Structural and Functional Studies of the Promoter Element for Dengue Virus RNA Replication

ABSTRACT The 5′ untranslated region (5′UTR) of the dengue virus (DENV) genome contains two defined elements essential for viral replication. At the 5′ end, a large stem-loop (SLA) structure functions as the promoter for viral polymerase activity. Next to the SLA, there is a short stem-loop that contains a cyclization sequence known as the 5′ upstream AUG region (5′UAR). Here, we analyzed the secondary structure of the SLA in solution and the structural requirements of this element for viral replication. Using infectious DENV clones, viral replicons, and in vitro polymerase assays, we defined two helical regions, a side stem-loop, a top loop, and a U bulge within SLA as crucial elements for viral replication. The determinants for SLA-polymerase recognition were found to be common in different DENV serotypes. In addition, structural elements within the SLA required for DENV RNA replication were also conserved among different mosquito- and tick-borne flavivirus genomes, suggesting possible common strategies for polymerase-promoter recognition in flaviviruses. Furthermore, a conserved oligo(U) track present downstream of the SLA was found to modulate RNA synthesis in transfected cells. In vitro polymerase assays indicated that a sequence of at least 10 residues following the SLA, upstream of the 5′UAR, was necessary for efficient RNA synthesis using the viral 3′UTR as template.

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Interplay of RNA Elements in the Dengue Virus 5′ and 3′ Ends Required for Viral RNA Replication

Journal of Virology ◽

10.1128/jvi.02042-09 ◽

2010 ◽

Vol 84 (12) ◽

pp. 6103-6118 ◽

Cited By ~ 93

Author(s):

Peter Friebe ◽

Eva Harris

Keyword(s):

Dengue Virus ◽

Rna Structure ◽

Rna Synthesis ◽

Rna Replication ◽

Viral Rna ◽

Coding Region ◽

Stem Loop ◽

Complementary Sequences ◽

Translation Start ◽

Rna Elements

ABSTRACT Dengue virus (DENV) is a member of the Flavivirus genus of positive-sense RNA viruses. DENV RNA replication requires cyclization of the viral genome mediated by two pairs of complementary sequences in the 5′ and 3′ ends, designated 5′ and 3′ cyclization sequences (5′-3′ CS) and the 5′ and 3′ upstream of AUG region (5′-3′ UAR). Here, we demonstrate that another stretch of six nucleotides in the 5′ end is involved in DENV replication and possibly genome cyclization. This new sequence is located downstream of the AUG, designated the 5′ downstream AUG region (5′ DAR); the motif predicted to be complementary in the 3′ end is termed the 3′ DAR. In addition to the UAR, CS and DAR motifs, two other RNA elements are located at the 5′ end of the viral RNA: the 5′ stem-loop A (5′ SLA) interacts with the viral RNA-dependent RNA polymerase and promotes RNA synthesis, and a stem-loop in the coding region named cHP is involved in translation start site selection as well as RNA replication. We analyzed the interplay of these 5′ RNA elements in relation to RNA replication, and our data indicate that two separate functional units are formed; one consists of the SLA, and the other includes the UAR, DAR, cHP, and CS elements. The SLA must be located at the 5′ end of the genome, whereas the position of the second unit is more flexible. We also show that the UAR, DAR, cHP, and CS must act in concert and therefore likely function together to form the tertiary RNA structure of the circularized DENV genome.

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A conserved arginine in NS5 binds genomic 3’stem-loop RNA for primer-independent initiation of flavivirus RNA-replication

RNA ◽

10.1261/rna.078949.121 ◽

2021 ◽

pp. rna.078949.121

Author(s):

Sai Wang ◽

Kitt Wing Ki Chan ◽

Min Jie Alvin Tan ◽

Charlotte Flory ◽

Dahai Luo ◽

...

Keyword(s):

Protein Interactions ◽

De Novo ◽

Rna Replication ◽

Polymerase Activity ◽

Structural Protein ◽

Binding Studies ◽

Stem Loop ◽

Cis Acting ◽

Rna Polymerase Activity

Replication of the RNA genome of flaviviruses without a primer involves RNA-protein interactions that have been shown to include the recognition of the stem-loop A (SLA) in the 5’ untranslated region (UTR) by the non-structural protein 5 (NS5). We show that DENV2 NS5 arginine 888, located within the C-terminal 18 residues, is completely conserved in all flaviviruses and interacts specifically with the top-loop of 3’SL in the 3’UTR which contains the pentanucleotide 5’-CACAG-3’ previously shown to be critical for flavivirus RNA replication. We present virological and biochemical data showing the importance of this Arg 888 in virus viability and de novo initiation of RNA polymerase activity in vitro. Based on our binding studies, we hypothesize that ternary complex formation of NS5 with 3’SL, followed by dimerization, leads to the formation of the de novo initiation complex that could be regulated by the reversible zipping and unzipping of cis-acting RNA elements.

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Evaluation of AT-752, a double prodrug of a guanosine nucleotide analog with in vitro and in vivo activity against dengue and other flaviviruses

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00988-21 ◽

2021 ◽

Author(s):

Steven S. Good ◽

Ashleigh Shannon ◽

Kai Lin ◽

Adel Moussa ◽

Justin G. Julander ◽

...

Keyword(s):

Dengue Virus ◽

Viral Replication ◽

Mononuclear Cells ◽

Potent Inhibitor ◽

Denv Infection ◽

Peripheral Blood Mononuclear ◽

Denv Serotypes ◽

Nucleotide Analog

Every year millions of people worldwide are infected with dengue virus (DENV), with a significant number developing severe life-threatening disease. There are currently no broadly indicated vaccines or therapeutics available for treatment of DENV infection. Here, we show that AT-281, the free base of AT-752, an orally available double prodrug of a guanosine nucleotide analog, was a potent inhibitor of DENV serotypes 2 and 3 in vitro , requiring concentrations of 0.48 and 0.77 μM, respectively, to inhibit viral replication by 50% (EC 50 ) in Huh-7 cells. AT-281 was also a potent inhibitor of all other flaviviruses tested with EC 50 values ranging from 0.19 to 1.41 μM. Little to no cytotoxicity was observed for AT-281 at concentrations up to 170 μM. After oral administration of AT-752, substantial levels of the active triphosphate metabolite AT-9010 were formed in vivo in peripheral blood mononuclear cells of mice, rats and monkeys. Furthermore, AT-9010 competed with guanosine triphosphate in RNA template-primer elongation assays with DENV-2 RNA polymerase, which is essential for viral replication, with incorporation of AT-9010 resulting in termination of RNA synthesis. In AG129 mice infected with DENV D2Y98P, treatment with AT-752 significantly reduced viremia and morbidity and increased survival. The demonstrated in vitro and in vivo activity of AT-752 suggest that it is a promising compound for the treatment of dengue virus infection, and is currently under evaluation in clinical studies.

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Efficient and Specific Initiation of Subgenomic RNA Synthesis by Cucumber Mosaic Virus Replicase In Vitro Requires an Upstream RNA Stem-Loop

Journal of Virology ◽

10.1128/jvi.74.23.11201-11209.2000 ◽

2000 ◽

Vol 74 (23) ◽

pp. 11201-11209 ◽

Cited By ~ 18

Author(s):

M.-H. Chen ◽

M. J. Roossinck ◽

C. C. Kao

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Rna Synthesis ◽

Core Promoter ◽

Brome Mosaic Virus ◽

Stem Loop ◽

Promoter Sequences ◽

Promoter Recognition

ABSTRACT We defined the minimal core promoter sequences responsible for efficient and accurate initiation of cucumber mosaic virus (CMV) subgenomic RNA4. The necessary sequence maps to positions −28 to +15 relative to the initiation cytidylate used to initiate RNA synthesis in vivo. Positions −28 to −5 contain a 9-bp stem and a 6-nucleotide purine-rich loop. Considerable changes in the stem and the loop are tolerated for RNA synthesis, including replacement with a different stem-loop. In a template competition assay, the stem-loop and the initiation cytidylate are sufficient to interact with the CMV replicase. Thus, the mechanism of core promoter recognition by the CMV replicase appears to be less specific in comparison to the minimal subgenomic core promoter of the closely related brome mosaic virus.

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Sequence Requirements for Viral RNA Replication and VPg Uridylylation Directed by the Internal cis-Acting Replication Element (cre) of Human Rhinovirus Type 14

Journal of Virology ◽

10.1128/jvi.76.15.7485-7494.2002 ◽

2002 ◽

Vol 76 (15) ◽

pp. 7485-7494 ◽

Cited By ~ 51

Author(s):

Yan Yang ◽

Rene Rijnbrand ◽

Kevin L. McKnight ◽

Eckard Wimmer ◽

Aniko Paul ◽

...

Keyword(s):

Rna Structure ◽

Rna Synthesis ◽

Mutational Analysis ◽

Rna Replication ◽

Human Rhinovirus ◽

Viral Rna ◽

Base Substitution ◽

Stem Loop ◽

Additional Support

ABSTRACT Until recently, the cis-acting signals required for replication of picornaviral RNAs were believed to be restricted to the 5′ and 3′ noncoding regions of the genome. However, an RNA stem-loop in the VP1-coding sequence of human rhinovirus type 14 (HRV-14) is essential for viral minus-strand RNA synthesis (K. L. McKnight and S. M. Lemon, RNA 4:1569-1584, 1998). The nucleotide sequence of the apical loop of this internal cis-acting replication element (cre) was critical for RNA synthesis, while secondary RNA structure, but not primary sequence, was shown to be important within the duplex stem. Similar cres have since been identified in other picornaviral genomes. These RNA segments appear to serve as template for the uridylylation of the genome-linked protein, VPg, providing the VPg-pUpU primer required for viral RNA transcription (A. V. Paul et al., J. Virol. 74:10359-10370, 2000). Here, we show that the minimal functional HRV-14 cre resides within a 33-nucleotide (nt) RNA segment that is predicted to form a simple stem-loop with a 14-nt loop sequence. An extensive mutational analysis involving every possible base substitution at each position within the loop segment defined the sequence that is required within this loop for efficient replication of subgenomic HRV-14 replicon RNAs. These results indicate that three consecutive adenosine residues (nt 2367 to 2369) within the 5′ half of this loop are critically important for cre function and suggest that a common RNNNAARNNNNNNR loop motif exists among the cre sequences of enteroviruses and rhinoviruses. We found a direct, positive correlation between the capacity of mutated cres to support RNA replication and their ability to function as template in an in vitro VPg uridylylation reaction, suggesting that these functions are intimately linked. These data thus define more precisely the sequence and structural requirements of the HRV-14 cre and provide additional support for a model in which the role of the cre in RNA replication is to act as template for VPg uridylylation.

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Role of the 3′ tRNA-Like Structure in Tobacco Mosaic Virus Minus-Strand RNA Synthesis by the Viral RNA-Dependent RNA Polymerase In Vitro

Journal of Virology ◽

10.1128/jvi.74.24.11671-11680.2000 ◽

2000 ◽

Vol 74 (24) ◽

pp. 11671-11680 ◽

Cited By ~ 49

Author(s):

T. A. M. Osman ◽

C. L. Hemenway ◽

K. W. Buck

Keyword(s):

Rna Polymerase ◽

Tobacco Mosaic Virus ◽

Mosaic Virus ◽

Untranslated Region ◽

Rna Synthesis ◽

Central Core ◽

Minus Strand ◽

Stem Loop ◽

Polymerase Binding

ABSTRACT A template-dependent RNA polymerase has been used to determine the sequence elements in the 3′ untranslated region of tobacco mosaic virus RNA that are required for promotion of minus-strand RNA synthesis and binding to the RNA polymerase in vitro. Regions which were important for minus-strand synthesis were domain D1, which is equivalent to a tRNA acceptor arm; domain D2, which is similar to a tRNA anticodon arm; an upstream domain, D3; and a central core, C, which connects domains D1, D2, and D3 and determines their relative orientations. Mutational analysis of the 3′-terminal 4 nucleotides of domain D1 indicated the importance of the 3′-terminal CA sequence for minus-strand synthesis, with the sequence CCCA or GGCA giving the highest transcriptional efficiency. Several double-helical regions, but not their sequences, which are essential for forming pseudoknot and/or stem-loop structures in domains D1, D2, and D3 and the central core, C, were shown to be required for high template efficiency. Also important were a bulge sequence in the D2 stem-loop and, to a lesser extent, a loop sequence in a hairpin structure in domain D1. The sequence of the 3′ untranslated region upstream of domain D3 was not required for minus-strand synthesis. Template-RNA polymerase binding competition experiments showed that the highest-affinity RNA polymerase binding element region lay within a region comprising domain D2 and the central core, C, but domains D1 and D3 also bound to the RNA polymerase with lower affinity.

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A Novel Leu92 Mutant of HIV-1 Reverse Transcriptase with a Selective Deficiency in Strand Transfer Causes a Loss of Viral Replication

Journal of Virology ◽

10.1128/jvi.00809-15 ◽

2015 ◽

Vol 89 (16) ◽

pp. 8119-8129 ◽

Cited By ~ 4

Author(s):

Eytan Herzig ◽

Nickolay Voronin ◽

Nataly Kucherenko ◽

Amnon Hizi

Keyword(s):

Life Cycle ◽

Viral Replication ◽

Reverse Transcriptase ◽

Dna Polymerase ◽

Reverse Transcription ◽

Polymerase Activity ◽

Rnase H ◽

Strand Transfer ◽

Hiv 1

ABSTRACTThe process of reverse transcription (RTN) in retroviruses is essential to the viral life cycle. This key process is catalyzed exclusively by the viral reverse transcriptase (RT) that copies the viral RNA into DNA by its DNA polymerase activity, while concomitantly removing the original RNA template by its RNase H activity. During RTN, the combination between DNA synthesis and RNA hydrolysis leads to strand transfers (or template switches) that are critical for the completion of RTN. The balance between these RT-driven activities was considered to be the sole reason for strand transfers. Nevertheless, we show here that a specific mutation in HIV-1 RT (L92P) that does not affect the DNA polymerase and RNase H activities abolishes strand transfer. There is also a good correlation between this complete loss of the RT's strand transfer to the loss of the DNA clamp activity of the RT, discovered recently by us. This finding indicates a mechanistic linkage between these two functions and that they are both direct and unique functions of the RT (apart from DNA synthesis and RNA degradation). Furthermore, when the RT's L92P mutant was introduced into an infectious HIV-1 clone, it lost viral replication, due to inefficient intracellular strand transfers during RTN, thus supporting thein vitrodata. As far as we know, this is the first report on RT mutants that specifically and directly impair RT-associated strand transfers. Therefore, targeting residue Leu92 may be helpful in selectively blocking this RT activity and consequently HIV-1 infectivity and pathogenesis.IMPORTANCEReverse transcription in retroviruses is essential for the viral life cycle. This multistep process is catalyzed by viral reverse transcriptase, which copies the viral RNA into DNA by its DNA polymerase activity (while concomitantly removing the RNA template by its RNase H activity). The combination and balance between synthesis and hydrolysis lead to strand transfers that are critical for reverse transcription completion. We show here for the first time that a single mutation in HIV-1 reverse transcriptase (L92P) selectively abolishes strand transfers without affecting the enzyme's DNA polymerase and RNase H functions. When this mutation was introduced into an infectious HIV-1 clone, viral replication was lost due to an impaired intracellular strand transfer, thus supporting thein vitrodata. Therefore, finding novel drugs that target HIV-1 reverse transcriptase Leu92 may be beneficial for developing new potent and selective inhibitors of retroviral reverse transcription that will obstruct HIV-1 infectivity.

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Distinct Poly(rC) Binding Protein KH Domain Determinants for Poliovirus Translation Initiation and Viral RNA Replication

Journal of Virology ◽

10.1128/jvi.76.23.12008-12022.2002 ◽

2002 ◽

Vol 76 (23) ◽

pp. 12008-12022 ◽

Cited By ~ 100

Author(s):

Brandon L. Walter ◽

Todd B. Parsley ◽

Ellie Ehrenfeld ◽

Bert L. Semler

Keyword(s):

Translation Initiation ◽

Rna Synthesis ◽

Rna Binding ◽

Binding Protein ◽

Rna Replication ◽

Viral Rna ◽

Host Protein ◽

Loop Structure ◽

Stem Loop ◽

Stem Loop Structure

ABSTRACT The limited coding capacity of picornavirus genomic RNAs necessitates utilization of host cell factors in the completion of an infectious cycle. One host protein that plays a role in both translation initiation and viral RNA synthesis is poly(rC) binding protein 2 (PCBP2). For picornavirus RNAs containing type I internal ribosome entry site (IRES) elements, PCBP2 binds the major stem-loop structure (stem-loop IV) in the IRES and is essential for translation initiation. Additionally, the binding of PCBP2 to the 5′-terminal stem-loop structure (stem-loop I or cloverleaf) in concert with viral protein 3CD is required for initiation of RNA synthesis directed by poliovirus replication complexes. PCBP1, a highly homologous isoform of PCBP2, binds to poliovirus stem-loop I with an affinity similar to that of PCBP2; however, PCBP1 has reduced affinity for stem-loop IV. Using a dicistronic poliovirus RNA, we were able to functionally uncouple translation and RNA replication in PCBP-depleted extracts. Our results demonstrate that PCBP1 rescues RNA replication but is not able to rescue translation initiation. We have also generated mutated versions of PCBP2 containing site-directed lesions in each of the three RNA-binding domains. Specific defects in RNA binding to either stem-loop I and/or stem-loop IV suggest that these domains may have differential functions in translation and RNA replication. These predictions were confirmed in functional assays that allow separation of RNA replication activities from translation. Our data have implications for differential picornavirus template utilization during viral translation and RNA replication and suggest that specific PCBP2 domains may have distinct roles in these activities.

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The Role of Tissue Oxygen Tension in Dengue Virus Replication

Cells ◽

10.3390/cells7120241 ◽

2018 ◽

Vol 7 (12) ◽

pp. 241 ◽

Cited By ~ 8

Author(s):

Efseveia Frakolaki ◽

Panagiota Kaimou ◽

Maria Moraiti ◽

Katerina Kalliampakou ◽

Kalliopi Karampetsou ◽

...

Keyword(s):

Dengue Virus ◽

Oxygen Tension ◽

Atmospheric Oxygen ◽

Rna Replication ◽

Metabolic Reprogramming ◽

Anaerobic Glycolysis ◽

Low Oxygen ◽

Hypoxia Response

Low oxygen tension exerts a profound effect on the replication of several DNA and RNA viruses. In vitro propagation of Dengue virus (DENV) has been conventionally studied under atmospheric oxygen levels despite that in vivo, the tissue microenvironment is hypoxic. Here, we compared the efficiency of DENV replication in liver cells, monocytes, and epithelial cells under hypoxic and normoxic conditions, investigated the ability of DENV to induce a hypoxia response and metabolic reprogramming and determined the underlying molecular mechanism. In DENV-infected cells, hypoxia had no effect on virus entry and RNA translation, but enhanced RNA replication. Overexpression and silencing approaches as well as chemical inhibition and energy substrate exchanging experiments showed that hypoxia-mediated enhancement of DENV replication depends on the activation of the key metabolic regulators hypoxia-inducible factors 1α/2α (HIF-1α/2α) and the serine/threonine kinase AKT. Enhanced RNA replication correlates directly with an increase in anaerobic glycolysis producing elevated ATP levels. Additionally, DENV activates HIF and anaerobic glycolysis markers. Finally, reactive oxygen species were shown to contribute, at least in part through HIF, both to the hypoxia-mediated increase of DENV replication and to virus-induced hypoxic reprogramming. These suggest that DENV manipulates hypoxia response and oxygen-dependent metabolic reprogramming for efficient viral replication.

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