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Purifying selection masks the mutational flexibility of HIV-1 reverse transcriptase.
Robert A Smith1, Donovan J Anderson, Bradley D Preston
1Department of Pathology, University of Washington, Seattle, Washington 98195, USA.
The Journal of Biological Chemistry
|March 12, 2004
Summary
Human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) tolerates mutations in conserved regions, revealing flexibility. This adaptability in HIV-1 RT function aids viral evolution and drug resistance.
Area of Science:
- Molecular Biology
- Virology
- Evolutionary Biology
Background:
- DNA and RNA polymerases possess conserved motifs (A, B, C).
- Conserved amino acid sequences in these motifs are crucial for polymerase function across species.
- HIV-1 reverse transcriptase (RT) motif B is highly conserved in vivo.
Purpose of the Study:
- To investigate the functional tolerance of HIV-1 RT motif B to amino acid substitutions.
- To assess the impact of these substitutions on viral infectivity and fitness.
- To explore potential alterations in drug susceptibility.
Main Methods:
- Construction of mutant HIV-1 libraries with random single amino acid replacements in RT motif B.
- Selection in cell culture to evaluate RT function and viral replication.
- Serial passage experiments to assess viral fitness and drug susceptibility.
Main Results:
- HIV-1 RT motif B tolerated substitutions at 10 of 11 positions, including highly conserved residues.
- Several mutants exhibited wild-type infectivity and some showed neutral or beneficial fitness effects.
- Selected variants displayed altered susceptibility to nucleoside analog inhibitors like AZT and 3TC.
Conclusions:
- HIV-1 exhibits significant mutational flexibility in conserved RT residues, challenging assumptions of strict conservation.
- In vivo purifying selection may mask a broader range of viable phenotypic variants.
- This adaptability is a key factor in HIV-1 evolution and response to therapeutic pressures.