Increased misincorporation fidelity observed for nucleoside analog resistance mutations M184V and E89G in human immunodeficiency virus type 1 reverse transcriptase does not correlate with the overall error rate measured in vitro

Nucleoside analog-resistant variants of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) that displayed higher in vitro polymerase fidelity were previously identified via nucleotide insertion and mispair extension assays. To evaluate the contribution of increased nucleotide insertion and primer extension fidelities on the overall error rate of HIV-1 RT, we have measured the impact of two such mutations, E89G and M184V, on DNA copying fidelity in an M13 phage-based forward mutation assay. Using this assay, we observed mutation frequencies of 8.60 x 10^-3, 6.26 x 10^-3, 5.53 x 10^-3, and 12.30 x 10^-3 for wild-type, E89G, M184V, and double-mutant E89G/M184V HIV-1 RTs, respectively. Therefore, the overall polymerase fidelities of wild-type, E89G, M184V, and E89G/M184V HIV-1 RTs are similar (less than twofold differences) for DNA-dependent DNA synthesis. Thus, rather large increases in fidelity of deoxynucleoside triphosphate insertion and mispair extension observed previously appear not to influence the overall error rate of these mutants. However, a qualitative analysis of the mutations induced revealed significant differences in the mutational spectra between the wild-type and mutant enzymes.