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D'Orso I. The HIV-1 Transcriptional Program: From Initiation to Elongation Control. J Mol Biol 2024:168690. [PMID: 38936695 DOI: 10.1016/j.jmb.2024.168690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 06/20/2024] [Accepted: 06/21/2024] [Indexed: 06/29/2024]
Abstract
A large body of work in the last four decades has revealed the key pillars of HIV-1 transcription control at the initiation and elongation steps. Here, I provide a recount of this collective knowledge starting with the genomic elements (DNA and nascent TAR RNA stem-loop) and transcription factors (cellular and the viral transactivator Tat), and later transitioning to the assembly and regulation of transcription initiation and elongation complexes, and the role of chromatin structure. Compelling evidence support a core HIV-1 transcriptional program regulated by the sequential and concerted action of cellular transcription factors and Tat to promote initiation and sustain elongation, highlighting the efficiency of a small virus to take over its host to produce the high levels of transcription required for viral replication. I summarize new advances including the use of CRISPR-Cas9, genetic tools for acute factor depletion, and imaging to study transcriptional dynamics, bursting and the progression through the multiple phases of the transcriptional cycle. Finally, I describe current challenges to future major advances and discuss areas that deserve more attention to both bolster our basic knowledge of the core HIV-1 transcriptional program and open up new therapeutic opportunities.
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Affiliation(s)
- Iván D'Orso
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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2
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Rausch JW, Parvez S, Pathak S, Capoferri AA, Kearney MF. HIV Expression in Infected T Cell Clones. Viruses 2024; 16:108. [PMID: 38257808 PMCID: PMC10820123 DOI: 10.3390/v16010108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 01/04/2024] [Accepted: 01/06/2024] [Indexed: 01/24/2024] Open
Abstract
The principal barrier to an HIV-1 cure is the persistence of infected cells harboring replication-competent proviruses despite antiretroviral therapy (ART). HIV-1 transcriptional suppression, referred to as viral latency, is foremost among persistence determinants, as it allows infected cells to evade the cytopathic effects of virion production and killing by cytotoxic T lymphocytes (CTL) and other immune factors. HIV-1 persistence is also governed by cellular proliferation, an innate and essential capacity of CD4+ T cells that both sustains cell populations over time and enables a robust directed response to immunological threats. However, when HIV-1 infects CD4+ T cells, this capacity for proliferation can enable surreptitious HIV-1 propagation without the deleterious effects of viral gene expression in latently infected cells. Over time on ART, the HIV-1 reservoir is shaped by both persistence determinants, with selective forces most often favoring clonally expanded infected cell populations harboring transcriptionally quiescent proviruses. Moreover, if HIV latency is incomplete or sporadically reversed in clonal infected cell populations that are replenished faster than they are depleted, such populations could both persist indefinitely and contribute to low-level persistent viremia during ART and viremic rebound if treatment is withdrawn. In this review, select genetic, epigenetic, cellular, and immunological determinants of viral transcriptional suppression and clonal expansion of HIV-1 reservoir T cells, interdependencies among these determinants, and implications for HIV-1 persistence will be presented and discussed.
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Affiliation(s)
- Jason W. Rausch
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA; (S.P.); (S.P.); (A.A.C.); (M.F.K.)
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3
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Roebuck KA, Saifuddin M. Regulation of HIV-1 transcription. Gene Expr 2018; 8:67-84. [PMID: 10551796 PMCID: PMC6157391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Human immunodeficiency virus type-1 (HIV-1) is a highly pathogenic lentivirus that requires transcription of its provirus genome for completion of the viral life cycle and the production of progeny virions. Since the first genetic analysis of HIV-1 in 1985, much has been learned about the transcriptional regulation of the HIV-1 genome in infected cells. It has been demonstrated that HIV-1 transcription depends on a varied and complex interaction of host cell transcription factors with the viral long terminal repeat (LTR) promoter. The regulatory elements within the LTR interact with constitutive and inducible transcription factors to direct the assembly of a stable transcription complex that stimulates multiple rounds of transcription by RNA polymerase II (RNAPII). However, the majority of these transcripts terminate prematurely in the absence of the virally encoded trans-activator protein Tat, which stimulates HIV-1 transcription elongation by interacting with a stem-loop RNA element (TAR) formed at the extreme 5' end of all viral transcripts. The Tat-TAR interaction recruits a cellular kinase into the initiation-elongation complex that alters the elongation properties of RNAPII during its transit through TAR. This review summarizes our current knowledge and understanding of the regulation of HIV-1 transcription in infected cells and highlights the important contributions human lentivirus gene regulation has made to our general understanding of the transcription process.
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Affiliation(s)
- K A Roebuck
- Department of Immunology/Microbiology, Rush Presbyterian St. Luke's Medical Center, Chicago, IL 60612, USA.
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Peddi SR, Sivan SK, Manga V. Molecular dynamics and MM/GBSA-integrated protocol probing the correlation between biological activities and binding free energies of HIV-1 TAR RNA inhibitors. J Biomol Struct Dyn 2017; 36:486-503. [PMID: 28081678 DOI: 10.1080/07391102.2017.1281762] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The interaction of HIV-1 transactivator protein Tat with its cognate transactivation response (TAR) RNA has emerged as a promising target for developing antiviral compounds and treating HIV infection, since it is a crucial step for efficient transcription and replication. In the present study, molecular dynamics (MD) simulations and MM/GBSA calculations have been performed on a series of neamine derivatives in order to estimate appropriate MD simulation time for acceptable correlation between ΔGbind and experimental pIC50 values. Initially, all inhibitors were docked into the active site of HIV-1 TAR RNA. Later to explore various conformations and examine the docking results, MD simulations were carried out. Finally, binding free energies were calculated using MM/GBSA method and were correlated with experimental pIC50 values at different time scales (0-1 to 0-10 ns). From this study, it is clear that in case of neamine derivatives as simulation time increased the correlation between binding free energy and experimental pIC50 values increased correspondingly. Therefore, the binding energies which can be interpreted at longer simulation times can be used to predict the bioactivity of new neamine derivatives. Moreover, in this work, we have identified some plausible critical nucleotide interactions with neamine derivatives that are responsible for potent inhibitory activity. Furthermore, we also provide some insights into a new class of oxadiazole-based back bone cyclic peptides designed by incorporating the structural features of neamine derivatives. On the whole, this approach can provide a valuable guidance for designing new potent inhibitors and modify the existing compounds targeting HIV-1 TAR RNA.
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Affiliation(s)
- Saikiran Reddy Peddi
- a Molecular Modeling and Medicinal Chemistry Group, Department of Chemistry , University College of Science, Osmania University , Hyderabad 500 007 , Telangana , India
| | - Sree Kanth Sivan
- b Department of Chemistry , Nizam College, Osmania University , Hyderabad 500 001 , Telangana , India
| | - Vijjulatha Manga
- a Molecular Modeling and Medicinal Chemistry Group, Department of Chemistry , University College of Science, Osmania University , Hyderabad 500 007 , Telangana , India
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Impact of viral activators and epigenetic regulators on HIV-1 LTRs containing naturally occurring single nucleotide polymorphisms. BIOMED RESEARCH INTERNATIONAL 2015; 2015:320642. [PMID: 25629043 PMCID: PMC4299542 DOI: 10.1155/2015/320642] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 09/29/2014] [Accepted: 10/14/2014] [Indexed: 12/17/2022]
Abstract
Following human immunodeficiency virus type 1 (HIV-1) integration into host cell DNA, the viral promoter can become transcriptionally silent in the absence of appropriate signals and factors. HIV-1 gene expression is dependent on regulatory elements contained within the long terminal repeat (LTR) that drive the synthesis of viral RNAs and proteins through interaction with multiple host and viral factors. Previous studies identified single nucleotide polymorphisms (SNPs) within CCAAT/enhancer binding protein (C/EBP) site I and Sp site III (3T, C-to-T change at position 3, and 5T, C-to-T change at position 5 of the binding site, respectively, when compared to the consensus B sequence) that are low affinity binding sites and correlate with more advanced stages of HIV-1 disease. Stably transfected cell lines containing the wild type, 3T, 5T, and 3T5T LTRs were developed utilizing bone marrow progenitor, T, and monocytic cell lines to explore the LTR phenotypes associated with these genotypic changes from an integrated chromatin-based microenvironment. Results suggest that in nonexpressing cell clones LTR-driven gene expression occurs in a SNP-specific manner in response to LTR activation or treatment with trichostatin A treatment, indicating a possible cell type and SNP-specific mechanism behind the epigenetic control of LTR activation.
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Li CH, Zuo ZC, Su JG, Xu XJ, Wang CX. The interactions and recognition of cyclic peptide mimetics of Tat with HIV-1 TAR RNA: a molecular dynamics simulation study. J Biomol Struct Dyn 2012; 31:276-87. [PMID: 22943434 DOI: 10.1080/07391102.2012.698248] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The interaction of HIV-1 trans-activator protein Tat with its cognate trans-activation response element (TAR) RNA is critical for viral transcription and replication. Therefore, it has long been considered as an attractive target for the development of antiviral compounds. Recently, the conformationally constrained cyclic peptide mimetics of Tat have been tested to be a promising family of lead peptides. Here, we focused on two representative cyclic peptides termed as L-22 and KP-Z-41, both of which exhibit excellent inhibitory potency against Tat and TAR interaction. By means of molecular dynamics simulations, we obtained a detailed picture of the interactions between them and HIV-1 TAR RNA. In results, it is found that the binding modes of the two cyclic peptides to TAR RNA are almost identical at or near the bulge regions, whereas the binding interfaces at the apical loop exhibit large conformational heterogeneity. In addition, it is revealed that electrostatic interaction energy contributes much more to KP-Z-41 complex formation than to L-22 complex, which is the main source of energy that results in a higher binding affinity of KP-Z-41 over-22 for TAR RNA. Furthermore, we identified a conserved motif RRK (Arg-Arg-Lys) that is shown to be essential for specific binding of this class of cyclic peptides to TAR RNA. This work can provide a useful insight into the design and modification of cyclic peptide inhibitors targeting the association of HIV-1 Tat and TAR RNA.
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Affiliation(s)
- Chun Hua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Pingleyuan 100, Chaoyang District, Beijing 100124, China.
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Kilareski EM, Shah S, Nonnemacher MR, Wigdahl B. Regulation of HIV-1 transcription in cells of the monocyte-macrophage lineage. Retrovirology 2009; 6:118. [PMID: 20030845 PMCID: PMC2805609 DOI: 10.1186/1742-4690-6-118] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 12/23/2009] [Indexed: 12/20/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) has been shown to replicate productively in cells of the monocyte-macrophage lineage, although replication occurs to a lesser extent than in infected T cells. As cells of the monocyte-macrophage lineage become differentiated and activated and subsequently travel to a variety of end organs, they become a source of infectious virus and secreted viral proteins and cellular products that likely initiate pathological consequences in a number of organ systems. During this process, alterations in a number of signaling pathways, including the level and functional properties of many cellular transcription factors, alter the course of HIV-1 long terminal repeat (LTR)-directed gene expression. This process ultimately results in events that contribute to the pathogenesis of HIV-1 infection. First, increased transcription leads to the upregulation of infectious virus production, and the increased production of viral proteins (gp120, Tat, Nef, and Vpr), which have additional activities as extracellular proteins. Increased viral production and the presence of toxic proteins lead to enhanced deregulation of cellular functions increasing the production of toxic cellular proteins and metabolites and the resulting organ-specific pathologic consequences such as neuroAIDS. This article reviews the structural and functional features of the cis-acting elements upstream and downstream of the transcriptional start site in the retroviral LTR. It also includes a discussion of the regulation of the retroviral LTR in the monocyte-macrophage lineage during virus infection of the bone marrow, the peripheral blood, the lymphoid tissues, and end organs such as the brain. The impact of genetic variation on LTR-directed transcription during the course of retrovirus disease is also reviewed.
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Affiliation(s)
- Evelyn M Kilareski
- Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Center for Molecular Therapeutics and Resistance, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA
| | - Sonia Shah
- Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Center for Molecular Therapeutics and Resistance, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA
| | - Michael R Nonnemacher
- Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Center for Molecular Therapeutics and Resistance, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA
| | - Brian Wigdahl
- Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Center for Molecular Therapeutics and Resistance, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N 15th St, Philadelphia, Pennsylvania 19102, USA
- Department of Microbiology and Immunology, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, Pennsylvania 19129, USA
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Wang X, Yamataka K, Okamoto M, Ikeda S, Baba M. Potent and selective inhibition of Tat-dependent HIV-1 replication in chronically infected cells by a novel naphthalene derivative JTK-101. Antivir Chem Chemother 2008; 18:201-11. [PMID: 17907378 DOI: 10.1177/095632020701800404] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In search for effective human immunodeficiency virus type 1 (HIV-1) transcription inhibitors, we have evaluated more than 100,000 compounds for their inhibitory effects on HIV-1 long terminal repeat (LTR)-driven reporter gene expression, and identified a novel naphthalene derivative, JTK-101. This compound could suppress tumour necrosis factor (TNF)-alpha-induced HIV-1 production in latently infected OM-10.1 cells at nanomolar concentrations. JTK-101 could also potently inhibit constitutive HIV-1 production in MOTL-4/IIIB. However, the antiviral activity of JTK-101 was found to be much weaker in acutely infected cells and the chronically infected cells U937/IIIB cells than in OM-10.1 and MOLT-4/IIIB cells. JTK-101 selectively suppressed TNF-alpha-induced HIV-1 mRNA synthesis in OM-10.1 cells in a dose-dependent fashion. JTK-101 modestly inhibited TNF-alpha-induced HIV-1 LTR-driven reporter gene expression, but potently inhibited Tat-induced gene expression. Immunoblot analysis revealed that low-level expression of the Tat cofactors CDK9 and cyclin T1 might contribute to the diminished antiviral activity in U937/IIIB cells. Furthermore, JTK-101 could not inhibit HIV-1 replication in chronically infected monocytes/macrophages, in which CDK9 and cyclin T1 were undetectable. These results suggest that JTK-101 exerts its anti-HIV-1 activity through the inhibition of known or unknown Tat cofactors, presumably CDK9/cyclin T1.
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Affiliation(s)
- Xin Wang
- Division of Antiviral Chemotherapy, Center for Chronic Viral Diseases, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
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Boven LA, Noorbakhsh F, Bouma G, van der Zee R, Vargas DL, Pardo C, McArthur JC, Nottet HSLM, Power C. Brain-derived human immunodeficiency virus-1 Tat exerts differential effects on LTR transactivation and neuroimmune activation. J Neurovirol 2007; 13:173-84. [PMID: 17505986 DOI: 10.1080/13550280701258399] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Molecular diversity within brain-derived HIV-1 sequences is highly variable depending on the individual gene examined and the neurological status of the patient. Herein, we examined different brain-derived human immunodeficiency virus (HIV)-1 tat sequences in terms of their effects on LTR transactivation and host gene induction in neural cells. Astrocytic and monocytoid cells co-transfected with prototypic tat clones derived from non-demented (ND) (n = 3) and demented (HAD) (n = 3) AIDS patients and different HIV-LTR constructs revealed that LTR transactivation mediated by tat clones derived from HAD patients was decreased (p < 0.05). A Tat-derived peptide containing the amino acid 24-38 domain from a ND clone caused down-regulation of the LTR transactivation (p < 0.05) in contrast to peptides from other Tat regions derived from HAD and ND tat clones. Both brain-derived HAD and ND tat constructs were able to induce the host immune genes, MCP-1 and IL-1beta. Microarray analysis revealed several host genes were selectively upregulated by a HAD-derived tat clone including an enzyme mediating heparan sulphate synthesis, HS3ST3B1 (p < 0.05), which was also found to be increased in the brains of patients with HAD. Expression of the pro-apoptotic gene, PDCD7, was reduced in cells transfected with the HAD-derived tat clone and moreover, this gene was also suppressed in monocytoid cells infected with a neurotropic HIV-1 strain. Thus, mutations within the HIV-1 tat gene may exert pathogenic effects contributing to the development of HAD, which are independent of its effects on LTR transactivation.
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Affiliation(s)
- Leonie A Boven
- Department of Immunology, Erasmus Medical Center, Rotterdam, The Netherlands
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Gorrill T, Feliciano M, Mukerjee R, Sawaya BE, Khalili K, White MK. Activation of early gene transcription in polyomavirus BK by human immunodeficiency virus type 1 Tat. J Gen Virol 2006; 87:1557-1566. [PMID: 16690919 DOI: 10.1099/vir.0.81569-0] [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] [Indexed: 11/18/2022] Open
Abstract
Polyomavirus BK (BKV) is a serious problem for immunocompromised patients, where latent virus can enter into the lytic cycle causing cytolytic destruction of host cells. BKV infects >80% of the population worldwide during childhood and then remains in a latent state in the kidney. In the context of immunosuppression in kidney transplant patients, reactivation of the viral early promoter (BKV(E)) results in production of T antigen, enabling virus replication and transition from latency to the lytic phase, causing polyomavirus-associated nephropathy. Reactivation of BKV can also cause complications such as nephritis, atypical retinitis and haemorrhagic cystitis in AIDS patients. Here, the effects of human immunodeficiency virus type 1 (HIV-1) proteins Tat and Vpr on BKV transcription were investigated and it was demonstrated that Tat dramatically stimulated BKV(E). Site-directed mutagenesis analysis of potential Tat-responsive transcriptional motifs complemented by an electrophoretic mobility shift assay (EMSA) showed that Tat activated BKV(E) by inducing binding of the NF-kappaB p65 subunit to a kappaB motif near the 3' end of BKV(E). In addition, a sequence within the 5' UTR of BKV(E) transcripts (BKV(E)-TAR) was identified that is identical to the HIV-1 transactivation response (TAR) element. The BKV(E)-TAR sequence bound TAT in RNA EMSA assays and deletion of the BKV(E)-TAR sequence eliminated Tat transactivation of BKV(E) transcription. Thus, Tat positively affected BKV(E) transcription by a dual mechanism and this may be important in diseases involving BKV reactivation in AIDS patients.
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Affiliation(s)
- Timothy Gorrill
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
| | - Mariha Feliciano
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
| | - Ruma Mukerjee
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
| | - Bassel E Sawaya
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
| | - Kamel Khalili
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
| | - Martyn K White
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA
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Hidalgo-Estévez AM, González E, Punzón C, Fresno M. Human immunodeficiency virus type 1 Tat increases cooperation between AP-1 and NFAT transcription factors in T cells. J Gen Virol 2006; 87:1603-1612. [PMID: 16690925 DOI: 10.1099/vir.0.81637-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) Tat affects cellular gene expression through modulation of the activity of different transcription factors. Here, the role of Tat in the cooperation between nuclear factor of activated T cells (NFAT) and activator protein 1 (AP-1) transcription factors was investigated. Constitutive or transient Tat expression in Jurkat T cells enhanced cooperative NFAT/AP-1- but not AP-1-dependent transcription independent of its ability to transactivate the HIV-1 LTR. The enhancing effect of Tat took place after nuclear translocation of NFAT. Furthermore, transactivation of an NFAT/AP-1 reporter by transfection of NFAT and c-Jun was strongly enhanced by simultaneous Tat transfection. Moreover, intracellular Tat expression increased the binding of NFAT/AP-1 complexes to the interleukin 2 promoter without significantly altering NFAT- and AP-1-independent binding. HIV-1 Tat interacted with NFAT but not c-Jun. These results indicate that Tat interacts with NFAT, affecting its cooperation with AP-1, without altering independent binding of these transcription factors to DNA.
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Affiliation(s)
- Alicia M Hidalgo-Estévez
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Esther González
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Carmen Punzón
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
| | - Manuel Fresno
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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White MK, Gorrill TS, Khalili K. Reciprocal transactivation between HIV-1 and other human viruses. Virology 2006; 352:1-13. [PMID: 16725168 DOI: 10.1016/j.virol.2006.04.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 03/14/2006] [Accepted: 04/06/2006] [Indexed: 01/08/2023]
Abstract
A variety of rare clinical syndromes are seen with strikingly increased prevalence in HIV-1-infected individuals, many with underlying viral etiologies. The emergence of these diseases in AIDS reflects a reduction in the ability of the immune system to mount an adequate defense against viruses in general due to the damage inflicted to the immune system by HIV-1 infection. However, in many cases, it has been found that HIV-1 can enhance the level of expression and hence the life cycle of other viruses independently of immunosuppression through specific interactions with the viruses. This can occur either directly by HIV-1 proteins such as Tat enhancing the activity of heterologous viral promoters, and/or indirectly by HIV-1 inducing the expression of cytokines and activation of their downstream signaling that eventually promotes the multiplication of the other virus. In a reciprocal manner, the effects of other viruses can enhance the pathogenicity of HIV-1 infection in individuals with AIDS through stimulation of the HIV-1 promoter activity and genome expression. The purpose of this review is to examine the cross-interactions between these viruses and HIV-1.
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Affiliation(s)
- Martyn K White
- Center for Neurovirology, Department of Neuroscience, Temple University School of Medicine, 1900 North 12th Street, 015-96, Room 203, Philadelphia, PA 19122, USA.
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Montano M, Rarick M, Sebastiani P, Brinkmann P, Skefos J, Ericksen R. HIV-1 burden influences host response to co-infection with Neisseria gonorrhoeae in vitro. Int Immunol 2005; 18:125-37. [PMID: 16352629 DOI: 10.1093/intimm/dxh355] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
There is considerable evidence that co-infection with the sexually transmitted pathogen Neisseria gonorrhoeae (Gc) can increase the likelihood of both transmitting and acquiring HIV-1 worldwide. However, less information is available on how host immune response to co-infection differs with immune response to HIV-1 infection alone. To evaluate HIV-1 burden effects on host response to co-infection with Gc, we performed gene-expression profiling of human PBMCs infected over a broad range of viral titers (HIV-1 series) and upon exposure to a single infectious dose of Gc (HIV-1/Gc series). The transcriptional profiles differed substantially between each series (P < 0.0001). Major shifts in the transcriptional landscape were identified in contour plots based on fold stimulation and hierarchical clustering. Prominent regions of transcriptional activity were evaluated for statistical enrichment to identify up-regulated pathways associated with immune response, infection and T-cell stimulation. Notably, gene enrichment was dependent on HIV-1 burden and shifted during co-infection to reveal a disproportionate effect on lymphocyte signaling, apoptosis and proteasome activity. Further evaluation of these findings may help to better understand the role of viral burden in defining cellular contribution to host immune response upon co-infection with secondary sexually transmitted pathogens.
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Affiliation(s)
- Monty Montano
- Department of Medicine, Section of Infectious Diseases, Center for HIV-1/AIDS Care and Research, Boston University School of Medicine, USA
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14
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Biswas DK, Singh S, Shi Q, Pardee AB, Iglehart JD. Crossroads of estrogen receptor and NF-kappaB signaling. Sci Signal 2005; 2005:pe27. [PMID: 15956359 DOI: 10.1126/stke.2882005pe27] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Cellular homeostasis in higher organisms is maintained by balancing cell growth, differentiation, and death. Two important systems that transmit extracellular signals into the machinery of the cell nucleus are the signaling pathways that activate nuclear factor kappaB (NF-kappaB) and estrogen receptor (ER). These two transcription factors induce expression of genes that control cell fates, including proliferation and cell death (apoptosis). However, ER has anti-inflammatory effects, whereas activated NF-kappaB initiates and maintains cellular inflammatory responses. Recent investigations elucidated a nonclassical and nongenomic effect of ER: inhibition of NF-kappaB activation and the inflammatory response. In breast cancer, antiestrogen therapy might cause reactivation of NF-kappaB, potentially rerouting a proliferative signal to breast cancer cells and contributing to hormone resistance. Thus, ER ligands that selectively block NF-kappaB activation could provide specific potential therapy for hormone-resistant ER-positive breast cancers.
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Affiliation(s)
- Debajit K Biswas
- Department of Cancer Biology, Dana-Farber Cancer Institute, Brigham and Women's Hospital, Boston, MA 02115, USA.
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15
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Biswas DK, Shi Q, Baily S, Strickland I, Ghosh S, Pardee AB, Iglehart JD. NF-kappa B activation in human breast cancer specimens and its role in cell proliferation and apoptosis. Proc Natl Acad Sci U S A 2004; 101:10137-42. [PMID: 15220474 PMCID: PMC454178 DOI: 10.1073/pnas.0403621101] [Citation(s) in RCA: 352] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lack of molecular targets in estrogen receptor-negative (ER-negative) breast cancer is a major therapeutic hurdle. We studied NF-kappa B activation in human breast tumors and in carcinoma cell lines. Activated NF-kappa B was detected predominantly in ER-negative vs. ER-positive breast tumors and mostly in ER-negative and ErbB2-positive tumors (86%). These in vivo results demonstrate association of activated NF-kappa B with a subgroup of human breast tumors and are consistent with previously reported in vitro observations using similar classes of human breast cancer cell lines. Finding such an association suggested functional and biological significance. Immunofluorescence demonstrated increased nuclear p65, a component of the active NF-kappa B complex, in cytokeratin 19 (CK19)-positive epithelial cells of ER-negative/ErbB2-positive tumor samples. In contrast, nuclear NF-kappa B was detected mostly in stroma of ER-negative and ErbB2-negative tumors, suggesting a role of activated NF-kappa B in intercellular signaling between epithelial and stromal cells in this type of breast cancers. To elucidate roles of activated NF-kappa B, we used an ER-negative and ErbB2-positive human breast tumor cell line (SKBr3). The polypeptide heregulin beta1 stimulated, and herceptin, the anti-ErbB2 antibody, inhibited, NF-kappa B activation in SKBr3 cells. The NF-kappa B essential modulator (NEMO)-binding domain (NBD) peptide, an established selective inhibitor of I kappa B-kinase (IKK), blocked heregulin-mediated activation of NF-kappa B and cell proliferation, and simultaneously induced apoptosis only in proliferating and not resting cells. These results substantiate the hypothesis that certain breast cancer cells rely on NF-kappa B for aberrant cell proliferation and simultaneously avoid apoptosis, thus implicating activated NF-kappa B as a therapeutic target for distinctive subclasses of ER-negative breast cancers.
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Affiliation(s)
- Debajit K Biswas
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
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16
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Rohr O, Marban C, Aunis D, Schaeffer E. Regulation of HIV-1 gene transcription: from lymphocytes to microglial cells. J Leukoc Biol 2003; 74:736-49. [PMID: 12960235 DOI: 10.1189/jlb.0403180] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Transcription is a crucial step for human immunodeficiency virus type 1 (HIV-1) expression in all infected host cells, from T lymphocytes, thymocytes, monocytes, macrophages, and dendritic cells in the immune system up to microglial cells in the central nervous system. To maximize its replication, HIV-1 adapts transcription of its integrated proviral genome by ideally exploiting the specific cellular environment and by forcing cellular stimulatory events and impairing transcriptional inhibition. Multiple cell type-specific interplays between cellular and viral factors perform the challenge for the virus to leave latency and actively replicate in a great diversity of cells, despite the variability of its long terminal repeat region in different HIV strains. Knowledge about the molecular mechanisms underlying transcriptional regulatory events helps in the search for therapeutic agents that target the step of transcription in anti-HIV strategies.
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Affiliation(s)
- Olivier Rohr
- Institut National de la Santé Recherche Médicale Unité, Strasbourg, France
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17
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Darbinian N, Sawaya BE, Khalili K, Jaffe N, Wortman B, Giordano A, Amini S. Functional interaction between cyclin T1/cdk9 and Puralpha determines the level of TNFalpha promoter activation by Tat in glial cells. J Neuroimmunol 2001; 121:3-11. [PMID: 11730934 DOI: 10.1016/s0165-5728(01)00372-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In addition to its stimulatory effect on transcription of the HIV-1 LTR, the early protein of HIV-1, Tat, exhibits detrimental effects on the CNS by deregulating the expression of several cytokines and immunomodulators including TNFalpha. Activation of the viral promoter by Tat requires several cellular proteins including cyclin T1 and its partner, cdk9, which upon association with the TAR sequence of the LTR, forms a complex that enhances the activity of RNA polymerase II. Here, we examined the involvement of cyclin T1/cdk9 in Tat-mediated transcriptional activation of the TNFalpha promoter which has no TAR sequence. Results from transfection of human astrocytic cells revealed that both cyclin T1 and cdk9 stimulate the basal promoter activity of TNFalpha, although the level of such activation is decreased in the presence of Tat. Ectopic expression of Puralpha, a brain-derived regulatory protein which binds to Tat, enhanced the basal level of TNFalpha transcription, yet exerted a negative effect on the level of Tat activation of the TNFalpha promoter. The antagonistic effect of Puralpha and Tat upon the TNFalpha promoter was diminished in the presence of cyclin T1 and cdk9, suggesting cooperativity of Puralpha with cyclin T1 and cdk9 in Tat activation of the TNFalpha promoter. Results from protein-protein binding studies showed the interaction of Puralpha with both cyclin T1 and cdk9 through distinct domains of Puralpha which are in juxtaposition with each other. Interestingly, the site for cyclin T1 binding within Puralpha is adjacent to the region which is important for Tat/Puralpha association. In light of these observations, we propose a model which ascribes a bridging role for Puralpha in assembling Tat, cyclin T1, and cdk9 around the promoter region of TAR-negative genes such as TNFalpha, which is responsive to Tat activation.
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Affiliation(s)
- N Darbinian
- Center for Neurovirology and Cancer Biology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA
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18
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Jiménez JL, González-Nicolás J, Alvarez S, Fresno M, Muñoz-Fernández MA. Regulation of human immunodeficiency virus type 1 replication in human T lymphocytes by nitric oxide. J Virol 2001; 75:4655-63. [PMID: 11312336 PMCID: PMC114219 DOI: 10.1128/jvi.75.10.4655-4663.2001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Addition of nitric oxide (NO) donors to mitogen-activated human immunodeficiency virus type 1 (HIV-1)-infected peripheral blood mononuclear cultures produced a significant increase in virus replication, and this effect was not associated with a change in cell proliferation. This effect was only observed with T-tropic X4 or X4R5 virus but not with R5 virus. Moreover, HIV-1 replication in mitogen-stimulated cultures was partially prevented by the specific inhibitors of the inducible nitric oxide synthase (iNOS). NO donors also enhanced HIV-1 infection of the human T-cell lines, Jurkat and MT-2. We have also observed that NO leads to an enhancement of HIV-1 replication in resting human T cells transfected with a plasmid carrying the entire HIV-1 genome and activated with phorbol ester plus ionomycin. Thus, in those cultures NO donors strongly potentiated HIV-1 replication in a dose-dependent manner, up to levels comparable to those with tumor necrosis factor alpha (TNF-alpha) stimulation. Furthermore, iNOS inhibitors decreased HIV-1 replication in HIV-1-transfected T cells to levels similar to those obtained with neutralizing anti-TNF-alpha antibodies. Moreover, HIV-1 replication induced iNOS and TNF-alpha transcription in T cells and T-cell lines. Interestingly, NO donors also stimulated long terminal repeat (LTR)-driven transcription whereas iNOS inhibitors partially blocked TNF-alpha-induced LTR transcription. Therefore, our results suggest that NO is involved in HIV-1 replication, especially that induced by TNF-alpha.
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Affiliation(s)
- J L Jiménez
- Division of Immunology, Hospital Universitario Gregorio Marañón, Madrid, Spain
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19
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Tyagi M, Rusnati M, Presta M, Giacca M. Internalization of HIV-1 tat requires cell surface heparan sulfate proteoglycans. J Biol Chem 2001; 276:3254-61. [PMID: 11024024 DOI: 10.1074/jbc.m006701200] [Citation(s) in RCA: 551] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tat, the transactivator protein of human immunodeficiency virus-1, has the unusual capacity of being internalized by cells when present in the extracellular milieu. This property can be exploited for the cellular delivery of heterologous proteins fused to Tat both in cell culture and in living animals. Here we provide genetic and biochemical evidence that cell membrane heparan sulfate (HS) proteoglycans act as receptors for extracellular Tat uptake. Cells genetically defective in the biosynthesis of fully sulfated HS are selectively impaired in the internalization of recombinant Tat fused to the green fluorescent protein, as evaluated by both flow cytometry and functional assays. In wild type cells, Tat uptake is competitively inhibited by soluble heparin and by treatment with glycosaminoglycan lyases specifically degrading HS chains. Cell surface HS proteoglycans also mediate physiological internalization of Tat green fluorescent protein released from neighboring producing cells. In contrast to extracellular Tat uptake, both wild type cells and cells genetically impaired in proteoglycan synthesis are equally proficient in the extracellular release of Tat, thus indicating that proteoglycans are not required for this process. The ubiquitous distribution of HS proteoglycans is consistent with the efficient intracellular delivery of heterologous proteins fused with Tat to different mammalian cell types.
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Affiliation(s)
- M Tyagi
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), 34012 Trieste, Italy
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20
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Biswas DK, Cruz AP, Gansberger E, Pardee AB. Epidermal growth factor-induced nuclear factor kappa B activation: A major pathway of cell-cycle progression in estrogen-receptor negative breast cancer cells. Proc Natl Acad Sci U S A 2000; 97:8542-7. [PMID: 10900013 PMCID: PMC26984 DOI: 10.1073/pnas.97.15.8542] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2000] [Indexed: 11/18/2022] Open
Abstract
The epidermal growth factor (EGF) family of receptors (EGFR) is overproduced in estrogen receptor (ER) negative (-) breast cancer cells. An inverse correlation of the level of EGFR and ER is observed between ER- and ER positive (+) breast cancer cells. A comparative study with EGFR-overproducing ER- and low-level producing ER+ breast cancer cells suggests that EGF is a major growth-stimulating factor for ER- cells. An outline of the pathway for the EGF-induced enhanced proliferation of ER- human breast cancer cells is proposed. The transmission of mitogenic signal induced by EGF-EGFR interaction is mediated via activation of nuclear factor kappaB (NF-kappaB). The basal level of active NF-kappaB in ER- cells is elevated by EGF and inhibited by anti-EGFR antibody (EGFR-Ab), thus qualifying EGF as a NF-kappaB activation factor. NF-kappaB transactivates the cell-cycle regulatory protein, cyclin D1, which causes increased phosphorylation of retinoblastoma protein, more strongly in ER- cells. An inhibitor of phosphatidylinositol 3 kinase, Ly294-002, blocked this event, suggesting a role of the former in the activation of NF-kappaB by EGF. Go6976, a well-characterized NF-kappaB inhibitor, blocked EGF-induced NF-kappaB activation and up-regulation of cell-cycle regulatory proteins. This low molecular weight compound also caused apoptotic death, predominantly more in ER- cells. Thus Go6976 and similar NF-kappaB inhibitors are potentially novel low molecular weight therapeutic agents for treatment of ER- breast cancer patients.
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Affiliation(s)
- D K Biswas
- Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA 02115, USA.
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21
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Marasco WA, LaVecchio J, Winkler A. Human anti-HIV-1 tat sFv intrabodies for gene therapy of advanced HIV-1-infection and AIDS. J Immunol Methods 1999; 231:223-38. [PMID: 10648940 DOI: 10.1016/s0022-1759(99)00159-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The early successes of highly active anti-retroviral therapies (HAART) for the treatment of HIV-1-infection and AIDS have raised the question as to whether there is a legitimate role for gene therapy in the treatment of this chronic infectious disease. However, in many patients the profound suppression of viral replication is short lived, particularly if patients have been treated with sequential monotherapies in the past, have been infected with a highly drug resistant isolate of HIV-1, or have temporarily discontinued therapy as a "holiday" or because of drug intolerance. In addition, life-long adherence to maintenance HAART will probably be required even in responding patients with undetectable viremia because of the reservoirs of latently infected cells that can persist for years. Gene therapy through the introduction of anti-retroviral "resistance" genes into CD4(+) T cells is one approach that could give long term protection to these HIV-1 susceptible cells in vivo. We have explored this approach by developing intrabodies to the critical HIV-1 transactivator protein, Tat that is absolutely required for HIV-1 replication. This provocative treatment approach, that will be tested in a clinical gene therapy trial, sets the groundwork for determining if anti-Tat intrabody gene therapy together with HAART can provide a treatment strategy for the immune reconstitution of HIV-1-infected patients with advanced disease.
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Affiliation(s)
- W A Marasco
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA.
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22
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Kelly GD, Morris CB, Offermann MK. Lack of responsiveness of a nuclear factor-kappaB-regulated promoter to transactivation by human immunodeficiency virus 1 Tat in HeLa cells. Virology 1999; 263:128-38. [PMID: 10544088 DOI: 10.1006/viro.1999.9966] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transcriptional activation by Tat protein is in large part dependent on interactions with the TAR RNA element located in the 5'-untranslated region of all human immunodeficiency virus type 1 (HIV-1) transcripts. In addition, Tat has been shown to induce nuclear translocation of nuclear factor-kappaB (NF-kappaB), potentially contributing to gene induction. The NF-kappaB responsive reporter construct, (PRDII)(4)-CAT, was used to explore transcription resulting from NF-kappaB activated by Tat. Tat did not activate (PRDII)(4)-CAT, whereas (PRDII)(4)-CAT was highly responsive to either transfected Rel A or to tumor necrosis factor-alpha (TNF-alpha). Despite its inability to directly induce, Tat enhanced the responsiveness of (PRDII)(4)-CAT to either transfected Rel A or to TNF-alpha by approximately 2.5-fold. High levels of CAT activity were seen with HIV-LTR-derived reporters that contained kappaB and TAR elements in response to transfected Tat in the absence of either transfected Rel A or exogenous TNF-alpha, and overexpression of IkappaBalpha with Tat inhibited CAT activity by 60% to 80%, suggesting that some activation of NF-kappaB by Tat was occurring. HIV-LTR reporter activities were enhanced three fold to sixfold compared with Tat alone when additional NF-kappaB was provided by transfection or by activation with TNF-alpha. These data indicate that Tat is unable to activate some NF-kappaB-responsive promoters but is able to synergize with NF-kappaB in the activation of both HIV-derived and non-HIV-derived promoters.
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Affiliation(s)
- G D Kelly
- Department of Medicine, Emory University, Atlanta, Georgia 30322, USA
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23
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Yang X, Chen Y, Gabuzda D. ERK MAP kinase links cytokine signals to activation of latent HIV-1 infection by stimulating a cooperative interaction of AP-1 and NF-kappaB. J Biol Chem 1999; 274:27981-8. [PMID: 10488148 DOI: 10.1074/jbc.274.39.27981] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) can establish latent infection following provirus integration into the host genome. NF-kappaB plays a critical role in activation of HIV-1 gene expression by cytokines and other stimuli, but the signal transduction pathways that regulate the switch from latent to productive infection have not been defined. Here, we show that ERK1/ERK2 mitogen-activated protein kinase (MAPK) plays a central role in linking signals at the cell surface to activation of HIV-1 gene expression in latently infected cells. MAPK was activated by cytokines and phorbol 12-myristate 13-acetate in latently infected U1 cells. The induction of HIV-1 expression by these stimuli was inhibited by PD98059 and U0126, which are specific inhibitors of MAPK activation. Studies using constitutively active MEK or Raf kinase mutants demonstrated that MAPK activates the HIV-1 long terminal repeat (LTR) through the NF-kappaB sites. Most HIV-1 inducers activated NF-kappaB via a MAPK-independent pathway, indicating that activation of NF-kappaB is not sufficient to explain the activation of HIV-1 gene expression by MAPK. In contrast, all of the stimuli activated AP-1 via a MAPK-dependent pathway. NF-kappaB and AP-1 components c-Fos and c-Jun were shown to physically associate by yeast two-hybrid assays and electrophoretic mobility shift assays. Coexpression of NF-kappaB and c-Fos or c-Jun synergistically transactivated the HIV-1 LTR through the NF-kappaB sites. These studies suggest that MAPK acts by stimulating AP-1 and a subsequent physical and functional interaction of AP-1 with NF-kappaB, resulting in a complex that synergistically transactivates the HIV-1 LTR. These results define a mechanism for signal-dependent activation of HIV-1 replication in latently infected cells and suggest potential therapeutic strategies for unmasking latent reservoirs of HIV-1.
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Affiliation(s)
- X Yang
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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24
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Demarchi F, Gutierrez MI, Giacca M. Human immunodeficiency virus type 1 tat protein activates transcription factor NF-kappaB through the cellular interferon-inducible, double-stranded RNA-dependent protein kinase, PKR. J Virol 1999; 73:7080-6. [PMID: 10400814 PMCID: PMC112801 DOI: 10.1128/jvi.73.8.7080-7086.1999] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The transactivator protein of human immunodeficiency virus type 1 (HIV-1) (Tat) is a powerful activator of nuclear factor-kappaB (NF-kappaB), acting through degradation of the inhibitor IkappaB-alpha (F. Demarchi, F. d'Adda di Fagagna, A. Falaschi, and M. Giacca, J. Virol. 70:4427-4437, 1996). Here, we show that this activity of Tat requires the function of the cellular interferon-inducible protein kinase PKR. Tat-mediated NF-kappaB activation and transcriptional induction of the HIV-1 long terminal repeat were impaired in murine cells in which the PKR gene was knocked out. Both functions were restored by cotransfection of Tat with the cDNA for PKR. Expression of a dominant-negative mutant of PKR specifically reduced the levels of Tat transactivation in different human cell types. Activation of NF-kappaB by Tat required integrity of the basic domain of Tat; previous studies have indicated that this domain is necessary for specific Tat-PKR interaction.
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Affiliation(s)
- F Demarchi
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology, 34012 Trieste, Italy
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25
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Axelrod JH, Honigman A. A sensitive and versatile bioluminescence bioassay for HIV type 1 based on adenoviral vectors. AIDS Res Hum Retroviruses 1999; 15:759-67. [PMID: 10357471 DOI: 10.1089/088922299310845] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The construction and characterization of a versatile bioassay for the quantification of HIV-1 viral infection and HIV-1 Tat protein activity based on recombinant adenoviral vectors carrying an HIV LTR-driven luciferase reporter gene is described. The assay system consists of a set of two adeno-reporter vectors, one of which is responsive to HIV-1 Tat protein activity, and the second of which is not, by virtue of a deletion of the TAR site within the HIV LTR. This configuration of the reporter genes allows one to distinguish Tat-specific activation from Tat-non-specific HIV LTR-mediated gene expression. The adenoviral HIV LTR-mediated luciferase gene expression is highly responsive to Tat and increases linearly with increasing levels of HIV-1 infection, reaching levels of between 3- and 1000-fold induction. The adeno-reporter viruses can be utilized to detect Tat activity and HIV-1 infection in a wide range of cell types, including 293, CEM, HUT-78, Jurkat, and HeLa-derived cell lines. The resulting bioassay is convenient, sensitive, and readily adaptable to automated procedures. These characteristics of the adeno-reporter assay make it a valuable reagent for studies of HIV infection and for analysis of HIV-inhibitory agents.
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Affiliation(s)
- J H Axelrod
- Department of Virology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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26
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Wang Z, Morris GF, Reed JC, Kelly GD, Morris CB. Activation of Bcl-2 promoter-directed gene expression by the human immunodeficiency virus type-1 Tat protein. Virology 1999; 257:502-10. [PMID: 10329560 DOI: 10.1006/viro.1999.9688] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) Tat transcriptionally activates expression from a number of viral and cellular promoters. Recent studies demonstrate the ability of Tat to differentially modulate cellular responses to apoptotic signaling. The antiapoptotic effects of Tat appear to correlate with increased expression of Bcl-2, a cellular protein that enhances cellular survival. Here, endogenous expression of HIV-1 Tat in HeLa and Jurkat cells elevates levels of Bcl-2. Transient expression assays performed in HeLa cells demonstrate that Tat directly or indirectly enhances Bcl-2 promoter-directed gene expression by more than 10-fold. Analyses of Tat mutants demonstrate that two noncontiguous regions in the N- and C-termini of Tat mediate maximal transactivation of the Bcl-2 promoter. The requirement for C-terminal sequences contrasts with transactivation of the HIV-1 long terminal repeat in which the N-terminal 57 amino acids are required but downstream residues are not. Bcl-2 promoter analyses suggest that sequences required for Tat responsiveness are located upstream of P1 and between the P1 and P2 promoter units. Results from these studies reveal effects of HIV-1 Tat on Bcl-2 expression and provide a putative mechanism by which endogenously expressed Tat affects cellular survival through the up-regulation of Bcl-2.
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Affiliation(s)
- Z Wang
- Department of Pathology and Laboratory Medicine, Tulane Cancer Center, New Orleans, Louisiana, 70112, USA
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27
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Biswas DK, Reddy PV, Pickard M, Makkad B, Pettit N, Pardee AB. Calmodulin is essential for estrogen receptor interaction with its motif and activation of responsive promoter. J Biol Chem 1998; 273:33817-24. [PMID: 9837972 DOI: 10.1074/jbc.273.50.33817] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calmodulin (CaM) has been reported to have affinity for the estrogen receptor (ER). Observations reported here reveal a direct physical interaction between purified CaM and ER. This direct ER-CaM interaction may be an initial event preceding the assembly of ER plus auxiliary proteins into the active ER complex with its DNA motif, the estrogen response element. We demonstrate that CaM is an integral component of this complex by using a system reconstituted from purified ER and nuclear extract from ER-negative breast cancer cells and also with ER-depleted nuclear extract of an ER-positive breast cancer cell line. Although CaM is essential for formation of this complex, it is not sufficient, suggesting roles also of auxiliary proteins. CaM also is functionally required for activation of an ER-responsive promoter, in the 17beta-estradiol-ER pathway of hormone action and regulation of 17beta-estradiol-responsive gene expression that is associated with proliferation of mammary epithelial cells.
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Affiliation(s)
- D K Biswas
- Division of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
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28
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Biswas DK, Mhashilkar AM, Ewaniuk DS, Pezza JA, Oh LM, Kannangara GS, Tius MA, Pardee AB. Inhibition of HIV-1 replication by combination of a novel inhibitor of TNF-alpha with AZT. JOURNAL OF ACQUIRED IMMUNE DEFICIENCY SYNDROMES AND HUMAN RETROVIROLOGY : OFFICIAL PUBLICATION OF THE INTERNATIONAL RETROVIROLOGY ASSOCIATION 1998; 18:426-34. [PMID: 9715838 DOI: 10.1097/00042560-199808150-00003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The small molecule S9a was derived from an established tumor necrosis factor-alpha (TNF-alpha) inhibitor (Canventol) by replacement of the isopropylidine group with a phenyl ring. S9a at 10 to 100 nM inhibited HIV production as potently as 3'-azido-3'-deoxythymidine (AZT), an inhibitor of viral reverse transcriptase. Furthermore, S9a and AZT in combination, at noncytoxic concentrations strongly inhibited HIV-1 replication that was more than additive and substantially prolonged the appearance of virus both in acutely infected CD4+ lymphocytes (SupT) in culture and in peripheral blood mononuclear cells (PBMCs) infected with a primary HIV-1 isolate. S9a inhibited TNF-alpha promoter-driven reporter gene activity. It was proposed that the mechanism of antiviral action of S9a was on the host cell, by blocking TNF-alpha transcription via a Tat-induced tar-independent loop, which decreases downstream NF-kappaB activation of HIV-1 long terminal repeat (LTR). S9a was superior to the first generation compound Canventol, which was superior to the natural compound sarcophytol A, demonstrating that further structure-based enhancement of potency of these compounds is feasible. This study suggests a therapeutic approach against AIDS by application of two drugs, one against a cellular and the other a viral target, which may provide an approach to the problem of frequent emergence of resistant variants to combinations of drugs that target only HIV genes.
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Affiliation(s)
- D K Biswas
- Division of Cell Growth and Regulation, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
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29
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Biswas DK, Averboukh L, Sheng S, Martin K, Ewaniuk DS, Jawde TF, Wang F, Pardee AB. Classification of breast cancer cells on the basis of a functional assay for estrogen receptor. Mol Med 1998; 4:454-67. [PMID: 9713824 PMCID: PMC2230334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND The receptor (ER) for estrogen (E2) is routinely assayed as a marker to determine the feasibility of anti-hormone therapy against breast cancer because ER-positive (ER+) tumors are much more likely to respond to anti-hormone therapy than are ER-negative (ER-). However 40% of ER+ breast cancer patients do not respond to anti-hormone therapy. We suggest that this unpredictability of therapeutic responses lies in the current ER assays, which measure only an initial component of the E2-responsive pathway, and that the difference depends upon altered downstream processes. We propose a functional criterion that subclassifies breast cancers on the basis of specific binding of ER to its cognate DNA sequence, the estrogen response element (ERE). MATERIALS AND METHODS ER was identified in breast cancer cell lines by immunofluorescence assay, Western blot analysis, identification of ER-specific mRNA, and by interaction of the ER-ERE complex with three different ER-specific antibodies. ER-ERE complex formation was measured by electrophoretic mobility shift assay (EMSA). Transactivation of the E2-responsive gene was studied by transfection of cells with fusion gene construct with the promoter-containing ERE sequence and assay of reporter gene activity in the cell extracts. RESULTS The growth of ER+ T47D cells was sensitive to tamoxifen, ICI-182,780, and ethynyl estradiol (EE2), whereas another ER+ breast cancer cell line, 21 PT, was resistant to these compounds. The estrogen receptor (ER) in the nuclear extracts of MCF-7 and T47D demonstrated hormone-dependent interaction with the response element (ERE) and also downstream transactivation of the E2-responsive PS2 promoter. But in the 21 PT cell line that was designated as ER- on the basis of ligand-binding assay and was found to be ER+ by all the other ER assays, ER-ERE interaction and PS2 promoter transactivation were independent of hormone. CONCLUSIONS On the basis of the downstream functional assay of ER interaction with ERE, ER+ breast tumor cells can be subclassified into two categories. The first is E2-dependent (ERd+) and these cells should respond to anti-hormone therapy. The second type of ER interacts with ERE independent of E2 (ERi+) and constitutively transactivates responsive genes. It is predicted that the latter type of breast cancers will not respond to antihormone therapy.
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MESH Headings
- Antibodies, Monoclonal
- Antineoplastic Agents, Hormonal/pharmacology
- Blotting, Northern
- Blotting, Western
- Breast Neoplasms/chemistry
- Breast Neoplasms/classification
- Breast Neoplasms/genetics
- Breast Neoplasms/pathology
- Cell Survival
- DNA-Binding Proteins/analysis
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Estradiol/analogs & derivatives
- Estradiol/pharmacology
- Estrogen Antagonists/pharmacology
- Female
- Fulvestrant
- Humans
- Promoter Regions, Genetic
- Receptors, Estrogen/analysis
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Regulatory Sequences, Nucleic Acid
- Tamoxifen/pharmacology
- Transcriptional Activation
- Transfection
- Tumor Cells, Cultured
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Affiliation(s)
- D K Biswas
- Division of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA.
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30
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Classification of Breast Cancer Cells on the Basis of a Functional Assay for Estrogen Receptor. Mol Med 1998. [DOI: 10.1007/bf03401751] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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31
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Adenovirus-Mediated Human Immunodeficiency Virus-1 Nef Expression in Human Monocytes/Macrophages and Effect of Nef on Downmodulation of Fcγ Receptors and Expression of Monokines. Blood 1998. [DOI: 10.1182/blood.v91.6.2108.2108_2108_2117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To characterize the effect of human immunodeficiency virus-1 (HIV-1)nef expression in human monocytes/macrophage (HMØ) and U937 on the levels of FcγRs, HLA antigens, and monokines, elutriated HMØs and U937 cells were transfected with an adenovirus-mediated Nef expression system. Nef-expressing cells downmodulated FcγRI, FcγRII, and upregulated HLA class I molecules. Nef-expressing HMØs, treated with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA), overexpressed tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-10. However, IL-6 was induced by LPS and inhibited by PMA. Additionally, a subpopulation of Nef-expressing HMØs underwent apoptosis. Our data suggest that HIV-1 nefdownmodulated FcγRs in myeloid cells in a manner similar to that previously reported for its effect on CD4+ in T cells.
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32
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Adenovirus-Mediated Human Immunodeficiency Virus-1 Nef Expression in Human Monocytes/Macrophages and Effect of Nef on Downmodulation of Fcγ Receptors and Expression of Monokines. Blood 1998. [DOI: 10.1182/blood.v91.6.2108] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractTo characterize the effect of human immunodeficiency virus-1 (HIV-1)nef expression in human monocytes/macrophage (HMØ) and U937 on the levels of FcγRs, HLA antigens, and monokines, elutriated HMØs and U937 cells were transfected with an adenovirus-mediated Nef expression system. Nef-expressing cells downmodulated FcγRI, FcγRII, and upregulated HLA class I molecules. Nef-expressing HMØs, treated with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA), overexpressed tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-10. However, IL-6 was induced by LPS and inhibited by PMA. Additionally, a subpopulation of Nef-expressing HMØs underwent apoptosis. Our data suggest that HIV-1 nefdownmodulated FcγRs in myeloid cells in a manner similar to that previously reported for its effect on CD4+ in T cells.
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33
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Rondon IJ, Marasco WA. Intracellular antibodies (intrabodies) for gene therapy of infectious diseases. Annu Rev Microbiol 1997; 51:257-83. [PMID: 9343351 DOI: 10.1146/annurev.micro.51.1.257] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Intracellular antibodies (intrabodies) represent a new class of neutralizing molecules with a potential use in gene therapy. Intrabodies are engineered single-chain antibodies in which the variable domain of the heavy chain is joined to the variable domain of the light chain through a peptide linker, preserving the affinity of the parent antibody. Intrabodies are expressed inside cells and directed to different subcellular compartments where they can exert their function more effectively. The effects of intrabodies have been investigated using structural, regulatory, and enzymatic proteins of the human immunodeficiency virus (HIV-1) as targets. These intrabodies have demonstrated their versatility by controlling early as well as late events of the viral life cycle. In this article, we review studies of the use of intrabodies as research tools and therapeutic agents against HIV-1.
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Affiliation(s)
- I J Rondon
- Division of Human Retrovirology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
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34
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Lechner F, Machado J, Bertoni G, Seow HF, Dobbelaere DA, Peterhans E. Caprine arthritis encephalitis virus dysregulates the expression of cytokines in macrophages. J Virol 1997; 71:7488-97. [PMID: 9311828 PMCID: PMC192095 DOI: 10.1128/jvi.71.10.7488-7497.1997] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Caprine arthritis encephalitis virus (CAEV) is a lentivirus of goats that leads to chronic mononuclear infiltration of various tissues, in particular, the radiocarpal joints. Cells of the monocyte/macrophage lineage are the major host cells of CAEV in vivo. We have shown that infection of cultured goat macrophages with CAEV results in an alteration of cytokine expression in vitro. Constitutive expression of interleukin 8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) was increased in infected macrophages, whereas transforming growth factor beta1 (TGF-beta1) mRNA was down-regulated. When macrophages were infected with a CAEV clone lacking the trans-acting nuclear regulatory gene tat, IL-8 and MCP-1 were also increased. No significant differences from cells infected with the wild-type clone were observed, suggesting that Tat is not required for the increased expression of IL-8 and MCP-1 in infected macrophages. Furthermore, infection with CAEV led to an altered pattern of cytokine expression in response to lipopolysaccharide (LPS), heat-killed Listeria monocytogenes plus gamma interferon, or fixed cells of Staphylococcus aureus Cowan I. In infected macrophages, tumor necrosis factor alpha, IL-1beta, IL-6, and IL-12 p40 mRNA expression was reduced in response to all stimuli tested whereas changes in expression of granulocyte-macrophage colony-stimulating factor depended on the stimulating agent. Electrophoretic mobility shift assays demonstrated that, in contrast to effects of human immunodeficiency virus infection of macrophages, CAEV infection had no effect on the level of constitutive nuclear factor-kappaB (NF-kappaB) activity or on the level of LPS-stimulated NF-kappaB activity, suggesting that NF-kappaB is not involved in altered regulation of cytokine expression in CAEV-infected cells. In contrast, activator protein 1 (AP-1) binding activity was decreased in infected macrophages. These data show that CAEV infection may result in a dysregulation of expression of cytokines in macrophages. This finding suggests that CAEV may modulate the accessory functions of infected macrophages and the antiviral immune response in vivo.
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Affiliation(s)
- F Lechner
- Institute of Veterinary Virology, University of Bern, Switzerland
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35
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Mhashilkar AM, Biswas DK, LaVecchio J, Pardee AB, Marasco WA. Inhibition of human immunodeficiency virus type 1 replication in vitro by a novel combination of anti-Tat single-chain intrabodies and NF-kappa B antagonists. J Virol 1997; 71:6486-94. [PMID: 9261367 PMCID: PMC191923 DOI: 10.1128/jvi.71.9.6486-6494.1997] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) Tat, an early regulatory protein that is critical for viral gene expression and replication, transactivates the HIV-1 long terminal repeat (LTR) via its binding to the transactivation response element (TAR) and, along with other cellular factors, increases viral transcription initiation and elongation. Tat also superactivates the HIV-1 promoter through a TAR-independent mechanism, including tumor necrosis factor alpha-induced and protein kinase C (PKC)-dependent activation of NF-kappa B, and inhibitors of Tat and NF-kappa B cooperatively down-regulate this Tat-mediated LTR superactivation. In this study, a combined pharmacologic and genetic strategy using two PKC (NF-kappa B) inhibitors, pentoxifylline (PTX) and Gö-6976, and a stably expressed anti-Tat single-chain intracellular antibody (sFv intrabody) was employed to obtain cooperative inhibition of both HIV-1 LTR-driven gene expression and HIV-1 replication. Treatment of cells with PTX and Gö-6976 resulted in cooperative inhibition of both HIV-1 LTR-driven gene expression and HIV-1 replication. In addition, the combined use of anti-Tat sFv intrabodies and the two NF-kappa B inhibitors retained the virus in the latent state for as long as 45 days. The combined treatment resulted in more durable inhibition of HIV-1 replication than was seen with the NF-kappa B inhibitors alone or the anti-Tat sFv intrabodies alone. Together, these results suggest that in future clinical gene therapy trials, a combined pharmacologic and genetic strategy like the one reported here may improve the survival of transduced cells and prolong clinical benefit.
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Affiliation(s)
- A M Mhashilkar
- Division of Human Retrovirology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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36
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Yang L, Morris GF, Lockyer JM, Lu M, Wang Z, Morris CB. Distinct transcriptional pathways of TAR-dependent and TAR-independent human immunodeficiency virus type-1 transactivation by Tat. Virology 1997; 235:48-64. [PMID: 9300036 DOI: 10.1006/viro.1997.8672] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Tat stimulates HIV-1 gene expression during transcription initiation and elongation. Tat functions primarily through specific interactions with TAR RNA and several putative cellular cofactors to increase the processivity of RNA polymerase II complexes during HIV-1 transcription elongation. Although HIV-1 transactivation by Tat in most cell types requires intact TAR sequences, previous reports demonstrate that Tat transactivates HIV-1 long terminal repeat (LTR)-directed gene expression in several central nervous system-derived astrocytic/glial cell lines in the absence of TAR. Within this study, transient expression assays performed in the astrocytic/glial cell line, U87-MG, confirm that kappa B elements within the HIV-1 LTR mediate TAR-independent transactivation by Tat and demonstrate additionally that distinct amino acid residues within the cysteine-rich activation domain of Tat are required for TAR-independent versus TAR-dependent transactivation. Established U87-MG cell lines expressing a transdominant negative mutant of I kappa B alpha, I kappa B alpha delta N, fail to support TAR-independent transactivation by Tat, suggesting that binding of NF-kappa B to kappa B enhancer elements within the HIV-1 LTR is necessary for Tat-mediated transactivation in the absence of TAR. Ribonucleic acid protection analyses of promoter-proximal and -distal transcripts derived from TAR-deleted and TAR-containing HIV-1 LTR reporter constructs in U87-MG cells indicate that the predominant effect of Tat during TAR-independent transactivation occurs at the lavel of transcription initiation, whereas a prominent elongation effect of Tat is observed in the presence of TAR. These data suggest an alternative regulatory pathway for Tat transactivation in specific cells derived from the central nervous system that is independent of TAR and that requires direct or indirect interaction of Tat with NF-kappa B-binding sites in the HIV-1 LTR.
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Affiliation(s)
- L Yang
- School of Biology, Georgia Institute of Technology, Atlanta 30332, USA
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37
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Lisziewicz J, Sun D, Gallo RC, Ensoli B, Lori F. Efficacy of antitat gene therapy in the presence of high multiplicity infection and inflammatory cytokines. Hum Gene Ther 1996; 7:2209-16. [PMID: 8953311 DOI: 10.1089/hum.1996.7.18-2209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Because human immunodeficiency virus type 1 (HIV-1) infection is characterized by a large number of viral replication cycles and rapid cell turnover in vivo, successful gene therapy requires an approach effective under these conditions. The antitat gene has been proposed for gene therapy because it effectively blocks Tat function and the replication of HIV-1. However, neither antitat nor any other antiviral gene has been shown to inhibit HIV in the presence of high viral load and inflammatory cytokines, a condition closer to the in vivo situation. We show that cells transduced with antitat retrovirus vector are resistant to high multiplicity of HIV infection. In the presence of inflammatory cytokines, including interleukin-1 and tumor necrosis factor, both known to activate viral gene expression independently of Tat, antitat suppressed virus replication. HIV-1 inhibition was observed when cell were treated with a mixture of inflammatory cytokines able to induce acquired immunodeficiency syndrome (AIDS) Kaposi's sarcoma cell growth. These molecules have been shown to be increased in HIV-1-infected individuals, and it is suggested they play a role in the pathogenesis of AIDS. Our results suggest that antitat is effective under conditions present in vivo and therefore a primary candidate for HIV-1 gene therapy.
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Affiliation(s)
- J Lisziewicz
- Research Institute for Genetic and Human Therapy, Gaithersburg, MD 20879, USA
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38
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Zauli G, Gibellini D. The human immunodeficiency virus type-1 (HIV-1) Tat protein and Bcl-2 gene expression. Leuk Lymphoma 1996; 23:551-60. [PMID: 9031086 DOI: 10.3109/10428199609054864] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Tat protein of human immunodeficiency virus type-1 (HIV-1) plays a central role in viral replication and shows pleiotropic effects on the survival and growth of different cell types. Remarkably, Tat represents the first example of a viral protein, that can also be actively secreted by infected cells and shows a cytokine-like activity on both HIV-1 infected and uninfected cells. We previously reported that the stable expression of tat cDNA rescues Jurkat cell lines from apoptosis induced by a variety of stimuli, such as serum withdrawal, engagement of fas antigen or even a productive infection with HIV-1. These findings suggested that Tat was able to modulate the expression of one or more gene(s) relevant for the control of cell survival/death. Consistently, Jurkat cells stably transfected with tat show an upregulated expression of bcl-2. It is still unsettled whether Tat affects cell survival and bcl-2 expression directly or indirectly, modulating the expression of other cellular genes involved in the control of cell survival or encoding for cytokines. Blocking experiments performed with anti-Tat neutralizing antibodies revealed that TAt increases bcl-2 expression and prevent lymphoid T cells from apoptosis by acting, at least in part, through an autocrine/paracrine loop. While high (nM-microM) concentrations of extracellular Tat display a cytotoxic activity on the antigen-mediated induction of T cell proliferation, low (pM) concentrations of Tat were able to protect both Jurkat cells and primary peripheral blood mononuclear cells from apoptosis. Significantly, pM concentrations of Tat were detected in the sera of some HIV-1 infected individuals as well as in the culture supernatant of HIV-1 infected cells, raising the possibility that these levels of Tat protein may be present physiologically in vivo. The potential relevance of Tat-mediated upregulation of bcl-2 for the pathogenesis of HIV-1 disease is discussed.
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Affiliation(s)
- G Zauli
- Institute of Human Anatomy, University of Ferrara, Italy
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39
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Sodroski J. Perspective: research highlights at the Dana-Farber Cancer Institute Center for AIDS Research (CFAR). AIDS Res Hum Retroviruses 1996; 12:1499-502. [PMID: 8911574 DOI: 10.1089/aid.1996.12.1499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Affiliation(s)
- J Sodroski
- Dana-Farber Cancer Institute, Department of Pathology, Harvard Medical School, Boston, Massachusetts, USA
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40
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Beauparlant P, Kwon H, Clarke M, Lin R, Sonenberg N, Wainberg M, Hiscott J. Transdominant mutants of I kappa B alpha block Tat-tumor necrosis factor synergistic activation of human immunodeficiency virus type 1 gene expression and virus multiplication. J Virol 1996; 70:5777-85. [PMID: 8709193 PMCID: PMC190591 DOI: 10.1128/jvi.70.9.5777-5785.1996] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) contains two binding sites for the NF-kappa B/Rel family of transcription factors which are required for the transcriptional activation of viral genes by inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) and interleukin-1. In the present study, we examined the effect of transdominant mutants of I kappa B alpha on the synergistic activation of the HIV-1 LTR by TNF-alpha and the HIV-1 transactivator, Tat, in Jurkat T cells. The synergistic induction of HIV-1 LTR-driven gene expression represented a 50- to 70-fold stimulation and required both an intact HIV-1 enhancer and Tat-TAR element interaction, since mutations in Tat protein (R52Q, R53Q) or in the bulge region of the TAR element that eliminated Tat binding to TAR were unable to stimulate LTR expression. Coexpression of I kappa B alpha inhibited Tat-TNF-alpha activation of HIV LTR in a dose-dependent manner. Transdominant forms of I kappa B alpha, mutated in critical serine or threonine residues required for inducer-mediated (S32A, S36A) and/or constitutive (S283A, T291A, T299A) phosphorylation of I kappa B alpha were tested for their capacity to block HIV-1 LTR transactivation. I kappa B alpha molecules mutated in the N-terminal sites were not degraded following inducer-mediated stimulation (t1/2, > 4 h) and were able to efficiently block HIV-1 LTR transactivation. Strikingly, the I kappa B alpha (S32A, S36A) transdominant mutant was at least five times as effective as wild-type I kappa B alpha in inhibiting synergistic induction of the HIV-1 LTR. This mutant also effectively inhibited HIV-1 multiplication in a single-cycle infection model in Cos-1 cells, as measured by Northern (RNA) blot analysis of viral mRNA species and viral protein production. These experiments suggest a strategy that may contribute to inhibition of HIV-1 gene expression by interfering with the NF-kappa B/Rel signaling pathway.
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Affiliation(s)
- P Beauparlant
- Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
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