ribodeoxyvirus DNA polymerases was also increased by the presence of Mn2+ in the DNA synthesizing reaction. These findings indicate that, under appropriate conditions, any DNA polymerase has the potential to make a significatn number of errors in DNA synthesis and that altered conditions for DNA polymerase action might play a role in spontaneous mutation.