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João Gonçalves - One of the best experts on this subject based on the ideXlab platform.
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HIV-1 Vif Protein blocks the cytidine deaminase activity of B-cell specific AID in E. coli by a similar mechanism of action.
Molecular immunology, 2006Co-Authors: Mariana Santa-marta, Frederico Aires Da Silva, Ana Margarida Fonseca, Sylvie Rato, João GonçalvesAbstract:HIV-1 Vif Protein protects viral replication in non-permissive cells by inducing degradation of APOBEC3G via ubiquitination and proteasomal pathway, although new studies indicate a putative role in Vif's direct inhibition of APOBEC3G. APOBEC3G is member of a homologous family of Proteins with cytidine deaminase activity expressed with characteristic tissue specificity, that in humans consist of APOBEC1, APOBEC2, APOBEC3A-H, APOBEC4 and the activation-induced deaminase (AID), a B lymphoid Protein necessary for somatic hypermutation, gene conversion and class switch recombination. In this work we show that Vif can counteract AID's activity in E. coli in absence of specific eukaryotic co-factors necessary for AID induced somatic hypermutation, gene conversion and to stimulate class switch recombination in B-cells. We show that AID inhibition is mediated by a direct Protein-Protein interaction via unique amino acid D118 an homologous mutant responsible for the species-specific restriction of HIV-1 Vif Protein existent for APOBEC3G. These results raise the hypothesis that Vif related Proteins can act as a broad inhibitor of deaminase activity. Moreover as AID and Vif evolved in different cellular environments, these results may indicate that Vif related Proteins might mimic cellular factors that interact with a structural conserved domain of cytidine deaminases during evolution.
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Functional Analysis of Vif Protein Shows Less Restriction of Human Immunodeficiency Virus Type 2 by APOBEC3G
Journal of virology, 2005Co-Authors: Ana Clara Ribeiro, João Gonçalves, Mariana Santa-marta, Alexandra Maia E Silva, Ana Pombo, José Moniz-pereira, Isabel BarahonaAbstract:Viral infectivity factor (Vif) is one of the human immunodeficiency virus (HIV) accessory Proteins and is conserved in the primate lentivirus group. This Protein is essential for viral replication in vivo and for productive infection of nonpermissive cells, such as peripheral blood mononuclear cells (PBMC). Vif counteracts an antiretroviral cellular factor in nonpermissive cells named CEM15/APOBEC3G. Although HIV type 1 (HIV-1) Vif Protein (Vif1) can be functionally replaced by HIV-2 Vif Protein (Vif2), its identity is very small. Most of the functional studies have been carried out with Vif1. Characterization of functional domains of Vif2 may elucidate its function, as well as differences between HIV-1 and HIV-2 infectivity. Our aim was to identify the permissivity of different cell lines for HIV-2 Vif-minus viruses. By mutagenesis specific conserved motifs of HIV-2 Vif Protein were analyzed, as well as in conserved motifs between Vif1 and Vif2 Proteins. Vif2 mutants were examined for their stability, expression, and cellular localization in order to characterize essential domains of Vif2 Proteins. Viral replication in various target cells (PBMC and H9, A3.01, U38, and Jurkat cells) and infectivity in single cycle assays in the presence of APOBEC3G were also analyzed. Our results of viral replication show that only PBMC have a nonpermissive phenotype in the absence of Vif2. Moreover, the HIV-1 Vif-minus nonpermissive cell line H9 does not show a similar phenotype for Vif-negative HIV-2. We also report a limited effect of APOBEC3G in a single-cycle infectivity assay, where only conserved domains between HIV-1 and HIV-2 Vif Proteins influence viral infectivity. Taken together, these results allow us to speculate that viral inhibition by APOBEC3G is not the sole and most important determinant of antiviral activity against HIV-2.
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HIV-1 Vif Can Directly Inhibit ApolipoProtein B mRNA-editing Enzyme Catalytic Polypeptide-like 3G-mediated Cytidine Deamination by Using a Single Amino Acid Interaction and Without Protein Degradation
The Journal of biological chemistry, 2004Co-Authors: Mariana Santa-marta, Frederico Aires Da Silva, Ana Margarida Fonseca, João GonçalvesAbstract:The human apolipoProtein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G), also known as CEM-15, is a host-cell factor involved in innate resistance to retroviral infection. HIV-1 viral infectivity factor (Vif) Protein was shown to protect the virus from APOBEC3G-mediated viral cDNA hypermutation. The mechanism proposed for protection of the virus by HIV-1 Vif is mediated by APOBEC3G degradation through ubiquitination and the proteasomal pathway. Here we show that in Escherichia coli the APOBEC3G-induced cytidine deamination is inhibited by expression of Vif without depletion of deaminase. Moreover, inhibition of deaminase-mediated bacterial hypermutation is dependent on a single amino acid substitution D128K that renders APOBEC3G resistant to Vif inhibition. This single amino acid was elegantly proven by other authors to determine species-specific sensitivity. Our results show that in bacteria this single amino acid substitution controls Vif-dependent blocking of APOBEC3G that is dependent on a strong Protein interaction. The C-terminal region of Vif is responsible for this strong Protein-Protein interaction. In conclusion, our experiments suggest a complement to the model of Vif-induced degradation of APOBEC3G by bringing to relevance that deaminase inhibition can also result from a direct interaction with Vif Protein.
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Functional neutralization of HIV-1 Vif Protein by intracellular immunization inhibits reverse transcription and viral replication.
The Journal of biological chemistry, 2002Co-Authors: João Gonçalves, Dana Gabuzda, Frederico Aires Da Silva, Acilino Freitas-vieira, Mariana Santa-marta, Rui Malhó, Xiaoyu Yang, Carlos F. BarbasAbstract:Human immunodeficiency virus type 1 (HIV-1)-encoded Vif Protein is important for viral replication and infectivity. Vif is a cytoplasmic Protein that acts during virus assembly by an unknown mechanism, enhancing viral infectivity. The action of Vif in producer cells is essential for the completion of proviral DNA synthesis following virus entry. Therefore, Vif is considered to be an important alternative therapeutic target for inhibition of viral infectivity at the level of viral assembly and reverse transcription. To gain insight into this process, we developed a Vif-specific single-chain antibody and expressed it intracellularly in the cytoplasm. This intrabody efficiently bound Vif Protein and neutralized its infectivity-enhancing function. Intrabody-expressing cells were shown to be highly refractory to challenge with different strains of HIV-1 and HIV-1-infected cells. Inhibition of Vif by intrabody expression in the donor cell produced viral particles that do not complete reverse transcription in the recipient cell. The anti-Vif scFv was shown to be specific for Vif Protein because its function was observed only in nonpermissive cells (H9, CEM, and U38). Moreover, transduction of peripheral blood mononuclear cells with an HIV-derived retroviral vector expressing Vif intrabody was shown to confer resistance to laboratory-adapted and primary HIV strains. This study provides biochemical evidence for the role of Vif in the HIV-1 lifecycle and validates Vif as a target for the control of HIV-1 infection.
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Subcellular localization of the Vif Protein of human immunodeficiency virus type 1.
Journal of virology, 1994Co-Authors: João Gonçalves, Prasad V. Jallepalli, Dana GabuzdaAbstract:Abstract The Vif (viral infectivity factor) Protein of human immunodeficiency virus type 1 (HIV-1) has been shown to dramatically enhance the infectivity of HIV-1 virus particles during virus production. The subcellular localization of Vif was examined to elucidate cellular pathways which may be important for Vif function. Indirect immunofluorescence staining of Vif demonstrated a diffuse cytoplasmic distribution and showed that most Vif was not associated with the Golgi complex, a proposed site of localization (B. Guy, M. Geist, K. Dott, D. Spehner, M.-P. Kieny, and J.-P. Lecocq, J. Virol. 65:1325-1331, 1991). Subcellular fractionation of transfected COS cells and HIV-1-infected Jurkat and CEM cells demonstrated that Vif is a cytoplasmic Protein which exists in both a soluble cytosolic form and membrane-associated form. The membrane-associated form of Vif is a peripheral membrane Protein which is tightly associated with the cytoplasmic side of cellular membranes. The C terminus of Vif was required for the stable association of Vif with membranes. The C terminus was also essential for Vif function, suggesting that the association of Vif with membranes is likely to be important for its biological activity. The highly conserved regions at residues 103 to 115 and 142 to 150 were important for Vif function but did not affect membrane association, indicating that these regions are likely to be important for other, as-yet-unknown functions.
Dana Gabuzda - One of the best experts on this subject based on the ideXlab platform.
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redoxal an inhibitor of de novo pyrimidine biosynthesis augments apobec3g antiviral activity against human immunodeficiency virus type 1
Virology, 2015Co-Authors: Erez Pery, Ann M Sheehy, Vikas Misra, Marie K Mankowski, Lynn Rasmussen, Miranda N Nebane, Lucile E White, Roger G Ptak, Dana GabuzdaAbstract:Abstract APOBEC3G (A3G) is a cytidine deaminase that restricts HIV-1 replication by inducing G-to-A hypermutation in viral DNA; deamination-independent mechanisms are also implicated. HIV-1 Vif Protein counteracts A3G by inducing its proteasomal degradation. Thus, the Vif–A3G axis is a potential therapeutic target. To identify compounds that inhibit Vif:A3G interaction, a 307,520 compound library was tested in a TR-FRET screen. Two identified compounds, redoxal and lomofungin, inhibited HIV-1 replication in peripheral blood mononuclear cells. Lomofungin activity was linked to A3G, but not pursued further due to cytotoxicity. Redoxal displayed A3G-dependent restriction, inhibiting viral replication by stabilizing A3G Protein levels and increasing A3G in virions. A3G-independent activity was also detected. Treatment with uridine or orotate, intermediates of pyrimidine synthesis, diminished redoxal-induced stabilization of A3G and antiviral activity. These results identify redoxal as an inhibitor of HIV-1 replication and suggest its ability to inhibit pyrimidine biosynthesis suppresses viral replication by augmenting A3G antiviral activity.
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redoxal an inhibitor of de novo pyrimidine biosynthesis augments apobec3g antiviral activity against human immunodeficiency virus type 1
Virology, 2015Co-Authors: Erez Pery, Ann M Sheehy, Vikas Misra, Marie K Mankowski, Lynn Rasmussen, Miranda N Nebane, Lucile E White, Roger G Ptak, Dana GabuzdaAbstract:Abstract APOBEC3G (A3G) is a cytidine deaminase that restricts HIV-1 replication by inducing G-to-A hypermutation in viral DNA; deamination-independent mechanisms are also implicated. HIV-1 Vif Protein counteracts A3G by inducing its proteasomal degradation. Thus, the Vif–A3G axis is a potential therapeutic target. To identify compounds that inhibit Vif:A3G interaction, a 307,520 compound library was tested in a TR-FRET screen. Two identified compounds, redoxal and lomofungin, inhibited HIV-1 replication in peripheral blood mononuclear cells. Lomofungin activity was linked to A3G, but not pursued further due to cytotoxicity. Redoxal displayed A3G-dependent restriction, inhibiting viral replication by stabilizing A3G Protein levels and increasing A3G in virions. A3G-independent activity was also detected. Treatment with uridine or orotate, intermediates of pyrimidine synthesis, diminished redoxal-induced stabilization of A3G and antiviral activity. These results identify redoxal as an inhibitor of HIV-1 replication and suggest its ability to inhibit pyrimidine biosynthesis suppresses viral replication by augmenting A3G antiviral activity.
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the hiv 1 Vif Protein mediates degradation of vpr and reduces vpr induced cell cycle arrest
DNA and Cell Biology, 2008Co-Authors: Jiangfang Wang, Dana Gabuzda, Jason M Shackelford, Nithianandan Selliah, Debra K Shivers, Eduardo Oneill, Victor J Garcia, Karuppiah Muthumani, David B Weiner, Terri H FinkelAbstract:Prior work has implicated viral Protein R (Vpr) in the arrest of human immunodeficiency virus type 1 (HIV-1)-infected cells in the G2 phase of the cell cycle, associated with increased viral replication and host cell apoptosis. We and others have recently shown that virion infectivity factor (Vif ) also plays a role in the G2 arrest of HIV-1-infected cells. Here, we demonstrate that, paradoxically, at early time points postinfection, Vif expression blocks Vpr-mediated G2 arrest, while deletion of Vif from the HIV-1 genome leads to a marked increase in G2 arrest of infected CD4 T-cells. Consistent with this increased G2 arrest, T-cells infected with Vif-deleted HIV-1 express higher levels of Vpr Protein than cells infected with wild-type virus. Further, expression of exogenous Vif inhibits the expression of Vpr, associated with a decrease in G2 arrest of both infected and transfected cells. Treatment with the proteasome inhibitor MG132 increases Vpr Protein expression and G2 arrest in wild-type, but not Vif-deleted, NL4-3-infected cells, and in cells cotransfected with Vif and Vpr. In addition, Vpr coimmunoprecipitates with Vif in cotransfected cells in the presence of MG132. This suggests that inhibition of Vpr by Vif is mediated at least in part by proteasomal degradation, similar to Vif-induced degradation of APOBEC3G. Together, these data show that Vif mediates the degradation of Vpr and modulates Vpr-induced G2 arrest in HIV-1-infected T-cells.
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Functional neutralization of HIV-1 Vif Protein by intracellular immunization inhibits reverse transcription and viral replication.
The Journal of biological chemistry, 2002Co-Authors: João Gonçalves, Dana Gabuzda, Frederico Aires Da Silva, Acilino Freitas-vieira, Mariana Santa-marta, Rui Malhó, Xiaoyu Yang, Carlos F. BarbasAbstract:Human immunodeficiency virus type 1 (HIV-1)-encoded Vif Protein is important for viral replication and infectivity. Vif is a cytoplasmic Protein that acts during virus assembly by an unknown mechanism, enhancing viral infectivity. The action of Vif in producer cells is essential for the completion of proviral DNA synthesis following virus entry. Therefore, Vif is considered to be an important alternative therapeutic target for inhibition of viral infectivity at the level of viral assembly and reverse transcription. To gain insight into this process, we developed a Vif-specific single-chain antibody and expressed it intracellularly in the cytoplasm. This intrabody efficiently bound Vif Protein and neutralized its infectivity-enhancing function. Intrabody-expressing cells were shown to be highly refractory to challenge with different strains of HIV-1 and HIV-1-infected cells. Inhibition of Vif by intrabody expression in the donor cell produced viral particles that do not complete reverse transcription in the recipient cell. The anti-Vif scFv was shown to be specific for Vif Protein because its function was observed only in nonpermissive cells (H9, CEM, and U38). Moreover, transduction of peripheral blood mononuclear cells with an HIV-derived retroviral vector expressing Vif intrabody was shown to confer resistance to laboratory-adapted and primary HIV strains. This study provides biochemical evidence for the role of Vif in the HIV-1 lifecycle and validates Vif as a target for the control of HIV-1 infection.
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Mitogen-activated Protein Kinase Phosphorylates and Regulates the HIV-1 Vif Protein
The Journal of biological chemistry, 1998Co-Authors: Xiaoyu Yang, Dana GabuzdaAbstract:Abstract The human immunodeficiency virus type 1 (HIV-1) Vif Protein plays a critical role in virus replication and infectivity. Here we show that Vif is phosphorylated and regulated by p44/42 mitogen-activated Protein kinase (MAPK). Vif phosphorylation by MAPK was demonstrated in vitro as well as in vivoand was shown to occur on serine and threonine residues. Two-dimensional tryptic phosphopeptide mapping indicated that Vif is phosphorylated by MAPK on the same sites in vitro andin vivo. Radioactive peptide sequencing identified two phosphorylation sites, Thr96 and Ser165. These phosphorylation sites do not correspond to the known optimum consensus sequences for phosphorylation by MAPK (PX(S/T)P) nor to the minimum consensus sequence ((S/T)P), indicating that MAPK can phosphorylate Proteins at sites other than those containing the PX(S/T)P or (S/T)P motifs. Synthetic Vif peptides corresponding to the local sequences of the phosphorylation sites were not phosphorylated by MAPK, suggesting that recognition of these sites by MAPK is likely to require structural determinants outside the phosphorylation site. Mutations of the Thr96 site, which is conserved among Vif sequences from HIV-1, HIV-2, and SIV, resulted in significant loss of Vif activity and inhibition of HIV-1 replication. These results suggest that MAPK plays a direct role in regulating HIV-1 replication and infectivity by phosphorylating Vif and identify a novel mechanism for activation of HIV-1 replication by mitogens and other extracellular stimuli.
U Wieland - One of the best experts on this subject based on the ideXlab platform.
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Unimpaired function of a naturally occurring C terminally truncated Vif gene product of human immunodeficiency virus type 1.
The Journal of general virology, 1996Co-Authors: C Ochsenbauer, V Bosch, I Oelze, U WielandAbstract:In approximate 10 percent of natural human immunodeficiency virus 1 (HIV-1) Vif gene populations, sequences of shortened Vif open reading frames with premature stop codons have been found. Here we report the functional analysis of two patient-derived Vif genes. Vif45-2 encodes a C terminally truncated Vif Protein of only 173 instead of 192 amino acids and additionally contains several rare amino acid substitutions which are in part shared by VifA65-5. HIV-1 pNL4-3-derived recombinant A45-2 and A65-5 virions were fully infectious in H9 cells and human PBMC, both known to be non-permissive for Vif-defective HIV-1. Furthermore, A45-2 virions produced in primary human monocyte-derived macrophages were infectious for MT-4 cells. This study unequivocally demonstrates that the C-terminal region (19 amino acids) of the Vif Protein is dispensable for Vif function in the in vitro cell culture systems employed. Additionally, we investigated whether the Vif Protein might be phosphorylated in vivo and obtained no evidence for this.
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Prevalence of antibodies to recombinant virion infectivity factor in the sera of prospectively studied patients with HIV-1 infection
Journal of medical virology, 1992Co-Authors: S. Schwander, R. W. Braun, J. E. Kühn, Frank T. Hufert, P. Kern, M. Dietrich, U WielandAbstract:Two hundred twenty-four sera were collected from 34 HIV-1 infected patients during an observation period of up to 4.5 years (109 patient years of observation). The sera were tested for the presence of antibodies against the HIV-1 virion infectivity factor (Vif) Protein. Thirty sera from 6 HIV-1 seronegative individuals served as negative controls. The sera were immunoblotted against a recombinant, prokaryotically expressed Vif Protein. The prevalence of anti-Vif antibodies increased significantly with progression of the disease from 18% to 81% (P less than 0.0001) which suggests a possible role of Vif in HIV-1 replication and pathogenicity.
Klaus Strebel - One of the best experts on this subject based on the ideXlab platform.
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Production of infectious human immunodeficiency virus type 1 does not require depletion of APOBEC3G from virus-producing cells.
Retrovirology, 2004Co-Authors: Sandra Kao, Mohammad Ahmed Khan, Eri Miyagi, Hiroaki Takeuchi, Sandrine Opi, Ritu Goila-gaur, Klaus StrebelAbstract:Background The human immunodeficiency virus Vif Protein overcomes the inhibitory activity of the APOBEC3G cytidine deaminase by prohibiting its packaging into virions. Inhibition of APOBEC3G encapsidation is paralleled by a reduction of its intracellular level presumably caused by the Vif-induced proteasome-dependent degradation of APOBEC3G.
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Intravirion processing of the human immunodeficiency virus type 1 Vif Protein by the viral protease may be correlated with Vif function.
Journal of virology, 2002Co-Authors: Mohammad Ahmed Khan, Claudia Aberham, Sandra Kao, Hirofumi Akari, David A. Davis, Alicia Buckler-white, Klaus StrebelAbstract:The human immunodeficiency virus type 1 (HIV-1) Vif Protein is specifically packaged into virus particles through an interaction with viral genomic RNA in which it associates with the viral nucleoProtein complex. We now demonstrate for the first time that virus-associated Vif is subject to proteolytic processing by the viral protease (Pr). Pr-dependent processing of Vif was observed both in vivo and in vitro. In vivo processing of Vif was cell type independent and evident by the appearance of a 7-kDa processing product, which was restricted to cell-free virus preparations. Processing of Vif required an active viral Pr and was sensitive to Pr inhibitors such as ritonavir. The processing site in Vif was characterized both in vivo and in vitro and mapped to Ala(150). Interestingly, the Vif processing site is located in a domain that is highly conserved among HIV-1, HIV-2, and simian immunodeficiency virus Vif isolates. Mutations at or near the processing site did not affect Protein stability or packaging efficiency but had dramatic effects on Vif processing. In general, mutations that markedly increased or decreased the sensitivity of Vif to proteolytic processing severely impaired or completely abolished Vif function. In contrast, mutations at the same site that had little or no effect on processing efficiency also did not influence Vif function. None of the mutants affected the ability of the virus to replicate in permissive cell lines. Our data suggest that mutations in Vif that cause a profound change in the sensitivity to Pr-dependent processing also severely impaired Vif function, suggesting that intravirion processing of Vif is important for the production of infectious viruses.
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human immunodeficiency virus type 1 Vif Protein is packaged into the nucleoProtein complex through an interaction with viral genomic rna
Journal of Virology, 2001Co-Authors: Mohammad Ahmed Khan, Claudia Aberham, Sandra Kao, Hirofumi Akari, Robert J Gorelick, Stephan Bour, Klaus StrebelAbstract:The human immunodeficiency virus type 1 (HIV-1) Vif Protein plays a critical role in the production of infectious virions. Previous studies have demonstrated the presence of small amounts of Vif in virus particles. However, Vif packaging was assumed to be nonspecific, and its functional significance has been questioned. We now report that packaging of Vif is dependent on the packaging of viral genomic RNA in both permissive and restrictive HIV-1 target cells. Mutations in the nucleocapsid zinc finger domains that abrogate packaging of viral genomic RNA abolished packaging of Vif. Additionally, an RNA packaging-defective virus exhibited significantly reduced packaging of Vif. Finally, deletion of a putative RNA-interacting domain in Vif abolished packaging of Vif into virions. Virion-associated Vif was resistant to detergent extraction and copurified with components of the viral nucleoProtein complex and functional reverse transcription complexes. Thus, Vif is specifically packaged into virions as a component of the viral nucleoProtein complex. Our data suggest that the specific association of Vif with the viral nucleoProtein complex might be functionally significant and could be a critical requirement for infectivity of viruses produced from restrictive host cells.
Bryan R. Cullen - One of the best experts on this subject based on the ideXlab platform.
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specific packaging of apobec3g into hiv 1 virions is mediated by the nucleocapsid domain of the gag polyProtein precursor
Virology, 2004Co-Authors: Alexandra Schafer, Hal P Bogerd, Bryan R. CullenAbstract:Abstract In cells infected by HIV-1 mutants lacking a functional Vif Protein, APOBEC3G is specifically packaged into progeny virions and then interferes with the process of virus infection. Here, we show that incorporation of APOBEC3G into HIV-1 virions is mediated by the specific interaction of APOBEC3G with the carboxy-terminal nucleocapsid/p6 domain of the Gag polyProtein precursor. As a result, HIV-1 virus-like particles that lack the nucleocapsid domain fail to package APOBEC3G. Surprisingly, RNA was also found to be essential for formation of the nucleocapsid–APOBEC3G complex in vitro, thus raising the possibility that RNA may form a bridge between these two Proteins.
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a second human antiretroviral factor apobec3f is suppressed by the hiv 1 and hiv 2 Vif Proteins
The EMBO Journal, 2004Co-Authors: Heather L Wiegand, Bryan R. Cullen, Hal P Bogerd, Brian P DoehleAbstract:The HIV-1 Vif Protein suppresses the inhibition of viral replication caused by the human antiretroviral factor APOBEC3G. As a result, HIV-1 mutants that do not express the Vif Protein are replication incompetent in 'nonpermissive' cells, such as primary T cells and the T-cell line CEM, that express APOBEC3G. In contrast, Vif-defective HIV-1 replicates effectively in 'permissive' cell lines, such as a derivative of CEM termed CEM-SS, that do not express APOBEC3G. Here, we show that a second human Protein, APOBEC3F, is also specifically packaged into HIV-1 virions and inhibits their infectivity. APOBEC3F binds the HIV-1 Vif Protein specifically and Vif suppresses both the inhibition of virus infectivity caused by APOBEC3F and virion incorporation of APOBEC3F. Surprisingly, APOBEC3F and APOBEC3G are extensively coexpressed in nonpermissive human cells, including primary lymphocytes and the cell line CEM, where they form heterodimers. In contrast, both genes are quiescent in the permissive CEM derivative CEM-SS. Together, these data argue that HIV-1 Vif has evolved to suppress at least two distinct but related human antiretroviral DNA-editing enzymes.
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A second human antiretroviral factor, APOBEC3F, is suppressed by the HIV‐1 and HIV‐2 Vif Proteins
The EMBO journal, 2004Co-Authors: Heather L Wiegand, Hal P Bogerd, Brian P Doehle, Bryan R. CullenAbstract:The HIV-1 Vif Protein suppresses the inhibition of viral replication caused by the human antiretroviral factor APOBEC3G. As a result, HIV-1 mutants that do not express the Vif Protein are replication incompetent in 'nonpermissive' cells, such as primary T cells and the T-cell line CEM, that express APOBEC3G. In contrast, Vif-defective HIV-1 replicates effectively in 'permissive' cell lines, such as a derivative of CEM termed CEM-SS, that do not express APOBEC3G. Here, we show that a second human Protein, APOBEC3F, is also specifically packaged into HIV-1 virions and inhibits their infectivity. APOBEC3F binds the HIV-1 Vif Protein specifically and Vif suppresses both the inhibition of virus infectivity caused by APOBEC3F and virion incorporation of APOBEC3F. Surprisingly, APOBEC3F and APOBEC3G are extensively coexpressed in nonpermissive human cells, including primary lymphocytes and the cell line CEM, where they form heterodimers. In contrast, both genes are quiescent in the permissive CEM derivative CEM-SS. Together, these data argue that HIV-1 Vif has evolved to suppress at least two distinct but related human antiretroviral DNA-editing enzymes.
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a single amino acid difference in the host apobec3g Protein controls the primate species specificity of hiv type 1 virion infectivity factor
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Hal P Bogerd, Heather L Wiegand, Brian P Doehle, Bryan R. CullenAbstract:The HIV type 1 (HIV-1) virion infectivity factor (Vif) Protein blocks the action of the host defense factor APOBEC3G in human cells, thereby allowing release of infectious virions, but fails to inhibit similar APOBEC3G Proteins present in some simian cells. Conversely, the Vif Protein encoded by the African green monkey (agm) simian immunodeficiency virus (SIV) can block agm APOBEC3G function but fails to inhibit human APOBEC3G. This difference plays a key role in determining the primate species tropism of HIV-1 and SIV agm. Here, we demonstrate that a single APOBEC3G residue, which is an aspartic acid in human APOBEC3G and a lysine in agm APOBEC3G, controls the ability of the HIV-1 Vif Protein to bind and inactivate these host defense factors. These data identify a critical charged residue that plays a key role in mediating the formation of the distinct Vif:APOBEC3G complexes formed in human and simian cells. Moreover, these results suggest that the biological barrier preventing the entry of additional SIV into the human population as zoonotic infections is potentially quite fragile.