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Hu Y, Delviks-Frankenberry KA, Wu C, Arizaga F, Pathak VK, Xiong Y. Structural insights into PPP2R5A degradation by HIV-1 Vif. Nat Struct Mol Biol 2024:10.1038/s41594-024-01314-6. [PMID: 38789685 DOI: 10.1038/s41594-024-01314-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 04/11/2024] [Indexed: 05/26/2024]
Abstract
HIV-1 Vif recruits host cullin-RING-E3 ubiquitin ligase and CBFβ to degrade the cellular APOBEC3 antiviral proteins through diverse interactions. Recent evidence has shown that Vif also degrades the regulatory subunits PPP2R5(A-E) of cellular protein phosphatase 2A to induce G2/M cell cycle arrest. As PPP2R5 proteins bear no functional or structural resemblance to A3s, it is unclear how Vif can recognize different sets of proteins. Here we report the cryogenic-electron microscopy structure of PPP2R5A in complex with HIV-1 Vif-CBFβ-elongin B-elongin C at 3.58 Å resolution. The structure shows PPP2R5A binds across the Vif molecule, with biochemical and cellular studies confirming a distinct Vif-PPP2R5A interface that partially overlaps with those for A3s. Vif also blocks a canonical PPP2R5A substrate-binding site, indicating that it suppresses the phosphatase activities through both degradation-dependent and degradation-independent mechanisms. Our work identifies critical Vif motifs regulating the recognition of diverse A3 and PPP2R5A substrates, whereby disruption of these host-virus protein interactions could serve as potential targets for HIV-1 therapeutics.
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Affiliation(s)
- Yingxia Hu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Krista A Delviks-Frankenberry
- Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, USA
| | - Chunxiang Wu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Fidel Arizaga
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Vinay K Pathak
- Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD, USA.
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
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2
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Ito F, Alvarez-Cabrera AL, Kim K, Zhou ZH, Chen XS. Structural basis of HIV-1 Vif-mediated E3 ligase targeting of host APOBEC3H. Nat Commun 2023; 14:5241. [PMID: 37640699 PMCID: PMC10462622 DOI: 10.1038/s41467-023-40955-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 08/17/2023] [Indexed: 08/31/2023] Open
Abstract
Human APOBEC3 (A3) cytidine deaminases are antiviral factors that are particularly potent against retroviruses. As a countermeasure, HIV-1 uses a viral infectivity factor (Vif) to target specific human A3s for proteasomal degradation. Vif recruits cellular transcription cofactor CBF-β and Cullin-5 (CUL5) RING E3 ubiquitin ligase to bind different A3s distinctively, but how this is accomplished remains unclear in the absence of the atomic structure of the complex. Here, we present the cryo-EM structures of HIV-1 Vif in complex with human A3H, CBF-β and components of CUL5 ubiquitin ligase (CUL5, ELOB, and ELOC). Vif nucleates the entire complex by directly binding four human proteins, A3H, CBF-β, CUL5, and ELOC. The structures reveal a large interface area between A3H and Vif, primarily mediated by an α-helical side of A3H and a five-stranded β-sheet of Vif. This A3H-Vif interface unveils the basis for sensitivity-modulating polymorphism of both proteins, including a previously reported gain-of-function mutation in Vif isolated from HIV/AIDS patients. Our structural and functional results provide insights into the remarkable interplay between HIV and humans and would inform development efforts for anti-HIV therapeutics.
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Affiliation(s)
- Fumiaki Ito
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA90095, USA
| | - Ana L Alvarez-Cabrera
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA90095, USA
| | - Kyumin Kim
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA90095, USA
- California NanoSystems Institute, University of California, Los Angeles, CA90095, USA
| | - Xiaojiang S Chen
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
- Genetic, Molecular and Cellular Biology Program, Keck School of Medicine, University of Southern California, Los Angeles, CA90089, USA.
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA90089, USA.
- Center of Excellence in NanoBiophysics, University of Southern California, Los Angeles, CA90089, USA.
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3
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Kouno T, Shibata S, Shigematsu M, Hyun J, Kim TG, Matsuo H, Wolf M. Structural insights into RNA bridging between HIV-1 Vif and antiviral factor APOBEC3G. Nat Commun 2023; 14:4037. [PMID: 37419875 PMCID: PMC10328928 DOI: 10.1038/s41467-023-39796-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 06/29/2023] [Indexed: 07/09/2023] Open
Abstract
Great effort has been devoted to discovering the basis of A3G-Vif interaction, the key event of HIV's counteraction mechanism to evade antiviral innate immune response. Here we show reconstitution of the A3G-Vif complex and subsequent A3G ubiquitination in vitro and report the cryo-EM structure of the A3G-Vif complex at 2.8 Å resolution using solubility-enhanced variants of A3G and Vif. We present an atomic model of the A3G-Vif interface, which assembles via known amino acid determinants. This assembly is not achieved by protein-protein interaction alone, but also involves RNA. The cryo-EM structure and in vitro ubiquitination assays identify an adenine/guanine base preference for the interaction and a unique Vif-ribose contact. This establishes the biological significance of an RNA ligand. Further assessment of interactions between A3G, Vif, and RNA ligands show that the A3G-Vif assembly and subsequent ubiquitination can be controlled by amino acid mutations at the interface or by polynucleotide modification, suggesting that a specific chemical moiety would be a promising pharmacophore to inhibit the A3G-Vif interaction.
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Affiliation(s)
- Takahide Kouno
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan.
| | - Satoshi Shibata
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan
- Division of Bacteriology, Department of Microbiology and Immunology, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago-shi, Tottori, 683-8503, Japan
| | - Megumi Shigematsu
- Computational Medicine Center, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Jaekyung Hyun
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan
- School of Pharmacy, Sungkyunkwan University, Suwon-si, Gyeonggi-do, 16419, Republic of Korea
| | - Tae Gyun Kim
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan
- Department of Efficacy Evaluation, Innovation Center for Vaccine Industry, Gyeongbuk Institute for Bio Industry, Gyeongsanbuk-do, 36618, Republic of Korea
| | - Hiroshi Matsuo
- Cancer Innovation Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Matthias Wolf
- Molecular Cryo-Electron Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan.
- Institute of Biological Chemistry, Academia Sinica, 128 Academia Road Sec. 2, 115, Taipei, Taiwan.
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4
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Li YL, Langley CA, Azumaya CM, Echeverria I, Chesarino NM, Emerman M, Cheng Y, Gross JD. The structural basis for HIV-1 Vif antagonism of human APOBEC3G. Nature 2023; 615:728-733. [PMID: 36754086 PMCID: PMC10033410 DOI: 10.1038/s41586-023-05779-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 02/02/2023] [Indexed: 02/10/2023]
Abstract
The APOBEC3 (A3) proteins are host antiviral cellular proteins that hypermutate the viral genome of diverse viral families. In retroviruses, this process requires A3 packaging into viral particles1-4. The lentiviruses encode a protein, Vif, that antagonizes A3 family members by targeting them for degradation. Diversification of A3 allows host escape from Vif whereas adaptations in Vif enable cross-species transmission of primate lentiviruses. How this 'molecular arms race' plays out at the structural level is unknown. Here, we report the cryogenic electron microscopy structure of human APOBEC3G (A3G) bound to HIV-1 Vif, and the hijacked cellular proteins that promote ubiquitin-mediated proteolysis. A small surface explains the molecular arms race, including a cross-species transmission event that led to the birth of HIV-1. Unexpectedly, we find that RNA is a molecular glue for the Vif-A3G interaction, enabling Vif to repress A3G by ubiquitin-dependent and -independent mechanisms. Our results suggest a model in which Vif antagonizes A3G by intercepting it in its most dangerous form for the virus-when bound to RNA and on the pathway to packaging-to prevent viral restriction. By engaging essential surfaces required for restriction, Vif exploits a vulnerability in A3G, suggesting a general mechanism by which RNA binding helps to position key residues necessary for viral antagonism of a host antiviral gene.
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Affiliation(s)
- Yen-Li Li
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA
| | - Caroline A Langley
- Divisions of Human Biology and Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA, USA
| | - Caleigh M Azumaya
- Fred Hutchinson Cancer Center, Electron Microscopy Shared Resource, Seattle, WA, USA
| | - Ignacia Echeverria
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA
- Quantitative Bioscience Institute, University of California, San Francisco, CA, USA
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
| | - Nicholas M Chesarino
- Divisions of Human Biology and Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Michael Emerman
- Divisions of Human Biology and Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Yifan Cheng
- Quantitative Bioscience Institute, University of California, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, CA, USA
| | - John D Gross
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA.
- Quantitative Bioscience Institute, University of California, San Francisco, CA, USA.
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5
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Ito F, Alvarez-Cabrera AL, Liu S, Yang H, Shiriaeva A, Zhou ZH, Chen XS. Structural basis for HIV-1 antagonism of host APOBEC3G via Cullin E3 ligase. SCIENCE ADVANCES 2023; 9:eade3168. [PMID: 36598981 PMCID: PMC9812381 DOI: 10.1126/sciadv.ade3168] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
Human APOBEC3G (A3G) is a virus restriction factor that inhibits HIV-1 replication and triggers lethal hypermutation on viral reverse transcripts. HIV-1 viral infectivity factor (Vif) breaches this host A3G immunity by hijacking a cellular E3 ubiquitin ligase complex to target A3G for ubiquitination and degradation. The molecular mechanism of A3G targeting by Vif-E3 ligase is unknown, limiting the antiviral efforts targeting this host-pathogen interaction crucial for HIV-1 infection. Here, we report the cryo-electron microscopy structures of A3G bound to HIV-1 Vif in complex with T cell transcription cofactor CBF-β and multiple components of the Cullin-5 RING E3 ubiquitin ligase. The structures reveal unexpected RNA-mediated interactions of Vif with A3G primarily through A3G's noncatalytic domain, while A3G's catalytic domain is poised for ubiquitin transfer. These structures elucidate the molecular mechanism by which HIV-1 Vif hijacks the host ubiquitin ligase to specifically target A3G to establish infection and offer structural information for the rational development of antiretroviral therapeutics.
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Affiliation(s)
- Fumiaki Ito
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Ana L. Alvarez-Cabrera
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
- California NanoSystems Institute, UCLA, Los Angeles, CA, USA
| | - Shiheng Liu
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
- California NanoSystems Institute, UCLA, Los Angeles, CA, USA
| | - Hanjing Yang
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Anna Shiriaeva
- Department of Biological Chemistry, UCLA, Los Angeles, CA, USA
| | - Z. Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA, USA
- California NanoSystems Institute, UCLA, Los Angeles, CA, USA
| | - Xiaojiang S. Chen
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA, USA
- Genetic, Molecular, and Cellular Biology Program, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA
- Center of Excellence in NanoBiophysics, University of Southern California, Los Angeles, CA, USA
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6
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The current toolbox for APOBEC drug discovery. Trends Pharmacol Sci 2022; 43:362-377. [PMID: 35272863 PMCID: PMC9018551 DOI: 10.1016/j.tips.2022.02.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 02/03/2022] [Accepted: 02/09/2022] [Indexed: 12/14/2022]
Abstract
Mutational processes driving genome evolution and heterogeneity contribute to immune evasion and therapy resistance in viral infections and cancer. APOBEC3 (A3) enzymes promote such mutations by catalyzing the deamination of cytosines to uracils in single-stranded DNA. Chemical inhibition of A3 enzymes may yield an antimutation therapeutic strategy to improve the durability of current drug therapies that are prone to resistance mutations. A3 small-molecule drug discovery efforts to date have been restricted to a single high-throughput biochemical activity assay; however, the arsenal of discovery assays has significantly expanded in recent years. The assays used to study A3 enzymes are reviewed here with an eye towards their potential for small-molecule discovery efforts.
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7
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Wu R, Oshi M, Asaoka M, Huyser MR, Tokumaru Y, Yamada A, Yan L, Endo I, Ishikawa T, Takabe K. APOBEC3F expression in triple-negative breast cancer is associated with tumor microenvironment infiltration and activation of cancer immunity and improved survival. Am J Cancer Res 2022; 12:744-762. [PMID: 35261799 PMCID: PMC8899983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 11/16/2021] [Indexed: 06/14/2023] Open
Abstract
The apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) causes a point mutation from cytidine to uracil in DNA and/or RNA. The role of APOBEC3A and APOBEC3B in breast cancer has been well described, whereas that of APOBEC3F remains unknown. To investigate the clinical relevance of APOBEC3F expression, we analyzed a total of 3000 breast cancer cases from multiple independent large patient cohorts including METABRIC, TCGA, GSE75688, and GSE114725. High expression of APOBEC3F was associated with improved disease-specific and overall survival in triple negative breast cancer (TNBC). APOBEC3F is not usually a reflection of cancer cell biology in TNBC or luminal breast cancer, except for homologous recombination deficiency in TNBC. In the TNBC homologous recombination deficiency group, APOBEC3F expression was not consistently associated with intratumor heterogeneity, mutation rates, or neoantigens. APOBEC3F expression did not correlate with response to any of the drugs tested in breast cancer cell lines in vitro. However, high APOBEC3F expression was associated with enrichment of several immune-related gene sets and immune activity. High APOBEC3F expression also accompanied higher infiltration of anti-cancer immune cell infiltration in TNBC. However, in luminal breast cancer, high APOBEC3F tumor significantly enriched not only immune-related gene sets, but also cell proliferation-, metastasis-, and apoptosis-related gene sets. Analysis of single-cell transcriptomes showed APOBEC3F exclusively expressed in immune cells and significantly associated with cytolytic activity of the immune cells, immune response, and immune cell proliferation. Expression of immune checkpoint genes was uniformly elevated in APOBEC3F-high tumors. We conclude that APOBEC3F is exclusively expressed in immune cells and this expression is associated with enhanced anti-cancer immune response as well as improved survival in TNBC.
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Affiliation(s)
- Rongrong Wu
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
- Department of Breast Surgery and Oncology, Tokyo Medical UniversityTokyo, Japan
| | - Masanori Oshi
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
- Department of Gastroenterological Surgery, Yokohama City University Graduate School of MedicineYokohama, Kanagawa, Japan
| | - Mariko Asaoka
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
- Department of Breast Surgery and Oncology, Tokyo Medical UniversityTokyo, Japan
| | - Michelle R Huyser
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
| | - Yoshihisa Tokumaru
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
- Department of Surgical Oncology, Graduate School of Medicine, Gifu UniversityGifu, Japan
| | - Akimitsu Yamada
- Department of Gastroenterological Surgery, Yokohama City University Graduate School of MedicineYokohama, Kanagawa, Japan
| | - Li Yan
- Department of Biostatistics & Bioinformatics, Roswell Park Cancer InstituteBuffalo, NY, USA
| | - Itaru Endo
- Department of Gastroenterological Surgery, Yokohama City University Graduate School of MedicineYokohama, Kanagawa, Japan
| | - Takashi Ishikawa
- Department of Breast Surgery and Oncology, Tokyo Medical UniversityTokyo, Japan
| | - Kazuaki Takabe
- Department of Surgical Oncology, Roswell Park Cancer InstituteBuffalo, NY, USA
- Department of Breast Surgery and Oncology, Tokyo Medical UniversityTokyo, Japan
- Department of Gastroenterological Surgery, Yokohama City University Graduate School of MedicineYokohama, Kanagawa, Japan
- Department of Surgery, Jacobs School of Medicine and Biomedical Sciences, State University of New YorkBuffalo, NY, USA
- Department of Surgery, Niigata University Graduate School of Medical and Dental SciencesNiigata, Japan
- Department of Breast Surgery, Fukushima Medical UniversityFukushima, Japan
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8
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Zhao X, Zhao Y, Du J, Gao P, Zhao K. The Interplay Among HIV, LINE-1, and the Interferon Signaling System. Front Immunol 2021; 12:732775. [PMID: 34566998 PMCID: PMC8459832 DOI: 10.3389/fimmu.2021.732775] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/20/2021] [Indexed: 12/17/2022] Open
Abstract
Human immunodeficiency viruses (HIVs) are retroviruses that replicate effectively in human CD4+ cells and cause the development of acquired immune deficiency syndrome (AIDS). On the other hand, type 1 long interspersed elements (LINE-1s or L1s) are the only active retroelements that can replicate autonomously in human cells. They, along with other active yet nonautonomous retroelements, have been associated with autoimmune diseases. There are many similarities between HIV and LINE-1. Being derived (or evolved) from ancient retroviruses, both HIV and LINE-1 replicate through a process termed reverse transcription, activate endogenous DNA and RNA sensors, trigger innate immune activation to promote interferon (IFN) expression, and are suppressed by protein products of interferon-stimulated genes (ISGs). However, these similarities make it difficult to decipher or even speculate the relationship between HIV and LINE-1, especially regarding the involvement of the IFN signaling system. In this review, we summarize previous findings on the relationships between HIV and innate immune activation as well as between LINE-1 and IFN upregulation. We also attempt to elucidate the interplay among HIV, LINE-1, and the IFN signaling system in hopes of guiding future research directions for viral suppression and immune regulation.
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Affiliation(s)
- Xu Zhao
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, China.,Department of Hepatology, First Hospital of Jilin University, Changchun, China
| | - Yifei Zhao
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, China
| | - Juan Du
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, China.,Key Laboratory of Organ Regeneration & Transplantation of the Ministry of Education, First Hospital of Jilin University, Changchun, China
| | - Pujun Gao
- Department of Hepatology, First Hospital of Jilin University, Changchun, China
| | - Ke Zhao
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, China.,Key Laboratory of Organ Regeneration & Transplantation of the Ministry of Education, First Hospital of Jilin University, Changchun, China
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9
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APOBEC3F Constitutes a Barrier to Successful Cross-Species Transmission of Simian Immunodeficiency Virus SIVsmm to Humans. J Virol 2021; 95:e0080821. [PMID: 34132575 DOI: 10.1128/jvi.00808-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Simian immunodeficiency virus infecting sooty mangabeys (SIVsmm) has been transmitted to humans on at least nine occasions, giving rise to human immunodeficiency virus type 2 (HIV-2) groups A to I. SIVsmm isolates replicate in human T cells and seem capable of overcoming major human restriction factors without adaptation. However, only groups A and B are responsible for the HIV-2 epidemic in sub-Saharan Africa, and it is largely unclear whether adaptive changes were associated with spread in humans. To address this, we examined the sensitivity of infectious molecular clones (IMCs) of five HIV-2 strains and representatives of five different SIVsmm lineages to various APOBEC3 proteins. We confirmed that SIVsmm strains replicate in human T cells, albeit with more variable replication fitness and frequently lower efficiency than HIV-2 IMCs. Efficient viral propagation was generally dependent on intact vif genes, highlighting the need for counteraction of APOBEC3 proteins. On average, SIVsmm was more susceptible to inhibition by human APOBEC3D, -F, -G, and -H than HIV-2. For example, human APOBEC3F reduced infectious virus yield of SIVsmm by ∼80% but achieved only ∼40% reduction in the case of HIV-2. Functional and mutational analyses of human- and monkey-derived alleles revealed that an R128T polymorphism in APOBEC3F contributes to species-specific counteraction by HIV-2 and SIVsmm Vifs. In addition, a T84S substitution in SIVsmm Vif increased its ability to counteract human APOBEC3F. Altogether, our results confirm that SIVsmm Vif proteins show intrinsic activity against human APOBEC3 proteins but also demonstrate that epidemic HIV-2 strains evolved an increased ability to counteract this class of restriction factors during human adaptation. IMPORTANCE Viral zoonoses pose a significant threat to human health, and it is important to understand determining factors. SIVs infecting great apes gave rise to HIV-1. In contrast, SIVs infecting African monkey species have not been detected in humans, with one notable exception. SIVsmm from sooty mangabeys has crossed the species barrier to humans on at least nine independent occasions and seems capable of overcoming many innate defense mechanisms without adaptation. Here, we confirmed that SIVsmm Vif proteins show significant activity against human APOBEC3 proteins. Our analyses also revealed, however, that different lineages of SIVsmm are significantly more susceptible to inhibition by various human APOBEC3 proteins than HIV-2 strains. Mutational analyses suggest that an R128T substitution in APOBEC3F and a T84S change in Vif contribute to species-specific counteraction by HIV-2 and SIVsmm. Altogether, our results support that epidemic HIV-2 strains acquired increased activity against human APOBEC3 proteins to clear this restrictive barrier.
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10
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Ikeda T, Yue Y, Shimizu R, Nasser H. Potential Utilization of APOBEC3-Mediated Mutagenesis for an HIV-1 Functional Cure. Front Microbiol 2021; 12:686357. [PMID: 34211449 PMCID: PMC8239295 DOI: 10.3389/fmicb.2021.686357] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/10/2021] [Indexed: 11/13/2022] Open
Abstract
The introduction of combination antiretroviral therapy (cART) has managed to control the replication of human immunodeficiency virus type 1 (HIV-1) in infected patients. However, a complete HIV-1 cure, including a functional cure for or eradication of HIV-1, has yet to be achieved because of the persistence of latent HIV-1 reservoirs in adherent patients. The primary source of these viral reservoirs is integrated proviral DNA in CD4+ T cells and other non-T cells. Although a small fraction of this proviral DNA is replication-competent and contributes to viral rebound after the cessation of cART, >90% of latent viral reservoirs are replication-defective and some contain high rates of G-to-A mutations in proviral DNA. At least in part, these high rates of G-to-A mutations arise from the APOBEC3 (A3) family proteins of cytosine deaminases. A general model has shown that the HIV-1 virus infectivity factor (Vif) degrades A3 family proteins by proteasome-mediated pathways and inactivates their antiviral activities. However, Vif does not fully counteract the HIV-1 restriction activity of A3 family proteins in vivo, as indicated by observations of A3-mediated G-to-A hypermutation in the proviral DNA of HIV-1-infected patients. The frequency of A3-mediated hypermutation potentially contributes to slower HIV-1/AIDS disease progression and virus evolution including the emergence of cytotoxic T lymphocyte escape mutants. Therefore, combined with other strategies, the manipulation of A3-mediated mutagenesis may contribute to an HIV-1 functional cure aimed at cART-free remission. In this mini-review, we discuss the possibility of an HIV-1 functional cure arising from manipulation of A3 mutagenic activity.
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Affiliation(s)
- Terumasa Ikeda
- Division of Molecular Virology and Genetics, Joint Research Center for Human Retrovirus Infection, Kumamoto University, Kumamoto, Japan
| | - Yuan Yue
- Division of Molecular Virology and Genetics, Joint Research Center for Human Retrovirus Infection, Kumamoto University, Kumamoto, Japan.,Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Ryo Shimizu
- Division of Molecular Virology and Genetics, Joint Research Center for Human Retrovirus Infection, Kumamoto University, Kumamoto, Japan.,Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Hesham Nasser
- Division of Molecular Virology and Genetics, Joint Research Center for Human Retrovirus Infection, Kumamoto University, Kumamoto, Japan
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11
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Gaba A, Flath B, Chelico L. Examination of the APOBEC3 Barrier to Cross Species Transmission of Primate Lentiviruses. Viruses 2021; 13:1084. [PMID: 34200141 PMCID: PMC8228377 DOI: 10.3390/v13061084] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 12/12/2022] Open
Abstract
The transmission of viruses from animal hosts into humans have led to the emergence of several diseases. Usually these cross-species transmissions are blocked by host restriction factors, which are proteins that can block virus replication at a specific step. In the natural virus host, the restriction factor activity is usually suppressed by a viral antagonist protein, but this is not the case for restriction factors from an unnatural host. However, due to ongoing viral evolution, sometimes the viral antagonist can evolve to suppress restriction factors in a new host, enabling cross-species transmission. Here we examine the classical case of this paradigm by reviewing research on APOBEC3 restriction factors and how they can suppress human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). APOBEC3 enzymes are single-stranded DNA cytidine deaminases that can induce mutagenesis of proviral DNA by catalyzing the conversion of cytidine to promutagenic uridine on single-stranded viral (-)DNA if they escape the HIV/SIV antagonist protein, Vif. APOBEC3 degradation is induced by Vif through the proteasome pathway. SIV has been transmitted between Old World Monkeys and to hominids. Here we examine the adaptations that enabled such events and the ongoing impact of the APOBEC3-Vif interface on HIV in humans.
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Affiliation(s)
| | | | - Linda Chelico
- Department of Biochemistry, Microbiology, and Immunology, University of Saskatchewan, Saskatoon, SA S7H 0E5, Canada; (A.G.); (B.F.)
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12
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Hu Y, Knecht KM, Shen Q, Xiong Y. Multifaceted HIV-1 Vif interactions with human E3 ubiquitin ligase and APOBEC3s. FEBS J 2021; 288:3407-3417. [PMID: 32893454 PMCID: PMC8172064 DOI: 10.1111/febs.15550] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 09/01/2020] [Indexed: 12/31/2022]
Abstract
APOBEC3 (A3) proteins are a family of host antiviral restriction factors that potently inhibit various retroviral infections, including human immunodeficiency virus (HIV)-1. To overcome this restriction, HIV-1 virion infectivity factor (Vif) recruits the cellular cofactor CBFβ to assist in targeting A3 proteins to a host E3 ligase complex for polyubiquitination and subsequent proteasomal degradation. Intervention of the Vif-A3 interactions could be a promising therapeutic strategy to facilitate A3-mediated suppression of HIV-1 in patients. In this structural snapshot, we review the structural features of the recently determined structure of human A3F in complex with HIV-1 Vif and its cofactor CBFβ, discuss insights into the molecular principles of Vif-A3 interplay during the arms race between the virus and host, and highlight the therapeutic implications.
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Affiliation(s)
- Yingxia Hu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Kirsten M. Knecht
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Qi Shen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
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13
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A hijack mechanism of Indian SARS-CoV-2 isolates for relapsing contemporary antiviral therapeutics. Comput Biol Med 2021; 132:104315. [PMID: 33705994 PMCID: PMC7935700 DOI: 10.1016/j.compbiomed.2021.104315] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 03/02/2021] [Indexed: 12/16/2022]
Abstract
Coronavirus disease (COVID-19) rapidly expands to a global pandemic and its impact on public health varies from country to country. It is caused by a new virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is imperative for relapsing current antiviral therapeutics owing to randomized genetic drift in global SARS-CoV-2 isolates. A molecular mechanism behind the emerging genomic variants is not yet understood for the prioritization of selective antivirals. The present computational study was aimed to repurpose existing antivirals for Indian SARS-CoV-2 isolates by uncovering a hijack mechanism based on structural and functional characteristics of protein variants. Forty-one protein mutations were identified in 12 Indian SARS-CoV-2 isolates by analysis of genome variations across 460 genome sequences obtained from 30 geographic sites in India. Two unique mutations such as W6152R and N5928H found in exonuclease of Surat (GBRC275b) and Gandhinagar (GBRC239) isolates. We report for the first time the impact of folding rate on stabilizing/retaining a sequence-structure-function-virulence link of emerging protein variants leading to accommodate hijack ability from current antivirals. Binding affinity analysis revealed the effect of point mutations on virus infectivity and the drug-escaping efficiency of Indian isolates. Emodin and artinemol suggested herein as repurposable antivirals for the treatment of COVID-19 patients infected with Indian isolates. Our study concludes that a protein folding rate is a key structural and evolutionary determinant to enhance the receptor-binding specificity and ensure hijack ability from the prevalent antiviral therapeutics.
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Degradation-Independent Inhibition of APOBEC3G by the HIV-1 Vif Protein. Viruses 2021; 13:v13040617. [PMID: 33916704 PMCID: PMC8066197 DOI: 10.3390/v13040617] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/30/2021] [Accepted: 04/01/2021] [Indexed: 12/20/2022] Open
Abstract
The ubiquitin–proteasome system plays an important role in the cell under normal physiological conditions but also during viral infections. Indeed, many auxiliary proteins from the (HIV-1) divert this system to its own advantage, notably to induce the degradation of cellular restriction factors. For instance, the HIV-1 viral infectivity factor (Vif) has been shown to specifically counteract several cellular deaminases belonging to the apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC3 or A3) family (A3A to A3H) by recruiting an E3-ubiquitin ligase complex and inducing their polyubiquitination and degradation through the proteasome. Although this pathway has been extensively characterized so far, Vif has also been shown to impede A3s through degradation-independent processes, but research on this matter remains limited. In this review, we describe our current knowledge regarding the degradation-independent inhibition of A3s, and A3G in particular, by the HIV-1 Vif protein, the molecular mechanisms involved, and highlight important properties of this small viral protein.
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15
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Insights into the Structures and Multimeric Status of APOBEC Proteins Involved in Viral Restriction and Other Cellular Functions. Viruses 2021; 13:v13030497. [PMID: 33802945 PMCID: PMC8002816 DOI: 10.3390/v13030497] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/15/2021] [Accepted: 03/15/2021] [Indexed: 12/16/2022] Open
Abstract
Apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC) proteins belong to a family of deaminase proteins that can catalyze the deamination of cytosine to uracil on single-stranded DNA or/and RNA. APOBEC proteins are involved in diverse biological functions, including adaptive and innate immunity, which are critical for restricting viral infection and endogenous retroelements. Dysregulation of their functions can cause undesired genomic mutations and RNA modification, leading to various associated diseases, such as hyper-IgM syndrome and cancer. This review focuses on the structural and biochemical data on the multimerization status of individual APOBECs and the associated functional implications. Many APOBECs form various multimeric complexes, and multimerization is an important way to regulate functions for some of these proteins at several levels, such as deaminase activity, protein stability, subcellular localization, protein storage and activation, virion packaging, and antiviral activity. The multimerization of some APOBECs is more complicated than others, due to the associated complex RNA binding modes.
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16
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Kostrhon S, Prabu JR, Baek K, Horn-Ghetko D, von Gronau S, Klügel M, Basquin J, Alpi AF, Schulman BA. CUL5-ARIH2 E3-E3 ubiquitin ligase structure reveals cullin-specific NEDD8 activation. Nat Chem Biol 2021; 17:1075-1083. [PMID: 34518685 PMCID: PMC8460447 DOI: 10.1038/s41589-021-00858-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 07/06/2021] [Indexed: 02/08/2023]
Abstract
An emerging mechanism of ubiquitylation involves partnering of two distinct E3 ligases. In the best-characterized E3-E3 pathways, ARIH-family RING-between-RING (RBR) E3s ligate ubiquitin to substrates of neddylated cullin-RING E3s. The E3 ARIH2 has been implicated in ubiquitylation of substrates of neddylated CUL5-RBX2-based E3s, including APOBEC3-family substrates of the host E3 hijacked by HIV-1 virion infectivity factor (Vif). However, the structural mechanisms remained elusive. Here structural and biochemical analyses reveal distinctive ARIH2 autoinhibition, and activation on assembly with neddylated CUL5-RBX2. Comparison to structures of E3-E3 assemblies comprising ARIH1 and neddylated CUL1-RBX1-based E3s shows cullin-specific regulation by NEDD8. Whereas CUL1-linked NEDD8 directly recruits ARIH1, CUL5-linked NEDD8 does not bind ARIH2. Instead, the data reveal an allosteric mechanism. NEDD8 uniquely contacts covalently linked CUL5, and elicits structural rearrangements that unveil cryptic ARIH2-binding sites. The data reveal how a ubiquitin-like protein induces protein-protein interactions indirectly, through allostery. Allosteric specificity of ubiquitin-like protein modifications may offer opportunities for therapeutic targeting.
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Affiliation(s)
- Sebastian Kostrhon
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - J. Rajan Prabu
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Kheewoong Baek
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Daniel Horn-Ghetko
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Susanne von Gronau
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Maren Klügel
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Jérôme Basquin
- grid.418615.f0000 0004 0491 845XDepartment of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Arno F. Alpi
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Brenda A. Schulman
- grid.418615.f0000 0004 0491 845XDepartment of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
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Knecht KM, Hu Y, Rubene D, Cook M, Ziegler SJ, Jónsson SR, Xiong Y. Maedi-visna virus Vif protein uses motifs distinct from HIV-1 Vif to bind zinc and the cofactor required for A3 degradation. J Biol Chem 2021; 296:100045. [PMID: 33465707 PMCID: PMC7949081 DOI: 10.1074/jbc.ra120.015828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/23/2020] [Accepted: 11/09/2020] [Indexed: 11/06/2022] Open
Abstract
The mammalian apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3 or A3) family of cytidine deaminases restrict viral infections by mutating viral DNA and impeding reverse transcription. To overcome this antiviral activity, most lentiviruses express a viral accessory protein called the virion infectivity factor (Vif), which recruits A3 proteins to cullin-RING E3 ubiquitin ligases such as cullin-5 (Cul5) for ubiquitylation and subsequent proteasomal degradation. Although Vif proteins from primate lentiviruses such as HIV-1 utilize the transcription factor core-binding factor subunit beta as a noncanonical cofactor to stabilize the complex, the maedi-visna virus (MVV) Vif hijacks cyclophilin A (CypA) instead. Because core-binding factor subunit beta and CypA are both highly conserved among mammals, the requirement for two different cellular cofactors suggests that these two A3-targeting Vif proteins have different biochemical and structural properties. To investigate this topic, we used a combination of in vitro biochemical assays and in vivo A3 degradation assays to study motifs required for the MVV Vif to bind zinc ion, Cul5, and the cofactor CypA. Our results demonstrate that although some common motifs between the HIV-1 Vif and MVV Vif are involved in recruiting Cul5, different determinants in the MVV Vif are required for cofactor binding and stabilization of the E3 ligase complex, such as the zinc-binding motif and N- and C-terminal regions of the protein. Results from this study advance our understanding of the mechanism of MVV Vif recruitment of cellular factors and the evolution of lentiviral Vif proteins.
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Affiliation(s)
- Kirsten M Knecht
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Yingxia Hu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Diana Rubene
- Institute for Experimental Pathology, University of Iceland, Keldur, Iceland
| | - Matthew Cook
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Samantha J Ziegler
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Stefán R Jónsson
- Institute for Experimental Pathology, University of Iceland, Keldur, Iceland
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
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18
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Retroviral Restriction Factors and Their Viral Targets: Restriction Strategies and Evolutionary Adaptations. Microorganisms 2020; 8:microorganisms8121965. [PMID: 33322320 PMCID: PMC7764263 DOI: 10.3390/microorganisms8121965] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/30/2020] [Accepted: 12/08/2020] [Indexed: 12/17/2022] Open
Abstract
The evolutionary conflict between retroviruses and their vertebrate hosts over millions of years has led to the emergence of cellular innate immune proteins termed restriction factors as well as their viral antagonists. Evidence accumulated in the last two decades has substantially increased our understanding of the elaborate mechanisms utilized by these restriction factors to inhibit retroviral replication, mechanisms that either directly block viral proteins or interfere with the cellular pathways hijacked by the viruses. Analyses of these complex interactions describe patterns of accelerated evolution for these restriction factors as well as the acquisition and evolution of their virus-encoded antagonists. Evidence is also mounting that many restriction factors identified for their inhibition of specific retroviruses have broader antiviral activity against additional retroviruses as well as against other viruses, and that exposure to these multiple virus challenges has shaped their adaptive evolution. In this review, we provide an overview of the restriction factors that interfere with different steps of the retroviral life cycle, describing their mechanisms of action, adaptive evolution, viral targets and the viral antagonists that evolved to counter these factors.
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Functional and Structural Insights into a Vif/PPP2R5 Complex Elucidated Using Patient HIV-1 Isolates and Computational Modeling. J Virol 2020; 94:JVI.00631-20. [PMID: 32847850 DOI: 10.1128/jvi.00631-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) Vif recruits a cellular ubiquitin ligase complex to degrade antiviral APOBEC3 enzymes (APOBEC3C-H) and PP2A phosphatase regulators (PPP2R5A to PPP2R5E). While APOBEC3 antagonism is the canonical function of HIV-1 Vif, this viral accessory protein is also known to trigger G2/M cell cycle arrest. Vif initiates G2/M arrest by degrading multiple PPP2R5 family members, an activity prevalent among diverse HIV-1 and simian immunodeficiency virus (SIV) isolates. Here, computational protein-protein docking was used to delineate a Vif/CBF-β/PPP2R5 complex in which Vif is predicted to bind the same PPP2R5 surface as physiologic phosphatase targets. This model was tested using targeted mutagenesis of amino acid residues within or adjacent to the putative interface to show loss or retention, respectively, of Vif-induced PPP2R5 degradation activity. Additionally, expression of a peptide that mimics cellular targets of PPP2R5s robustly inhibited Vif-mediated degradation of PPP2R5A but not APOBEC3G. Moreover, live-cell imaging studies examining Vif-mediated degradation of PPP2R5A and APOBEC3G within the same cell revealed that PPP2R5A degradation kinetics are comparable to those of APOBEC3G with a half-life of roughly 6 h postinfection, demonstrating that Vif can concurrently mediate the degradation of distinct cellular substrates. Finally, experiments with a panel of patient-derived Vif isolates indicated that PPP2R5A degradation activity is common in patient-derived isolates. Taken together, these results support a model in which PPP2R5 degradation and global changes in the cellular phosphoproteome are likely to be advantageous for viral pathogenesis.IMPORTANCE A critical function of HIV-1 Vif is to counteract the family of APOBEC3 innate immune proteins. It is also widely accepted that Vif induces G2/M cell cycle arrest in several different cell types. Recently, it has been shown that Vif degrades multiple PPP2R5 phosphoregulators to induce the G2/M arrest phenotype. Here, computational approaches are used to test a structural model of the Vif/PPP2R5 complex. In addition, imaging studies are used to show that Vif degrades these PPP2R5 substrates in roughly the same time frame as APOBEC3 degradation and that this activity is prevalent in patient-derived Vif isolates. These studies are important by further defining PPP2R5 proteins as a bona fide substrate of HIV-1 Vif.
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Delviks-Frankenberry KA, Desimmie BA, Pathak VK. Structural Insights into APOBEC3-Mediated Lentiviral Restriction. Viruses 2020; 12:E587. [PMID: 32471198 PMCID: PMC7354603 DOI: 10.3390/v12060587] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/22/2020] [Accepted: 05/24/2020] [Indexed: 01/18/2023] Open
Abstract
Mammals have developed clever adaptive and innate immune defense mechanisms to protect against invading bacterial and viral pathogens. Human innate immunity is continuously evolving to expand the repertoire of restriction factors and one such family of intrinsic restriction factors is the APOBEC3 (A3) family of cytidine deaminases. The coordinated expression of seven members of the A3 family of cytidine deaminases provides intrinsic immunity against numerous foreign infectious agents and protects the host from exogenous retroviruses and endogenous retroelements. Four members of the A3 proteins-A3G, A3F, A3H, and A3D-restrict HIV-1 in the absence of virion infectivity factor (Vif); their incorporation into progeny virions is a prerequisite for cytidine deaminase-dependent and -independent activities that inhibit viral replication in the host target cell. HIV-1 encodes Vif, an accessory protein that antagonizes A3 proteins by targeting them for polyubiquitination and subsequent proteasomal degradation in the virus producing cells. In this review, we summarize our current understanding of the role of human A3 proteins as barriers against HIV-1 infection, how Vif overcomes their antiviral activity, and highlight recent structural and functional insights into A3-mediated restriction of lentiviruses.
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Affiliation(s)
| | | | - Vinay K. Pathak
- Viral Mutation Section, HIV Dynamics and Replication Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA; (K.A.D.-F.); (B.A.D.)
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