1
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Yasin S, Lesko SL, Kharytonchyk S, Brown JD, Chaudry I, Geleta SA, Tadzong NF, Zheng MY, Patel HB, Kengni G, Neubert E, Quiambao JMC, Becker G, Ghinger FG, Thapa S, Williams A, Radov MH, Boehlert KX, Hollmann NM, Singh K, Bruce JW, Marchant J, Telesnitsky A, Sherer NM, Summers MF. Role of RNA structural plasticity in modulating HIV-1 genome packaging and translation. Proc Natl Acad Sci U S A 2024; 121:e2407400121. [PMID: 39110735 PMCID: PMC11331132 DOI: 10.1073/pnas.2407400121] [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: 04/13/2024] [Accepted: 07/09/2024] [Indexed: 08/21/2024] Open
Abstract
HIV-1 transcript function is controlled in part by twinned transcriptional start site usage, where 5' capped RNAs beginning with a single guanosine (1G) are preferentially packaged into progeny virions as genomic RNA (gRNA) whereas those beginning with three sequential guanosines (3G) are retained in cells as mRNAs. In 3G transcripts, one of the additional guanosines base pairs with a cytosine located within a conserved 5' polyA element, resulting in formation of an extended 5' polyA structure as opposed to the hairpin structure formed in 1G RNAs. To understand how this remodeling influences overall transcript function, we applied in vitro biophysical studies with in-cell genome packaging and competitive translation assays to native and 5' polyA mutant transcripts generated with promoters that differentially produce 1G or 3G RNAs. We identified mutations that stabilize the 5' polyA hairpin structure in 3G RNAs, which promote RNA dimerization and Gag binding without sequestering the 5' cap. None of these 3G transcripts were competitively packaged, confirming that cap exposure is a dominant negative determinant of viral genome packaging. For all RNAs examined, conformations that favored 5' cap exposure were both poorly packaged and more efficiently translated than those that favored 5' cap sequestration. We propose that structural plasticity of 5' polyA and other conserved RNA elements place the 5' leader on a thermodynamic tipping point for low-energetic (~3 kcal/mol) control of global transcript structure and function.
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Affiliation(s)
- Saif Yasin
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Sydney L. Lesko
- Department of Oncology, McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI53705
- Department of Oncology, Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI53705
| | - Siarhei Kharytonchyk
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI48109-5620
| | - Joshua D. Brown
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Issac Chaudry
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Samuel A. Geleta
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Ndeh F. Tadzong
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Mei Y. Zheng
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Heer B. Patel
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Gabriel Kengni
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Emma Neubert
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | | | - Ghazal Becker
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Frances Grace Ghinger
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Sreeyasha Thapa
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - A’Lyssa Williams
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Michelle H. Radov
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Kellie X. Boehlert
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Nele M. Hollmann
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
- HHMI, University of Maryland, Baltimore County, MD21250
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, MD21250
| | - Karndeep Singh
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - James W. Bruce
- Department of Oncology, McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI53705
- Department of Oncology, Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI53705
| | - Jan Marchant
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
| | - Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI48109-5620
| | - Nathan M. Sherer
- Department of Oncology, McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI53705
- Department of Oncology, Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI53705
| | - Michael F. Summers
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD21250
- HHMI, University of Maryland, Baltimore County, MD21250
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, MD21250
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2
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Namer LS, Harwig A, Heynen SP, Das AT, Berkhout B, Kaempfer R. HIV co-opts a cellular antiviral mechanism, activation of stress kinase PKR by its RNA, to enable splicing of rev/tat mRNA. Cell Biosci 2023; 13:28. [PMID: 36774495 PMCID: PMC9922466 DOI: 10.1186/s13578-023-00972-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 01/24/2023] [Indexed: 02/13/2023] Open
Abstract
BACKGROUND Activation of RNA-dependent stress kinase PKR, especially by viral double-stranded RNA, induces eukaryotic initiation factor 2 α-chain (eIF2α) phosphorylation, attenuating thereby translation. We report that this RNA-mediated negative control mechanism, considered a cornerstone of the cell's antiviral response, positively regulates splicing of a viral mRNA. RESULTS Excision of the large human immunodeficiency virus (HIV) rev/tat intron depends strictly on activation of PKR by the viral RNA and on eIF2α phosphorylation. Rev/tat mRNA splicing was blocked by viral PKR antagonists Vaccinia E3L and Ebola VP35, as well as by a trans-dominant negative mutant of PKR, yet enhanced by overexpressing PKR. Expression of non-phosphorylatable mutant eIF2αS51A, but not of wild type eIF2α, abrogated efficient splicing of rev/tat mRNA. By contrast, expression of eIF2αS51D, a phosphomimetic mutant of eIF2α, left rev/tat mRNA splicing intact. Unlike eIF2αS51A, eIF2αS51D does not inhibit eIF2α phosphorylation by activated PKR. All HIV mRNA species contain terminal trans-activation response (TAR) stem-loop sequences that potentially could activate PKR, yet even upon TAR deletion, HIV mRNA production remained sensitive to inhibitors of PKR activation. Bioinformatic and mutational analyses revealed a compact RNA pseudoknot upstream of 3'-terminal TAR that promotes splicing by activating PKR. Supporting its essential role in control of splicing, this pseudoknot is conserved among diverse HIV and nonhuman primate SIVcpz isolates. The pseudoknot and 3'-terminal TAR collaborate in mediating PKR-regulated splicing of rev/tat intron, the pseudoknot being dominant. CONCLUSIONS Our results on HIV provide the first example of a virus co-opting activation of PKR by its RNA, a cellular antiviral mechanism, to promote splicing. They raise the question whether other viruses may use local activation of host kinase PKR through RNA elements within their genome to achieve efficient splicing of their mRNA. Our experiments reveal an indispensable role for eIF2α phosphorylation in HIV rev/tat mRNA splicing that accounts for the need for PKR activation.
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Affiliation(s)
- Lise Sarah Namer
- grid.9619.70000 0004 1937 0538Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102 Jerusalem, Israel
| | - Alex Harwig
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Stephan P. Heynen
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Atze T. Das
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Ben Berkhout
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102, Jerusalem, Israel.
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3
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Ding P, Summers MF. Sequestering the 5′‐cap for viral RNA packaging. Bioessays 2022; 44:e2200104. [PMID: 36101513 DOI: 10.1002/bies.202200104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/28/2022] [Accepted: 08/31/2022] [Indexed: 11/11/2022]
Abstract
Many viruses evolved mechanisms for capping the 5'-ends of their plus-strand RNAs as a means of hijacking the eukaryotic messenger RNA (mRNA) splicing/translation machinery. Although capping is critical for replication, the RNAs of these viruses have other essential functions including their requirement to be packaged as either genomes or pre-genomes into progeny viruses. Recent studies indicate that human immunodeficiency virus type-1 (HIV-1) RNAs are segregated between splicing/translation and packaging functions by a mechanism that involves structural sequestration of the 5'-cap. Here, we examined studies reported for other viruses and retrotransposons that require both selective packaging of their RNAs and 5'-RNA capping for host-mediated translation. Our findings suggest that viruses and retrotransposons have evolved multiple mechanisms to control 5'-cap accessibility, consistent with the hypothesis that removal or sequestration of the 5' cap enables packageable RNAs to avoid capture by the cellular RNA processing and translation machinery.
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Affiliation(s)
- Pengfei Ding
- Department of Chemistry and Biochemistry and Howard Hughes Medical Institute University of Maryland Baltimore County Baltimore Maryland USA
| | - Michael F. Summers
- Department of Chemistry and Biochemistry and Howard Hughes Medical Institute University of Maryland Baltimore County Baltimore Maryland USA
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4
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Crespo R, Rao S, Mahmoudi T. HibeRNAtion: HIV-1 RNA Metabolism and Viral Latency. Front Cell Infect Microbiol 2022; 12:855092. [PMID: 35774399 PMCID: PMC9237370 DOI: 10.3389/fcimb.2022.855092] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/10/2022] [Indexed: 01/12/2023] Open
Abstract
HIV-1 infection remains non-curative due to the latent reservoir, primarily a small pool of resting memory CD4+ T cells bearing replication-competent provirus. Pharmacological reversal of HIV-1 latency followed by intrinsic or extrinsic cell killing has been proposed as a promising strategy to target and eliminate HIV-1 viral reservoirs. Latency reversing agents have been extensively studied for their role in reactivating HIV-1 transcription in vivo, although no permanent reduction of the viral reservoir has been observed thus far. This is partly due to the complex nature of latency, which involves strict intrinsic regulation at multiple levels at transcription and RNA processing. Still, the molecular mechanisms that control HIV-1 latency establishment and maintenance have been almost exclusively studied in the context of chromatin remodeling, transcription initiation and elongation and most known LRAs target LTR-driven transcription by manipulating these. RNA metabolism is a largely understudies but critical mechanistic step in HIV-1 gene expression and latency. In this review we provide an update on current knowledge on the role of RNA processing mechanisms in viral gene expression and latency and speculate on the possible manipulation of these pathways as a therapeutic target for future cure studies.
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Affiliation(s)
- Raquel Crespo
- Department of Biochemistry, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Shringar Rao
- Department of Biochemistry, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Tokameh Mahmoudi
- Department of Biochemistry, Erasmus University Medical Center, Rotterdam, Netherlands
- Department of Pathology, Erasmus University Medical Center, Rotterdam, Netherlands
- Department of Urology, Erasmus University Medical Center, Rotterdam, Netherlands
- *Correspondence: Tokameh Mahmoudi,
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5
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Abstract
Genetically-characterizing full-length HIV-1 RNA is critical for identifying genetically-intact genomes and for comparing these RNA genomes to proviral DNA. We have developed a method for sequencing plasma-derived RNA using long-range sequencing (PRLS assay; ∼8.3 kb from gag to the 3′ end or ∼5 kb from integrase to the 3′ end). We employed the gag-3′ PRLS assay to sequence HIV-1 RNA genomes from ART-naive participants during acute/early infection (n = 6) or chronic infection (n = 2). On average, only 65% of plasma-derived genomes were genetically-intact. Defects were found in all genomic regions but were concentrated in env and pol. We compared these genomes to near-full-length proviral sequences from paired peripheral blood mononuclear cell (PBMC) samples for the acute/early group and found that near-identical (>99.98% identical) sequences were identified only during acute infection. For three participants who initiated therapy during acute infection, we used the int-3′ PRLS assay to sequence plasma-derived genomes from an analytical treatment interruption and identified 100% identical genomes between pretherapy and rebound time points. The PRLS assay provides a new level of sensitivity for understanding the genetic composition of plasma-derived HIV-1 RNA from viremic individuals either pretherapy or after treatment interruption, which will be invaluable in assessing possible HIV-1 curative strategies. IMPORTANCE We developed novel plasma-derived RNA using long-range sequencing assays (PRLS assay; 8.3 kb, gag-3′, and 5.0 kb, int-3′). Employing the gag-3′ PRLS assay, we found that 26% to 51% of plasma-derived genomes are genetically-defective, largely as a result of frameshift mutations and deletions. These genetic defects were concentrated in the env region compared to gag and pol, likely a reflection of viral immune escape in env during untreated HIV-1 infection. Employing the int-3′ PRLS assay, we found that analytical treatment interruption (ATI) plasma-derived sequences were identical and genetically-intact. Several sequences from the ATI plasma samples were identical to viral sequences from pretherapy plasma and PBMC samples, indicating that HIV-1 reservoirs established prior to therapy contribute to viral rebound during an ATI. Therefore, near-full-length sequencing of HIV-1 particles is required to gain an accurate picture of the genetic landscape of plasma HIV-1 virions in studies of HIV-1 replication and persistence.
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6
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Blakemore RJ, Burnett C, Swanson C, Kharytonchyk S, Telesnitsky A, Munro JB. Stability and conformation of the dimeric HIV-1 genomic RNA 5'UTR. Biophys J 2021; 120:4874-4890. [PMID: 34529947 PMCID: PMC8595565 DOI: 10.1016/j.bpj.2021.09.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 08/13/2021] [Accepted: 09/08/2021] [Indexed: 12/20/2022] Open
Abstract
During HIV-1 assembly, the viral Gag polyprotein specifically selects the dimeric RNA genome for packaging into new virions. The 5' untranslated region (5'UTR) of the dimeric genome may adopt a conformation that is optimal for recognition by Gag. Further conformational rearrangement of the 5'UTR, promoted by the nucleocapsid (NC) domain of Gag, is predicted during virus maturation. Two 5'UTR dimer conformations, the kissing dimer (KD) and the extended dimer (ED), have been identified in vitro, which differ in the extent of intermolecular basepairing. Whether 5'UTRs from different HIV-1 strains with distinct sequences have access to the same dimer conformations has not been determined. Here, we applied fluorescence cross-correlation spectroscopy and single-molecule Förster resonance energy transfer imaging to demonstrate that 5'UTRs from two different HIV-1 subtypes form (KDs) with divergent stabilities. We further show that both 5'UTRs convert to a stable dimer in the presence of the viral NC protein, adopting a conformation consistent with extensive intermolecular contacts. These results support a unified model in which the genomes of diverse HIV-1 strains adopt an ED conformation.
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Affiliation(s)
- Robert J Blakemore
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine and School of Graduate Biomedical Sciences, Boston, Massachusetts; Graduate Program in Molecular Microbiology, Tufts University Graduate School of Biomedical Sciences, Boston, Massachusetts
| | - Cleo Burnett
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Canessa Swanson
- Department of Chemistry and Biochemistry, University of Maryland Baltimore Country, Baltimore, Maryland
| | - Siarhei Kharytonchyk
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan
| | - James B Munro
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine and School of Graduate Biomedical Sciences, Boston, Massachusetts; Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts; Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts.
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7
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Grewe B, Vogt C, Horstkötter T, Tippler B, Xiao H, Müller B, Überla K, Wagner R, Asbach B, Bohne J. The HIV 5' Gag Region Displays a Specific Nucleotide Bias Regulating Viral Splicing and Infectivity. Viruses 2021; 13:v13060997. [PMID: 34071819 PMCID: PMC8227319 DOI: 10.3390/v13060997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/17/2021] [Accepted: 05/22/2021] [Indexed: 11/16/2022] Open
Abstract
Alternative splicing and the expression of intron-containing mRNAs is one hallmark of HIV gene expression. To facilitate the otherwise hampered nuclear export of non-fully processed mRNAs, HIV encodes the Rev protein, which recognizes its intronic response element and fuels the HIV RNAs into the CRM-1-dependent nuclear protein export pathway. Both alternative splicing and Rev-dependency are regulated by the primary HIV RNA sequence. Here, we show that these processes are extremely sensitive to sequence alterations in the 5’coding region of the HIV genomic RNA. Increasing the GC content by insertion of either GFP or silent mutations activates a cryptic splice donor site in gag, entirely deregulates the viral splicing pattern, and lowers infectivity. Interestingly, an adaptation of the inserted GFP sequence toward an HIV-like nucleotide bias reversed these phenotypes completely. Of note, the adaptation yielded completely different primary sequences although encoding the same amino acids. Thus, the phenotypes solely depend on the nucleotide composition of the two GFP versions. This is a strong indication of an HIV-specific mRNP code in the 5′ gag region wherein the primary RNA sequence bias creates motifs for RNA-binding proteins and controls the fate of the HIV-RNA in terms of viral gene expression and infectivity.
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Affiliation(s)
- Bastian Grewe
- Department of Molecular and Medical Virology, Ruhr-University, 44801 Bochum, Germany; (B.G.); (B.T.); (H.X.); (B.M.); (K.Ü.)
| | - Carolin Vogt
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany; (C.V.); (T.H.)
| | - Theresa Horstkötter
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany; (C.V.); (T.H.)
| | - Bettina Tippler
- Department of Molecular and Medical Virology, Ruhr-University, 44801 Bochum, Germany; (B.G.); (B.T.); (H.X.); (B.M.); (K.Ü.)
- Department of Biochemistry, Ruhr-University, 44780 Bochum, Germany
| | - Han Xiao
- Department of Molecular and Medical Virology, Ruhr-University, 44801 Bochum, Germany; (B.G.); (B.T.); (H.X.); (B.M.); (K.Ü.)
- Institute of Clinical and Molecular Virology, University Clinics Erlangen, 91054 Erlangen, Germany
| | - Bianca Müller
- Department of Molecular and Medical Virology, Ruhr-University, 44801 Bochum, Germany; (B.G.); (B.T.); (H.X.); (B.M.); (K.Ü.)
| | - Klaus Überla
- Department of Molecular and Medical Virology, Ruhr-University, 44801 Bochum, Germany; (B.G.); (B.T.); (H.X.); (B.M.); (K.Ü.)
- Institute of Clinical and Molecular Virology, University Clinics Erlangen, 91054 Erlangen, Germany
| | - Ralf Wagner
- Institute of Medical Microbiology and Hygiene, University Regensburg, 93053 Regensburg, Germany; (R.W.); (B.A.)
- Institute of Clinical Microbiology and Hygiene, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Benedikt Asbach
- Institute of Medical Microbiology and Hygiene, University Regensburg, 93053 Regensburg, Germany; (R.W.); (B.A.)
| | - Jens Bohne
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany; (C.V.); (T.H.)
- Correspondence: ; Tel.: +49-511-532-4308
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8
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Boyd PS, Brown JB, Brown JD, Catazaro J, Chaudry I, Ding P, Dong X, Marchant J, O’Hern CT, Singh K, Swanson C, Summers MF, Yasin S. NMR Studies of Retroviral Genome Packaging. Viruses 2020; 12:v12101115. [PMID: 33008123 PMCID: PMC7599994 DOI: 10.3390/v12101115] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/18/2020] [Accepted: 09/26/2020] [Indexed: 12/03/2022] Open
Abstract
Nearly all retroviruses selectively package two copies of their unspliced RNA genomes from a cellular milieu that contains a substantial excess of non-viral and spliced viral RNAs. Over the past four decades, combinations of genetic experiments, phylogenetic analyses, nucleotide accessibility mapping, in silico RNA structure predictions, and biophysical experiments were employed to understand how retroviral genomes are selected for packaging. Genetic studies provided early clues regarding the protein and RNA elements required for packaging, and nucleotide accessibility mapping experiments provided insights into the secondary structures of functionally important elements in the genome. Three-dimensional structural determinants of packaging were primarily derived by nuclear magnetic resonance (NMR) spectroscopy. A key advantage of NMR, relative to other methods for determining biomolecular structure (such as X-ray crystallography), is that it is well suited for studies of conformationally dynamic and heterogeneous systems—a hallmark of the retrovirus packaging machinery. Here, we review advances in understanding of the structures, dynamics, and interactions of the proteins and RNA elements involved in retroviral genome selection and packaging that are facilitated by NMR.
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9
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Donegà S, Rogalska ME, Pianigiani G, Igreja S, Amaral MD, Pagani F. Rescue of common exon-skipping mutations in cystic fibrosis with modified U1 snRNAs. Hum Mutat 2020; 41:2143-2154. [PMID: 32935393 DOI: 10.1002/humu.24116] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/31/2020] [Accepted: 09/07/2020] [Indexed: 01/22/2023]
Abstract
In cystic fibrosis (CF), the correction of splicing defects represents an interesting therapeutic approach to restore normal CFTR function. In this study, we focused on 10 common mutations/variants 711+3A>G/C, 711+5G>A, TG13T3, TG13T5, TG12T5, 1863C>T, 1898+3A>G, 2789+5G>A, and 3120G>A that induce skipping of the corresponding CFTR exons 5, 10, 13, 16, and 18. To rescue the splicing defects we tested, in a minigene assay, a panel of modified U1 small nuclear RNAs (snRNAs), named Exon Specific U1s (ExSpeU1s), that was engineered to bind to intronic sequences downstream of each defective exon. Using this approach, we show that all 10 splicing mutations analyzed are efficiently corrected by specific ExSpeU1s. Using complementary DNA-splicing competent minigenes, we also show that the ExspeU1-mediated splicing correction at the RNA level recovered the full-length CFTR protein for 1863C>T, 1898+3A>G, 2789+5G>A variants. In addition, detailed mutagenesis experiments performed on exon 13 led us to identify a novel intronic regulatory element involved in the ExSpeU1-mediated splicing rescue. These results provide a common strategy based on modified U1 snRNAs to correct exon skipping in a group of disease-causing CFTR mutations.
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Affiliation(s)
- Stefano Donegà
- Human Molecular Genetics, ICGEB - International Center for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Malgorzata Ewa Rogalska
- Human Molecular Genetics, ICGEB - International Center for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Giulia Pianigiani
- Human Molecular Genetics, ICGEB - International Center for Genetic Engineering and Biotechnology, Trieste, Italy
| | - Susana Igreja
- BioISI - Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
| | - Margarida Duarte Amaral
- BioISI - Biosystems and Integrative Sciences Institute, Faculty of Sciences, University of Lisbon, Lisbon, Portugal
| | - Franco Pagani
- Human Molecular Genetics, ICGEB - International Center for Genetic Engineering and Biotechnology, Trieste, Italy
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10
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Esquiaqui JM, Kharytonchyk S, Drucker D, Telesnitsky A. HIV-1 spliced RNAs display transcription start site bias. RNA (NEW YORK, N.Y.) 2020; 26:708-714. [PMID: 32205324 PMCID: PMC7266155 DOI: 10.1261/rna.073650.119] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 03/17/2020] [Indexed: 05/13/2023]
Abstract
Human immunodeficiency virus type 1 (HIV-1) transcripts have three fates: to serve as genomic RNAs, unspliced mRNAs, or spliced subgenomic mRNAs. Recent structural studies have shown that sequences near the 5' end of HIV-1 RNA can adopt at least two alternate three-dimensional conformations, and that these structures dictate genome versus unspliced mRNA fates. HIV-1's use of alternate transcription start sites (TSS) can influence which RNA conformer is generated, and this choice, in turn, dictates the fate of the unspliced RNA. The structural context of HIV-1's major 5' splice site differs in these two RNA conformers, suggesting that the conformers may differ in their ability to support HIV-1 splicing events. Here, we tested the hypothesis that TSS that shift the RNA monomer/dimer structural equilibrium away from the splice site sequestering dimer-competent fold would favor splicing. Consistent with this hypothesis, the results showed that the 5' ends of spliced HIV-1 RNAs were enriched in 3GCap structures and depleted of 1GCap RNAs relative to the total intracellular RNA population. These findings expand the functional significance of HIV-1 RNA structural dynamics by demonstrating roles for RNA structure in defining all three classes of HIV-1 RNAs, and suggest that HIV-1 TSS choice initiates a cascade of molecular events that dictate the fates of nascent HIV-1 RNAs.
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Affiliation(s)
- Jackie M Esquiaqui
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5620, USA
| | - Siahrei Kharytonchyk
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5620, USA
| | - Darra Drucker
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5620, USA
| | - Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-5620, USA
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11
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Sithole N, Williams CA, Abbink TEM, Lever AML. DDX5 potentiates HIV-1 transcription as a co-factor of Tat. Retrovirology 2020; 17:6. [PMID: 32228614 PMCID: PMC7106839 DOI: 10.1186/s12977-020-00514-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 03/16/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND HIV-1 does not encode a helicase and hijacks those of the cell for efficient replication. We and others previously showed that the DEAD box helicase, DDX5, is an essential HIV dependency factor. DDX5 was recently shown to be associated with the 7SK snRNP. Cellular positive transcription elongation factor b (P-TEFb) is bound in an inactive form with HEXIM1/2 on 7SK snRNP. The Tat/P-TEFb complex is essential for efficient processivity of Pol II in HIV-1 transcription elongation and Tat competes with HEXIM1/2 for P-TEFb. We investigated the precise role of DDX5 in HIV replication using siRNA mediated knockdown and rescue with DDX5 mutants which prevent protein-protein interactions and RNA and ATP binding. RESULTS We demonstrate a critical role for DDX5 in the Tat/HEXIM1 interaction. DDX5 acts to potentiate Tat activity and can bind both Tat and HEXIM1 suggesting it may facilitate the dissociation of HEXIM1/2 from the 7SK-snRNP complex, enhancing Tat/P-TEFb availability. We show knockdown of DDX5 in a T cell line significantly reduces HIV-1 infectivity and viral protein production. This activity is unique to DDX5 and cannot be substituted by its close paralog DDX17. Overexpression of DDX5 stimulates the Tat/LTR promoter but suppresses other cellular and viral promoters. Individual mutations of conserved ATP binding, RNA binding, helicase related or protein binding motifs within DDX5 show that the N terminal RNA binding motifs, the Walker B and the glycine doublet motifs are essential for this function. The Walker A and RNA binding motifs situated on the transactivation domain are however dispensable. CONCLUSION DDX5 is an essential cellular factor for efficient HIV transcription elongation. It interacts with Tat and may potentiate the availability of P-TEFb through sequestering HEXIM1.
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Affiliation(s)
- Nyaradzai Sithole
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK
| | - Claire A Williams
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK
- Department of Microbiology, Specialist Virology Centre, Norfolk and Norwich University Hospitals, Norwich, UK
| | - Truus E M Abbink
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK
- Department of Paediatrics, Child Neurology, Centre for Childhood White Matter Disorders, VU University Medical Centre, Amsterdam, The Netherlands
| | - Andrew M L Lever
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK.
- Department of Medicine, National University of Singapore, Singapore, 119228, Singapore.
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12
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Zaikos TD, Terry VH, Sebastian Kettinger NT, Lubow J, Painter MM, Virgilio MC, Neevel A, Taschuk F, Onafuwa-Nuga A, McNamara LA, Riddell J, Bixby D, Markowitz N, Collins KL. Hematopoietic Stem and Progenitor Cells Are a Distinct HIV Reservoir that Contributes to Persistent Viremia in Suppressed Patients. Cell Rep 2019; 25:3759-3773.e9. [PMID: 30590047 DOI: 10.1016/j.celrep.2018.11.104] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 09/12/2018] [Accepted: 11/29/2018] [Indexed: 01/03/2023] Open
Abstract
Long-lived reservoirs of persistent HIV are a major barrier to a cure. CD4+ hematopoietic stem and progenitor cells (HSPCs) have the capacity for lifelong survival, self-renewal, and the generation of daughter cells. Recent evidence shows that they are also susceptible to HIV infection in vitro and in vivo. Whether HSPCs harbor infectious virus or contribute to plasma virus (PV) is unknown. Here, we provide strong evidence that clusters of identical proviruses from HSPCs and their likely progeny often match residual PV. A higher proportion of these sequences match residual PV than proviral genomes from bone marrow and peripheral blood mononuclear cells that are observed only once. Furthermore, an analysis of near-full-length genomes isolated from HSPCs provides evidence that HSPCs harbor functional HIV proviral genomes that often match residual PV. These results support the conclusion that HIV-infected HSPCs form a distinct and functionally significant reservoir of persistent HIV in infected people.
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Affiliation(s)
- Thomas D Zaikos
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Valeri H Terry
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Nadia T Sebastian Kettinger
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, USA; Medical Scientist Training Program, University of Michigan, Ann Arbor, MI, USA
| | - Jay Lubow
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Mark M Painter
- Graduate Program in Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Maria C Virgilio
- Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, USA
| | - Andrew Neevel
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Frances Taschuk
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | | | - Lucy A McNamara
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - James Riddell
- Division of Infectious Disease, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Dale Bixby
- Division of Oncology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Norman Markowitz
- Division of Infectious Diseases, Henry Ford Hospital, Detroit, MI, USA
| | - Kathleen L Collins
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA; Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA; Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, MI, USA; Medical Scientist Training Program, University of Michigan, Ann Arbor, MI, USA; Division of Infectious Disease, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA; Graduate Program in Immunology, University of Michigan, Ann Arbor, MI, USA.
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13
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Das AT, Pasternak AO, Berkhout B. On the generation of the MSD-Ѱ class of defective HIV proviruses. Retrovirology 2019; 16:19. [PMID: 31296234 PMCID: PMC6625037 DOI: 10.1186/s12977-019-0481-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 07/05/2019] [Indexed: 11/10/2022] Open
Abstract
Antiretroviral therapy (ART) can effectively suppress ongoing HIV replication and block disease progression, but the infection is never cured due to the persistence of a small pool of latently infected cells hosting integrated replication-competent HIV proviruses. However, the vast majority of HIV proviruses in ART-treated patients are replication-incompetent due to a variety of genetic defects. Most defective proviruses (around 90%) contain large internal deletions or are G-to-A hypermutated, resulting in destruction of most if not all viral open reading frames, which is consistent with the idea that cytotoxic T cells (CTLs) effectively remove cells that produce viral antigens. An intriguing subclass of defective proviruses (around 10%) that are consistently detected in such patients carry a small deletion or a point mutation in a relatively precise and well conserved region near the 5ʹ end of the HIV genome, in the area that encodes the major splice donor (MSD) site and the packaging signal Ѱ in the viral RNA genome. Why this subclass of proviruses is defective has never been properly understood. We now propose a mechanistic scenario for how these MSD-Ѱ mutations can prevent viral protein expression. Based on ample results in literature, we argue that MSD inactivation triggers the activity of the 5ʹ-polyadenylation site, resulting in the production of ultra-short non-protein-coding HIV transcripts.
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Affiliation(s)
- Atze T Das
- Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Alexander O Pasternak
- Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, The Netherlands. .,Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.
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14
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Ptok J, Müller L, Theiss S, Schaal H. Context matters: Regulation of splice donor usage. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194391. [PMID: 31202784 DOI: 10.1016/j.bbagrm.2019.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/07/2019] [Accepted: 06/09/2019] [Indexed: 11/16/2022]
Abstract
Elaborate research on splicing, starting in the late seventies, evolved from the discovery that 5' splice sites are recognized by their complementarity to U1 snRNA towards the realization that RNA duplex formation cannot be the sole basis for 5'ss selection. Rather, their recognition is highly influenced by a number of context factors including transcript architecture as well as splicing regulatory elements (SREs) in the splice site neighborhood. In particular, proximal binding of splicing regulatory proteins highly influences splicing outcome. The importance of SRE integrity especially becomes evident in the light of human pathogenic mutations where single nucleotide changes in SREs can severely affect the resulting transcripts. Bioinformatics tools nowadays greatly assist in the computational evaluation of 5'ss, their neighborhood and the impact of pathogenic mutations. Although predictions are already quite robust, computational evaluation of the splicing regulatory landscape still faces challenges to increase future reliability. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.
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Affiliation(s)
- Johannes Ptok
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Lisa Müller
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Heiner Schaal
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
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15
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Sithole N, Williams CA, Vaughan AM, Kenyon JC, Lever AML. DDX17 Specifically, and Independently of DDX5, Controls Use of the HIV A4/5 Splice Acceptor Cluster and Is Essential for Efficient Replication of HIV. J Mol Biol 2018; 430:3111-3128. [PMID: 30131116 PMCID: PMC6119765 DOI: 10.1016/j.jmb.2018.06.052] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 06/26/2018] [Accepted: 06/27/2018] [Indexed: 12/11/2022]
Abstract
HIV splicing involves five splice donor and eight splice acceptor sequences which, together with cryptic splice sites, generate over 100 mRNA species. Ninety percent of both partially spliced and fully spliced transcripts utilize the intrinsically weak A4/A5 3' splice site cluster. We show that DDX17, but not its close paralog DDX5, specifically controls the usage of this splice acceptor group. In its absence, production of the viral envelope protein and other regulatory and accessory proteins is grossly reduced, while Vif, which uses the A1 splice acceptor, is unaffected. This is associated with a profound decrease in viral export from the cell. Loss of Vpu expression causing upregulation of cellular Tetherin compounds the phenotype. DDX17 utilizes distinct RNA binding motifs for its role in efficient HIV replication, and we identify RNA binding motifs essential for its role, while the Walker A, Walker B (DEAD), Q motif and the glycine doublet motif are all dispensable. We show that DDX17 interacts with SRSF1/SF2 and the heterodimeric auxiliary factor U2AF65/35, which are essential splicing factors in the generation of Rev and Env/Vpu transcripts.
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Affiliation(s)
- Nyaradzai Sithole
- Department of Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Claire A Williams
- Department of Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Aisling M Vaughan
- Department of Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Julia C Kenyon
- Department of Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK; Department of Microbiology and Immunology, National University of Singapore, Singapore 117545
| | - Andrew M L Lever
- Department of Medicine, University of Cambridge, Cambridge, CB2 0QQ, UK; Department of Medicine, National University of Singapore, Singapore 119228.
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16
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Singh G, Rife BD, Seufzer B, Salemi M, Rendahl A, Boris-Lawrie K. Identification of conserved, primary sequence motifs that direct retrovirus RNA fate. Nucleic Acids Res 2018; 46:7366-7378. [PMID: 29846681 PMCID: PMC6101577 DOI: 10.1093/nar/gky369] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 04/20/2018] [Accepted: 05/16/2018] [Indexed: 12/16/2022] Open
Abstract
Precise stoichiometry of genome-length transcripts and alternatively spliced mRNAs is a hallmark of retroviruses. We discovered short, guanosine and adenosine sequence motifs in the 5'untranslated region of several retroviruses and ascertained the reasons for their conservation using a representative lentivirus and genetically simpler retrovirus. We conducted site-directed mutagenesis of the GA-motifs in HIV molecular clones and observed steep replication delays in T-cells. Quantitative RNA analyses demonstrate the GA-motifs are necessary to retain unspliced viral transcripts from alternative splicing. Mutagenesis of the GA-motifs in a C-type retrovirus validate the similar downregulation of unspliced transcripts and virion structural protein. The evidence from cell-based co-precipitation studies shows the GA-motifs in the 5'untranslated region confer binding by SFPQ/PSF, a protein co-regulated with T-cell activation. Diminished SFPQ/PSF or mutation of either GA-motif attenuates the replication of HIV. The interaction of SFPQ/PSF with both GA-motifs is crucial for maintaining the stoichiometry of the viral transcripts and does not affect packaging of HIV RNA. Our results demonstrate the conserved GA-motifs direct the fate of retrovirus RNA. These findings have exposed an RNA-based molecular target to attenuate retrovirus replication.
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Affiliation(s)
- Gatikrushna Singh
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, MN 55108, USA
| | - Brittany D Rife
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Bradley Seufzer
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, MN 55108, USA
| | - Marco Salemi
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Aaron Rendahl
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, MN 55108, USA
| | - Kathleen Boris-Lawrie
- Department of Veterinary and Biomedical Sciences, University of Minnesota, Saint Paul, MN 55108, USA
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17
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The HIV-1 Tat Protein Enhances Splicing at the Major Splice Donor Site. J Virol 2018; 92:JVI.01855-17. [PMID: 29743356 DOI: 10.1128/jvi.01855-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 04/25/2018] [Indexed: 12/23/2022] Open
Abstract
Transcription of the HIV-1 proviral DNA and subsequent processing of the primary transcript results in the production of a large set of unspliced and differentially spliced viral RNAs. The major splice donor site (5'ss) that is located in the untranslated leader of the HIV-1 transcript is used for the production of all spliced RNAs, and splicing at this site has to be tightly regulated to allow the balanced production of all viral RNAs and proteins. We demonstrate that the viral Tat protein, which is known to activate viral transcription, also stimulates splicing at the major 5'ss. As for the transcription effect, Tat requires the viral long terminal repeat promoter and the trans-acting responsive RNA hairpin for splicing regulation. These results indicate that HIV-1 transcription and splicing are tightly coupled processes through the coordinated action of the essential Tat protein.IMPORTANCE The HIV-1 proviral DNA encodes a single RNA transcript that is used as RNA genome and packaged into newly assembled virus particles. This full-length RNA is also used as mRNA for the production of structural and enzymatic proteins. Production of other essential viral proteins depends on alternative splicing of the primary transcript, which yields a large set of differentially spliced mRNAs. Optimal virus replication requires a balanced production of all viral RNAs, which means that the splicing process has to be strictly regulated. We show that the HIV-1 Tat protein, a factor that is well known for its transcription activating function, also stimulates splicing. Thus, Tat controls not only the level of the viral RNA but also the balance between spliced and unspliced RNAs.
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18
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Pasternak AO, Berkhout B. What do we measure when we measure cell-associated HIV RNA. Retrovirology 2018; 15:13. [PMID: 29378657 PMCID: PMC5789533 DOI: 10.1186/s12977-018-0397-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 01/16/2018] [Indexed: 12/21/2022] Open
Abstract
Cell-associated (CA) HIV RNA has received much attention in recent years as a surrogate measure of the efficiency of HIV latency reversion and because it may provide an estimate of the viral reservoir size. This review provides an update on some recent insights in the biology and clinical utility of this biomarker. We discuss a number of important considerations to be taken into account when interpreting CA HIV RNA measurements, as well as different methods to measure this biomarker.
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Affiliation(s)
- Alexander O Pasternak
- Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center of the University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center of the University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
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19
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Sampathkumar R, Scott-Herridge J, Liang B, Kimani J, Plummer FA, Luo M. HIV-1 Subtypes and 5'LTR-Leader Sequence Variants Correlate with Seroconversion Status in Pumwani Sex Worker Cohort. Viruses 2017; 10:v10010004. [PMID: 29295533 PMCID: PMC5795417 DOI: 10.3390/v10010004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 12/18/2017] [Accepted: 12/20/2017] [Indexed: 01/04/2023] Open
Abstract
Within the Pumwani sex worker cohort, a subgroup remains seronegative, despite frequent exposure to HIV-1; some of them seroconverted several years later. This study attempts to identify viral variations in 5′LTR-leader sequences (5′LTR-LS) that might contribute to the late seroconversion. The 5′LTR-LS contains sites essential for replication and genome packaging, viz, primer binding site (PBS), major splice donor (SD), and major packaging signal (PS). The 5′LTR-LS of 20 late seroconverters (LSC) and 122 early seroconverters (EC) were amplified, cloned, and sequenced. HelixTree 6.4.3 was employed to classify HIV subtypes and sequence variants based on seroconversion status. We find that HIV-1 subtypes A1.UG and D.UG were overrepresented in the viruses infecting the LSC (P < 0.0001). Specific variants of PBS (Pc < 0.0001), SD1 (Pc < 0.0001), and PS (Pc < 0.0001) were present only in the viral population from EC or LSC. Combinations of PBS [PBS-2 (Pc < 0.0001) and PBS-3 (Pc < 0.0001)] variants with specific SD sequences were only seen in LSC or EC. Combinations of A1.KE or D with specific PBS and SD variants were only present in LSC or EC (Pc < 0.0001). Furthermore, PBS variants only present in LSC co-clustered with PBS references utilizing tRNAArg; whereas, the PBS variants identified only in EC co-clustered with PBS references using tRNALys,3 and its variants. This is the first report that specific PBS, SD1, and PS sequence variants within 5′LTR-LS are associated with HIV-1 seroconversion, and it could aid designing effective anti-HIV strategies.
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Affiliation(s)
- Raghavan Sampathkumar
- Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, R3E 3R2, Canada.
| | - Joel Scott-Herridge
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, R3E 3R2, Canada.
| | - Binhua Liang
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, R3E 3R2, Canada.
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
| | - Joshua Kimani
- Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
- Department of Medical Microbiology, University of Nairobi, Nairobi, Kenya.
| | - Francis A Plummer
- Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, R3E 3R2, Canada.
| | - Ma Luo
- Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada.
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, R3E 3R2, Canada.
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20
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Nomaguchi M, Doi N, Yoshida T, Koma T, Adachi S, Ode H, Iwatani Y, Yokoyama M, Sato H, Adachi A. Production of HIV-1 vif mRNA Is Modulated by Natural Nucleotide Variations and SLSA1 RNA Structure in SA1D2prox Genomic Region. Front Microbiol 2017; 8:2542. [PMID: 29326677 PMCID: PMC5741601 DOI: 10.3389/fmicb.2017.02542] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/07/2017] [Indexed: 12/11/2022] Open
Abstract
Genomic RNA of HIV-1 contains localized structures critical for viral replication. Its structural analysis has demonstrated a stem-loop structure, SLSA1, in a nearby region of HIV-1 genomic splicing acceptor 1 (SA1). We have previously shown that the expression level of vif mRNA is considerably altered by some natural single-nucleotide variations (nSNVs) clustering in SLSA1 structure. In this study, besides eleven nSNVs previously identified by us, we totally found nine new nSNVs in the SLSA1-containing sequence from SA1, splicing donor 2, and through to the start codon of Vif that significantly affect the vif mRNA level, and designated the sequence SA1D2prox (142 nucleotides for HIV-1 NL4-3). We then examined by extensive variant and mutagenesis analyses how SA1D2prox sequence and SLSA1 secondary structure are related to vif mRNA level. While the secondary structure and stability of SLSA1 was largely changed by nSNVs and artificial mutations introduced to restore the original NL4-3 form from altered ones by nSNVs, no clear association of the two SLSA1 properties with vif mRNA level was observed. In contrast, when naturally occurring SA1D2prox sequences that contain multiple nSNVs were examined, we attained significant inverse correlation between the vif level and SLSA1 stability. These results may suggest that SA1D2prox sequence adapts over time, and also that the altered SA1D2prox sequence, SLSA1 stability, and vif level are mutually related. In total, we show here that the entire SA1D2prox sequence and SLSA1 stability critically contribute to the modulation of vif mRNA level.
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Affiliation(s)
- Masako Nomaguchi
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
| | - Naoya Doi
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
| | - Tomoya Yoshida
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
| | - Takaaki Koma
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
| | - Shun Adachi
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
| | - Hirotaka Ode
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Yasumasa Iwatani
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Masaru Yokoyama
- Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Hironori Sato
- Laboratory of Viral Genomics, Pathogen Genomics Center, National Institute of Infectious Diseases, Tokyo, Japan
| | - Akio Adachi
- Department of Microbiology, Graduate School of Medical Science, Tokushima University, Tokushima, Japan
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21
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Boeras I, Seufzer B, Brady S, Rendahl A, Heng X, Boris-Lawrie K. The basal translation rate of authentic HIV-1 RNA is regulated by 5'UTR nt-pairings at junction of R and U5. Sci Rep 2017; 7:6902. [PMID: 28761163 PMCID: PMC5537239 DOI: 10.1038/s41598-017-06883-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 06/19/2017] [Indexed: 11/25/2022] Open
Abstract
The paradigm protein synthesis rate is regulated by structural complexity of the 5′untranslated region (UTR) derives from bacterial and other riboswitches. In-solution, HIV-1 5′UTR forms two interchangeable long-range nucleotide (nt) -pairings, one sequesters the gag start codon promoting dimerization while the other sequesters the dimer initiation signal preventing dimerization. While the effect of these nt-pairings on dimerization and packaging has been documented their effect on authentic HIV translation in cellulo has remained elusive until now. HIVNL4-3 5′UTR substitutions were designed to individually stabilize the dimer-prone or monomer-prone conformations, validated in-solution, and introduced to molecular clones. The effect of 5′UTR conformation on ribosome loading to HIV unspliced RNA and rate of Gag polypeptide synthesis was quantified in cellulo. Monomer- and dimer-prone 5′UTRs displayed equivalent, basal rate of translation. Gain-of-function substitution U103, in conjunction with previously defined nt-pairings that reorient AUG to flexible nt-pairing, significantly activated the translation rate, indicating the basal translation rate is under positive selection. The observed translation up-mutation focuses attention to nt-pairings at the junction of R and U5, a poorly characterized structure upstream of the characterized HIV riboswitch and demonstrates the basal translation rate of authentic HIV RNA is regulated independently of monomer:dimer equilibrium of the 5′UTR.
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Affiliation(s)
- I Boeras
- University of Minnesota, Department of Veterinary and Biomedical Sciences, 1971 Commonwealth, Saint Paul, MN, 55108, USA
| | - B Seufzer
- University of Minnesota, Department of Veterinary and Biomedical Sciences, 1971 Commonwealth, Saint Paul, MN, 55108, USA
| | - S Brady
- University of Missouri, Department of Biochemistry, 503 S. College Ave, Columbia, MO, 65211, USA
| | - A Rendahl
- University of Minnesota, Department of Veterinary and Biomedical Sciences, 1971 Commonwealth, Saint Paul, MN, 55108, USA
| | - X Heng
- University of Missouri, Department of Biochemistry, 503 S. College Ave, Columbia, MO, 65211, USA.
| | - K Boris-Lawrie
- University of Minnesota, Department of Veterinary and Biomedical Sciences, 1971 Commonwealth, Saint Paul, MN, 55108, USA.
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22
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Analysis of Competing HIV-1 Splice Donor Sites Uncovers a Tight Cluster of Splicing Regulatory Elements within Exon 2/2b. J Virol 2017; 91:JVI.00389-17. [PMID: 28446664 DOI: 10.1128/jvi.00389-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022] Open
Abstract
The HIV-1 accessory protein Vif is essential for viral replication by counteracting the host restriction factor APOBEC3G (A3G), and balanced levels of both proteins are required for efficient viral replication. Noncoding exons 2/2b contain the Vif start codon between their alternatively used splice donors 2 and 2b (D2 and D2b). For vif mRNA, intron 1 must be removed while intron 2 must be retained. Thus, splice acceptor 1 (A1) must be activated by U1 snRNP binding to either D2 or D2b, while splicing at D2 or D2b must be prevented. Here, we unravel the complex interactions between previously known and novel components of the splicing regulatory network regulating HIV-1 exon 2/2b inclusion in viral mRNAs. In particular, using RNA pulldown experiments and mass spectrometry analysis, we found members of the heterogeneous nuclear ribonucleoparticle (hnRNP) A/B family binding to a novel splicing regulatory element (SRE), the exonic splicing silencer ESS2b, and the splicing regulatory proteins Tra2/SRSF10 binding to the nearby exonic splicing enhancer ESE2b. Using a minigene reporter, we performed bioinformatics HEXplorer-guided mutational analysis to narrow down SRE motifs affecting splice site selection between D2 and D2b. Eventually, the impacts of these SREs on the viral splicing pattern and protein expression were exhaustively analyzed in viral particle production and replication experiments. Masking of these protein binding sites by use of locked nucleic acids (LNAs) impaired Vif expression and viral replication.IMPORTANCE Based on our results, we propose a model in which a dense network of SREs regulates vif mRNA and protein expression, crucial to maintain viral replication within host cells with varying A3G levels and at different stages of infection. This regulation is maintained by several serine/arginine-rich splicing factors (SRSF) and hnRNPs binding to those elements. Targeting this cluster of SREs with LNAs may lead to the development of novel effective therapeutic strategies.
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Keane SC, Summers MF. NMR Studies of the Structure and Function of the HIV-1 5'-Leader. Viruses 2016; 8:v8120338. [PMID: 28009832 PMCID: PMC5192399 DOI: 10.3390/v8120338] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/15/2016] [Accepted: 12/16/2016] [Indexed: 12/25/2022] Open
Abstract
The 5′-leader of the human immunodeficiency virus type 1 (HIV-1) genome plays several critical roles during viral replication, including differentially establishing mRNA versus genomic RNA (gRNA) fates. As observed for proteins, the function of the RNA is tightly regulated by its structure, and a common paradigm has been that genome function is temporally modulated by structural changes in the 5′-leader. Over the past 30 years, combinations of nucleotide reactivity mapping experiments with biochemistry, mutagenesis, and phylogenetic studies have provided clues regarding the secondary structures of stretches of residues within the leader that adopt functionally discrete domains. More recently, nuclear magnetic resonance (NMR) spectroscopy approaches have been developed that enable direct detection of intra- and inter-molecular interactions within the intact leader, providing detailed insights into the structural determinants and mechanisms that regulate HIV-1 genome packaging and function.
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Affiliation(s)
- Sarah C Keane
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
| | - Michael F Summers
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
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Transcriptional start site heterogeneity modulates the structure and function of the HIV-1 genome. Proc Natl Acad Sci U S A 2016; 113:13378-13383. [PMID: 27834211 DOI: 10.1073/pnas.1616627113] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The promoter in HIV type 1 (HIV-1) proviral DNA contains three sequential guanosines at the U3-R boundary that have been proposed to function as sites for transcription initiation. Here we show that all three sites are used in cells infected with HIV-1 and that viral RNAs containing a single 5' capped guanosine (Cap1G) are specifically selected for packaging in virions, consistent with a recent report [Masuda et al. (2015) Sci Rep 5:17680]. In addition, we now show that transcripts that begin with two or three capped guanosines (Cap2G or Cap3G) are enriched on polysomes, indicating that RNAs synthesized from different transcription start sites have different functions in viral replication. Because genomes are selected for packaging as dimers, we examined the in vitro monomer-dimer equilibrium properties of Cap1G, Cap2G, and Cap3G 5'-leader RNAs in the NL4-3 strain of HIV-1. Strikingly, under physiological-like ionic conditions in which the Cap1G 5'-leader RNA adopts a dimeric structure, the Cap2G and Cap3G 5'-leader RNAs exist predominantly as monomers. Mutagenesis studies designed to probe for base-pairing interactions suggest that the additional guanosines of the 2G and 3G RNAs remodel the base of the PolyA hairpin, resulting in enhanced sequestration of dimer-promoting residues and stabilization of the monomer. Our studies suggest a mechanism through which the structure, function, and fate of the viral genome can be modulated by the transcriptionally controlled presence or absence of a single 5' guanosine.
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NMR detection of intermolecular interaction sites in the dimeric 5'-leader of the HIV-1 genome. Proc Natl Acad Sci U S A 2016; 113:13033-13038. [PMID: 27791166 DOI: 10.1073/pnas.1614785113] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
HIV type-1 (HIV-1) contains a pseudodiploid RNA genome that is selected for packaging and maintained in virions as a noncovalently linked dimer. Genome dimerization is mediated by conserved elements within the 5'-leader of the RNA, including a palindromic dimer initiation signal (DIS) that has been proposed to form kissing hairpin and/or extended duplex intermolecular contacts. Here, we have applied a 2H-edited NMR approach to directly probe for intermolecular interactions in the full-length, dimeric HIV-1 5'-leader (688 nucleotides; 230 kDa). The interface is extensive and includes DIS:DIS base pairing in an extended duplex state as well as intermolecular pairing between elements of the upstream Unique-5' (U5) sequence and those near the gag start site (AUG). Other pseudopalindromic regions of the leader, including the transcription activation (TAR), polyadenylation (PolyA), and primer binding (PBS) elements, do not participate in intermolecular base pairing. Using a 2H-edited one-dimensional NMR approach, we also show that the extended interface structure forms on a time scale similar to that of overall RNA dimerization. Our studies indicate that a kissing dimer-mediated structure, if formed, exists only transiently and readily converts to the extended interface structure, even in the absence of the HIV-1 nucleocapsid protein or other RNA chaperones.
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26
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Gotic I, Omidi S, Fleury-Olela F, Molina N, Naef F, Schibler U. Temperature regulates splicing efficiency of the cold-inducible RNA-binding protein gene Cirbp. Genes Dev 2016; 30:2005-17. [PMID: 27633015 PMCID: PMC5066242 DOI: 10.1101/gad.287094.116] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 08/19/2016] [Indexed: 12/28/2022]
Abstract
Gotic et al. show that the temperature-dependent accumulation of cold-inducible RNA-binding protein (Cirbp) mRNA is controlled primarily by the regulation of splicing efficiency. As revealed by genome-wide “approach-to-steady-state” kinetics, this post-transcriptional mechanism is widespread in the temperature-dependent control of gene expression. In mammals, body temperature fluctuates diurnally around a mean value of 36°C–37°C. Despite the small differences between minimal and maximal values, body temperature rhythms can drive robust cycles in gene expression in cultured cells and, likely, animals. Here we studied the mechanisms responsible for the temperature-dependent expression of cold-inducible RNA-binding protein (CIRBP). In NIH3T3 fibroblasts exposed to simulated mouse body temperature cycles, Cirbp mRNA oscillates about threefold in abundance, as it does in mouse livers. This daily mRNA accumulation cycle is directly controlled by temperature oscillations and does not depend on the cells’ circadian clocks. Here we show that the temperature-dependent accumulation of Cirbp mRNA is controlled primarily by the regulation of splicing efficiency, defined as the fraction of Cirbp pre-mRNA processed into mature mRNA. As revealed by genome-wide “approach to steady-state” kinetics, this post-transcriptional mechanism is widespread in the temperature-dependent control of gene expression.
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Affiliation(s)
- Ivana Gotic
- Department of Molecular Biology, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - Saeed Omidi
- The Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Fabienne Fleury-Olela
- Department of Molecular Biology, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - Nacho Molina
- The Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Felix Naef
- The Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Ueli Schibler
- Department of Molecular Biology, University of Geneva, CH-1211 Geneva 4, Switzerland
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A Phylogenetic Survey on the Structure of the HIV-1 Leader RNA Domain That Encodes the Splice Donor Signal. Viruses 2016; 8:v8070200. [PMID: 27455303 PMCID: PMC4974535 DOI: 10.3390/v8070200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/29/2016] [Accepted: 07/01/2016] [Indexed: 11/16/2022] Open
Abstract
RNA splicing is a critical step in the human immunodeficiency virus type 1 (HIV-1) replication cycle because it controls the expression of the complex viral proteome. The major 5′ splice site (5′ss) that is positioned in the untranslated leader of the HIV-1 RNA transcript is of particular interest because it is used for the production of the more than 40 differentially spliced subgenomic mRNAs. HIV-1 splicing needs to be balanced tightly to ensure the proper levels of all viral proteins, including the Gag-Pol proteins that are translated from the unspliced RNA. We previously presented evidence that the major 5′ss is regulated by a repressive local RNA structure, the splice donor (SD) hairpin, that masks the 11 nucleotides (nts) of the 5′ss signal for recognition by U1 small nuclear RNA (snRNA) of the spliceosome machinery. A strikingly different multiple-hairpin RNA conformation was recently proposed for this part of the HIV-1 leader RNA. We therefore inspected the sequence of natural HIV-1 isolates in search for support, in the form of base pair (bp) co-variations, for the different RNA conformations.
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Vega Y, Delgado E, de la Barrera J, Carrera C, Zaballos Á, Cuesta I, Mariño A, Ocampo A, Miralles C, Pérez-Castro S, Álvarez H, López-Miragaya I, García-Bodas E, Díez-Fuertes F, Thomson MM. Sequence Analysis of In Vivo-Expressed HIV-1 Spliced RNAs Reveals the Usage of New and Unusual Splice Sites by Viruses of Different Subtypes. PLoS One 2016; 11:e0158525. [PMID: 27355361 PMCID: PMC4927154 DOI: 10.1371/journal.pone.0158525] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 06/16/2016] [Indexed: 11/18/2022] Open
Abstract
HIV-1 RNAs are generated through a complex splicing mechanism, resulting in a great diversity of transcripts, which are classified in three major categories: unspliced, singly spliced (SS), and doubly spliced (DS). Knowledge on HIV-1 RNA splicing in vivo and by non-subtype B viruses is scarce. Here we analyze HIV-1 RNA splice site usage in CD4+CD25+ lymphocytes from HIV-1-infected individuals through pyrosequencing. HIV-1 DS and SS RNAs were amplified by RT-PCR in 19 and 12 samples, respectively. 13,108 sequences from HIV-1 spliced RNAs, derived from viruses of five subtypes (A, B, C, F, G), were identified. In four samples, three of non-B subtypes, five 3' splice sites (3'ss) mapping to unreported positions in the HIV-1 genome were identified. Two, designated A4i and A4j, were used in 22% and 25% of rev RNAs in two viruses of subtypes B and A, respectively. Given their close proximity (one or two nucleotides) to A4c and A4d, respectively, they could be viewed as variants of these sites. Three 3'ss, designated A7g, A7h, and A7i, located 20, 32, and 18 nucleotides downstream of A7, respectively, were identified in a subtype C (A7g, A7h) and a subtype G (A7i) viruses, each in around 2% of nef RNAs. The new splice sites or variants of splice sites were associated with the usual sequence features of 3'ss. Usage of unusual 3'ss A4d, A4e, A5a, A7a, and A7b was also detected. A4f, previously identified in two subtype C viruses, was preferentially used by rev RNAs of a subtype C virus. These results highlight the great diversity of in vivo splice site usage by HIV-1 RNAs. The fact that four of five newly identified splice sites or variants of splice sites were detected in non-subtype B viruses allows anticipating an even greater diversity of HIV-1 splice site usage than currently known.
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Affiliation(s)
- Yolanda Vega
- HIV Biology and Variability Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Elena Delgado
- HIV Biology and Variability Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Jorge de la Barrera
- Bioinformatics Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Cristina Carrera
- HIV Biology and Variability Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Ángel Zaballos
- Genomics Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Isabel Cuesta
- Bioinformatics Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Ana Mariño
- Hospital Arquitecto Marcide. Ferrol, A Coruña, Spain
| | - Antonio Ocampo
- Complejo Hospitalario Universitario de Vigo. Vigo, Pontevedra, Spain
| | - Celia Miralles
- Complejo Hospitalario Universitario de Vigo. Vigo, Pontevedra, Spain
| | | | | | | | - Elena García-Bodas
- HIV Biology and Variability Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Francisco Díez-Fuertes
- AIDS Immunopathogenesis Unit. Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
| | - Michael M. Thomson
- HIV Biology and Variability Unit, Centro Nacional de Microbiología, Instituto de Salud Carlos III. Majadahonda, Madrid, Spain
- * E-mail:
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Mueller N, Klaver B, Berkhout B, Das AT. Human immunodeficiency virus type 1 splicing at the major splice donor site is controlled by highly conserved RNA sequence and structural elements. J Gen Virol 2016; 96:3389-3395. [PMID: 26385834 DOI: 10.1099/jgv.0.000288] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) splicing has to be strictly controlled to ensure the balanced production of the unspliced and all differently spliced viral RNAs. Splicing at the major 59 splice site (59ss) that is used for the synthesis of all spliced RNAs is modulated by the local RNA structure and binding of regulatory SR proteins. Here, we demonstrate that the suboptimal sequence complementarity between this 59ss and U1 small nuclear RNA (snRNA) also contributes to prevent excessive splicing. Analysis of a large set of HIV-1 sequences revealed that all three regulatory features of the 59ss region (RNA structure, SR protein binding and sequence complementarity with U1 snRNA) are highly conserved amongst virus isolates, which supports their importance. Combined mutations that destabilize the local RNA structure, remove binding sites for inhibitory SR proteins and optimize the U1 snRNA complementarity resulted in almost complete splicing and accordingly reduced virus replication.
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Affiliation(s)
- Nancy Mueller
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Bep Klaver
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Atze T Das
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Natural Single-Nucleotide Variations in the HIV-1 Genomic SA1prox Region Can Alter Viral Replication Ability by Regulating Vif Expression Levels. J Virol 2016; 90:4563-4578. [PMID: 26912631 DOI: 10.1128/jvi.02939-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 02/15/2016] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED We previously found that natural single-nucleotide variations located within a proximal region of splicing acceptor 1 (SA1prox) in the HIV-1 genome could alter the viral replication potential and mRNA expression pattern, especially the vif mRNA level. Here, we studied the virological and molecular basis of nucleotide sequence variations in SA1prox for alterations of viral replication ability. Consistent with our previous findings, variant clones indeed expressed Vif at different levels and grew distinctively in cells with various APOBEC3G expression levels. Similar effects were observed for natural variations found in HIV-2 SA1prox, suggesting the importance of the SA1prox sequence. To define nucleotides critical for the regulation of HIV-1 Vif expression, effects of natural SA1prox variations newly found in the HIV Sequence Compendium database on vif mRNA/Vif protein levels were examined. Seven out of nine variations were found to produce Vif at lower, higher, or more excessive levels than wild-type NL4-3. Combination experiments of variations giving distinct Vif levels suggested that the variations mutually affected vif transcript production. While low and high producers of Vif grew in an APOBEC3G-dependent manner, excessive expressers always showed an impeded growth phenotype due to defects in single-cycle infectivity and/or virion production levels. The phenotype of excessive expressers was not due primarily to inadequate expression of Tat or Rev, although SA1prox variations altered the overall HIV-1 mRNA expression pattern. Collectively, our results demonstrate that HIV SA1prox regulates Vif expression levels and suggest a relationship between SA1prox and viral adaptation/evolution given that variations occurred naturally. IMPORTANCE While human cells possess restriction factors to inhibit HIV-1 replication, HIV-1 encodes antagonists to overcome these barriers. Conflicts between host restriction factors and viral counterparts are critical driving forces behind mutual evolution. The interplay of cellular APOBEC3G and viral Vif proteins is a typical example. Here, we demonstrate that naturally occurring single-nucleotide variations in the proximal region of splicing acceptor 1 (SA1prox) of the HIV-1 genome frequently alter Vif expression levels, thereby modulating viral replication potential in cells with various ABOBEC3G levels. The results of the present study reveal a previously unidentified and important way for HIV-1 to compete with APOBEC3G restriction by regulating its Vif expression levels. We propose that SA1prox plays a regulatory role in Vif counteraction against APOBEC3G in order to contribute to HIV-1 replication and evolution, and this may be applicable to other primate lentiviruses.
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31
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HIV-1 RNAs: sense and antisense, large mRNAs and small siRNAs and miRNAs. Curr Opin HIV AIDS 2015; 10:103-9. [PMID: 25565176 DOI: 10.1097/coh.0000000000000135] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW This review summarizes recent findings concerning the ever-growing HIV-1 RNA population. RECENT FINDINGS The retrovirus HIV-1 has an RNA genome that is converted into DNA and is integrated into the genome of the infected host cell. Transcription from the long terminal repeat-encoded promoter results in the production of a full-length genomic RNA and multiple spliced mRNAs. Recent experiments, mainly based on next-generation sequencing, provided evidence for several additional HIV-encoded RNAs, including antisense RNAs and virus-encoded microRNAs. SUMMARY We will survey recent findings related to HIV-1 RNA biosynthesis, especially regulatory mechanisms that control initiation of transcription, capping and polyadenylation. We zoom in on the diversity of HIV-1 derived RNA transcripts, their mode of synthesis and proposed functions in the infected cell. Special attention is paid to the viral transacting responsive RNA hairpin motif that has been suggested to encode microRNAs.
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Meng B, Ip NCY, Prestwood LJ, Abbink TEM, Lever AML. Evidence that the endosomal sorting complex required for transport-II (ESCRT-II) is required for efficient human immunodeficiency virus-1 (HIV-1) production. Retrovirology 2015; 12:72. [PMID: 26268989 PMCID: PMC4535389 DOI: 10.1186/s12977-015-0197-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/31/2015] [Indexed: 11/17/2022] Open
Abstract
Background Egress of a number of different virus species from infected cells depends on proteins of the endosomal sorting complexes required for transport (ESCRT) pathway. HIV has also hijacked this system to bud viruses outward from the cell surface. How ESCRT-I activates ESCRT-III in this process remains unclear with conflicting published evidence for the requirement of ESCRT-II which fulfils this role in other systems. We investigated the role of ESCRT-II using knockdown mediated by siRNA and shRNA, mutants which prevent ESCRT-I/ESCRT-II interaction and a CRISPR/Cas9 EAP45 knockout cell line. Results Depletion or elimination of ESCRT-II components from an HIV infected cell produces two distinct effects. The overall production of HIV-1 Gag is reduced leading to a diminished amount of intracellular virion protein. In addition depletion of ESCRT-II produces an effect similar to that seen when ESCRT-I and -III components are depleted, that of a delayed Gag p26 to p24 +p2 cleavage associated with a reduction in export of virion particles and a visible reduction in budding efficiency in virus producing cells. Mutants that interfere with ESCRT-I interacting with ESCRT-II similarly reduce virus export. The export defect is independent of the decrease in overall Gag production. Using a mutant virus which cannot use the ALIX mediated export pathway exacerbates the decrease in virus export seen when ESCRT-II is depleted. ESCRT-II knockdown does not lead to complete elimination of virus release suggesting that the late domain role of ESCRT-II is required for optimal efficiency of viral budding but that there are additional pathways that the virus can employ to facilitate this. Conclusion ESCRT-II contributes to efficient HIV virion production and export by more than one pathway; both by a transcriptional or post transcriptional mechanism and also by facilitating efficient virus export from the cell through interactions with other ESCRT components. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0197-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Bo Meng
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
| | - Natasha C Y Ip
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
| | - Liam J Prestwood
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
| | - Truus E M Abbink
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK. .,Centre for Childhood White Matter Disorders, VU University Medical Centre, Amsterdam, The Netherlands.
| | - Andrew M L Lever
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
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Le Grice SFJ. Targeting the HIV RNA genome: high-hanging fruit only needs a longer ladder. Curr Top Microbiol Immunol 2015; 389:147-69. [PMID: 25735922 PMCID: PMC7120518 DOI: 10.1007/82_2015_434] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
Small molecules targeting the enzymes responsible for human immunodeficiency virus (HIV) maturation, DNA synthesis and its subsequent chromosomal integration as ribonucleotide-free double-stranded DNA remain the mainstay of combination antiretroviral therapy. For infected individuals harboring drug-susceptible virus, this approach has afforded complete or near-complete viral suppression. However, in the absence of a curative strategy, the predictable emergence of drug-resistant variants requires continued development of improved antiviral strategies, inherent to which is the necessity of identifying novel targets. Regulatory elements that mediate transcription, translation, nucleocytoplasmic transport, dimerization, packaging and reverse transcription of the (+) strand RNA genome should now be considered viable targets for small molecule, peptide- and oligonucleotide-based therapeutics. Where target specificity and cellular penetration and toxicity have been the primary obstacle to successful “macromolecule therapeutics”, this chapter summarizes (a) novel approaches targeting RNA motifs whose three-dimensional structure is critical for biological function and consequently may be less prone to resistance-conferring mutations and (b) improved methods for delivery.
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Affiliation(s)
- Stuart F J Le Grice
- RT Biochemistry Section, Basic Research Laboratory, National Cancer Institute, Frederick, MD, 21702, USA,
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34
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Keane SC, Heng X, Lu K, Kharytonchyk S, Ramakrishnan V, Carter G, Barton S, Hosic A, Florwick A, Santos J, Bolden NC, McCowin S, Case DA, Johnson BA, Salemi M, Telesnitsky A, Summers MF. RNA structure. Structure of the HIV-1 RNA packaging signal. Science 2015; 348:917-21. [PMID: 25999508 PMCID: PMC4492308 DOI: 10.1126/science.aaa9266] [Citation(s) in RCA: 202] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The 5' leader of the HIV-1 genome contains conserved elements that direct selective packaging of the unspliced, dimeric viral RNA into assembling particles. By using a (2)H-edited nuclear magnetic resonance (NMR) approach, we determined the structure of a 155-nucleotide region of the leader that is independently capable of directing packaging (core encapsidation signal; Ψ(CES)). The RNA adopts an unexpected tandem three-way junction structure, in which residues of the major splice donor and translation initiation sites are sequestered by long-range base pairing and guanosines essential for both packaging and high-affinity binding to the cognate Gag protein are exposed in helical junctions. The structure reveals how translation is attenuated, Gag binding promoted, and unspliced dimeric genomes selected, by the RNA conformer that directs packaging.
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Affiliation(s)
- Sarah C Keane
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Xiao Heng
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Kun Lu
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Siarhei Kharytonchyk
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-5620, USA
| | - Venkateswaran Ramakrishnan
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Gregory Carter
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Shawn Barton
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Azra Hosic
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Alyssa Florwick
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Justin Santos
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Nicholas C Bolden
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - Sayo McCowin
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA
| | - David A Case
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA
| | - Bruce A Johnson
- One Moon Scientific, Incorporated, 839 Grant Avenue, Westfield, NJ 07090, USA, and City University of New York (CUNY) Advanced Science Research Center, 85 St. Nicholas Terrace, New York, NY 10031, USA
| | - Marco Salemi
- Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, and Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
| | - Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-5620, USA.
| | - Michael F Summers
- Howard Hughes Medical Institute (HHMI) and Department of Chemistry and Biochemistry, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA.
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Abstract
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Influenza A is an RNA virus with
a genome of eight negative sense
segments. Segment 7 mRNA contains a 3′ splice site for alternative
splicing to encode the essential M2 protein. On the basis of sequence
alignment and chemical mapping experiments, the secondary structure
surrounding the 3′ splice site has an internal loop, adenine
bulge, and hairpin loop when it is in the hairpin conformation that
exposes the 3′ splice site. We report structural features of
a three-dimensional model of the hairpin derived from nuclear magnetic
resonance spectra and simulated annealing with restrained molecular
dynamics. Additional insight was provided by modeling based on 1H chemical shifts. The internal loop containing the 3′
splice site has a dynamic guanosine and a stable imino (cis Watson–Crick/Watson–Crick) GA pair. The adenine bulge
also appears to be dynamic with the A either stacked in the stem or
forming a base triple with a Watson–Crick GC pair. The hairpin
loop is a GAAA tetraloop closed by an AC pair.
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Affiliation(s)
- Jonathan L Chen
- †Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Scott D Kennedy
- ‡Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, United States
| | - Douglas H Turner
- †Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.,§Center for RNA Biology, University of Rochester, Rochester, New York 14627, United States
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Mueller N, Berkhout B, Das AT. HIV-1 splicing is controlled by local RNA structure and binding of splicing regulatory proteins at the major 5' splice site. J Gen Virol 2015; 96:1906-17. [PMID: 25779589 DOI: 10.1099/vir.0.000122] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The 5' leader region of the human immunodeficiency virus 1 (HIV-1) RNA genome contains the major 5' splice site (ss) that is used in the production of the many spliced viral RNAs. This splice-donor (SD) region can fold into a stable stem-loop structure and the thermodynamic stability of this RNA hairpin influences splicing efficiency. In addition, splicing may be modulated by binding of splicing regulatory (SR) proteins, in particular SF2/ASF (SRSF1), SC35 (SRSF2), SRp40 (SRSF5) and SRp55 (SRSF6), to sequence elements in the SD region. The role of RNA structure and SR protein binding in splicing control was previously studied by functional analysis of mutant SD sequences. The interpretation of these studies was complicated by the fact that most mutations simultaneously affect both structure and sequence elements. We therefore tried to disentangle the contribution of these two variables by designing more precise SD region mutants with a single effect on either the sequence or the structure. The current analysis indicates that HIV-1 splicing at the major 5'ss is modulated by both the stability of the local RNA structure and the binding of splicing regulatory proteins.
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Affiliation(s)
- Nancy Mueller
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands
| | - Atze T Das
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands
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Machinaga A, Takase-Yoden S. A 38 nt region and its flanking sequences within gag of Friend murine leukemia virus are crucial for splicing at the correct 5' and 3' splice sites. Microbiol Immunol 2014; 58:38-50. [PMID: 24236664 DOI: 10.1111/1348-0421.12114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 10/25/2013] [Accepted: 11/12/2013] [Indexed: 11/27/2022]
Abstract
The genome of the Friend murine leukemia virus (Fr-MLV) contains a 5' splice site (5'ss) located at 205 nt and a 3'ss located at 5489 nt. In our previous studies, it was shown that if the HindIII-BglII (879-1904 bp) fragment within gag is deleted from the proA8m1 vector, which carries the entire Fr-MLV sequence, then cryptic splicing of env-mRNA occurs. Here, attempts were made to identify the genomic segment(s) in this region that is/are essential to correct splicing. First, vectors with a serially truncated HindIII-BglII fragment were constructed. The vector, in which a 38 bp fragment (1612-1649 bp) is deleted or reversed in proA8m1, only produced splice variants. It was found that a 38 nt region within gag contains important elements that positively regulate splicing at the correct splice sites. Further analyses of a series of vectors carrying the 38 bp fragment and its flanking sequences showed that a region (1183-1611 nt) upstream of the 38 nt fragment also contains sequences that positively or negatively influence splicing at the correct splice sites. The SphI-NdeI (5140-5400 bp) fragment just upstream of the 3'ss was deleted from vectors that carried the 38 bp fragment and its flanking sequences, which yielded correctly spliced mRNA; interestingly, these deleted vectors showed cryptic splicing. These findings suggest that the 5140-5400 nt region located just upstream of the 3'ss is required for the splicing function of the 38 nt fragment and its flanking sequences.
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Affiliation(s)
- Akihito Machinaga
- Department of Bioinformatics, Faculty of Engineering, Soka University, 1-236, Tangi-machi, Hachioji, Tokyo, 192-8577, Japan
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Cantara WA, Olson ED, Musier-Forsyth K. Progress and outlook in structural biology of large viral RNAs. Virus Res 2014; 193:24-38. [PMID: 24956407 PMCID: PMC4252365 DOI: 10.1016/j.virusres.2014.06.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 02/05/2023]
Abstract
The field of viral molecular biology has reached a precipice for which pioneering studies on the structure of viral RNAs are beginning to bridge the gap. It has become clear that viral genomic RNAs are not simply carriers of hereditary information, but rather are active players in many critical stages during replication. Indeed, functions such as cap-independent translation initiation mechanisms are, in some cases, primarily driven by RNA structural determinants. Other stages including reverse transcription initiation in retroviruses, nuclear export and viral packaging are specifically dependent on the proper 3-dimensional folding of multiple RNA domains to recruit necessary viral and host factors required for activity. Furthermore, a large-scale conformational change within the 5'-untranslated region of HIV-1 has been proposed to regulate the temporal switch between viral protein synthesis and packaging. These RNA-dependent functions are necessary for replication of many human disease-causing viruses such as severe acute respiratory syndrome (SARS)-associated coronavirus, West Nile virus, and HIV-1. The potential for antiviral development is currently hindered by a poor understanding of RNA-driven molecular mechanisms, resulting from a lack of structural information on large RNAs and ribonucleoprotein complexes. Herein, we describe the recent progress that has been made on characterizing these large RNAs and provide brief descriptions of the techniques that will be at the forefront of future advances. Ongoing and future work will contribute to a more complete understanding of the lifecycles of retroviruses and RNA viruses and potentially lead to novel antiviral strategies.
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Affiliation(s)
| | | | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, Center for Retrovirus Research, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, United States
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39
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Mueller N, van Bel N, Berkhout B, Das AT. HIV-1 splicing at the major splice donor site is restricted by RNA structure. Virology 2014; 468-470:609-620. [PMID: 25305540 DOI: 10.1016/j.virol.2014.09.018] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/11/2014] [Accepted: 09/19/2014] [Indexed: 11/29/2022]
Abstract
The 5' leader region of the HIV-1 RNA contains the major 5' splice site (ss) that is used in the production of all spliced viral RNAs. This splice-donor (SD) region can fold a stem-loop structure. We demonstrate that whereas stabilization of this SD hairpin reduces splicing efficiency, destabilization increases splicing. Both stabilization and destabilization reduce viral fitness. These results demonstrate that the stability of the SD hairpin can modulate the level of splicing, most likely by controlling the accessibility of the 5'ss for the splicing machinery. The natural stability of the SD hairpin restricts splicing and this stability seems to be fine-tuned to reach the optimal balance between unspliced and spliced RNAs for efficient virus replication. The 5'ss region of different HIV-1 isolates and the related SIVmac239 can fold a similar structure. This evolutionary conservation supports the importance of this structure in viral replication.
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Affiliation(s)
- Nancy Mueller
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands.
| | - Nikki van Bel
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands.
| | - Ben Berkhout
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands.
| | - Atze T Das
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, The Netherlands.
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40
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Assis R. Strong epistatic selection on the RNA secondary structure of HIV. PLoS Pathog 2014; 10:e1004363. [PMID: 25210786 PMCID: PMC4161434 DOI: 10.1371/journal.ppat.1004363] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/29/2014] [Indexed: 11/23/2022] Open
Abstract
A key question in evolutionary genomics is how populations navigate the adaptive landscape in the presence of epistasis, or interactions among loci. This problem can be directly addressed by studying the evolution of RNA secondary structures, for which there is constraint to maintain pairing between Watson-Crick (WC) sites. Replacement of a nucleotide at one site of a WC pair reduces fitness by disrupting binding, which can be restored via a compensatory replacement at the interacting site. Here, I present the first genome-scale analysis of epistasis on the RNA secondary structure of human immunodeficiency virus type 1 (HIV-1). Comparison of polymorphism frequencies at ancestrally conserved sites reveals that selection against replacements is ∼2.7 times stronger at WC than at non-WC sites, such that nearly 50% of constraint can be attributed to epistasis. However, almost all epistatic constraint is due to selection against conversions of WC pairs to unpaired (UP) nucleotides, whereas conversions to GU wobbles are only slightly deleterious. This disparity is also evident in pairs with second-site compensatory replacements; conversions from UP nucleotides to WC pairs increase median fitness by ∼4.2%, whereas conversions from GU wobbles to WC pairs only increase median fitness by ∼0.3%. Moreover, second-site replacements that convert UP nucleotides to GU wobbles also increase median fitness by ∼4%, indicating that such replacements are nearly as compensatory as those that restore WC pairing. Thus, WC peaks of the HIV-1 epistatic adaptive landscape are connected by high GU ridges, enabling the viral population to rapidly explore distant peaks without traversing deep UP valleys. Epistasis is an evolutionary process in which the effect of a nucleotide at one site in the genome is dependent on the presence or absence of particular nucleotides at other sites in the genome. One of the simplest types of epistasis occurs between Watson-Crick (WC) nucleotides in RNA secondary structures, which are under constraint to maintain base-pairing. In this study, I examine the effects of mutations at WC sites in the RNA secondary structure of HIV-1. I show that while epistasis plays a major role in the evolution of the HIV-1 secondary structure, different types of mutations have variable effects on fitness. Therefore, by favoring certain mutational trajectories, HIV-1 can evolve rapidly despite strong epistatic constraint on its RNA secondary structure.
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Affiliation(s)
- Raquel Assis
- Department of Biology, Huck Institutes of the Life Sciences, Center for Medical Genomics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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41
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Jiang T, Kennedy SD, Moss WN, Kierzek E, Turner DH. Secondary structure of a conserved domain in an intron of influenza A M1 mRNA. Biochemistry 2014; 53:5236-48. [PMID: 25026548 PMCID: PMC4139153 DOI: 10.1021/bi500611j] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Influenza A virus utilizes RNA throughout infection. Little is known, however, about the roles of RNA structures. A previous bioinformatics survey predicted multiple regions of influenza A virus that are likely to generate evolutionarily conserved and stable RNA structures. One predicted conserved structure is in the pre-mRNA coding for essential proteins, M1 and M2. This structure starts 79 nucleotides downstream of the M2 mRNA 5' splice site. Here, a combination of biochemical structural mapping, mutagenesis, and NMR confirms the predicted three-way multibranch structure of this RNA. Imino proton NMR spectra reveal no change in secondary structure when 80 mM KCl is supplemented with 4 mM MgCl2. Optical melting curves in 1 M NaCl and in 100 mM KCl with 10 mM MgCl2 are very similar, with melting temperatures ∼14 °C higher than that for 100 mM KCl alone. These results provide a firm basis for designing experiments and potential therapeutics to test for function in cell culture.
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Affiliation(s)
- Tian Jiang
- Department of Chemistry and Center for RNA Biology, University of Rochester , Rochester, New York 14627, United States
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42
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Dela-Moss LI, Moss WN, Turner DH. Identification of conserved RNA secondary structures at influenza B and C splice sites reveals similarities and differences between influenza A, B, and C. BMC Res Notes 2014; 7:22. [PMID: 24405943 PMCID: PMC3895672 DOI: 10.1186/1756-0500-7-22] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 01/02/2014] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Influenza B and C are single-stranded RNA viruses that cause yearly epidemics and infections. Knowledge of RNA secondary structure generated by influenza B and C will be helpful in further understanding the role of RNA structure in the progression of influenza infection. FINDINGS All available protein-coding sequences for influenza B and C were analyzed for regions with high potential for functional RNA secondary structure. On the basis of conserved RNA secondary structure with predicted high thermodynamic stability, putative structures were identified that contain splice sites in segment 8 of influenza B and segments 6 and 7 of influenza C. The sequence in segment 6 also contains three unused AUG start codon sites that are sequestered within a hairpin structure. CONCLUSIONS When added to previous studies on influenza A, the results suggest that influenza splicing may share common structural strategies for regulation of splicing. In particular, influenza 3' splice sites are predicted to form secondary structures that can switch conformation to regulate splicing. Thus, these RNA structures present attractive targets for therapeutics aimed at targeting one or the other conformation.
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Affiliation(s)
- Lumbini I Dela-Moss
- Department of Chemistry and Center for RNA Biology, University of Rochester, Rochester, New York 14627-0216, USA
| | - Walter N Moss
- Department of Chemistry and Center for RNA Biology, University of Rochester, Rochester, New York 14627-0216, USA
| | - Douglas H Turner
- Department of Chemistry and Center for RNA Biology, University of Rochester, Rochester, New York 14627-0216, USA
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Abstract
The 5' untranslated leader region of the human immunodeficiency virus type 1 (HIV-1) RNA genome is a strongly conserved sequence that encodes several regulatory motifs important for viral replication. Most of these motifs are exposed as hairpin structures, including the dimerization initiation signal (DIS), the major splice donor site (SD), and the packaging signal (Ψ), which are connected by short single-stranded regions. Mutational analysis revealed many functions of these hairpins, but only a few studies have focused on the single-stranded purine-rich sequences. Using the in vivo SELEX (systematic evolution of ligands by exponential enrichment) approach, we probed the sequence space in these regions that is compatible with efficient HIV-1 replication and analyzed the impact on the RNA secondary structure of the leader RNA. Our results show a strong sequence requirement for the DIS hairpin flanking regions. We postulate that these sequences are important for the binding of specific protein factors that support leader RNA-mediated functions. The sequence between the SD and Ψ hairpins seems to have a less prominent role, despite the strong conservation of the stretch of 5 A residues in natural isolates. We hypothesize that this may reflect the subtle evolutionary pressure on HIV-1 to acquire an A-rich RNA genome. In silico analyses indicate that sequences are avoided in all 3 single-stranded domains that affect the local or overall leader RNA folding. IMPORTANCE Many regulatory RNA sequences are clustered in the untranslated leader domain of the HIV-1 RNA genome. Several RNA hairpin structures in this domain have been proposed to fulfill specific roles, e.g., mediating RNA dimer formation to facilitate HIV-1 recombination. We now focus on the importance of a few well-conserved single-stranded sequences that connect these hairpins. We created libraries of HIV-1 variants in which these segments were randomized and selected the best-replicating variants. For two segments we document the selection of the (nearly) wild-type sequence, thus demonstrating the importance of these primary nucleotide sequences and the power of the in vivo SELEX approach. However, for the third segment a large variety of sequences is compatible with efficient HIV-1 replication. Interestingly, the A-rich sequence of this segment is highly conserved among HIV-1 isolates, which likely reflects the evolutionary tendency of HIV-1 to adopt A-rich sequences.
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44
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Seif E, Niu M, Kleiman L. Annealing to sequences within the primer binding site loop promotes an HIV-1 RNA conformation favoring RNA dimerization and packaging. RNA (NEW YORK, N.Y.) 2013; 19:1384-1393. [PMID: 23960173 PMCID: PMC3854529 DOI: 10.1261/rna.038497.113] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 07/02/2013] [Indexed: 06/02/2023]
Abstract
The 5' untranslated region (5' UTR) of HIV-1 genomic RNA (gRNA) includes structural elements that regulate reverse transcription, transcription, translation, tRNA(Lys3) annealing to the gRNA, and gRNA dimerization and packaging into viruses. It has been reported that gRNA dimerization and packaging are regulated by changes in the conformation of the 5'-UTR RNA. In this study, we show that annealing of tRNA(Lys3) or a DNA oligomer complementary to sequences within the primer binding site (PBS) loop of the 5' UTR enhances its dimerization in vitro. Structural analysis of the 5'-UTR RNA using selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) shows that the annealing promotes a conformational change of the 5' UTR that has been previously reported to favor gRNA dimerization and packaging into virus. The model predicted by SHAPE analysis is supported by antisense experiments designed to test which annealed sequences will promote or inhibit gRNA dimerization. Based on reports showing that the gRNA dimerization favors its incorporation into viruses, we tested the ability of a mutant gRNA unable to anneal to tRNA(Lys3) to be incorporated into virions. We found a ∼60% decrease in mutant gRNA packaging compared with wild-type gRNA. Together, these data further support a model for viral assembly in which the initial annealing of tRNA(Lys3) to gRNA is cytoplasmic, which in turn aids in the promotion of gRNA dimerization and its incorporation into virions.
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Affiliation(s)
- Elias Seif
- Lady Davis Institute for Medical Research and McGill AIDS Centre, Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
| | - Meijuan Niu
- Lady Davis Institute for Medical Research and McGill AIDS Centre, Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
| | - Lawrence Kleiman
- Lady Davis Institute for Medical Research and McGill AIDS Centre, Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
- Department of Medicine, McGill University, Montreal, Quebec H3A 1A1, Canada
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45
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Wei B, Han L, Abbink TEM, Groppelli E, Lim D, Thaker YR, Gao W, Zhai R, Wang J, Lever A, Jolly C, Wang H, Rudd CE. Immune adaptor ADAP in T cells regulates HIV-1 transcription and cell-cell viral spread via different co-receptors. Retrovirology 2013; 10:101. [PMID: 24047317 PMCID: PMC3851709 DOI: 10.1186/1742-4690-10-101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/12/2013] [Indexed: 11/25/2022] Open
Abstract
Background Immune cell adaptor protein ADAP (adhesion and degranulation-promoting adaptor protein) mediates aspects of T-cell adhesion and proliferation. Despite this, a connection between ADAP and infection by the HIV-1 (human immunodeficiency virus-1) has not been explored. Results In this paper, we show for the first time that ADAP and its binding to SLP-76 (SH2 domain-containing leukocyte protein of 76 kDa) regulate HIV-1 infection via two distinct mechanisms and co-receptors. siRNA down-regulation of ADAP, or expression of a mutant that is defective in associating to its binding partner SLP-76 (termed M12), inhibited the propagation of HIV-1 in T-cell lines and primary human T-cells. In one step, ADAP and its binding to SLP-76 were needed for the activation of NF-κB and its transcription of the HIV-1 long terminal repeat (LTR) in cooperation with ligation of co-receptor CD28, but not LFA-1. In a second step, the ADAP-SLP-76 module cooperated with LFA-1 to regulate conjugate formation between T-cells and dendritic cells or other T-cells as well as the development of the virological synapse (VS) and viral spread between immune cells. Conclusions These findings indicate that ADAP regulates two steps of HIV-1 infection cooperatively with two distinct receptors, and as such, serves as a new potential target in the blockade of HIV-1 infection.
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Affiliation(s)
- Bin Wei
- The State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai China.
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46
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Sabarinathan R, Tafer H, Seemann SE, Hofacker IL, Stadler PF, Gorodkin J. RNAsnp: efficient detection of local RNA secondary structure changes induced by SNPs. Hum Mutat 2013; 34:546-56. [PMID: 23315997 PMCID: PMC3708107 DOI: 10.1002/humu.22273] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 12/18/2012] [Indexed: 02/05/2023]
Abstract
Structural characteristics are essential for the functioning of many noncoding RNAs and cis-regulatory elements of mRNAs. SNPs may disrupt these structures, interfere with their molecular function, and hence cause a phenotypic effect. RNA folding algorithms can provide detailed insights into structural effects of SNPs. The global measures employed so far suffer from limited accuracy of folding programs on large RNAs and are computationally too demanding for genome-wide applications. Here, we present a strategy that focuses on the local regions of maximal structural change between mutant and wild-type. These local regions are approximated in a “screening mode” that is intended for genome-wide applications. Furthermore, localized regions are identified as those with maximal discrepancy. The mutation effects are quantified in terms of empirical P values. To this end, the RNAsnp software uses extensive precomputed tables of the distribution of SNP effects as function of length and GC content. RNAsnp thus achieves both a noise reduction and speed-up of several orders of magnitude over shuffling-based approaches. On a data set comprising 501 SNPs associated with human-inherited diseases, we predict 54 to have significant local structural effect in the untranslated region of mRNAs. RNAsnp is available at http://rth.dk/resources/rnasnp.
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47
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Moss WN, Steitz JA. Genome-wide analyses of Epstein-Barr virus reveal conserved RNA structures and a novel stable intronic sequence RNA. BMC Genomics 2013; 14:543. [PMID: 23937650 PMCID: PMC3751371 DOI: 10.1186/1471-2164-14-543] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 08/07/2013] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Epstein-Barr virus (EBV) is a human herpesvirus implicated in cancer and autoimmune disorders. Little is known concerning the roles of RNA structure in this important human pathogen. This study provides the first comprehensive genome-wide survey of RNA and RNA structure in EBV. RESULTS Novel EBV RNAs and RNA structures were identified by computational modeling and RNA-Seq analyses of EBV. Scans of the genomic sequences of four EBV strains (EBV-1, EBV-2, GD1, and GD2) and of the closely related Macacine herpesvirus 4 using the RNAz program discovered 265 regions with high probability of forming conserved RNA structures. Secondary structure models are proposed for these regions based on a combination of free energy minimization and comparative sequence analysis. The analysis of RNA-Seq data uncovered the first observation of a stable intronic sequence RNA (sisRNA) in EBV. The abundance of this sisRNA rivals that of the well-known and highly expressed EBV-encoded non-coding RNAs (EBERs). CONCLUSION This work identifies regions of the EBV genome likely to generate functional RNAs and RNA structures, provides structural models for these regions, and discusses potential functions suggested by the modeled structures. Enhanced understanding of the EBV transcriptome will guide future experimental analyses of the discovered RNAs and RNA structures.
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Affiliation(s)
- Walter N Moss
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA
| | - Joan A Steitz
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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48
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Choo YC, Seki Y, Machinaga A, Ogita N, Takase-Yoden S. The 0.3-kb fragment containing the R-U5-5'leader sequence of Friend murine leukemia virus influences the level of protein expression from spliced mRNA. Virol J 2013; 10:124. [PMID: 23602143 PMCID: PMC3651342 DOI: 10.1186/1743-422x-10-124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 04/12/2013] [Indexed: 12/04/2022] Open
Abstract
Background A neuropathogenic variant of Friend murine leukemia virus (Fr-MLV) clone A8 induces spongiform neurodegeneration when infected into neonatal rats. Studies with chimeras constructed from the A8 virus and the non-neuropathogenic Fr-MLV clone 57 identified a 0.3-kb KpnI-AatII fragment containing a R-U5-5’leader sequence as an important determinant for inducing spongiosis, in addition to the env gene of A8 as the primary determinant. This 0.3-kb fragment contains a 17-nucleotide difference between the A8 and 57 sequences. We previously showed that the 0.3-kb fragment influences expression levels of Env protein in both cultured cells and rat brain, but the corresponding molecular mechanisms are not well understood. Results Studies with expression vectors constructed from the full-length proviral genome of Fr-MLV that incorporated the luciferase (luc) gene instead of the env gene found that the vector containing the A8-0.3-kb fragment yielded a larger amount of spliced luc-mRNA and showed higher expression of luciferase when compared to the vector containing the 57-0.3-kb fragment. The amount of total transcripts from the vectors, the poly (A) tail length of their mRNAs, and the nuclear-cytoplasm distribution of luc-mRNA in transfected cells were also evaluated. The 0.3-kb fragment did not influence transcription efficiency, mRNA polyadenylation or nuclear export of luc-mRNA. Mutational analyses were carried out to determine the importance of nucleotides that differ between the A8 and 57 sequences within the 0.3-kb fragment. In particular, seven nucleotides upstream of the 5’splice site (5’ss) were found to be important in regulating the level of protein expression from spliced messages. Interestingly, these nucleotides reside within the stem-loop structure that has been speculated to limit the recognition of 5’ss. Conclusions The 0.3-kb fragment containing the R-U5-5’leader sequence of Fr-MLV influences the level of protein expression from the spliced-mRNA by regulating the splicing efficiency rather than transcription, nuclear export of spliced-mRNA, or poly (A) addition to mRNA. Seven nucleotides in the 0.3-kb fragment, which reside within the stem-loop structure that has been speculated to limit recognition of the 5’ss, could pinpoint the function of this region.
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Affiliation(s)
- Yeng Cheng Choo
- Department of Bioinformatics, Faculty of Engineering, Soka University, Hachioji, Tokyo 192-8577, Japan
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49
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Abstract
An RNA secondary structure model for the complete HIV-1 genome has recently been published based on SHAPE technology. Several well-known RNA motifs such as TAR and RRE were confirmed and numerous new structured motifs were described that may play important roles in virus replication. The 9 kb viral RNA genome is densely packed with many RNA hairpin motifs and the collective fold may play an important role in HIV-1 biology. We initially focused on 16 RNA hairpin motifs scattered along the viral genome. We considered conservation of these structures, despite sequence variation among virus isolates, as a first indication for a significant function. Four relatively small hairpins exhibited considerable structural conservation and were selected for experimental validation in virus replication assays. Mutations were introduced into the HIV-1 RNA genome to destabilize individual RNA structures without affecting the protein-coding properties (silent codon changes). No major virus replication defects were scored, suggesting that these four hairpin structures do not play essential roles in HIV-1 replication.
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Affiliation(s)
- Stefanie A Knoepfel
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center; University of Amsterdam, Amsterdam, the Netherlands
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50
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Ocwieja KE, Sherrill-Mix S, Mukherjee R, Custers-Allen R, David P, Brown M, Wang S, Link DR, Olson J, Travers K, Schadt E, Bushman FD. Dynamic regulation of HIV-1 mRNA populations analyzed by single-molecule enrichment and long-read sequencing. Nucleic Acids Res 2012; 40:10345-55. [PMID: 22923523 PMCID: PMC3488221 DOI: 10.1093/nar/gks753] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Alternative RNA splicing greatly expands the repertoire of proteins encoded by genomes. Next-generation sequencing (NGS) is attractive for studying alternative splicing because of the efficiency and low cost per base, but short reads typical of NGS only report mRNA fragments containing one or few splice junctions. Here, we used single-molecule amplification and long-read sequencing to study the HIV-1 provirus, which is only 9700 bp in length, but encodes nine major proteins via alternative splicing. Our data showed that the clinical isolate HIV-1(89.6) produces at least 109 different spliced RNAs, including a previously unappreciated ∼1 kb class of messages, two of which encode new proteins. HIV-1 message populations differed between cell types, longitudinally during infection, and among T cells from different human donors. These findings open a new window on a little studied aspect of HIV-1 replication, suggest therapeutic opportunities and provide advanced tools for the study of alternative splicing.
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Affiliation(s)
- Karen E Ocwieja
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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