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Zeiger M, Pires M, Didier P, Vauchelles R, Mély Y, Boutant E, Real E. HIV-1 Gag Compact form Stabilized by Intramolecular Interactions is Crucial for Infectious Particle Production. J Mol Biol 2024; 436:168639. [PMID: 38838849 DOI: 10.1016/j.jmb.2024.168639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 05/29/2024] [Accepted: 05/30/2024] [Indexed: 06/07/2024]
Abstract
HIV-1 Gag polyprotein plays a pivotal role in assembly and budding of new particles, by specifically packaging two copies of viral gRNA in the host cell cytoplasm and selecting the cell plasma membrane for budding. Both gRNA and membrane selections are thought to be mediated by the compact form of Gag. This compact form binds to gRNA through both its matrix (MA) and nucleocapsid (NC) domains in the cytoplasm. At the plasma membrane, the membrane competes with gRNA for Gag binding, resulting in a transition to the extended form of Gag found in immature particles with MA bound to membrane lipids and NC to gRNA. The Gag compact form was previously evidenced in vitro. Here, we demonstrated the compact form of Gag in cells by confocal microscopy, using a bimolecular fluorescence complementation approach with a split-GFP bipartite system. Using wild-type Gag and Gag mutants, we showed that the compact form is highly dependent on the binding of MA and NC domains to RNA, as well as on interactions between MA and CA domains. In contrast, Gag multimerization appears to be less critical for the accumulation of the compact form. Finally, mutations altering the formation of Gag compact form led to a strong reduction in viral particle production and infectivity, revealing its key role in the production of infectious viral particles.
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Affiliation(s)
- Manon Zeiger
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Manuel Pires
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Pascal Didier
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Romain Vauchelles
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Yves Mély
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France.
| | - Emmanuel Boutant
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France.
| | - Eléonore Real
- UMR 7021, CNRS, Laboratoire de Bioimagerie et Pathologies - LBP, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France.
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2
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Duchon A, Hu WS. HIV-1 RNA genome packaging: it's G-rated. mBio 2024; 15:e0086123. [PMID: 38411060 PMCID: PMC11005445 DOI: 10.1128/mbio.00861-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024] Open
Abstract
A member of the Retroviridae, human immunodeficiency virus type 1 (HIV-1), uses the RNA genome packaged into nascent virions to transfer genetic information to its progeny. The genome packaging step is a highly regulated and extremely efficient process as a vast majority of virus particles contain two copies of full-length unspliced HIV-1 RNA that form a dimer. Thus, during virus assembly HIV-1 can identify and selectively encapsidate HIV-1 unspliced RNA from an abundant pool of cellular RNAs and various spliced HIV-1 RNAs. Several "G" features facilitate the packaging of a dimeric RNA genome. The viral polyprotein Gag orchestrates virus assembly and mediates RNA genome packaging. During this process, Gag preferentially binds unpaired guanosines within the highly structured 5' untranslated region (UTR) of HIV-1 RNA. In addition, the HIV-1 unspliced RNA provides a scaffold that promotes Gag:Gag interactions and virus assembly, thereby ensuring its packaging. Intriguingly, recent studies have shown that the use of different guanosines at the junction of U3 and R as transcription start sites results in HIV-1 unspliced RNA species with 99.9% identical sequences but dramatically distinct 5' UTR conformations. Consequently, one species of unspliced RNA is preferentially packaged over other nearly identical RNAs. These studies reveal how conformations affect the functions of HIV-1 RNA elements and the complex regulation of HIV-1 replication. In this review, we summarize cis- and trans-acting elements critical for HIV-1 RNA packaging, locations of Gag:RNA interactions that mediate genome encapsidation, and the effects of transcription start sites on the structure and packaging of HIV-1 RNA.
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Affiliation(s)
- Alice Duchon
- Viral Recombination Section, HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Maryland, USA
| | - Wei-Shau Hu
- Viral Recombination Section, HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Maryland, USA
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3
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Martin EW, Iserman C, Olety B, Mitrea DM, Klein IA. Biomolecular Condensates as Novel Antiviral Targets. J Mol Biol 2024; 436:168380. [PMID: 38061626 DOI: 10.1016/j.jmb.2023.168380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 11/23/2023] [Accepted: 11/30/2023] [Indexed: 12/24/2023]
Abstract
Viral infections pose a significant health risk worldwide. There is a pressing need for more effective antiviral drugs to combat emerging novel viruses and the reemergence of previously controlled viruses. Biomolecular condensates are crucial for viral replication and are promising targets for novel antiviral therapies. Herein, we review the role of biomolecular condensates in the viral replication cycle and discuss novel strategies to leverage condensate biology for antiviral drug discovery. Biomolecular condensates may also provide an opportunity to develop antivirals that are broad-spectrum or less prone to acquired drug resistance.
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4
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Sumner C, Ono A. The "basics" of HIV-1 assembly. PLoS Pathog 2024; 20:e1011937. [PMID: 38300900 PMCID: PMC10833515 DOI: 10.1371/journal.ppat.1011937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2024] Open
Affiliation(s)
- Christopher Sumner
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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5
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Tateishi H, Chinen T, Fukuda R, Radwan MO, Shimagaki K, Koga R, Masuda T, Okamoto Y, Sakamoto A, Misumi S, Otsuka M, Fujita M, Anraku K. HIV-1 Gag MA domain binds to cardiolipin in a binding mode distinct from virus assemble mediator PI(4,5)P 2. Chem Biol Drug Des 2024; 103:e14401. [PMID: 37985015 DOI: 10.1111/cbdd.14401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 10/16/2023] [Accepted: 11/07/2023] [Indexed: 11/22/2023]
Abstract
The human immunodeficiency virus type 1 (HIV-1) Gag protein is responsible for facilitating HIV-1 virion assembly and budding. Our study demonstrates that cardiolipin (CL), a component found in the inner mitochondrial membrane, exhibits the highest binding affinity to the N-terminal MA domain of the HIV-1 Gag protein within the lipid group of host cells. To assess this binding interaction, we synthesized short acyl chain derivatives of CL and employed surface plasmon resonance (SPR) analysis to determine the dissociation constants (Kd) for CL and the MA domain. Simultaneously, we examined the Kd of D-myo-phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 ) derivatives, known to play a crucial role in virion formation. Among all the derivatives, Tetra-C7 -CL exhibited the lowest Kd value (Kd = 30.8 ± 6.9 μM) for MA binding on the CL analog-immobilized sensorchip, indicating a higher affinity. Similarly, the Kd value of Di-C7 -PIP2 (Kd = 36.6 ± 4.7 μM) was the lowest on the PI(4,5)P2 analog-immobilized sensorchip. Thus, Tetra-C7 -CL binds to the MA domain using a distinct binding mode while displaying a comparable binding affinity to Di-C7 -PIP2. This discovery holds significant implications for comprehending the virological importance of CL-MA domain binding, such as its subcellular distribution, including mitochondrial translocation, and involvement in viral particle formation in concert with PI(4,5)P2 . Furthermore, this study has the potential to contribute to the development of drugs in the future.
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Affiliation(s)
- Hiroshi Tateishi
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takuma Chinen
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Ryota Fukuda
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Mohamed O Radwan
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
- Chemistry of Natural Compounds Department, Pharmaceutical and Drug Industries Research Division, National Research Centre, Cairo, Egypt
| | - Kazunori Shimagaki
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Ryoko Koga
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takashi Masuda
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Yoshinari Okamoto
- Department of Instrumental Analysis, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Arisa Sakamoto
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
- Department of Medical Technology, Kumamoto Health Science University, Kumamoto, Japan
| | - Shogo Misumi
- Department of Environmental and Molecular Health Sciences, Global Center for Natural Resources Sciences, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Masami Otsuka
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
- Science Farm Ltd., Kumamoto, Japan
| | - Mikako Fujita
- Medicinal and Biological Chemistry Science Farm Joint Research Laboratory, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kensaku Anraku
- Department of Medical Technology, Kumamoto Health Science University, Kumamoto, Japan
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6
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Monette A, Niu M, Maldonado RK, Chang J, Lambert GS, Flanagan JM, Cochrane A, Parent LJ, Mouland AJ. Influence of HIV-1 Genomic RNA on the Formation of Gag Biomolecular Condensates. J Mol Biol 2023; 435:168190. [PMID: 37385580 PMCID: PMC10838171 DOI: 10.1016/j.jmb.2023.168190] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 06/18/2023] [Accepted: 06/20/2023] [Indexed: 07/01/2023]
Abstract
Biomolecular condensates (BMCs) play an important role in the replication of a growing number of viruses, but many important mechanistic details remain to be elucidated. Previously, we demonstrated that the pan-retroviral nucleocapsid (NC) and HIV-1 pr55Gag (Gag) proteins phase separate into condensates, and that HIV-1 protease (PR)-mediated maturation of Gag and Gag-Pol precursor proteins yields self-assembling BMCs that have HIV-1 core architecture. Using biochemical and imaging techniques, we aimed to further characterize the phase separation of HIV-1 Gag by determining which of its intrinsically disordered regions (IDRs) influence the formation of BMCs, and how the HIV-1 viral genomic RNA (gRNA) could influence BMC abundance and size. We found that mutations in the Gag matrix (MA) domain or the NC zinc finger motifs altered condensate number and size in a salt-dependent manner. Gag BMCs were also bimodally influenced by the gRNA, with a condensate-promoting regime at lower protein concentrations and a gel dissolution at higher protein concentrations. Interestingly, incubation of Gag with CD4+ T cell nuclear lysates led to the formation of larger BMCs compared to much smaller ones observed in the presence of cytoplasmic lysates. These findings suggest that the composition and properties of Gag-containing BMCs may be altered by differential association of host factors in nuclear and cytosolic compartments during virus assembly. This study significantly advances our understanding of HIV-1 Gag BMC formation and provides a foundation for future therapeutic targeting of virion assembly.
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Affiliation(s)
- Anne Monette
- Lady Davis Institute at the Jewish General Hospital, Montréal, Québec H3T 1E2, Canada
| | - Meijuan Niu
- Lady Davis Institute at the Jewish General Hospital, Montréal, Québec H3T 1E2, Canada
| | - Rebecca Kaddis Maldonado
- Department of Medicine, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States; Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
| | - Jordan Chang
- Department of Medicine, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
| | - Gregory S Lambert
- Department of Medicine, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
| | - John M Flanagan
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
| | - Alan Cochrane
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Leslie J Parent
- Department of Medicine, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States; Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey, PA 17033, United States.
| | - Andrew J Mouland
- Lady Davis Institute at the Jewish General Hospital, Montréal, Québec H3T 1E2, Canada; Department of Medicine, McGill University, Montréal, Québec H4A 3J1, Canada.
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7
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Monette A, Niu M, Maldonado RK, Chang J, Lambert GS, Flanagan JM, Cochrane A, Parent LJ, Mouland AJ. Influence of HIV-1 genomic RNA on the formation of Gag biomolecular condensates. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.23.529585. [PMID: 36865181 PMCID: PMC9980109 DOI: 10.1101/2023.02.23.529585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Biomolecular condensates (BMCs) play an important role in the replication of a growing number of viruses, but many important mechanistic details remain to be elucidated. Previously, we demonstrated that pan-retroviral nucleocapsid (NC) and the HIV-1 pr55 Gag (Gag) proteins phase separate into condensates, and that HIV-1 protease (PR)-mediated maturation of Gag and Gag-Pol precursor proteins yield self-assembling BMCs having HIV-1 core architecture. Using biochemical and imaging techniques, we aimed to further characterize the phase separation of HIV-1 Gag by determining which of its intrinsically disordered regions (IDRs) influence the formation of BMCs and how the HIV-1 viral genomic RNA (gRNA) could influence BMC abundance and size. We found that mutations in the Gag matrix (MA) domain or the NC zinc finger motifs altered condensate number and size in a salt-dependent manner. Gag BMCs were also bimodally influenced by the gRNA, with a condensate-promoting regime at lower protein concentrations and a gel dissolution at higher protein concentrations. Interestingly, incubation of Gag with CD4 + T cell nuclear lysates led to the formation of larger BMCs as compared to much smaller ones observed in the presence of cytoplasmic lysates. These findings suggests that the composition and properties of Gag-containing BMCs may be altered by differential association of host factors in nuclear and cytosolic compartments during virus assembly. This study significantly advances our understanding of HIV-1 Gag BMC formation and provides a foundation for future therapeutic targeting of virion assembly.
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8
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Abstract
The intracellular parasite Toxoplasma gondii adapts to diverse host cell environments within a replicative compartment that is heavily decorated by secreted proteins. In an attempt to identify novel parasite secreted proteins that influence host cell activity, we identified and characterized a transmembrane dense granule protein dubbed GRA64 (TGME49_202620). We found that GRA64 is on the parasitophorous vacuolar membrane (PVM) and is partially exposed to the host cell cytoplasm in both tachyzoite and bradyzoite parasitophorous vacuoles. Using co-immunoprecipitation and proximity-based biotinylation approaches, we demonstrated that GRA64 appears to interact with components of the host endosomal sorting complexes required for transport (ESCRT). Genetic disruption of GRA64 does not affect acute Toxoplasma virulence or encystation in mice, as observed via tissue cyst burdens in mice during chronic infection. However, ultrastructural analysis of Δgra64 tissue cysts using electron tomography revealed enlarged vesicular structures underneath the cyst membrane, suggesting a role for GRA64 in organizing the recruitment of ESCRT proteins and subsequent intracystic vesicle formation. This study uncovers a novel host-parasite interaction that contributes to an emerging paradigm in which specific host ESCRT proteins are recruited to the limiting membranes (PVMs) of tachyzoite and bradyzoite vacuoles formed during acute and chronic Toxoplasma infection. IMPORTANCE Toxoplasma gondii is a widespread foodborne parasite that causes congenital disease and life-threatening complications in immunocompromised individuals. Part of this parasite's success lies in its ability to infect diverse organisms and host cells and to persist as a latent infection within parasite-constructed structures called tissue cysts. In this study, we characterized a protein that is secreted by T. gondii into its parasitophorous vacuole during intracellular infection, which we dub GRA64. On the vacuolar membrane, this protein is exposed to the host cell cytosol and interacts with specific host ESCRT proteins. Parasites lacking the GRA64 protein exhibit ultrastructural changes in tissue cysts during chronic infection. This study lays the foundation for future studies on the mechanics and consequences of host ESCRT-parasite protein interactions.
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9
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Herrmann D, Hanson HM, Zhou LW, Addabbo R, Willkomm NA, Angert I, Mueller JD, Mansky LM, Saad JS. Molecular Determinants of Human T-cell Leukemia Virus Type 1 Gag Targeting to the Plasma Membrane for Assembly. J Mol Biol 2022; 434:167609. [PMID: 35490898 PMCID: PMC10557380 DOI: 10.1016/j.jmb.2022.167609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/20/2022] [Accepted: 04/23/2022] [Indexed: 01/10/2023]
Abstract
Assembly of human T-cell leukemia virus type 1 (HTLV-1) particles is initiated by the trafficking of virally encoded Gag polyproteins to the inner leaflet of the plasma membrane (PM). Gag-PM interactions are mediated by the matrix (MA) domain, which contains a myristoyl group (myr) and a basic patch formed by lysine and arginine residues. For many retroviruses, Gag-PM interactions are mediated by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]; however, previous studies suggested that HTLV-1 Gag-PM interactions and therefore virus assembly are less dependent on PI(4,5)P2. We have recently shown that PI(4,5)P2 binds directly to HTLV-1 unmyristoylated MA [myr(-)MA] and that myr(-)MA binding to membranes is significantly enhanced by inclusion of phosphatidylserine (PS) and PI(4,5)P2. Herein, we employed structural, biophysical, biochemical, mutagenesis, and cell-based assays to identify residues involved in MA-membrane interactions. Our data revealed that the lysine-rich motif (Lys47, Lys48, and Lys51) constitutes the primary PI(4,5)P2-binding site. Furthermore, we show that arginine residues 3, 7, 14 and 17 located in the unstructured N-terminus are essential for MA binding to membranes containing PS and/or PI(4,5)P2. Substitution of lysine and arginine residues severely attenuated virus-like particle production, but only the lysine residues could be clearly correlated with reduced PM binding. These results support a mechanism by which HTLV-1 Gag targeting to the PM is mediated by a trio engagement of the myr group, Arg-rich and Lys-rich motifs. These findings advance our understanding of a key step in retroviral particle assembly.
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Affiliation(s)
- Dominik Herrmann
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - Heather M Hanson
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States
| | - Lynne W Zhou
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States
| | - Rayna Addabbo
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States
| | - Nora A Willkomm
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States
| | - Isaac Angert
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States
| | - Joachim D Mueller
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, United States
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, United States.
| | - Jamil S Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
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10
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Sumner C, Ono A. Relationship between HIV-1 Gag Multimerization and Membrane Binding. Viruses 2022; 14:v14030622. [PMID: 35337029 PMCID: PMC8949992 DOI: 10.3390/v14030622] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/06/2022] [Accepted: 03/09/2022] [Indexed: 12/11/2022] Open
Abstract
HIV-1 viral particle assembly occurs specifically at the plasma membrane and is driven primarily by the viral polyprotein Gag. Selective association of Gag with the plasma membrane is a key step in the viral assembly pathway, which is traditionally attributed to the MA domain. MA regulates specific plasma membrane binding through two primary mechanisms including: (1) specific interaction of the MA highly basic region (HBR) with the plasma membrane phospholipid phosphatidylinositol (4,5) bisphosphate [PI(4,5)P2], and (2) tRNA binding to the MA HBR, which prevents Gag association with non-PI(4,5)P2 containing membranes. Gag multimerization, driven by both CA–CA inter-protein interactions and NC-RNA binding, also plays an essential role in viral particle assembly, mediating the establishment and growth of the immature Gag lattice on the plasma membrane. In addition to these functions, the multimerization of HIV-1 Gag has also been demonstrated to enhance its membrane binding activity through the MA domain. This review provides an overview of the mechanisms regulating Gag membrane binding through the MA domain and multimerization through the CA and NC domains, and examines how these two functions are intertwined, allowing for multimerization mediated enhancement of Gag membrane binding.
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11
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Sumner C, Kotani O, Liu S, Musier-Forsyth K, Sato H, Ono A. Molecular Determinants in tRNA D-arm Required for Inhibition of HIV-1 Gag Membrane Binding. J Mol Biol 2022; 434:167390. [PMID: 34883117 PMCID: PMC8752508 DOI: 10.1016/j.jmb.2021.167390] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 11/23/2021] [Accepted: 11/30/2021] [Indexed: 02/01/2023]
Abstract
Plasma-membrane-specific localization of Gag, an essential step in HIV-1 particle assembly, is regulated by the interaction of the Gag MA domain with PI(4,5)P2 and tRNA-mediated inhibition of non-specific or premature membrane binding. Different tRNAs inhibit PI(4,5)P2-independent membrane binding to varying degrees in vitro; however, the structural determinants for this difference remain unknown. Here we demonstrate that membrane binding of full-length Gag synthesized in vitro using reticulocyte lysates is inhibited when RNAs that contain the anticodon arm of tRNAPro, but not that of tRNALys3, are added exogenously. In contrast, in the context of a liposome binding assay in which the effects of tRNAs on purified MA were tested, full-length tRNALys3 showed greater inhibition of MA membrane binding than full-length tRNAPro. While transplantation of the D loop sequence of tRNALys3 into tRNAPro resulted in a modest increase in the inhibitory effect relative to WT tRNAPro, replacing the entire D arm sequence with that of tRNALys3 was necessary to confer the full inhibitory effects upon tRNAPro. Together, these results demonstrate that the D arm of tRNALys3 is a major determinant of strong inhibition of MA membrane binding and that this inhibitory effect requires not only the D loop, which was recently reported to contact the MA highly basic region, but the loop sequence in the context of the D arm structure.
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Affiliation(s)
- Christopher Sumner
- Dept. of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, United States
| | - Osamu Kotani
- Center for Pathogen Genomics, National Institute of Infectious Diseases, Tokyo, Japan
| | - Shuohui Liu
- Dept. of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus, OH, United States
| | - Karin Musier-Forsyth
- Dept. of Chemistry and Biochemistry, Center for Retrovirus Research, and Center for RNA Biology, The Ohio State University, Columbus, OH, United States
| | - Hironori Sato
- Center for Pathogen Genomics, National Institute of Infectious Diseases, Tokyo, Japan
| | - Akira Ono
- Dept. of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, United States
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12
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Rivera-Cuevas Y, Mayoral J, Di Cristina M, Lawrence ALE, Olafsson EB, Patel RK, Thornhill D, Waldman BS, Ono A, Sexton JZ, Lourido S, Weiss LM, Carruthers VB. Toxoplasma gondii exploits the host ESCRT machinery for parasite uptake of host cytosolic proteins. PLoS Pathog 2021; 17:e1010138. [PMID: 34898650 PMCID: PMC8700025 DOI: 10.1371/journal.ppat.1010138] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 12/23/2021] [Accepted: 11/23/2021] [Indexed: 11/18/2022] Open
Abstract
Toxoplasma gondii is a master manipulator capable of effectively siphoning the resources from the host cell for its intracellular subsistence. However, the molecular underpinnings of how the parasite gains resources from its host remain largely unknown. Residing within a non-fusogenic parasitophorous vacuole (PV), the parasite must acquire resources across the limiting membrane of its replicative niche, which is decorated with parasite proteins including those secreted from dense granules. We discovered a role for the host Endosomal Sorting Complex Required for Transport (ESCRT) machinery in host cytosolic protein uptake by T. gondii by disrupting host ESCRT function. We identified the transmembrane dense granule protein TgGRA14, which contains motifs homologous to the late domain motifs of HIV-1 Gag, as a candidate for the recruitment of the host ESCRT machinery to the PV membrane. Using an HIV-1 virus-like particle (VLP) release assay, we found that the motif-containing portion of TgGRA14 is sufficient to substitute for HIV-1 Gag late domain to mediate ESCRT-dependent VLP budding. We also show that TgGRA14 is proximal to and interacts with host ESCRT components and other dense granule proteins during infection. Furthermore, analysis of TgGRA14-deficient parasites revealed a marked reduction in ingestion of a host cytosolic protein compared to WT parasites. Thus, we propose a model in which T. gondii recruits the host ESCRT machinery to the PV where it can interact with TgGRA14 for the internalization of host cytosolic proteins across the PV membrane (PVM). These findings provide new insight into how T. gondii accesses contents of the host cytosol by exploiting a key pathway for vesicular budding and membrane scission.
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Affiliation(s)
- Yolanda Rivera-Cuevas
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Joshua Mayoral
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Manlio Di Cristina
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Anna-Lisa E. Lawrence
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Einar B. Olafsson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Romir K. Patel
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Dishari Thornhill
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Benjamin S. Waldman
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jonathan Z. Sexton
- Department of Medicinal Chemistry, College of Pharmacy, Ann Arbor, Michigan, United States of America
| | - Sebastian Lourido
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Louis M. Weiss
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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13
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Murakami T, Ono A. Roles of Virion-Incorporated CD162 (PSGL-1), CD43, and CD44 in HIV-1 Infection of T Cells. Viruses 2021; 13:v13101935. [PMID: 34696365 PMCID: PMC8541244 DOI: 10.3390/v13101935] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/18/2021] [Accepted: 09/22/2021] [Indexed: 11/16/2022] Open
Abstract
Nascent HIV-1 particles incorporate the viral envelope glycoprotein and multiple host transmembrane proteins during assembly at the plasma membrane. At least some of these host transmembrane proteins on the surface of virions are reported as pro-viral factors that enhance virus attachment to target cells or facilitate trans-infection of CD4+ T cells via interactions with non-T cells. In addition to the pro-viral factors, anti-viral transmembrane proteins are incorporated into progeny virions. These virion-incorporated transmembrane proteins inhibit HIV-1 entry at the point of attachment and fusion. In infected polarized CD4+ T cells, HIV-1 Gag localizes to a rear-end protrusion known as the uropod. Regardless of cell polarization, Gag colocalizes with and promotes the virion incorporation of a subset of uropod-directed host transmembrane proteins, including CD162, CD43, and CD44. Until recently, the functions of these virion-incorporated proteins had not been clear. Here, we review the recent findings about the roles played by virion-incorporated CD162, CD43, and CD44 in HIV-1 spread to CD4+ T cells.
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14
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Herrmann D, Zhou LW, Hanson HM, Willkomm NA, Mansky LM, Saad JS. Structural Insights into the Mechanism of Human T-cell Leukemia Virus Type 1 Gag Targeting to the Plasma Membrane for Assembly. J Mol Biol 2021; 433:167161. [PMID: 34298060 PMCID: PMC8453114 DOI: 10.1016/j.jmb.2021.167161] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/10/2021] [Accepted: 07/12/2021] [Indexed: 01/10/2023]
Abstract
Retroviral Gag targeting to the plasma membrane (PM) for assembly is mediated by the N-terminal matrix (MA) domain. For many retroviruses, Gag-PM interaction is dependent on phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). However, it has been shown that for human T-cell leukemia virus type 1 (HTLV-1), Gag binding to membranes is less dependent on PI(4,5)P2 than HIV-1, suggesting that other factors may modulate Gag assembly. To elucidate the mechanism by which HTLV-1 Gag binds to the PM, we employed NMR techniques to determine the structure of unmyristoylated MA (myr(-)MA) and to characterize its interactions with lipids and liposomes. The MA structure consists of four α-helices and unstructured N- and C-termini. We show that myr(-)MA binds to PI(4,5)P2 via the polar head and that binding to inositol phosphates (IPs) is significantly enhanced by increasing the number of phosphate groups on the inositol ring, indicating that the MA-IP binding is governed by charge-charge interactions. The IP binding site was mapped to a well-defined basic patch formed by lysine and arginine residues. Using an NMR-based liposome binding assay, we show that PI(4,5)P2and phosphatidylserine enhance myr(-)MA binding in a synergistic fashion. Confocal microscopy data revealed formation of puncta on the PM of Gag expressing cells. However, G2A-Gag mutant, lacking myristoylation, is diffuse and cytoplasmic. These results suggest that although myr(-)MA binds to membranes, myristoylation appears to be key for formation of HTLV-1 Gag puncta on the PM. Altogether, these findings advance our understanding of a key mechanism in retroviral assembly.
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Affiliation(s)
- Dominik Herrmann
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lynne W Zhou
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Heather M Hanson
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
| | - Nora A Willkomm
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN 55455, USA
| | - Jamil S Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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15
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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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16
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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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17
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Rendezvous at Plasma Membrane: Cellular Lipids and tRNA Set up Sites of HIV-1 Particle Assembly and Incorporation of Host Transmembrane Proteins. Viruses 2020; 12:v12080842. [PMID: 32752131 PMCID: PMC7472227 DOI: 10.3390/v12080842] [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: 07/04/2020] [Revised: 07/20/2020] [Accepted: 07/24/2020] [Indexed: 12/28/2022] Open
Abstract
The HIV-1 structural polyprotein Gag drives the virus particle assembly specifically at the plasma membrane (PM). During this process, the nascent virion incorporates specific subsets of cellular lipids and host membrane proteins, in addition to viral glycoproteins and viral genomic RNA. Gag binding to the PM is regulated by cellular factors, including PM-specific phospholipid PI(4,5)P2 and tRNAs, both of which bind the highly basic region in the matrix domain of Gag. In this article, we review our current understanding of the roles played by cellular lipids and tRNAs in specific localization of HIV-1 Gag to the PM. Furthermore, we examine the effects of PM-bound Gag on the organization of the PM bilayer and discuss how the reorganization of the PM at the virus assembly site potentially contributes to the enrichment of host transmembrane proteins in the HIV-1 particle. Since some of these host transmembrane proteins alter release, attachment, or infectivity of the nascent virions, the mechanism of Gag targeting to the PM and the nature of virus assembly sites have major implications in virus spread.
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18
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Boutant E, Bonzi J, Anton H, Nasim MB, Cathagne R, Réal E, Dujardin D, Carl P, Didier P, Paillart JC, Marquet R, Mély Y, de Rocquigny H, Bernacchi S. Zinc Fingers in HIV-1 Gag Precursor Are Not Equivalent for gRNA Recruitment at the Plasma Membrane. Biophys J 2020; 119:419-433. [PMID: 32574557 PMCID: PMC7376094 DOI: 10.1016/j.bpj.2020.05.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/15/2020] [Accepted: 05/06/2020] [Indexed: 01/16/2023] Open
Abstract
The human immunodeficiency virus type 1 Gag precursor specifically selects the unspliced viral genomic RNA (gRNA) from the bulk of cellular and spliced viral RNAs via its nucleocapsid (NC) domain and drives gRNA encapsidation at the plasma membrane (PM). To further identify the determinants governing the intracellular trafficking of Gag-gRNA complexes and their accumulation at the PM, we compared, in living and fixed cells, the interactions between gRNA and wild-type Gag or Gag mutants carrying deletions in NC zinc fingers (ZFs) or a nonmyristoylated version of Gag. Our data showed that the deletion of both ZFs simultaneously or the complete NC domain completely abolished intracytoplasmic Gag-gRNA interactions. Deletion of either ZF delayed the delivery of gRNA to the PM but did not prevent Gag-gRNA interactions in the cytoplasm, indicating that the two ZFs display redundant roles in this respect. However, ZF2 played a more prominent role than ZF1 in the accumulation of the ribonucleoprotein complexes at the PM. Finally, the myristate group, which is mandatory for anchoring the complexes at the PM, was found to be dispensable for the association of Gag with the gRNA in the cytosol.
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Affiliation(s)
- Emmanuel Boutant
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France.
| | - Jeremy Bonzi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France
| | - Halina Anton
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Maaz Bin Nasim
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Raphael Cathagne
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Eléonore Réal
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Denis Dujardin
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Philippe Carl
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Pascal Didier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Jean-Christophe Paillart
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France
| | - Roland Marquet
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France
| | - Yves Mély
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Hugues de Rocquigny
- Morphogenèse et Antigénicité du VIH et des Virus des Hépatites, Inserm - U1259 MAVIVH, Tours, France.
| | - Serena Bernacchi
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France.
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19
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Junková P, Pleskot R, Prchal J, Sýs J, Ruml T. Differences and commonalities in plasma membrane recruitment of the two morphogenetically distinct retroviruses HIV-1 and MMTV. J Biol Chem 2020; 295:8819-8833. [PMID: 32385109 DOI: 10.1074/jbc.ra119.011991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 05/05/2020] [Indexed: 11/06/2022] Open
Abstract
Retroviral Gag polyproteins are targeted to the inner leaflet of the plasma membrane through their N-terminal matrix (MA) domain. Because retroviruses of different morphogenetic types assemble their immature particles in distinct regions of the host cell, the mechanism of MA-mediated plasma membrane targeting differs among distinct retroviral morphogenetic types. Here, we focused on possible mechanistic differences of the MA-mediated plasma membrane targeting of the B-type mouse mammary tumor virus (MMTV) and C-type HIV-1, which assemble in the cytoplasm and at the plasma membrane, respectively. Molecular dynamics simulations, together with surface mapping, indicated that, similarly to HIV-1, MMTV uses a myristic switch to anchor the MA to the membrane and electrostatically interacts with phosphatidylinositol 4,5-bisphosphate to stabilize MA orientation. We observed that the affinity of MMTV MA to the membrane is lower than that of HIV-1 MA, possibly related to their different topologies and the number of basic residues in the highly basic MA region. The latter probably reflects the requirement of C-type retroviruses for tighter membrane binding, essential for assembly, unlike for D/B-type retroviruses, which assemble in the cytoplasm. A comparison of the membrane topology of the HIV-1 MA, using the surface-mapping method and molecular dynamics simulations, revealed that the residues at the HIV-1 MA C terminus help stabilize protein-protein interactions within the HIV-1 MA lattice at the plasma membrane. In summary, HIV-1 and MMTV share common features such as membrane binding of the MA via hydrophobic interactions and exhibit several differences, including lower membrane affinity of MMTV MA.
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Affiliation(s)
- Petra Junková
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Roman Pleskot
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium; VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Jan Prchal
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic
| | - Jakub Sýs
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic
| | - Tomáš Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Czech Republic.
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20
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Distinct Contributions of Different Domains within the HIV-1 Gag Polyprotein to Specific and Nonspecific Interactions with RNA. Viruses 2020; 12:v12040394. [PMID: 32252233 PMCID: PMC7232488 DOI: 10.3390/v12040394] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/31/2020] [Accepted: 03/31/2020] [Indexed: 11/17/2022] Open
Abstract
Viral genomic RNA is packaged into virions with high specificity and selectivity. However, in vitro the Gag specificity towards viral RNA is obscured when measured in buffers containing physiological salt. Interestingly, when the binding is challenged by increased salt concentration, the addition of competing RNAs, or introducing mutations to Gag protein, the specificity towards viral RNA becomes detectable. The objective of this work was to examine the contributions of the individual HIV-1 Gag polyprotein domains to nonspecific and specific RNA binding and stability of the initial protein-RNA complexes. Using a panel of Gag proteins with mutations disabling different Gag-Gag or Gag-RNA interfaces, we investigated the distinct contributions of individual domains which distinguish the binding to viral and nonviral RNA by measuring the binding of the proteins to RNAs. We measured the binding affinity in near-physiological salt concentration, and then challenged the binding by increasing the ionic strength to suppress the electrostatic interactions and reveal the contribution of specific Gag–RNA and Gag–Gag interactions. Surprisingly, we observed that Gag dimerization and the highly basic region in the matrix domain contribute significantly to the specificity of viral RNA binding.
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21
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Relationships between MA-RNA Binding in Cells and Suppression of HIV-1 Gag Mislocalization to Intracellular Membranes. J Virol 2019; 93:JVI.00756-19. [PMID: 31511376 DOI: 10.1128/jvi.00756-19] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 09/02/2019] [Indexed: 12/24/2022] Open
Abstract
The HIV-1 Gag matrix (MA) domain mediates the localization of Gag to the plasma membrane (PM), the site for infectious virion assembly. The MA highly basic region (MA-HBR) interacts with phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2], a PM-specific acidic lipid. The MA-HBR also binds RNAs. To test whether acidic lipids alone determine PM-specific localization of Gag or whether MA-RNA binding also plays a role, we compared a panel of MA-HBR mutants that contain two types of substitutions at MA residues 25 and 26 or residues 29 and 31: Lys→Arg (KR) (25/26KR and 29/31KR) and Lys→Thr (KT) (25/26KT and 29/31KT). Consistent with the importance of the HBR charge in RNA binding, both KT mutants failed to bind RNA via MA efficiently, unlike the corresponding KR mutants. Both 25/26KT Gag-yellow fluorescent protein (YFP) and 29/31KT Gag-YFP bound nonspecifically to the PM and intracellular membranes, presumably via the myristoyl moiety and remaining MA basic residues. In contrast, 25/26KR Gag-YFP bound specifically to the PM, suggesting a role for the total positive charge and/or MA-bound RNA in navigating Gag to the PM. Unlike 29/31KT Gag-YFP, 29/31KR Gag-YFP was predominantly cytosolic and showed little intracellular membrane binding despite having a higher HBR charge. Therefore, it is likely that MA-RNA binding blocks promiscuous Gag membrane binding in cells. Notably, the introduction of a heterologous multimerization domain restored PI(4,5)P2-dependent PM-specific localization for 29/31KR Gag-YFP, suggesting that the blocking of PM binding is more readily reversed than that of intracellular membrane binding. Altogether, these cell-based data support a model in which MA-RNA binding ensures PM-specific localization of Gag via suppression of nonspecific membrane binding.IMPORTANCE The PM-specific localization of HIV-1 Gag is a crucial early step in infectious progeny production. The interaction between the MA highly basic region (MA-HBR) of Gag and the PM-specific lipid PI(4,5)P2 is critical for Gag localization to the PM. Additionally, in vitro evidence has indicated that MA-RNA binding prevents nonspecific binding of Gag to non-PI(4,5)P2-containing membranes. However, cell-based evidence supporting a role for HIV-1 MA-RNA binding in PM-specific subcellular localization has been scarce; thus, it remained possible that in cells, just the high basic charge or the PI(4,5)P2 binding ability is sufficient for MA to direct Gag specifically to the PM. The present study reveals for the first time an excellent correlation between RNA binding of the MA-HBR and inhibition of promiscuous Gag localization, both within the cells, and thereby provides cell-based evidence supporting a mechanism in which HIV-1 MA binding to RNA ensures the specific localization of Gag to the PM.
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