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Martínez Del Río J, López-Carrobles N, Mendieta-Moreno JI, Herrera-Chacón Ó, Sánchez-Ibáñez A, Mendieta J, Menéndez-Arias L. Charge Engineering of the Nucleic Acid Binding Cleft of a Thermostable HIV-1 Reverse Transcriptase Reveals Key Interactions and a Novel Mechanism of RNase H Inactivation. J Mol Biol 2023; 435:168219. [PMID: 37536391 DOI: 10.1016/j.jmb.2023.168219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 07/26/2023] [Accepted: 07/26/2023] [Indexed: 08/05/2023]
Abstract
Coupled with PCR, reverse transcriptases (RTs) have been widely used for RNA detection and gene expression analysis. Increased thermostability and nucleic acid binding affinity are desirable RT properties to improve yields and sensitivity of these applications. The effects of amino acid substitutions in the RT RNase H domain were tested in an engineered HIV-1 group O RT, containing mutations K358R/A359G/S360A and devoid of RNase H activity due to the presence of E478Q (O3MQ RT). Twenty mutant RTs with Lys or Arg at positions interacting with the template-primer (i.e., at positions 473-477, 499-502 and 505) were obtained and characterized. Most of them produced significant amounts of cDNA at 37, 50 and 65 °C, as determined in RT-PCR reactions. However, a big loss of activity was observed with mutants A477K/R, S499K/R, V502K/R and Y505K/R, particularly at 65 °C. Binding affinity experiments confirmed that residues 477, 502 and 505 were less tolerant to mutations. Amino acid substitutions Q500K and Q500R produced a slight increase of cDNA synthesis efficiency at 50 and 65 °C, without altering the KD for model DNA/DNA and RNA/DNA heteroduplexes. Interestingly, molecular dynamics simulations predicted that those mutations inactivate the RNase H activity by altering the geometry of the catalytic site. Proof of this unexpected effect was obtained after introducing Q500K or Q500R in the wild-type HIV-1BH10 RT and mutant K358R/A359G/S360A RT. Our results reveal a novel mechanism of RNase H inactivation that preserves RT DNA binding and polymerization efficiency without substituting RNase H active site residues.
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Affiliation(s)
- Javier Martínez Del Río
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), c/ Nicolás Cabrera 1, Campus de Cantoblanco-UAM, Madrid, Spain
| | - Nerea López-Carrobles
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), c/ Nicolás Cabrera 1, Campus de Cantoblanco-UAM, Madrid, Spain
| | | | - Óscar Herrera-Chacón
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), c/ Nicolás Cabrera 1, Campus de Cantoblanco-UAM, Madrid, Spain
| | - Adrián Sánchez-Ibáñez
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), c/ Nicolás Cabrera 1, Campus de Cantoblanco-UAM, Madrid, Spain
| | - Jesús Mendieta
- Department of Biotechnology, Universidad Francisco de Vitoria, Pozuelo de Alarcón, Madrid, Spain
| | - Luis Menéndez-Arias
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), c/ Nicolás Cabrera 1, Campus de Cantoblanco-UAM, Madrid, Spain.
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El Bouzidi K, Datir RP, Kwaghe V, Roy S, Frampton D, Breuer J, Ogbanufe O, Murtala-Ibrahim F, Charurat M, Dakum P, Sabin CA, Ndembi N, Gupta RK. Deep sequencing of HIV-1 reveals extensive subtype variation and drug resistance after failure of first-line antiretroviral regimens in Nigeria. J Antimicrob Chemother 2021; 77:474-482. [PMID: 34741609 PMCID: PMC8809188 DOI: 10.1093/jac/dkab385] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 09/28/2021] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Deep sequencing could improve understanding of HIV treatment failure and viral population dynamics. However, this tool is often inaccessible in low- and middle-income countries. OBJECTIVES To determine the genetic patterns of resistance emerging in West African HIV-1 subtypes during first-line virological failure, and the implications for future antiretroviral options. PATIENTS AND METHODS Participants were selected from a Nigerian cohort of people living with HIV who had failed first-line ART and subsequently switched to second-line therapy. Whole HIV-1 genome sequences were generated from first-line virological failure samples with Illumina MiSeq. Mutations detected at ≥2% frequency were analysed and compared by subtype. RESULTS HIV-1 sequences were obtained from 101 participants (65% female, median age 30 years, median 32.9 months of nevirapine- or efavirenz-based ART). Thymidine analogue mutations (TAMs) were detected in 61%, other core NRTI mutations in 92% and NNRTI mutations in 99%. Minority variants (<20% frequency) comprised 18% of all mutations. K65R was more prevalent in CRF02_AG than G subtypes (33% versus 7%; P = 0.002), and ≥3 TAMs were more common in G than CRF02_AG (52% versus 24%; P = 0.004). Subtype G viruses also contained more RT cleavage site mutations. Cross-resistance to at least one of the newer NNRTIs, doravirine, etravirine or rilpivirine, was predicted in 81% of participants. CONCLUSIONS Extensive drug resistance had accumulated in people with West African HIV-1 subtypes, prior to second-line ART. Deep sequencing significantly increased the detection of resistance-associated mutations. Caution should be used if considering newer-generation NNRTI agents in this setting.
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Affiliation(s)
- Kate El Bouzidi
- Division of Infection & Immunity, University College London, London, UK.,Institute for Global Health, University College London, London, UK
| | - Rawlings P Datir
- Cambridge Institute of Therapeutic Immunology and Infectious Diseases, University of Cambridge, Cambridge, UK
| | - Vivian Kwaghe
- University of Abuja Teaching Hospital, Abuja, Nigeria
| | - Sunando Roy
- Division of Infection & Immunity, University College London, London, UK
| | - Dan Frampton
- Division of Infection & Immunity, University College London, London, UK.,Farr Institute of Health Informatics Research, University College London, London, UK
| | - Judith Breuer
- Division of Infection & Immunity, University College London, London, UK
| | - Obinna Ogbanufe
- U.S. Centers for Disease Control and Prevention, U.S. Embassy, Abuja, Nigeria
| | | | - Man Charurat
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, USA
| | | | - Caroline A Sabin
- Institute for Global Health, University College London, London, UK
| | - Nicaise Ndembi
- Institute of Human Virology Nigeria, Abuja, Nigeria.,Africa Centres for Disease Control and Prevention, African Union Commission, Addis Ababa, Ethiopia
| | - Ravindra K Gupta
- Cambridge Institute of Therapeutic Immunology and Infectious Diseases, University of Cambridge, Cambridge, UK.,Africa Health Research Institute, Durban, South Africa
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Large Multidomain Protein NMR: HIV-1 Reverse Transcriptase Precursor in Solution. Int J Mol Sci 2020; 21:ijms21249545. [PMID: 33333923 PMCID: PMC7765405 DOI: 10.3390/ijms21249545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Revised: 12/10/2020] [Accepted: 12/12/2020] [Indexed: 11/17/2022] Open
Abstract
NMR studies of large proteins, over 100 kDa, in solution are technically challenging and, therefore, of considerable interest in the biophysics field. The challenge arises because the molecular tumbling of a protein in solution considerably slows as molecular mass increases, reducing the ability to detect resonances. In fact, the typical 1H-13C or 1H-15N correlation spectrum of a large protein, using a 13C- or 15N-uniformly labeled protein, shows severe line-broadening and signal overlap. Selective isotope labeling of methyl groups is a useful strategy to reduce these issues, however, the reduction in the number of signals that goes hand-in-hand with such a strategy is, in turn, disadvantageous for characterizing the overall features of the protein. When domain motion exists in large proteins, the domain motion differently affects backbone amide signals and methyl groups. Thus, the use of multiple NMR probes, such as 1H, 19F, 13C, and 15N, is ideal to gain overall structural or dynamical information for large proteins. We discuss the utility of observing different NMR nuclei when characterizing a large protein, namely, the 66 kDa multi-domain HIV-1 reverse transcriptase that forms a homodimer in solution. Importantly, we present a biophysical approach, complemented by biochemical assays, to understand not only the homodimer, p66/p66, but also the conformational changes that contribute to its maturation to a heterodimer, p66/p51, upon HIV-1 protease cleavage.
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Ilina T, Slack RL, Guerrero M, Ishima R. Effect of Lysyl-tRNA Synthetase on the Maturation of HIV-1 Reverse Transcriptase. ACS OMEGA 2020; 5:16619-16627. [PMID: 32685828 PMCID: PMC7364630 DOI: 10.1021/acsomega.0c01449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 06/17/2020] [Indexed: 06/11/2023]
Abstract
In human immunodeficiency virus-1 (HIV-1), reverse transcriptase (RT) is encoded as a 66 kDa protein, p66, in the Gag-Pol polyprotein. This protein is proteolytically cleaved by HIV-1 protease (PR) to finally generate a mature RT that is a heterodimer, composed of a p66 subunit and a p66-derived 51 kDa subunit, p51. In our prior work, we demonstrated that tRNALys3 binding to p66/p66 facilitates efficient cleavage of p66 to p51 by PR. However, tRNALys3 is known to be recruited to the virus by forming a complex with lysyl-tRNA synthetase (LysRS). Herein, we tested whether LysRS can have an effect on RT maturation in vitro. Importantly, our data show no significant differences in RT maturation in the presence of LysRS. Furthermore, no apparent p66/66 interaction with LysRS was observed. Although PR cleaved LysRS, it did not immediately release tRNALys3 from LysRS. Thus, we conclude that a free fraction of tRNALys3, which is in equilibrium with a LysRS-bound form, interacts with p66/p66 without any additional mechanism involving release of tRNALys3 from LysRS. Given that only transient tRNALys3-p66/p66 interaction is needed for efficient RT maturation, a small amount of free tRNA may be sufficient for this process. These studies reveal molecular level insights into RT maturation and will be useful for the design of cellular/viral experiments to better understand the role of tRNA in HIV-1 replication.
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Slack RL, Ilina TV, Xi Z, Giacobbi NS, Kawai G, Parniak MA, Sarafianos SG, Sluis Cremer N, Ishima R. Conformational Changes in HIV-1 Reverse Transcriptase that Facilitate Its Maturation. Structure 2019; 27:1581-1593.e3. [PMID: 31471129 DOI: 10.1016/j.str.2019.08.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 07/10/2019] [Accepted: 08/09/2019] [Indexed: 01/18/2023]
Abstract
HIV-1 reverse transcriptase (RT) is translated as part of the Gag-Pol polyprotein that is proteolytically processed by HIV-1 protease (PR) to finally become a mature heterodimer, composed of a p66 and a p66-derived 51-kDa subunit, p51. Our previous work suggested that tRNALys3 binding to p66/p66 introduces conformational changes in the ribonuclease (RNH) domain of RT that facilitate efficient cleavage of p66 to p51 by PR. In this study, we characterized the conformational changes in the RNH domain of p66/p66 imparted by tRNALys3 using NMR. Moreover, the importance of tRNALys3 in RT maturation was confirmed in cellulo by modulating the levels of Lys-tRNA synthetase, which affects recruitment of tRNALys3 to the virus. We also employed nonnucleoside RT inhibitors, to modulate the p66 dimer-monomer equilibrium and monitor the resulting structural changes. Taken together, our data provide unique insights into the conformational changes in p66/p66 that drive PR cleavage.
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Affiliation(s)
- Ryan L Slack
- Department of Structural Biology, University of Pittsburgh School of Medicine, Room 1037, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Tatiana V Ilina
- Department of Structural Biology, University of Pittsburgh School of Medicine, Room 1037, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Zhaoyong Xi
- Department of Structural Biology, University of Pittsburgh School of Medicine, Room 1037, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Nicholas S Giacobbi
- Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Gota Kawai
- Department of Life and Environmental Sciences, Chiba Institute of Technology, Chiba, Japan
| | - Michael A Parniak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
| | - Stefan G Sarafianos
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Nicolas Sluis Cremer
- Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
| | - Rieko Ishima
- Department of Structural Biology, University of Pittsburgh School of Medicine, Room 1037, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA.
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Gong T, Patel SK, Parniak MA, Ballou B, Rohan LC. Nanocrystal Formulation Improves Vaginal Delivery of CSIC for HIV Prevention. AAPS PharmSciTech 2019; 20:286. [PMID: 31410664 DOI: 10.1208/s12249-019-1503-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 08/03/2019] [Indexed: 12/31/2022] Open
Abstract
5-Chloro-3-phenylsulfonylindole-2-carboxamide (CSIC) is a highly potent non-nucleoside reverse transcriptase inhibitor (NNRTI) with potential for use in topical prophylaxis against HIV transmission. However, the hydrophobic nature of CSIC limits its administration through vaginal route. In this study, we developed nanocrystals of CSIC to potentially improve the aqueous solubility and intracellular uptake of CSIC in vitro and in vivo. CSIC nanocrystals were manufactured and stabilized with Pluronic F98 and hydroxypropyl methylcellulose E5. Transmission electron microscopy showed CSIC nanocrystals to be needle-like. Dynamic light scattering measurements showed a hydrodynamic size of 243 nm (polydispersity index < 0.3) and near neutral surface charge (- 7.8 mV). Particle size was maintained for at least 7 days in the liquid state and for at least 5 months after lyophilization. Drug content in the CSIC nanocrystal formulation (nanosuspension) was 0.8 mg/mL, which is 1000 times higher than the aqueous solubility of CSIC. In vitro release study showed that over 90% of CSIC was released from the nanocrystal formulation in a linear fashion over a period of 4 days. Importantly, CSIC nanocrystals showed equivalent cell-based anti-HIV activity (EC50 ~ 1 nM) as that of non-formulated drug. In vitro studies demonstrated rapid macrophage uptake of CSIC nanocrystals via both energy-dependent (endocytosis) and independent processes. In vivo studies in Swiss Webster female mice showed that the nanocrystal formulation significantly improved CSIC delivery to mouse cervicovaginal tissues following intravaginal instillation. In summary, nanocrystals are a promising formulation approach for topical delivery of CSIC for protection against HIV sexual transmission.
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Ilina TV, Slack RL, Elder JH, Sarafianos SG, Parniak MA, Ishima R. Effect of tRNA on the Maturation of HIV-1 Reverse Transcriptase. J Mol Biol 2018; 430:1891-1900. [PMID: 29751015 PMCID: PMC5988984 DOI: 10.1016/j.jmb.2018.02.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/21/2018] [Accepted: 02/22/2018] [Indexed: 11/21/2022]
Abstract
The mature HIV-1 reverse transcriptase is a heterodimer that comprises 66 kDa (p66) and 51 kDa (p51) subunits. The latter is formed by HIV-1 protease-catalyzed removal of a C-terminal ribonuclease H domain from a p66 subunit. This proteolytic processing is a critical step in virus maturation and essential for viral infectivity. Here, we report that tRNA significantly enhances in vitro processing even at a substoichiometric tRNA:p66/p66 ratio. Other double-stranded RNAs have considerably less pronounced effect. Our data support a model where interaction of p66/p66 with tRNA introduces conformational asymmetry in the two subunits, permitting specific proteolytic processing of one p66 to provide the mature RT p66/p51 heterodimer.
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Affiliation(s)
- Tatiana V Ilina
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, United States; Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, United States
| | - Ryan L Slack
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, United States
| | - John H Elder
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, United States
| | - Stefan G Sarafianos
- Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Michael A Parniak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, United States
| | - Rieko Ishima
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, United States.
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8
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Structural Maturation of HIV-1 Reverse Transcriptase-A Metamorphic Solution to Genomic Instability. Viruses 2016; 8:v8100260. [PMID: 27690082 PMCID: PMC5086598 DOI: 10.3390/v8100260] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/12/2016] [Indexed: 12/13/2022] Open
Abstract
Human immunodeficiency virus 1 (HIV-1) reverse transcriptase (RT)—a critical enzyme of the viral life cycle—undergoes a complex maturation process, required so that a pair of p66 precursor proteins can develop conformationally along different pathways, one evolving to form active polymerase and ribonuclease H (RH) domains, while the second forms a non-functional polymerase and a proteolyzed RH domain. These parallel maturation pathways rely on the structural ambiguity of a metamorphic polymerase domain, for which the sequence–structure relationship is not unique. Recent nuclear magnetic resonance (NMR) studies utilizing selective labeling techniques, and structural characterization of the p66 monomer precursor have provided important insights into the details of this maturation pathway, revealing many aspects of the three major steps involved: (1) domain rearrangement; (2) dimerization; and (3) subunit-selective RH domain proteolysis. This review summarizes the major structural changes that occur during the maturation process. We also highlight how mutations, often viewed within the context of the mature RT heterodimer, can exert a major influence on maturation and dimerization. It is further suggested that several steps in the RT maturation pathway may provide attractive targets for drug development.
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Raghwani J, Bhatt S, Pybus OG. Faster Adaptation in Smaller Populations: Counterintuitive Evolution of HIV during Childhood Infection. PLoS Comput Biol 2016; 12:e1004694. [PMID: 26741359 PMCID: PMC4704780 DOI: 10.1371/journal.pcbi.1004694] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 12/07/2015] [Indexed: 12/17/2022] Open
Abstract
Analysis of HIV-1 gene sequences sampled longitudinally from infected individuals can reveal the evolutionary dynamics that underlie associations between disease outcome and viral genetic diversity and divergence. Here we extend a statistical framework to estimate rates of viral molecular adaptation by considering sampling error when computing nucleotide site-frequencies. This is particularly beneficial when analyzing viral sequences from within-host viral infections if the number of sequences per time point is limited. To demonstrate the utility of this approach, we apply our method to a cohort of 24 patients infected with HIV-1 at birth. Our approach finds that viral adaptation arising from recurrent positive natural selection is associated with the rate of HIV-1 disease progression, in contrast to previous analyses of these data that found no significant association. Most surprisingly, we discover a strong negative correlation between viral population size and the rate of viral adaptation, the opposite of that predicted by standard molecular evolutionary theory. We argue that this observation is most likely due to the existence of a confounding third variable, namely variation in selective pressure among hosts. A conceptual non-linear model of virus adaptation that incorporates the two opposing effects of host immunity on the virus population can explain this counterintuitive result. Since some common approaches to the study of molecular adaptation may not be optimal for answering questions regarding within-host virus evolution, we have developed an alternative approach that estimates an absolute rate of molecular adaptation from serially-sampled viral populations. Here, we extend this framework to include sampling error when estimating the rate of adaptation, which is an important addition when analyzing historical data sets obtained in the pre-HAART era, for which the number of sequences per time point is often limited. We applied this extended method to a cohort of 24 pediatric HIV-1 patients and discovered that viral adaptation is strongly associated with the rate of disease progression, which is in contrast to previous analyses of these data that did not find a significant association. Strikingly, this results in a negative relationship between the rate of viral adaptation and viral population size, which is unexpected under standard micro-evolutionary models since larger populations are predicted to fix more mutations per unit time than smaller populations. Our findings indicate that the negative correlation is unlikely to be driven by relaxation of selective constraint, but instead by significant variation in host immune responses. Consequently, this supports a previously proposed non-linear model of viral adaptation in which host immunity imposes counteracting effects on population size and selection.
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Affiliation(s)
- Jayna Raghwani
- Department of Zoology, University of Oxford, South Parks Road, Oxford, United Kingdom
- * E-mail: (JR); (OGP)
| | - Samir Bhatt
- Department of Zoology, University of Oxford, South Parks Road, Oxford, United Kingdom
| | - Oliver G. Pybus
- Department of Zoology, University of Oxford, South Parks Road, Oxford, United Kingdom
- * E-mail: (JR); (OGP)
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Slack RL, Spiriti J, Ahn J, Parniak MA, Zuckerman DM, Ishima R. Structural integrity of the ribonuclease H domain in HIV-1 reverse transcriptase. Proteins 2015; 83:1526-38. [PMID: 26061827 DOI: 10.1002/prot.24843] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 05/14/2015] [Accepted: 06/03/2015] [Indexed: 02/06/2023]
Abstract
The mature form of reverse transcriptase (RT) is a heterodimer comprising the intact 66-kDa subunit (p66) and a smaller 51-kDa subunit (p51) that is generated by removal of most of the RNase H (RNH) domain from a p66 subunit by proteolytic cleavage between residues 440 and 441. Viral infectivity is eliminated by mutations such as F440A and E438N in the proteolytic cleavage sequence, while normal processing and virus infectivity are restored by a compensatory mutation, T477A, that is located more than 10 Å away from the processing site. The molecular basis for this compensatory effect has remained unclear. We therefore investigated structural characteristics of RNH mutants using computational and experimental approaches. Our Nuclear Magnetic Resonance and Differential Scanning Fluorimetry results show that both F440A and E438N mutations disrupt RNH folding. Addition of the T477A mutation restores correct folding of the RNH domain despite the presence of the F440A or E438N mutations. Molecular dynamics simulations suggest that the T477A mutation affects the processing site by altering relative orientations of secondary structure elements. Predictions of sequence tolerance suggest that phenylalanine and tyrosine are structurally preferred at residues 440 and 441, respectively, which are the P1 and P1' substrate residues known to require bulky side chains for substrate specificity. Interestingly, our study demonstrates that the processing site residues, which are critical for protease substrate specificity and must be exposed to the solvent for efficient processing, also function to maintain proper RNH folding in the p66/p51 heterodimer.
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Affiliation(s)
- Ryan L Slack
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
| | - Justin Spiriti
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
| | - Michael A Parniak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
| | - Daniel M Zuckerman
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
| | - Rieko Ishima
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15260
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Vaginal Microbicide Film Combinations of Two Reverse Transcriptase Inhibitors, EFdA and CSIC, for the Prevention of HIV-1 Sexual Transmission. Pharm Res 2015; 32:2960-72. [PMID: 25794967 DOI: 10.1007/s11095-015-1678-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 03/12/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE EFdA is a potent nucleoside reverse transcriptase inhibitor (NRTI) with activity against a wide spectrum of wild-type and drug resistant HIV-1 variants. CSIC is a tight-binding non-nucleoside reverse transcriptase inhibitor (NNRTI) with demonstrated anti-HIV properties important for use in topical prevention of HIV transmission. The objective of this study was to develop and characterize film-formulated EFdA and CSIC for use as a female-controlled vaginal microbicide to prevent sexual transmission of HIV. METHODS Assessments of EFdA- and CSIC-loaded films included physicochemical characteristics, in vitro cytotoxicity, epithelia integrity studies, compatibility with the normal vaginal Lactobacillus flora and anti-HIV bioactivity evaluations. RESULTS No significant change in physicochemical properties or biological activity of the combination films were noted during 3 months storage. In vitro cytotoxicity and bioactivity testing showed that 50% cytotoxic concentration (CC50) of either EFdA or CSIC was several orders of magnitude higher than the 50% effective concentration (EC50) values. Film-formulated EFdA and CSIC combination showed additive inhibitory activity against wild type and drug-resistant variants of HIV. Epithelial integrity studies demonstrated that the combination vaginal film had a much lower toxicity to HEC-1A monolayers compared to that of VCF®, a commercial vaginal film product containing nonoxynol-9. Polarized ectocervical explants showed films with drug alone or in combination were effective at preventing HIV infection. CONCLUSIONS Our data suggest that vaginal microbicide films containing a combination of the NRTI EFdA and the NNRTI CSIC have potential to prevent HIV-1 sexual transmission.
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The nature of the N-terminal amino acid residue of HIV-1 RNase H is critical for the stability of reverse transcriptase in viral particles. J Virol 2014; 89:1286-97. [PMID: 25392207 DOI: 10.1128/jvi.02312-14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) is synthesized and packaged into the virion as a part of the GagPol polyprotein. Mature RT is released by the action of viral protease. However, unlike other viral proteins, RT is subject to an internal cleavage event leading to the formation of two subunits in the virion: a p66 subunit and a p51 subunit that lacks the RNase H domain. We have previously identified RNase H to be an HIV-1 protein that has the potential to be a substrate for the N-end rule pathway, which is an ubiquitin-dependent proteolytic system in which the identity of the N-terminal amino acid determines the half-life of a protein. Here we examined the importance of the N-terminal amino acid residue of RNase H in the early life cycle of HIV-1. We show that changing this residue to an amino acid structurally different from the conserved residue leads to the degradation of RT and, in some cases, integrase in the virus particle and this abolishes infectivity. Using intravirion complementation and in vitro protease cleavage assays, we show that degradation of RT in RNase H N-terminal mutants occurs in the absence of active viral protease in the virion. Our results also indicate the importance of the RNase H N-terminal residue in the dimerization of RT subunits. IMPORTANCE HIV-1 proteins are initially made as part of a polyprotein that is cleaved by the viral protease into the proteins that form the virus particle. We were interested in one particular protein, RNase H, that is cleaved from reverse transcriptase. In particular, we found that the first amino acid of RNase H never varied in over 1,850 isolates of HIV-1 that we compared. When we changed the first amino acid, we found that the reverse transcriptase in the virus was degraded. While other studies have implied that the viral protease can degrade mutant RT proteins, we show here that this may not be the case for our mutants. Our results suggest that the presence of active viral protease is not required for the degradation of RT in RNase H N-terminal mutants, suggesting a role for a cellular protease in this process.
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Akil A, Parniak MA, Dezzuitti CS, Moncla BJ, Cost MR, Li M, Rohan LC. Development and Characterization of a Vaginal Film Containing Dapivirine, a Non- nucleoside Reverse Transcriptase Inhibitor (NNRTI), for prevention of HIV-1 sexual transmission. Drug Deliv Transl Res 2011; 1:209-222. [PMID: 22708075 DOI: 10.1007/s13346-011-0022-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Dapivirine, a non-nucleoside reverse transcriptase inhibitor, is a potent and promising anti-HIV molecule. It is currently being investigated for use as a vaginal microbicide in two dosage forms, a semi-solid gel and a silicone elastomer ring. Quick-dissolving films are promising and attractive dosage forms that may provide an alternative platform for the vaginal delivery of microbicide drug candidates. Vaginal films may provide advantages such as discreet use, no product leakage during use, lack of requirement for an applicator for insertion, rapid drug release and minimal packaging and reduced wastage. Within this study the in vitro bioactivity of dapivirine as compared to the NNRTI UC781 was further established and a quick dissolve film was developed for vaginal application of dapivirine for prevention of HIV infection. The developed film was characterized with respect to its physical and chemical attributes including water content, mechanical strength, drug release profile, permeability, compatibility with lactobacilli and bioactivity. The anti-HIV activity of the formulated dapivirine film was confirmed in in vitro and ex vivo models. Importantly the physical and chemical properties of the film as well as its bioactivity were maintained for a period of 18 months. In conclusion, a vaginal film containing dapivirine was developed and characterized. The film was shown to prevent HIV-1 infection in vitro and ex vivo and have acceptable characteristics which make this film a promising candidate for testing as vaginal microbicide.
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Affiliation(s)
- Ayman Akil
- Magee-Womens Research Institute, Pittsburgh, Pennsylvania, USA
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