Mutation rates and intrinsic fidelity of retroviral reverse transcriptases

Abstract

Retroviruses are RNA viruses that replicate through a DNA intermediate, in a process catalyzed by the viral reverse transcriptase (RT). Although cellular polymerases and host factors contribute to retroviral mutagenesis, the RT errors play a major role in retroviral mutation. RT mutations that affect the accuracy of the viral polymerase have been identified by in vitro analysis of the fidelity of DNA synthesis, by using enzymological (gel-based) and genetic assays (e.g., M13mp2 lacZ forward mutation assays). For several amino acid substitutions, these observations have been confirmed in cell culture using viral vectors. This review provides an update on studies leading to the identification of the major components of the fidelity center in retroviral RTs.

Keywords: DNA polymerase; HIV; fidelity; mutation; retroviruses; reverse transcriptase.

Figure 1.

Major steps of the retroviral replication cycle and host factors that could influence the viral mutation rate.

Figure 2.

Proposed models and mutational intermediates leading to the generation of base substitutions and frameshift errors [adapted from Ref. 86].

Figure 3.

View of the nucleic acid binding cleft of HIV-1 RT showing the location of amino acids that influence fidelity of DNA synthesis (blue and orange CPK models). Ribbon diagrams are used for the representation of p66 (blue) and p51 (green). A stick representation is used for the template (red) and primer (magenta) strands of the DNA/DNA complex. The incoming dNTP is represented with a yellow CPK. Atomic coordinates were taken from Protein Data Bank file 1RTD [114].