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Roesmann F, Müller L, Klaassen K, Heß S, Widera M. Interferon-Regulated Expression of Cellular Splicing Factors Modulates Multiple Levels of HIV-1 Gene Expression and Replication. Viruses 2024; 16:938. [PMID: 38932230 PMCID: PMC11209495 DOI: 10.3390/v16060938] [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: 04/30/2024] [Revised: 05/31/2024] [Accepted: 06/03/2024] [Indexed: 06/28/2024] Open
Abstract
Type I interferons (IFN-Is) are pivotal in innate immunity against human immunodeficiency virus I (HIV-1) by eliciting the expression of IFN-stimulated genes (ISGs), which encompass potent host restriction factors. While ISGs restrict the viral replication within the host cell by targeting various stages of the viral life cycle, the lesser-known IFN-repressed genes (IRepGs), including RNA-binding proteins (RBPs), affect the viral replication by altering the expression of the host dependency factors that are essential for efficient HIV-1 gene expression. Both the host restriction and dependency factors determine the viral replication efficiency; however, the understanding of the IRepGs implicated in HIV-1 infection remains greatly limited at present. This review provides a comprehensive overview of the current understanding regarding the impact of the RNA-binding protein families, specifically the two families of splicing-associated proteins SRSF and hnRNP, on HIV-1 gene expression and viral replication. Since the recent findings show specifically that SRSF1 and hnRNP A0 are regulated by IFN-I in various cell lines and primary cells, including intestinal lamina propria mononuclear cells (LPMCs) and peripheral blood mononuclear cells (PBMCs), we particularly discuss their role in the context of the innate immunity affecting HIV-1 replication.
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Affiliation(s)
- Fabian Roesmann
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt, Paul-Ehrlich-Str. 40, 60596 Frankfurt am Main, Germany
| | - Lisa Müller
- Institute of Virology, Medical Faculty, University Hospital Düsseldorf, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Katleen Klaassen
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt, Paul-Ehrlich-Str. 40, 60596 Frankfurt am Main, Germany
| | - Stefanie Heß
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt, Paul-Ehrlich-Str. 40, 60596 Frankfurt am Main, Germany
| | - Marek Widera
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt, Paul-Ehrlich-Str. 40, 60596 Frankfurt am Main, Germany
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2
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Koma T, Doi N, Le BQ, Kondo T, Ishizue M, Tokaji C, Tsukada C, Adachi A, Nomaguchi M. Involvement of a Rarely Used Splicing SD2b Site in the Regulation of HIV-1 vif mRNA Production as Revealed by a Growth-Adaptive Mutation. Viruses 2023; 15:2424. [PMID: 38140666 PMCID: PMC10747208 DOI: 10.3390/v15122424] [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: 11/21/2023] [Revised: 12/09/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
We have previously reported an HIV-1 mutant designated NL-Y226tac that expresses Vif at an ultra-low level, being replication-defective in high-APOBEC3G cells, such as H9. It carries a synonymous mutation within the splicing SA1 site relative to its parental clone. In order to determine whether a certain mutant(s) emerges during multi-infection cycles, we maintained H9 cells infected with a relatively low or high input of NL-Y226tac for extended time periods. Unexpectedly, we reproducibly identified a g5061a mutation in the SD2b site in the two independent long-term culture experiments that partially increases Vif expression and replication ability. Importantly, the adaptive mutation g5061a was demonstrated to enhance vif mRNA production by activation of the SA1 site mediated through increasing usage of a rarely used SD2b site. In the long-term culture initiated by a high virus input, we additionally found a Y226Fttc mutation at the original Y226tac site in SA1 that fully restores Vif expression and replication ability. As expected, the adaptive mutation Y226Fttc enhances vif mRNA production through increasing the splicing site usage of SA1. Our results here revealed the importance of the SD2b nucleotide sequence in producing vif mRNA involved in the HIV-1 adaptation and of mutual antagonism between Vif and APOBEC3 proteins in HIV-1 adaptation/evolution and survival.
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Affiliation(s)
- Takaaki Koma
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
| | - Naoya Doi
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
| | - Bao Quoc Le
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
| | - Tomoyuki Kondo
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
| | - Mitsuki Ishizue
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Chiaki Tokaji
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Chizuko Tsukada
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Akio Adachi
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
| | - Masako Nomaguchi
- Department of Microbiology, Graduate School of Medicine, Tokushima University, Tokushima 770-8503, Japan; (T.K.); (N.D.); (B.Q.L.); (T.K.)
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Sertznig H, Roesmann F, Wilhelm A, Heininger D, Bleekmann B, Elsner C, Santiago M, Schuhenn J, Karakoese Z, Benatzy Y, Snodgrass R, Esser S, Sutter K, Dittmer U, Widera M. SRSF1 acts as an IFN-I-regulated cellular dependency factor decisively affecting HIV-1 post-integration steps. Front Immunol 2022; 13:935800. [PMID: 36458014 PMCID: PMC9706209 DOI: 10.3389/fimmu.2022.935800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 10/19/2022] [Indexed: 08/24/2023] Open
Abstract
Efficient HIV-1 replication depends on balanced levels of host cell components including cellular splicing factors as the family of serine/arginine-rich splicing factors (SRSF, 1-10). Type I interferons (IFN-I) play a crucial role in the innate immunity against HIV-1 by inducing the expression of IFN-stimulated genes (ISGs) including potent host restriction factors. The less well known IFN-repressed genes (IRepGs) might additionally affect viral replication by downregulating host dependency factors that are essential for the viral life cycle; however, so far, the knowledge about IRepGs involved in HIV-1 infection is very limited. In this work, we could demonstrate that HIV-1 infection and the associated ISG induction correlated with low SRSF1 levels in intestinal lamina propria mononuclear cells (LPMCs) and peripheral blood mononuclear cells (PBMCs) during acute and chronic HIV-1 infection. In HIV-1-susceptible cell lines as well as primary monocyte-derived macrophages (MDMs), expression levels of SRSF1 were transiently repressed upon treatment with specific IFNα subtypes in vitro. Mechanically, 4sU labeling of newly transcribed mRNAs revealed that IFN-mediated SRSF1 repression is regulated on early RNA level. SRSF1 knockdown led to an increase in total viral RNA levels, but the relative proportion of the HIV-1 viral infectivity factor (Vif) coding transcripts, which is essential to counteract APOBEC3G-mediated host restriction, was significantly reduced. In the presence of high APOBEC3G levels, however, increased LTR activity upon SRSF1 knockdown facilitated the overall replication, despite decreased vif mRNA levels. In contrast, SRSF1 overexpression significantly impaired HIV-1 post-integration steps including LTR transcription, alternative splice site usage, and virus particle production. Since balanced SRSF1 levels are crucial for efficient viral replication, our data highlight the so far undescribed role of SRSF1 acting as an IFN-modulated cellular dependency factor decisively regulating HIV-1 post-integration steps.
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Affiliation(s)
- Helene Sertznig
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Fabian Roesmann
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
| | - Alexander Wilhelm
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
| | - Delia Heininger
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
| | - Barbara Bleekmann
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Carina Elsner
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Mario Santiago
- Department of Medicine, University of Colorado Denver, Aurora, CO, United States
| | - Jonas Schuhenn
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Zehra Karakoese
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Yvonne Benatzy
- Institute of Biochemistry I, Faculty of Medicine, Goethe-University Frankfurt am Main, Frankfurt, Germany
| | - Ryan Snodgrass
- Institute of Biochemistry I, Faculty of Medicine, Goethe-University Frankfurt am Main, Frankfurt, Germany
| | - Stefan Esser
- Clinic of Dermatology, University Hospital, University of Duisburg-Essen, Essen, Germany
| | - Kathrin Sutter
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Ulf Dittmer
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Marek Widera
- Institute for Virology, University Hospital Essen, University Duisburg-Essen, Essen, Germany
- Institute for Medical Virology, University Hospital Frankfurt, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
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Lee MYH, Khoury G, Olshansky M, Sonza S, Carter GP, McMahon J, Stinear TP, Turner SJ, Lewin SR, Purcell DFJ. Detection of Chimeric Cellular: HIV mRNAs Generated Through Aberrant Splicing in HIV-1 Latently Infected Resting CD4+ T Cells. Front Cell Infect Microbiol 2022; 12:855290. [PMID: 35573784 PMCID: PMC9096486 DOI: 10.3389/fcimb.2022.855290] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
Latent HIV-1 provirus in infected individuals on suppressive therapy does not always remain transcriptionally silent. Both HIV-1 LTR and human gene promoter derived transcriptional events can contribute HIV-1 sequences to the mRNA produced in the cell. In addition, chimeric cellular:HIV mRNA can arise through readthrough transcription and aberrant splicing. Using target enrichment coupled to the Illumina Mi-Seq and PacBio RS II platforms, we show that 3’ LTR activation is frequent in latently infected cells from both the CCL19-induced primary cell model of HIV-1 latency as well as ex vivo samples. In both systems of latent HIV-1 infection, we detected several chimeric species that were generated via activation of a cryptic splice donor site in the 5’ LTR of HIV-1. Aberrant splicing involving the major HIV-1 splice donor sites, SD1 and SD4 disrupts post-transcriptional processing of the gene in which HIV-1 is integrated. In the primary cell model of HIV-1 latency, Tat-encoding sequences are incorporated into the chimeric mRNA transcripts through the use of SD4. Our study unravels clues to the characteristics of HIV-1 integrants that promote formation of chimeric cellular:HIV mRNA and improves the understanding of the HIV-1 RNA footprint in latently infected cells.
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Affiliation(s)
- Michelle Y-H Lee
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Georges Khoury
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Moshe Olshansky
- Department of Microbiology, Biomedical Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Secondo Sonza
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Glen P. Carter
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
- Doherty Applied Microbial Genomics, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - James McMahon
- Department of Infectious Diseases, Monash University and Alfred Hospital, Melbourne, VIC, Australia
| | - Timothy P. Stinear
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
- Doherty Applied Microbial Genomics, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Stephen J. Turner
- Department of Microbiology, Biomedical Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Sharon R. Lewin
- Department of Infectious Diseases, Monash University and Alfred Hospital, Melbourne, VIC, Australia
- Department of Infectious Diseases, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
- Victorian Infectious Diseases Service, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
| | - Damian F. J. Purcell
- Department of Microbiology and Immunology, The University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
- *Correspondence: Damian F. J. Purcell,
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Müller L, Moskorz W, Brillen AL, Hillebrand F, Ostermann PN, Kiel N, Walotka L, Ptok J, Timm J, Lübke N, Schaal H. Altered HIV-1 mRNA Splicing Due to Drug-Resistance-Associated Mutations in Exon 2/2b. Int J Mol Sci 2021; 23:ijms23010156. [PMID: 35008581 PMCID: PMC8745674 DOI: 10.3390/ijms23010156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/18/2021] [Accepted: 12/22/2021] [Indexed: 12/02/2022] Open
Abstract
The underlying molecular mechanism and their general effect on the replication capacity of HIV 1 drug-resistance-associated mutations is often poorly understood. To elucidate the effect of two such mutations located in a region with a high density of spicing regulatory elements on the HIV-1-splicing outcome, bioinformatic predictions were combined with transfection and infection experiments. Results show that the previously described R263K drug-resistance-associated integrase mutation has additionally a severe effect on the ESE2b splicing regulatory element (SRE) in exon 2b, which causes loss of SD2b recognition. This was confirmed by an R263R silent mutation with a similar predicted effect on the exon 2b SRE. In contrast, a V260I mutation and its silent counterpart with a lower effect on ESS2b did not exhibit any differences in the splicing pattern. Since HIV-1 highly relies on a balanced splicing reaction, changes in the splicing outcome can contribute to changes in viral replication and might add to the effect of escape mutations toward antiviral drugs. Thus, a classification of mutations purely addressing proteins is insufficient.
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Koma T, Doi N, Takemoto M, Watanabe K, Yamamoto H, Nakashima S, Adachi A, Nomaguchi M. The Expression Level of HIV-1 Vif Is Optimized by Nucleotide Changes in the Genomic SA1D2prox Region during the Viral Adaptation Process. Viruses 2021; 13:2079. [PMID: 34696508 PMCID: PMC8537775 DOI: 10.3390/v13102079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/05/2021] [Accepted: 10/13/2021] [Indexed: 12/20/2022] Open
Abstract
HIV-1 Vif plays an essential role in viral replication by antagonizing anti-viral cellular restriction factors, a family of APOBEC3 proteins. We have previously shown that naturally-occurring single-nucleotide mutations in the SA1D2prox region, which surrounds the splicing acceptor 1 and splicing donor 2 sites of the HIV-1 genome, dramatically alter the Vif expression level, resulting in variants with low or excessive Vif expression. In this study, we investigated how these HIV-1 variants with poor replication ability adapt and evolve under the pressure of APOBEC3 proteins. Adapted clones obtained through adaptation experiments exhibited an altered replication ability and Vif expression level compared to each parental clone. While various mutations were present throughout the viral genome, all replication-competent adapted clones with altered Vif expression levels were found to bear them within SA1D2prox, without exception. Indeed, the mutations identified within SA1D2prox were responsible for changes in the Vif expression levels and altered the splicing pattern. Moreover, for samples collected from HIV-1-infected patients, we showed that the nucleotide sequences of SA1D2prox can be chronologically changed and concomitantly affect the Vif expression levels. Taken together, these results demonstrated the importance of the SA1D2prox nucleotide sequence for modulating the Vif expression level during HIV-1 replication and adaptation.
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Affiliation(s)
- Takaaki Koma
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
| | - Naoya Doi
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
| | - Mai Takemoto
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Kyosuke Watanabe
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Hideki Yamamoto
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Satoshi Nakashima
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
- Faculty of Medicine, Tokushima University, Tokushima 770-8503, Japan
| | - Akio Adachi
- Department of Microbiology, Kansai Medical University, Osaka 573-1010, Japan
| | - Masako Nomaguchi
- Department of Microbiology, Tokushima University Graduate School of Biomedical Sciences, Tokushima 770-8503, Japan; (T.K.); (N.D.); (M.T.); (K.W.); (H.Y.); (S.N.)
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7
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Ptok J, Müller L, Ostermann PN, Ritchie A, Dilthey AT, Theiss S, Schaal H. Modifying splice site usage with ModCon: Maintaining the genetic code while changing the underlying mRNP code. Comput Struct Biotechnol J 2021; 19:3069-3076. [PMID: 34136105 PMCID: PMC8178101 DOI: 10.1016/j.csbj.2021.05.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 05/14/2021] [Accepted: 05/20/2021] [Indexed: 11/22/2022] Open
Abstract
Codon degeneracy of amino acid sequences permits an additional “mRNP code” layer underlying the genetic code that is related to RNA processing. In pre-mRNA splicing, splice site usage is determined by both intrinsic strength and sequence context providing RNA binding sites for splicing regulatory proteins. In this study, we systematically examined modification of splicing regulatory properties in the neighborhood of a GT site, i.e. potential splice site, without altering the encoded amino acids. We quantified the splicing regulatory properties of the neighborhood around a potential splice site by its Splice Site HEXplorer Weight (SSHW) based on the HEXplorer score algorithm. To systematically modify GT site neighborhoods, either minimizing or maximizing their SSHW, we designed the novel stochastic optimization algorithm ModCon that applies a genetic algorithm with stochastic crossover, insertion and random mutation elements supplemented by a heuristic sliding window approach. To assess the achievable range in SSHW in human splice donors without altering the encoded amino acids, we applied ModCon to a set of 1000 randomly selected Ensembl annotated human splice donor sites, achieving substantial and accurate changes in SSHW. Using ModCon optimization, we successfully switched splice donor usage in a splice site competition reporter containing coding sequences from FANCA, FANCB or BRCA2, while retaining their amino acid coding information. The ModCon algorithm and its R package implementation can assist in reporter design by either introducing novel splice sites, silencing accidental, undesired splice sites, and by generally modifying the entire mRNP code while maintaining the genetic code.
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Key Words
- A, adenine
- F1, filial sequence 1
- G, guanine
- GA, genetic algorithm
- HBS, HBond score
- HBond score
- HEXplorer score
- HZEI, HEXplorer score
- P1, parental sequence 1
- SA, splice acceptor
- SD, splice donor
- SR proteins, serine- and arginine-rich proteins
- SRP, splicing regulatory protein
- SSHW, splice site HEXplorer weight
- SW, sliding window
- Splice donor
- Splicing regulatory proteins
- Splicing reporter
- T, thymine
- eGFP, enhanced green fluorescent protein
- hnRNP, heterogeneous nuclear ribonucleoproteins
- nt, nucleotides
- pre-mRNA splicing
- pre-mRNA, precursor messenger RNA
- snRNA, small nuclear RNA
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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
| | - Philipp Niklas Ostermann
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Anastasia Ritchie
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany
| | - Alexander T Dilthey
- Institute of Medical Statistics and Computational Biology, University of Cologne, Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
- Institute of Medical Microbiology and Hospital Hygiene, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Stephan Theiss
- Institute of Virology, 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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8
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Emery A, Swanstrom R. HIV-1: To Splice or Not to Splice, That Is the Question. Viruses 2021; 13:181. [PMID: 33530363 PMCID: PMC7912102 DOI: 10.3390/v13020181] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 01/21/2021] [Accepted: 01/22/2021] [Indexed: 02/05/2023] Open
Abstract
The transcription of the HIV-1 provirus results in only one type of transcript-full length genomic RNA. To make the mRNA transcripts for the accessory proteins Tat and Rev, the genomic RNA must completely splice. The mRNA transcripts for Vif, Vpr, and Env must undergo splicing but not completely. Genomic RNA (which also functions as mRNA for the Gag and Gag/Pro/Pol precursor polyproteins) must not splice at all. HIV-1 can tolerate a surprising range in the relative abundance of individual transcript types, and a surprising amount of aberrant and even odd splicing; however, it must not over-splice, which results in the loss of full-length genomic RNA and has a dramatic fitness cost. Cells typically do not tolerate unspliced/incompletely spliced transcripts, so HIV-1 must circumvent this cell policing mechanism to allow some splicing while suppressing most. Splicing is controlled by RNA secondary structure, cis-acting regulatory sequences which bind splicing factors, and the viral protein Rev. There is still much work to be done to clarify the combinatorial effects of these splicing regulators. These control mechanisms represent attractive targets to induce over-splicing as an antiviral strategy. Finally, splicing has been implicated in latency, but to date there is little supporting evidence for such a mechanism. In this review we apply what is known of cellular splicing to understand splicing in HIV-1, and present data from our newer and more sensitive deep sequencing assays quantifying the different HIV-1 transcript types.
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MESH Headings
- Alternative Splicing
- Exons
- Gene Expression Regulation, Viral
- HIV-1/genetics
- Nucleic Acid Conformation
- RNA Splicing
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Regulatory Sequences, Nucleic Acid
- Virus Latency/genetics
- rev Gene Products, Human Immunodeficiency Virus/genetics
- rev Gene Products, Human Immunodeficiency Virus/metabolism
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Affiliation(s)
- Ann Emery
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA;
| | - Ronald Swanstrom
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA;
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA
- Center for AIDS Research, University of North Carolina, Chapel Hill, NC 27599, USA
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9
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Erkelenz S, Poschmann G, Ptok J, Müller L, Schaal H. Profiling of cis- and trans-acting factors supporting noncanonical splice site activation. RNA Biol 2020; 18:118-130. [PMID: 32693676 DOI: 10.1080/15476286.2020.1798111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Recently, by combining transcriptomics with functional splicing reporter assays we were able to identify GT > GC > TT as the three highest ranked dinucleotides of human 5' splice sites (5'ss). Here, we have extended our investigations to the proteomic characterization of nuclear proteins that bind to canonical and noncanonical 5'ss. Surprisingly, we found that U1 snRNP binding to functional 5'ss sequences prevented components of the DNA damage response (DDR) from binding to the RNA, suggesting a close link between spliceosome arrangement and genome stability. We demonstrate that all tested noncanonical 5'ss sequences are bona-fide targets of the U2-type spliceosome and are bound by U1 snRNP, including U1-C, in the presence of splicing enhancers. The quantity of precipitated U1-C protein was similar for all noncanonical 5'ss dinucleotides, so that the highly different 5'ss usage was likely due to a later step after early U1 snRNP binding. In addition, we show that an internal GT at positions +5/+6 can be advantageous for splicing at position +1 of noncanonical splice sites. Likewise, and in agreement with previous observations, splicing inactive U1 snRNP binding sites could serve as splicing enhancers, which may also explain the higher abundance of U1 snRNPs compared to other U snRNPs. Finally, we observe that an arginine-serine (RS)-rich domain recruitment to stem loop I of the U1 snRNA is functionally sufficient to promote exon-definition and upstream 3'ss activation.
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Affiliation(s)
- Steffen Erkelenz
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf , Düsseldorf, Germany.,Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne , Cologne, Germany
| | - Gereon Poschmann
- Molecular Proteomics Laboratory, BMFZ, Universitätsklinikum Düsseldorf , Düsseldorf, Germany
| | - Johannes Ptok
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf , Düsseldorf, Germany
| | - Lisa Müller
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf , Düsseldorf, Germany
| | - Heiner Schaal
- Institute of Virology, Medical Faculty, Heinrich Heine University Düsseldorf , Düsseldorf, Germany
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10
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Doi N, Koma T, Adachi A, Nomaguchi M. Expression Level of HIV-1 Vif Can Be Fluctuated by Natural Nucleotide Variations in the vif-Coding and Regulatory SA1D2prox Sequences of the Proviral Genome. Front Microbiol 2019; 10:2758. [PMID: 31849897 PMCID: PMC6893887 DOI: 10.3389/fmicb.2019.02758] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 11/12/2019] [Indexed: 11/26/2022] Open
Abstract
Vif is required for HIV-1 replication in natural target cells by counteracting host restriction factors, APOBEC3 (A3) proteins. We recently demonstrated that Vif expression level can be changed by naturally occurring single-nucleotide variations within SA1D2prox of the HIV-1 genome. We also found that levels for vif/vpr mRNAs are inversely correlated. While amino acid sequence per se is critical for functionality, Vif expression level modulated by signal sequences in its coding region is likely to be important as well. There are two splicing sites in the region involved in vpr expression. To reveal possible fluctuations of Vif-expression level, we examined SA1D2prox and vif gene by chimeric approaches using HIV-1 subtypes B and C with distinct anti-A3 activity. In this report, recombinant clones in subtype B backbone carrying chimeric sequences with respect to SA1D2prox/vif and those within the vif-coding region were generated. Of these, clones containing vif-coding sequence of subtype C, especially its 3′ region, expressed vif/Vif at a decreased level but did at an increased level for vpr/Vpr. Clones with reduced vif/Vif level grew similarly or slightly better than a parental clone in weakly A3G-positive cells but more poorly in highly A3G-expressing cells. Three clones with this property were also tested for their A3-degrading activity. One of the clones appeared to have some defect in addition to the poor ability to express vif/Vif. Taken all together, our results show that natural variations in the SA1D2prox and vif-coding region can change the Vif-expression level and affect the HIV-1 replication potential.
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Affiliation(s)
- Naoya Doi
- Department of Microbiology, Tokushima University Graduate School of Medical Science, Tokushima, Japan
| | - Takaaki Koma
- Department of Microbiology, Tokushima University Graduate School of Medical Science, Tokushima, Japan
| | - Akio Adachi
- Department of Microbiology, Kansai Medical University, Osaka, Japan
| | - Masako Nomaguchi
- Department of Microbiology, Tokushima University Graduate School of Medical Science, Tokushima, Japan
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11
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Pabis M, Corsini L, Vincendeau M, Tripsianes K, Gibson TJ, Brack-Werner R, Sattler M. Modulation of HIV-1 gene expression by binding of a ULM motif in the Rev protein to UHM-containing splicing factors. Nucleic Acids Res 2019; 47:4859-4871. [PMID: 30892606 PMCID: PMC6511859 DOI: 10.1093/nar/gkz185] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/04/2019] [Accepted: 03/18/2019] [Indexed: 12/01/2022] Open
Abstract
The HIV-1 protein Rev is essential for virus replication and ensures the expression of partially spliced and unspliced transcripts. We identified a ULM (UHM ligand motif) motif in the Arginine-Rich Motif (ARM) of the Rev protein. ULMs (UHM ligand motif) mediate protein interactions during spliceosome assembly by binding to UHM (U2AF homology motifs) domains. Using NMR, biophysical methods and crystallography we show that the Rev ULM binds to the UHMs of U2AF65 and SPF45. The highly conserved Trp45 in the Rev ULM is crucial for UHM binding in vitro, for Rev co-precipitation with U2AF65 in human cells and for proper processing of HIV transcripts. Thus, Rev-ULM interactions with UHM splicing factors contribute to the regulation of HIV-1 transcript processing, also at the splicing level. The Rev ULM is an example of viral mimicry of host short linear motifs that enables the virus to interfere with the host molecular machinery.
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Affiliation(s)
- Marta Pabis
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
| | - Lorenzo Corsini
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
| | - Michelle Vincendeau
- Institute of Virology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Research Unit Cellular Signal Integration, Helmholtz Zentrum München, Neuherberg, 85 764, Germany
| | - Konstantinos Tripsianes
- CEITEC - Central European Institute of Technology, Masaryk University, Brno 62 500, Czech Republic
| | | | - Ruth Brack-Werner
- Institute of Virology, Helmholtz Zentrum München, Neuherberg 85 764, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
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12
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Skittrall JP, Ingemarsdotter CK, Gog JR, Lever AML. A scale-free analysis of the HIV-1 genome demonstrates multiple conserved regions of structural and functional importance. PLoS Comput Biol 2019; 15:e1007345. [PMID: 31545786 PMCID: PMC6791557 DOI: 10.1371/journal.pcbi.1007345] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 10/14/2019] [Accepted: 08/19/2019] [Indexed: 12/22/2022] Open
Abstract
HIV-1 replicates via a low-fidelity polymerase with a high mutation rate; strong conservation of individual nucleotides is highly indicative of the presence of critical structural or functional properties. Identifying such conservation can reveal novel insights into viral behaviour. We analysed 3651 publicly available sequences for the presence of nucleic acid conservation beyond that required by amino acid constraints, using a novel scale-free method that identifies regions of outlying score together with a codon scoring algorithm. Sequences with outlying score were further analysed using an algorithm for producing local RNA folds whilst accounting for alignment properties. 11 different conserved regions were identified, some corresponding to well-known cis-acting functions of the HIV-1 genome but also others whose conservation has not previously been noted. We identify rational causes for many of these, including cis functions, possible additional reading frame usage, a plausible mechanism by which the central polypurine tract primes second-strand DNA synthesis and a conformational stabilising function of a region at the 5' end of env.
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Affiliation(s)
- Jordan P. Skittrall
- Department of Medicine, University of Cambridge, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Carin K. Ingemarsdotter
- Department of Medicine, University of Cambridge, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Julia R. Gog
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Centre for Mathematical Sciences, Cambridge, United Kingdom
| | - Andrew M. L. Lever
- Department of Medicine, University of Cambridge, Addenbrooke’s Hospital, Cambridge, United Kingdom
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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13
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Sertznig H, Hillebrand F, Erkelenz S, Schaal H, Widera M. Behind the scenes of HIV-1 replication: Alternative splicing as the dependency factor on the quiet. Virology 2018; 516:176-188. [PMID: 29407375 DOI: 10.1016/j.virol.2018.01.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 01/10/2018] [Accepted: 01/11/2018] [Indexed: 01/31/2023]
Abstract
Alternative splicing plays a key role in the HIV-1 life cycle and is essential to maintain an equilibrium of mRNAs that encode viral proteins and polyprotein-isoforms. In particular, since all early HIV-1 proteins are expressed from spliced intronless and late enzymatic and structural proteins from intron containing, i.e. splicing repressed viral mRNAs, cellular splicing factors and splicing regulatory proteins are crucial for the replication capacity. In this review, we will describe the complex network of cis-acting splicing regulatory elements (SREs), which are mainly localized in the neighbourhoods of all HIV-1 splice sites and warrant the proper ratio of individual transcript isoforms. Since SREs represent binding sites for trans-acting cellular splicing factors interacting with the cellular spliceosomal apparatus we will review the current knowledge of interactions between viral RNA and cellular proteins as well as their impact on viral replication. Finally, we will discuss potential therapeutic approaches targeting HIV-1 alternative splicing.
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Affiliation(s)
- Helene Sertznig
- Institute for Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Frank Hillebrand
- Institute of Virology, Heinrich Heine University, University Hospital, Düsseldorf, Germany
| | - Steffen Erkelenz
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
| | - Heiner Schaal
- Institute of Virology, Heinrich Heine University, University Hospital, Düsseldorf, Germany
| | - Marek Widera
- Institute for Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.
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14
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Takata MA, Soll SJ, Emery A, Blanco-Melo D, Swanstrom R, Bieniasz PD. Global synonymous mutagenesis identifies cis-acting RNA elements that regulate HIV-1 splicing and replication. PLoS Pathog 2018; 14:e1006824. [PMID: 29377940 PMCID: PMC5805364 DOI: 10.1371/journal.ppat.1006824] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 02/08/2018] [Accepted: 12/16/2017] [Indexed: 01/22/2023] Open
Abstract
The ~9.5 kilobase HIV-1 genome contains RNA sequences and structures that control many aspects of viral replication, including transcription, splicing, nuclear export, translation, packaging and reverse transcription. Nonetheless, chemical probing and other approaches suggest that the HIV-1 genome may contain many more RNA secondary structures of unknown importance and function. To determine whether there are additional, undiscovered cis-acting RNA elements in the HIV-1 genome that are important for viral replication, we undertook a global silent mutagenesis experiment. Sixteen mutant proviruses containing clusters of ~50 to ~200 synonymous mutations covering nearly the entire HIV-1 protein coding sequence were designed and synthesized. Analyses of these mutant viruses resulted in their division into three phenotypic groups. Group 1 mutants exhibited near wild-type replication, Group 2 mutants exhibited replication defects accompanied by perturbed RNA splicing, and Group 3 mutants had replication defects in the absence of obvious splicing perturbation. The three phenotypes were caused by mutations that exhibited a clear regional bias in their distribution along the viral genome, and those that caused replication defects all caused reductions in the level of unspliced RNA. We characterized in detail the underlying defects for Group 2 mutants. Second-site revertants that enabled viral replication could be derived for Group 2 mutants, and generally contained point mutations that reduced the utilization of proximal splice sites. Mapping of the changes responsible for splicing perturbations in Group 2 viruses revealed the presence of several RNA sequences that apparently suppressed the use of cryptic or canonical splice sites. Some sequences that affected splicing were diffusely distributed, while others could be mapped to discrete elements, proximal or distal to the affected splice site(s). Overall, our data indicate complex negative regulation of HIV-1 splicing by RNA elements in various regions of the HIV-1 genome that enable balanced splicing and viral replication. In addition to encoding viral proteins, the HIV-1 genome contains sequence elements that act at the level of RNA to enable replication. We undertook an experiment to discover new RNA elements that act in this way by altering nearly the entire coding sequence of the viral genome so as to change the RNA sequence without changing protein sequences. This experiment uncovered two classes of defective mutants. One class had profound defects in RNA splicing, the other had no obvious defects in splicing. Through an analysis of the splicing-defective mutants, we found several previously RNA sequences in the viral genome that affected splicing, enabling a nearly complete catalogue of signals that regulate HIV-1 alternative splicing in infected cells to be derived. Because these newly described sequences lack sequence motifs that are known to bind to canonical splicing-regulatory proteins, they may function through novel mechanisms.
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Affiliation(s)
- Matthew A. Takata
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Steven J. Soll
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
| | - Ann Emery
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Daniel Blanco-Melo
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Ronald Swanstrom
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Paul D. Bieniasz
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
- Howard Hughes Medical Institute, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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15
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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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16
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Control of HIV-1 gene expression by SR proteins. Biochem Soc Trans 2017; 44:1417-1425. [PMID: 27911724 DOI: 10.1042/bst20160113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/08/2016] [Accepted: 07/12/2016] [Indexed: 12/24/2022]
Abstract
Cellular proteins are required for all steps of human immunodeficiency virus type 1 (HIV-1) gene expression including transcription, splicing, 3'-end formation/polyadenylation, nuclear export and translation. SR proteins are a family of cellular RNA-binding proteins that regulate and functionally integrate multiple steps of gene expression. Specific SR proteins are best characterised for regulating HIV-1 RNA splicing by binding specific locations in the viral RNA, though recently they have also been shown to control transcription, 3'-end formation, and translation. Due to their importance in regulating HIV-1 gene expression, SR proteins and their regulatory factors are potential antiviral drug targets.
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17
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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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18
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Dlamini Z, Hull R. Can the HIV-1 splicing machinery be targeted for drug discovery? HIV AIDS-RESEARCH AND PALLIATIVE CARE 2017; 9:63-75. [PMID: 28331370 PMCID: PMC5354533 DOI: 10.2147/hiv.s120576] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
HIV-1 is able to express multiple protein types and isoforms from a single 9 kb mRNA transcript. These proteins are also expressed at particular stages of viral development, and this is achieved through the control of alternative splicing and the export of these transcripts from the nucleus. The nuclear export is controlled by the HIV protein Rev being required to transport incompletely spliced and partially spliced mRNA from the nucleus where they are normally retained. This implies a close relationship between the control of alternate splicing and the nuclear export of mRNA in the control of HIV-1 viral proliferation. This review discusses both the processes. The specificity and regulation of splicing in HIV-1 is controlled by the use of specific splice sites as well as exonic splicing enhancer and exonic splicing silencer sequences. The use of these silencer and enhancer sequences is dependent on the serine arginine family of proteins as well as the heterogeneous nuclear ribonucleoprotein family of proteins that bind to these sequences and increase or decrease splicing. Since alternative splicing is such a critical factor in viral development, it presents itself as a promising drug target. This review aims to discuss the inhibition of splicing, which would stall viral development, as an anti-HIV therapeutic strategy. In this review, the most recent knowledge of splicing in human immunodeficiency viral development and the latest therapeutic strategies targeting human immunodeficiency viral splicing are discussed.
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Affiliation(s)
- Zodwa Dlamini
- Research, Innovation & Engagements Portfolio, Mangosuthu University of Technology, Durban, South Africa
| | - Rodney Hull
- Research, Innovation & Engagements Portfolio, Mangosuthu University of Technology, Durban, South Africa
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19
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Baeyens A, Naessens E, Van Nuffel A, Weening KE, Reilly AM, Claeys E, Trypsteen W, Vandekerckhove L, Eyckerman S, Gevaert K, Verhasselt B. HIV-1 Vpr N-terminal tagging affects alternative splicing of the viral genome. Sci Rep 2016; 6:34573. [PMID: 27721439 PMCID: PMC5056386 DOI: 10.1038/srep34573] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 09/12/2016] [Indexed: 01/11/2023] Open
Abstract
To facilitate studies on Vpr function in replicating HIV-1, we aimed to tag the protein in an infectious virus. First we showed that N-, but not C-terminal HA/FLAG tagging of Vpr protein preserves Vpr cytopathicity. Cloning the tags into proviral DNA however ablated viral production and replication. By construction of additional viral variants we could show this defect was not protein- but RNA-dependent and sequence specific, and characterized by oversplicing of the genomic RNA. Simulation of genomic RNA folding suggested that introduction of the tag sequence induced an alternative folding structure in a region enriched in splice sites and splicing regulatory sequences. In silico predictions identified the HA/His6-Vpr tagging in HIV-1 to affect mRNA folding less than HA/FLAG-Vpr tagging. In vitro infectivity and mRNA splice pattern improved but did not reach wild-type values. Thus, sequence-specific insertions may interfere with mRNA splicing, possibly due to altered RNA folding. Our results point to the complexity of viral RNA genome sequence interactions. This should be taken into consideration when designing viral manipulation strategies, for both research as for biological interventions.
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Affiliation(s)
- Ann Baeyens
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Evelien Naessens
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Anouk Van Nuffel
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Karin E Weening
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Anne-Marie Reilly
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Eva Claeys
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
| | - Wim Trypsteen
- HIV Translational Research Unit, Department of Internal Medicine, Faculty of Medicine and Health Sciences, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Linos Vandekerckhove
- HIV Translational Research Unit, Department of Internal Medicine, Faculty of Medicine and Health Sciences, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Sven Eyckerman
- VIB Medical Biotechnology Center, B-9000 Ghent, Belgium.,Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium
| | - Kris Gevaert
- VIB Medical Biotechnology Center, B-9000 Ghent, Belgium.,Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium
| | - Bruno Verhasselt
- Department of Clinical Chemistry, Microbiology, and Immunology, Ghent University, Ghent, Belgium
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20
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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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21
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Finley J. Reactivation of latently infected HIV-1 viral reservoirs and correction of aberrant alternative splicing in the LMNA gene via AMPK activation: Common mechanism of action linking HIV-1 latency and Hutchinson–Gilford progeria syndrome. Med Hypotheses 2015; 85:320-32. [DOI: 10.1016/j.mehy.2015.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 05/25/2015] [Accepted: 06/08/2015] [Indexed: 12/30/2022]
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Balanced splicing at the Tat-specific HIV-1 3'ss A3 is critical for HIV-1 replication. Retrovirology 2015; 12:29. [PMID: 25889056 PMCID: PMC4422144 DOI: 10.1186/s12977-015-0154-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 02/26/2015] [Indexed: 11/12/2022] Open
Abstract
Background The viral regulatory protein Tat is essential for establishing a productive transcription from the 5′-LTR promoter during the early phase of viral gene expression. Formation of the Tat-encoding mRNAs requires splicing at the viral 3′ss A3, which has previously been shown to be both negatively and positively regulated by the downstream splicing regulatory elements (SREs) ESS2p and ESE2/ESS2. However, using the novel RESCUE-type computational HEXplorer algorithm, we were recently able to identify another splicing enhancer (ESE5807-5838, henceforth referred to as ESEtat) located between ESS2p and ESE2/ESS2. Here we show that ESEtat has a great impact on viral tat-mRNA splicing and that it is fundamental for regulated 3′ss A3 usage. Results Mutational inactivation or locked nucleic acid (LNA)-directed masking of the ESEtat sequence in the context of a replication-competent virus was associated with a failure (i) to activate viral 3′ss A3 and (ii) to accumulate Tat-encoding mRNA species. Consequently, due to insufficient amounts of Tat protein efficient viral replication was drastically impaired. RNA in vitro binding assays revealed SRSF2 and SRSF6 as candidate splicing factors acting through ESEtat and ESE2 for 3′ss A3 activation. This notion was supported by coexpression experiments, in which wild-type, but not ESEtat-negative provirus responded to higher levels of SRSF2 and SRSF6 proteins with higher levels of tat-mRNA splicing. Remarkably, we could also find that SRSF6 overexpression established an antiviral state within provirus-transfected cells, efficiently blocking virus particle production. For the anti-HIV-1 activity the arginine-serine (RS)-rich domain of the splicing factor was dispensable. Conclusions Based on our results, we propose that splicing at 3′ss A3 is dependent on binding of the enhancing SR proteins SRSF2 and SRSF6 to the ESEtat and ESE2 sequence. Mutational inactivation or interference specifically with ESEtat activity by LNA-directed masking seem to account for an early stage defect in viral gene expression, probably by cutting off the supply line of Tat that HIV needs to efficiently transcribe its genome.
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Widera M, Hillebrand F, Erkelenz S, Vasudevan AAJ, Münk C, Schaal H. A functional conserved intronic G run in HIV-1 intron 3 is critical to counteract APOBEC3G-mediated host restriction. Retrovirology 2014; 11:72. [PMID: 25169827 PMCID: PMC4163160 DOI: 10.1186/s12977-014-0072-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 08/08/2014] [Indexed: 11/24/2022] Open
Abstract
Background The HIV-1 accessory proteins, Viral Infectivity Factor (Vif) and the pleiotropic Viral Protein R (Vpr) are important for efficient virus replication. While in non-permissive cells an appropriate amount of Vif is critical to counteract APOBEC3G-mediated host restriction, the Vpr-induced G2 arrest sets the stage for highest transcriptional activity of the HIV-1 long terminal repeat. Both vif and vpr mRNAs harbor their translational start codons within the intron bordering the non-coding leader exons 2 and 3, respectively. Intron retention relies on functional cross-exon interactions between splice sites A1 and D2 (for vif mRNA) and A2 and D3 (for vpr mRNA). More precisely, prior to the catalytic step of splicing, which would lead to inclusion of the non-coding leader exons, binding of U1 snRNP to the 5' splice site (5'ss) facilitates recognition of the 3'ss by U2 snRNP and also supports formation of vif and vpr mRNA. Results We identified a G run localized deep in the vpr AUG containing intron 3 (GI3-2), which was critical for balanced splicing of both vif and vpr non-coding leader exons. Inactivation of GI3-2 resulted in excessive exon 3 splicing as well as exon-definition mediated vpr mRNA formation. However, in an apparently mutually exclusive manner this was incompatible with recognition of upstream exon 2 and vif mRNA processing. As a consequence, inactivation of GI3-2 led to accumulation of Vpr protein with a concomitant reduction in Vif protein. We further demonstrate that preventing hnRNP binding to intron 3 by GI3-2 mutation diminished levels of vif mRNA. In APOBEC3G-expressing but not in APOBEC3G-deficient T cell lines, mutation of GI3-2 led to a considerable replication defect. Moreover, in HIV-1 isolates carrying an inactivating mutation in GI3-2, we identified an adjacent G-rich sequence (GI3-1), which was able to substitute for the inactivated GI3-2. Conclusions The functionally conserved intronic G run in HIV-1 intron 3 plays a major role in the apparently mutually exclusive exon selection of vif and vpr leader exons and hence in vif and vpr mRNA formation. The competition between these exons determines the ability to evade APOBEC3G-mediated antiviral effects due to optimal vif expression. Electronic supplementary material The online version of this article (doi:10.1186/s12977-014-0072-1) contains supplementary material, which is available to authorized users.
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Erkelenz S, Theiss S, Otte M, Widera M, Peter JO, Schaal H. Genomic HEXploring allows landscaping of novel potential splicing regulatory elements. Nucleic Acids Res 2014; 42:10681-97. [PMID: 25147205 PMCID: PMC4176321 DOI: 10.1093/nar/gku736] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Effective splice site selection is critically controlled by flanking splicing regulatory elements (SREs) that can enhance or repress splice site use. Although several computational algorithms currently identify a multitude of potential SRE motifs, their predictive power with respect to mutation effects is limited. Following a RESCUE-type approach, we defined a hexamer-based ‘HEXplorer score’ as average Z-score of all six hexamers overlapping with a given nucleotide in an arbitrary genomic sequence. Plotted along genomic regions, HEXplorer score profiles varied slowly in the vicinity of splice sites. They reflected the respective splice enhancing and silencing properties of splice site neighborhoods beyond the identification of single dedicated SRE motifs. In particular, HEXplorer score differences between mutant and reference sequences faithfully represented exonic mutation effects on splice site usage. Using the HIV-1 pre-mRNA as a model system highly dependent on SREs, we found an excellent correlation in 29 mutations between splicing activity and HEXplorer score. We successfully predicted and confirmed five novel SREs and optimized mutations inactivating a known silencer. The HEXplorer score allowed landscaping of splicing regulatory regions, provided a quantitative measure of mutation effects on splice enhancing and silencing properties and permitted calculation of the mutationally most effective nucleotide.
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Affiliation(s)
- Steffen Erkelenz
- Institute for Virology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Stephan Theiss
- Institute of Clinical Neuroscience and Medical Psychology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Marianne Otte
- Institute of Evolutionary Genetics, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Marek Widera
- Institute for Virology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Jan Otto Peter
- Institute for Virology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
| | - Heiner Schaal
- Institute for Virology, Heinrich-Heine-University Duesseldorf, Duesseldorf, Germany
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Hillebrand F, Erkelenz S, Diehl N, Widera M, Noffke J, Avota E, Schneider-Schaulies S, Dabauvalle MC, Schaal H. The PI3K pathway acting on alternative HIV-1 pre-mRNA splicing. J Gen Virol 2014; 95:1809-1815. [DOI: 10.1099/vir.0.064618-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
HIV-1 mediates pro-survival signals and prevents apoptosis via the phosphatidylinositol-3-kinase (PI3K) pathway. This pathway, however, also affects phosphorylation of serine-arginine (SR) proteins, a family of splicing regulatory factors balancing splice site selection. We now show that pharmacologic inhibition of PI3K signalling alters the HIV-1 splicing pattern of both minigene- and provirus-derived mRNAs. This indicates that HIV-1 might also promote PI3K signalling to balance processing of its transcripts by regulating phosphorylation of splicing regulatory proteins.
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Affiliation(s)
- Frank Hillebrand
- Institute for Virology, Universitaetsklinikum Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf, Germany
- Central Division for Electron Microscopy, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg, Germany
| | - Steffen Erkelenz
- Institute for Virology, Universitaetsklinikum Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf, Germany
| | - Nora Diehl
- Institute for Virology, Universitaetsklinikum Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf, Germany
| | - Marek Widera
- Institute for Virology, Universitaetsklinikum Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf, Germany
| | - Juliane Noffke
- Department of Dermatology, Universitaetsklinikum Duesseldorf, Moorenstrasse 5, D-40225 Duesseldorf, Germany
| | - Elita Avota
- Institute for Virology and Immunobiology, University of Wuerzburg, Versbacher Str. 7, D-97078 Wuerzburg, Germany
| | - Sibylle Schneider-Schaulies
- Institute for Virology and Immunobiology, University of Wuerzburg, Versbacher Str. 7, D-97078 Wuerzburg, Germany
| | - Marie-Christine Dabauvalle
- Central Division for Electron Microscopy, University of Wuerzburg, Am Hubland, D-97074 Wuerzburg, Germany
| | - Heiner Schaal
- Institute for Virology, Universitaetsklinikum Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf, Germany
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Rath AK, Kellermann SJ, Rentmeister A. Programmable Design of Functional Ribonucleoprotein Complexes. Chem Asian J 2014; 9:2045-51. [DOI: 10.1002/asia.201402220] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 04/14/2014] [Indexed: 12/26/2022]
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Natural single-nucleotide polymorphisms in the 3' region of the HIV-1 pol gene modulate viral replication ability. J Virol 2014; 88:4145-60. [PMID: 24478432 DOI: 10.1128/jvi.01859-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED We previously showed that prototype macaque-tropic human immunodeficiency virus type 1 (HIV-1) acquired nonsynonymous growth-enhancing mutations within a narrow genomic region during the adaptation process in macaque cells. These adaptive mutations were clustered in the 3' region of the pol gene, encoding a small portion of the C-terminal domain of integrase (IN). Mutations in HIV-1 IN have been reported to have pleiotropic effects on both the early and late phases in viral replication. cis-acting functions in the IN-coding sequence for viral gene expression have also been reported. We here demonstrated that the adaptive mutations promoted viral growth by increasing virion production with no positive effects on the early replication phase. Synonymous codon alterations in one of the adaptive mutations influenced virion production levels, which suggested nucleotide-dependent regulation. Indeed, when the single-nucleotide natural polymorphisms observed in the 3' regions of 196 HIV-1/simian immunodeficiency virus (SIVcpz) pol genes (nucleotides [nt] 4895 to 4929 for HIV-1 NL4-3) were introduced into macaque- and human-tropic HIV-1 clones, more than half exhibited altered replication potentials. Moreover, single-nucleotide mutations caused parallel increases or decreases in the expression levels of viral late proteins and viral replication potentials. We also showed that the overall expression profiles of viral mRNAs were markedly changed by single-nucleotide mutations. These results demonstrate that the 3' region of the HIV-1 pol gene (nt 4895 to 4929) can alter viral replication potential by modulating the expression pattern of viral mRNAs in a nucleotide-dependent manner. IMPORTANCE Viruses have the plasticity to adapt themselves under various constraints. HIV-1 can mutate and evolve in growth-restrictive cells by acquiring adaptive changes in its genome. We have previously identified some growth-enhancing mutations in a narrow region of the IN-coding sequence, in which a number of cis-acting elements are located. We now focus on the virological significance of this pol gene region and the mechanistic basis underlying its effects on viral replication. We have found several naturally occurring synonymous mutations within this region that alter viral replication potentials. The effects caused by these natural single-nucleotide polymorphisms are linked to the definite expression patterns of viral mRNAs. We show here that the nucleotide sequence of the pol gene (nucleotides 4895 to 4929 for HIV-1 NL4-3) plays an important role in HIV-1 replication by modulating viral gene expression.
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Nawroth I, Mueller F, Basyuk E, Beerens N, Rahbek UL, Darzacq X, Bertrand E, Kjems J, Schmidt U. Stable assembly of HIV-1 export complexes occurs cotranscriptionally. RNA (NEW YORK, N.Y.) 2014; 20:1-8. [PMID: 24255166 PMCID: PMC3866638 DOI: 10.1261/rna.038182.113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 09/13/2013] [Indexed: 06/02/2023]
Abstract
The HIV-1 Rev protein mediates export of unspliced and singly spliced viral transcripts by binding to the Rev response element (RRE) and recruiting the cellular export factor CRM1. Here, we investigated the recruitment of Rev to the transcription sites of HIV-1 reporters that splice either post- or cotranscriptionally. In both cases, we observed that Rev localized to the transcription sites of the reporters and recruited CRM1. Rev and CRM1 remained at the reporter transcription sites when cells were treated with the splicing inhibitor Spliceostatin A (SSA), showing that the proteins associate with RNA prior to or during early spliceosome assembly. Fluorescence recovery after photobleaching (FRAP) revealed that Rev and CRM1 have similar kinetics as the HIV-1 RNA, indicating that Rev, CRM1, and RRE-containing RNAs are released from the site of transcription in one single export complex. These results suggest that cotranscriptional formation of a stable export complex serves as a means to ensure efficient export of unspliced viral RNAs.
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Affiliation(s)
- Isabel Nawroth
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Florian Mueller
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, 75230 Paris cedex 05, France
- Institut Pasteur, Imaging and Modeling Unit, CNRS URA 2582, 75015 Paris, France
| | - Eugenia Basyuk
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Nancy Beerens
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Ulrik L. Rahbek
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Xavier Darzacq
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, 75230 Paris cedex 05, France
| | - Edouard Bertrand
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Jørgen Kjems
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Ute Schmidt
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
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Karn J, Stoltzfus CM. Transcriptional and posttranscriptional regulation of HIV-1 gene expression. Cold Spring Harb Perspect Med 2013; 2:a006916. [PMID: 22355797 DOI: 10.1101/cshperspect.a006916] [Citation(s) in RCA: 284] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Control of HIV-1 gene expression depends on two viral regulatory proteins, Tat and Rev. Tat stimulates transcription elongation by directing the cellular transcriptional elongation factor P-TEFb to nascent RNA polymerases. Rev is required for the transport from the nucleus to the cytoplasm of the unspliced and incompletely spliced mRNAs that encode the structural proteins of the virus. Molecular studies of both proteins have revealed how they interact with the cellular machinery to control transcription from the viral LTR and regulate the levels of spliced and unspliced mRNAs. The regulatory feedback mechanisms driven by HIV-1 Tat and Rev ensure that HIV-1 transcription proceeds through distinct phases. In cells that are not fully activated, limiting levels of Tat and Rev act as potent blocks to premature virus production.
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Affiliation(s)
- Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Vincendeau M, Nagel D, Brenke JK, Brack-Werner R, Hadian K. Heterogenous nuclear ribonucleoprotein Q increases protein expression from HIV-1 Rev-dependent transcripts. Virol J 2013; 10:151. [PMID: 23679954 PMCID: PMC3673855 DOI: 10.1186/1743-422x-10-151] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 03/19/2013] [Indexed: 02/05/2023] Open
Abstract
Background Heterogenous nuclear ribonucleoproteins (hnRNPs) control many processes of the gene expression machinery including mRNA transcription, splicing, export, stability and translation. Recent data show interaction of the HIV-1 Rev regulatory protein with a subset of hnRNP proteins, that includes hnRNP Q, suggesting that hnRNPs can contribute to regulation of HIV-1 gene expression by Rev. Findings In this work we address the effect of hnRNP Q on Rev-dependent gene expression. We show that hnRNP Q overexpression increased levels of proteins produced from a Rev-dependent reporter gene in the presence of Rev. Increased protein levels did not correlate with changes in either the levels or the nucleocytoplasmic distribution of Rev-dependent reporter mRNAs. Similar observations were made in persistently HIV-1 infected HeLa cells. In these cells, hnRNP Q overexpression increased levels of the HIV-1 Gag-p24 protein, while levels of viral Rev-dependent mRNAs were not affected. Conclusion Our data indicate that hnRNP Q can stimulate the protein production of Rev-dependent mRNAs without changing mRNA levels and mRNA export, respectively. This suggests that hnRNP Q can boost HIV gene expression at the level of protein production.
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Affiliation(s)
- Michelle Vincendeau
- Institute of Virology, Helmholtz Zentrum München, Research Center for Environmental Health, Ingolstaedter Landstraße 1, 85764 Neuherberg, Germany
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Pollom E, Dang KK, Potter EL, Gorelick RJ, Burch CL, Weeks KM, Swanstrom R. Comparison of SIV and HIV-1 genomic RNA structures reveals impact of sequence evolution on conserved and non-conserved structural motifs. PLoS Pathog 2013; 9:e1003294. [PMID: 23593004 PMCID: PMC3616985 DOI: 10.1371/journal.ppat.1003294] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 02/22/2013] [Indexed: 11/25/2022] Open
Abstract
RNA secondary structure plays a central role in the replication and metabolism of all RNA viruses, including retroviruses like HIV-1. However, structures with known function represent only a fraction of the secondary structure reported for HIV-1(NL4-3). One tool to assess the importance of RNA structures is to examine their conservation over evolutionary time. To this end, we used SHAPE to model the secondary structure of a second primate lentiviral genome, SIVmac239, which shares only 50% sequence identity at the nucleotide level with HIV-1NL4-3. Only about half of the paired nucleotides are paired in both genomic RNAs and, across the genome, just 71 base pairs form with the same pairing partner in both genomes. On average the RNA secondary structure is thus evolving at a much faster rate than the sequence. Structure at the Gag-Pro-Pol frameshift site is maintained but in a significantly altered form, while the impact of selection for maintaining a protein binding interaction can be seen in the conservation of pairing partners in the small RRE stems where Rev binds. Structures that are conserved between SIVmac239 and HIV-1(NL4-3) also occur at the 5' polyadenylation sequence, in the plus strand primer sites, PPT and cPPT, and in the stem-loop structure that includes the first splice acceptor site. The two genomes are adenosine-rich and cytidine-poor. The structured regions are enriched in guanosines, while unpaired regions are enriched in adenosines, and functionaly important structures have stronger base pairing than nonconserved structures. We conclude that much of the secondary structure is the result of fortuitous pairing in a metastable state that reforms during sequence evolution. However, secondary structure elements with important function are stabilized by higher guanosine content that allows regions of structure to persist as sequence evolution proceeds, and, within the confines of selective pressure, allows structures to evolve.
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Affiliation(s)
- Elizabeth Pollom
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Kristen K. Dang
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - E. Lake Potter
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Robert J. Gorelick
- AIDS and Cancer Virus Program, SAIC-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
| | - Christina L. Burch
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Kevin M. Weeks
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Ronald Swanstrom
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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Erkelenz S, Mueller WF, Evans MS, Busch A, Schöneweis K, Hertel KJ, Schaal H. Position-dependent splicing activation and repression by SR and hnRNP proteins rely on common mechanisms. RNA (NEW YORK, N.Y.) 2013; 19:96-102. [PMID: 23175589 PMCID: PMC3527730 DOI: 10.1261/rna.037044.112] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Alternative splicing is regulated by splicing factors that modulate splice site selection. In some cases, however, splicing factors show antagonistic activities by either activating or repressing splicing. Here, we show that these opposing outcomes are based on their binding location relative to regulated 5' splice sites. SR proteins enhance splicing only when they are recruited to the exon. However, they interfere with splicing by simply relocating them to the opposite intronic side of the splice site. hnRNP splicing factors display analogous opposing activities, but in a reversed position dependence. Activation by SR or hnRNP proteins increases splice site recognition at the earliest steps of exon definition, whereas splicing repression promotes the assembly of nonproductive complexes that arrest spliceosome assembly prior to splice site pairing. Thus, SR and hnRNP splicing factors exploit similar mechanisms to positively or negatively influence splice site selection.
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Affiliation(s)
- Steffen Erkelenz
- Institute of Virology, Heinrich-Heine-University, D-40225 Düsseldorf, Germany
| | - William F. Mueller
- Department of Microbiology and Molecular Genetics, University of California, Irvine, Irvine, California 92697-4025, USA
| | - Melanie S. Evans
- Department of Microbiology and Molecular Genetics, University of California, Irvine, Irvine, California 92697-4025, USA
| | - Anke Busch
- Department of Microbiology and Molecular Genetics, University of California, Irvine, Irvine, California 92697-4025, USA
| | - Katrin Schöneweis
- Institute of Virology, Heinrich-Heine-University, D-40225 Düsseldorf, Germany
| | - Klemens J. Hertel
- Department of Microbiology and Molecular Genetics, University of California, Irvine, Irvine, California 92697-4025, USA
- Corresponding authorsE-mail E-mail
| | - Heiner Schaal
- Institute of Virology, Heinrich-Heine-University, D-40225 Düsseldorf, Germany
- Corresponding authorsE-mail E-mail
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Tra2-mediated recognition of HIV-1 5' splice site D3 as a key factor in the processing of vpr mRNA. J Virol 2012; 87:2721-34. [PMID: 23255807 DOI: 10.1128/jvi.02756-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Small noncoding HIV-1 leader exon 3 is defined by its splice sites A2 and D3. While 3' splice site (3'ss) A2 needs to be activated for vpr mRNA formation, the location of the vpr start codon within downstream intron 3 requires silencing of splicing at 5'ss D3. Here we show that the inclusion of both HIV-1 exon 3 and vpr mRNA processing is promoted by an exonic splicing enhancer (ESE(vpr)) localized between exonic splicing silencer ESSV and 5'ss D3. The ESE(vpr) sequence was found to be bound by members of the Transformer 2 (Tra2) protein family. Coexpression of these proteins in provirus-transfected cells led to an increase in the levels of exon 3 inclusion, confirming that they act through ESE(vpr). Further analyses revealed that ESE(vpr) supports the binding of U1 snRNA at 5'ss D3, allowing bridging interactions across the upstream exon with 3'ss A2. In line with this, an increase or decrease in the complementarity of 5'ss D3 to the 5' end of U1 snRNA was accompanied by a higher or lower vpr expression level. Activation of 3'ss A2 through the proposed bridging interactions, however, was not dependent on the splicing competence of 5'ss D3 because rendering it splicing defective but still competent for efficient U1 snRNA binding maintained the enhancing function of D3. Therefore, we propose that splicing at 3'ss A2 occurs temporally between the binding of U1 snRNA and splicing at D3.
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An intronic G run within HIV-1 intron 2 is critical for splicing regulation of vif mRNA. J Virol 2012; 87:2707-20. [PMID: 23255806 DOI: 10.1128/jvi.02755-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Within target T lymphocytes, human immunodeficiency virus type I (HIV-1) encounters the retroviral restriction factor APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G; A3G), which is counteracted by the HIV-1 accessory protein Vif. Vif is encoded by intron-containing viral RNAs that are generated by splicing at 3' splice site (3'ss) A1 but lack splicing at 5'ss D2, which results in the retention of a large downstream intron. Hence, the extents of activation of 3'ss A1 and repression of D2, respectively, determine the levels of vif mRNA and thus the ability to evade A3G-mediated antiviral effects. The use of 3'ss A1 can be enhanced or repressed by splicing regulatory elements that control the recognition of downstream 5'ss D2. Here we show that an intronic G run (G(I2)-1) represses the use of a second 5'ss, termed D2b, that is embedded within intron 2 and, as determined by RNA deep-sequencing analysis, is normally inefficiently used. Mutations of G(I2)-1 and activation of D2b led to the generation of transcripts coding for Gp41 and Rev protein isoforms but primarily led to considerable upregulation of vif mRNA expression. We further demonstrate, however, that higher levels of Vif protein are actually detrimental to viral replication in A3G-expressing T cell lines but not in A3G-deficient cells. These observations suggest that an appropriate ratio of Vif-to-A3G protein levels is required for optimal virus replication and that part of Vif level regulation is effected by the novel G run identified here.
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Jeang KT. Multi-Faceted Post-Transcriptional Functions of HIV-1 Rev. BIOLOGY 2012; 1:165-74. [PMID: 24832222 PMCID: PMC4009778 DOI: 10.3390/biology1020165] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 07/15/2012] [Accepted: 07/16/2012] [Indexed: 12/27/2022]
Abstract
Post-transcriptional regulation of HIV-1 gene expression is largely governed by the activities of the viral Rev protein. In this minireview, the multiple post-transcriptional activities of Rev in the export of partially spliced and unspliced HIV-1 RNAs from the nucleus to the cytoplasm, in the translation of HIV-1 transcripts, and in the packaging of viral genomic RNAs are reviewed in brief.
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Affiliation(s)
- Kuan-Teh Jeang
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institutes of Allergy and Infectious Diseases, the National Institutes of Health, Bethesda, MD 20892, USA.
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Asang C, Erkelenz S, Schaal H. The HIV-1 major splice donor D1 is activated by splicing enhancer elements within the leader region and the p17-inhibitory sequence. Virology 2012; 432:133-45. [PMID: 22749061 DOI: 10.1016/j.virol.2012.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 04/05/2012] [Accepted: 06/07/2012] [Indexed: 11/25/2022]
Abstract
Usage of the HIV-1 major 5' splice site D1 is a prerequisite for generation of all spliced viral mRNAs encoding essential regulatory and structural proteins. We set out to determine whether flanking sequences ensure D1-activation. We found that an exonic splicing enhancer function is exerted by the region upstream of D1, which is crucially required for its activation. Additionally, we identified an intronic splicing regulatory element within the p17-instability element of the Gag-ORF enhancing D1-activation. Furthermore, our experimental data demonstrated that sequence motifs displaying high similarity to consensus binding sites for SR protein SC35 (SRSF2) overlapping with D1 fine-tune its activation. Our results reveal that D1-activation is safe-guarded by the interplay of upstream and downstream located splicing enhancer elements ensuring usage of D1 even if its strength is decreased upon mutation. The identification of sequence elements activating D1-usage sheds further light on the balanced expression of alternatively spliced HIV-1 mRNAs.
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Affiliation(s)
- Corinna Asang
- Institut für Virologie, Universitätsklinikum Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
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Cavallari I, Rende F, D'Agostino DM, Ciminale V. Converging strategies in expression of human complex retroviruses. Viruses 2011; 3:1395-414. [PMID: 21994786 PMCID: PMC3185809 DOI: 10.3390/v3081395] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 07/28/2011] [Accepted: 07/28/2011] [Indexed: 12/27/2022] Open
Abstract
The discovery of human retroviruses in the early 1980s revealed the existence of viral-encoded non-structural genes that were not evident in previously described animal retroviruses. Based on the absence or presence of these additional genes retroviruses were classified as ‘simple’ and ‘complex’, respectively. Expression of most of these extra genes is achieved through the generation of alternatively spliced mRNAs. The present review summarizes the genetic organization and expression strategies of human complex retroviruses and highlights the converging mechanisms controlling their life cycles.
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Affiliation(s)
- Ilaria Cavallari
- Department of Oncology and Surgical Sciences, University of Padova, Via Gattamelata 64, I-35128 Padova, Italy; E-Mails: (I.C.); (F.R.); (D.M.D.)
| | - Francesca Rende
- Department of Oncology and Surgical Sciences, University of Padova, Via Gattamelata 64, I-35128 Padova, Italy; E-Mails: (I.C.); (F.R.); (D.M.D.)
- Istituto Oncologico Veneto-IRCCS, I-35128 Padova, Italy
| | - Donna M. D'Agostino
- Department of Oncology and Surgical Sciences, University of Padova, Via Gattamelata 64, I-35128 Padova, Italy; E-Mails: (I.C.); (F.R.); (D.M.D.)
| | - Vincenzo Ciminale
- Department of Oncology and Surgical Sciences, University of Padova, Via Gattamelata 64, I-35128 Padova, Italy; E-Mails: (I.C.); (F.R.); (D.M.D.)
- Istituto Oncologico Veneto-IRCCS, I-35128 Padova, Italy
- Author to whom correspondence should be addressed; E-Mail: ; Tel.:+39-049-821-5885; Fax: +39-049-807-2854
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Abstract
It is generally acknowledged that the Tat protein has a pivotal role in HIV-1 replication because it stimulates transcription from the viral long terminal repeat (LTR) promoter by binding to the TAR hairpin in the nascent RNA transcript. However, a multitude of additional Tat functions have been suggested. The importance of these functions is difficult to assess in replication studies with Tat-mutated HIV-1 variants because of the dominant negative effect on viral gene expression. We therefore used an HIV-1 construct that does not depend on the Tat-TAR interaction for transcription to reevaluate whether or not Tat has a second essential function in HIV-1 replication. This HIV-rtTA variant uses the incorporated Tet-On gene expression system for activation of transcription and replicates efficiently upon complete TAR deletion. Here we demonstrated that Tat inactivation does nevertheless severely inhibit replication. Upon long-term culturing, the Tat-minus HIV-rtTA variant acquired mutations in the U3 region that improved promoter activity and reestablished replication. We showed that in the absence of a functional TAR, Tat remains important for viral transcription via Sp1 sequence elements in the U3 promoter region. Substitution of these U3 sequences with nonrelated promoter elements created a virus that replicates efficiently without Tat in SupT1 T cells. These results indicate that Tat has a versatile role in transcription via TAR and U3 elements. The results also imply that Tat has no other essential function in viral replication in cultured T cells.
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Wong R, Balachandran A, Mao AY, Dobson W, Gray-Owen S, Cochrane A. Differential effect of CLK SR Kinases on HIV-1 gene expression: potential novel targets for therapy. Retrovirology 2011; 8:47. [PMID: 21682887 PMCID: PMC3148977 DOI: 10.1186/1742-4690-8-47] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 06/17/2011] [Indexed: 12/03/2022] Open
Abstract
Background RNA processing plays a critical role in the replication of HIV-1, regulated in part through the action of host SR proteins. To explore the impact of modulating SR protein activity on virus replication, the effect of increasing or inhibiting the activity of the Cdc2-like kinase (CLK) family of SR protein kinases on HIV-1 expression and RNA processing was examined. Results Despite their high homology, increasing individual CLK expression had distinct effects on HIV-1, CLK1 enhancing Gag production while CLK2 inhibited the virus. Parallel studies on the anti-HIV-1 activity of CLK inhibitors revealed a similar discrepant effect on HIV-1 expression. TG003, an inhibitor of CLK1, 2 and 4, had no effect on viral Gag synthesis while chlorhexidine, a CLK2, 3 and 4 inhibitor, blocked virus production. Chlorhexidine treatment altered viral RNA processing, decreasing levels of unspliced and single spliced viral RNAs, and reduced Rev accumulation. Subsequent experiments in the context of HIV-1 replication in PBMCs confirmed the capacity of chlorhexidine to suppress virus replication. Conclusions Together, these findings establish that HIV-1 RNA processing can be targeted to suppress virus replication as demonstrated by manipulating individual CLK function and identified chlorhexidine as a lead compound in the development of novel anti-viral therapies.
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Affiliation(s)
- Raymond Wong
- Dept. of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada
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Abstract
The post-transcriptional export of spliced and unspliced HIV-1 (human immunodeficiency virus type 1) RNAs from the nucleus to the cytoplasm is a complex process. Part of the complexity arises from the fact that eukaryotic cells normally retain unspliced RNAs in the nucleus preventing their exit into the cytoplasm. HIV-1 has evolved a protein, Rev, that participates in the export of unspliced / partially spliced viral RNAs from the nucleus. It has been documented that several cellular factors cooperate in trans with Rev, and certain cis-RNA motifs / features are important for transcripts to be recognized by Rev and its co-factors. Here, the post-transcriptional activities of Rev are discussed in the context of a recent finding that an RNA cap methyltransferase contributes to the expression of unspliced / partially spliced HIV-1 transcripts.
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Affiliation(s)
- Venkat S R K Yedavalli
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institutes of Allergy and Infectious Diseases, the National Institutes of Health, Bethesda, MD, USA
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Hartmann L, Neveling K, Borkens S, Schneider H, Freund M, Grassman E, Theiss S, Wawer A, Burdach S, Auerbach AD, Schindler D, Hanenberg H, Schaal H. Correct mRNA processing at a mutant TT splice donor in FANCC ameliorates the clinical phenotype in patients and is enhanced by delivery of suppressor U1 snRNAs. Am J Hum Genet 2010; 87:480-93. [PMID: 20869034 DOI: 10.1016/j.ajhg.2010.08.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/26/2010] [Accepted: 08/31/2010] [Indexed: 12/19/2022] Open
Abstract
The U1 small nuclear RNA (U1 snRNA) as a component of the major U2-dependent spliceosome recognizes 5' splice sites (5'ss) containing GT as the canonical dinucleotide in the intronic positions +1 and +2. The c.165+1G>T germline mutation in the 5'ss of exon 2 of the Fanconi anemia C (FANCC) gene commonly predicted to prevent correct splicing was identified in nine FA patients from three pedigrees. RT-PCR analysis of the endogenous FANCC mRNA splicing pattern of patient-derived fibroblasts revealed aberrant mRNA processing, but surprisingly also correct splicing at the TT dinucleotide, albeit with lower efficiency. This consequently resulted in low levels of correctly spliced transcript and minute levels of normal posttranslationally processed FANCD2 protein, indicating that this naturally occurring TT splicing might contribute to the milder clinical manifestations of the disease in these patients. Functional analysis of this FANCC 5'ss within splicing reporters revealed that both the noncanonical TT dinucleotide and the genomic context of FANCC were required for the residual correct splicing at this mutant 5'ss. Finally, use of lentiviral vectors as a delivery system to introduce expression cassettes for TT-adapted U1 snRNAs into primary FANCC patient fibroblasts allowed the correction of the DNA-damage-induced G2 cell-cycle arrest in these cells, thus representing an alternative transcript-targeting approach for genetic therapy of inherited splice-site mutations.
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Affiliation(s)
- Linda Hartmann
- Institute of Virology, Heinrich-Heine-University, D-40225 Düsseldorf, Germany
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Zychlinski D, Erkelenz S, Melhorn V, Baum C, Schaal H, Bohne J. Limited complementarity between U1 snRNA and a retroviral 5' splice site permits its attenuation via RNA secondary structure. Nucleic Acids Res 2010; 37:7429-40. [PMID: 19854941 PMCID: PMC2794156 DOI: 10.1093/nar/gkp694] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Multiple types of regulation are used by cells and viruses to control alternative splicing. In murine leukemia virus, accessibility of the 5′ splice site (ss) is regulated by an upstream region, which can fold into a complex RNA stem–loop structure. The underlying sequence of the structure itself is negligible, since most of it could be functionally replaced by a simple heterologous RNA stem–loop preserving the wild-type splicing pattern. Increasing the RNA duplex formation between U1 snRNA and the 5′ss by a compensatory mutation in position +6 led to enhanced splicing. Interestingly, this mutation affects splicing only in the context of the secondary structure, arguing for a dynamic interplay between structure and primary 5′ss sequence. The reduced 5′ss accessibility could also be counteracted by recruiting a splicing enhancer domain via a modified MS2 phage coat protein to a single binding site at the tip of the simple RNA stem–loop. The mechanism of 5′ss attenuation was revealed using hyperstable U1 snRNA mutants, showing that restricted U1 snRNP access is the cause of retroviral alternative splicing.
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Affiliation(s)
- Daniela Zychlinski
- Institute for Virology, Hannover Medical School, 30625 Hannover, Germany
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Tazi J, Bakkour N, Marchand V, Ayadi L, Aboufirassi A, Branlant C. Alternative splicing: regulation of HIV-1 multiplication as a target for therapeutic action. FEBS J 2010; 277:867-76. [DOI: 10.1111/j.1742-4658.2009.07522.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Over 40 different human immunodeficiency virus type 1 (HIV-1) mRNA species, both completely and incompletely spliced, are produced by alternative splicing of the primary viral RNA transcript. In addition, about half of the viral RNA remains unspliced and is transported to the cytoplasm where it is used both as mRNA and as genomic RNA. In general, the identities of the completely and incompletely spliced HIV-1 mRNA species are determined by the proximity of the open reading frames to the 5'-end of the mRNAs. The relative abundance of the mRNAs encoding the HIV-1 gene products is determined by the frequency of splicing at the different alternative 3'-splice sites. This chapter will highlight studies showing how HIV-1 uses exon definition to control the level of splicing at each of its 3'-splice sites through a combination of positively acting exonic splicing enhancer (ESE) elements, negatively acting exonic and intronic splicing silencer elements (ESS and ISS elements, respectively), and the 5'-splice sites of the regulated exons. Each of these splicing elements represent binding sites for cellular factors whose levels in the infected cell can determine the dominance of the positive or negative elements on HIV-1 alternative splicing. Both mutations of HIV-1 splicing elements and overexpression or inhibition of cellular splicing factors that bind to these elements have been used to show that disruption of regulated splicing inhibits HIV-1 replication. These studies have provided strong rationale for the investigation and development of antiviral drugs that specifically inhibit HIV-1 RNA splicing.
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Hadian K, Vincendeau M, Mäusbacher N, Nagel D, Hauck SM, Ueffing M, Loyter A, Werner T, Wolff H, Brack-Werner R. Identification of a heterogeneous nuclear ribonucleoprotein-recognition region in the HIV Rev protein. J Biol Chem 2009; 284:33384-91. [PMID: 19808671 DOI: 10.1074/jbc.m109.021659] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Rev protein is a key regulator of human immunodeficiency virus type 1 (HIV-1) gene expression. Rev is primarily known as an adaptor protein for nuclear export of HIV RNAs. However, Rev also contributes to numerous other processes by less well known mechanisms. Understanding the functional nature of Rev requires extensive knowledge of its cellular interaction partners. Here we demonstrate that Rev interacts with members of a large family of multifunctional host cell factors called hnRNPs. Rev employs amino acids 9-14 for specific binding to the heterogeneous nuclear ribonucleoproteins (hnRNP) A1, Q, K, R, and U. In addition, Rev interacts with hnRNP E1 and E2 by a different mechanism. The set of hnRNPs recognized by the N terminus of Rev feature RGG boxes. Exemplary testing of hnRNP A1 revealed a critical role of arginine residues within the RGG box for interaction with Rev. Finally, we demonstrate that expression levels of hnRNP A1, Q, K, R, and U influence HIV-1 production by persistently infected astrocytes, linking these hnRNPs to HIV replication. The novel interaction of HIV-1 Rev with functionally diverse hnRNPs lends further support to the idea that Rev is a multifunctional protein and may be involved in coupling HIV replication to diverse cellular processes and promoting virus-host cell interactions.
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Affiliation(s)
- Kamyar Hadian
- Institute of Virology, Helmholtz Zentrum München, Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany
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Transcriptional errors in human immunodeficiency virus type 1 generate targets for T-cell responses. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2009; 16:1369-71. [PMID: 19571107 DOI: 10.1128/cvi.00410-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We measured T-cell responses to human immunodeficiency virus type 1 (HIV-1) cryptic epitopes encoded by regions of the viral genome not normally translated into viral proteins. T-cell responses to cryptic epitopes and to regions normally spliced out of the HIV-1 viral proteins Rev and Tat were detected in HIV-1-infected subjects.
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Jackson D, Lamb RA. The influenza A virus spliced messenger RNA M mRNA3 is not required for viral replication in tissue culture. J Gen Virol 2009; 89:3097-3101. [PMID: 19008398 DOI: 10.1099/vir.0.2008/004739-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Influenza A virus genome RNA segment 7 encodes three known mRNAs, two of which, M2 mRNA and M mRNA3, are derived by alternative splicing of the primary collinear mRNA transcript using alternative 5' splice sites. The function of M mRNA3 is currently unknown, therefore we attempted to determine whether it is essential for virus replication. Recombinant viruses unable to produce M mRNA3 and/or M2 mRNA were created by mutating the shared 3' splice site. Growth of the mutant viruses in M2-expressing MDCK cells was not significantly affected by the lack of M mRNA3. During the course of a wild-type virus infection, levels of M mRNA3 began to decrease while those of M2 mRNA increased, which may indicate a potential mechanism of alternative splicing control. These data suggest that neither M mRNA3 nor any potential protein product are essential for influenza virus replication in tissue culture.
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Affiliation(s)
- David Jackson
- Howard Hughes Medical Institute and Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA
| | - Robert A Lamb
- Howard Hughes Medical Institute and Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA
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Ngandu NK, Scheffler K, Moore P, Woodman Z, Martin D, Seoighe C. Extensive purifying selection acting on synonymous sites in HIV-1 Group M sequences. Virol J 2008; 5:160. [PMID: 19105834 PMCID: PMC2666660 DOI: 10.1186/1743-422x-5-160] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 12/23/2008] [Indexed: 11/26/2022] Open
Abstract
Background Positive selection pressure acting on protein-coding sequences is usually inferred when the rate of nonsynonymous substitution is greater than the synonymous rate. However, purifying selection acting directly on the nucleotide sequence can lower the synonymous substitution rate. This could result in false inference of positive selection because when synonymous changes at some sites are under purifying selection, the average synonymous rate is an underestimate of the neutral rate of evolution. Even though HIV-1 coding sequences contain a number of regions that function at the nucleotide level, and are thus likely to be affected by purifying selection, studies of positive selection assume that synonymous substitutions can be used to estimate the neutral rate of evolution. Results We modelled site-to-site variation in the synonymous substitution rate across coding regions of the HIV-1 genome. Synonymous substitution rates were found to vary significantly within and between genes. Surprisingly, regions of the genome that encode proteins in more than one frame had significantly higher synonymous substitution rates than regions coding in a single frame. We found evidence of strong purifying selection pressure affecting synonymous mutations in fourteen regions with known functions. These included an exonic splicing enhancer, the rev-responsive element, the poly-purine tract and a transcription factor binding site. A further five highly conserved regions were located within known functional domains. We also found four conserved regions located in env and vpu which have not been characterized previously. Conclusion We provide the coordinates of genomic regions with markedly lower synonymous substitution rates, which are putatively under the influence of strong purifying selection pressure at the nucleotide level as well as regions encoding proteins in more than one frame. These regions should be excluded from studies of positive selection acting on HIV-1 coding regions.
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Affiliation(s)
- Nobubelo K Ngandu
- National Bioinformatics Network Node, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, 7925, South Africa.
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Negative and positive mRNA splicing elements act competitively to regulate human immunodeficiency virus type 1 vif gene expression. J Virol 2008; 82:3921-31. [PMID: 18272582 DOI: 10.1128/jvi.01558-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Over 40 different human immunodeficiency virus type 1 (HIV-1) mRNAs are produced by alternative splicing of the primary HIV-1 RNA transcripts. In addition, approximately half of the viral RNA remains unspliced and is used as genomic RNA and as mRNA for the Gag and Pol gene products. Regulation of splicing at the HIV-1 3' splice sites (3'ss) requires suboptimal polypyrimidine tracts, and positive or negative regulation occurs through the binding of cellular factors to cis-acting splicing regulatory elements. We have previously shown that splicing at HIV-1 3'ss A1, which produces single-spliced vif mRNA and promotes the inclusion of HIV exon 2 into both completely and incompletely spliced viral mRNAs, is increased by optimizing the 5' splice site (5'ss) downstream of exon 2 (5'ss D2). Here we show that the mutations within 5'ss D2 that are predicted to lower or increase the affinity of the 5'ss for U1 snRNP result in reduced or increased Vif expression, respectively. Splicing at 5'ss D2 was not necessary for the effect of 5'ss D2 on Vif expression. In addition, we have found that mutations of the GGGG motif proximal to the 5'ss D2 increase exon 2 inclusion and Vif expression. Finally, we report the presence of a novel exonic splicing enhancer (ESE) element within the 5'-proximal region of exon 2 that facilitates both exon inclusion and Vif expression. This ESE binds specifically to the cellular SR protein SRp75. Our results suggest that the 5'ss D2, the proximal GGGG silencer, and the ESE act competitively to determine the level of vif mRNA splicing and Vif expression. We propose that these positive and negative splicing elements act together to allow the accumulation of vif mRNA and unspliced HIV-1 mRNA, compatible with optimal virus replication.
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Asang C, Hauber I, Schaal H. Insights into the selective activation of alternatively used splice acceptors by the human immunodeficiency virus type-1 bidirectional splicing enhancer. Nucleic Acids Res 2008; 36:1450-63. [PMID: 18203748 PMCID: PMC2275126 DOI: 10.1093/nar/gkm1147] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The guanosine-adenosine-rich exonic splicing enhancer (GAR ESE) identified in exon 5 of the human immunodeficiency virus type-1 (HIV-1) pre-mRNA activates either an enhancer-dependent 5′ splice site (ss) or 3′ ss in 1-intron reporter constructs in the presence of the SR proteins SF2/ASF2 and SRp40. Characterizing the mode of action of the GAR ESE inside the internal HIV-1 exon 5 we found that this enhancer fulfils a dual splicing regulatory function (i) by synergistically mediating exon recognition through its individual SR protein-binding sites and (ii) by conferring 3′ ss selectivity within the 3′ ss cluster preceding exon 5. Both functions depend upon the GAR ESE, U1 snRNP binding at the downstream 5′ ss D4 and the E42 sequence located between these elements. Therefore, a network of cross-exon interactions appears to regulate splicing of the alternative exons 4a and 5. As the GAR ESE-mediated activation of the upstream 3′ ss cluster also is essential for the processing of intron-containing vpu/env-mRNAs during intermediate viral gene expression, the GAR enhancer substantially contributes to the regulation of viral replication.
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Affiliation(s)
- Corinna Asang
- Institut für Virologie, Universitätsklinikum Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany
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