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The HIV-1 Gag Protein Displays Extensive Functional and Structural Roles in Virus Replication and Infectivity. Int J Mol Sci 2022; 23:ijms23147569. [PMID: 35886917 PMCID: PMC9323242 DOI: 10.3390/ijms23147569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/15/2022] [Accepted: 06/19/2022] [Indexed: 01/10/2023] Open
Abstract
Once merely thought of as the protein responsible for the overall physical nature of the human immunodeficiency virus type 1 (HIV-1), the Gag polyprotein has since been elucidated to have several roles in viral replication and functionality. Over the years, extensive research into the polyproteins’ structure has revealed that Gag can mediate its own trafficking to the plasma membrane, it can interact with several host factors and can even aid in viral genome packaging. Not surprisingly, Gag has also been associated with HIV-1 drug resistance and even treatment failure. Therefore, this review provides an extensive overview of the structural and functional roles of the HIV-1 Gag domains in virion integrity, functionality and infectivity.
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Bussienne C, Marquet R, Paillart JC, Bernacchi S. Post-Translational Modifications of Retroviral HIV-1 Gag Precursors: An Overview of Their Biological Role. Int J Mol Sci 2021; 22:ijms22062871. [PMID: 33799890 PMCID: PMC8000049 DOI: 10.3390/ijms22062871] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/06/2021] [Accepted: 03/09/2021] [Indexed: 11/24/2022] Open
Abstract
Protein post-translational modifications (PTMs) play key roles in eukaryotes since they finely regulate numerous mechanisms used to diversify the protein functions and to modulate their signaling networks. Besides, these chemical modifications also take part in the viral hijacking of the host, and also contribute to the cellular response to viral infections. All domains of the human immunodeficiency virus type 1 (HIV-1) Gag precursor of 55-kDa (Pr55Gag), which is the central actor for viral RNA specific recruitment and genome packaging, are post-translationally modified. In this review, we summarize the current knowledge about HIV-1 Pr55Gag PTMs such as myristoylation, phosphorylation, ubiquitination, sumoylation, methylation, and ISGylation in order to figure out how these modifications affect the precursor functions and viral replication. Indeed, in HIV-1, PTMs regulate the precursor trafficking between cell compartments and its anchoring at the plasma membrane, where viral assembly occurs. Interestingly, PTMs also allow Pr55Gag to hijack the cell machinery to achieve viral budding as they drive recognition between viral proteins or cellular components such as the ESCRT machinery. Finally, we will describe and compare PTMs of several other retroviral Gag proteins to give a global overview of their role in the retroviral life cycle.
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How HIV-1 Gag Manipulates Its Host Cell Proteins: A Focus on Interactors of the Nucleocapsid Domain. Viruses 2020; 12:v12080888. [PMID: 32823718 PMCID: PMC7471995 DOI: 10.3390/v12080888] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 08/06/2020] [Accepted: 08/10/2020] [Indexed: 12/27/2022] Open
Abstract
The human immunodeficiency virus (HIV-1) polyprotein Gag (Group-specific antigen) plays a central role in controlling the late phase of the viral lifecycle. Considered to be only a scaffolding protein for a long time, the structural protein Gag plays determinate and specific roles in HIV-1 replication. Indeed, via its different domains, Gag orchestrates the specific encapsidation of the genomic RNA, drives the formation of the viral particle by its auto-assembly (multimerization), binds multiple viral proteins, and interacts with a large number of cellular proteins that are needed for its functions from its translation location to the plasma membrane, where newly formed virions are released. Here, we review the interactions between HIV-1 Gag and 66 cellular proteins. Notably, we describe the techniques used to evidence these interactions, the different domains of Gag involved, and the implications of these interactions in the HIV-1 replication cycle. In the final part, we focus on the interactions involving the highly conserved nucleocapsid (NC) domain of Gag and detail the functions of the NC interactants along the viral lifecycle.
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Huang L, Li L, Tien C, LaBarbera DV, Chen C. Targeting HIV-1 Protease Autoprocessing for High-throughput Drug Discovery and Drug Resistance Assessment. Sci Rep 2019; 9:301. [PMID: 30670786 PMCID: PMC6343032 DOI: 10.1038/s41598-018-36730-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 11/23/2018] [Indexed: 01/28/2023] Open
Abstract
HIV-1 protease autoprocessing liberates the free mature protease from its Gag-Pol polyprotein precursor through a series of highly regulated autoproteolysis reactions. Herein, we report the development and validation (Z' ≥ 0.50) of a cell-based functional assay for high-throughput screening (HTS) of autoprocessing inhibitors using fusion precursors in combination with AlphaLISA (amplified luminescent proximity homogeneous assay ELISA). Through pilot screening of a collection of 130 known protease inhibitors, the AlphaLISA assay confirmed all 11 HIV protease inhibitors in the library capable of suppressing precursor autoprocessing at low micromolar concentrations. Meanwhile, other protease inhibitors had no impact on precursor autoprocessing. We next conducted HTS of ~23,000 compounds but found no positive hits. Such high selectivity is advantageous for large-scale HTS campaigns and as anticipated based on assay design because a positive hit needs simultaneously to be nontoxic, cell permeable, and inhibiting precursor autoprocessing. Furthermore, AlphaLISA quantification of fusion precursors carrying mutations known to cause resistance to HIV protease inhibitors faithfully recapitulated the reported resistance, suggesting that precursor autoprocessing is a critical step contributing to drug resistance. Taken together, this reported AlphaLISA platform will provide a useful tool for drug discovery targeting HIV-1 protease autoprocessing and for quantification of PI resistance.
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Affiliation(s)
- Liangqun Huang
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Linfeng Li
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - ChihFeng Tien
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Daniel V LaBarbera
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA.
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Tien C, Huang L, Watanabe SM, Speidel JT, Carter CA, Chen C. Context-dependent autoprocessing of human immunodeficiency virus type 1 protease precursors. PLoS One 2018; 13:e0191372. [PMID: 29338056 PMCID: PMC5770051 DOI: 10.1371/journal.pone.0191372] [Citation(s) in RCA: 6] [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: 10/13/2017] [Accepted: 01/03/2018] [Indexed: 11/29/2022] Open
Abstract
HIV-1 protease autoprocessing is responsible for liberation of free mature protease (PR) from the Gag-Pol polyprotein precursor. A cell-based model system was previously developed to examine the autoprocessing mechanism of fusion precursors carrying the p6*-PR miniprecursor sandwiched between various proteins or epitopes. We here report that precursor autoprocessing is context-dependent as its activity and outcomes can be modulated by sequences upstream of p6*-PR. This was exemplified by the 26aa maltose binding protein (MBP) signal peptide (SigP) when placed at the N-terminus of a fusion precursor. The mature PRs released from SigP-carrying precursors are resistant to self-degradation whereas those released from SigP-lacking fusion precursors are prone to self-degradation. A H69D mutation in PR abolished autoprocessing of SigP-containing fusion precursors whereas it only partially suppressed autoprocessing of fusion precursors lacking SigP. An autoprocessing deficient GFP fusion precursor with SigP exhibited a subcellular distribution pattern distinct from the one without it in transfected HeLa cells. Furthermore, a SigP fusion precursor carrying a substitution at the P1 position released the mature PR and PR-containing fragments that were different from those released from the precursor carrying the same mutation but lacking SigP. We also examined autoprocessing outcomes in viral particles produced by a NL4-3 derived proviral construct and demonstrated the existence of several PR-containing fragments along with the mature PR. Some of these resembled the SigP precursor autoprocessing outcomes. This finding of context-dependent modulation reveals the complexity of precursor autoprocessing regulation that most likely accompanies sequence variation imposed by the evolution of the upstream Gag moiety.
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Affiliation(s)
- ChihFeng Tien
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Liangqun Huang
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Susan M. Watanabe
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Jordan T. Speidel
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Carol A. Carter
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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6
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Strickland M, Ehrlich LS, Watanabe S, Khan M, Strub MP, Luan CH, Powell MD, Leis J, Tjandra N, Carter CA. Tsg101 chaperone function revealed by HIV-1 assembly inhibitors. Nat Commun 2017; 8:1391. [PMID: 29123089 PMCID: PMC5680296 DOI: 10.1038/s41467-017-01426-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 09/15/2017] [Indexed: 01/08/2023] Open
Abstract
HIV-1 replication requires Tsg101, a component of cellular endosomal sorting complex required for transport (ESCRT) machinery. Tsg101 possesses an ubiquitin (Ub) E2 variant (UEV) domain with a pocket that can bind PT/SAP motifs and another pocket that can bind Ub. The PTAP motif in the viral structural precursor polyprotein, Gag, allows the recruitment of Tsg101 and other ESCRTs to virus assembly sites where they mediate budding. It is not known how or even whether the UEV Ub binding function contributes to virus production. Here, we report that disruption of UEV Ub binding by commonly used drugs arrests assembly at an early step distinct from the late stage involving PTAP binding disruption. NMR reveals that the drugs form a covalent adduct near the Ub-binding pocket leading to the disruption of Ub, but not PTAP binding. We conclude that the Ub-binding pocket has a chaperone function involved in bud initiation.
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Affiliation(s)
- Madeleine Strickland
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Lorna S Ehrlich
- Department of Molecular Genetics & Microbiology, School of Medicine, Stony Brook University, Stony Brook, NY, 11794-5222, USA
| | - Susan Watanabe
- Department of Molecular Genetics & Microbiology, School of Medicine, Stony Brook University, Stony Brook, NY, 11794-5222, USA
| | - Mahfuz Khan
- Department of Microbiology and Immunology, Morehouse School of Medicine, Atlanta, GA, 30310, USA
| | - Marie-Paule Strub
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Chi-Hao Luan
- High Throughput Analysis Laboratory and Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA
| | - Michael D Powell
- Department of Microbiology and Immunology, Morehouse School of Medicine, Atlanta, GA, 30310, USA
| | - Jonathan Leis
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Carol A Carter
- Department of Molecular Genetics & Microbiology, School of Medicine, Stony Brook University, Stony Brook, NY, 11794-5222, USA.
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Watanabe SM, Simon V, Durham ND, Kemp BR, Machihara S, Kemal KS, Shi B, Foley B, Li H, Chen BK, Weiser B, Burger H, Anastos K, Chen C, Carter CA. The HIV-1 late domain-2 S40A polymorphism in antiretroviral (or ART)-exposed individuals influences protease inhibitor susceptibility. Retrovirology 2016; 13:64. [PMID: 27600154 PMCID: PMC5011916 DOI: 10.1186/s12977-016-0298-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 08/21/2016] [Indexed: 11/24/2022] Open
Abstract
Background The p6 region of the HIV-1 structural precursor polyprotein, Gag, contains two motifs, P7TAP11 and L35YPLXSL41, designated as late (L) domain-1 and -2, respectively. These motifs bind the ESCRT-I factor Tsg101 and the ESCRT adaptor Alix, respectively, and are critical for efficient budding of virus particles from the plasma membrane. L domain-2 is thought to be functionally redundant to PTAP. To identify possible other functions of L domain-2, we examined this motif in dominant viruses that emerged in a group of 14 women who had detectable levels of HIV-1 in both plasma and genital tract despite a history of current or previous antiretroviral therapy. Results Remarkably, variants possessing mutations or rare polymorphisms in the highly conserved L domain-2 were identified in seven of these women. A mutation in a conserved residue (S40A) that does not reduce Gag interaction with Alix and therefore did not reduce budding efficiency was further investigated. This mutation causes a simultaneous change in the Pol reading frame but exhibits little deficiency in Gag processing and virion maturation. Whether introduced into the HIV-1 NL4-3 strain genome or a model protease (PR) precursor, S40A reduced production of mature PR. This same mutation also led to high level detection of two extended forms of PR that were fairly stable compared to the WT in the presence of IDV at various concentrations; one of the extended forms was effective in trans processing even at micromolar IDV. Conclusions Our results indicate that L domain-2, considered redundant in vitro, can undergo mutations in vivo that significantly alter PR function. These may contribute fitness benefits in both the absence and presence of PR inhibitor. Electronic supplementary material The online version of this article (doi:10.1186/s12977-016-0298-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Susan M Watanabe
- Department of Molecular Genetics and Microbiology, Stony Brook University, Life Sciences Bldg., Stony Brook, NY, 11794-5222, USA
| | - Viviana Simon
- Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Natasha D Durham
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Brittney R Kemp
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA
| | - Satoshi Machihara
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA
| | | | - Binshan Shi
- Department of Health Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, USA
| | - Brian Foley
- Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Hongru Li
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Benjamin K Chen
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Barbara Weiser
- Department of Medicine, University of California Davis, Davis, CA, USA.,Department of Medicine, Sacramento VA Medical Center, Cordova, CA, USA
| | - Harold Burger
- Department of Medicine, University of California Davis, Davis, CA, USA.,Department of Medicine, Sacramento VA Medical Center, Cordova, CA, USA
| | - Kathryn Anastos
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA.
| | - Carol A Carter
- Department of Molecular Genetics and Microbiology, Stony Brook University, Life Sciences Bldg., Stony Brook, NY, 11794-5222, USA.
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Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag. Viruses 2016; 8:117. [PMID: 27120610 PMCID: PMC4848609 DOI: 10.3390/v8040117] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 03/29/2016] [Accepted: 04/18/2016] [Indexed: 12/15/2022] Open
Abstract
The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (l-) domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane.
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Abstract
UNLABELLED We have examined the interactions of wild-type (WT) and matrix protein-deleted (ΔMA) HIV-1 precursor Gag (PrGag) proteins in virus-producing cells using a biotin ligase-tagging approach. To do so, WT and ΔMA PrGag proteins were tagged with the Escherichia coli promiscuous biotin ligase (BirA*), expressed in cells, and examined. Localization patterns of PrGag proteins and biotinylated proteins overlapped, consistent with observations that BirA*-tagged proteins biotinylate neighbor proteins that are in close proximity. Results indicate that BirA*-tagged PrGag proteins biotinylated themselves as well as WT PrGag proteins in trans. Previous data have shown that the HIV-1 Envelope (Env) protein requires an interaction with MA for assembly into virions. Unexpectedly, ΔMA proteins biotinylated Env, whereas WT BirA*-tagged proteins did not, suggesting that the presence of MA made Env inaccessible to biotinylation. We also identified over 50 cellular proteins that were biotinylated by BirA*-tagged PrGag proteins. These included membrane proteins, cytoskeleton-associated proteins, nuclear transport factors, lipid metabolism regulators, translation factors, and RNA-processing proteins. The identification of these biotinylated proteins offers new insights into HIV-1 Gag protein trafficking and activities and provides new potential targets for antiviral interference. IMPORTANCE We have employed a novel strategy to analyze the interactions of the HIV-1 structural Gag proteins, which involved tagging wild-type and mutant Gag proteins with a biotin ligase. Expression of the tagged proteins in cells allowed us to analyze proteins that came in close proximity to the Gag proteins as they were synthesized, transported, assembled, and released from cells. The tagged proteins biotinylated proteins encoded by the HIV-1 pol gene and neighbor Gag proteins, but, surprisingly, only the mutant Gag protein biotinylated the HIV-1 Envelope protein. We also identified over 50 cellular proteins that were biotinylated, including membrane and cytoskeletal proteins and proteins involved in lipid metabolism, nuclear import, translation, and RNA processing. Our results offer new insights into HIV-1 Gag protein trafficking and activities and provide new potential targets for antiviral interference.
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Li G, Theys K, Verheyen J, Pineda-Peña AC, Khouri R, Piampongsant S, Eusébio M, Ramon J, Vandamme AM. A new ensemble coevolution system for detecting HIV-1 protein coevolution. Biol Direct 2015; 10:1. [PMID: 25564011 PMCID: PMC4332441 DOI: 10.1186/s13062-014-0031-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 12/02/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND A key challenge in the field of HIV-1 protein evolution is the identification of coevolving amino acids at the molecular level. In the past decades, many sequence-based methods have been designed to detect position-specific coevolution within and between different proteins. However, an ensemble coevolution system that integrates different methods to improve the detection of HIV-1 protein coevolution has not been developed. RESULTS We integrated 27 sequence-based prediction methods published between 2004 and 2013 into an ensemble coevolution system. This system allowed combinations of different sequence-based methods for coevolution predictions. Using HIV-1 protein structures and experimental data, we evaluated the performance of individual and combined sequence-based methods in the prediction of HIV-1 intra- and inter-protein coevolution. We showed that sequence-based methods clustered according to their methodology, and a combination of four methods outperformed any of the 27 individual methods. This four-method combination estimated that HIV-1 intra-protein coevolving positions were mainly located in functional domains and physically contacted with each other in the protein tertiary structures. In the analysis of HIV-1 inter-protein coevolving positions between Gag and protease, protease drug resistance positions near the active site mostly coevolved with Gag cleavage positions (V128, S373-T375, A431, F448-P453) and Gag C-terminal positions (S489-Q500) under selective pressure of protease inhibitors. CONCLUSIONS This study presents a new ensemble coevolution system which detects position-specific coevolution using combinations of 27 different sequence-based methods. Our findings highlight key coevolving residues within HIV-1 structural proteins and between Gag and protease, shedding light on HIV-1 intra- and inter-protein coevolution.
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Affiliation(s)
- Guangdi Li
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium.
| | - Kristof Theys
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium.
| | - Jens Verheyen
- Institute of Virology, University hospital, University Duisburg-Essen, Essen, Germany.
| | - Andrea-Clemencia Pineda-Peña
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium. .,Clinical and Molecular Infectious Disease Group, Faculty of Sciences and Mathematics, Universidad del Rosario, Bogotá, Colombia.
| | - Ricardo Khouri
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium.
| | - Supinya Piampongsant
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium.
| | - Mónica Eusébio
- Centro de Malária e Outras Doenças Tropicais and Unidade de Microbiologia, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal.
| | - Jan Ramon
- Department of Computer Science, KU Leuven - University of Leuven, Leuven, Belgium.
| | - Anne-Mieke Vandamme
- KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Leuven, Belgium. .,Centro de Malária e Outras Doenças Tropicais and Unidade de Microbiologia, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal.
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Radestock B, Burk R, Müller B, Kräusslich HG. Re-visiting the functional Relevance of the highly conserved Serine 40 Residue within HIV-1 p6(Gag). Retrovirology 2014; 11:114. [PMID: 25524645 PMCID: PMC4301901 DOI: 10.1186/s12977-014-0114-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/17/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND HIV-1 formation is driven by the viral structural polyprotein Gag, which assembles at the plasma membrane into a hexagonal lattice. The C-terminal p6(Gag) domain harbors short peptide motifs, called late domains, which recruit the cellular endosomal sorting complex required for transport and promote HIV-1 abscission from the plasma membrane. Similar to late domain containing proteins of other viruses, HIV-1 p6 is phosphorylated at multiple residues, including a highly conserved serine at position 40. Previously published studies showed that an S40F exchange in p6(Gag) severely affected virus infectivity, while we had reported that mutation of all phosphorylatable residues in p6(Gag) had only minor effects. FINDINGS We introduced mutations into p6(Gag) without affecting the overlapping pol reading frame by using an HIV-1 derivative where gag and pol are genetically uncoupled. HIV-1 derivatives with a conservative S40N or a non-conservative S40F exchange were produced. The S40F substitution severely affected virus maturation and infectivity as reported before, while the S40N exchange caused no functional defects and the variant was fully infectious in T-cell lines and primary T-cells. CONCLUSIONS An HIV-1 variant carrying a conservative S40N exchange in p6(Gag) is fully functional in tissue culture demonstrating that neither S40 nor its phosphorylation are required for HIV-1 release and maturation. The phenotype of the S40F mutation appears to be caused by the bulky hydrophobic residue introduced into a flexible region.
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Affiliation(s)
- Benjamin Radestock
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120, Heidelberg, Germany.
| | - Robin Burk
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120, Heidelberg, Germany.
| | - Barbara Müller
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120, Heidelberg, Germany.
| | - Hans-Georg Kräusslich
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120, Heidelberg, Germany.
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12
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Mutation of the highly conserved Ser-40 of the HIV-1 p6 gag protein to Phe causes the formation of a hydrophobic patch, enhances membrane association, and polyubiquitination of Gag. Viruses 2014; 6:3738-65. [PMID: 25279819 PMCID: PMC4213559 DOI: 10.3390/v6103738] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 09/19/2014] [Accepted: 09/26/2014] [Indexed: 01/04/2023] Open
Abstract
The HIV-1 p6 Gag protein contains two late assembly (l-) domains that recruit proteins of the endosomal sorting complex required for transport (ESCRT) pathway to mediate membrane fission between the nascent virion and the cell membrane. It was recently demonstrated that mutation of the highly conserved Ser-40 to Phe (S40F) disturbs CA-SP1 processing, virus morphogenesis, and infectivity. It also causes the formation of filopodia-like structures, while virus release remains unaffected. Here, we show that the mutation S40F, but not the conservative mutation to Asp (S40D) or Asn (S40N), augments membrane association, K48-linked polyubiquitination, entry into the 26S proteasome, and, consequently, enhances MHC-I antigen presentation of Gag derived epitopes. Nuclear magnetic resonance (NMR) structure analyses revealed that the newly introduced Phe-40, together with Tyr-36, causes the formation of a hydrophobic patch at the C-terminal α-helix of p6, providing a molecular rationale for the enhanced membrane association of Gag observed in vitro and in HIV-1 expressing cells. The extended exposure of the S40F mutant to unidentified membrane-resident ubiquitin E3-ligases might trigger the polyubiquitination of Gag. The cumulative data support a previous model of a so far undefined property of p6, which, in addition to MA, acts as membrane targeting domain of Gag.
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13
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Ehrlich LS, Medina GN, Photiadis S, Whittredge PB, Watanabe S, Taraska JW, Carter CA. Tsg101 regulates PI(4,5)P2/Ca(2+) signaling for HIV-1 Gag assembly. Front Microbiol 2014; 5:234. [PMID: 24904548 PMCID: PMC4033031 DOI: 10.3389/fmicb.2014.00234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Accepted: 04/30/2014] [Indexed: 11/13/2022] Open
Abstract
Our previous studies identified the 1,4,5-inositol trisphosphate receptor (IP3R), a channel mediating release of Ca2+ from ER stores, as a cellular factor differentially associated with HIV-1 Gag that might facilitate ESCRT function in virus budding. Channel opening requires activation that is initiated by binding of 1,4,5-triphosphate (IP3), a product of phospholipase C (PLC)-mediated PI(4,5)P2 hydrolysis. The store emptying that follows stimulates store refilling which requires intact PI(4,5)P2. Raising cytosolic Ca2+ promotes viral particle production and our studies indicate that IP3R and the ER Ca2+ store are the physiological providers of Ca2+ for Gag assembly and release. Here, we show that Gag modulates ER store gating and refilling. Cells expressing Gag exhibited a higher cytosolic Ca2+ level originating from the ER store than control cells, suggesting that Gag induced release of store Ca2+. This property required the PTAP motif in Gag that recruits Tsg101, an ESCRT-1 component. Consistent with cytosolic Ca2+ elevation, Gag accumulation at the plasma membrane was found to require continuous IP3R activation. Like other IP3R channel modulators, Gag was detected in physical proximity to the ER and to endogenous IP3R, as indicated respectively by total internal reflection fluorescence (TIRF) and immunoelectron microscopy (IEM) or indirect immunofluorescence. Reciprocal co-immunoprecipitation suggested that Gag and IP3R proximity is favored when the PTAP motif in Gag is intact. Gag expression was also accompanied by increased PI(4,5)P2 accumulation at the plasma membrane, a condition favoring store refilling capacity. Supporting this notion, Gag particle production was impervious to treatment with 2-aminoethoxydiphenyl borate, an inhibitor of a refilling coupling interaction. In contrast, particle production by a Gag mutant lacking the PTAP motif was reduced. We conclude that a functional PTAP L domain, and by inference Tsg101 binding, confers Gag with an ability to modulate both ER store Ca2+ release and ER store refilling.
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Affiliation(s)
- Lorna S Ehrlich
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Gisselle N Medina
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Sara Photiadis
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Paul B Whittredge
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Susan Watanabe
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Carol A Carter
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
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