Mutational studies of human immunodeficiency virus type 1 reverse transcriptase: The involvement of residues 183 and 184 in the fidelity of DNA synthesis

The high error rates characteristic of human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) are a presumptive source of the viral hypermutability that impedes prevention and therapy of acquired immunodeficiency syndrome (AIDS), We have analyzed two mutants of HIV-1 RT by conducting a comparative study of the accuracy of DNA synthesis, Each mutant bears a single amino acid substitution adjacent to the two aspartic acid residues at positions 185 and 186 in the highly conserved DNA polymerase active site, The first mutant, Met 184 --> Leu (M184L), displays a marked reduction in both misinsertion and mispair extension, suggesting a fidelity of DNA synthesis significantly higher than that of the wild-type HIV-1 RT, The second mutant, Tyr 183 --> Phe (Y183F), shows a decrease in mispair extension with no significant change in misincorporation. Thus, the overall pattern of error-proneness of DNA synthesis is: wild-type HIV-1 RT > Y183F > M184L, Taken together, it is possible that residues 183 and 184 contribute to the low fidelity of DNA synthesis characteristic of the reverse transcriptases of HIV-1, HIV-2 and possibly, of other lentiviruses, Our observations may bear on the nature of potential mutations responsible for resistance to the nucleoside analogs used in chemotherapy of AIDS.