101
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Hulme AE, Bogerd HP, Cullen BR, Moran JV. Selective inhibition of Alu retrotransposition by APOBEC3G. Gene 2006; 390:199-205. [PMID: 17079095 PMCID: PMC2917221 DOI: 10.1016/j.gene.2006.08.032] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 08/23/2006] [Accepted: 08/24/2006] [Indexed: 11/30/2022]
Abstract
The non-LTR retrotransposon LINE-1 (L1) comprises approximately 17% of the human genome, and the L1-encoded proteins can function in trans to mediate the retrotransposition of non-autonomous retrotransposons (i.e., Alu and probably SVA elements) and cellular mRNAs to generate processed pseudogenes. Here, we have examined the effect of APOBEC3G and APOBEC3F, cytidine deaminases that inhibit Vif-deficient HIV-1 replication, on Alu retrotransposition and other L1-mediated retrotransposition processes. We demonstrate that APOBEC3G selectively inhibits Alu retrotransposition in an ORF1p-independent manner. An active cytidine deaminase site is not required for the inhibition of Alu retrotransposition and the resultant integration events lack G to A or C to T hypermutation. These data demonstrate a differential restriction of L1 and Alu retrotransposition by APOBEC3G, and suggest that the Alu ribonucleoprotein complex may be targeted by APOBEC3G.
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Affiliation(s)
- Amy E. Hulme
- Department of Human Genetics, The University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Paper correspondence should be addressed to or
| | - Hal P. Bogerd
- Center for Virology and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Bryan R. Cullen
- Center for Virology and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - John V. Moran
- Department of Human Genetics, The University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Internal Medicine, The University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Paper correspondence should be addressed to or
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102
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Muckenfuss H, Hamdorf M, Held U, Perković M, Löwer J, Cichutek K, Flory E, Schumann GG, Münk C. APOBEC3 proteins inhibit human LINE-1 retrotransposition. J Biol Chem 2006; 281:22161-22172. [PMID: 16735504 DOI: 10.1074/jbc.m601716200] [Citation(s) in RCA: 291] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The human cytidine deaminase family APOBEC3 represents a novel group of proteins in the field of innate defense mechanisms that has been shown to be active against a variety of retroviruses. Here we examined whether members of the APO-BEC3 family have an impact on retrotransposition of human long interspersed nuclear elements (LINE-1s or L1s). Using a retrotransposition reporter assay in HeLa cells, we demonstrate that in the presence of transiently transfected APOBEC3A, L1 retrotransposition frequency was reduced by up to 85%. Although APOBEC3G and -3H did not influence L1 retrotransposition notably, expression of APOBEC3B, -3C, and -3F inhibited transposition by approximately 75%. Although reverse transcription of L1s occurs in the nucleus and APOBEC3 proteins are believed to act via DNA deamination during reverse transcription, activity against L1 retrotransposition was not correlated with nuclear localization of APOBEC3s. We demonstrate that APOBEC3C and APOBEC3B were endogenously expressed in HeLa cells. Accordingly, down-regulation of APOBEC3C by RNA interference enhanced L1 retrotransposition by approximately 78%. Sequence analyses of de novo L1 retrotransposition events that occurred in the presence of overexpressed APOBEC3 proteins as well as the analyses of pre-existing endogenous L1 elements did not reveal an enhanced rate of G-to-A transitions, pointing to a mechanism independent of DNA deamination. This study presents evidence for a role of host-encoded APOBEC3 proteins in the regulation of L1 retrotransposition.
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Affiliation(s)
- Heide Muckenfuss
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Matthias Hamdorf
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Ulrike Held
- Section Pr2/Retroelements, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Mario Perković
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Johannes Löwer
- Section Pr2/Retroelements, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Klaus Cichutek
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Egbert Flory
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany
| | - Gerald G Schumann
- Section Pr2/Retroelements, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany.
| | - Carsten Münk
- Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany.
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103
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Abstract
APOBEC3G (A3G), a deoxycytidine deaminase, is a powerful host antiretroviral factor that can restrict HIV-1 infection. This restriction is counteracted by the HIV-1 virion infectivity factor (Vif) protein, whose activity culminates in depletion of A3G from infected cells. In the absence of Vif, viruses encapsidate A3G, which acts in part to mutate viral DNA formed during reverse transcription upon subsequent infection of a new cell. Cellular A3G also functions as a post-entry restriction factor for HIV in resting CD4 T cells, where it resides in a low molecular mass form. Unfortunately, this barrier is forfeited when CD4 T cells are activated because A3G is recruited into inactive high molecular mass ribonucleoprotein complexes. In addition to restricting HIV, A3G and related deaminases may counter other retroviruses and protect the cell from endogenous mobile retroelements. Understanding A3G complex assembly and its interplay with HIV Vif may make possible future development of a new class of HIV therapeutic agents.
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Affiliation(s)
- Vanessa B Soros
- Gladstone Institute of Virology and Immunology, Department of Medicine, University of California, San Francisco, 1650 Owens Street, CA 94158-2261, USA
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104
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Folgueira MAAK, Brentani H, Katayama MLH, Patrão DFC, Carraro DM, Mourão Netto M, Barbosa EM, Caldeira JRF, Abreu APS, Lyra EC, Kaiano JHL, Mota LD, Campos AHJFM, Maciel MS, Dellamano M, Caballero OLSD, Brentani MM. Gene expression profiling of clinical stages II and III breast cancer. Braz J Med Biol Res 2006; 39:1101-13. [PMID: 16906285 DOI: 10.1590/s0100-879x2006000800013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Accepted: 04/24/2006] [Indexed: 11/22/2022] Open
Abstract
Clinical stage (CS) is an established indicator of breast cancer outcome. In the present study, a cDNA microarray platform containing 692 genes was used to identify molecular differences between CSII and CSIII disease. Tumor samples were collected from patients with CSII or CSIII breast cancer, and normal breast tissue was collected from women without invasive cancer. Seventy-eight genes were deregulated in CSIII tumors and 22 in CSII tumors when compared to normal tissue, and 20 of them were differentially expressed in both CSII and CSIII tumors. In addition, 58 genes were specifically altered in CSIII and expression of 6 of them was tested by real time RT-PCR in another cohort of patients with CSII or CSIII breast cancer and in women without cancer. Among these genes, MAX, KRT15 and S100A14, but not APOBEC3G or KRT19, were differentially expressed on both CSIII and CSII tumors as compared to normal tissue. Increased HMOX1 levels were detected only in CSIII tumors and may represent a molecular marker of this stage. A clear difference in gene expression pattern occurs at the normal-to-cancer transition; however, most of the differentially expressed genes are deregulated in tumors of both CS (II and III) compared to normal breast tissue.
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Affiliation(s)
- M A A K Folgueira
- Disciplina de Oncologia, Departamento de Radiologia, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brasil
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105
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Abstract
Since the beginning of time, microorganisms have been devising ways to bypass detection and destruction by our immune system. Therefore, it is no surprise that along with the identification of the cellular antiviral protein APOBEC3G (A3G) has come the recognition of the viral solution to this assault. Here, we review the research that led up to the identification of A3G and the mechanism that the human immunodeficiency virus protein Vif developed to evade A3G's antiviral activities.
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Affiliation(s)
- Elana S Ehrlich
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
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106
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Stenglein MD, Harris RS. APOBEC3B and APOBEC3F Inhibit L1 Retrotransposition by a DNA Deamination-independent Mechanism. J Biol Chem 2006; 281:16837-16841. [PMID: 16648136 DOI: 10.1074/jbc.m602367200] [Citation(s) in RCA: 221] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most common transposable genetic element in humans, long interspersed element 1 (L1), constitutes about 20% of the genome. The activity of L1 and related transposons such as Alu elements causes disease and contributes to speciation. Little is known about the cellular mechanisms that control their spread. We show that expression of human APOBEC3B or APOBEC3F decreased the rate of L1 retrotransposition by 5-10-fold. Expression of two related proteins, APOBEC3D or APOBEC3G, had little effect. The mechanism of L1 inhibition did not correlate with an obvious subcellular protein distribution as APOBEC3B appeared predominantly nuclear and APOBEC3F was mostly cytosolic. Two lines of evidence indicated that these APOBEC3 proteins use a deamination-independent mechanism to inhibit L1. First, a catalytically inactive APOBEC3B mutant maintained L1 inhibition activity. Second, cDNA strand-specific C --> T hypermutations were not detected among L1 elements that had replicated in the presence of APOBEC3B or APOBEC3F. In addition, lower levels of retrotransposed L1 DNA accumulated in the presence of APOBEC3B and APOBEC3F. Together, these data combined to suggest a model in which APOBEC3B or APOBEC3F provide a preintegration barrier to L1 retrotransposition. A particularly high level of APOBEC3F protein in human testes and an inverse correlation between L1 activity and APOBEC3 gene number suggest the relevance of this mechanism to mammals.
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Affiliation(s)
- Mark D Stenglein
- Department of Biochemistry, Molecular Biology and Biophysics, The Institute for Molecular Virology and The Beckman Center for Transposon Research, the University of Minnesota, Minneapolis, Minnesota 55455
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, The Institute for Molecular Virology and The Beckman Center for Transposon Research, the University of Minnesota, Minneapolis, Minnesota 55455.
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107
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Bonvin M, Achermann F, Greeve I, Stroka D, Keogh A, Inderbitzin D, Candinas D, Sommer P, Wain-Hobson S, Vartanian JP, Greeve J. Interferon-inducible expression of APOBEC3 editing enzymes in human hepatocytes and inhibition of hepatitis B virus replication. Hepatology 2006; 43:1364-74. [PMID: 16729314 DOI: 10.1002/hep.21187] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hypermutations in hepatitis B virus (HBV) DNA by APOBEC3 cytidine deaminases have been detected in vitro and in vivo, and APOBEC3G (A3G) and APOBEC3F (A3F) have been shown to inhibit the replication of HBV in vitro, but the presumably low or even absent hepatic expression of these enzymes has raised the question as to their physiological impact on HBV replication. We show that normal human liver expresses the mRNAs of APOBEC3B (A3B), APOBEC3C (A3C), A3F, and A3G. In primary human hepatocytes, interferon alpha (IFN-alpha) stimulated the expression of these cytidine deaminases up to 14-fold, and the mRNAs of A3G, A3F, and A3B reached expression levels of 10%, 3%, and 3%, respectively, relative to GAPDH mRNA abundance. On transfection, the full-length protein A3B(L) inhibited HBV replication in vitro as efficiently as A3G or A3F, whereas the truncated splice variant A3B(S) and A3C had no effect. A3B(L) and A3B(S) were detected predominantly in the nucleus of uninfected cells; however, in HBV-expressing cells both proteins were found also in the cytoplasm and were associated with HBV viral particles, similarly to A3G and A3F. Moreover, A3G, A3F, and A3B(L), but not A3B(S), induced extensive G-to-A hypermutations in a fraction of the replicated HBV genomes. In conclusion, the editing enzymes A3B(L), A3F, and most markedly A3G, which are expressed in liver and up-regulated by IFN-alpha in hepatocytes, are candidates to contribute to the noncytolytic clearance of HBV.
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Affiliation(s)
- Marianne Bonvin
- Department of Clinical Research,University Hospital Berne, Switzerland
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108
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Chiu YL, Greene WC. Multifaceted antiviral actions of APOBEC3 cytidine deaminases. Trends Immunol 2006; 27:291-7. [PMID: 16678488 DOI: 10.1016/j.it.2006.04.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 03/16/2006] [Accepted: 04/20/2006] [Indexed: 12/19/2022]
Abstract
To defend against external pathogens, metazoan organisms have evolved numerous defenses that generally fall within the innate and adaptive immune responses. Considerable effort continues to focus on developing a vaccine to manipulate the adaptive immune system to protect against or control HIV-1. However, recent advances in our understanding of the innate immune system have revealed that cells have a potent intrinsic antiretroviral defense in the form of APOBEC3G, which is a member of a larger family of cytidine deaminases that are active against HIV-1 and other retroviruses. Insights into how the action of A3G is circumvented by HIV-1 through the action of its Vif protein, and the surprising mechanisms by which A3G is regulated within the cell, offer exciting new opportunities for developing novel anti-HIV-1 therapies that exploit this intrinsic antiretroviral system.
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Affiliation(s)
- Ya-Lin Chiu
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA 94141-9100, USA
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109
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Tian C, Yu X, Zhang W, Wang T, Xu R, Yu XF. Differential requirement for conserved tryptophans in human immunodeficiency virus type 1 Vif for the selective suppression of APOBEC3G and APOBEC3F. J Virol 2006; 80:3112-5. [PMID: 16501124 PMCID: PMC1395459 DOI: 10.1128/jvi.80.6.3112-3115.2006] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
APOBEC3G (A3G) and related cytidine deaminases, such as APOBEC3F (A3F), are potent inhibitors of retroviruses. Formation of infectious human immunodeficiency virus type 1 (HIV-1) requires suppression of multiple cytidine deaminases by Vif. Whether HIV-1 Vif recognizes various APOBEC3 proteins through a common mechanism is unclear. The domains in Vif that mediate APOBEC3 recognitions are also poorly defined. The N-terminal region of HIV-1 Vif is unusually rich in Trp residues, which are highly conserved. In the present study, we examined the role of these Trp residues in the suppression of APOBEC3 proteins by HIV-1 Vif. We found that most of the highly conserved Trp residues were required for efficient suppression of both A3G and A3F, but some of these residues were selectively required for the suppression of A3F but not A3G. Mutant Vif molecules in which Ala was substituted for Trp79 and, to a lesser extent, for Trp11 remained competent for A3G interaction and its suppression; however, they were defective for A3F interaction and therefore could not efficiently suppress the antiviral activity of A3F. Interestingly, while the HIV-1 Vif-mediated degradation of A3G was not affected by the different C-terminal tag peptides, that of A3F was significantly influenced by its C-terminal tags. These data indicate that the mechanisms by which HIV-1 Vif recognizes its target molecules, A3G and A3F, are not identical. The fact that several highly conserved residues in Vif are required for the suppression of A3F but not that of A3G suggests a critical role for A3F in the restriction of HIV-1 in vivo.
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Affiliation(s)
- Chunjuan Tian
- Second Affiliated Hospital, Cancer Institute, School of Medicine, Zhejiang University, Hangzhou, China
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110
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OhAinle M, Kerns JA, Malik HS, Emerman M. Adaptive evolution and antiviral activity of the conserved mammalian cytidine deaminase APOBEC3H. J Virol 2006; 80:3853-62. [PMID: 16571802 PMCID: PMC1440450 DOI: 10.1128/jvi.80.8.3853-3862.2006] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Accepted: 01/30/2006] [Indexed: 01/01/2023] Open
Abstract
The APOBEC3 genes encode cytidine deaminases that act as components of an intrinsic immune defense that have potent activity against a variety of retroelements. This family of genes has undergone a rapid expansion from one or two genes in nonprimate mammals to at least seven members in primates. Here we describe the evolution and function of an uncharacterized antiviral effector, APOBEC3H, which represents the most evolutionarily divergent APOBEC3 gene found in primates. We found that APOBEC3H has undergone significant adaptive evolution in primates. Consistent with our previous findings implicating adaptively evolving APOBEC3 genes as antiviral effectors, APOBEC3H from Old World monkeys (OWMs) has efficient antiviral activity against primate lentiviruses, is sensitive to inactivation by the simian immunodeficiency virus Vif protein, and is capable of hypermutating retroviral genomes. In contrast, human APOBEC3H is inherently poorly expressed in primate cells and is ineffective at inhibiting retroviral replication. Both OWM and human APOBEC3H proteins can be expressed in bacteria, where they display significant DNA mutator activity. Thus, humans have retained an APOBEC3H gene that encodes a functional, but poorly expressed, cytidine deaminase with no apparent antiviral activity. The consequences of the lack of antiviral activity of human APOBEC3H are likely to be relevant to the current-day abilities of humans to combat retroviral challenges.
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Affiliation(s)
- Molly OhAinle
- Molecular and Cellular Biology Program, University of Washington, Seattle 98109, USA
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111
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Chiu YL, Greene WC. APOBEC3 cytidine deaminases: distinct antiviral actions along the retroviral life cycle. J Biol Chem 2006; 281:8309-12. [PMID: 16407183 DOI: 10.1074/jbc.r500021200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The field of human immunodeficiency virus (HIV) biology has been galvanized by the discovery of innate APOBEC3 cytidine deaminases, which pose powerful barriers to the replication of HIV and other retroviruses. Rapid progress has been made in defining their action, intriguing regulation within cells, expanded range of retroviral targets, and counterstrikes utilized by retroviruses against them. Although scientifically fascinating, advances in APOBEC3 biology may lead to new antiviral drugs and improved lentiviral vectors for gene therapy.
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Affiliation(s)
- Ya-Lin Chiu
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, CA 94141, USA
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112
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Affiliation(s)
- Donna A Macduff
- University of Minnesota, Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Beckman Center for Transposon Research, Minneapolis, Minnesota 55455, USA
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113
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Esnault C, Millet J, Schwartz O, Heidmann T. Dual inhibitory effects of APOBEC family proteins on retrotransposition of mammalian endogenous retroviruses. Nucleic Acids Res 2006; 34:1522-31. [PMID: 16537839 PMCID: PMC1401513 DOI: 10.1093/nar/gkl054] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We demonstrated previously that the cytosine deaminase APOBEC3G inhibits retrotransposition of two active murine endogenous retroviruses, namely intracisternal A-particles (IAP) and MusD, in an ex vivo assay where retrotransposition was monitored by selection of neo-marked elements. Sequencing of the transposed copies further disclosed extensive editing, resulting in a high load of G-to-A mutations. Here, we asked whether this G-to-A editing was associated with an impact of APOBEC3G on viral cDNA yields. To this end, we used a specially designed quantitative PCR method to selectively measure the copy number of transposed retroelements, in the absence of G418 selection. We show that human APOBEC3G severely reduces the number of MusD and IAP transposed cDNA copies, with no effect on the level of the intermediate RNA transcripts. The magnitude of the decrease closely parallels that observed when transposed copies are assayed by selection of G418-resistant cells. Moreover, sequencing of transposed elements recovered by PCR without prior selection of the cells reveals high-level editing. Using this direct method with a series of cytosine deaminases, we further demonstrate a similar dual effect of African green monkey APOBE3G, human APOBEC3F and murine APOBEC3 on MusD retrotransposition, with a distinct extent and site specificity for each editing activity. Altogether the data demonstrate that cytosine deaminases have a protective effect against endogenous retroviruses both by reducing viral cDNA levels and by introducing mutations in the transposed copies, thus inactivating them for subsequent rounds of retrotransposition. This dual, two-step effect likely participates in the efficient defense of the cell genome against invading endogenous retroelements.
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Affiliation(s)
| | | | - Olivier Schwartz
- Department of Virology, Virus and Immunity Group, Institut Pasteur, CNRS URA 193075015 Paris, France
| | - Thierry Heidmann
- To whom correspondence should be addressed. Tel: +33 1 42 11 49 70; Fax: +33 1 42 11 53 42;
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114
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Xiao Z, Ehrlich E, Yu Y, Luo K, Wang T, Tian C, Yu XF. Assembly of HIV-1 Vif-Cul5 E3 ubiquitin ligase through a novel zinc-binding domain-stabilized hydrophobic interface in Vif. Virology 2006; 349:290-9. [PMID: 16530799 DOI: 10.1016/j.virol.2006.02.002] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 01/02/2006] [Accepted: 02/02/2006] [Indexed: 02/08/2023]
Abstract
APOBEC3G (A3G) and related cytidine deaminases are potent inhibitors of retroviruses. HIV-1 Vif hijacks the cellular Cul5-E3 ubiquitin ligase to degrade APOBEC3 proteins and render them ineffective against these viruses. Here, we report that HIV-1 Vif is a novel zinc-binding protein containing an H-x(5)-C-x(17-18)-C-x(3-5)-H motif that is distinct from other recognized classes of zinc fingers. Zinc-binding stabilized a conserved hydrophobic interface within the HCCH motif that is critical for Vif-Cul5 E3 assembly and Vif function. An N-terminal region in the first Cullin repeat of Cul5, which is dispensable for adaptor ElonginC binding, was required for interaction with Vif. This region is the most divergent sequence between Cul2 and Cul5, a factor that may contribute to the selection of Cul5 and not Cul2 by Vif. This is the first example of a zinc-binding substrate receptor responsible for the assembly of a Cullin-RING ligase, representing a new target for antiviral development.
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Affiliation(s)
- Zuoxiang Xiao
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
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115
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Affiliation(s)
- Bryan R Cullen
- Department of Molecular Genetics and Microbiology, Box 3025, Duke University Medical Center, Durham, NC 27710, USA.
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116
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Cho SJ, Drechsler H, Burke RC, Arens MQ, Powderly W, Davidson NO. APOBEC3F and APOBEC3G mRNA levels do not correlate with human immunodeficiency virus type 1 plasma viremia or CD4+ T-cell count. J Virol 2006; 80:2069-72. [PMID: 16439564 PMCID: PMC1367163 DOI: 10.1128/jvi.80.4.2069-2072.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
APOBEC3F and APOBEC3G (hA3F and hA3G) are part of an innate mechanism of antiretroviral defense. The human immunodeficiency virus type 1 (HIV-1) accessory protein Vif targets both proteins for proteasomal degradation. Using mRNA from peripheral blood mononuclear cells of 92 HIV-infected subjects not taking antiretroviral therapy and 19 HIV-uninfected controls, we found that hA3F (P < 0.001) and hA3G (P = 0.016) mRNA levels were lower in HIV-infected subjects and were positively correlated with one another (P = 0.003). However, we found no correlation in the abundance of either hA3F or hA3G mRNA with either viral load or CD4 counts in HIV-infected subjects.
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Affiliation(s)
- Soo-Jin Cho
- Washington University School of Medicine, Division of Gastroenterology, Box 8124, 660 S. Euclid Ave., St. Louis, MO 63110, USA
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117
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Delebecque F, Suspène R, Calattini S, Casartelli N, Saïb A, Froment A, Wain-Hobson S, Gessain A, Vartanian JP, Schwartz O. Restriction of foamy viruses by APOBEC cytidine deaminases. J Virol 2006; 80:605-14. [PMID: 16378963 PMCID: PMC1346872 DOI: 10.1128/jvi.80.2.605-614.2006] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Foamy viruses (FVs) are nonpathogenic retroviruses infecting many species of mammals, notably primates, cattle, and cats. We have examined whether members of the apolipoprotein B-editing catalytic polypeptide-like subunit (APOBEC) family of antiviral cytidine deaminases restrict replication of simian FV. We show that human APOBEC3G is a potent inhibitor of FV infectivity in cell culture experiments. This antiviral activity is associated with cytidine editing of the viral genome. Both molecular FV clones and primary uncloned viruses were susceptible to APOBEC3G, and viral infectivity was also inhibited by murine and simian APOBEC3G homologues, as well as by human APOBEC3F. Wild-type and bet-deleted viruses were similarly sensitive to this antiviral activity, suggesting that Bet does not significantly counteract APOBEC proteins. Moreover, we did not detect FV sequences that may have been targeted by APOBEC in naturally infected macaques, but we observed a few G-to-A substitutions in humans that have been accidentally contaminated by simian FV. In infected hosts, the persistence strategy employed by FV might be based on low levels of replication, as well as avoidance of cells expressing large amounts of active cytidine deaminases.
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Affiliation(s)
- Frédéric Delebecque
- Virus and Immunity Group, URA CNRS 1930, Institut Pasteur, 75724 Paris cedex 15, France
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Bogerd HP, Wiegand HL, Doehle BP, Lueders KK, Cullen BR. APOBEC3A and APOBEC3B are potent inhibitors of LTR-retrotransposon function in human cells. Nucleic Acids Res 2006; 34:89-95. [PMID: 16407327 PMCID: PMC1326241 DOI: 10.1093/nar/gkj416] [Citation(s) in RCA: 223] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
While the ability of APOBEC3G to reduce the replication of a range of exogenous retroviruses is now well established, recent evidence has suggested that APOBEC3G can also inhibit the replication of endogenous retrotransposons that bear long terminal repeats. Here, we extend this earlier work by showing that two other members of the human APOBEC3 protein family, APOBEC3B and APOBEC3A, can reduce retrotransposition by the intracisternal A-particle (IAP) retrotransposon in human cells by 20-fold to up to 100-fold, respectively. This compares to an ∼4-fold inhibition in IAP retrotransposition induced by APOBEC3G. While both APOBEC3G and APOBEC3B specifically interact with the IAP Gag protein in co-expressing cells, and induce extensive editing of IAP reverse transcripts, APOBEC3A fails to package detectably into IAP virus-like particles and does not edit IAP reverse transcripts. These data, which identify human APOBEC3A as a highly potent inhibitor of LTR-retrotransposon function, are the first to ascribe a biological activity to APOBEC3A. Moreover, these results argue that APOBEC3A inhibits IAP retrotransposition via a novel mechanism that is distinct from, and in this case more effective than, the DNA editing mechanism characteristic of APOBEC3G and APOBEC3B.
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Affiliation(s)
| | | | | | - Kira K. Lueders
- Laboratory of Biochemistry, National Cancer Institute, National Institutes of HealthBethesda, MD 20895, USA
| | - Bryan R. Cullen
- To whom correspondence should be addressed. Tel: +1 919 684 3369; Fax: +1 919 681 8979;
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Current awareness on yeast. Yeast 2006. [DOI: 10.1002/yea.1172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Abstract
APOBEC3G is a potent antiretroviral factor, which belongs to the APOBEC superfamily of cytidine deaminases. It deaminates cytidine to uridine in nascent minus-strand viral DNA, inducing G-to-A hypermutation in the plus-strand viral DNA. HIV-1 Vif protein overcomes the antiviral activity of APOBEC3G by targeting it for ubiquitin-dependent degradation. Recent accumulating evidences that other members of APOBEC proteins also show antiviral activity on a wide variety of viruses suggest that APOBEC family proteins play a crucial role in an antiviral defense as an innate immunity. Here, we review recent progress in research on APOBEC3 proteins.
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Affiliation(s)
- Akifumi Takaori
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Japan.
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