1
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Yang H, Pacheco J, Kim K, Ebrahimi D, Ito F, Chen XS. Molecular mechanism for regulating APOBEC3G DNA editing function by the non-catalytic domain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.11.584510. [PMID: 38559028 PMCID: PMC10980023 DOI: 10.1101/2024.03.11.584510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
APOBEC3G (A3G) belongs to the AID/APOBEC cytidine deaminase family and is essential for antiviral immunity. It contains two zinc-coordinated cytidine-deaminase (CD) domains. The N-terminal CD1 domain is non-catalytic but has a strong affinity for nucleic acids, whereas the C-terminal CD2 domain catalyzes C-to-U editing in single-stranded DNA. The interplay between the two domains in DNA binding and editing is not fully understood. Here, our studies on rhesus macaque A3G (rA3G) show that the DNA editing function in linear and hairpin loop DNA is greatly enhanced by AA or GA dinucleotide motifs present downstream (in the 3'-direction) but not upstream (in the 5'-direction) of the target-C editing sites. The effective distance between AA/GA and the target-C sites depends on the local DNA secondary structure. We present two co-crystal structures of rA3G bound to ssDNA containing AA and GA, revealing the contribution of the non-catalytic CD1 domain in capturing AA/GA DNA and explaining our biochemical observations. Our structural and biochemical findings elucidate the molecular mechanism underlying the cooperative function between the non-catalytic and the catalytic domains of A3G, which is critical for its antiviral role and its contribution to genome mutations in cancer.
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Affiliation(s)
- Hanjing Yang
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Josue Pacheco
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Kyumin Kim
- Molecular and Computational Biology, Departments of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Diako Ebrahimi
- Texas Biomedical Research Institute, San Antonio, TX 78227, USA
| | - Fumiaki Ito
- Molecular and Computational Biology, Departments 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
| | - Xiaojiang S. Chen
- Molecular and Computational Biology, Departments 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, CA 90089, USA
- Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90089, USA
- Center of Excellence in NanoBiophysics, University of Southern California, Los Angeles, CA 90089, USA
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2
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Bao Q, Zhou J. Various strategies for developing APOBEC3G protectors to circumvent human immunodeficiency virus type 1. Eur J Med Chem 2023; 250:115188. [PMID: 36773550 DOI: 10.1016/j.ejmech.2023.115188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/18/2023] [Accepted: 02/04/2023] [Indexed: 02/09/2023]
Abstract
Host restriction factor APOBEC3G (A3G) efficiently restricts Vif-deficient HIV-1 by being packaged with progeny virions and causing the G to A mutation during HIV-1 viral DNA synthesis as the progeny virus infects new cells. HIV-1 expresses Vif protein to resist the activity of A3G by mediating A3G degradation. This process requires the self-association of Vif in concert with A3G proteins, protein chaperones, and factors of the ubiquitination machinery, which are potential targets to discover novel anti-HIV drugs. This review will describe compounds that have been reported so far to inhibit viral replication of HIV-1 by protecting A3G from Vif-mediated degradation.
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Affiliation(s)
- Qiqi Bao
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, PR China; Drug Development and Innovation Center, College of Chemistry and Life Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, PR China
| | - Jinming Zhou
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, PR China; Drug Development and Innovation Center, College of Chemistry and Life Sciences, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, PR China.
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3
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Ajoge HO, Renner TM, Bélanger K, Greig M, Dankar S, Kohio HP, Coleman MD, Ndashimye E, Arts EJ, Langlois MA, Barr SD. Antiretroviral APOBEC3 cytidine deaminases alter HIV-1 provirus integration site profiles. Nat Commun 2023; 14:16. [PMID: 36627271 PMCID: PMC9832166 DOI: 10.1038/s41467-022-35379-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 11/30/2022] [Indexed: 01/12/2023] Open
Abstract
APOBEC3 (A3) proteins are host-encoded deoxycytidine deaminases that provide an innate immune barrier to retroviral infection, notably against HIV-1. Low levels of deamination are believed to contribute to the genetic evolution of HIV-1, while intense catalytic activity of these proteins can induce catastrophic hypermutation in proviral DNA leading to near-total HIV-1 restriction. So far, little is known about how A3 cytosine deaminases might impact HIV-1 proviral DNA integration sites in human chromosomal DNA. Using a deep sequencing approach, we analyze the influence of catalytic active and inactive APOBEC3F and APOBEC3G on HIV-1 integration site selections. Here we show that DNA editing is detected at the extremities of the long terminal repeat regions of the virus. Both catalytic active and non-catalytic A3 mutants decrease insertions into gene coding sequences and increase integration sites into SINE elements, oncogenes and transcription-silencing non-B DNA features. Our data implicates A3 as a host factor influencing HIV-1 integration site selection and also promotes what appears to be a more latent expression profile.
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Affiliation(s)
- Hannah O Ajoge
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada
| | - Tyler M Renner
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Kasandra Bélanger
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Matthew Greig
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Samar Dankar
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Hinissan P Kohio
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada
| | - Macon D Coleman
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada
| | - Emmanuel Ndashimye
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada
| | - Eric J Arts
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada
| | - Marc-André Langlois
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada. .,Ottawa Center for Infection, Immunity and Inflammation (CI3), Ottawa, ON, Canada.
| | - Stephen D Barr
- Western University, Schulich School of Medicine and Dentistry, Department of Microbiology and Immunology, London, ON, Canada.
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4
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Yang H, Kim K, Li S, Pacheco J, Chen XS. Structural basis of sequence-specific RNA recognition by the antiviral factor APOBEC3G. Nat Commun 2022; 13:7498. [PMID: 36470880 PMCID: PMC9722718 DOI: 10.1038/s41467-022-35201-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022] Open
Abstract
An essential step in restricting HIV infectivity by the antiviral factor APOBEC3G is its incorporation into progeny virions via binding to HIV RNA. However, the mechanism of APOBEC3G capturing viral RNA is unknown. Here, we report crystal structures of a primate APOBEC3G bound to different types of RNAs, revealing that APOBEC3G specifically recognizes unpaired 5'-AA-3' dinucleotides, and to a lesser extent, 5'-GA-3' dinucleotides. APOBEC3G binds to the common 3'A in the AA/GA motifs using an aromatic/hydrophobic pocket in the non-catalytic domain. It binds to the 5'A or 5'G in the AA/GA motifs using an aromatic/hydrophobic groove conformed between the non-catalytic and catalytic domains. APOBEC3G RNA binding property is distinct from that of the HIV nucleocapsid protein recognizing unpaired guanosines. Our findings suggest that the sequence-specific RNA recognition is critical for APOBEC3G virion packaging and restricting HIV infectivity.
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Affiliation(s)
- Hanjing Yang
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Los Angeles, CA 90089 USA
| | - Kyumin Kim
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Los Angeles, CA 90089 USA
| | - Shuxing Li
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Los Angeles, CA 90089 USA ,grid.42505.360000 0001 2156 6853Center of Excellence in NanoBiophysics, University of Southern California, Los Angeles, CA 90089 USA
| | - Josue Pacheco
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Los Angeles, CA 90089 USA
| | - Xiaojiang S. Chen
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Los Angeles, CA 90089 USA ,grid.42505.360000 0001 2156 6853Center of Excellence in NanoBiophysics, University of Southern California, Los Angeles, CA 90089 USA ,grid.42505.360000 0001 2156 6853Genetic, Molecular and Cellular Biology Program, Keck School of Medicine, Los Angeles, CA 90033 USA ,grid.42505.360000 0001 2156 6853Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA 90033 USA
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5
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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: 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: 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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6
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Wang J, Becker JT, Shi K, Lauer KV, Salamango DJ, Aihara H, Shaban NM, Harris RS. The Role of RNA in HIV-1 Vif-Mediated Degradation of APOBEC3H. J Mol Biol 2019; 431:5019-5031. [PMID: 31628948 DOI: 10.1016/j.jmb.2019.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/04/2019] [Accepted: 09/16/2019] [Indexed: 11/17/2022]
Abstract
As many as five members of the APOBEC3 family of DNA cytosine deaminases are capable of inhibiting HIV-1 replication by deaminating viral cDNA cytosines and interfering with reverse transcription. HIV-1 counteracts restriction with the virally encoded Vif protein, which forms a hybrid ubiquitin ligase complex that directly binds APOBEC3 enzymes and targets them for proteasomal degradation. APOBEC3H (A3H) is unique among family members by dimerization through cellular and viral duplex RNA species. RNA binding is required for localization of A3H to the cytoplasmic compartment, for efficient packaging into nascent HIV-1 particles and ultimately for effective virus restriction activity. Here we compared wild-type human A3H and RNA binding-defective mutants to ask whether RNA may be a factor in the functional interaction with HIV-1 Vif. We used structural modeling, immunoblotting, live cell imaging, and split green fluorescence protein (GFP) reconstitution approaches to assess the capability of HIV-1 Vif to promote the degradation of wild-type A3H in comparison to RNA binding-defective mutants. The results combined to show that RNA is not strictly required for Vif-mediated degradation of A3H, and that RNA and Vif are likely to bind this single-domain DNA cytosine deaminase on physically distinct surfaces. However, a subset of the results also indicated that the A3H degradation process may be affected by A3H protein structure, subcellular localization, and differences in the constellation of A3H interaction partners, suggesting additional factors may also influence the fate and functionality of this host-pathogen interaction.
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Affiliation(s)
- Jiayi Wang
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jordan T Becker
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ke Shi
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kate V Lauer
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Daniel J Salamango
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hideki Aihara
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Nadine M Shaban
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA; Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA; Howard Hughes Medical Institute, University of Minnesota, Minneapolis, MN 55455, USA.
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7
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Pan Y, Shlyakhtenko LS, Lyubchenko YL. Insight into dynamics of APOBEC3G protein in complexes with DNA assessed by high speed AFM. NANOSCALE ADVANCES 2019; 1:4016-4024. [PMID: 33313478 PMCID: PMC7731963 DOI: 10.1039/c9na00457b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 09/03/2019] [Indexed: 06/12/2023]
Abstract
APOBEC3G (A3G) is a single-stranded DNA (ssDNA) binding protein that restricts the HIV virus by deamination of dC to dU during reverse transcription of the viral genome. A3G has two zing-binding domains: the N-terminal domain (NTD), which efficiently binds ssDNA, and the C-terminal catalytic domain (CTD), which supports deaminase activity of A3G. Until now, structural information on A3G has lacked, preventing elucidation of the molecular mechanisms underlying its interaction with ssDNA and deaminase activity. We have recently built a computational model for the full-length A3G monomer and validated its structure by data obtained from time-lapse High-Speed Atomic Force Microscopy (HS AFM). Here time-lapse HS AFM was applied to directly visualize the structure and dynamics of A3G in complexes with ssDNA. Our results demonstrate a highly dynamic structure of A3G, where two domains of the protein fluctuate between compact globular and extended dumbbell structures. Quantitative analysis of our data revealed a substantial increase in the number of A3G dumbbell structures in the presence of the DNA substrate, suggesting the interaction of A3G with the ssDNA substrate stabilizes this dumbbell structure. Based on these data, we proposed a model explaining the interaction of globular and dumbbell structures of A3G with ssDNA and suggested a possible role of the dumbbell structure in A3G function.
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Affiliation(s)
- Yangang Pan
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical CenterOmahaNebraska 68198-6025USA
| | - Luda S. Shlyakhtenko
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical CenterOmahaNebraska 68198-6025USA
| | - Yuri L. Lyubchenko
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical CenterOmahaNebraska 68198-6025USA
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8
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Fukuda H, Li S, Sardo L, Smith JL, Yamashita K, Sarca AD, Shirakawa K, Standley DM, Takaori-Kondo A, Izumi T. Structural Determinants of the APOBEC3G N-Terminal Domain for HIV-1 RNA Association. Front Cell Infect Microbiol 2019; 9:129. [PMID: 31165049 PMCID: PMC6536580 DOI: 10.3389/fcimb.2019.00129] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Accepted: 04/11/2019] [Indexed: 01/22/2023] Open
Abstract
APOBEC3G (A3G) is a cellular protein that inhibits HIV-1 infection through virion incorporation. The interaction of the A3G N-terminal domain (NTD) with RNA is essential for A3G incorporation in the HIV-1 virion. The interaction between A3G-NTD and RNA is not completely understood. The A3G-NTD is also recognized by HIV-1 Viral infectivity factor (Vif) and A3G-Vif binding leads to A3G degradation. Therefore, the A3G-Vif interaction is a target for the development of antiviral therapies that block HIV-1 replication. However, targeting the A3G-Vif interactions could disrupt the A3G-RNA interactions that are required for A3G's antiviral activity. To better understand A3G-RNA binding, we generated in silico docking models to simulate the RNA-binding propensity of A3G-NTD. We simulated the A3G-NTD residues with high RNA-binding propensity, experimentally validated our prediction by testing A3G-NTD mutations, and identified structural determinants of A3G-RNA binding. In addition, we found a novel amino acid residue, I26 responsible for RNA interaction. The new structural insights provided here will facilitate the design of pharmaceuticals that inhibit A3G-Vif interactions without negatively impacting A3G-RNA interactions.
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Affiliation(s)
- Hirofumi Fukuda
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Songling Li
- Systems Immunology Laboratory, WPI Research Center Immunology Frontier Research Center, Osaka University, Osaka, Japan.,Department of Genome Informatics, Genome Information Research Center, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Luca Sardo
- Department of Biological Sciences, McNeil Science and Technology Center, University of the Sciences, Philadelphia, PA, United States
| | - Jessica L Smith
- Molecular and Translational Sciences, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD, United States
| | - Kazuo Yamashita
- Systems Immunology Laboratory, WPI Research Center Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Anamaria D Sarca
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kotaro Shirakawa
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Daron M Standley
- Systems Immunology Laboratory, WPI Research Center Immunology Frontier Research Center, Osaka University, Osaka, Japan.,Department of Genome Informatics, Genome Information Research Center, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Akifumi Takaori-Kondo
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Taisuke Izumi
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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9
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Salter JD, Polevoda B, Bennett RP, Smith HC. Regulation of Antiviral Innate Immunity Through APOBEC Ribonucleoprotein Complexes. Subcell Biochem 2019; 93:193-219. [PMID: 31939152 DOI: 10.1007/978-3-030-28151-9_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The DNA mutagenic enzyme known as APOBEC3G (A3G) plays a critical role in innate immunity to Human Immunodeficiency Virus-1 (HIV-1 ). A3G is a zinc-dependent enzyme that mutates select deoxycytidines (dC) to deoxyuridine (dU) through deamination within nascent single stranded DNA (ssDNA) during HIV reverse transcription. This activity requires that the enzyme be delivered to viral replication complexes by redistributing from the cytoplasm of infected cells to budding virions through what appears to be an RNA-dependent process. Once inside infected cells, A3G must bind to nascent ssDNA reverse transcripts for dC to dU base modification gene editing. In this chapter we will discuss data indicating that ssDNA deaminase activity of A3G is regulated by RNA binding to A3G and ribonucleoprotein complex formation along with evidence suggesting that RNA-selective interactions with A3G are temporally and mechanistically important in this process.
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Affiliation(s)
- Jason D Salter
- OyaGen, Inc, 77 Ridgeland Road, Rochester, NY, 14623, USA
| | - Bogdan Polevoda
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Ave, Rochester, NY, 14642, USA
| | - Ryan P Bennett
- OyaGen, Inc, 77 Ridgeland Road, Rochester, NY, 14623, USA
| | - Harold C Smith
- OyaGen, Inc, 77 Ridgeland Road, Rochester, NY, 14623, USA. .,Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Ave, Rochester, NY, 14642, USA.
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10
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Salter JD, Smith HC. Modeling the Embrace of a Mutator: APOBEC Selection of Nucleic Acid Ligands. Trends Biochem Sci 2018; 43:606-622. [PMID: 29803538 PMCID: PMC6073885 DOI: 10.1016/j.tibs.2018.04.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 04/25/2018] [Accepted: 04/30/2018] [Indexed: 12/17/2022]
Abstract
The 11-member APOBEC (apolipoprotein B mRNA editing catalytic polypeptide-like) family of zinc-dependent cytidine deaminases bind to RNA and single-stranded DNA (ssDNA) and, in specific contexts, modify select (deoxy)cytidines to (deoxy)uridines. In this review, we describe advances made through high-resolution co-crystal structures of APOBECs bound to mono- or oligonucleotides that reveal potential substrate-specific binding sites at the active site and non-sequence-specific nucleic acid binding sites distal to the active site. We also discuss the effect of APOBEC oligomerization on functionality. Future structural studies will need to address how ssDNA binding away from the active site may enhance catalysis and the mechanism by which RNA binding may modulate catalytic activity on ssDNA. APOBEC proteins catalyze deamination of cytidine or deoxycytidine in either a sequence-specific or semi-specific manner on either DNA or RNA. APOBECs each possess the cytidine deaminase core fold, but sequence and structural differences among loops surrounding the zinc-dependent active site impart differences in sequence-dependent target preferences, binding affinity, catalytic rate, and regulation of substrate access to the active site among the 11 family members. APOBECs also regulate the deamination reaction through additional nucleic acid substrate binding sites located within surface grooves or patches of positive electrostatic potential that are distal to the active site but may do so nonspecifically. Binding of nonsubstrate RNA and RNA-mediated oligomerization by APOBECs that deaminate ssDNA downregulates catalytic activity but also controls APOBEC subcellular or virion localization. The presence of a second, though noncatalytic, cytidine deaminase domain for some APOBECs and the ability of some APOBECs to oligomerize add additional molecular surfaces for positive or negative regulation of catalysis through nucleic acid binding.
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Affiliation(s)
- Jason D Salter
- OyaGen, Inc., 77 Ridgeland Road, Rochester, NY 14623, USA.
| | - Harold C Smith
- OyaGen, Inc., 77 Ridgeland Road, Rochester, NY 14623, USA; University of Rochester, School of Medicine and Dentistry, Department of Biochemistry and Biophysics, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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11
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King JJ, Larijani M. A Novel Regulator of Activation-Induced Cytidine Deaminase/APOBECs in Immunity and Cancer: Schrödinger's CATalytic Pocket. Front Immunol 2017; 8:351. [PMID: 28439266 PMCID: PMC5382155 DOI: 10.3389/fimmu.2017.00351] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 03/10/2017] [Indexed: 12/20/2022] Open
Abstract
Activation-induced cytidine deaminase (AID) and its relative APOBEC3 cytidine deaminases boost immune response by mutating immune or viral genes. Because of their genome-mutating activities, AID/APOBECs are also drivers of tumorigenesis. Due to highly charged surfaces, extensive non-specific protein-protein/nucleic acid interactions, formation of polydisperse oligomers, and general insolubility, structure elucidation of these proteins by X-ray crystallography and NMR has been challenging. Hence, almost all available AID/APOBEC structures are of mutated and/or truncated versions. In 2015, we reported a functional structure for AID using a combined computational-biochemical approach. In so doing, we described a new regulatory mechanism that is a first for human DNA/RNA-editing enzymes. This mechanism involves dynamic closure of the catalytic pocket. Subsequent X-ray and NMR studies confirmed our discovery by showing that other APOBEC3s also close their catalytic pockets. Here, we highlight catalytic pocket closure as an emerging and important regulatory mechanism of AID/APOBEC3s. We focus on three sub-topics: first, we propose that variable pocket closure rates across AID/APOBEC3s underlie differential activity in immunity and cancer and review supporting evidence. Second, we discuss dynamic pocket closure as an ever-present internal regulator, in contrast to other proposed regulatory mechanisms that involve extrinsic binding partners. Third, we compare the merits of classical approaches of X-ray and NMR, with that of emerging computational-biochemical approaches, for structural elucidation specifically for AID/APOBEC3s.
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Affiliation(s)
- Justin J. King
- Immunology and Infectious Diseases Program, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Mani Larijani
- Immunology and Infectious Diseases Program, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
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Polevoda B, Joseph R, Friedman AE, Bennett RP, Greiner R, De Zoysa T, Stewart RA, Smith HC. DNA mutagenic activity and capacity for HIV-1 restriction of the cytidine deaminase APOBEC3G depend on whether DNA or RNA binds to tyrosine 315. J Biol Chem 2017; 292:8642-8656. [PMID: 28381554 DOI: 10.1074/jbc.m116.767889] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 04/04/2017] [Indexed: 12/23/2022] Open
Abstract
APOBEC3G (A3G) belongs to the AID/APOBEC protein family of cytidine deaminases (CDA) that bind to nucleic acids. A3G mutates the HIV genome by deamination of dC to dU, leading to accumulation of virus-inactivating mutations. Binding to cellular RNAs inhibits A3G binding to substrate single-stranded (ss) DNA and CDA activity. Bulk RNA and substrate ssDNA bind to the same three A3G tryptic peptides (amino acids 181-194, 314-320, and 345-374) that form parts of a continuously exposed protein surface extending from the catalytic domain in the C terminus of A3G to its N terminus. We show here that the A3G tyrosines 181 and 315 directly cross-linked ssDNA. Binding experiments showed that a Y315A mutation alone significantly reduced A3G binding to both ssDNA and RNA, whereas Y181A and Y182A mutations only moderately affected A3G nucleic acid binding. Consistent with these findings, the Y315A mutant exhibited little to no deaminase activity in an Escherichia coli DNA mutator reporter, whereas Y181A and Y182A mutants retained ∼50% of wild-type A3G activity. The Y315A mutant also showed a markedly reduced ability to assemble into viral particles and had reduced antiviral activity. In uninfected cells, the impaired RNA-binding capacity of Y315A was evident by a shift of A3G from high-molecular-mass ribonucleoprotein complexes to low-molecular-mass complexes. We conclude that Tyr-315 is essential for coordinating ssDNA interaction with or entry to the deaminase domain and hypothesize that RNA bound to Tyr-315 may be sufficient to competitively inhibit ssDNA deaminase-dependent antiviral activity.
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Affiliation(s)
- Bogdan Polevoda
- From the Departments of Biochemistry and Biophysics and.,Center for RNA Biology, and
| | | | | | | | | | | | | | - Harold C Smith
- From the Departments of Biochemistry and Biophysics and .,Center for RNA Biology, and.,OyaGen, Inc., Rochester, New York 14623.,Center for AIDS Research, University of Rochester Medical Center, Rochester, New York 14642 and
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Pan Y, Sun Z, Maiti A, Kanai T, Matsuo H, Li M, Harris RS, Shlyakhtenko LS, Lyubchenko YL. Nanoscale Characterization of Interaction of APOBEC3G with RNA. Biochemistry 2017; 56:1473-1481. [PMID: 28029777 DOI: 10.1021/acs.biochem.6b01189] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human cytidine deaminase APOBEC3G (A3G) is a potent inhibitor of the HIV-1 virus in the absence of viral infectivity factor (Vif). The molecular mechanism of A3G antiviral activity is primarily attributed to deamination of single-stranded DNA (ssDNA); however, the nondeamination mechanism also contributes to HIV-1 restriction. The interaction of A3G with ssDNA and RNA is required for its antiviral activity. Here we used atomic force microscopy to directly visualize A3G-RNA and A3G-ssDNA complexes and compare them to each other. Our results showed that A3G in A3G-RNA complexes exists primarily in monomeric-dimeric states, similar to its stoichiometry in complexes with ssDNA. New A3G-RNA complexes in which A3G binds to two RNA molecules were identified. These data suggest the existence of two separate RNA binding sites on A3G. Such complexes were not observed with ssDNA substrates. Time-lapse high-speed atomic force microscopy was applied to characterize the dynamics of the complexes. The data revealed that the two RNA binding sites have different affinities for A3G. On the basis of the obtained results, a model for the interaction of A3G with RNA is proposed.
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Affiliation(s)
- Yangang Pan
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical Center , 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, United States
| | - Zhiqiang Sun
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical Center , 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, United States
| | - Atanu Maiti
- Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc. , Advanced Technology Research Facility, 8560 Progress Drive, Frederick, Maryland 21702, United States
| | - Tapan Kanai
- Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc. , Advanced Technology Research Facility, 8560 Progress Drive, Frederick, Maryland 21702, United States
| | - Hiroshi Matsuo
- Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc. , Advanced Technology Research Facility, 8560 Progress Drive, Frederick, Maryland 21702, United States
| | - Ming Li
- Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Center for Genome Engineering, Masonic Cancer Center, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Center for Genome Engineering, Masonic Cancer Center, University of Minnesota , Minneapolis, Minnesota 55455, United States.,Howard Hughes Medical Institute, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Luda S Shlyakhtenko
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical Center , 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, United States
| | - Yuri L Lyubchenko
- Department of Pharmaceutical Sciences, College of Pharmacy, WSH, University of Nebraska Medical Center , 986025 Nebraska Medical Center, Omaha, Nebraska 68198-6025, United States
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Abstract
Apolipoprotein B mRNA Editing Catalytic Polypeptide-like 1 or APOBEC1 was discovered in 1993 as the zinc-dependent cytidine deaminase responsible for the production of an in frame stop codon in apoB mRNA through modification of cytidine at nucleotide position 6666 to uridine. At the time of this discovery there was much speculation concerning the mechanism of base modification RNA editing which has been rekindled by the discovery of multiple C to U RNA editing events in the 3′ UTRs of mRNAs and the finding that other members of the APOBEC family while able to bind RNA, have the biological function of being DNA mutating enzymes. Current research is addressing the mechanism for these nucleotide modification events that appear not to adhere to the mooring sequence-dependent model for APOBEC1 involving the assembly of a multi protein containing editosome. This review will summarize our current understanding of the structure and function of APOBEC proteins and examine how RNA binding to them may be a regulatory mechanism.
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Affiliation(s)
- Harold C Smith
- a University of Rochester, School of Medicine and Dentistry , Department of Biochemistry and Biophysics , Rochester , NY , USA
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15
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Polevoda B, McDougall WM, Tun BN, Cheung M, Salter JD, Friedman AE, Smith HC. RNA binding to APOBEC3G induces the disassembly of functional deaminase complexes by displacing single-stranded DNA substrates. Nucleic Acids Res 2015; 43:9434-45. [PMID: 26424853 PMCID: PMC4627094 DOI: 10.1093/nar/gkv970] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 09/14/2015] [Accepted: 09/15/2015] [Indexed: 11/14/2022] Open
Abstract
APOBEC3G (A3G) DNA deaminase activity requires a holoenzyme complex whose assembly on nascent viral reverse transcripts initiates with A3G dimers binding to ssDNA followed by formation of higher-order A3G homo oligomers. Catalytic activity is inhibited when A3G binds to RNA. Our prior studies suggested that RNA inhibited A3G binding to ssDNA. In this report, near equilibrium binding and gel shift analyses showed that A3G assembly and disassembly on ssDNA was an ordered process involving A3G dimers and multimers thereof. Although, fluorescence anisotropy showed that A3G had similar nanomolar affinity for RNA and ssDNA, RNA stochastically dissociated A3G dimers and higher-order oligomers from ssDNA, suggesting a different modality for RNA binding. Mass spectrometry mapping of A3G peptides cross-linked to nucleic acid suggested ssDNA only bound to three peptides, amino acids (aa) 181-194 in the N-terminus and aa 314-320 and 345-374 in the C-terminus that were part of a continuous exposed surface. RNA bound to these peptides and uniquely associated with three additional peptides in the N- terminus, aa 15-29, 41-52 and 83-99, that formed a continuous surface area adjacent to the ssDNA binding surface. The data predict a mechanistic model of RNA inhibition of ssDNA binding to A3G in which competitive and allosteric interactions determine RNA-bound versus ssDNA-bound conformational states.
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Affiliation(s)
- Bogdan Polevoda
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA Center for RNA Biology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - William M McDougall
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA Center for RNA Biology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Bradley N Tun
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Michael Cheung
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Jason D Salter
- OyaGen, Inc, Rochester BioVenture Center, 77 Ridgeland Road, Rochester, NY 14623, USA
| | - Alan E Friedman
- Environmental Health Sciences Center, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Harold C Smith
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA Center for RNA Biology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA OyaGen, Inc, Rochester BioVenture Center, 77 Ridgeland Road, Rochester, NY 14623, USA Environmental Health Sciences Center, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA Center for AIDS Research, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
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