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Molecular mechanism by which the K70E mutation in human immunodeficiency virus type 1 reverse transcriptase confers resistance to nucleoside reverse transcriptase inhibitors.

ABSTRACT: The K70E mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has become more prevalent in clinical samples, particularly in isolates derived from patients for whom triple-nucleoside regimens that include tenofovir (TNV), abacavir, and lamivudine (3TC) failed. To elucidate the molecular mechanism by which this mutation confers resistance to these nucleoside RT inhibitors (NRTI), we conducted detailed biochemical analyses comparing wild-type (WT), K70E, and K65R HIV-1 RT. Pre-steady-state kinetic experiments demonstrate that the K70E mutation in HIV-1 RT allows the enzyme to discriminate between the natural deoxynucleoside triphosphate substrate and the NRTI triphosphate (NRTI-TP). Compared to the WT enzyme, K70E RT showed 2.1-, 2.3-, and 3.5-fold-higher levels of resistance toward TNV-diphosphate, carbovir-TP, and 3TC-TP, respectively. By comparison, K65R RT demonstrated 12.4-, 12.0-, and 13.1-fold-higher levels of resistance, respectively, toward the same analogs. NRTI-TP discrimination by the K70E (and K65R) mutation was primarily due to decreased rates of NRTI-TP incorporation and not to changes in analog binding affinity. The K65R and K70E mutations also profoundly impaired the ability of RT to excise 3'-azido-2',3'-dideoxythymidine monophosphate (AZT-MP) and other NRTI-MP from the 3' end of a chain-terminated primer. When introduced into an enzyme with the thymidine analog mutations (TAMs) M41L, L210W, and T215Y, the K70E mutation inhibited ATP-mediated excision of AZT-MP. Taken together, these findings indicate that the K70E mutation, like the K65R mutation, reduces susceptibility to NRTI by selectively decreasing NRTI-TP incorporation and is antagonistic to TAM-mediated nucleotide excision.

SUBMITTER: Sluis-Cremer N

PROVIDER: S-EPMC1797654 | biostudies-literature | 2007 Jan

REPOSITORIES: biostudies-literature

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Molecular mechanism by which the K70E mutation in human immunodeficiency virus type 1 reverse transcriptase confers resistance to nucleoside reverse transcriptase inhibitors.

Sluis-Cremer Nicolas N Sheen Chih-Wei CW Zelina Shannon S Torres Pedro S Argoti PS Parikh Urvi M UM Mellors John W JW

Antimicrobial agents and chemotherapy 20061106 1

The K70E mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has become more prevalent in clinical samples, particularly in isolates derived from patients for whom triple-nucleoside regimens that include tenofovir (TNV), abacavir, and lamivudine (3TC) failed. To elucidate the molecular mechanism by which this mutation confers resistance to these nucleoside RT inhibitors (NRTI), we conducted detailed biochemical analyses comparing wild-type (WT), K70E, and K65R HIV- ...[more]

PMID: 17088490

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Project description:The development of antiviral drug resistance is an important problem in the treatment of human immunodeficiency virus type 1 (HIV-1) infection. Potent antiretroviral therapy is currently used for treatment, and typically consists of at least two reverse transcriptase (RT) inhibitors. We have previously reported that both drugs and drug-resistant RT mutants can increase virus mutation frequencies. To further assess the contributions of nucleoside RT inhibitors (NRTIs), nonnucleoside RT inhibitors (NNRTIs), and drug-resistant RTs to HIV mutagenesis, a new high-throughput assay system was developed. This assay system was designed to specifically detect frameshift mutations in the luciferase gene in a single virus replication cycle. New drug-resistant RTs were identified that significantly altered virus mutation frequencies. Consistent with our previous observations of NRTIs, abacavir, stavudine, and zalcitabine increased HIV-1 mutation frequencies, supporting the general hypothesis that the NRTIs currently used in antiviral drug therapy increase virus mutation frequencies. Interestingly, similar observations were made with NNRTIs. This is the first report to show that NNRTIs can influence virus mutation frequencies. NNRTI combinations, NRTI-NNRTI combinations, and combinations of drug and drug-resistant RTs led to significant changes in the virus mutation frequencies compared to virus replication of drug-resistant virus in the absence of drug or wild-type virus in the presence of drug. This indicates that combinations of RT drugs or drugs and drug-resistant virus created during the evolution of drug resistance can act together to increase HIV-1 mutation frequencies, which would have important implications for drug therapy regimens. Finally, the influence of drug-resistant RT mutants from CRF01_AE viruses on HIV-1 mutation frequencies was analyzed and it was found that only a highly drug resistant RT led to altered virus mutation frequencies. The results further suggest that high-level drug-resistant RT can significantly influence virus mutation frequencies. A structural model that explains the mutation frequency data is discussed.

Project description:We characterized 16 additional mutations in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) whose role in drug resistance is still unknown by analyzing 1,906 plasma-derived HIV-1 subtype B pol sequences from 551 drug-naïve patients and 1,355 nucleoside RT inhibitor (NRTI)-treated patients. Twelve mutations positively associated with NRTI treatment strongly correlated both in pairs and in clusters with known NRTI resistance mutations on divergent evolutionary pathways. In particular, T39A, K43E/Q, K122E, E203K, and H208Y clustered with the nucleoside analogue mutation 1 cluster (NAM1; M41L+L210W+T215Y). Their copresence in this cluster was associated with an increase in thymidine analogue resistance. Moreover, treatment failure in the presence of K43E, K122E, or H208Y was significantly associated with higher viremia and lower CD4 cell count. Differently, D218E clustered with the NAM2 pathway (D67N+K70R+K219Q+T215F), and its presence in this cluster determined an increase in zidovudine resistance. In contrast, three mutations (V35I, I50V, and R83K) negatively associated with NRTI treatment showed negative correlations with NRTI resistance mutations and were associated with increased susceptibility to specific NRTIs. In particular, I50V negatively correlated with the lamivudine-selected mutation M184V and was associated with a decrease in M184V/lamivudine resistance, whereas R83K negatively correlated with both NAM1 and NAM2 clusters and was associated with a decrease in thymidine analogue resistance. Finally, the association pattern of the F214L polymorphism revealed its propensity for the NAM2 pathway and its strong negative association with the NAM1 pathway. Our study provides evidence of novel RT mutational patterns that regulate positively and/or negatively NRTI resistance and strongly suggests that other mutations beyond those currently known to confer resistance should be considered for improved prediction of clinical response to antiretroviral drugs.

Project description:Human immunodeficiency virus type 1 (HIV-1)-specific pyridinone reverse transcriptase (RT) inhibitors prevent HIV-1 replication in cell culture (M. E. Goldman, J. H. Nunberg, J. A. O'Brien, J.C. Quintero, W. A. Schleif, K. F. Freund, S. L. Gaul, W. S. Saari, J. S. Wai, J. M. Hoffman, P. S. Anderson, D. J. Hupe, E. A. Emini, and A. M. Stern, Proc. Natl. Acad. Sci. USA 88:6863-6867, 1991). In contrast to nucleoside analog inhibitors, such as AZT, which need to be converted to triphosphates by host cells, these compounds act directly to inhibit RT via a mechanism which is noncompetitive with respect to deoxynucleoside triphosphates. As one approach to define the mechanism of action of pyridinone inhibitors, we isolated resistant mutants of HIV-1 in cell culture. Serial passage in the presence of inhibitor yielded virus which was 1,000-fold resistant to compounds of this class. Bacterially expressed RTs molecularly cloned from resistant viruses were also resistant. The resistant RT genes encoded two amino acid changes, K-103 to N and Y-181 to C, each of which contributed partial resistance. The mutation at amino acid 181 lies adjacent to the conserved YG/MDD motif found in most DNA and RNA polymerases. The mutation at amino acid 103 lies within a region of RT which may be involved in PPi binding. The resistant viruses, although sensitive to nucleoside analogs, were cross-resistant to the structurally unrelated RT inhibitors TIBO R82150 (R. Pauwels, K. Andries, J. Desmyter, D. Schols, M. J. Kukla, H. J. Breslin, A. Raeymaeckers, J. Van Gelder, R. Woestenborghs, J. Heykanti, K. Schellekens, M. A. C. Janssen, E. De Clercq, and P. A. J. Janssen, Nature [London] 343:470-474, 1990) and BI-RG-587 (V. J. Merluzzi, K. D. Hargrave, M. Labadia, K. Grozinger, M. Skoog, J. C. Wu, C.-K. Shih, K. Eckner, S. Hattox, J. Adams, A. S. Rosenthal, R. Faanes, R. J. Eckner, R. A. Koup, and J. L. Sullivan, Science 250:1411-1413, 1990). Thus, these nonnucleoside analog inhibitors may share a common binding site on RT and may all make up a single pharmacologic class of RT inhibitor. This observation may have important implications for the clinical development of these compounds.

Project description:Nucleoside reverse-transcriptase inhibitor (NRTI) therapy for human immunodeficiency virus (HIV) infection has been associated with mitochondrial DNA (mtDNA) polymerase-gamma inhibition and subsequent mtDNA depletion. Effects on mtDNA mutation, although suggested by critical involvement of polymerase-gamma in DNA-repair reactions, are unknown. In the present study, we assessed the nature and frequency of mitochondrial genome sequence differences in peripheral-blood samples taken prior to NRTI therapy and after 6-77 mo of treatment in 16 NRTI-treated patients. Samples from 10 HIV-infected, treatment-naive control individuals were taken at similar time intervals. Single-stranded conformation polymorphism (SSCP) and DNA-sequencing analysis techniques were used to detect mitochondrial genome sequence variants between paired longitudinal samples, and heteroplasmic populations were quantified after cloning and repeat SSCP/sequencing. Of 16 individuals treated with NRTIs, 5 exhibited altered SSCP profiles associated with the development of novel heteroplasmic DNA sequence changes, whereas no SSCP pattern change within these regions was observed in the control individuals. Heteroplasmic sequence changes were distributed across four regions of the genome: the noncoding region to 12S ribosomal RNA, reduced-nicotinamide-adenine-dinucleotide dehydrogenase 1, and cytochrome oxidase subunits I and III. Of the total of 26 patients who were examined in the present study, 4 of 5 patients with detectable mtDNA sequence changes since commencement of therapy developed evidence of peripheral fat wasting (lipoatrophy) between sample intervals (P=.031). One patient, without detectable sequence changes on NRTI therapy, also developed lipoatrophy. Levels of mtDNA copies/cell in blood samples were determined by quantitative PCR for 11 of the 16 NRTI-exposed patients; 7 of these 11 patients showed reduced levels of mtDNA in blood after therapy, including all 3 patients tested with evidence of mtDNA sequence changes on therapy. These data indicate that NRTI therapy provides conditions permissive for the development of peripheral-blood mtDNA mutations in vivo.

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Molecular mechanism by which the K70E mutation in human immunodeficiency virus type 1 reverse transcriptase confers resistance to nucleoside reverse transcriptase inhibitors.

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Molecular mechanism by which the K70E mutation in human immunodeficiency virus type 1 reverse transcriptase confers resistance to nucleoside reverse transcriptase inhibitors.

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