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Simpson J, Kozak CA, Boso G. Evolutionary conservation of an ancient retroviral gagpol gene in Artiodactyla. J Virol 2023; 97:e0053523. [PMID: 37668369 PMCID: PMC10537755 DOI: 10.1128/jvi.00535-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 06/28/2023] [Indexed: 09/06/2023] Open
Abstract
The genomes of mammals contain fingerprints of past infections by ancient retroviruses that invaded the germline of their ancestors. Most of these endogenous retroviruses (ERVs) contain only remnants of the original retrovirus; however, on rare occasions, ERV genes can be co-opted for a beneficial host function. While most studies of co-opted ERVs have focused on envelope genes, including the syncytins that function in placentation, there are examples of co-opted gag genes including one we recently discovered in simian primates. Here, we searched for other intact gag genes in non-primate mammalian lineages. We began by examining the genomes of extant camel species, which represent a basal lineage in the order Artiodactyla. This identified a gagpol gene with a large open reading frame (ORF) (>3,500 bp) in the same orthologous location in Artiodactyla species but that is absent in other mammals. Thus, this ERV was fixed in the common ancestor of all Artiodactyla at least 64 million years ago. The amino acid sequence of this gene, termed ARTgagpol, contains recognizable matrix, capsid, nucleocapsid, and reverse transcriptase domains in ruminants, with an RNase H domain in camels and pigs. Phylogenetic analysis and structural prediction of its reverse transcriptase and RNase H domains groups ARTgagpol with gammaretroviruses. Transcriptomic analysis shows ARTgagpol expression in multiple tissues suggestive of a co-opted host function. These findings identify the oldest and largest ERV-derived gagpol gene with an intact ORF in mammals, an intriguing milestone in the co-evolution of mammals and retroviruses. IMPORTANCE Retroviruses are unique among viruses that infect animals as they integrate their reverse-transcribed double-stranded DNA into host chromosomes. When this happens in a germline cell, such as sperm, egg, or their precursors, the integrated retroviral copies can be passed on to the next generation as endogenous retroviruses (ERVs). On rare occasions, the genes of these ERVs can be domesticated by the host. In this study we used computational similarity searches to identify an ancient ERV with an intact viral gagpol gene in the genomes of camels that is also found in the same genomic location in other even-toed ungulates suggesting that it is at least 64 million years old. Broad tissue expression and predicted preservation of the reverse transcriptase fold of this protein suggest that it may be domesticated for a host function. This is the oldest known intact gagpol gene of an ancient retrovirus in mammals.
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Affiliation(s)
- J'Zaria Simpson
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
| | - Christine A. Kozak
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
| | - Guney Boso
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA
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2
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Yan S, Wu G. Potential 3-chymotrypsin-like cysteine protease cleavage sites in the coronavirus polyproteins pp1a and pp1ab and their possible relevance to COVID-19 vaccine and drug development. FASEB J 2021; 35:e21573. [PMID: 33913206 PMCID: PMC8206714 DOI: 10.1096/fj.202100280rr] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 03/04/2021] [Accepted: 03/19/2021] [Indexed: 02/06/2023]
Abstract
Coronavirus (CoV) 3-chymotrypsin (C)-like cysteine protease (3CLpro ) is a target for anti-CoV drug development and drug repurposing because along with papain-like protease, it cleaves CoV-encoded polyproteins (pp1a and pp1ab) into nonstructural proteins (nsps) for viral replication. However, the cleavage sites of 3CLpro and their relevant nsps remain unclear, which is the subject of this perspective. Here, we address the subject from three standpoints. First, we explore the inconsistency in the cleavage sites and relevant nsps across CoVs, and investigate the function of nsp11. Second, we consider the nsp16 mRNA overlapping of the spike protein mRNA, and analyze the effect of this overlapping on mRNA vaccines. Finally, we study nsp12, whose existence depends on ribosomal frameshifting, and investigate whether 3CLpro requires a large number of inhibitors to achieve full inhibition. This perspective helps us to clarify viral replication and is useful for developing anti-CoV drugs with 3CLpro as a target in the current coronavirus disease 2019 (COVID-19) pandemic.
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Affiliation(s)
- Shaomin Yan
- National Engineering Research Center for Non‐Food Biorefinery, State Key Laboratory of Non‐Food Biomass and Enzyme Technology, Guangxi Biomass Engineering Technology Research Center, Guangxi Key Laboratory of BiorefineryGuangxi Academy of SciencesNanningChina
| | - Guang Wu
- National Engineering Research Center for Non‐Food Biorefinery, State Key Laboratory of Non‐Food Biomass and Enzyme Technology, Guangxi Biomass Engineering Technology Research Center, Guangxi Key Laboratory of BiorefineryGuangxi Academy of SciencesNanningChina
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3
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Mikl M, Pilpel Y, Segal E. High-throughput interrogation of programmed ribosomal frameshifting in human cells. Nat Commun 2020; 11:3061. [PMID: 32546731 PMCID: PMC7297798 DOI: 10.1038/s41467-020-16961-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/28/2020] [Indexed: 12/30/2022] Open
Abstract
Programmed ribosomal frameshifting (PRF) is the controlled slippage of the translating ribosome to an alternative frame. This process is widely employed by human viruses such as HIV and SARS coronavirus and is critical for their replication. Here, we developed a high-throughput approach to assess the frameshifting potential of a sequence. We designed and tested >12,000 sequences based on 15 viral and human PRF events, allowing us to systematically dissect the rules governing ribosomal frameshifting and discover novel regulatory inputs based on amino acid properties and tRNA availability. We assessed the natural variation in HIV gag-pol frameshifting rates by testing >500 clinical isolates and identified subtype-specific differences and associations between viral load in patients and the optimality of PRF rates. We devised computational models that accurately predict frameshifting potential and frameshifting rates, including subtle differences between HIV isolates. This approach can contribute to the development of antiviral agents targeting PRF.
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Affiliation(s)
- Martin Mikl
- Department of Computer Science and Applied Mathematics, Rehovot, 7610001, Israel.
- Department of Molecular Cell Biology and Weizmann Institute of Science, Rehovot, 7610001, Israel.
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
- Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Mount Carmel, Haifa, 31905, Israel.
| | - Yitzhak Pilpel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Eran Segal
- Department of Computer Science and Applied Mathematics, Rehovot, 7610001, Israel.
- Department of Molecular Cell Biology and Weizmann Institute of Science, Rehovot, 7610001, Israel.
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Thulson E, Hartwick EW, Cooper-Sansone A, Williams MAC, Soliman ME, Robinson LK, Kieft JS, Mouzakis KD. An RNA pseudoknot stimulates HTLV-1 pro-pol programmed -1 ribosomal frameshifting. RNA (NEW YORK, N.Y.) 2020; 26:512-528. [PMID: 31980578 PMCID: PMC7075266 DOI: 10.1261/rna.070490.119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
Programmed -1 ribosomal frameshifts (-1 PRFs) are commonly used by viruses to regulate their enzymatic and structural protein levels. Human T-cell leukemia virus type 1 (HTLV-1) is a carcinogenic retrovirus that uses two independent -1 PRFs to express viral enzymes critical to establishing new HTLV-1 infections. How the cis-acting RNA elements in this viral transcript function to induce frameshifting is unknown. The objective of this work was to conclusively define the 3' boundary of and the RNA elements within the HTLV-1 pro-pol frameshift site. We hypothesized that the frameshift site structure was a pseudoknot and that its 3' boundary would be defined by the pseudoknot's 3' end. To test these hypotheses, the in vitro frameshift efficiencies of three HTLV-1 pro-pol frameshift sites with different 3' boundaries were quantified. The results indicated that nucleotides included in the longest construct were essential to highly efficient frameshift stimulation. Interestingly, only this construct could form the putative frameshift site pseudoknot. Next, the secondary structure of this frameshift site was determined. The dominant structure was an H-type pseudoknot which, together with the slippery sequence, stimulated frameshifting to 19.4(±0.3)%. The pseudoknot's critical role in frameshift stimulation was directly revealed by examining the impact of structural changes on HTLV-1 pro-pol -1 PRF. As predicted, mutations that occluded pseudoknot formation drastically reduced the frameshift efficiency. These results are significant because they demonstrate that a pseudoknot is important to HTLV-1 pro-pol -1 PRF and define the frameshift site's 3' boundary.
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Affiliation(s)
- Eliza Thulson
- Department of Chemistry and Biochemistry, Fort Lewis College, Durango, Colorado 81301, USA
| | - Erik W Hartwick
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA
- RNA Bioscience Initiative, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA
| | - Andrew Cooper-Sansone
- Department of Chemistry and Biochemistry, Fort Lewis College, Durango, Colorado 81301, USA
| | - Marcus A C Williams
- Department of Chemistry and Biochemistry, Fort Lewis College, Durango, Colorado 81301, USA
| | - Mary E Soliman
- Department of Chemistry and Biochemistry, Loyola Marymount University, Los Angeles, California 90045, USA
| | - Leila K Robinson
- Department of Chemistry and Biochemistry, Loyola Marymount University, Los Angeles, California 90045, USA
| | - Jeffrey S Kieft
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA
- RNA Bioscience Initiative, University of Colorado Denver School of Medicine, Aurora, Colorado 80045, USA
| | - Kathryn D Mouzakis
- Department of Chemistry and Biochemistry, Loyola Marymount University, Los Angeles, California 90045, USA
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Atkins JF, Loughran G, Bhatt PR, Firth AE, Baranov PV. Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use. Nucleic Acids Res 2016; 44:7007-78. [PMID: 27436286 PMCID: PMC5009743 DOI: 10.1093/nar/gkw530] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/26/2016] [Indexed: 12/15/2022] Open
Abstract
Genetic decoding is not ‘frozen’ as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational ‘correction’ of problem or ‘savior’ indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5′ or 3′ of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3′ from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.
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Affiliation(s)
- John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland School of Microbiology, University College Cork, Cork, Ireland Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pramod R Bhatt
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Andrew E Firth
- Division of Virology, Department of Pathology, University of Cambridge, Hills Road, Cambridge CB2 0QQ, UK
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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6
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Green L, Goff SP. Translational readthrough-promoting drugs enhance pseudoknot-mediated suppression of the stop codon at the Moloney murine leukemia virus gag–pol junction. J Gen Virol 2016; 96:3411-3421. [PMID: 26382736 DOI: 10.1099/jgv.0.000284] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Translational readthrough-promoting drugs enhance the incorporation of amino acids at stop codons and can thus bypass premature termination during protein synthesis. The polymerase (Pol) proteins of Moloney murine leukemia virus (MoMLV) are synthesized as a large Gag–Pol fusion protein, formed by the readthrough of a stop codon at the end of the gag ORF. The downstream pol ORF lacks its own start codon, and Pol protein synthesis is wholly dependent on translation of the upstream gag gene and the readthrough event for expression. Here, we explored the effects of readthrough-promoting drugs – aminoglycoside antibiotics and the small molecule ataluren – on the efficiency of readthrough of the stop codon in the context of the MoMLV genome. We showed that these compounds increased readthrough of the stop codon at the MoMLV gag–pol junction in vivo above the already high basal level and that the resulting elevated gag–pol readthrough had deleterious effects on virus replication. We also showed that readthrough efficiency could be driven to even higher levels in vitro, and that the combination of the small molecules and the RNA structure at the MoMLV stop codon could achieve extremely high readthrough efficiencies.
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Affiliation(s)
- Lisa Green
- Department of Biological Sciences, Columbia University Medical Center, New York, NY 10032, USA
| | - Stephen P Goff
- Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, New York, NY 10032, USA.,Howard Hughes Medical Institute, Columbia University Medical Center, New York, NY 10032, USA.,Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY 10032, USA
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7
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Maldonado JO, Cao S, Zhang W, Mansky LM. Distinct Morphology of Human T-Cell Leukemia Virus Type 1-Like Particles. Viruses 2016; 8:v8050132. [PMID: 27187442 PMCID: PMC4885087 DOI: 10.3390/v8050132] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/15/2016] [Accepted: 04/21/2016] [Indexed: 02/06/2023] Open
Abstract
The Gag polyprotein is the main retroviral structural protein and is essential for the assembly and release of virus particles. In this study, we have analyzed the morphology and Gag stoichiometry of human T-cell leukemia virus type 1 (HTLV-1)-like particles and authentic, mature HTLV-1 particles by using cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission electron microscopy (STEM). HTLV-1-like particles mimicked the morphology of immature authentic HTLV-1 virions. Importantly, we have observed for the first time that the morphology of these virus-like particles (VLPs) has the unique local feature of a flat Gag lattice that does not follow the curvature of the viral membrane, resulting in an enlarged distance between the Gag lattice and the viral membrane. Other morphological features that have been previously observed with other retroviruses include: (1) a Gag lattice with multiple discontinuities; (2) membrane regions associated with the Gag lattice that exhibited a string of bead-like densities at the inner leaflet; and (3) an arrangement of the Gag lattice resembling a railroad track. Measurement of the average size and mass of VLPs and authentic HTLV-1 particles suggested a consistent range of size and Gag copy numbers in these two groups of particles. The unique local flat Gag lattice morphological feature observed suggests that HTLV-1 Gag could be arranged in a lattice structure that is distinct from that of other retroviruses characterized to date.
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Affiliation(s)
- José O Maldonado
- Institute for Molecular Virology & DDS-PhD Dual Degree Program, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
| | - Sheng Cao
- Institute for Molecular Virology, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
| | - Wei Zhang
- Institute for Molecular Virology & Characterization Facility, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
| | - Louis M Mansky
- Institute for Molecular Virology, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
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8
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Transactivation of programmed ribosomal frameshifting by a viral protein. Proc Natl Acad Sci U S A 2014; 111:E2172-81. [PMID: 24825891 DOI: 10.1073/pnas.1321930111] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Programmed -1 ribosomal frameshifting (-1 PRF) is a widely used translational mechanism facilitating the expression of two polypeptides from a single mRNA. Commonly, the ribosome interacts with an mRNA secondary structure that promotes -1 frameshifting on a homopolymeric slippery sequence. Recently, we described an unusual -2 frameshifting (-2 PRF) signal directing efficient expression of a transframe protein [nonstructural protein 2TF (nsp2TF)] of porcine reproductive and respiratory syndrome virus (PRRSV) from an alternative reading frame overlapping the viral replicase gene. Unusually, this arterivirus PRF signal lacks an obvious stimulatory RNA secondary structure, but as confirmed here, can also direct the occurrence of -1 PRF, yielding a third, truncated nsp2 variant named "nsp2N." Remarkably, we now show that both -2 and -1 PRF are transactivated by a protein factor, specifically a PRRSV replicase subunit (nsp1β). Embedded in nsp1β's papain-like autoproteinase domain, we identified a highly conserved, putative RNA-binding motif that is critical for PRF transactivation. The minimal RNA sequence required for PRF was mapped within a 34-nt region that includes the slippery sequence and a downstream conserved CCCANCUCC motif. Interaction of nsp1β with the PRF signal was demonstrated in pull-down assays. These studies demonstrate for the first time, to our knowledge, that a protein can function as a transactivator of ribosomal frameshifting. The newly identified frameshifting determinants provide potential antiviral targets for arterivirus disease control and prevention. Moreover, protein-induced transactivation of frameshifting may be a widely used mechanism, potentially including previously undiscovered viral strategies to regulate viral gene expression and/or modulate host cell translation upon infection.
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9
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Lin Z, Gilbert RJC, Brierley I. Spacer-length dependence of programmed -1 or -2 ribosomal frameshifting on a U6A heptamer supports a role for messenger RNA (mRNA) tension in frameshifting. Nucleic Acids Res 2012; 40:8674-89. [PMID: 22743270 PMCID: PMC3458567 DOI: 10.1093/nar/gks629] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Programmed -1 ribosomal frameshifting is employed in the expression of a number of viral and cellular genes. In this process, the ribosome slips backwards by a single nucleotide and continues translation of an overlapping reading frame, generating a fusion protein. Frameshifting signals comprise a heptanucleotide slippery sequence, where the ribosome changes frame, and a stimulatory RNA structure, a stem-loop or RNA pseudoknot. Antisense oligonucleotides annealed appropriately 3' of a slippery sequence have also shown activity in frameshifting, at least in vitro. Here we examined frameshifting at the U6A slippery sequence of the HIV gag/pol signal and found high levels of both -1 and -2 frameshifting with stem-loop, pseudoknot or antisense oligonucleotide stimulators. By examining -1 and -2 frameshifting outcomes on mRNAs with varying slippery sequence-stimulatory RNA spacing distances, we found that -2 frameshifting was optimal at a spacer length 1-2 nucleotides shorter than that optimal for -1 frameshifting with all stimulatory RNAs tested. We propose that the shorter spacer increases the tension on the mRNA such that when the tRNA detaches, it more readily enters the -2 frame on the U6A heptamer. We propose that mRNA tension is central to frameshifting, whether promoted by stem-loop, pseudoknot or antisense oligonucleotide stimulator.
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Affiliation(s)
- Zhaoru Lin
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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Liao PY, Choi YS, Dinman JD, Lee KH. The many paths to frameshifting: kinetic modelling and analysis of the effects of different elongation steps on programmed -1 ribosomal frameshifting. Nucleic Acids Res 2010; 39:300-12. [PMID: 20823091 PMCID: PMC3017607 DOI: 10.1093/nar/gkq761] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Several important viruses including the human immunodeficiency virus type 1 (HIV-1) and the SARS-associated Coronavirus (SARS-CoV) employ programmed −1 ribosomal frameshifting (PRF) for their protein expression. Here, a kinetic framework is developed to describe −1 PRF. The model reveals three kinetic pathways to −1 PRF that yield two possible frameshift products: those incorporating zero frame encoded A-site tRNAs in the recoding site, and products incorporating −1 frame encoded A-site tRNAs. Using known kinetic rate constants, the individual contributions of different steps of the translation elongation cycle to −1 PRF and the ratio between two types of frameshift products were evaluated. A dual fluorescence reporter was employed in Escherichia coli to empirically test the model. Additionally, the study applied a novel mass spectrometry approach to quantify the ratios of the two frameshift products. A more detailed understanding of the mechanisms underlying −1 PRF may provide insight into developing antiviral therapeutics.
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Affiliation(s)
- Pei-Yu Liao
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
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Abstract
Regulation of protein synthesis by viruses occurs at all levels of translation. Even prior to protein synthesis itself, the accessibility of the various open reading frames contained in the viral genome is precisely controlled. Eukaryotic viruses resort to a vast array of strategies to divert the translation machinery in their favor, in particular, at initiation of translation. These strategies are not only designed to circumvent strategies common to cell protein synthesis in eukaryotes, but as revealed more recently, they also aim at modifying or damaging cell factors, the virus having the capacity to multiply in the absence of these factors. In addition to unraveling mechanisms that may constitute new targets in view of controlling virus diseases, viruses constitute incomparably useful tools to gain in-depth knowledge on a multitude of cell pathways.
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Lepoutre V, Jain P, Quann K, Wigdahl B, Khan ZK. Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease. Front Biosci (Landmark Ed) 2009; 14:1152-68. [PMID: 19273122 DOI: 10.2741/3300] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.
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Affiliation(s)
- Veronique Lepoutre
- Department of Microbiology and Immunology, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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Ohsugi T, Koito A. Current topics in prevention of human T-cell leukemia virus type i infection: NF-kappa B inhibitors and APOBEC3. Int Rev Immunol 2008; 27:225-53. [PMID: 18574738 DOI: 10.1080/08830180801939272] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Human T-cell leukemia virus type I (HTLV-I) is the first human retrovirus and causes adult T-cell leukemia/lymphoma (ATL). Constitutive activation of nuclear factor-kappa B (NF-kappa B) in the leukemic cells is essential for their growth and survival. Thus, NF-kappa B inhibitors have been attracting attention as a potential strategy to treat ATL. Recently, the field of retrovirus research has been stimulated by the discovery of an innate host defense factor, APOBEC3, against the retroviruses. HTLV-I is relatively resistant to the antiviral effects of APOBEC3. To clarify the resistance of HTLV-I against APOBEC3 might contribute to the design of effective therapeutic approaches.
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Affiliation(s)
- Takeo Ohsugi
- Division of Microbiology and Genetics, Center for Animal Resources and Development, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan.
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14
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Mitchell MS, Tözsér J, Princler G, Lloyd PA, Auth A, Derse D. Synthesis, processing, and composition of the virion-associated HTLV-1 reverse transcriptase. J Biol Chem 2005; 281:3964-71. [PMID: 16368688 DOI: 10.1074/jbc.m507660200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is not known whether the low infectivity and low virion-associated polymerase activity of human T-cell lymphotropic virus type-1 (HTLV-1) are due to the quantity or quality of the reverse transcriptase (RT), because the protein has not yet been fully characterized. We have developed anti-RT antibodies and constructed HTLV-1 expression plasmids that express truncated or hemagglutinin-tagged Pol polyproteins to examine the maturation and composition of HTLV-1 RT. We detected virion-associated proteins corresponding to RT-integrase (IN) (pr98) and RT (p62) as well as smaller proteins containing the polymerase (p49) or RNase H domains. We have identified the amino acid sequences in the Pol polyprotein that are cleaved by HTLV-1 protease to yield RT and IN. We have also identified the cleavage sites within RT that give rise to the p49 polymerase fragment. Immunoprecipitation of an epitope-tagged p62 subunit coprecipitated p49, indicating that the HTLV-1 RT complex can exist as a p62/p49 heterodimer analogous to the RT of HIV-1 (p66/p51).
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15
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Manktelow E, Shigemoto K, Brierley I. Characterization of the frameshift signal of Edr, a mammalian example of programmed -1 ribosomal frameshifting. Nucleic Acids Res 2005; 33:1553-63. [PMID: 15767280 PMCID: PMC1065257 DOI: 10.1093/nar/gki299] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The ribosomal frameshifting signal of the mouse embryonal carcinoma differentiation regulated (Edr) gene represents the sole documented example of programmed −1 frameshifting in mammalian cellular genes [Shigemoto,K., Brennan,J., Walls,E,. Watson,C.J., Stott,D., Rigby,P.W. and Reith,A.D. (2001), Nucleic Acids Res., 29, 4079–4088]. Here, we have employed site-directed mutagenesis and RNA structure probing to characterize the Edr signal. We began by confirming the functionality and magnitude of the signal and the role of a GGGAAAC motif as the slippery sequence. Subsequently, we derived a model of the Edr stimulatory RNA and assessed its similarity to those stimulatory RNAs found at viral frameshift sites. We found that the structure is an RNA pseudoknot possessing features typical of retroviral frameshifter pseudoknots. From these experiments, we conclude that the Edr signal and by inference, the human orthologue PEG10, do not represent a novel ‘cellular class’ of programmed −1 ribosomal frameshift signal, but rather are similar to viral examples, albeit with some interesting features. The similarity to viral frameshift signals may complicate the design of antiviral therapies that target the frameshift process.
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Affiliation(s)
| | - Kazuhiro Shigemoto
- Department of Environmental Health and Social Medicine, Ehime University School of MedicineShitsukawa, Toon, Ehime 791-0295 Japan
| | - Ian Brierley
- To whom correspondence should be addressed. Tel: +44 1223 336914; Fax: +44 1223 336926;
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16
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Peptide nucleic acids as epigenetic inhibitors of HIV-1. Int J Pept Res Ther 2005. [DOI: 10.1007/s10989-005-4925-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Gao F, Ou HY, Chen LL, Zheng WX, Zhang CT. Prediction of proteinase cleavage sites in polyproteins of coronaviruses and its applications in analyzing SARS-CoV genomes. FEBS Lett 2003; 553:451-6. [PMID: 14572668 PMCID: PMC7232748 DOI: 10.1016/s0014-5793(03)01091-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Revised: 09/19/2003] [Accepted: 09/22/2003] [Indexed: 01/17/2023]
Abstract
Recently, we have developed a coronavirus-specific gene-finding system, ZCURVE_CoV 1.0. In this paper, the system is further improved by taking the prediction of cleavage sites of viral proteinases in polyproteins into account. The cleavage sites of the 3C-like proteinase and papain-like proteinase are highly conserved. Based on the method of traditional positional weight matrix trained by the peptides around cleavage sites, the present method also sufficiently considers the length conservation of non-structural proteins cleaved by the 3C-like proteinase and papain-like proteinase to reduce the false positive prediction rate. The improved system, ZCURVE_CoV 2.0, has been run for each of the 24 completely sequenced coronavirus genomes in GenBank. Consequently, all the non-structural proteins in the 24 genomes are accurately predicted. Compared with known annotations, the performance of the present method is satisfactory. The software ZCURVE_CoV 2.0 is freely available at http://tubic.tju.edu.cn/sars/.
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Affiliation(s)
- Feng Gao
- Department of Physics, Tianjin University, Tianjin 300072, PR China
| | - Hong-Yu Ou
- Department of Physics, Tianjin University, Tianjin 300072, PR China
| | - Ling-Ling Chen
- Department of Physics, Tianjin University, Tianjin 300072, PR China
- Laboratory for Computational Biology, Shandong Provincial Research Center for Bioinformatic Engineering and Technique, Shandong University of Technology, Zibo 255049, PR China
| | - Wen-Xin Zheng
- Department of Physics, Tianjin University, Tianjin 300072, PR China
| | - Chun-Ting Zhang
- Department of Physics, Tianjin University, Tianjin 300072, PR China
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18
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Brierley I, Pennell S. Structure and function of the stimulatory RNAs involved in programmed eukaryotic-1 ribosomal frameshifting. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 66:233-48. [PMID: 12762025 DOI: 10.1101/sqb.2001.66.233] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- I Brierley
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
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19
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Peptide nucleic acids as epigenetic inhibitors of HIV-1. Int J Pept Res Ther 2003. [DOI: 10.1007/s10989-004-4925-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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20
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Shuker SB, Mariani VL, Herger BE, Dennison KJ. Understanding HTLV-I protease. CHEMISTRY & BIOLOGY 2003; 10:373-80. [PMID: 12770819 DOI: 10.1016/s1074-5521(03)00104-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Suzanne Beckham Shuker
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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21
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22
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Abstract
Human T-cell leukemia virus type 1 (HTLV-1) is a type C human retrovirus and is the causative agent of adult T-cell leukemia and other diseases. The enzymatic and structural proteins of HTLV-I are synthesized as part of a Gag-Pro-Pol precursor polyprotein, and the mature proteins are released by proteolytic processing catalyzed by HTLV-I protease. The locations of most of the proteolytic cleavage sites are known, however, the site that creates the N-terminus of HTLV-1 integrase has not been previously identified. A 15 residue peptide corresponding to junction of the C-terminus of RNaseH and N-terminus of integrase (DALLITPVLQLSPAF-OH) was incubated with HTLV-1 protease. Analysis of the cleavage products by LC-MS revealed fragments Ac-DALLITPVLQL-OH and H(2)N-SPAF-OH were produced, indicating cleavage between the leucine and serine. This is the first physical identification of the N-terminal amino acid sequence of the integrase of HTLV-1.
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Affiliation(s)
- Victoria L Mariani
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
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23
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Namy O, Duchateau-Nguyen G, Rousset JP. Translational readthrough of the PDE2 stop codon modulates cAMP levels in Saccharomyces cerevisiae. Mol Microbiol 2002; 43:641-52. [PMID: 11929521 DOI: 10.1046/j.1365-2958.2002.02770.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The efficiency of translation termination in yeast can vary several 100-fold, depending on the context around the stop codon. We performed a computer analysis designed to identify yeast open reading frames (ORFs) containing a readthrough motif surrounding the termination codon. Eight ORFs were found to display inefficient stop codon recognition, one of which, PDE2, encodes the high-affinity cAMP phosphodiesterase. We demonstrate that Pde2p stability is very impaired by the readthrough-dependent extension of the protein. A 20-fold increase in readthrough of PDE2 was observed in a [PSI+] as compared with a [psi-] strain. Consistent with this observation, an important increase in cAMP concentration was observed in suppressor backgrounds. These results provide a molecular explanation for at least some of the secondary phenotypes associated with suppressor backgrounds.
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Affiliation(s)
- Olivier Namy
- Laboratoire de génétique moléculaire de la traduction, Institut de Génétique et Microbiologie, Université Paris-Sud, Orsay, France
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24
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Meertens L, Mahieux R, Mauclère P, Lewis J, Gessain A. Complete sequence of a novel highly divergent simian T-cell lymphotropic virus from wild-caught red-capped mangabeys (Cercocebus torquatus) from Cameroon: a new primate T-lymphotropic virus type 3 subtype. J Virol 2002; 76:259-68. [PMID: 11739691 PMCID: PMC135714 DOI: 10.1128/jvi.76.1.259-268.2002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Among 65 samples obtained from a primate rescue center located in Cameroon, two female adult red-capped mangabeys (Cercocebus torquatus) (CTO-602 and CTO-604), of wild-caught origin, had a peculiar human T-cell lymphotropic virus type 2 (HTLV-2)-like Western blot seroreactivity (p24, RGD21, +/-K55). Analyses of the simian T-cell lymphotropic virus type 3 (STLV-3)/CTO-604 complete proviral sequence (8,919 bp) indicated that this novel strain was highly divergent from HTLV-1 (60% nucleotide similarity), HTLV-2 (62%), or STLV-2 (62%) prototypes. It was, however, related to STLV-3/PH-969 (87%), a divergent STLV strain previously isolated from an Eritrean baboon. The STLV-3/CTO-604 sequence possesses the major open reading frames corresponding to the structural, enzymatic, and regulatory proteins. However, its long terminal repeat is shorter, with only two 21-bp repeats. Furthermore, as demonstrated by reverse transcriptase PCR, this new STLV exhibits significant differences from STLV-3/PH-969 at the mRNA splice junction position level. In all phylogenetic analyses, STLV-3/CTO-604 and STLV-3/PH-969 clustered in a highly supported single clade, indicating an evolutionary lineage independent from primate T-lymphotropic virus type 1 (PTLV-1) and PTLV-2. Nevertheless, the nucleotide divergence between STLV-3/PH-969 and STLV-3/CTO-604 is equivalent to or higher than the divergence observed between the different HTLV-1 or HTLV-2 subtypes. Thus, the STLV-3/CTO-604 strain can be considered the prototype of a second subtype in the PTLV-3 type. The presence of two related viruses in evolutionarily distantly related African monkeys species, living in two opposite ecosystems (rain forest versus desert), reinforces the possible African origin of PTLV and opens new avenues regarding the search for a possible human counterpart of these viruses in individuals exhibiting such HTLV-2-like seroreactivities.
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Affiliation(s)
- Laurent Meertens
- Unité d'Epidémiologie et Physiopathologie des Virus Oncogènes, Département du SIDA et des Rétrovirus, Institut Pasteur, 75724 Paris Cedex 15, France
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25
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Le Blanc I, Grange MP, Delamarre L, Rosenberg AR, Blot V, Pique C, Dokhélar MC. HTLV-1 structural proteins. Virus Res 2001; 78:5-16. [PMID: 11520576 DOI: 10.1016/s0168-1702(01)00278-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
HTLV-1 structural proteins do not appear to ensure virus transmission as efficiently as most other retrovirus structural proteins do, whereas all other retroviruses can be transmitted via either free virions or cell-to-cell contacts, infection by HTLV-1 by free virions is very inefficient, and effective infection requires the presence of HTLV-1 infected cells. This characteristic feature of HTLV-1 provides a unique tool which can be used to analyse retrovirus cellular transmission in the absence of simultaneous cell-free infection. Here we summarise what is known about HTLV-1 structural proteins and identify the questions about these proteins which remain to be answered.
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Affiliation(s)
- I Le Blanc
- INSERM U332, Institut Cochin de Génétique Moléculaire, 22 Rue Méchain, 75014, Paris, France
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26
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Agbuya PG, Sherman NE, Moen LK. Proteolytic processing of the human T-cell lymphotropic virus 1 reverse transcriptase: identification of the N-terminal cleavage site by mass spectrometry. Arch Biochem Biophys 2001; 392:93-102. [PMID: 11469799 DOI: 10.1006/abbi.2001.2432] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human T-cell lymphotropic virus 1 (HTLV-1) is a type C human retrovirus, which is the causative agent of Adult T-cell Leukemia and other diseases. The reverse transcriptase of HTLV-1 (E.C. 2.7.7.49) is synthesized as part of a Gag--Pro--Pol precursor protein, and the mature Gag, Pro, and Pol proteins, including the reverse transcriptase, are created by proteolytic processing catalyzed by the viral protease. The location of the proteolytic cleavage site, which creates the N-terminus of mature HTLV-1 reverse transcriptase, has not been previously identified. By using sequence comparisons of several retroviral polymerases, as well as information about the location of the ribosomal frameshift, we tentatively identified this N-terminal processing site. PCR amplification was used to construct a clone, which spans a region of the pro--pol junction of HTLV-1, to produce a recombinant Pro--Pol protein spanning the locations of those cleavage sites proposed by others as well as the one identified by our sequence alignment. Cleavage of the recombinant Pro--Pol protein by HTLV-1 protease generated a 5.5-kDa fragment. Analysis of this fragment by capillary LC-MS and MS/MS revealed the N-terminal cleavage site to be between Leu(147)--Pro(148) of the pro ORF. This is the first physical identification of the authentic amino acid sequence of the reverse transcriptase of HTLV-1. The data reported here provides a basis for further investigation of the function and structural aspects of protein-nucleic interaction.
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Affiliation(s)
- P G Agbuya
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, USA
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27
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Anantharaman V, Moen LK. Effects of Nucleoside Analogs on Native and Site-Directed Mutants of HTLV Type 1 Reverse Transcriptase. Bioorg Chem 2000; 28:293-305. [PMID: 11133148 DOI: 10.1006/bioo.2000.1181] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A bacterial assay was developed for testing HTLV-1 reverse transcriptase sensitivity to common nucleoside analog inhibitors in an Escherichia coli strain characterized by a temperature sensitive PolI/RecA deletion phenotype. This genetic complementation assay exploits the ability of HTLV-1 reverse transcriptase to functionally replace these missing activities at nonpermissive temperatures. The four inhibitors tested, dideoxyinosine, dideoxyadenosine, deoxythymidine, and didehydrodeoxythymidine are well-known inhibitors of HIV reverse transcriptase. All except dideoxyadenosine showed a strong activity against HTLV-1 reverse transcriptase with IC(50); in the nanomolar range. Sequence alignments were used to identify amino acid residues in HTLV-1 reverse transcriptase, which correspond to those identified as important for drug-resistance in HIV reverse transcriptase. Mutations of some of these HTLV-1 residues altered the IC(50) for the inhibitors as expected, which suggests that these amino acids have a function in HTLV-1 reverse transcriptase similar to that of their homologs in HIV reverse transcriptase. Copyright 2000 Academic Press.
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Affiliation(s)
- V Anantharaman
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, 23529-0126
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28
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Sei S, Yang QE, O'Neill D, Yoshimura K, Nagashima K, Mitsuya H. Identification of a key target sequence to block human immunodeficiency virus type 1 replication within the gag-pol transframe domain. J Virol 2000; 74:4621-33. [PMID: 10775598 PMCID: PMC111982 DOI: 10.1128/jvi.74.10.4621-4633.2000] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the full sequence of the human immunodeficiency virus type 1 (HIV-1) genome has been known for more than a decade, effective genetic antivirals have yet to be developed. Here we show that, of 22 regions examined, one highly conserved sequence (ACTCTTTGGCAACGA) near the 3' end of the HIV-1 gag-pol transframe region, encoding viral protease residues 4 to 8 and a C-terminal Vpr-binding motif of p6(Gag) protein in two different reading frames, can be successfully targeted by an antisense peptide nucleic acid oligomer named PNA(PR2). A disrupted translation of gag-pol mRNA induced at the PNA(PR2)-annealing site resulted in a decreased synthesis of Pr160(Gag-Pol) polyprotein, hence the viral protease, a predominant expression of Pr55(Gag) devoid of a fully functional p6(Gag) protein, and the excessive intracellular cleavage of Gag precursor proteins, hindering the processes of virion assembly. Treatment with PNA(PR2) abolished virion production by up to 99% in chronically HIV-1-infected H9 cells and in peripheral blood mononuclear cells infected with clinical HIV-1 isolates with the multidrug-resistant phenotype. This particular segment of the gag-pol transframe gene appears to offer a distinctive advantage over other regions in invading viral structural genes and restraining HIV-1 replication in infected cells and may potentially be exploited as a novel antiviral genetic target.
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Affiliation(s)
- S Sei
- HIV Clinical Interface Laboratory, SAIC-Frederick, NCI-Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA.
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29
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Ziebuhr J, Snijder EJ, Gorbalenya AE. Virus-encoded proteinases and proteolytic processing in the Nidovirales. J Gen Virol 2000; 81:853-79. [PMID: 10725411 DOI: 10.1099/0022-1317-81-4-853] [Citation(s) in RCA: 751] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- J Ziebuhr
- Institute of Virology and Immunology, University of Würzburg, Versbacher Str. 7, 97078 Würzburg, Germany.
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30
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Carlson BA, Kwon SY, Lee BJ, Hatfield D. Yeast asparagine (Asn) tRNA without Q base promotes eukaryotic frameshifting more efficiently than mammalian Asn tRNAs with or without Q base. Mol Cells 2000; 10:113-8. [PMID: 10774757 DOI: 10.1007/s10059-000-0113-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
In this study, we compare the efficiency of Asn tRNA from mammalian sources with and without the highly modified queuosine (Q) base in the wobble position of its anticodon and Asn tRNA from yeast, which naturally lacks Q base, to promote frameshifting. Interestingly, no differences in the ability of the two mammalian Asn tRNAs to promote frameshifting were observed, while yeast tRNA(ASn)(-Q) promoted frameshifting more efficiently than its mammalian counterparts in both rabbit reticulocyte lysates and wheat germ extracts. The shiftability of yeast Asn tRNA is therefore not due, or at least not completely, to the lack of Q base and most likely the shiftiness resides in structural differences elsewhere in the molecule. However, we cannot absolutely rule out a role of Q base in frameshifting as wheat germ extracts and a lysate depleted of most of its tRNA and supplemented with calf liver tRNA contain both Asn tRNA with or without Q base.
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Affiliation(s)
- B A Carlson
- Section on the Molecular Biology of Selenium, Laboratory of Basic Research and Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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31
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Lopinski JD, Dinman JD, Bruenn JA. Kinetics of ribosomal pausing during programmed -1 translational frameshifting. Mol Cell Biol 2000; 20:1095-103. [PMID: 10648594 PMCID: PMC85227 DOI: 10.1128/mcb.20.4.1095-1103.2000] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In the Saccharomyces cerevisiae double-stranded RNA virus, programmed -1 ribosomal frameshifting is responsible for translation of the second open reading frame of the essential viral RNA. A typical slippery site and downstream pseudoknot are necessary for this frameshifting event, and previous work has demonstrated that ribosomes pause over the slippery site. The translational intermediate associated with a ribosome paused at this position is detected, and, using in vitro translation and quantitative heelprinting, the rates of synthesis, the ribosomal pause time, the proportion of ribosomes paused at the slippery site, and the fraction of paused ribosomes that frameshift are estimated. About 10% of ribosomes pause at the slippery site in vitro, and some 60% of these continue in the -1 frame. Ribosomes that continue in the -1 frame pause about 10 times longer than it takes to complete a peptide bond in vitro. Altering the rate of translational initiation alters the rate of frameshifting in vivo. Our in vitro and in vivo experiments can best be interpreted to mean that there are three methods by which ribosomes pass the frameshift site, only one of which results in frameshifting.
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Affiliation(s)
- J D Lopinski
- Department of Biological Sciences, State University of New York at Buffalo, Buffalo, New York 14260, USA
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32
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Takahashi RH, Nagashima K, Kurata T, Takahashi H. Analysis of human lymphotropic T-cell virus type II-like particle production by recombinant baculovirus-infected insect cells. Virology 1999; 256:371-80. [PMID: 10191202 DOI: 10.1006/viro.1999.9655] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular processes involved in retrovirus assembly and budding formation remain poorly understood. The gag-pro-pol genes of human lymphotropic T-cell virus type II (HTLV-II) are translated into Gag, Gag-Pro, or Gag-Pro-Pol by frameshift events. In the present study, we investigated the roles of the gag, pro, and pol regions of HTLV-II in viral particle formation using recombinant baculoviruses. In this study we could successfully produce mature HTLV-II viral particles containing core structures using a construct expressing the entire gag-pro-pol region. We also investigated the role of the pol region in particle formation. Deletion of the pol region affects viral particle assembly or release very little, indicating that the gag-pro region is sufficient for viral particle formation and maturation. Expression of the Gag proteins alone or Gag proteins with inactivated viral proteases (Pro) resulted in the formation of viral particles; however, these particles did not contain core structures. These results suggest the intracellular expression of Gag with Pro of HTLV-II is essential for the production of mature virus particles, whereas that of Pol is not.
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Affiliation(s)
- R H Takahashi
- Department of Pathology, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo, 162, Japan.
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33
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Carlson BA, Kwon SY, Chamorro M, Oroszlan S, Hatfield DL, Lee BJ. Transfer RNA modification status influences retroviral ribosomal frameshifting. Virology 1999; 255:2-8. [PMID: 10049815 DOI: 10.1006/viro.1998.9569] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The possibility of whether tRNAs with and without a highly modified base in their anticodon loop may influence the level of retroviral ribosomal frameshifting was examined. Rabbit reticulocyte lysates were programmed with mRNA encoding UUU or AAC at the frameshift site and the corresponding Phe tRNA with or without the highly modified wyebutoxine (Y) base on the 3' side of its anticodon or Asn tRNA with or without the highly modified queuine (Q) base in the wobble position of its anticodon added. Phe and Asn tRNAs without the Y or Q base, respectively, stimulated the level of frameshifting, suggesting that the frameshift event is influenced by tRNA modification status. In addition, when AAU occurred immediately upstream of UUU as the penultimate frameshift site codon, addition of tRNAAsn without the Q base reduced the stimulatory effect of tRNAPhe without the Y base, whereas addition of tRNAAsn with the Q base did not alter the stimulatory effect. The addition of tRNAAsn without the Q base and tRNAPhe with the Y base inhibited frameshifting. The latter studies suggest an interplay between the tRNAs decoded at the penulimate frameshift and frameshift site codons that is also influenced by tRNA modification status. These data may be intrepreted as indicating that a hypomodified isoacceptor modulates frameshifting in an upward manner when utilized at the frameshift site codon, but modulates frameshifting in a downward manner when utilized at the penultimate frameshift site codon.
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Affiliation(s)
- B A Carlson
- Laboratory of Basic Research, National Cancer Institute, Bethesda, Maryland 20892, USA
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34
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Müller B, Kräusslich HG. Characterization of human T-cell leukemia virus type I integrase expressed in Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 259:79-87. [PMID: 9914478 DOI: 10.1046/j.1432-1327.1999.00026.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The C-terminal part of the pol gene of the human T-cell leukemia virus type I (HTLV-I) is predicted to encode the integrase (IN) of the virus; however, this protein has not yet been detected in virions or infected cells. We expressed the putative IN from an infectious molecular clone of HTLV-I in Escherichia coli. Comparison with protein resulting from coexpression of HTLV-I protease (PR) and Pol in insect cells indicated that the bacterially expressed protein is identical with or very similar to IN released from a PR-Pol precursor by proteolytic cleavage. HTLV-I IN was purified from E. coli under native conditions. The protein behaved like a dimer in size-exclusion chromatography. It carried out activities characteristic of retroviral IN with high efficiency, displaying a strong preference for U5-derived vs. U3-derived sequences in the processing and strand-transfer reactions. In the disintegration reaction, HTLV-I IN not only accepted the double-stranded branched substrate corresponding to the product of a strand-transfer reaction, but was also able to carry out a phosphoryl transfer on a branched molecule with a single-stranded or a single adenosine overhang.
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Affiliation(s)
- B Müller
- Heinrich-Pette-Institut für experimentelle Virologie und Immunologie an der Universität Hamburg, Germany.
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35
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Trentin B, Rebeyrotte N, Mamoun RZ. Human T-cell leukemia virus type 1 reverse transcriptase (RT) originates from the pro and pol open reading frames and requires the presence of RT-RNase H (RH) and RT-RH-integrase proteins for its activity. J Virol 1998; 72:6504-10. [PMID: 9658093 PMCID: PMC109816 DOI: 10.1128/jvi.72.8.6504-6510.1998] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The first description of an active form of a recombinant human T-cell leukemia virus type 1 (HTLV-1) reverse transcriptase (RT) and subsequent predictions of its amino acid sequence and quaternary structure are reported here. By using amino acid alignment methods, the NH2 and COOH termini of the RT, RNase H (RH), and integrase (IN) domains of the Pol polyprotein were determined. The HTLV-1 RT seems to be unique since its NH2 terminus is probably encoded by the pro open reading frame (ORF) fused downstream, via a transframe peptide, to the polypeptide encoded by the pol ORF. The HTLV-1 Pol amino acid sequence was revealed to be highly similar to that of Rous sarcoma virus (RSV), particularly at the RT-RH hinge region. These two domains remain linked for RSV; this may also be the case for HTLV-1. In light of these results, RT, RT-RH, and RT-RH-IN genes were constructed and introduced into His-tagged protein expression vectors. The corresponding proteins were synthesized in vitro, and the DNA polymerase activities of different protein combinations were tested. Solely the RT-RH-RT-RH-IN combination was found to have a significant activity level. Velocity sedimentation analysis suggested that the HTLV-1 RT-RH and RT-RH-IN monomers are likely associated in an oligomeric structure, probably of the alpha3/beta type.
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Affiliation(s)
- B Trentin
- Laboratoire Rétrovirus et Thérapie, IFR INSERM/CNRS No. 66 Pathologies Infectieuses, Université Victor Segalen Bordeaux 2, F-33076 Bordeaux Cedex, France
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36
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Owen SM, Lal RB, Ikeda RA. Cloning and expression of a human T-lymphotropic virus type 1 protein with reverse transcriptase activity. J Virol 1998; 72:5279-84. [PMID: 9573305 PMCID: PMC110122 DOI: 10.1128/jvi.72.6.5279-5284.1998] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Unlike most other characterized retroviruses, there is little published information on the biochemical properties of human T-lymphotropic virus type 1 (HTLV-1) reverse transcriptase (RT). Specifically, no reports of a cloned functional RT enzyme have been published. Since the RT enzyme is an essential component of the virus, our objective was to clone, express, and purify a functional RT enzyme from HTLV-1. Our approach was to clone and express a protein of approximately 60 to 65 kDa that we hypothesized would correspond to the RT region encoded by the pol reading frame. The predicted region encoding the RT enzyme comprised nucleotides 2617 to 4312 of the HTLV-1 MT-2 isolate. A putative RT gene was obtained by PCR and was ligated into various prokaryotic expression vectors. A novel cloning approach allowed us to generate a stable clone in the prokaryotic expression vector pGEX-4T-1 and produce a recombinant protein of approximately 60 to 65 kDa. The partially purified protein displays RT activity in both amplification RT (AMP-RT) assays and traditional RT assays. This is the first report of a cloned protein from HTLV-1 which displays RT activity and is the first step in the characterization of HTLV-1 RT.
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Affiliation(s)
- S M Owen
- HIV and Retrovirus Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA
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Pichová I, Teplitsky A, Cubínková R, Zábranský A, Shoham G, Hrusková-Heidingsfeldová O. Subsequent selfprocessing of bovine leukemia virus proteinase in vitro. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 436:109-13. [PMID: 9561207 DOI: 10.1007/978-1-4615-5373-1_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- I Pichová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Prague, Czech Republic
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Fehrmann F, Welker R, Kräusslich HG. Intracisternal A-type particles express their proteinase in a separate reading frame by translational frameshifting, similar to D-type retroviruses. Virology 1997; 235:352-9. [PMID: 9281515 DOI: 10.1006/viro.1997.8708] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Intracisternal A-type particles (IAP) are defective endogenous retroviruses that accumulate in the endoplasmic reticulum of rodent cells. IAP genomes share extensive sequence homologies with D-type retroviruses, but were presumed to express the viral proteinase (PR) as part of the gag open reading frame (ORF) while D-type retroviruses express PR in a separate ORF. Here we show that expression of the murine IAP element MIA14 yields three major translation products, corresponding to the Gag, Gag-PR, and Gag-PR-Pol polyproteins. Sequence analysis revealed that MIA14 PR is encoded in its own reading frame, separate from gag and pol. Frameshifting occurred with an efficiency of approximately 25% between the gag and pro ORFs and 35% between pro and pol. The region containing the putative gag-pro frameshift signal consists of a heptanucleotide slippery sequence (A6C) and a stem-loop structure probably forming a pseudoknot. Deletion of this structure element almost completely abolished frameshifting. Insertion of an additional base next to the frameshift signal placed gag and pro in the same ORF and resulted in predominant formation of Gag-PR and Gag-PR-Pol polyproteins which were not processed following in vitro translation. Expression of a similar construct in tissue culture cells, on the other hand, led to efficient intracellular processing of the mutant polyproteins.
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Affiliation(s)
- F Fehrmann
- Heinrich-Pette-Institut, Martinistrasse 52, Hamburg, D-20251, Germany
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Larsen B, Gesteland RF, Atkins JF. Structural probing and mutagenic analysis of the stem-loop required for Escherichia coli dnaX ribosomal frameshifting: programmed efficiency of 50%. J Mol Biol 1997; 271:47-60. [PMID: 9300054 PMCID: PMC7126992 DOI: 10.1006/jmbi.1997.1162] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Three elements are crucial for the programmed frameshifting in translation of dnaX mRNA: a Shine-Dalgarno (SD)-like sequence, a double-shift site, and a 3' structure. The conformation of the mRNA containing these three elements was investigated using chemical and enzymatic probes. The probing data show that the structure is a specific stem-loop. The bottom half of the stem is more stable than the top half of the stem. The function of the stem-loop was further investigated by mutagenic analysis. Reducing the stability of the bottom half of the stem strongly effects frameshifting levels, whereas similar changes in the top half are not as effective. Stabilizing the top half of the stem gives increased frameshifting beyond the WT efficiency. The identity of the primary RNA sequence in the stem-loop is unimportant, provided that the overall structure is maintained. The calculated stabilities of the variant stem-loop structures correlate with frameshifting efficiency. The SD-interaction and the stem-loop element act independently to increase frameshifting in dnaX.
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Key Words
- dnax
- frameshifting
- recoding
- probing
- stem-loop structure
- sd, shine-dalgarno
- dms, dimethylsulfate
- cmct, 1-cyclohexyl-3-(morpholino-ethyl) carbodiimide metho-p-toluenesulfonate
- wt, wild-type
- ibv, infectious bronchitis virus
- mmtv, mouse mammary tumor virus
- hiv, human immunodeficiency virus
- pcr, polymerase chain reaction
- 2d, two-dimensional
- fiv, feline immunodeficiency virus
- htlv-ii, human t-cell leukemia virus type ii
- srv-1, simian retrovirus type 1
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Affiliation(s)
- B Larsen
- Department of Human Genetics, University of Utah, Salt Lake City 84112, USA
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Brierley I, Meredith MR, Bloys AJ, Hagervall TG. Expression of a coronavirus ribosomal frameshift signal in Escherichia coli: influence of tRNA anticodon modification on frameshifting. J Mol Biol 1997; 270:360-73. [PMID: 9237903 PMCID: PMC7126968 DOI: 10.1006/jmbi.1997.1134] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Eukaryotic ribosomal frameshift signals generally contain two elements, a heptanucleotide slippery sequence (XXXYYYN) and an RNA secondary structure, often an RNA pseudoknot, located downstream. Frameshifting takes place at the slippery sequence by simultaneous slippage of two ribosome-bound tRNAs. All of the tRNAs that are predicted to decode frameshift sites in the ribosomal A-site (XXXYYYN) possess a hypermodified base in the anticodon-loop and it is conceivable that these modifications play a role in the frameshift process. To test this, we expressed slippery sequence variants of the coronavirus IBV frameshift signal in strains of Escherichia coli unable to modify fully either tRNA(Lys) or tRNA(Asn). At the slippery sequences UUUAAAC and UUUAAAU (underlined codon decoded by tRNA(Asn), anticodon 5' QUU 3'), frameshifting was very inefficient (2 to 3%) and in strains deficient in the biosynthesis of Q base, was increased (AAU) or decreased (AAC) only two-fold. In E. coli, therefore, hypomodification of tRNA(Asn) had little effect on frameshifting. The situation with the efficient slippery sequences UUUAAAA (15%) and UUUAAAG (40%) (underlined codon decoded by tRNA(Lys), anticodon 5' mnm5s2UUU 3') was more complex, since the wobble base of tRNA(Lys) is modified at two positions. Of four available mutants, only trmE (s2UUU) had a marked influence on frameshifting, increasing the efficiency of the process at the slippery sequence UUUAAAA. No effect on frameshifting was seen in trmC1 (cmnm5s2UUU) or trmC2 (nm5s2UUU) strains and only a very small reduction (at UUUAAAG) was observed in an asuE (mnm5UUU) strain. The slipperiness of tRNA(Lys), therefore, cannot be ascribed to a single modification site on the base. However, the data support a role for the amino group of the mnm5 substitution in shaping the anticodon structure. Whether these conclusions can be extended to eukaryotic translation systems is uncertain. Although E. coli ribosomes changed frame at the IBV signal (UUUAAAG) with an efficiency similar to that measured in reticulocyte lysates (40%), there were important qualitative differences. Frameshifting of prokaryotic ribosomes was pseudoknot-independent (although secondary structure dependent) and appeared to require slippage of only a single tRNA.
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Key Words
- ribosomal frameshifting
- trna anticodon modification
- rna pseudoknot
- lysyl-trna
- q base
- rsv, rous sarcoma virus
- orf, open reading frame
- q, queuosine
- y, wyebutoxine
- hiv, human immunodeficiency virus
- htlv, human t-cell leukaemia virus
- blv, bovine leukaemia virus
- ibv, infectious bronchitis virus
- rrl, rabbit reticulocyte lysate
- iptg, isopropyl-β, d-thiogalactopyranoside
- tgt, trna guanine transglycosylase
- mmtv, mouse mammary tumour virus
- pfu, plaque-forming units
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Affiliation(s)
- I Brierley
- Department of Pathology, University of Cambridge, UK
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Van Brüssel M, Goubau P, Rousseau R, Desmyter J, Vandamme AM. Complete nucleotide sequence of the new simian T-lymphotropic virus, STLV-PH969 from a Hamadryas baboon, and unusual features of its long terminal repeat. J Virol 1997; 71:5464-72. [PMID: 9188619 PMCID: PMC191787 DOI: 10.1128/jvi.71.7.5464-5472.1997] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A third type of primate T-lymphotropic virus, PTLV-L, with STLV-PH969 as a prototype, has recently been isolated from an African baboon (Papio hamadryas). Classification of this virus has been based on partial sequence analysis of cDNA from a virus-producing cell line, PH969. We obtained the complete nucleotide sequence of this virus with a proviral genome of 8,916 bp. All major genes, homologous in all human T-cell lymphotropic virus (HTLV)-related viruses, and their corresponding mRNAs, including appropriate splicing, were identified. One additional nonhomologous open reading frame in the proximal pX region is accessible for translation through alternative splicing. Sequence comparison shows that STLV-PH969 is equidistantly related to HTLV type 1 (HTLV-1) and HTLV-2. In all coding regions, the similarity tends to be the lowest between STLV-PH969 and HTLV-1. However, in the long terminal repeat (LTR) region, the lowest similarity was found between STLV-PH969 and HTLV-2. The U3-R and R-U5 boundaries of the STLV-PH969 LTR were experimentally determined at nucleotides 268 and 524, respectively. This 695-bp LTR is 60 and 73 bp shorter than the LTRs of HTLV-1 and HTLV-2, respectively, but its general organization is similar to the one found in the HTLV-bovine leukemia virus genus. In the long region between the polyadenylation signal and the poly(A) site, sequence similarity with the HTLV-1 Rex-responsive element (RexRE) core and secondary structure prediction suggest the presence of a RexRE. The presence of three 21-bp repeats is conserved within the U3 region of HTLV-1, HTLV-2, and BLV. Only two direct repeats with similarity to these Tax-responsive elements were found in the STLV-PH969 LTR, which might suggest differences in the Tax-mediated transactivation of this virus. We conclude that STLV-PH969 has all the genes and genomic regions to suggest a replication cycle comparable to that of HTLV-1 and HTLV-2.
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Affiliation(s)
- M Van Brüssel
- Rega Institute for Medical Research and University Hospitals, Leuven, Belgium.
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Abstract
Errors that alter the reading frame occur extremely rarely during translation, yet some genes have evolved sequences that efficiently induce frameshifting. These sequences, termed programmed frameshift sites, manipulate the translational apparatus to promote non-canonical decoding. Frameshifts are mechanistically diverse. Most cause a -1 shift of frames; the first such site was discovered in a metazoan retrovirus, but they are now known to be dispersed quite widely among evolutionarily diverse species. +1 frameshift sites are much less common, but again dispersed widely. The rarest form are the translational hop sites which program the ribosome to bypass a region of several dozen nucleotides. Each of these types of events are stimulated by distinct mechanisms. All of the events share a common phenomenology in which the programmed frameshift site causes the ribosome to pause during elongation so that the kinetically unfavorable alternative decoding event can occur. During this pause most frameshifts occur because one or more ribosome-bound tRNAs slip between cognate or near-cognate codons. However, even this generalization is not entirely consistent, since some frameshifts occur without slippage. Because of their similarity to rarer translational errors, programmed frameshift sites provide a tool with which to probe the mechanism of frame maintenance.
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Affiliation(s)
- P J Farabaugh
- Department of Biological Sciences, University of Maryland, Baltimore 21228, USA
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Affiliation(s)
- P J Farabaugh
- Department of Biological Sciences, University of Maryland, Baltimore 21228, USA.
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Affiliation(s)
- P J Farabaugh
- Department of Biological Sciences, University of Maryland, Baltimore 21228, USA.
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Hu PY, Waheed A, Sly WS. Partial rescue of human carbonic anhydrase II frameshift mutation by ribosomal frameshift. Proc Natl Acad Sci U S A 1995; 92:2136-40. [PMID: 7892236 PMCID: PMC42438 DOI: 10.1073/pnas.92.6.2136] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A single-base-pair deletion in exon 7 of the human carbonic anhydrase II gene was found to be the molecular defect in a group of independently ascertained, clinically heterogeneous, Hispanic carbonic anhydrase II-deficient patients, all of whom had ancestors from the Caribbean islands. This mutation predicts a +1 frameshift at codon 227 and incorporation of 12 missense amino acids before an early stop codon at position 239 produces a 27-kDa truncated carbonic anhydrase II. Expression of the Hispanic mutant cDNA in bacteria produced predominantly the 27-kDa protein, which was inactive. However, a minor 29-kDa polypeptide species was also produced that had 10% the specific activity of the wild-type enzyme after affinity purification. Amino acid sequencing showed that the 29-kDa mutant protein was produced by two frameshift events: a +1 frameshift at codon 227 due to the single-base deletion and a -1 ribosomal frameshift at codon 237 that restored the original reading frame after 11 missense amino acids were incorporated. Antibody against the 11-amino acid frameshift peptide detected the 29-kDa mutant protein in lysates of transfected COS cells. These results indicate that ribosomal frameshift can partially rescue the human carbonic anhydrase II frameshift mutation and suggest a mechanism whereby a compensatory ribosomal frameshift can ameliorate the consequences of certain frameshift mutations. Whether individual differences in efficiency of ribosomal frameshift contribute to clinical heterogeneity in patients with such mutations deserves further study.
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Affiliation(s)
- P Y Hu
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, MO 63104
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Affiliation(s)
- E Chen
- Department of Biological Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486
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Herold J, Siddell SG. An 'elaborated' pseudoknot is required for high frequency frameshifting during translation of HCV 229E polymerase mRNA. Nucleic Acids Res 1993; 21:5838-42. [PMID: 8290341 PMCID: PMC310462 DOI: 10.1093/nar/21.25.5838] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The RNA polymerase gene (gene 1) of the human coronavirus 229E is approximately 20 kb in length and is located at the 5' end of the positive-strand genomic RNA. The coding sequence of gene 1 is divided into two large open reading frames, ORF1a and ORF1b, that overlap by 43 nucleotides. In the region of the ORF1a/ORF1b overlap, the genomic RNA displays two elements that are known to mediate (-1) ribosomal frameshifting. These are the slippery sequence, UUUAAAC, and a 3' pseudoknot structure. By introducing site-specific mutations into synthetic mRNAs, we have analysed the predicted structure of the HCV 229E pseudoknot and shown that besides the well-known stem structures, S1 and S2, a third stem structure, S3, is required for a high frequency of frameshifting. The requirement for an S3 stem is independent of the length of loop 2.
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Affiliation(s)
- J Herold
- Institute of Virology, University of Würzburg, Germany
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Falk H, Mador N, Udi R, Panet A, Honigman A. Two cis-acting signals control ribosomal frameshift between human T-cell leukemia virus type II gag and pro genes. J Virol 1993; 67:6273-7. [PMID: 8371359 PMCID: PMC238052 DOI: 10.1128/jvi.67.10.6273-6277.1993] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The open reading frame of the human T-cell leukemia virus type II pro gene is arranged at a -1 position relative to the gag gene. Synthesis of the Gag-Pro fusion polyprotein is facilitated by ribosomal frameshift into the reading frame of the pro gene. Cloning of a synthetic 41-bp oligonucleotide corresponding to the gag-pro junction within a heterologous gene (nef of human immunodeficiency virus type I) and mutation analysis revealed that two cis-acting signals, an adenosine residue stretch and a dyad symmetry sequence, flanking the UAA termination codon, are required for efficient ribosomal frameshifting between gag and pro. The stability of the stem-loop structure is crucial for frameshifting.
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Affiliation(s)
- H Falk
- Department of Molecular Genetics, Hebrew University, Hadassah Medical School, Jerusalem, Israel
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Reil H, Kollmus H, Weidle UH, Hauser H. A heptanucleotide sequence mediates ribosomal frameshifting in mammalian cells. J Virol 1993; 67:5579-84. [PMID: 8350413 PMCID: PMC237961 DOI: 10.1128/jvi.67.9.5579-5584.1993] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Ribosomal frameshifting is an essential requirement for replication of many viruses and retrovirus-like elements. It is regarded as a potential target for antiretroviral therapy. It has been shown that the frameshifting event takes place in the -1 direction within a sequence, the slippery sequence, which is usually followed by structured RNA. To distinguish between the basic sequence requirements and the modulating elements in intact cells, we have established a sensitive assay system for quantitative determination of ribosomal frameshifting in mammalian cell culture. In this assay system, the gag and pol genes of human immunodeficiency virus type 1 are replaced by the genes for the functional enzymes beta-galactosidase and luciferase, respectively. The sensitivity of the test system allows us to demonstrate for the first time that the slippery sequence, a heptanucleotide, is sufficient to mediate a basal level of ribosomal frameshifting independent of its position within a gene. The stem-loop sequence serves only as a positive modulator. These data indicate that frameshifting could also occur during translation of cellular genes in which a slippery sequence is present within the reading frame. The resulting putative transframe proteins might have a functional importance for cellular processes.
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Affiliation(s)
- H Reil
- Genetics of Eukaryotes, Gesellschaft für Biotechnologische Forschung mbH, Braunschweig, Germany
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