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Troyer RM, Malmberg JL, Zheng X, Miller C, MacMillan M, Sprague WS, Wood BA, VandeWoude S. Expression of APOBEC3 Lentiviral Restriction Factors in Cats. Viruses 2019; 11:v11090831. [PMID: 31500260 PMCID: PMC6783916 DOI: 10.3390/v11090831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/05/2019] [Accepted: 09/05/2019] [Indexed: 12/31/2022] Open
Abstract
Feline immunodeficiency virus (FIV) is a naturally occurring T-cell tropic lentiviral disease of felids with many similarities to HIV/AIDS in humans. Similar to primate lentiviral-host interactions, feline APOBEC3 (A3) has been shown to inhibit FIV infection in a host-specific manner and feline A3 degradation is mediated by FIV Vif. Further, infection of felids with non-native FIV strains results in restricted viral replication in both experimental and naturally occurring infections. However, the link between molecular A3-Vif interactions and A3 biological activity during FIV infection has not been well characterized. We thus examined expression of the feline A3 genes A3Z2, A3Z3 and A3Z2-Z3 during experimental infection of domestic cats with host-adapted domestic cat FIV (referred to as FIV) and non-adapted Puma concolor FIV (referred to as puma lentivirus, PLV). We determined A3 expression in different tissues and blood cells from uninfected, FIV-infected, PLV-infected and FIV/PLV co-infected cats; and in purified blood cell subpopulations from FIV-infected and uninfected cats. Additionally, we evaluated regulation of A3 expression by cytokines, mitogens, and FIV infection in cultured cells. In all feline cells and tissues studied, there was a striking difference in expression between the A3 genes which encode FIV inhibitors, with A3Z3 mRNA abundance exceeding that of A3Z2-Z3 by 300-fold or more. Interferon-alpha treatment of cat T cells resulted in upregulation of A3 expression, while treatment with interferon-gamma enhanced expression in cat cell lines. In cats, secondary lymphoid organs and peripheral blood mononuclear cells (PBMC) had the highest basal A3 expression levels and A3 genes were differentially expressed among blood T cells, B cells, and monocytes. Acute FIV and PLV infection of cats, and FIV infection of primary PBMC resulted in no detectable change in A3 expression with the exception of significantly elevated A3 expression in the thymus, the site of highest FIV replication. We conclude that cat A3 expression is regulated by cytokine treatment but, by and large, lentiviral infection did not appear to alter expression. Differences in A3 expression in different blood cell subsets did not appear to impact FIV viral replication kinetics within these cells. Furthermore, the relative abundance of A3Z3 mRNA compared to A3Z2-Z3 suggests that A3Z3 may be the major active anti-lentiviral APOBEC3 gene product in domestic cats.
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Affiliation(s)
- Ryan M Troyer
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
- Department of Microbiology and Immunology, University of Western Ontario, 1151 Richmond St., London, ON N6A 5C1, Canada.
| | - Jennifer L Malmberg
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
- Wyoming State Veterinary Laboratory, University of Wyoming, 1174 Snowy Range Rd., Laramie, WY 82072, USA.
| | - Xin Zheng
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
| | - Craig Miller
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078, USA.
| | - Martha MacMillan
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
| | - Wendy S Sprague
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
- Sprague Medical and Scientific Communications, LLC, Fort Collins, CO 80528, USA.
| | - Britta A Wood
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
- The Pirbright Institute, Pirbright, Surrey GU24 0NF, UK.
| | - Sue VandeWoude
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
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Yang Z, Tao Y, Xu X, Cai F, Yu Y, Ma L. Bufalin inhibits cell proliferation and migration of hepatocellular carcinoma cells via APOBEC3F induced intestinal immune network for IgA production signaling pathway. Biochem Biophys Res Commun 2018; 503:2124-2131. [PMID: 30100060 DOI: 10.1016/j.bbrc.2018.07.169] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 07/31/2018] [Indexed: 02/08/2023]
Abstract
OBJECTIVE This study aimed to evaluate functions of APOBEC3F gene in biological process of hepatocellular carcinoma (HCC) and anti-tumor mechanisms of bufalin. METHODS Effect of APOBEC3F and bufalin on cell proliferation and migration abilities were evaluated by CCK-8, wounding healing tests and transwell assays in SK-Hep1 and Bel-7404 cells. Bioinformatic analysis were also used to compare APOBEC3F expression levels, detect coexpressed genes and enrichment of pathways. RESULTS APOBEC3F was overexpressed in tumor tissues compared to adjacent tissues in HCC patients. And, APOBEC3F promotes cell proliferation and migration in SK-Hep1 and Bel-7404 cells. Bufalin inhibits cell proliferation and migration and reduces APOBEC3F expression. GO and KEGG enrichment of APOBEC3F-coexpressed genes revealed that APOBEC3F might active intestinal immune network for IgA production signaling pathway, leading to malignant biological behaviors of HCC cells. Additionally, siAPOBEC3F could decrease pIgR, CCR9, CCR10 and CXCR4 protein levels. And, bufalin inhibits the pIgR, CCR9, CCR10 and CXCR4 protein expressions. CONCLUSIONS Bufalin inhibits cell proliferation and migration of HCC cells via APOBEC3F induced intestinal immune network for IgA production signaling pathway.
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Affiliation(s)
- Zongguo Yang
- Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China; Department of Integrative Medicine, Shanghai Public Health Clinical Center, Fudan University, Shanghai, 201508, PR China
| | - Yuquan Tao
- Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China
| | - Xin Xu
- Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China
| | - Feng Cai
- Department of Clinical Laboratory Medicine, Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China
| | - Yongchun Yu
- Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China; Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, 200030, PR China.
| | - Lifang Ma
- Department of Clinical Laboratory Medicine, Shanghai Municipal Hospital of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, 200071, PR China.
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Koh S, Kah J, Tham CYL, Yang N, Ceccarello E, Chia A, Chen M, Khakpoor A, Pavesi A, Tan AT, Dandri M, Bertoletti A. Nonlytic Lymphocytes Engineered to Express Virus-Specific T-Cell Receptors Limit HBV Infection by Activating APOBEC3. Gastroenterology 2018; 155:180-193.e6. [PMID: 29550589 DOI: 10.1053/j.gastro.2018.03.027] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 02/26/2018] [Accepted: 03/08/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS Strategies to develop virus-specific T cells against hepatic viral infections have been hindered by safety concerns. We engineered nonlytic human T cells to suppress replication of hepatitis B virus (HBV) and hepatitis C virus (HCV) without overt hepatotoxicity and investigated their antiviral activity. METHODS We electroporated resting T cells or T cells activated by anti-CD3 with mRNAs encoding HBV or HCV-specific T-cell receptors (TCRs) to create 2 populations of TCR-reprogrammed T cells. We tested their ability to suppress HBV or HCV replication without lysis in 2-dimensional and 3-dimensional cultures of HepG2.2.15 cells and HBV-infected HepG2-hNTCP cells. We also injected TCR-reprogrammed resting and activated T cells into HBV-infected urokinase-type plasminogen activator/severe combined immunodeficiency disease/interleukin 2γ mice with humanized livers and measured levels of intrahepatic and serological viral parameters and serum alanine aminotransferase. Livers were collected for analysis of gene expression patterns to determine effects of the TCR-reprogrammed T cells. RESULTS TCR-reprogrammed resting T cells produced comparable levels of interferon gamma but lower levels of perforin and granzyme than activated T cells and did not lyse HCV- or HBV-infected hepatoma cells. Although T-cell secretion of interferon gamma was required to inhibit HCV replication, the HBV-specific TCR-reprogrammed resting T cells reduced HBV replication also through intracellular activation of apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3 (APOBEC3). The mechanism of APOBEC3 intracellular activation involved temporal expression of lymphotoxin-β receptor ligands on resting T cells after TCR-mediated antigen recognition and activation of lymphotoxin-β receptor in infected cells. CONCLUSIONS We developed TCR-reprogrammed nonlytic T cells capable of activating APOBEC3 in hepatoma cells and in HBV-infected human hepatocytes in mice, limiting viral infection. These cells with limited hepatotoxicity might be developed for treatment of chronic HBV infection.
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Affiliation(s)
- Sarene Koh
- Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A*STAR), Singapore; Lion TCR Private Limited Singapore, Singapore.
| | - Janine Kah
- Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christine Y L Tham
- Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A*STAR), Singapore; NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore
| | - Ninghan Yang
- Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Erica Ceccarello
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Adeline Chia
- Emerging Infectious Diseases (EID) Program, Duke-NUS Medical School, Singapore
| | - Margaret Chen
- Department of Dental Medicine, Karolinska Institutet, Sweden
| | - Atefeh Khakpoor
- Emerging Infectious Diseases (EID) Program, Duke-NUS Medical School, Singapore
| | - Andrea Pavesi
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Anthony T Tan
- Emerging Infectious Diseases (EID) Program, Duke-NUS Medical School, Singapore
| | - Maura Dandri
- Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; German Center for Infection Research, Hamburg-Lübeck-Borstel Partner Site, Germany
| | - Antonio Bertoletti
- Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research (A*STAR), Singapore; Emerging Infectious Diseases (EID) Program, Duke-NUS Medical School, Singapore.
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Bennett RP, Salter JD, Smith HC. A New Class of Antiretroviral Enabling Innate Immunity by Protecting APOBEC3 from HIV Vif-Dependent Degradation. Trends Mol Med 2018; 24:507-520. [PMID: 29609878 PMCID: PMC7362305 DOI: 10.1016/j.molmed.2018.03.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 03/05/2018] [Accepted: 03/08/2018] [Indexed: 12/11/2022]
Abstract
The infectivity of HIV depends on overcoming APOBEC3 (A3) innate immunity, predominantly through the expression of the viral protein Vif, which induces A3 degradation in the proteasome. Disruption of the functional interactions of Vif enables A3 mutagenesis of the HIV genome during viral replication, which can result in a broadly neutralizing antiviral effect. Vif function requires self-association along with interactions with A3 proteins, protein chaperones, and factors of the ubiquitination machinery and these are described here as a potential platform for novel antiviral drug discovery. This Review will examine the current state of development of Vif inhibitors that we believe to have therapeutic and functional cure potential.
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Affiliation(s)
- Ryan P Bennett
- OyaGen, Inc., 77 Ridgeland Road, Rochester, NY 14623, USA.
| | - Jason D Salter
- OyaGen, Inc., 77 Ridgeland Road, Rochester, NY 14623, USA
| | - Harold C Smith
- OyaGen, Inc., 77 Ridgeland Road, Rochester, NY 14623, USA; University of Rochester, School of Medicine and Dentistry, Department of Biochemistry and Biophysics, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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Abstract
A majority of human papillomavirus (HPV) infections are asymptomatic and self-resolving in the absence of medical interventions. Various innate and adaptive immune responses, as well as physical barriers, have been implicated in controlling early HPV infections. However, if HPV overcomes these host immune defenses and establishes persistence in basal keratinocytes, it becomes very difficult for the host to eliminate the infection. The HPV oncoproteins E5, E6, and E7 are important in regulating host immune responses. These oncoproteins dysregulate gene expression, protein-protein interactions, posttranslational modifications, and cellular trafficking of critical host immune modulators. In addition to the HPV oncoproteins, sequence variation and dinucleotide depletion in papillomavirus genomes has been suggested as an alternative strategy for evasion of host immune defenses. Since anti-HPV host immune responses are also considered to be important for antitumor immunity, immune dysregulation by HPV during virus persistence may contribute to immune suppression essential for HPV-associated cancer progression. Here, we discuss cellular pathways dysregulated by HPV that allow the virus to evade various host immune defenses.
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Affiliation(s)
- Joseph A Westrich
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Cody J Warren
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Current address: BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80303, USA
| | - Dohun Pyeon
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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Knisbacher BA, Gerber D, Levanon EY. DNA Editing by APOBECs: A Genomic Preserver and Transformer. Trends Genet 2016; 32:16-28. [PMID: 26608778 DOI: 10.1016/j.tig.2015.10.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 10/18/2015] [Accepted: 10/22/2015] [Indexed: 10/22/2022]
Abstract
Information warfare is not limited to the cyber world because it is waged within our cells as well. The unique AID (activation-induced cytidine deaminase)/APOBEC (apolipoprotein B mRNA editing enzyme, catalytic polypeptide) family comprises proteins that alter DNA sequences by converting deoxycytidines to deoxyuridines through deamination. This C-to-U DNA editing enables them to inhibit parasitic viruses and retrotransposons by disrupting their genomic content. In addition to attacking genomic invaders, APOBECs can target their host genome, which can be beneficial by initiating processes that create antibody diversity needed for the immune system or by accelerating the rate of evolution. AID can also alter gene regulation by removing epigenetic modifications from genomic DNA. However, when uncontrolled, these powerful agents of change can threaten genome stability and eventually lead to cancer.
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Affiliation(s)
- Binyamin A Knisbacher
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel
| | - Doron Gerber
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel
| | - Erez Y Levanon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel.
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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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Beck-Engeser GB, Winkelmann R, Wheeler ML, Shansab M, Yu P, Wünsche S, Walchhütter A, Metzner M, Vettermann C, Eilat D, DeFranco A, Jäck HM, Wabl M. APOBEC3 enzymes restrict marginal zone B cells. Eur J Immunol 2015; 45:695-704. [PMID: 25501566 PMCID: PMC4972502 DOI: 10.1002/eji.201445218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 10/31/2014] [Accepted: 12/09/2014] [Indexed: 12/16/2022]
Abstract
In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of the enzyme Apobec3 (abbreviated A3). This is counterintuitive because A3 directly controls viremia before the onset of adaptive antiviral immune responses. It suggests that A3 also affects the antibody response directly. Here, we studied the relative size of cell populations of the adaptive immune system as a function of A3 activity. We created a transgenic mouse that expresses all seven human A3 enzymes and compared it to WT and mouse A3-deficient mice. A3 enzymes decreased the number of marginal zone B cells, but not the number of follicular B or T cells. When mouse A3 was knocked out, the retroelement hitchhiker-1 and sialyl transferases encoded by genes close to it were overexpressed three and two orders of magnitude, respectively. We suggest that A3 shifts the balance, from the fast antibody response mediated by marginal zone B cells with little affinity maturation, to a more sustained germinal center B-cell response, which drives affinity maturation and, thereby, a better neutralizing response.
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Affiliation(s)
| | - Rebecca Winkelmann
- Division of Molecular Immunology, Department of Internal Medicine III, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Matthew L. Wheeler
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
| | - Maryam Shansab
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
| | - Philipp Yu
- Institut für Immunologie, Philipps-Universität Marburg, Marburg, Germany
| | - Sarah Wünsche
- Institut für Immunologie, Philipps-Universität Marburg, Marburg, Germany
| | - Anja Walchhütter
- Institut für Immunologie, Philipps-Universität Marburg, Marburg, Germany
| | - Mirjam Metzner
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
- Division of Molecular Immunology, Department of Internal Medicine III, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Christian Vettermann
- Division of Molecular Immunology, Department of Internal Medicine III, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Dan Eilat
- Department of Medicine, Hadassah University Hospital and The Hebrew University Faculty of Medicine, Jerusalem, Israel
| | - Anthony DeFranco
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
| | - Hans-Martin Jäck
- Division of Molecular Immunology, Department of Internal Medicine III, Nikolaus-Fiebiger-Center, University of Erlangen-Nürnberg, Erlangen, Germany
| | - Matthias Wabl
- Department of Microbiology and Immunology, University of California, San Francisco, CA, USA
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Baig TT, Feng Y, Chelico L. Determinants of efficient degradation of APOBEC3 restriction factors by HIV-1 Vif. J Virol 2014; 88:14380-95. [PMID: 25275135 PMCID: PMC4249154 DOI: 10.1128/jvi.02484-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 09/29/2014] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED The APOBEC3 deoxycytidine deaminases can restrict the replication of HIV-1 in cell culture to differing degrees. The effects of APOBEC3 enzymes are largely suppressed by HIV-1 Vif that interacts with host proteins to form a Cullin5-Ring E3 ubiquitin ligase that induces (48)K-linked polyubiquitination (poly-Ub) and proteasomal degradation of APOBEC3 enzymes. Vif variants have differing abilities to induce degradation of APOBEC3 enzymes and the underlying biochemical mechanisms for these differences is not fully understood. We hypothesized that by characterizing the interaction of multiple APOBEC3 enzymes and Vif variants we could identify common features that resulted in Vif-mediated degradation and further define the determinants required for efficient Vif-mediated degradation of APOBEC3 enzymes. We used Vifs from HIV-1 NL4-3 (IIIB) and HXB2 to characterize their induced degradation of and interaction with APOBEC3G, APOBEC3G D128K, APOBEC3H, and APOBEC3B in 293T cells. We quantified the APOBEC3G-Vif and APOBEC3H-Vif interaction strengths in vitro using rotational anisotropy. Our biochemical and cellular analyses of the interactions support a model in which the degradation efficiency of VifIIIB and VifHXB2 correlated with both the binding strength of the APOBEC3-Vif interaction and the APOBEC3-Vif interface, which differs for APOBEC3G and APOBEC3H. Notably, Vif bound to APOBEC3H and APOBEC3B in the natural absence of Vif-induced degradation and the interaction resulted in (63)K-linked poly-Ub of APOBEC3H and APOBEC3B, demonstrating additional functionality of the APOBEC3-Vif interaction apart from induction of proteasomal degradation. IMPORTANCE APOBEC3 enzymes can potently restrict the replication of HIV-1 in the absence of HIV-1 Vif. Vif suppresses APOBEC3 action by inducing their degradation through a direct interaction with APOBEC3 enzymes and other host proteins. Vif variants from different HIV-1 strains have different effects on APOBEC3 enzymes. We used differing Vif degradation capacities of two Vif variants and various APOBEC3 enzymes with differential sensitivities to Vif to delineate determinants of the APOBEC3-Vif interaction that are required for inducing efficient degradation. Using a combined biochemical and cellular approach we identified that the strength of the APOBEC3-Vif binding interaction and the APOBEC3-Vif interface are determinants for degradation efficiency. Our results highlight the importance of using Vif variants with different degradation potential when delineating mechanisms of Vif-induced APOBEC3 degradation and identify features important for consideration in the development of HIV-1 therapies that disrupt the APOBEC3-Vif interaction.
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Affiliation(s)
- Tayyba T Baig
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Yuqing Feng
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Linda Chelico
- Department of Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Ara A, Love RP, Chelico L. Different mutagenic potential of HIV-1 restriction factors APOBEC3G and APOBEC3F is determined by distinct single-stranded DNA scanning mechanisms. PLoS Pathog 2014; 10:e1004024. [PMID: 24651717 PMCID: PMC3961392 DOI: 10.1371/journal.ppat.1004024] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 02/09/2014] [Indexed: 01/12/2023] Open
Abstract
The APOBEC3 deoxycytidine deaminase family functions as host restriction factors that can block replication of Vif (virus infectivity factor) deficient HIV-1 virions to differing degrees by deaminating cytosines to uracils in single-stranded (-)HIV-1 DNA. Upon replication of the (-)DNA to (+)DNA, the HIV-1 reverse transcriptase incorporates adenines opposite the uracils, thereby inducing C/G→T/A mutations that can functionally inactivate HIV-1. Although both APOBEC3F and APOBEC3G are expressed in cell types HIV-1 infects and are suppressed by Vif, there has been no prior biochemical analysis of APOBEC3F, in contrast to APOBEC3G. Using synthetic DNA substrates, we characterized APOBEC3F and found that similar to APOBEC3G; it is a processive enzyme and can deaminate at least two cytosines in a single enzyme-substrate encounter. However, APOBEC3F scanning movement is distinct from APOBEC3G, and relies on jumping rather than both jumping and sliding. APOBEC3F jumping movements were also different from APOBEC3G. The lack of sliding movement from APOBEC3F is due to an ¹⁹⁰NPM¹⁹² motif, since insertion of this motif into APOBEC3G decreases its sliding movements. The APOBEC3G NPM mutant induced significantly less mutations in comparison to wild-type APOBEC3G in an in vitro model HIV-1 replication assay and single-cycle infectivity assay, indicating that differences in DNA scanning were relevant to restriction of HIV-1. Conversely, mutation of the APOBEC3F ¹⁹¹Pro to ¹⁹¹Gly enables APOBEC3F sliding movements to occur. Although APOBEC3F ¹⁹⁰NGM¹⁹² could slide, the enzyme did not induce more mutagenesis than wild-type APOBEC3F, demonstrating that the unique jumping mechanism of APOBEC3F abrogates the influence of sliding on mutagenesis. Overall, we demonstrate key differences in the impact of APOBEC3F- and APOBEC3G-induced mutagenesis on HIV-1 that supports a model in which both the processive DNA scanning mechanism and preferred deamination motif (APOBEC3F, 5'TTC; APOBEC3G 5'CCC) influences the mutagenic and gene inactivation potential of an APOBEC3 enzyme.
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Affiliation(s)
- Anjuman Ara
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Robin P. Love
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Linda Chelico
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail:
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Desimmie BA, Delviks-Frankenberrry KA, Burdick RC, Qi D, Izumi T, Pathak VK. Multiple APOBEC3 restriction factors for HIV-1 and one Vif to rule them all. J Mol Biol 2014; 426:1220-45. [PMID: 24189052 PMCID: PMC3943811 DOI: 10.1016/j.jmb.2013.10.033] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 10/25/2013] [Accepted: 10/28/2013] [Indexed: 12/11/2022]
Abstract
Several members of the APOBEC3 family of cellular restriction factors provide intrinsic immunity to the host against viral infection. Specifically, APOBEC3DE, APOBEC3F, APOBEC3G, and APOBEC3H haplotypes II, V, and VII provide protection against HIV-1Δvif through hypermutation of the viral genome, inhibition of reverse transcription, and inhibition of viral DNA integration into the host genome. HIV-1 counteracts APOBEC3 proteins by encoding the viral protein Vif, which contains distinct domains that specifically interact with these APOBEC3 proteins to ensure their proteasomal degradation, allowing virus replication to proceed. Here, we review our current understanding of APOBEC3 structure, editing and non-editing mechanisms of APOBEC3-mediated restriction, Vif-APOBEC3 interactions that trigger APOBEC3 degradation, and the contribution of APOBEC3 proteins to restriction and control of HIV-1 replication in infected patients.
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Affiliation(s)
- Belete A Desimmie
- Viral Mutation Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | | | - Ryan C Burdick
- Viral Mutation Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - DongFei Qi
- Viral Mutation Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Taisuke Izumi
- Viral Mutation Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Vinay K Pathak
- Viral Mutation Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA.
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Fourati S, Lambert-Niclot S, Soulie C, Wirden M, Malet I, Valantin MA, Tubiana R, Simon A, Katlama C, Carcelain G, Calvez V, Marcelin AG. Differential impact of APOBEC3-driven mutagenesis on HIV evolution in diverse anatomical compartments. AIDS 2014; 28:487-91. [PMID: 24401644 DOI: 10.1097/qad.0000000000000182] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE Previous studies on HIV quasispecies have revealed HIV compartmentalization in various tissues within an infected individual. Such HIV variation is a result of a combination of factors including high replication and mutation rates, recombination, and APOBEC3-host selective pressure. METHODS To evaluate the differential impact of APOBEC3 editing in HIV-1 compartments, we analyzed the level of G-to-A hypermutation in HIV-1 protease and reverse transcriptase sequences among 30 HAART-treated patients for whom peripheral blood mononuclear cells and body tissues or fluids [cerebral spinal fluid (CSF), rectal tissue, or renal tissue] were collected on the same day. RESULTS APOBEC3-mediated hypermutation was identified in 36% (11/30) of participants in at least one viral reservoir. HIV hypermutated sequences were often observed in viral sanctuaries (total n = 10; CSF, n = 6; renal tissue, n = 1; rectal tissue n = 3) compared with peripheral blood (total n = 4). Accordingly, APOBEC3 editing generated more G-to-A drug resistance mutations in sanctuaries: three patients' CSF (i.e. G73S in protease; M184I, M230I in reverse transcriptase) and two other patients' rectal tissues (M184I, M230I in reverse transcriptase) while such mutations were absent from paired peripheral blood mononuclear cells. CONCLUSION APOBEC3-induced mutations observed in peripheral blood underestimate the overall proportion of hypermutated viruses in anatomical compartments. The resulting mutations may favor escape to antiretrovirals in these compartments in conjunction with a lower penetration of drugs in some sanctuaries. On the other side, because hypermutated sequences often harbor inactivating mutations, our results suggest that accumulation of defective viruses may be more dominant in sanctuaries than in peripheral blood of patients on effective HAART.
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Affiliation(s)
- Slim Fourati
- aInserm UMR S-943 bVirology Department cInfectious Disease Department dInternal Medicine Department, Pitie-Salpetriere Hospital eUniversité Pierre and Marie Curie fInserm UMR S945 gAP-HP hImmunology Department, Pitie-Salpetriere Hospital, Paris, France
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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: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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15
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Fourati S, Malet I, Lambert S, Soulie C, Wirden M, Flandre P, Fofana DB, Sayon S, Simon A, Katlama C, Calvez V, Marcelin AG. E138K and M184I mutations in HIV-1 reverse transcriptase coemerge as a result of APOBEC3 editing in the absence of drug exposure. AIDS 2012; 26:1619-24. [PMID: 22695298 DOI: 10.1097/qad.0b013e3283560703] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
BACKGROUND Recent clinical trials with rilpivirine combined with emtricitabine and tenofovir revealed that patients failing treatment, frequently, harbored viruses encoding resistance-associated mutations in the HIV-1 reverse transcriptase at position E138K and M184I. We show here that APOBEC3 proteins play a role in the emergence of these drug resistance mutations. METHODS We used a Vif mutant that has suboptimal activity against APOBEC3 to assess the in-vitro frequency of APOBEC3-induced resistance mutations in reverse transcriptase. To assess the degree of in-vivo G-to-A viral hypermutation, a large amount of data of HIV-1 RT proviral sequences from peripheral blood mononuclear cells (PBMCs) recovered from infected patients under HAART was analyzed. RESULTS In-vitro replication experiments in cell lines with and without APOBEC3 expression suggest that APOBEC3-driven mutagenesis contributes to the generation of both M184I and E138K within HIV proviral repository in the absence of drug exposure. Additionally, analysis of 601 patients PBMCs sequences revealed that the copresence of mutations E138K and M184I were never detected in nonhypermutated sequences, whereas these mutations were found at a high frequency (24%) in the context of APOBEC3 editing and in the absence of exposure to etravirine-rilpivirine. CONCLUSION We demonstrate using in-vitro experiments and analyzing patients PBMCs sequences that M184I and E138K resistance-associated mutations may pre-exist in proviral reservoir at a high frequency prior to drug exposure, as a result of APOBEC3 editing. Thus, incomplete neutralization of one or more APOBEC3 proteins may favor viral escape to rilpivirine-emtricitabine.
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Affiliation(s)
- Slim Fourati
- Université Pierre et Marie Curie-Paris, Groupe Hospitalier Pitié Salpêtrière, Laboratoire de Virologie, Paris, France.
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Monajemi M, Woodworth CF, Benkaroun J, Grant M, Larijani M. Emerging complexities of APOBEC3G action on immunity and viral fitness during HIV infection and treatment. Retrovirology 2012; 9:35. [PMID: 22546055 PMCID: PMC3416701 DOI: 10.1186/1742-4690-9-35] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 04/30/2012] [Indexed: 12/31/2022] Open
Abstract
The enzyme APOBEC3G (A3G) mutates the human immunodeficiency virus (HIV) genome by converting deoxycytidine (dC) to deoxyuridine (dU) on minus strand viral DNA during reverse transcription. A3G restricts viral propagation by degrading or incapacitating the coding ability of the HIV genome. Thus, this enzyme has been perceived as an innate immune barrier to viral replication whilst adaptive immunity responses escalate to effective levels. The discovery of A3G less than a decade ago led to the promise of new anti-viral therapies based on manipulation of its cellular expression and/or activity. The rationale for therapeutic approaches has been solidified by demonstration of the effectiveness of A3G in diminishing viral replication in cell culture systems of HIV infection, reports of its mutational footprint in virions from patients, and recognition of its unusually robust enzymatic potential in biochemical studies in vitro. Despite its effectiveness in various experimental systems, numerous recent studies have shown that the ability of A3G to combat HIV in the physiological setting is severely limited. In fact, it has become apparent that its mutational activity may actually enhance viral fitness by accelerating HIV evolution towards the evasion of both anti-viral drugs and the immune system. This body of work suggests that the role of A3G in HIV infection is more complex than heretofore appreciated and supports the hypothesis that HIV has evolved to exploit the action of this host factor. Here we present an overview of recent data that bring to light historical overestimation of A3G's standing as a strictly anti-viral agent. We discuss the limitations of experimental systems used to assess its activities as well as caveats in data interpretation.
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Affiliation(s)
- Mahdis Monajemi
- Immunology and Infectious Diseases Program, Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, Newfoundland, Canada
| | - Claire F Woodworth
- Mani Larijani, Division of Biomedical Sciences, Faculty of Medicine, Health Sciences Center, MUN, 300 Prince Phillip Dr., St. John’s, NL, A1B 3V6, Canada
| | - Jessica Benkaroun
- Mani Larijani, Division of Biomedical Sciences, Faculty of Medicine, Health Sciences Center, MUN, 300 Prince Phillip Dr., St. John’s, NL, A1B 3V6, Canada
| | - Michael Grant
- Division of Biomedical Sciences, Faculty of Medicine, Health Sciences Center, MUN, 300 Prince Phillip Dr., St. John’s, NL, A1B 3V6, Canada
| | - Mani Larijani
- Division of Biomedical Sciences, Faculty of Medicine, Health Sciences Center, MUN, 300 Prince Phillip Dr., St. John’s, NL, A1B 3V6, Canada
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17
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Ebrahimi D, Anwar F, Davenport MP. APOBEC3 has not left an evolutionary footprint on the HIV-1 genome. J Virol 2011; 85:9139-46. [PMID: 21697498 PMCID: PMC3165787 DOI: 10.1128/jvi.00658-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 06/05/2011] [Indexed: 12/21/2022] Open
Abstract
It is known that the human immune proteins APOBEC3G and -F (hA3G/F) can inhibit Vif-deficient HIV by G-to-A mutation; however, the roles of these enzymes in the evolution of HIV are debated. We argue that if evolutionary pressure from hA3G/F exists there should be evidence of their imprint on the HIV genome in the form of (i) underrepresentation of hA3G/F target motifs (e.g., TGGG [targeted position is underlined]) and overrepresentation of product motifs (e.g., TAGG) and/or (ii) an increase in the ratio of nonsynonymous to synonymous (NS/S) G-to-A changes among hA3G/F target motifs and a decrease of NS/S A-to-G changes among hA3G/F product motifs. To test the first hypothesis, we studied the representation of hA3G/F target and product motifs in 1,932 complete HIV-1 genomes using Markov models. We found that the highly targeted motifs are not underrepresented and their product motifs are not overrepresented. To test the second hypothesis, we determined the NS/S G↔A changes among the hA3G/F target and product motifs in 1,540 complete sets of nine HIV-1 genes. The NS/S changes did not show an increasing/decreasing trend within the target/product motifs, but the NS/S changes within the motif AG was exceptionally low. We observed the same pattern by analyzing 740 human genes. Given that hA3G/F do not act on the human genome, this suggests a small NS/S change within AG has arisen by other mechanisms. We therefore find no evidence of an evolutionary footprint of hA3G/F. We postulate several mechanisms to explain why the HIV-1 genome does not contain the hA3G/F footprint.
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Affiliation(s)
- Diako Ebrahimi
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Firoz Anwar
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Miles P. Davenport
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
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Abstract
PURPOSE OF REVIEW Our understanding of the early events in HIV-1 infection continues to grow, along with the heightened recognition of the important contribution that innate immunity plays in response to HIV-1. Here, we review the epidemiological and functional studies of genetic polymorphisms associated with innate immune factors that are believed to modulate host responses, focusing specifically on recent findings related to Toll-like receptor, cytokine, host restriction and KIR genes and their activities. RECENT FINDINGS A growing number of genomic studies have described polymorphisms in innate immune genes that are associated with early postseroconversion events, including TLR4, TLR9, IRF-3, TRIM5α and the ABOBEC3 gene family. Genetic and functional data confirm the importance of KIR-HLA interactions and provide new understanding of the role of innate restriction factors in resistance to HIV-1 and disease progression. SUMMARY Single-gene, genome-wide association and expression studies have permitted the identification of innate immune genes and their variants that contribute to protection from disease progression. Characterization of the pathogen-innate immune system interactions and discovery of new and rare host genetic variants that account for a portion of the observed variance in the HIV-1 phenotype is critical to gain new insights into promising treatment and prevention strategies.
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Affiliation(s)
- Magdalena E Sobieszczyk
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
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19
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Abstract
PURPOSE OF REVIEW To present evidence of the role of innate mucosal immunity and to harness this arm of immunity in protection against HIV infection. RECENT FINDINGS Dendritic cells, monocytes, natural killer (NK) cells and γδ T cells are critical in innate immunity, which is mediated by Toll-like receptor (TLR) and recently identified stress pathways. Complement factors, cytokines and chemokines have diverse functions usually affecting HIV infection indirectly. A novel group of innate intracellular HIV restriction factors has been identified - APOBEC3G, TRIM5α and tetherin - all of which are upregulated by type I interferons and some by vaccination and TLR agonists. Whereas innate immunity conventionally lacks memory, recent evidence suggests that some of the cells and intracellular factors may express immunological memory-like features. SUMMARY Innate mucosal immunity may provide early effective control of HIV transmission and replication. Some vaccines can enhance innate immune factors, such as APOBEC3G and control HIV during the eclipse period, allowing full weight of neutralizing and/or cytotoxic T cells to develop and prevent mucosal HIV infection. The next generation of vaccines should be designed to target both innate and adaptive immune memory responses.
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Affiliation(s)
- Yufei Wang
- Mucosal Immunology Unit at Guy's Hospital, King's College London, London, UK
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20
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Knoepfel SA, Di Giallonardo F, Däumer M, Thielen A, Metzner KJ. In-depth analysis of G-to-A hypermutation rate in HIV-1 env DNA induced by endogenous APOBEC3 proteins using massively parallel sequencing. J Virol Methods 2011; 171:329-38. [PMID: 21111003 DOI: 10.1016/j.jviromet.2010.11.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 11/08/2010] [Accepted: 11/17/2010] [Indexed: 11/24/2022]
Abstract
Some APOBEC3 proteins cause G-to-A hypermutation in HIV-1 DNA when the accessory viral protein Vif is absent or non-functional. So far, cloning and sequencing has been performed to study G-to-A hypermutation. This is time-consuming and labour-intensive especially in the context of in vivo investigations where the number of hypermutated sequences can be very low. Thus, a massively parallel sequencing protocol has been developed for in-depth analysis of G-to-A hypermutation using the 454 pyrosequencing FLX system. Part of HIV-1 env was amplified and pyrosequenced after two rounds of infection in T cell lines and PBMCs using HIV-1 NL4-3Δvif. Specific criteria were applied to cope with major technical challenges: (1) the inclusion of hypermutated sequences, (2) the high genome diversity of HIV-1 env, and (3) the exclusion of sequences containing frameshift errors caused by pyrosequencing. In total, more than 140,000 sequences were obtained. 1.3-6.5% of guanines were mutated to adenine, most frequently in the GG dinucleotide context, the preferred deamination site of APOBEC3G. Non-G-to-A mutations occurred only in low frequencies (<0.6%). Single hypermutated sequences contained up to 24 G-to-A mutations. Overall, massively parallel sequencing is a very useful tool for in-depth analysis of G-to-A hypermutation in HIV-1 DNA induced by APOBEC3 proteins.
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Affiliation(s)
- Stefanie A Knoepfel
- Institute of Clinical and Molecular Virology, University of Erlangen-Nuremberg, Germany.
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21
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Tsuge M, Noguchi C, Akiyama R, Matsushita M, Kunihiro K, Tanaka S, Abe H, Mitsui F, Kitamura S, Hatakeyama T, Kimura T, Miki D, Hiraga N, Imamura M, Takahashi S, Hayses CN, Chayama K. G to A hypermutation of TT virus. Virus Res 2010; 149:211-6. [PMID: 20138932 DOI: 10.1016/j.virusres.2010.01.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Revised: 01/29/2010] [Accepted: 01/29/2010] [Indexed: 11/26/2022]
Abstract
APOBEC3 proteins function as part of innate antiviral immunity and induce G to A hypermutation in retroviruses and hepatitis B virus (HBV) genomes. Whether APOBEC3 proteins affect viruses that replicate without a reverse transcription step is unknown. TT virus (TTV), known to present in serum of healthy individuals and HBV carriers, has a single-stranded circular DNA genome and replicates without reverse transcription. In this study, we examined 67 blood samples obtained from healthy individuals and HBV carriers and observed G to A hypermutation of genomes of TTV in both healthy individuals and HBV carriers. During ALT flare-up in HBV carriers, G to A hypermutation of HBV increased, but TTV genomes significantly decreased in number and hypermutated TTV genomes became undetectable. Our results show that hypermutated TTV exist in healthy individuals and HBV carriers and that TTV genomes were susceptible to immune reaction directed to HBV by interacting with APOBEC3 proteins.
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Affiliation(s)
- Masataka Tsuge
- Department of Medicine and Molecular Science, Division of Frontier Medical Science, Programs for Biomedical Research, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan
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22
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Abstract
Recent discoveries have revealed previously unappreciated complexity with which retroviruses interact with their hosts. In particular, we have become aware that many mammals, including humans, are equipped with genes encoding so-called "restriction factors," that provide considerable resistance to retroviral infection. Such antiretroviral genes are sometimes constitutively expressed, and sometimes interferon-induced. Thus they can be viewed as comprising an intrinsic immune system that provides a pre-mobilized defense against retroviral infection or, alternatively, as a specialized extension of conventional innate immunity. Antiretroviral restriction factors have evolved at an unusually rapid pace, particularly in primates, and some startling examples of evolutionary change are present in genes encoding restriction factors. Our understanding of the mechanisms by which restriction factors interfere with retroviral replication, and how their effects are avoided by certain retroviruses, is accruing, but far from complete. Such knowledge could allow for novel forms of therapeutic intervention in pathogenic retroviral infections, as well as the development of animal models of human disease.
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Affiliation(s)
- Stuart Neil
- Department of Infectious Disease, King's College London School of Medicine, Guy's Hospital, London, United Kingdom
| | - Paul Bieniasz
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center, The Rockefeller University, New York, New York
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23
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Abstract
BACKGROUND CD4+ T lymphocytes are the primary targets of HIV1 but cannot be infected when fully quiescent, due to a post-entry block preventing the completion of reverse transcription. Chiu et al. recently proposed that this restriction reflects the action of APOBEC3G (A3G). They further suggested that T cell activation abrogates the A3G-mediated block by directing this protein to a high molecular mass complex. METHODOLOGY/PRINCIPAL FINDINGS In the present work, we sought to explore further this model. However, we found that effective suppression of A3G by combined RNA interference and expression of HIV1 Vif does not relieve the restrictive phenotype of post-activation resting T cells. We also failed to find a correlation between HIV resistance and the presence of A3G in a low molecular complex in primary T cells. CONCLUSIONS/SIGNIFICANCE We conclude that A3G is unlikely to play a role in the HIV restrictive phenotype of quiescent T lymphocytes.
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Affiliation(s)
- Francesca R. Santoni de Sio
- Global Health Institute, School of Life Sciences, “Frontiers in Genetics” National Center of Competence in Research, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Didier Trono
- Global Health Institute, School of Life Sciences, “Frontiers in Genetics” National Center of Competence in Research, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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Affiliation(s)
- Susan R Ross
- Department of Microbiology and Abramson Family Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
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25
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Abstract
The ability of members of the APOBEC3 (A3) family of proteins to confer intrinsic immunity to retroviral infection was recognized in several studies. More specifically, A3 proteins are cytidine deaminases (CDAs) that cause hypermutations of nascent retroviral genomes by deamination of cytidine residues. Although A3 proteins can restrict the replication of HIV, this inhibition is overcome by the viral infectivity factor (Vif). Inhibitory effects of APOBEC proteins are not limited to HIV but extend to other viruses and endogenous mobile genetic elements that share a reverse transcription process analogous to that of exogenous retroviruses. In sharp contrast, another conundrum of A3 proteins is that they inhibit viral replication even in the absence of CDA activity and recent advances have defined the inhibition of reverse transcriptase (RT) catalyzed DNA elongation reactions by A3 proteins. Together, these proteins provide strong and immediate intracellular immunity against incoming pathogens and restrict the movement of mobile genetic elements protecting the genome.
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Affiliation(s)
- Renato S Aguiar
- Department of Medicine, Microbiology and Immunology, University of California, San Francisco (UCSF), 533 Parnassus Avenue U422, San Francisco, CA 94143-0703, USA
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26
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Abstract
Xenotransplantation of porcine cells, tissues, and organs offers a solution to overcome the shortage of human donor materials. In addition to the immunological and physiological barriers, the existence of numerous porcine microorganisms including viruses poses a risk for xenozoonosis. Three classes of functional gamma-type porcine endogenous retroviruses (PERV) have been identified, whereby functional polytropic PERV-A and PERV-B infect human embryonic kidney (HEK 293) and other cell lines in vitro. In the course of risk assessment for xenotransplantation the capacity of human cells to counteract PERV infections should be analyzed. Primates and other mammals display different means of protection against viral infections. APOBEC3 proteins which are cytidine deaminases and a part of the intrinsic immunity mediate potent activity against a wide range of retroviruses including murine leukemia viruses (MLV). As PERV and MLV belong to the same genus, we raised the question as to whether PERV is affected by APOBEC3 proteins. Initial data indicate that human and porcine cytidine deaminases inhibit PERV replication, thereby possibly reducing the risk for infection of human cells by PERV as a consequence of pig-to-human xenotransplantation.
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27
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Abstract
Apobec proteins are a family of cellular cytidine deaminases, among which several members have been shown to have potent antiviral properties. This antiviral activity is associated with the ability to cause hypermutation of retroviral cDNA. However, recent research has indicated that Apobec proteins are also able to inhibit retroviruses by other mechanisms that are independent of their deaminase activity. We have compared the antiviral activities of human and murine Apobec3 (A3) proteins, and we have found that, consistent with previous reports, human immunodeficiency virus (HIV) is able to resist human A3G but is sensitive to murine A3, whereas murine leukemia virus (MLV) is relatively resistant to murine A3 (mA3) but sensitive to human A3G. In contrast to previous studies, we observed that mA3 is packaged efficiently into MLV particles. The C-terminal cytidine deaminase domain (CDD2) is required for packaging of mA3 into MLV particles, and packaging did not depend on the MLV viral RNA. However, mA3 packed into MLV particles failed to cause hypermutation of viral DNA, indicating that its deaminase activity is blocked or inhibited. hA3G also caused significantly less hypermutation of MLV than of HIV DNA. Both mA3 and the splice variant mA3Delta5 exhibited some residual antiviral activity against MLV and caused a reduction in the ability of MLV particles to generate reverse transcription products. These results suggest that MLV has evolved specific mechanisms to block the ability of Apobec proteins to mediate deaminase-dependent hypermutation.
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Affiliation(s)
- Edward P Browne
- The Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, 540 First Ave., Second Floor, New York, NY 10016, USA
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28
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Abstract
Human T-cell leukemia virus type I (HTLV-I) is the first human retrovirus and causes adult T-cell leukemia/lymphoma (ATL). Constitutive activation of nuclear factor-kappa B (NF-kappa B) in the leukemic cells is essential for their growth and survival. Thus, NF-kappa B inhibitors have been attracting attention as a potential strategy to treat ATL. Recently, the field of retrovirus research has been stimulated by the discovery of an innate host defense factor, APOBEC3, against the retroviruses. HTLV-I is relatively resistant to the antiviral effects of APOBEC3. To clarify the resistance of HTLV-I against APOBEC3 might contribute to the design of effective therapeutic approaches.
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Affiliation(s)
- Takeo Ohsugi
- Division of Microbiology and Genetics, Center for Animal Resources and Development, Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan.
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Coelho V, Dernedde J, Petrausch U, Panjideh H, Fuchs H, Menzel C, Dübel S, Keilholz U, Thiel E, Deckert PM. Design, construction, and in vitro analysis of A33scFv::CDy, a recombinant fusion protein for antibody-directed enzyme prodrug therapy in colon cancer. Int J Oncol 2007; 31:951-7. [PMID: 17786329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023] Open
Abstract
Antibody-directed enzyme-prodrug therapy (ADEPT) aims at improving the specificity of conventional chemotherapy by employing artificial antibody-enzyme constructs to convert a non-toxic prodrug into a cytotoxic agent specifically localized to the tumor site. The gpA33 antigen is a promising target for ADEPT in colon cancer, as it is expressed by >95% of human colon cancers, but is absent in all non-gastrointestinal tissues. We designed a recombinant fusion construct of a phage display-generated anti-gpA33 single chain fragment, A33scFv, with cytosine deaminase from yeast (CDy), which converts 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU). The resulting construct, A33scFv::CDy, was overexpressed in Pichia pastoris and secreted into culture supernatant. The fusion protein was purified by affinity chromatography on protein L. Silver-staining after SDS-polyacrylamide gel electrophoresis confirmed molecular mass and purity. Antibody binding and specificity were quantified by flow cytometry. The complete ADEPT system was applied in vitro on gpA33-positive LIM1215 cells, assessing cell survival by a fluorescein diacetate assay. Cytotoxicity of the prodrug 5-FC after A33scFv::CDy binding was equimolar to that of 5-FU, and this effect depended specifically on both antibody and enzyme function. These results demonstrate bifunctional activity of the heterogeneous Pichia-produced A33scFv::CDy fusion protein and proof of principle for the ADEPT system proposed herein.
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Affiliation(s)
- Vânia Coelho
- CharitéCentrum für Tumormedizin, Medizinische Klinik mit Schwerpunkt Hämatologie und Onkologie CBF, 12200 Berlin, Germany
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30
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Sakuma R, Mael AA, Ikeda Y. Alpha interferon enhances TRIM5alpha-mediated antiviral activities in human and rhesus monkey cells. J Virol 2007; 81:10201-6. [PMID: 17609277 PMCID: PMC2045407 DOI: 10.1128/jvi.00419-07] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 06/25/2007] [Indexed: 02/07/2023] Open
Abstract
Dominant, constitutively expressed antiretroviral factors, including TRIM5alpha and APOBEC3 proteins, are distinguished from the conventional innate immune systems and are classified as intrinsic immunity factors. Here, we demonstrate that interferon alpha (IFN-alpha) treatment upregulates TRIM5alpha mRNA in rhesus monkey cells, which correlates with the enhanced TRIM5alpha-mediated pre- and postintegration blocks of human immunodeficiency virus replication. In human cells, IFN-alpha increases the levels of TRIM5alpha mRNA, resulting in enhanced antiviral activity against N-tropic murine leukemia virus infection. These observations indicate that the TRIM5alpha-mediated antiviral effects can be orchestrated by the conventional innate immune response. It is conceivable that TRIM5alpha plays an essential role in controlling both the initial retroviral exposure and the subsequent viral dissemination in vivo.
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Affiliation(s)
- Ryuta Sakuma
- Molecular Medicine Program, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
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31
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Abstract
The HIV-1 viral infectivity factor (Vif) is a small basic protein essential for viral fitness and pathogenicity. Some "non-permissive" cell lines cannot sustain replication of Vif(-) HIV-1 virions. In these cells, Vif counteracts the natural antiretroviral activity of the DNA-editing enzymes APOBEC3G/3F. Moreover, Vif is packaged into viral particles through a strong interaction with genomic RNA in viral nucleoprotein complexes. To gain insights into determinants of this binding process, we performed the first characterization of Vif/nucleic acid interactions using Vif intrinsic fluorescence. We determined the affinity of Vif for RNA fragments corresponding to various regions of the HIV-1 genome. Our results demonstrated preferential and moderately cooperative binding for RNAs corresponding to the 5'-untranslated region of HIV-1 (5'-untranslated region) and gag (cooperativity parameter omega approximately 65-80, and K(d) = 45-55 nM). In addition, fluorescence spectroscopy allowed us to point out the TAR apical loop and a short region in gag as primary strong affinity binding sites (K(d) = 9.5-14 nM). Interestingly, beside its RNA binding properties, the Vif protein can also bind the corresponding DNA oligonucleotides and their complementary counterparts with an affinity similar to the one observed for the RNA sequences, while other DNA sequences displayed reduced affinity. Taken together, our results suggest that Vif binding to RNA and DNA offers several non-exclusive ways to counteract APOBEC3G/3F factors, in addition to the well documented Vif-induced degradation by the proteasome and to the Vif-mediated repression of translation of these antiviral factors.
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MESH Headings
- 5' Untranslated Regions/genetics
- 5' Untranslated Regions/immunology
- 5' Untranslated Regions/metabolism
- APOBEC-3G Deaminase
- Binding Sites/physiology
- Cytidine Deaminase
- Cytosine Deaminase/immunology
- Cytosine Deaminase/metabolism
- DNA, Viral/genetics
- DNA, Viral/immunology
- DNA, Viral/metabolism
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/immunology
- DNA-Binding Proteins/metabolism
- Gene Products, gag/genetics
- Gene Products, gag/immunology
- Gene Products, gag/metabolism
- Gene Products, vif/genetics
- Gene Products, vif/immunology
- Gene Products, vif/metabolism
- Genome, Viral/physiology
- HIV Long Terminal Repeat/physiology
- HIV-1/genetics
- HIV-1/immunology
- HIV-1/metabolism
- HIV-1/pathogenicity
- Humans
- Immunity, Innate/physiology
- Nucleoside Deaminases/immunology
- Nucleoside Deaminases/metabolism
- Oligonucleotides/genetics
- Oligonucleotides/immunology
- Oligonucleotides/metabolism
- Protein Binding/physiology
- Protein Biosynthesis/physiology
- RNA, Viral/genetics
- RNA, Viral/immunology
- RNA, Viral/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/immunology
- RNA-Binding Proteins/metabolism
- Repressor Proteins/genetics
- Repressor Proteins/immunology
- Repressor Proteins/metabolism
- vif Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Serena Bernacchi
- Architecture et Réactivité de l'ARN, Université Louis Pasteur de Strasbourg, CNRS, IBMC, 15 Rue René Descartes, 67084 Strasbourg, France
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32
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Peng G, Greenwell-Wild T, Nares S, Jin W, Lei KJ, Rangel ZG, Munson PJ, Wahl SM. Myeloid differentiation and susceptibility to HIV-1 are linked to APOBEC3 expression. Blood 2007; 110:393-400. [PMID: 17371941 PMCID: PMC1896122 DOI: 10.1182/blood-2006-10-051763] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Accepted: 02/16/2007] [Indexed: 01/06/2023] Open
Abstract
HIV-1 recognition by, interaction with, and/or infection of CD4(+)CCR5(+) tissue macrophages and dendritic cells (DCs) play important roles in HIV-1 transmission and pathogenesis. By comparison, circulating CD4(+)CCR5(+) monocytes appear relatively resistant to HIV-1, and a fundamental unresolved question involves deciphering restriction factors unique to this precursor population. Not only do monocytes, relative to macrophages, possess higher levels of the innate resistance factor APOBEC3G, but we uncovered APOBEC3A, not previously associated with anti-HIV activity, as being critical in monocyte resistance. Inversely correlated with susceptibility, silencing of APOBEC3A renders monocytes vulnerable to HIV-1. Differences in promiscuity of monocytes, macrophages, and DCs can be defined, at least partly, by disparities in APOBEC expression, with implications for enhancing cellular defenses against HIV-1.
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Affiliation(s)
- Gang Peng
- Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-4352, USA
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33
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Abstract
Interleukin (IL)-5 induces CD38-activated splenic B cells to differentiate into immunoglobulin M-secreting cells and undergo micro to gamma 1 class switch recombination (CSR) at the DNA level, resulting in immunoglobulin G1 (IgG1) production. Interestingly, IL-4, a well-known IgG1-inducing factor does not induce immunoglobulin production or micro to gamma 1 CSR in CD38-activated B cells. In the present study, we implemented complementary DNA microarrays to investigate the contribution of IL-5-induced gene expression in CD38-stimulated B cells to immunoglobulin-secreting cell differentiation and micro to gamma 1 CSR. IL-5 and IL-4 stimulation of CD38-activated B cells induced the expression of 418 and 289 genes, respectively, that consisted of several clusters. Surprisingly, IL-5-inducible 78 genes were redundantly regulated by IL-4. IL-5 and IL-4 also suppressed the gene expression of 319 and 325 genes, respectively, 97 of which were overlapped. Genes critically regulated by IL-5 include immunoglobulin-related genes such as J chain and immunoglobulinkappa, and genes involved in B-cell maturation such as BCL6, activation-induced cytidine deaminase (Aid) and B lymphocyte-induced maturation protein-1 (Blimp-1) and tend to be induced slowly after IL-5 stimulation. Intriguingly, among genes, the retroviral induction of Blimp-1 and Aid in CD38-activated B cells could induce IL-4-dependent maturation to Syndecan-1+ antibody-secreting cells and micro to gamma 1 CSR, respectively, in CD38-activated B cells. Taken together, preferential Aid and Blimp-1 expression plays a critical role in IL-5-induced immunoglobulin-secreting cell differentiation and micro to gamma 1 CSR in CD38-activated B cells.
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Affiliation(s)
- Keisuke Horikawa
- Division of Immunology, Department of Microbiology and Immunology, the Institute of Medical Science, University of Tokyo, Tokyo, Japan
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34
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Li Z, Zhao C, Iglesias-Ussel MD, Polonskaya Z, Zhuang M, Yang G, Luo Z, Edelmann W, Scharff MD. The mismatch repair protein Msh6 influences the in vivo AID targeting to the Ig locus. Immunity 2006; 24:393-403. [PMID: 16618598 DOI: 10.1016/j.immuni.2006.02.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2005] [Revised: 01/20/2006] [Accepted: 02/10/2006] [Indexed: 11/25/2022]
Abstract
Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by activation-induced cytidine deaminase (AID), which preferentially deaminates deoxycytidines at WRC (W = A/T, R = A/G) motifs in vitro. The mechanisms responsible for targeting AID and for organizing the queue of enzymes involved in vivo have been elusive. Here, we examined point mutant knockin Msh6 mice (Msh6(TD/TD)), which lack the second phase of SHM but retain all the proteins involved, and found that AID was frequently targeted to non-WRC motifs. Unexpectedly, by comparing SHM and CSR in wild-type, Msh6(TD/TD), and age-matched Msh6(-/-) mice, we discovered that the presence of Msh6 protein influenced the AID targeting in phase one of SHM and mediated the proper targeting of recombination sites in CSR in vivo. Our data suggest that Msh6 plays a scaffolding role in the first phase of SHM, in addition to its enzymatic role in the second phase of SHM.
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Affiliation(s)
- Ziqiang Li
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
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35
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Abstract
Human IgM+ IgD+ CD27+ B cells have mutated Ig genes and harbor a splenic marginal zone (MZ) phenotype. In this issue, the group of R. Küppers has studied the expression of the enzyme activation-induced cytidine deaminase (AID) in human spleen samples by immunocytochemistry and failed to detect a significant AID-expressing subset in the MZ region. The consequences on the possible origin of these cells are discussed.
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36
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Willenbrock K, Jungnickel B, Hansmann ML, Küppers R. Human splenic marginal zone B cells lack expression of activation-induced cytidine deaminase. Eur J Immunol 2005; 35:3002-7. [PMID: 16180254 DOI: 10.1002/eji.200535134] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
It has been speculated that somatic hypermutation of rearranged immunoglobulin variable (V) region genes does not only take place in the germinal center (GC) microenvironment, but also in the marginal zone (MZ) of the spleen, and that human peripheral blood IgM-positive B cells with somatically mutated V region genes may derive from mutating MZ B cells. As somatic hypermutation is strictly dependent on the enzyme activation-induced cytidine deaminase (AID), we used an AID-specific monoclonal antibody that is suitable for immunohistochemical staining to analyze human splenic MZ cells for AID expression. Analysis of tissue sections from 29 spleens revealed only very rare MZ cells (approx. 0.05%) showing AID staining, whereas in 25 of the spleen samples strong AID staining of GC B cells was observed. Thus, there are virtually no AID-expressing MZ B cells, indicating that somatic hypermutation does not take place at a significant level in the MZ. Consequently, it appears unlikely that the somatically mutated IgM B cells are generated in the splenic MZ. Moreover, the lack of AID-positive MZ B cells questions the recent speculation that B cell chronic lymphocytic leukemias with mutated V genes are derived from mutating MZ B cells.
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Affiliation(s)
- Klaus Willenbrock
- Senckenberg Institute of Pathology, University of Frankfurt, Frankfurt a.M., Germany
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37
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Greiner A, Tobollik S, Buettner M, Jungnickel B, Herrmann K, Kremmer E, Niedobitek G. Differential expression of activation-induced cytidine deaminase (AID) in nodular lymphocyte-predominant and classical Hodgkin lymphoma. J Pathol 2005; 205:541-7. [PMID: 15732141 DOI: 10.1002/path.1746] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Activation-induced cytidine deaminase (AID) is indispensable for class switch recombination and somatic hypermutation of immunoglobulin genes. Expression of AID has been detected in germinal centre centroblasts and in lymphomas derived from germinal centre cells. However, in situ studies of AID expression have until now been hampered by a lack of antibodies suitable for immunohistochemistry. To overcome this problem, an AID-specific monoclonal antibody suitable for immunohistochemical staining of formalin-fixed, paraffin wax-embedded tissue sections has been generated. This antibody was shown to detect AID expression in normal germinal centre B-cells as well as in non-Hodgkin lymphomas with a putative germinal centre origin. Using this antibody, a virtually exclusive cytoplasmic localization of AID in normal and neoplastic B-cells is shown. Employing a combination of immunohistochemistry and AID-specific in situ hybridization, it is demonstrated that AID is consistently expressed in the neoplastic cells of nodular lymphocyte-predominant Hodgkin lymphoma (HLnlp) but only infrequently in classical HL (cHL). This is in keeping with the notion that tumour cells of HLnlp represent transformed germinal centre B-cells showing evidence of somatic hypermutation. AID represents an additional marker useful in the differential diagnosis of HLnlp and cHL.
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Affiliation(s)
- Axel Greiner
- Institute for Pathology, Friedrich-Alexander-University, 91054 Erlangen, Germany
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38
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Abstract
BACKGROUND CD40 ligation activates nuclear factor kappaB (NF-kappaB) and the mitogen-activated protein kinases p38 and C-Jun N-terminal kinase (JNK) and causes immunoglobulin class-switch recombination (CSR) in B cells. Both NF-kappaB and p38 are important for CD40-mediated CSR. The role of JNK activation in CD40-mediated isotype switching is unknown. OBJECTIVE We sought to determine the role of JNK activation in CD40-mediated isotype switching. METHODS Splenic B cells from BALB/c mice were stimulated with anti-CD40 mAb and IL-4 or with soluble CD40 ligand in the presence or absence of SP600125, an anthrapyrazolone inhibitor of JNK. The following events were examined: IgE production by means of ELISA; S(mu)-S(epsilon) deletional switch recombination by means of digestion circularization PCR; Cepsilon germline, mature epsilon, and activation-induced deaminase (AID) transcription by means of RT-PCR; and proliferation by tritiated thymidine incorporation and surface expression of CD23, CD54, and CD86 by means of FACS analysis. RESULTS SP600125 at 10 microM drastically inhibited JNK phosphorylation but had little effect on CD40-mediated p38 phosphorylation and expression of the NF-kappaB dependent genes c-Myc and bcl-xL. SP600125 inhibited IgE synthesis by approximately 88% but had no effect on B-cell proliferation and survival in response to anti-CD40 + IL-4 or on upregulation of CD23, CD54, and CD86 in response to CD40 ligation. Analysis of molecular events involved in IgE class switching revealed that SP600125 had no effect on the expression of C(epsilon) germline and AID transcripts. In contrast, SP600125 severely reduced S(mu)-S(epsilon) switch recombination and expression of mature epsilon transcripts. CONCLUSION These results demonstrate that JNK activation is essential for CD40-mediated CSR to IgE and suggest that JNK is important for AID activity in B cells.
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Affiliation(s)
- Haifa H Jabara
- Division of Immunology, Children's Hospital, KARP Building #10126, 1 Blackfan Circle, Boston, MA 02115, USA.
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39
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Abstract
A powerful mechanism of vertebrate innate immunity has been discovered in the past year, in which APOBEC proteins inhibit retroviruses by deaminating cytosine residues in nascent retroviral cDNA. To thwart this cellular defence, HIV encodes Vif, a small protein that mediates APOBEC degradation. Therefore, the balance between APOBECs and Vif might be a crucial determinant of the outcome of retroviral infection. Vertebrates have up to 11 different APOBEC proteins, with primates having the most. APOBEC proteins include AID, a probable DNA mutator that is responsible for immunoglobulin-gene diversification, and APOBEC1, an RNA editor with antiretroviral activities. This APOBEC abundance might help to tip the balance in favour of cellular defences.
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Affiliation(s)
- Reuben S Harris
- University of Minnesota, Biochemistry, Molecular Biology and Biophysics Department, 321 Church Street South East, 6-155 Jackson Hall, Minneapolis, Minnesota 55455, USA.
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40
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Oppezzo P, Dumas G, Lalanne AI, Payelle-Brogard B, Magnac C, Pritsch O, Dighiero G, Vuillier F. Different isoforms of BSAP regulate expression of AID in normal and chronic lymphocytic leukemia B cells. Blood 2004; 105:2495-503. [PMID: 15561888 DOI: 10.1182/blood-2004-09-3644] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Activation-induced cytidine deaminase (AID) is key to initiating somatic hypermutation (SHM) and class switch recombination (CSR), but its mode of action and regulation remains unclear. Since Pax-5 and Id-2 transcription factors play an opposing role in AID regulation, we have studied the expression of Pax-5, Id-2, and prdm-1 genes in 54 chronic lymphocytic leukemia (CLL) B cells. In 21 cases, presence of AID is constantly associated with high expression of the complete form of the Pax-5 gene (Pax-5a) and lower expression of the Id-2 and prdm-1 transcripts. In 33 cases, the absence of AID expression and CSR is associated with a reduction of Pax-5a and the appearance of a spliced form with a deletion in exon 8 (Pax-5/Delta-Ex8). Stimulation with CD40L+interleukin 4 (IL-4) induces CSR, the presence of AID transcripts, up-regulation of Pax-5a and down-regulation of Pax-5/Delta-Ex8, and Id-2 and prdm-1 transcripts. Pax-5a and Pax-5/Delta-Ex8 are translated into 2 isoforms of the B-cell-specific activator protein (BSAP) and both are able to bind the AID-promoter region. Overall, these results suggest that Pax-5/Delta-Ex8 could play an important role in the control of its own transcription and indirectly in AID expression and CSR.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- B-Lymphocytes/pathology
- Base Sequence
- CD40 Ligand
- Cytidine Deaminase
- Cytosine Deaminase/immunology
- Cytosine Deaminase/metabolism
- Female
- Gene Expression Regulation, Enzymologic/immunology
- Gene Expression Regulation, Leukemic/immunology
- Humans
- Inhibitor of Differentiation Protein 2/immunology
- Inhibitor of Differentiation Protein 2/metabolism
- Leukemia, Lymphocytic, Chronic, B-Cell/immunology
- Leukemia, Lymphocytic, Chronic, B-Cell/metabolism
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- Male
- Middle Aged
- PAX5 Transcription Factor/immunology
- PAX5 Transcription Factor/metabolism
- Positive Regulatory Domain I-Binding Factor 1
- Protein Isoforms/immunology
- Protein Isoforms/metabolism
- Repressor Proteins/immunology
- Repressor Proteins/metabolism
- Sequence Deletion/immunology
- Somatic Hypermutation, Immunoglobulin/immunology
- Transcription Factors/immunology
- Transcription Factors/metabolism
- Transcription, Genetic/immunology
- Tumor Cells, Cultured
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Affiliation(s)
- Pablo Oppezzo
- Unité d'Immuno-hématologie et d'Immunopathologie, Institut Pasteur, 28 Rue Docteur Roux, 75015 Paris, France.
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41
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Pasqualucci L, Guglielmino R, Houldsworth J, Mohr J, Aoufouchi S, Polakiewicz R, Chaganti RSK, Dalla-Favera R. Expression of the AID protein in normal and neoplastic B cells. Blood 2004; 104:3318-25. [PMID: 15304391 DOI: 10.1182/blood-2004-04-1558] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Abstract
Somatic hypermutation (SHM) targets primarily the immunoglobulin variable region (IgV) genes in germinal center (GC) B cells, thereby allowing antibody affinity maturation. A malfunction of SHM, termed aberrant somatic hypermutation (ASHM), was found in about 50% of diffuse large B-cell lymphomas (DLBCLs), leading to mutations in the 5′ sequences of multiple genes, including oncogenes. Although the SHM mechanism is largely unknown, it was shown to require the activation-induced cytidine deaminase (AID) gene. AID mRNA is expressed in GC B cells and GC-derived lymphomas, but the pattern of expression of the AID protein is not known. Using 2 specific antibodies, here we show that the AID protein can be detected in GC centroblasts and their transformed counterpart (Burkitt lymphoma) but not in pre-GC B cells and post-GC neoplasms, including B-cell chronic lymphocytic leukemia and multiple myeloma. DLBCLs displayed variable levels of AID expression, which did not correlate with IgV ongoing hypermutation, ASHM, or disease subtype. Finally, both in normal and malignant B cells the AID protein appeared predominantly localized in the cytoplasm. These results indicate that the AID protein is specifically expressed in normal and transformed GC B cells; nonetheless, its predominantly cytoplasmic localization suggests that additional mechanisms may regulate its function and may be altered during lymphomagenesis. (Blood. 2004;104:3318-3325)
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Affiliation(s)
- Laura Pasqualucci
- Institute for Cancer Genetics, Department of Pathology, Columbia University, 1150 St Nicholas Ave, New York, NY 10032, USA.
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42
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Luo Z, Ronai D, Scharff MD. The role of activation-induced cytidine deaminase in antibody diversification, immunodeficiency, and B-cell malignancies. J Allergy Clin Immunol 2004; 114:726-35; quiz 736. [PMID: 15480307 DOI: 10.1016/j.jaci.2004.07.049] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Before exposure to antigen, antibodies with a wide diversity of antigen-binding sites are created by V(D)J rearrangement. After exposure to antigen, further diversification is accomplished by means of somatic hypermutation of the antibody variable region genes and class-switch recombination between the heavy-chain mu constant region and the downstream gamma, epsilon, and alpha constant region. The variable region mutations are responsible for the affinity maturation of the antibody response, whereas class-switch recombination enables the antibodies to be distributed throughout the body and to carry out different effector functions. Both somatic mutation and class switching require an enzyme called activation-induced cytidine deaminase (AID) that converts deoxycytidines to deoxyuracils on single-stranded DNA. Genetic defects of AID in human subjects result in hyper-IgM syndrome type 2. The analysis of both mutant mice and immunodeficient patients has led to a better understanding of the mechanism of action and role of AID in immunity, as well as in the malignant transformation of B cells.
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Affiliation(s)
- Zhonghui Luo
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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