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Arribas L, Menéndez-Arias L, Betancor G. May I Help You with Your Coat? HIV-1 Capsid Uncoating and Reverse Transcription. Int J Mol Sci 2024; 25:7167. [PMID: 39000271 PMCID: PMC11241228 DOI: 10.3390/ijms25137167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2024] [Revised: 06/26/2024] [Accepted: 06/27/2024] [Indexed: 07/16/2024] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) capsid is a protein core formed by multiple copies of the viral capsid (CA) protein. Inside the capsid, HIV-1 harbours all the viral components required for replication, including the genomic RNA and viral enzymes reverse transcriptase (RT) and integrase (IN). Upon infection, the RT transforms the genomic RNA into a double-stranded DNA molecule that is subsequently integrated into the host chromosome by IN. For this to happen, the viral capsid must open and release the viral DNA, in a process known as uncoating. Capsid plays a key role during the initial stages of HIV-1 replication; therefore, its stability is intimately related to infection efficiency, and untimely uncoating results in reverse transcription defects. How and where uncoating takes place and its relationship with reverse transcription is not fully understood, but the recent development of novel biochemical and cellular approaches has provided unprecedented detail on these processes. In this review, we present the latest findings on the intricate link between capsid stability, reverse transcription and uncoating, the different models proposed over the years for capsid uncoating, and the role played by other cellular factors on these processes.
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Affiliation(s)
- Laura Arribas
- Instituto Universitario de Investigaciones Biomédicas y Sanitarias (IUIBS), Universidad de Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Spain;
| | - Luis Menéndez-Arias
- Centro de Biología Molecular “Severo Ochoa” (Consejo Superior de Investigaciones Científicas & Universidad Autónoma de Madrid), 28049 Madrid, Spain;
| | - Gilberto Betancor
- Instituto Universitario de Investigaciones Biomédicas y Sanitarias (IUIBS), Universidad de Las Palmas de Gran Canaria, 35016 Las Palmas de Gran Canaria, Spain;
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2
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Zhu T, Niu G, Zhang Y, Chen M, Li CY, Hao L, Zhang Z. Host-mediated RNA editing in viruses. Biol Direct 2023; 18:12. [PMID: 36978112 PMCID: PMC10043548 DOI: 10.1186/s13062-023-00366-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 03/17/2023] [Indexed: 03/30/2023] Open
Abstract
Viruses rely on hosts for life and reproduction, cause a variety of symptoms from common cold to AIDS to COVID-19 and provoke public health threats claiming millions of lives around the globe. RNA editing, as a crucial co-/post-transcriptional modification inducing nucleotide alterations on both endogenous and exogenous RNA sequences, exerts significant influences on virus replication, protein synthesis, infectivity and toxicity. Hitherto, a number of host-mediated RNA editing sites have been identified in diverse viruses, yet lacking a full picture of RNA editing-associated mechanisms and effects in different classes of viruses. Here we synthesize the current knowledge of host-mediated RNA editing in a variety of viruses by considering two enzyme families, viz., ADARs and APOBECs, thereby presenting a landscape of diverse editing mechanisms and effects between viruses and hosts. In the ongoing pandemic, our study promises to provide potentially valuable insights for better understanding host-mediated RNA editing on ever-reported and newly-emerging viruses.
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Affiliation(s)
- Tongtong Zhu
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
- China National Center for Bioinformation, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Guangyi Niu
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
- China National Center for Bioinformation, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yuansheng Zhang
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
- China National Center for Bioinformation, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ming Chen
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
- China National Center for Bioinformation, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chuan-Yun Li
- Laboratory of Bioinformatics and Genomic Medicine, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing, 100871, China
| | - Lili Hao
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China.
- China National Center for Bioinformation, Beijing, 100101, China.
| | - Zhang Zhang
- National Genomics Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China.
- China National Center for Bioinformation, Beijing, 100101, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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3
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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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Upstream of N-Ras (Unr/CSDE1) Interacts with NCp7 and Gag, Modulating HIV-1 IRES-Mediated Translation Initiation. Viruses 2022; 14:v14081798. [PMID: 36016420 PMCID: PMC9413769 DOI: 10.3390/v14081798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/11/2022] [Accepted: 08/15/2022] [Indexed: 11/25/2022] Open
Abstract
The Human Immunodeficiency Virus-1 (HIV-1) nucleocapsid protein (NC) as a mature protein or as a domain of the Gag precursor plays important roles in the early and late phases of the infection. To better understand its roles, we searched for new cellular partners and identified the RNA-binding protein Unr/CSDE1, Upstream of N-ras, whose interaction with Gag and NCp7 was confirmed by co-immunoprecipitation and FRET-FLIM. Unr interaction with Gag was found to be RNA-dependent and mediated by its NC domain. Using a dual luciferase assay, Unr was shown to act as an ITAF (IRES trans-acting factor), increasing the HIV-1 IRES-dependent translation. Point mutations of the HIV-1 IRES in a consensus Unr binding motif were found to alter both the IRES activity and its activation by Unr, suggesting a strong dependence of the IRES on Unr. Interestingly, Unr stimulatory effect is counteracted by NCp7, while Gag increases the Unr-promoted IRES activity, suggesting a differential Unr effect on the early and late phases of viral infection. Finally, knockdown of Unr in HeLa cells leads to a decrease in infection by a non-replicative lentivector, proving its functional implication in the early phase of viral infection.
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Repair of APOBEC3G-Mutated Retroviral DNA In Vivo Is Facilitated by the Host Enzyme Uracil DNA Glycosylase 2. J Virol 2021; 95:e0124421. [PMID: 34468176 DOI: 10.1128/jvi.01244-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apolipoprotein B mRNA editing enzyme catalytic subunit 3 (APOBEC3) proteins are critical for the control of infection by retroviruses. These proteins deaminate cytidines in negative-strand DNA during reverse transcription, leading to G-to-A changes in coding strands. Uracil DNA glycosylase (UNG) is a host enzyme that excises uracils in genomic DNA, which the base excision repair machinery then repairs. Whether UNG removes uracils found in retroviral DNA after APOBEC3-mediated mutation is not clear, and whether this occurs in vivo has not been demonstrated. To determine if UNG plays a role in the repair of retroviral DNA, we used APOBEC3G (A3G) transgenic mice which we showed previously had extensive deamination of murine leukemia virus (MLV) proviruses. The A3G transgene was crossed onto an Ung and mouse Apobec3 knockout background (UNG-/-APO-/-), and the mice were infected with MLV. We found that virus infection levels were decreased in A3G UNG-/-APO-/- compared with A3G APO-/- mice. Deep sequencing of the proviruses showed that there were significantly higher levels of G-to-A mutations in proviral DNA from A3G transgenic UNG-/-APO-/- than A3G transgenic APO-/- mice, suggesting that UNG plays a role in the repair of uracil-containing proviruses. In in vitro studies, we found that cytoplasmic viral DNA deaminated by APOBEC3G was uracilated. In the absence of UNG, the uracil-containing proviruses integrated at higher levels into the genome than those made in the presence of UNG. Thus, UNG also functions in the nucleus prior to integration by nicking uracil-containing viral DNA, thereby blocking integration. These data show that UNG plays a critical role in the repair of the damage inflicted by APOBEC3 deamination of reverse-transcribed DNA. IMPORTANCE While APOBEC3-mediated mutation of retroviruses is well-established, what role the host base excision repair enzymes play in correcting these mutations is not clear. This question is especially difficult to address in vivo. Here, we use a transgenic mouse developed by our lab that expresses human APOBEC3G and also lacks the endogenous uracil DNA glycosylase (Ung) gene and show that UNG removes uracils introduced by this cytidine deaminase in MLV reverse transcripts, thereby reducing G-to-A mutations in proviruses. Furthermore, our data suggest that UNG removes uracils at two stages in infection-first, in unintegrated nuclear viral reverse-transcribed DNA, resulting in its degradation; and second, in integrated proviruses, resulting in their repair. These data suggest that retroviruses damaged by host cytidine deaminases take advantage of the host DNA repair system to overcome this damage.
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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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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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Hakata Y, Miyazawa M. Deaminase-Independent Mode of Antiretroviral Action in Human and Mouse APOBEC3 Proteins. Microorganisms 2020; 8:microorganisms8121976. [PMID: 33322756 PMCID: PMC7764128 DOI: 10.3390/microorganisms8121976] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 12/09/2020] [Indexed: 02/06/2023] Open
Abstract
Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3) proteins (APOBEC3s) are deaminases that convert cytosines to uracils predominantly on a single-stranded DNA, and function as intrinsic restriction factors in the innate immune system to suppress replication of viruses (including retroviruses) and movement of retrotransposons. Enzymatic activity is supposed to be essential for the APOBEC3 antiviral function. However, it is not the only way that APOBEC3s exert their biological function. Since the discovery of human APOBEC3G as a restriction factor for HIV-1, the deaminase-independent mode of action has been observed. At present, it is apparent that both the deaminase-dependent and -independent pathways are tightly involved not only in combating viruses but also in human tumorigenesis. Although the deaminase-dependent pathway has been extensively characterized so far, understanding of the deaminase-independent pathway remains immature. Here, we review existing knowledge regarding the deaminase-independent antiretroviral functions of APOBEC3s and their molecular mechanisms. We also discuss the possible unidentified molecular mechanism for the deaminase-independent antiretroviral function mediated by mouse APOBEC3.
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Affiliation(s)
- Yoshiyuki Hakata
- Department of Immunology, Kindai University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511, Japan;
- Correspondence: ; Tel.: +81-72-367-7660
| | - Masaaki Miyazawa
- Department of Immunology, Kindai University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511, Japan;
- Kindai University Anti-Aging Center, 3-4-1 Kowakae, Higashiosaka, Osaka 577-8502, Japan
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9
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The Role of APOBECs in Viral Replication. Microorganisms 2020; 8:microorganisms8121899. [PMID: 33266042 PMCID: PMC7760323 DOI: 10.3390/microorganisms8121899] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/25/2020] [Accepted: 11/26/2020] [Indexed: 12/14/2022] Open
Abstract
Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) proteins are a diverse and evolutionarily conserved family of cytidine deaminases that provide a variety of functions from tissue-specific gene expression and immunoglobulin diversity to control of viruses and retrotransposons. APOBEC family expansion has been documented among mammalian species, suggesting a powerful selection for their activity. Enzymes with a duplicated zinc-binding domain often have catalytically active and inactive domains, yet both have antiviral function. Although APOBEC antiviral function was discovered through hypermutation of HIV-1 genomes lacking an active Vif protein, much evidence indicates that APOBECs also inhibit virus replication through mechanisms other than mutagenesis. Multiple steps of the viral replication cycle may be affected, although nucleic acid replication is a primary target. Packaging of APOBECs into virions was first noted with HIV-1, yet is not a prerequisite for viral inhibition. APOBEC antagonism may occur in viral producer and recipient cells. Signatures of APOBEC activity include G-to-A and C-to-T mutations in a particular sequence context. The importance of APOBEC activity for viral inhibition is reflected in the identification of numerous viral factors, including HIV-1 Vif, which are dedicated to antagonism of these deaminases. Such viral antagonists often are only partially successful, leading to APOBEC selection for viral variants that enhance replication or avoid immune elimination.
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Maiti A, Myint W, Delviks-Frankenberry KA, Hou S, Kanai T, Balachandran V, Sierra Rodriguez C, Tripathi R, Kurt Yilmaz N, Pathak VK, Schiffer CA, Matsuo H. Crystal Structure of a Soluble APOBEC3G Variant Suggests ssDNA to Bind in a Channel that Extends between the Two Domains. J Mol Biol 2020; 432:6042-6060. [PMID: 33098858 DOI: 10.1016/j.jmb.2020.10.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/09/2020] [Accepted: 10/16/2020] [Indexed: 11/16/2022]
Abstract
APOBEC3G (A3G) is a single-stranded DNA (ssDNA) cytosine deaminase that can restrict HIV-1 infection by mutating the viral genome. A3G consists of a non-catalytic N-terminal domain (NTD) and a catalytic C-terminal domain (CTD) connected by a short linker. While the CTD catalyzes cytosine deamination, the NTD is believed to provide additional affinity for ssDNA. Structures of both A3G domains have been solved individually; however, a full-length A3G structure has been challenging. Recently, crystal structures of full-length rhesus macaque A3G variants were solved which suggested dimerization mechanisms and RNA binding surfaces, whereas the dimerization appeared to compromise catalytic activity. We determined the crystal structure of a soluble variant of human A3G (sA3G) at 2.5 Å and from these data generated a model structure of wild-type A3G. This model demonstrated that the NTD was rotated 90° relative to the CTD along the major axis of the molecule, an orientation that forms a positively charged channel connected to the CTD catalytic site, consisting of NTD loop-1 and CTD loop-3. Structure-based mutations, in vitro deamination and DNA binding assays, and HIV-1 restriction assays identify R24, located in the NTD loop-1, as essential to a critical interaction with ssDNA. Furthermore, sA3G was shown to bind a deoxy-cytidine dinucleotide near the catalytic Zn2+, yet not in the catalytic position, where the interactions between deoxy-cytidines and CTD loop-1 and loop-7 residues were different from those formed with substrate. These new interactions suggest a mechanism explaining why A3G exhibits a 3' to 5' directional preference in processive deamination.
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Affiliation(s)
- Atanu Maiti
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Wazo Myint
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Krista A Delviks-Frankenberry
- Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Shurong Hou
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Tapan Kanai
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA; Department of Chemistry, Banasthali University, Banasthali 304022, Rajasthan, India
| | | | | | - Rashmi Tripathi
- Department of Bioscience and Biotechnology, Banasthali University, Banasthali 304022, Rajasthan, India
| | - Nese Kurt Yilmaz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Vinay K Pathak
- Viral Mutation Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Celia A Schiffer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Hiroshi Matsuo
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA.
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11
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Jaguva Vasudevan AA, Balakrishnan K, Gertzen CGW, Borvető F, Zhang Z, Sangwiman A, Held U, Küstermann C, Banerjee S, Schumann GG, Häussinger D, Bravo IG, Gohlke H, Münk C. Loop 1 of APOBEC3C Regulates its Antiviral Activity against HIV-1. J Mol Biol 2020; 432:6200-6227. [PMID: 33068636 DOI: 10.1016/j.jmb.2020.10.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 10/09/2020] [Accepted: 10/09/2020] [Indexed: 01/10/2023]
Abstract
APOBEC3 deaminases (A3s) provide mammals with an anti-retroviral barrier by catalyzing dC-to-dU deamination on viral ssDNA. Within primates, A3s have undergone a complex evolution via gene duplications, fusions, arms race, and selection. Human APOBEC3C (hA3C) efficiently restricts the replication of viral infectivity factor (vif)-deficient Simian immunodeficiency virus (SIVΔvif), but for unknown reasons, it inhibits HIV-1Δvif only weakly. In catarrhines (Old World monkeys and apes), the A3C loop 1 displays the conserved amino acid pair WE, while the corresponding consensus sequence in A3F and A3D is the largely divergent pair RK, which is also the inferred ancestral sequence for the last common ancestor of A3C and of the C-terminal domains of A3D and A3F in primates. Here, we report that modifying the WE residues in hA3C loop 1 to RK leads to stronger interactions with substrate ssDNA, facilitating catalytic function, which results in a drastic increase in both deamination activity and in the ability to restrict HIV-1 and LINE-1 replication. Conversely, the modification hA3F_WE resulted only in a marginal decrease in HIV-1Δvif inhibition. We propose that the two series of ancestral gene duplications that generated A3C, A3D-CTD and A3F-CTD allowed neo/subfunctionalization: A3F-CTD maintained the ancestral RK residues in loop 1, while diversifying selection resulted in the RK → WE modification in Old World anthropoids' A3C, possibly allowing for novel substrate specificity and function.
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Affiliation(s)
- Ananda Ayyappan Jaguva Vasudevan
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
| | - Kannan Balakrishnan
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; Department of Biochemistry, School of Life Sciences, University of Hyderabad, Gachibowli, Hyderabad, India
| | - Christoph G W Gertzen
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre & Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Jülich, Germany; Center for Structural Studies (CSS), Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Fanni Borvető
- Centre National de la Recherche Scientifique, Laboratory MIVEGEC (CNRS, IRD, Uni Montpellier), Montpellier, France
| | - Zeli Zhang
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Anucha Sangwiman
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Ulrike Held
- Division of Medical Biotechnology, Paul-Ehrlich-Institute, Langen, Germany
| | | | - Sharmistha Banerjee
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Gachibowli, Hyderabad, India
| | - Gerald G Schumann
- Division of Medical Biotechnology, Paul-Ehrlich-Institute, Langen, Germany
| | - Dieter Häussinger
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Ignacio G Bravo
- Centre National de la Recherche Scientifique, Laboratory MIVEGEC (CNRS, IRD, Uni Montpellier), Montpellier, France
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany; John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre & Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Carsten Münk
- Clinic for Gastroenterology, Hepatology, and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
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12
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Hakata Y, Li J, Fujino T, Tanaka Y, Shimizu R, Miyazawa M. Mouse APOBEC3 interferes with autocatalytic cleavage of murine leukemia virus Pr180gag-pol precursor and inhibits Pr65gag processing. PLoS Pathog 2019; 15:e1008173. [PMID: 31830125 PMCID: PMC6907756 DOI: 10.1371/journal.ppat.1008173] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/30/2019] [Indexed: 01/01/2023] Open
Abstract
Mouse APOBEC3 (mA3) inhibits murine leukemia virus (MuLV) replication by a deamination-independent mechanism in which the reverse transcription is considered the main target process. However, other steps in virus replication that can be targeted by mA3 have not been examined. We have investigated the possible effect of mA3 on MuLV protease-mediated processes and found that mA3 binds both mature viral protease and Pr180gag-pol precursor polyprotein. Using replication-competent MuLVs, we also show that mA3 inhibits the processing of Pr65 Gag precursor. Furthermore, we demonstrate that the autoprocessing of Pr180gag-pol is impeded by mA3, resulting in reduced production of mature viral protease. This reduction appears to link with the above inefficient Pr65gag processing in the presence of mA3. Two major isoforms of mA3, exon 5-containing and -lacking ones, equally exhibit this antiviral activity. Importantly, physiologically expressed levels of mA3 impedes both Pr180gag-pol autocatalysis and Pr65gag processing. This blockade is independent of the deaminase activity and requires the C-terminal region of mA3. These results suggest that the above impairment of Pr180gag-pol autoprocessing may significantly contribute to the deaminase-independent antiretroviral activity exerted by mA3. Soon after the identification of the polynucleotide cytidine deaminase APOBEC3 as a host restriction factor against vif-deficient HIV, it was noticed that deamination-independent mechanisms are involved in the inhibition of viral replication in addition to the deaminase-dependent mechanism. We previously showed that mouse APOBEC3 (mA3) physiologically restricted mouse retrovirus replication in their natural hosts without causing significant G-to-A hypermutations. Inhibition of reverse transcription is reported to be the most plausible mechanism for the deamination-independent antiretroviral function. However, it remains unknown whether the inhibition of reverse transcription is the only way to explain the whole picture of deamination-independent antiviral activity exerted by APOBEC3. Here we show that mA3 targets the autoprocessing of Pr180gag-pol polyprotein. This activity does not require the deaminase catalytic center and mainly exerted by the C-terminal half of mA3. mA3 physically interacts with murine retroviral protease and its precursor Pr180gag-pol. mA3-induced disruption of the autocatalytic Pr180gag-pol cleavage leads to a significant reduction of mature viral protease, resulting in the inhibition of Pr65gag processing to mature Gag proteins. As the Pr180gag-pol autoprocessing is necessary for the maturation of other viral enzymes including the reverse transcriptase, its inhibition by host APOBEC3 may precede the previously described impairment of reverse transcription. Our discovery may lead to the development of novel antiretroviral drugs through the future identification of detailed molecular interfaces between retroviral Gag-Pol polyprotein and APOBEC3.
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Affiliation(s)
- Yoshiyuki Hakata
- Department of Immunology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, Japan
- * E-mail: (YH); (MM)
| | - Jun Li
- Department of Immunology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, Japan
- Ijunkai Medical Oncology, Endoscopy Clinic, Sakai-ku, Sakai, Osaka, Japan
| | - Takahiro Fujino
- Division of Analytical Bio-Medicine, Advanced Research Support Center (ADRES), Ehime University, Shitsukawa, Toon, Ehime, Japan
| | - Yuki Tanaka
- Division of Analytical Bio-Medicine, Advanced Research Support Center (ADRES), Ehime University, Shitsukawa, Toon, Ehime, Japan
| | - Rie Shimizu
- Department of Immunology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, Japan
| | - Masaaki Miyazawa
- Department of Immunology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, Japan
- Kindai University Anti-Aging Center, Higashiosaka, Osaka, Japan
- * E-mail: (YH); (MM)
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13
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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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14
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Crystal Structure of Cytidine Deaminase Human APOBEC3F Chimeric Catalytic Domain in Complex with DNA. CHINESE J CHEM 2018. [DOI: 10.1002/cjoc.201800508] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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15
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Pollpeter D, Parsons M, Sobala AE, Coxhead S, Lang RD, Bruns AM, Papaioannou S, McDonnell JM, Apolonia L, Chowdhury JA, Horvath CM, Malim MH. Deep sequencing of HIV-1 reverse transcripts reveals the multifaceted antiviral functions of APOBEC3G. Nat Microbiol 2018; 3:220-233. [PMID: 29158605 PMCID: PMC6014619 DOI: 10.1038/s41564-017-0063-9] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/10/2017] [Indexed: 12/15/2022]
Abstract
Following cell entry, the RNA genome of HIV-1 is reverse transcribed into double-stranded DNA that ultimately integrates into the host-cell genome to establish the provirus. These early phases of infection are notably vulnerable to suppression by a collection of cellular antiviral effectors, called restriction or resistance factors. The host antiviral protein APOBEC3G (A3G) antagonizes the early steps of HIV-1 infection through the combined effects of inhibiting viral cDNA production and cytidine-to-uridine-driven hypermutation of this cDNA. In seeking to address the underlying molecular mechanism for inhibited cDNA synthesis, we developed a deep sequencing strategy to characterize nascent reverse transcription products and their precise 3'-termini in HIV-1 infected T cells. Our results demonstrate site- and sequence-independent interference with reverse transcription, which requires the specific interaction of A3G with reverse transcriptase itself. This approach also established, contrary to current ideas, that cellular uracil base excision repair (UBER) enzymes target and cleave A3G-edited uridine-containing viral cDNA. Together, these findings yield further insights into the regulatory interplay between reverse transcriptase, A3G and cellular DNA repair machinery, and identify the suppression of HIV-1 reverse transcriptase by a directly interacting host protein as a new cell-mediated antiviral mechanism.
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Affiliation(s)
- Darja Pollpeter
- Department of Infectious Diseases, King's College London, London, UK
| | - Maddy Parsons
- Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
| | - Andrew E Sobala
- Department of Infectious Diseases, King's College London, London, UK
| | - Sashika Coxhead
- Department of Infectious Diseases, King's College London, London, UK
| | - Rupert D Lang
- Department of Infectious Diseases, King's College London, London, UK
| | - Annie M Bruns
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | | | - James M McDonnell
- Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
| | - Luis Apolonia
- Department of Infectious Diseases, King's College London, London, UK
| | - Jamil A Chowdhury
- Department of Infectious Diseases, King's College London, London, UK
| | - Curt M Horvath
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Michael H Malim
- Department of Infectious Diseases, King's College London, London, UK.
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16
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APOBEC Enzymes as Targets for Virus and Cancer Therapy. Cell Chem Biol 2017; 25:36-49. [PMID: 29153851 DOI: 10.1016/j.chembiol.2017.10.007] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 09/11/2017] [Accepted: 10/18/2017] [Indexed: 01/08/2023]
Abstract
Human DNA cytosine-to-uracil deaminases catalyze mutations in both pathogen and cellular genomes. APOBEC3D, APOBEC3F, APOBEC3G, and APOBEC3H restrict human immunodeficiency virus 1 (HIV-1) infection in cells deficient in the viral infectivity factor (Vif), and have the potential to catalyze sublethal levels of mutation in viral genomes in Vif-proficient cells. At least two APOBEC3 enzymes, and in particular APOBEC3B, are sources of somatic mutagenesis in cancer cells that drive tumor evolution and may manifest clinically as recurrence, metastasis, and/or therapy resistance. Consequently, APOBEC3 enzymes are tantalizing targets for developing chemical probes and therapeutic molecules to harness mutational processes in human disease. This review highlights recent efforts to chemically manipulate APOBEC3 activities.
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17
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Jaguva Vasudevan AA, Hofmann H, Willbold D, Häussinger D, Koenig BW, Münk C. Enhancing the Catalytic Deamination Activity of APOBEC3C Is Insufficient to Inhibit Vif-Deficient HIV-1. J Mol Biol 2017; 429:1171-1191. [DOI: 10.1016/j.jmb.2017.03.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/08/2017] [Accepted: 03/08/2017] [Indexed: 12/17/2022]
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18
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Zhou M, Luo RH, Hou XY, Wang RR, Yan GY, Chen H, Zhang RH, Shi JY, Zheng YT, Li R, Wei YQ. Synthesis, biological evaluation and molecular docking study of N -(2-methoxyphenyl)-6-((4-nitrophenyl)sulfonyl)benzamide derivatives as potent HIV-1 Vif antagonists. Eur J Med Chem 2017; 129:310-324. [DOI: 10.1016/j.ejmech.2017.01.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 01/06/2017] [Accepted: 01/08/2017] [Indexed: 01/28/2023]
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19
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Okada A, Iwatani Y. APOBEC3G-Mediated G-to-A Hypermutation of the HIV-1 Genome: The Missing Link in Antiviral Molecular Mechanisms. Front Microbiol 2016; 7:2027. [PMID: 28066353 PMCID: PMC5165236 DOI: 10.3389/fmicb.2016.02027] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/02/2016] [Indexed: 12/20/2022] Open
Abstract
APOBEC3G (A3G) is a member of the cellular polynucleotide cytidine deaminases, which catalyze the deamination of cytosine (dC) to uracil (dU) in single-stranded DNA. These enzymes potently inhibit the replication of a variety of retroviruses and retrotransposons, including HIV-1. A3G is incorporated into vif-deficient HIV-1 virions and targets viral reverse transcripts, particularly minus-stranded DNA products, in newly infected cells. It is well established that the enzymatic activity of A3G is closely correlated with the potential to greatly inhibit HIV-1 replication in the absence of Vif. However, the details of the underlying molecular mechanisms are not fully understood. One potential mechanism of A3G antiviral activity is that the A3G-dependent deamination may trigger degradation of the dU-containing reverse transcripts by cellular uracil DNA glycosylases (UDGs). More recently, another mechanism has been suggested, in which the virion-incorporated A3G generates lethal levels of the G-to-A hypermutation in the viral DNA genome, thus potentially driving the viruses into “error catastrophe” mode. In this mini review article, we summarize the deaminase-dependent and deaminase-independent molecular mechanisms of A3G and discuss how A3G-mediated deamination is linked to antiviral mechanisms.
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Affiliation(s)
- Ayaka Okada
- Department of Microbiology and Immunology, Laboratory of Infectious Diseases, Clinical Research Center, National Hospital Organization Nagoya Medical Center Nagoya, Japan
| | - Yasumasa Iwatani
- Department of Microbiology and Immunology, Laboratory of Infectious Diseases, Clinical Research Center, National Hospital Organization Nagoya Medical CenterNagoya, Japan; Department of AIDS Research, Nagoya University Graduate School of MedicineNagoya, Japan
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20
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Abstract
The AID/APOBEC family enzymes convert cytosines in single-stranded DNA to uracils, causing base substitutions and strand breaks. They are induced by cytokines produced during the body's inflammatory response to infections, and they help combat infections through diverse mechanisms. AID is essential for the maturation of antibodies and causes mutations and deletions in antibody genes through somatic hypermutation (SHM) and class-switch recombination (CSR) processes. One member of the APOBEC family, APOBEC1, edits mRNA for a protein involved in lipid transport. Members of the APOBEC3 subfamily in humans (APOBEC3A, APOBEC3B, APOBEC3C, APOBEC3D, APOBEC3F, APOBEC3G, and APOBEC3H) inhibit infections of viruses such as HIV-1, HBV, and HCV, and retrotransposition of endogenous retroelements through mutagenic and nonmutagenic mechanisms. There is emerging consensus that these enzymes can cause mutations in the cellular genome at replication forks or within transcription bubbles depending on the physiological state of the cell and the phase of the cell cycle during which they are expressed. We describe here the state of knowledge about the structures of these enzymes, regulation of their expression, and both the advantageous and deleterious consequences of their expression, including carcinogenesis. We highlight similarities among them and present a holistic view of their regulation and function.
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Affiliation(s)
- Sachini U Siriwardena
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
| | - Kang Chen
- Department of Obstetrics and Gynecology, Wayne State University , Detroit, Michigan 48201, United States
- Mucosal Immunology Studies Team, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
- Department of Immunology and Microbiology, Wayne State University School of Medicine , Detroit, Michigan 48201, United States
| | - Ashok S Bhagwat
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
- Department of Immunology and Microbiology, Wayne State University School of Medicine , Detroit, Michigan 48201, United States
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21
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Telesnitsky A, Wolin SL. The Host RNAs in Retroviral Particles. Viruses 2016; 8:v8080235. [PMID: 27548206 PMCID: PMC4997597 DOI: 10.3390/v8080235] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/15/2016] [Accepted: 08/16/2016] [Indexed: 12/15/2022] Open
Abstract
As they assemble, retroviruses encapsidate both their genomic RNAs and several types of host RNA. Whereas limited amounts of messenger RNA (mRNA) are detectable within virion populations, the predominant classes of encapsidated host RNAs do not encode proteins, but instead include endogenous retroelements and several classes of non-coding RNA (ncRNA), some of which are packaged in significant molar excess to the viral genome. Surprisingly, although the most abundant host RNAs in retroviruses are also abundant in cells, unusual forms of these RNAs are packaged preferentially, suggesting that these RNAs are recruited early in their biogenesis: before associating with their cognate protein partners, and/or from transient or rare RNA populations. These RNAs' packaging determinants differ from the viral genome's, and several of the abundantly packaged host ncRNAs serve cells as the scaffolds of ribonucleoprotein particles. Because virion assembly is equally efficient whether or not genomic RNA is available, yet RNA appears critical to the structural integrity of retroviral particles, it seems possible that the selectively encapsidated host ncRNAs might play roles in assembly. Indeed, some host ncRNAs appear to act during replication, as some transfer RNA (tRNA) species may contribute to nuclear import of human immunodeficiency virus 1 (HIV-1) reverse transcription complexes, and other tRNA interactions with the viral Gag protein aid correct trafficking to plasma membrane assembly sites. However, despite high conservation of packaging for certain host RNAs, replication roles for most of these selectively encapsidated RNAs-if any-have remained elusive.
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Affiliation(s)
- Alice Telesnitsky
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Sandra L Wolin
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06536, USA.
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22
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Abstract
A fascinating aspect of retroviruses is their tendency to nonrandomly incorporate host cell RNAs into virions. In addition to the specific tRNAs that prime reverse transcription, all examined retroviruses selectively package multiple host cell noncoding RNAs (ncRNAs). Many of these ncRNAs appear to be encapsidated shortly after synthesis, before assembling with their normal protein partners. Remarkably, although some packaged ncRNAs, such as pre-tRNAs and the spliceosomal U6 small nuclear RNA (snRNA), were believed to reside exclusively within mammalian nuclei, it was demonstrated recently that the model retrovirus murine leukemia virus (MLV) packages these ncRNAs from a novel pathway in which unneeded nascent ncRNAs are exported to the cytoplasm for degradation. The finding that retroviruses package forms of ncRNAs that are rare in cells suggests several hypotheses for how these RNAs could assist retrovirus assembly and infectivity. Moreover, recent experiments in several laboratories have identified additional ways in which cellular ncRNAs may contribute to the retrovirus life cycle. This review focuses on the ncRNAs that are packaged by retroviruses and the ways in which both encapsidated ncRNAs and other cellular ncRNAs may contribute to retrovirus replication.
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23
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Stavrou S, Ross SR. APOBEC3 Proteins in Viral Immunity. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2015; 195:4565-70. [PMID: 26546688 PMCID: PMC4638160 DOI: 10.4049/jimmunol.1501504] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Apolipoprotein B editing complex 3 family members are cytidine deaminases that play important roles in intrinsic responses to infection by retroviruses and have been implicated in the control of other viruses, such as parvoviruses, herpesviruses, papillomaviruses, hepatitis B virus, and retrotransposons. Although their direct effect on modification of viral DNA has been clearly demonstrated, whether they play additional roles in innate and adaptive immunity to viruses is less clear. We review the data regarding the various steps in the innate and adaptive immune response to virus infection in which apolipoprotein B editing complex 3 proteins have been implicated.
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Affiliation(s)
- Spyridon Stavrou
- Department of Microbiology, Abramson Cancer Center, Institute for Immunology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6142
| | - Susan R Ross
- Department of Microbiology, Abramson Cancer Center, Institute for Immunology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6142
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24
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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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25
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Siriwardena SU, Guruge TA, Bhagwat AS. Characterization of the Catalytic Domain of Human APOBEC3B and the Critical Structural Role for a Conserved Methionine. J Mol Biol 2015; 427:3042-55. [PMID: 26281709 DOI: 10.1016/j.jmb.2015.08.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 08/04/2015] [Accepted: 08/06/2015] [Indexed: 12/15/2022]
Abstract
Human APOBEC3B deaminates cytosines in DNA and belongs to the AID/APOBEC family of enzymes. These proteins are involved in innate and adaptive immunity and may cause mutations in a variety of cancers. To characterize its ability to convert cytosines into uracils, we tested several derivatives of APOBEC3B gene for their ability to cause mutations in Escherichia coli. Through this analysis, a methionine residue at the junction of the amino-terminal domain (NTD) and the carboxy-terminal domain (CTD) was found to be essential for high mutagenicity. Properties of mutants with substitutions at this position, examination of existing molecular structures of APOBEC3 family members and molecular modeling suggest that this residue is essential for the structural stability of this family of proteins. The APOBEC3B CTD with the highest mutational activity was purified to homogeneity and its kinetic parameters were determined. Size-exclusion chromatography of the CTD monomer showed that it is in equilibrium with its dimeric form and matrix-assisted laser desorption ionization time-of-flight analysis of the protein suggested that the dimer may be quite stable. The partially purified NTD did not show intrinsic deamination activity and did not enhance the activity of the CTD in biochemical assays. Finally, APOBEC3B was at least 10-fold less efficient at mutating 5-methylcytosine (5mC) to thymine than APOBEC3A in a genetic assay and was at least 10-fold less efficient at deaminating 5mC compared to C in biochemical assays. These results shed light on the structural organization of APOBEC3B catalytic domain, its substrate specificity and its possible role in causing genome-wide mutations.
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Affiliation(s)
| | - Thisari A Guruge
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
| | - Ashok S Bhagwat
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA; Department of Immunology and Microbiology, Wayne State University, Detroit, MI 48202, USA
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26
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Kouno T, Luengas EM, Shigematsu M, Shandilya SMD, Zhang J, Chen L, Hara M, Schiffer CA, Harris RS, Matsuo H. Structure of the Vif-binding domain of the antiviral enzyme APOBEC3G. Nat Struct Mol Biol 2015; 22:485-91. [PMID: 25984970 PMCID: PMC4456288 DOI: 10.1038/nsmb.3033] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 04/21/2015] [Indexed: 12/24/2022]
Abstract
The human APOBEC3G (A3G) DNA cytosine deaminase restricts and hypermutates DNA-based parasites including HIV-1. The viral infectivity factor (Vif) prevents restriction by triggering A3G degradation. While the structure of the A3G catalytic domain is known, the structure of the N-terminal Vif-binding domain has proven more elusive. Here, evolution- and structure-guided mutagenesis was used to solubilize the Vif-binding domain of A3G permitting structural determination by NMR spectroscopy. A smaller zinc-coordinating pocket and altered helical packing distinguish it from catalytic domain structures, and help explain the reported inactivity of this domain. This soluble A3G N-terminal domain is bound by Vif, which enabled mutagenesis and biochemical experiments to identify a unique Vif-interacting surface formed by α1-β1, β2-α2, and β4-α4 loops. This structure sheds new light on the Vif-A3G interaction and provides critical information for future drug development.
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Affiliation(s)
- Takahide Kouno
- 1] Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA. [2] Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Elizabeth M Luengas
- Biochemistry, Molecular Biology and Biophysics Department, Masonic Cancer Center, Center for Genome Engineering, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Megumi Shigematsu
- Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Shivender M D Shandilya
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - JingYing Zhang
- Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Luan Chen
- Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Mayuko Hara
- Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Celia A Schiffer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Reuben S Harris
- Biochemistry, Molecular Biology and Biophysics Department, Masonic Cancer Center, Center for Genome Engineering, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Hiroshi Matsuo
- Biochemistry, Molecular Biology and Biophysics Department, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA
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Heat-stable molecule derived from Streptococcus cristatus induces APOBEC3 expression and inhibits HIV-1 replication. PLoS One 2014; 9:e106078. [PMID: 25165817 PMCID: PMC4148350 DOI: 10.1371/journal.pone.0106078] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 07/31/2014] [Indexed: 11/26/2022] Open
Abstract
Although most human immunodeficiency virus type 1 (HIV-1) cases worldwide are transmitted through mucosal surfaces, transmission through the oral mucosal surface is a rare event. More than 700 bacterial species have been detected in the oral cavity. Despite great efforts to discover oral inhibitors of HIV, little information is available concerning the anti-HIV activity of oral bacterial components. Here we show that a molecule from an oral commensal bacterium, Streptococcus cristatus CC5A can induce expression of APOBEC3G (A3G) and APOBEC3F (A3F) and inhibit HIV-1 replication in THP-1 cells. We show by qRT-PCR that expression levels of A3G and A3F increase in a dose-dependent manner in the presence of a CC5A extract, as does A3G protein levels by Western blot assay. In addition, when the human monocytic cell line THP-1 was treated with CC5A extract, the replication of HIV-1 IIIB was significantly suppressed compared with IIIB replication in untreated THP-1 cells. Knock down of A3G expression in THP-1 cells compromised the ability of CC5A to inhibit HIV-1 IIIB infectivity. Furthermore, SupT1 cells infected with virus produced from CC5A extract-treated THP-1 cells replicated virus with a higher G to A hypermutation rate (a known consequence of A3G activity) than virus used from untreated THP-1 cells. This suggests that S. cristatus CC5A contains a molecule that induces A3G/F expression and thereby inhibits HIV replication. These findings might lead to the discovery of a novel anti-HIV/AIDS therapeutic.
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Feng Y, Baig TT, Love RP, Chelico L. Suppression of APOBEC3-mediated restriction of HIV-1 by Vif. Front Microbiol 2014; 5:450. [PMID: 25206352 PMCID: PMC4144255 DOI: 10.3389/fmicb.2014.00450] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 08/06/2014] [Indexed: 12/21/2022] Open
Abstract
The APOBEC3 restriction factors are a family of deoxycytidine deaminases that are able to suppress replication of viruses with a single-stranded DNA intermediate by inducing mutagenesis and functional inactivation of the virus. Of the seven human APOBEC3 enzymes, only APOBEC3-D, -F, -G, and -H appear relevant to restriction of HIV-1 in CD4+ T cells and will be the focus of this review. The restriction of HIV-1 occurs most potently in the absence of HIV-1 Vif that induces polyubiquitination and degradation of APOBEC3 enzymes through the proteasome pathway. To restrict HIV-1, APOBEC3 enzymes must be encapsidated into budding virions. Upon infection of the target cell during reverse transcription of the HIV-1 RNA into (-)DNA, APOBEC3 enzymes deaminate cytosines to form uracils in single-stranded (-)DNA regions. Upon replication of the (-)DNA to (+)DNA, the HIV-1 reverse transcriptase incorporates adenines opposite to the uracils thereby inducing C/G to T/A mutations that can functionally inactivate HIV-1. APOBEC3G is the most studied APOBEC3 enzyme and it is known that Vif attempts to thwart APOBEC3 function not only by inducing its proteasomal degradation but also by several degradation-independent mechanisms, such as inhibiting APOBEC3G virion encapsidation, mRNA translation, and for those APOBEC3G molecules that still become virion encapsidated, Vif can inhibit APOBEC3G mutagenic activity. Although most Vif variants can induce efficient degradation of APOBEC3-D, -F, and -G, there appears to be differential sensitivity to Vif-mediated degradation for APOBEC3H. This review examines APOBEC3-mediated HIV restriction mechanisms, how Vif acts as a substrate receptor for a Cullin5 ubiquitin ligase complex to induce degradation of APOBEC3s, and the determinants and functional consequences of the APOBEC3 and Vif interaction from a biological and biochemical perspective.
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Affiliation(s)
- Yuqing Feng
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Saskatoon, SK, Canada
| | - Tayyba T Baig
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Saskatoon, SK, Canada
| | - Robin P Love
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Saskatoon, SK, Canada
| | - Linda Chelico
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan Saskatoon, SK, Canada
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Aydin H, Taylor MW, Lee JE. Structure-guided analysis of the human APOBEC3-HIV restrictome. Structure 2014; 22:668-84. [PMID: 24657093 DOI: 10.1016/j.str.2014.02.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/11/2014] [Accepted: 02/20/2014] [Indexed: 01/03/2023]
Abstract
Human APOBEC3 (A3) proteins are host-encoded intrinsic restriction factors that inhibit the replication of many retroviral pathogens. Restriction is believed to occur as a result of the DNA cytosine deaminase activity of the A3 proteins; this activity converts cytosines into uracils in single-stranded DNA retroviral replication intermediates. A3 proteins are also equipped with deamination-independent means to restrict retroviruses that work cooperatively with deamination-dependent restriction pathways. A3 proteins substantially bolster the intrinsic immune system by providing a powerful block to the transmission of retroviral pathogens; however, most retroviruses are able to subvert this replicative restriction in their natural host. HIV-1, for instance, evades A3 proteins through the activity of its accessory protein Vif. Here, we summarize data from recent A3 structural and functional studies to provide perspectives into the interactions between cellular A3 proteins and HIV-1 macromolecules throughout the viral replication cycle.
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Affiliation(s)
- Halil Aydin
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Matthew W Taylor
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Jeffrey E Lee
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada.
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Imahashi M, Izumi T, Watanabe D, Imamura J, Matsuoka K, Ode H, Masaoka T, Sato K, Kaneko N, Ichikawa S, Koyanagi Y, Takaori-Kondo A, Utsumi M, Yokomaku Y, Shirasaka T, Sugiura W, Iwatani Y, Naoe T. Lack of association between intact/deletion polymorphisms of the APOBEC3B gene and HIV-1 risk. PLoS One 2014; 9:e92861. [PMID: 24667791 PMCID: PMC3965477 DOI: 10.1371/journal.pone.0092861] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 02/27/2014] [Indexed: 12/29/2022] Open
Abstract
Objective The human APOBEC3 family of proteins potently restricts HIV-1 replication APOBEC3B, one of the family genes, is frequently deleted in human populations. Two previous studies reached inconsistent conclusions regarding the effects of APOBEC3B loss on HIV-1 acquisition and pathogenesis. Therefore, it was necessary to verify the effects of APOBEC3B on HIV-1 infection in vivo. Methods Intact (I) and deletion (D) polymorphisms of APOBEC3B were analyzed using PCR. The syphilis, HBV and HCV infection rates, as well as CD4+ T cell counts and viral loads were compared among three APOBEC3B genotype groups (I/I, D/I, and D/D). HIV-1 replication kinetics was assayed in vitro using primary cells derived from PBMCs. Results A total of 248 HIV-1-infected Japanese men who have sex with men (MSM) patients and 207 uninfected Japanese MSM were enrolled in this study. The genotype analysis revealed no significant differences between the APOBEC3B genotype ratios of the infected and the uninfected cohorts (p = 0.66). In addition, HIV-1 disease progression parameters were not associated with the APOBEC3B genotype. Furthermore, the PBMCs from D/D and I/I subjects exhibited comparable HIV-1 susceptibility. Conclusion Our analysis of a population-based matched cohort suggests that the antiviral mechanism of APOBEC3B plays only a negligible role in eliminating HIV-1 in vivo.
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Affiliation(s)
- Mayumi Imahashi
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
- Department of Hematology and Oncology, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Taisuke Izumi
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- Japanese Foundation for AIDS Prevention, Chiyoda-ku, Tokyo, Japan
| | - Dai Watanabe
- Clinical Research Center, National Hospital Organization Osaka Medical Center, Osaka Japan
| | - Junji Imamura
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Kazuhiro Matsuoka
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Hirotaka Ode
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Takashi Masaoka
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Kei Sato
- Center for Human Retrovirus Research, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Noriyo Kaneko
- Department of International Health Nursing, Graduate School of Nursing, Nagoya City University, Nagoya, Japan
| | - Seiichi Ichikawa
- Department of International Health Nursing, Graduate School of Nursing, Nagoya City University, Nagoya, Japan
| | - Yoshio Koyanagi
- Center for Human Retrovirus Research, Institute for Virus Research, Kyoto University, Kyoto, Japan
| | - Akifumi Takaori-Kondo
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Makoto Utsumi
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Yoshiyuki Yokomaku
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
| | - Takuma Shirasaka
- Clinical Research Center, National Hospital Organization Osaka Medical Center, Osaka Japan
| | - Wataru Sugiura
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
- Department of AIDS Research, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Yasumasa Iwatani
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
- Department of AIDS Research, Graduate School of Medicine, Nagoya University, Nagoya, Japan
- * E-mail:
| | - Tomoki Naoe
- Department of Infectious Diseases and Immunology, Clinical Research Center, National Hospital Organization Nagoya Medical Center, Nagoya, Japan
- Department of Hematology and Oncology, Graduate School of Medicine, Nagoya University, Nagoya, Japan
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Li J, Chen Y, Li M, Carpenter MA, McDougle RM, Luengas EM, Macdonald PJ, Harris RS, Mueller JD. APOBEC3 multimerization correlates with HIV-1 packaging and restriction activity in living cells. J Mol Biol 2014; 426:1296-307. [PMID: 24361275 PMCID: PMC3977201 DOI: 10.1016/j.jmb.2013.12.014] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 12/10/2013] [Accepted: 12/10/2013] [Indexed: 12/30/2022]
Abstract
APOBEC3G belongs to a family of DNA cytosine deaminases that are involved in the restriction of a broad number of retroviruses including human immunodeficiency virus type 1 (HIV-1). Prior studies have identified two distinct mechanistic steps in Vif-deficient HIV-1 restriction: packaging into virions and deaminating viral cDNA. APOBEC3A, for example, although highly active, is not packaged and is therefore not restrictive. APOBEC3G, on the other hand, although having weaker enzymatic activity, is packaged into virions and is strongly restrictive. Although a number of studies have described the propensity for APOBEC3 oligomerization, its relevance to HIV-1 restriction remains unclear. Here, we address this problem by examining APOBEC3 oligomerization in living cells using molecular brightness analysis. We find that APOBEC3G forms high-order multimers as a function of protein concentration. In contrast, APOBEC3A, APOBEC3C and APOBEC2 are monomers at all tested concentrations. Among other members of the APOBEC3 family, we show that the multimerization propensities of APOBEC3B, APOBEC3D, APOBEC3F and APOBEC3H (haplotype II) bear more resemblance to APOBEC3G than to APOBEC3A/3C/2. Prior studies have shown that all of these multimerizing APOBEC3 proteins, but not the monomeric family members, have the capacity to package into HIV-1 particles and restrict viral infectivity. This correlation between oligomerization and restriction is further evidenced by two different APOBEC3G mutants, which are each compromised for multimerization, packaging and HIV-1 restriction. Overall, our results imply that multimerization of APOBEC3 proteins may be related to the packaging mechanism and ultimately to virus restriction.
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Affiliation(s)
- Jinhui Li
- School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA
| | - Yan Chen
- School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA
| | - Ming Li
- Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Michael A Carpenter
- Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Rebecca M McDougle
- Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Elizabeth M Luengas
- Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Patrick J Macdonald
- Department of Biomedical Engineering, University of Minnesota, 312 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Reuben S Harris
- Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology and Biophysics, 321 Church Street Southeast, Minneapolis, MN 55455, USA
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, 116 Church Street Southeast, Minneapolis, MN 55455, USA; Institute for Molecular Virology, University of Minnesota, 515 Delaware Street Southeast, Minneapolis, MN 55455, USA; Department of Biomedical Engineering, University of Minnesota, 312 Church Street Southeast, Minneapolis, MN 55455, USA.
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CBFβ enhances de novo protein biosynthesis of its binding partners HIV-1 Vif and RUNX1 and potentiates the Vif-induced degradation of APOBEC3G. J Virol 2014; 88:4839-52. [PMID: 24522927 DOI: 10.1128/jvi.03359-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Vif is a lentiviral accessory protein that regulates viral infectivity in part by inducing proteasomal degradation of APOBEC3G (A3G). Recently, CBFβ was found to facilitate Vif-dependent degradation of A3G. However, the exact role of CBFβ remains unclear. Several studies noted reduced Vif expression in CBFβ knockdown cells while others saw no significant impact of CBFβ on Vif stability. Here, we confirmed that CBFβ increases Vif steady-state levels. CBFβ affected expression of neither viral Gag nor Vpu protein, indicating that CBFβ regulates Vif expression posttranscriptionally. Kinetic studies revealed effects of CBFβ on both metabolic stability and the rate of Vif biosynthesis. These effects were dependent on the ability of CBFβ to interact with Vif. Importantly, at comparable Vif levels, CBFβ further enhanced A3G degradation, suggesting that CBFβ facilitates A3G degradation by increasing the levels of Vif and by independently augmenting the ability of Vif to target A3G for degradation. CBFβ also increased expression of RUNX1 by enhancing RUNX1 biosynthesis. Unlike Vif, however, CBFβ had no detectable effect on RUNX1 metabolic stability. We propose that CBFβ acts as a chaperone to stabilize Vif during and after synthesis and to facilitate interaction of Vif with cellular cofactors required for the efficient degradation of A3G. IMPORTANCE In this study, we show that CBFβ has a profound effect on the expression of the HIV-1 infectivity factor Vif and the cellular transcription factor RUNX1, two proteins that physically interact with CBFβ. Kinetic studies revealed that CBFβ increases the rate of Vif and RUNX1 biosynthesis at the level of translation. Mutants of Vif unable to physically interact with CBFβ were nonresponsive to CBFβ. Our data suggest that CBFβ exerts a chaperone-like activity (i) to minimize the production of defective ribosomal products (DRiPs) by binding to nascent protein to prevent premature termination and (ii) to stabilize mature protein conformation to ensure proper function of Vif and RUNX1. Thus, we identified a novel mechanism of protein regulation that affects both viral and cellular factors and thus has broad implications beyond the immediate HIV field.
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Bélanger K, Savoie M, Rosales Gerpe MC, Couture JF, Langlois MA. Binding of RNA by APOBEC3G controls deamination-independent restriction of retroviruses. Nucleic Acids Res 2013; 41:7438-52. [PMID: 23761443 PMCID: PMC3753645 DOI: 10.1093/nar/gkt527] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 05/19/2013] [Accepted: 05/21/2013] [Indexed: 11/19/2022] Open
Abstract
APOBEC3G (A3G) is a host-encoded protein that potently restricts the infectivity of a broad range of retroviruses. This can occur by mechanisms dependent on catalytic activity, resulting in the mutagenic deamination of nascent viral cDNA, and/or by other means that are independent of its catalytic activity. It is not yet known to what extent deamination-independent processes contribute to the overall restriction, how they exactly work or how they are regulated. Here, we show that alanine substitution of either tryptophan 94 (W94A) or 127 (W127A) in the non-catalytic N-terminal domain of A3G severely impedes RNA binding and alleviates deamination-independent restriction while still maintaining DNA mutator activity. Substitution of both tryptophans (W94A/W127A) produces a more severe phenotype in which RNA binding and RNA-dependent protein oligomerization are completely abrogated. We further demonstrate that RNA binding is specifically required for crippling late reverse transcript accumulation, preventing proviral DNA integration and, consequently, restricting viral particle release. We did not find that deaminase activity made a significant contribution to the restriction of any of these processes. In summary, this work reveals that there is a direct correlation between A3G's capacity to bind RNA and its ability to inhibit retroviral infectivity in a deamination-independent manner.
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Affiliation(s)
- Kasandra Bélanger
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Mathieu Savoie
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - María Carla Rosales Gerpe
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Jean-François Couture
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Marc-André Langlois
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5, Emerging Pathogens Research Centre, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5 and Department of Pathology and Laboratory Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
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Vieira VC, Soares MA. The role of cytidine deaminases on innate immune responses against human viral infections. BIOMED RESEARCH INTERNATIONAL 2013; 2013:683095. [PMID: 23865062 PMCID: PMC3707226 DOI: 10.1155/2013/683095] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Revised: 05/29/2013] [Accepted: 05/31/2013] [Indexed: 02/06/2023]
Abstract
The APOBEC family of proteins comprises deaminase enzymes that edit DNA and/or RNA sequences. The APOBEC3 subgroup plays an important role on the innate immune system, acting on host defense against exogenous viruses and endogenous retroelements. The role of APOBEC3 proteins in the inhibition of viral infection was firstly described for HIV-1. However, in the past few years many studies have also shown evidence of APOBEC3 action on other viruses associated with human diseases, including HTLV, HCV, HBV, HPV, HSV-1, and EBV. APOBEC3 inhibits these viruses through a series of editing-dependent and independent mechanisms. Many viruses have evolved mechanisms to counteract APOBEC effects, and strategies that enhance APOBEC3 activity constitute a new approach for antiviral drug development. On the other hand, novel evidence that editing by APOBEC3 constitutes a source for viral genetic diversification and evolution has emerged. Furthermore, a possible role in cancer development has been shown for these host enzymes. Therefore, understanding the role of deaminases on the immune response against infectious agents, as well as their role in human disease, has become pivotal. This review summarizes the state-of-the-art knowledge of the impact of APOBEC enzymes on human viruses of distinct families and harboring disparate replication strategies.
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Affiliation(s)
- Valdimara C. Vieira
- Programa de Oncovirologia, Instituto Nacional de Câncer, Rua André Cavalcanti, No. 37–4 Andar, Bairro de Fátima, 20231-050 Rio de Janeiro, RJ, Brazil
| | - Marcelo A. Soares
- Programa de Oncovirologia, Instituto Nacional de Câncer, Rua André Cavalcanti, No. 37–4 Andar, Bairro de Fátima, 20231-050 Rio de Janeiro, RJ, Brazil
- Departamento de Genética, Universidade Federal do Rio de Janeiro, 21949-570 Rio de Janeiro, RJ, Brazil
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Impact of H216 on the DNA binding and catalytic activities of the HIV restriction factor APOBEC3G. J Virol 2013; 87:7008-14. [PMID: 23596292 DOI: 10.1128/jvi.03173-12] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
APOBEC3G has an important role in human defense against retroviral pathogens, including HIV-1. Its single-stranded DNA cytosine deaminase activity, located in its C-terminal domain (A3Gctd), can mutate viral cDNA and restrict infectivity. We used time-resolved nuclear magnetic resonance (NMR) spectroscopy to determine kinetic parameters of A3Gctd's deamination reactions within a 5'-CCC hot spot sequence. A3Gctd exhibited a 45-fold preference for 5'-CCC substrate over 5'-CCU substrate, which explains why A3G displays almost no processivity within a 5'-CCC motif. In addition, A3Gctd's shortest substrate sequence was found to be a pentanucleotide containing 5'-CCC flanked on both sides by a single nucleotide. A3Gctd as well as full-length A3G showed peak deamination velocities at pH 5.5. We found that H216 is responsible for this pH dependence, suggesting that protonation of H216 could play a key role in substrate binding. Protonation of H216 appeared important for HIV-1 restriction activity as well, since substitutions of H216 resulted in lower restriction in vivo.
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Refsland EW, Harris RS. The APOBEC3 family of retroelement restriction factors. Curr Top Microbiol Immunol 2013; 371:1-27. [PMID: 23686230 DOI: 10.1007/978-3-642-37765-5_1] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The ability to regulate and even target mutagenesis is an extremely valuable cellular asset. Enzyme-catalyzed DNA cytosine deamination is a molecular strategy employed by vertebrates to promote antibody diversity and defend against foreign nucleic acids. Ten years ago, a family of cellular enzymes was first described with several proving capable of deaminating DNA and inhibiting HIV-1 replication. Ensuing studies on the apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3) restriction factors have uncovered a broad-spectrum innate defense network that suppresses the replication of numerous endogenous and exogenous DNA-based parasites. Although many viruses possess equally elaborate counter-defense mechanisms, the APOBEC3 enzymes offer a tantalizing possibility of leveraging innate immunity to fend off viral infection. Here, we focus on mechanisms of retroelement restriction by the APOBEC3 family of restriction enzymes, and we consider the therapeutic benefits, as well as the possible pathological consequences, of arming cells with active DNA deaminases.
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Affiliation(s)
- Eric W Refsland
- Department of Biochemistry, University of Minnesota, Minneapolis, MN 55455, USA
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Siu KK, Sultana A, Azimi FC, Lee JE. Structural determinants of HIV-1 Vif susceptibility and DNA binding in APOBEC3F. Nat Commun 2013; 4:2593. [PMID: 24185281 PMCID: PMC4956467 DOI: 10.1038/ncomms3593] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 09/10/2013] [Indexed: 01/12/2023] Open
Abstract
The human APOBEC3 family of DNA cytosine deaminases serves as a front-line intrinsic immune response to inhibit the replication of diverse retroviruses. APOBEC3F and APOBEC3G are the most potent factors against HIV-1. As a countermeasure, HIV-1 viral infectivity factor (Vif) targets APOBEC3s for proteasomal degradation. Here we report the crystal structure of the Vif-binding domain in APOBEC3F and a novel assay to assess Vif-APOBEC3 binding. Our results point to an amphipathic surface that is conserved in APOBEC3s as critical for Vif susceptibility in APOBEC3F. Electrostatic interactions likely mediate Vif binding. Moreover, structure-guided mutagenesis reveals a straight ssDNA-binding groove distinct from the Vif-binding site, and an 'aromatic switch' is proposed to explain DNA substrate specificities across the APOBEC3 family. This study opens new lines of inquiry that will further our understanding of APOBEC3-mediated retroviral restriction and provides an accurate template for structure-guided development of inhibitors targeting the APOBEC3-Vif axis.
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Affiliation(s)
- Karen K Siu
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Room 6316 Toronto, Ontario, Canada M5S 1A8
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Jaszczur M, Bertram JG, Pham P, Scharff MD, Goodman MF. AID and Apobec3G haphazard deamination and mutational diversity. Cell Mol Life Sci 2012. [PMID: 23178850 DOI: 10.1007/s00018-012-1212-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Activation-induced deoxycytidine deaminase (AID) and Apobec 3G (Apo3G) cause mutational diversity by initiating mutations on regions of single-stranded (ss) DNA. Expressed in B cells, AID deaminates C → U in actively transcribed immunoglobulin (Ig) variable and switch regions to initiate the somatic hypermutation (SHM) and class switch recombination (CSR) that are essential for antibody diversity. Apo3G expressed in T cells catalyzes C deaminations on reverse transcribed cDNA causing HIV-1 retroviral inactivation. When operating properly, AID- and Apo3G-initiated mutations boost human fitness. Yet, both enzymes are potentially powerful somatic cell "mutators". Loss of regulated expression and proper genome targeting can cause human cancer. Here, we review well-established biological roles of AID and Apo3G. We provide a synopsis of AID partnering proteins during SHM and CSR, and describe how an Apo2 crystal structure provides "surrogate" insight for AID and Apo3G biochemical behavior. However, large gaps remain in our understanding of how dC deaminases search ssDNA to identify trinucleotide motifs to deaminate. We discuss two recent methods to analyze ssDNA scanning and deamination. Apo3G scanning and deamination is visualized in real-time using single-molecule FRET, and AID deamination efficiencies are determined with a random walk analysis. AID and Apo3G encounter many candidate deamination sites while scanning ssDNA. Generating mutational diversity is a principal aim of AID and an important ancillary property of Apo3G. Success seems likely to involve hit and miss deamination motif targeting, biased strongly toward miss.
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Affiliation(s)
- Malgorzata Jaszczur
- Departments of Biological Sciences and Chemistry, Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089-2910, USA
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Phalora PK, Sherer NM, Wolinsky SM, Swanson CM, Malim MH. HIV-1 replication and APOBEC3 antiviral activity are not regulated by P bodies. J Virol 2012; 86:11712-24. [PMID: 22915799 PMCID: PMC3486339 DOI: 10.1128/jvi.00595-12] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 08/10/2012] [Indexed: 12/12/2022] Open
Abstract
The APOBEC3 cytidine deaminases play a critical role in host-mediated defense against exogenous viruses, most notably, human immunodeficiency virus type-1 (HIV-1) and endogenous transposable elements. APOBEC3G and APOBEC3F interact with numerous proteins that regulate cellular RNA metabolism, including components of the RNA-induced silencing complex (RISC), and colocalize with a subset of these proteins to mRNA processing bodies (P bodies), which are sites of mRNA translational repression and decay. We sought to determine the role of P bodies and associated proteins in HIV-1 replication and APOBEC3 antiviral activity. While we established a positive correlation between APOBEC3 protein incorporation into virions and localization to P bodies, depletion of the P-body components DDX6 or Lsm1 did not affect HIV-1 replication, APOBEC3 packaging into virions or APOBEC3 protein mediated inhibition of HIV-1 infectivity. In addition, neither HIV-1 genomic RNA nor Gag colocalized with P-body proteins. However, simultaneous depletion of multiple Argonaute family members, the effector proteins of RISC, could modestly increase viral infectivity. Because some APOBEC3 proteins interact with several Argonaute proteins, we also tested whether they could modulate microRNA (miRNA) activity. We found no evidence for the specific regulation of miRNA function by the APOBEC3 proteins, though more general effects on transfected gene expression were observed. In sum, our results indicate that P bodies and certain associated proteins do not regulate HIV-1 replication or APOBEC3 protein antiviral activity. Localization to P bodies may therefore provide a means of sequestering APOBEC3 enzymatic activity away from cellular DNA or may be linked to as yet unidentified cellular functions.
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Affiliation(s)
- Prabhjeet K. Phalora
- Department of Infectious Diseases, Kings College London School of Medicine, Guy's Hospital, London, United Kingdom
| | - Nathan M. Sherer
- Department of Infectious Diseases, Kings College London School of Medicine, Guy's Hospital, London, United Kingdom
| | - Steven M. Wolinsky
- Division of Infectious Diseases, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Chad M. Swanson
- Department of Infectious Diseases, Kings College London School of Medicine, Guy's Hospital, London, United Kingdom
| | - Michael H. Malim
- Department of Infectious Diseases, Kings College London School of Medicine, Guy's Hospital, London, United Kingdom
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Identification of the HIV-1 NC binding interface in Alix Bro1 reveals a role for RNA. J Virol 2012; 86:11608-15. [PMID: 22896625 DOI: 10.1128/jvi.01260-12] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
HIV-1 recruits members of ESCRT, the cell membrane fission machinery that promotes virus exit. HIV-1 Gag protein gains access to ESCRT directly by binding Alix, an ESCRT-associated protein that promotes budding. The Alix Bro1 and V domains bind Gag NC and p6 regions, respectively. Whereas V-p6 binding and function are well characterized, residues in Bro1 that interact with NC and their functional contribution to Alix-mediated HIV-1 budding are unknown. We mapped Bro1 residues that constitute the NC binding interface and found that they are critical for function. Intriguingly, residues involved in interactions on both sides of the Bro1-NC interface are positively charged, suggesting the involvement of a negatively charged cellular factor serving as a bridge. Nuclease treatment eliminated Bro1-NC interactions, revealing the involvement of RNA. These findings establish a direct role for NC in mediating interactions with ESCRT necessary for virus release and report the first evidence of RNA involvement in such recruitments.
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41
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Zhen A, Du J, Zhou X, Xiong Y, Yu XF. Reduced APOBEC3H variant anti-viral activities are associated with altered RNA binding activities. PLoS One 2012; 7:e38771. [PMID: 22859935 PMCID: PMC3408456 DOI: 10.1371/journal.pone.0038771] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 05/13/2012] [Indexed: 01/27/2023] Open
Abstract
APOBEC3H (A3H) is a member of the APOBEC3 family of proteins with varying activities against retroviruses and retrotransposons. The A3H gene contains several single nucleotide polymorphisms and up to seven haplotypes have been detected in humans. Although variations in anti-viral function among A3H haplotypes are not fully understood, only 15N105R-containing A3H variants are known to have potent activities against Vif-deficient HIV-1. Unique motif RLYY(F/Y)W of APOBEC3G (A3G) and APOBEC3F (A3F) required for 7SL RNA binding and HIV-1 incorporation is also conserved in all A3H variants. Like A3G, A3H HapII also demonstrated high binding affinity to host small RNAs such as 7SL and Y RNAs. Mutation of a critical amino acid, W115A resulted in reduced expression level, decreased affinity for 7SL RNA, impairment of virion packaging and reduced anti-viral activity. By comparison, A3H HapI had lower binding affinities to host small RNAs and reduced efficiency of virion incorporation, resulting in significantly reduced anti-viral activity. The SNP ΔN15 commonly found in A3H HapIII and HapIV abolished their abilities to associate with RNAs, and A3H HapIIΔ15N failed to package into HIV-1 virions or exhibited any anti-viral activity. Finally, we showed that A3H variants had distinct cellular localization patterns, which correlated with their different RNA binding affinities. Thus, Pol-III RNA such as 7SL RNA binding is a conserved feature of potent anti-HIV human APOBEC3 cytidine deaminases.
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Affiliation(s)
- Anjie Zhen
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Juan Du
- First Affiliated Hospital, Jilin University, Jilin, China
| | - Xiaohong Zhou
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- First Affiliated Hospital, Jilin University, Jilin, China
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
| | - Xiao-Fang Yu
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- First Affiliated Hospital, Jilin University, Jilin, China
- * E-mail:
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42
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Imahashi M, Nakashima M, Iwatani Y. Antiviral Mechanism and Biochemical Basis of the Human APOBEC3 Family. Front Microbiol 2012; 3:250. [PMID: 22787460 PMCID: PMC3391693 DOI: 10.3389/fmicb.2012.00250] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 06/21/2012] [Indexed: 12/24/2022] Open
Abstract
The human APOBEC3 (A3) family (A, B, C, DE, F, G, and H) comprises host defense factors that potently inhibit the replication of diverse retroviruses, retrotransposons, and the other viral pathogens. HIV-1 has a counterstrategy that includes expressing the Vif protein to abrogate A3 antiviral function. Without Vif, A3 proteins, particularly APOBEC3G (A3G) and APOBEC3F (A3F), inhibit HIV-1 replication by blocking reverse transcription and/or integration and hypermutating nascent viral cDNA. The molecular mechanisms of this antiviral activity have been primarily attributed to two biochemical characteristics common to A3 proteins: catalyzing cytidine deamination in single-stranded DNA (ssDNA) and a nucleic acid-binding capability that is specific to ssDNA or ssRNA. Recent advances suggest that unique property of A3G dimer/oligomer formations, is also important for the modification of antiviral activity. In this review article we summarize how A3 proteins, particularly A3G, inhibit viral replication based on the biochemical and structural characteristics of the A3G protein.
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Affiliation(s)
- Mayumi Imahashi
- Clinical Research Center, National Hospital Organization Nagoya Medical Center Nagoya, Japan
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43
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Batisse J, Guerrero S, Bernacchi S, Sleiman D, Gabus C, Darlix JL, Marquet R, Tisné C, Paillart JC. The role of Vif oligomerization and RNA chaperone activity in HIV-1 replication. Virus Res 2012; 169:361-76. [PMID: 22728817 DOI: 10.1016/j.virusres.2012.06.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 06/04/2012] [Accepted: 06/12/2012] [Indexed: 11/28/2022]
Abstract
The viral infectivity factor (Vif) is essential for the productive infection and dissemination of HIV-1 in non-permissive cells that involve most natural HIV-1 target cells. Vif counteracts the packaging of two cellular cytidine deaminases named APOBEC3G (A3G) and A3F by diverse mechanisms including the recruitment of an E3 ubiquitin ligase complex and the proteasomal degradation of A3G/A3F, the inhibition of A3G mRNA translation or by a direct competition mechanism. In addition, Vif appears to be an active partner of the late steps of viral replication by participating in virus assembly and Gag processing, thus regulating the final stage of virion formation notably genomic RNA dimerization and by inhibiting the initiation of reverse transcription. Vif is a small pleiotropic protein with multiple domains, and recent studies highlighted the importance of Vif conformation and flexibility in counteracting A3G and in binding RNA. In this review, we will focus on the oligomerization and RNA chaperone properties of Vif and show that the intrinsic disordered nature of some Vif domains could play an important role in virus assembly and replication. Experimental evidence demonstrating the RNA chaperone activity of Vif will be presented.
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Affiliation(s)
- Julien Batisse
- Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg, France
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44
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Characterization of the interaction of full-length HIV-1 Vif protein with its key regulator CBFβ and CRL5 E3 ubiquitin ligase components. PLoS One 2012; 7:e33495. [PMID: 22479405 PMCID: PMC3316577 DOI: 10.1371/journal.pone.0033495] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 02/14/2012] [Indexed: 01/07/2023] Open
Abstract
Human immunodeficiency virus-1 (HIV-1) viral infectivity factor (Vif) is essential for viral replication because of its ability to eliminate the host's antiviral response to HIV-1 that is mediated by the APOBEC3 family of cellular cytidine deaminases. Vif targets these proteins, including APOBEC3G, for polyubiquitination and subsequent proteasome-mediated degradation via the formation of a Cullin5-ElonginB/C-based E3 ubiquitin ligase. Determining how the cellular components of this E3 ligase complex interact with Vif is critical to the intelligent design of new antiviral drugs. However, structural studies of Vif, both alone and in complex with cellular partners, have been hampered by an inability to express soluble full-length Vif protein. Here we demonstrate that a newly identified host regulator of Vif, core-binding factor-beta (CBFβ), interacts directly with Vif, including various isoforms and a truncated form of this regulator. In addition, carboxyl-terminal truncations of Vif lacking the BC-box and cullin box motifs were sufficient for CBFβ interaction. Furthermore, association of Vif with CBFβ, alone or in combination with Elongin B/C (EloB/C), greatly increased the solubility of full-length Vif. Finally, a stable complex containing Vif-CBFβ-EloB/C was purified in large quantity and shown to bind purified Cullin5 (Cul5). This efficient strategy for purifying Vif-Cul5-CBFβ-EloB/C complexes will facilitate future structural and biochemical studies of Vif function and may provide the basis for useful screening approaches for identifying novel anti-HIV drug candidates.
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45
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Techtmann SM, Ghirlando R, Kao S, Strebel K, Maynard EL. Hydrodynamic and functional analysis of HIV-1 Vif oligomerization. Biochemistry 2012; 51:2078-86. [PMID: 22369580 DOI: 10.1021/bi201738a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
HIV-1 Vif is an accessory protein that induces the proteasomal degradation of the host restriction factor, apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G). The N-terminal half of Vif binds to APOBEC3G, and the C-terminal half binds to subunits of a cullin 5-based ubiquitin ligase. This Vif-directed ubiquitin ligase induces the degradation of APOBEC3G (a cytidine deaminase) and thereby protects the viral genome from mutation. A conserved PPLP motif near the C-terminus of Vif is essential for Vif function and is also involved in Vif oligomerization. However, the mechanism and functional significance of Vif oligomerization is unclear. We employed analytical ultracentrifugation to examine the oligomeric properties of Vif in solution. Contrary to previous reports, we find that Vif oligomerization does not require the conserved PPLP motif. Instead, our data suggest a more complex mechanism involving interactions among the HCCH motif, the BC box, and downstream residues in Vif. Mutation of residues near the PPLP motif (S165 and V166) affected the oligomeric properties of Vif and weakened the ability of Vif to bind and induce the degradation of APOBEC3G. We propose that Vif oligomerization may represent a mechanism for regulating interactions with APOBEC3G.
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Affiliation(s)
- Stephen M Techtmann
- Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, United States
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46
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Fehrholz M, Kendl S, Prifert C, Weissbrich B, Lemon K, Rennick L, Duprex PW, Rima BK, Koning FA, Holmes RK, Malim MH, Schneider-Schaulies J. The innate antiviral factor APOBEC3G targets replication of measles, mumps and respiratory syncytial viruses. J Gen Virol 2011; 93:565-576. [PMID: 22170635 DOI: 10.1099/vir.0.038919-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The cytidine deaminase APOBEC3G (apolipoprotein B mRNA-editing enzyme-catalytic polypeptide 3G; A3G) exerts antiviral activity against retroviruses, hepatitis B virus, adeno-associated virus and transposable elements. We assessed whether the negative-strand RNA viruses measles, mumps and respiratory syncytial might be affected by A3G, and found that their infectivity was reduced by 1-2 logs (90-99 %) in A3G overexpressing Vero cells, and in T-cell lines expressing A3G at physiological levels. Viral RNA was co-precipitated with HA-tagged A3G and could be amplified by RT-PCR. Interestingly, A3G reduced viral transcription and protein expression in infected cells by 50-70 %, and caused an increased mutation frequency of 0.95 mutations per 1000 nt in comparison to the background level of 0.22/1000. The observed mutations were not specific for A3G [cytidine to uridine (C→U) or guanine to adenine (G→A) hypermutations], nor specific for ADAR (adenosine deaminase acting on RNA, A→G and U→C transitions, with preference for next neighbour-nucleotides U = A>C>G). In addition, A3G mutants with inactivated catalytic deaminase (H257R and E259Q) were inhibitory, indicating that the deaminase activity is not required for the observed antiviral activity. In combination, impaired transcription and increased mutation frequencies are sufficient to cause the observed reduction in viral infectivity and eliminate virus replication within a few passages in A3G-expressing cells.
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Affiliation(s)
- Markus Fehrholz
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Sabine Kendl
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Christiane Prifert
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Benedikt Weissbrich
- Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany
| | - Ken Lemon
- Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, UK
| | - Linda Rennick
- Department of Microbiology, Boston University School of Medicine and National Emerging Infectious Diseases Laboratories, Boston University, Boston, USA
| | - Paul W Duprex
- Department of Microbiology, Boston University School of Medicine and National Emerging Infectious Diseases Laboratories, Boston University, Boston, USA
| | - Bert K Rima
- Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, UK
| | | | | | - Michael H Malim
- Department of Infectious Diseases, King's College, London, UK
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Abudu A, Wang X, Dang Y, Zhou T, Xiang SH, Zheng YH. Identification of molecular determinants from Moloney leukemia virus 10 homolog (MOV10) protein for virion packaging and anti-HIV-1 activity. J Biol Chem 2011; 287:1220-8. [PMID: 22105071 DOI: 10.1074/jbc.m111.309831] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Discovery of novel antiretroviral mechanism is essential for the design of innovative antiretroviral therapy. Recently, we and others reported that ectopic expression of Moloney leukemia virus 10 (MOV10) protein strongly inhibits retrovirus replication. MOV10, a putative RNA helicase, can be packaged into HIV-1 virions by binding to the nucleocapsid (NC) region of Gag and inhibit viral replication at a postentry step. Here, we report critical determinants for MOV10 virion packaging and antiviral activity. MOV10 has 1,003 amino acids and seven helicase motifs. We found that MOV10 packaging requires the NC basic linker, and Gag binds to the N-terminal amino acids 261-305 region of MOV10. Our predicted MOV10 three-dimensional structure model indicates that the Gag binding region is located in a structurally exposed domain, which spans amino acids 93-305 and is Cys-His-rich. Simultaneous mutation of residues Cys-188, Cys-195, His-199, His-201, and His-202 in this domain significantly compromised MOV10 anti-HIV-1 activity. Notably, although MOV10-Gag interaction is required, it is not sufficient for MOV10 packaging, which also requires its C-terminal all but one of seven helicase motifs. Moreover, we have mapped the minimal MOV10 antiviral region to amino acids 99-949, indicating that nearly all MOV10 residues are required for its antiviral activity. Mutations of residues Cys-947, Pro-948, and Phe-949 at the C terminus of this region completely disrupted MOV10 anti-HIV-1 activity. Taken together, we have identified two critical MOV10 packaging determinants and eight other critical residues for anti-HIV-1 activity. These results provide a molecular basis for further understanding the MOV10 antiretroviral mechanism.
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Affiliation(s)
- Aierken Abudu
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824-4320, USA
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48
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Abstract
APOBEC3G (A3G) is packaged into human immunodeficiency virus type 1 (HIV-1) virions unless HIV-1 virion infectivity factor (Vif) counteracts it. Virion A3G restricts HIV-1 reverse transcription and integration in target cells. Some A3G in producer cells colocalizes with specific cytoplasmic structures, in what are called "A3G complexes" here. Functional effects of producer cell A3G complexes on HIV-1 replication were studied. HeLa cells were cotransfected with HIV-1 constructs producing pseudoviruses, as well as either wild-type (WT) A3G or a mutant A3G (C97A, Y124A, W127A, or D128K A3G). Pseudovirus particle production was decreased from cells expressing any of the A3Gs that formed complexes by 24 h after transfection, relative to cells with C97A A3G that did not form detectable A3G complexes by 24 h or A3G-negative cells. The intracellular HIV-1 Gag half-life was shorter in cells containing A3G complexes than in those lacking complexes. HIV-1 virion output was decreased in a single round of replication from a T cell line containing A3G complexes (CEM cells) after infection with Vif-negative HIV-1, compared to Vif-positive HIV-1 that depleted A3G. Levels of production of Vif-negative and Vif-positive virus were similar from cells not containing A3G (CEM-SS cells). Knockdown of the mRNA processing body (P-body) component RCK/p54, eliminated A3G complex formation, and increased HIV-1 production. We conclude that endogenous A3G complexes in producer cells decrease HIV-1 production if not degraded by Vif.
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49
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McDougall WM, Okany C, Smith HC. Deaminase activity on single-stranded DNA (ssDNA) occurs in vitro when APOBEC3G cytidine deaminase forms homotetramers and higher-order complexes. J Biol Chem 2011; 286:30655-30661. [PMID: 21737457 DOI: 10.1074/jbc.m111.269506] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
APOBEC3G (A3G) is a cytidine deaminase that catalyzes deamination of deoxycytidine (dC) on single-stranded DNA (ssDNA). The oligomeric state of A3G required to support deaminase activity remains unknown. We show under defined in vitro conditions that full-length and native A3G formed complexes with ssDNA in an A3G concentration-dependent but temperature-independent manner. Complexes assembled and maintained at 4 °C did not have significant deaminase activity, but their enzymatic function could be restored by subsequent incubation at 37 °C. This approach enabled complexes of a defined size range to be isolated and subsequently evaluated for their contribution to enzymatic activity. The composition of A3G bound to ssDNA was determined by protein-protein chemical cross-linking. A3G-ssDNA complexes of 16 S were necessary for deaminase activity and consisted of cross-linked A3G homotetramers and homodimers. At lower concentrations, A3G only formed 5.8 S homodimers on ssDNA with low deaminase activity. Monomeric A3G was not identified in 5.8 S or 16 S complexes. We propose that deaminase-dependent antiviral activity of A3G in vivo may require a critical concentration of A3G in viral particles that will promote oligomerization on ssDNA during reverse transcription.
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Affiliation(s)
- William M McDougall
- Department of Biochemistry and Biophysics, Rochester, New York 14642; Center for RNA Biology, Rochester, New York 14642
| | - Chinelo Okany
- Department of Biochemistry and Biophysics, Rochester, New York 14642
| | - Harold C Smith
- Department of Biochemistry and Biophysics, Rochester, New York 14642; Center for RNA Biology, Rochester, New York 14642; Cancer Center, School of Medicine and Dentistry, the University of Rochester Medical Center, Rochester, New York 14642.
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50
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The role of amino-terminal sequences in cellular localization and antiviral activity of APOBEC3B. J Virol 2011; 85:8538-47. [PMID: 21715505 DOI: 10.1128/jvi.02645-10] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human APOBEC3B (A3B) has been described as a potent inhibitor of retroviral infection and retrotransposition. However, we found that the predominantly nuclear A3B only weakly restricted infection by HIV-1, HIV-1Δvif, and human T-cell leukemia virus type 1 (HTLV-1), while significantly inhibiting LINE-1 retrotransposition. The chimeric construct A3G/B, in which the first 60 amino acids of A3B were replaced with those of A3G, restricted HIV-1, HIV-1Δvif, and HTLV-1 infection, as well as LINE-1 retrotransposition. In contrast to the exclusively cytoplasmic A3G, which is inactive against LINE-1 retrotransposition, the A3G/B protein, while localized mainly to the cytoplasm, was also present in the nucleus. Further mutational analysis revealed that residues 18, 19, 22, and 24 in A3B were the major determinants for nuclear versus cytoplasmic localization and antiretroviral activity. HIV-1Δvif packages A3G, A3B, and A3G/B into particles with close-to-equal efficiencies. Mutation E68Q or E255Q in the active centers of A3G/B resulted in loss of the inhibitory activity against HIV-1Δvif, while not affecting activity against LINE-1 retrotransposition. The low inhibition of HIV-1Δvif by A3B correlated with a low rate of G-to-A hypermutation. In contrast, viruses that had been exposed to A3G/B showed a high number of G-to-A transitions. The mutation pattern was similar to that previously reported for A3B, with a preference for the GA context. In summary, these observations suggest that changing 4 residues in the amino terminus of A3B not only retargets the protein from the nucleus to the cytoplasm but also enhances its ability to restrict HIV while retaining inhibition of retrotransposition.
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