Structure and Function of HIV-1 Reverse Transcriptase: Molecular Mechanisms of Polymerization and Inhibition

Christopher Bond Life Sciences Center, Department of Molecular Microbiology & Immunology, University of Missouri School of Medicine, Columbia, MO 65211, USA.
Journal of Molecular Biology (Impact Factor: 4.33). 12/2008; 385(3):693-713. DOI: 10.1016/j.jmb.2008.10.071
Source: PubMed

ABSTRACT The rapid replication of HIV-1 and the errors made during viral replication cause the virus to evolve rapidly in patients, making the problems of vaccine development and drug therapy particularly challenging. In the absence of an effective vaccine, drugs are the only useful treatment. Anti-HIV drugs work; so far drug therapy has saved more than three million years of life. Unfortunately, HIV-1 develops resistance to all of the available drugs. Although a number of useful anti-HIV drugs have been approved for use in patients, the problems associated with drug toxicity and the development of resistance means that the search for new drugs is an ongoing process. The three viral enzymes, reverse transcriptase (RT), integrase (IN), and protease (PR) are all good drug targets. Two distinct types of RT inhibitors, both of which block the polymerase activity of RT, have been approved to treat HIV-1 infections, nucleoside analogs (NRTIs) and nonnucleosides (NNRTIs), and there are promising leads for compounds that either block the RNase H activity or block the polymerase in other ways. A better understanding of the structure and function(s) of RT and of the mechanism(s) of inhibition can be used to generate better drugs; in particular, drugs that are effective against the current drug-resistant strains of HIV-1.

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Available from: Kalyan Das, Aug 22, 2015
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    • "Reverse transcription and reverse transcriptases All retroviruses, as well as retrotransposons, undergo a unique DNA synthesis process called reverse transcription, which converts single stranded RNA genomes into double stranded DNA. This process is catalyzed by virally encoded DNA polymerases, reverse transcriptases (RT) (reviewed in Hu and Hughes, 2012; Sarafianos et al., 2009). Unlike cellular DNA polymerases, which synthesize DNA from DNA templates, RTs can execute DNA polymerization from RNA templates as well. "
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    ABSTRACT: Retroviruses consume cellular deoxynucleoside triphosphates (dNTPs) to convert their RNA genomes into proviral DNA through reverse transcription. While all retroviruses replicate in dividing cells, lentiviruses uniquely replicate in nondividing cells such as macrophages. Importantly, dNTP levels in nondividing cells are extremely low, compared to dividing cells. Indeed, a recently discovered anti-HIV/SIV restriction factor, SAMHD1, which is a dNTP triphosphohydrolase, is responsible for the limited dNTP pool of nondividing cells. Lentiviral reverse transcriptases (RT) uniquely stay functional even at the low dNTP concentrations in nondividing cells. Interestingly, Vpx of HIV-2/SIVsm proteosomally degrades SAMHD1, which elevates cellular dNTP pools and accelerates lentiviral replication in nondividing cells. These Vpx-encoding lentiviruses rapidly replicate in nondividing cells by encoding both highly functional RTs and Vpx. Here, we discuss a series of mechanistic and virological studies that have contributed to conceptually linking cellular dNTP levels and the adaptation of lentiviral replication in nondividing cells.
    Virology 12/2012; 436(2). DOI:10.1016/j.virol.2012.11.010 · 3.28 Impact Factor
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    • "Reverse transcription consists of a complex series of reactions that culminate in conversion of the single-stranded viral RNA genome into a linear, double-stranded DNA copy that is ultimately integrated into host chromosomal DNA (reviewed in Herschhorn and Hizi, 2010; Sarafianos et al., 2009). This process is catalyzed by the viral reverse transcriptase (RT) enzyme (Baltimore, 1970; Mizutani et al., 1970). "
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    ABSTRACT: During (-) strong-stop DNA [(-) SSDNA] synthesis, RNase H cleavage of genomic viral RNA generates small 5'-terminal RNA fragments (14 to 18 nt) that remain annealed to the DNA. Unless these fragments are removed, the minus-strand transfer reaction, required for (-) SSDNA elongation, cannot occur. Here, we describe the mechanism of 5'-terminal RNA removal and the roles of HIV-1 nucleocapsid protein (NC) and RNase H cleavage in this process. Using an NC-dependent system that models minus-strand transfer, we show that the presence of short terminal fragments pre-annealed to (-) SSDNA has no impact on strand transfer, implying efficient fragment removal. Moreover, in reactions with an RNase H(-) reverse transcriptase mutant, NC alone is able to facilitate fragment removal, albeit less efficiently than in the presence of both RNase H activity and NC. Results obtained from novel electrophoretic gel mobility shift and Förster Resonance Energy Transfer assays, which each directly measure RNA fragment release from a duplex in the absence of DNA synthesis, demonstrate for the first time that the architectural integrity of NC's zinc finger (ZF) domains is absolutely required for this reaction. This suggests that NC's helix destabilizing activity (associated with the ZFs) facilitates strand exchange through the displacement of these short terminal RNAs by the longer 3' acceptor RNA, which forms a more stable duplex with (-) SSDNA. Taken together with previously published results, we conclude that NC-mediated fragment removal is linked mechanistically with selection of the correct primer for plus-strand DNA synthesis and the tRNA removal step prior to plus-strand transfer. Thus, HIV-1 has evolved a single mechanism for the three RNA removal reactions that are critical for successful reverse transcription.
    Virus Research 11/2012; 171(2). DOI:10.1016/j.virusres.2012.08.013 · 2.83 Impact Factor
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    • "The synthesis of the DNA first strand is initiated from the region of polypurine from the genomic RNA that is resistant to RNase-H and that remains on the new negative strand of DNA (-). All other reverse transcription steps include elongation of the primer DNA (Brautigam & Steitz, 1998; Sarafianos et al., 2009). HIV-1 RT has the ability to interact with substrates of different conformational structures (doublestranded DNA and single stranded RNA), but with low fidelity or processing capacity. "
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    ABSTRACT: HIV-1 reverse transcriptase (HIV-1 RT) is a therapeutic target for the treatment of HIV-positive individuals or those already showing AIDS symptoms. In this perspective, the identification of new inhibitors for this enzyme is of great importance in view of the growing viral resistance to the existing treatments. This resistance has compromised the quality of life of those infected with multidrug-resistant strains, whose treatment options are already limited, putting at risk these individuals lives. The literature has recognized marine organisms and their products as natural sources for the identification of new therapeutic options for different pathologies. In this brief review, we consider the structure of HIV-1 RT and its most common inhibitors, as well as some marine diterpenes originally reported as HIV-1 RT inhibitors to encourage the identification and development of new marine antiviral prototypes.
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