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Chou TC, Maggirwar NS, Marsden MD. HIV Persistence, Latency, and Cure Approaches: Where Are We Now? Viruses 2024; 16:1163. [PMID: 39066325 PMCID: PMC11281696 DOI: 10.3390/v16071163] [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: 06/25/2024] [Revised: 07/13/2024] [Accepted: 07/17/2024] [Indexed: 07/28/2024] Open
Abstract
The latent reservoir remains a major roadblock to curing human immunodeficiency virus (HIV) infection. Currently available antiretroviral therapy (ART) can suppress active HIV replication, reduce viral loads to undetectable levels, and halt disease progression. However, antiretroviral drugs are unable to target cells that are latently infected with HIV, which can seed viral rebound if ART is stopped. Consequently, a major focus of the field is to study the latent viral reservoir and develop safe and effective methods to eliminate it. Here, we provide an overview of the major mechanisms governing the establishment and maintenance of HIV latency, the key challenges posed by latent reservoirs, small animal models utilized to study HIV latency, and contemporary cure approaches. We also discuss ongoing efforts to apply these approaches in combination, with the goal of achieving a safe, effective, and scalable cure for HIV that can be extended to the tens of millions of people with HIV worldwide.
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Affiliation(s)
- Tessa C. Chou
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92617, USA; (T.C.C.); (N.S.M.)
| | - Nishad S. Maggirwar
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92617, USA; (T.C.C.); (N.S.M.)
| | - Matthew D. Marsden
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, CA 92617, USA; (T.C.C.); (N.S.M.)
- Department of Medicine, Division of Infectious Disease, School of Medicine, University of California, Irvine, CA 92617, USA
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2
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Shortridge MD, Wille PT, Jones AN, Davidson A, Bogdanovic J, Arts E, Karn J, Robinson JA, Varani G. An ultra-high affinity ligand of HIV-1 TAR reveals the RNA structure recognized by P-TEFb. Nucleic Acids Res 2019; 47:1523-1531. [PMID: 30481318 PMCID: PMC6379670 DOI: 10.1093/nar/gky1197] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/09/2018] [Accepted: 11/23/2018] [Indexed: 12/16/2022] Open
Abstract
The HIV-1 trans-activator protein Tat binds the trans-activation response element (TAR) to facilitate recruitment of the super elongation complex (SEC) to enhance transcription of the integrated pro-viral genome. The Tat–TAR interaction is critical for viral replication and the emergence of the virus from the latent state, therefore, inhibiting this interaction has long been pursued to discover new anti-viral or latency reversal agents. However, discovering active compounds that directly target RNA with high affinity and selectivity remains a significant challenge; limiting pre-clinical development. Here, we report the rational design of a macrocyclic peptide mimic of the arginine rich motif of Tat, which binds to TAR with low pM affinity and 100-fold selectivity against closely homologous RNAs. Despite these unprecedented binding properties, the new ligand (JB181) only moderately inhibits Tat-dependent reactivation in cells and recruitment of positive transcription elongation factor (P-TEFb) to TAR. The NMR structure of the JB181–TAR complex revealed that the ligand induces a structure in the TAR loop that closely mimics the P-TEFb/Tat1:57/AFF4/TAR complex. These results strongly suggest that high-affinity ligands which bind the UCU bulge are not likely to inhibit recruitment of the SEC and suggest that targeting of the TAR loop will be an essential feature of effective Tat inhibitors.
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Affiliation(s)
- Matthew D Shortridge
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
| | - Paul T Wille
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106-4960
| | - Alisha N Jones
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
| | - Amy Davidson
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
| | - Jasmina Bogdanovic
- Department of Chemistry, University of Zurich, Zurich, Switzerland CH-8057
| | - Eric Arts
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106-4960
| | - Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106-4960
| | - John A Robinson
- Department of Chemistry, University of Zurich, Zurich, Switzerland CH-8057
| | - Gabriele Varani
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700
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3
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Rojas VK, Park IW. Role of the Ubiquitin Proteasome System (UPS) in the HIV-1 Life Cycle. Int J Mol Sci 2019; 20:ijms20122984. [PMID: 31248071 PMCID: PMC6628307 DOI: 10.3390/ijms20122984] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 01/18/2023] Open
Abstract
Given that the ubiquitin proteasome system (UPS) is the major protein degradation process in the regulation of a wide variety of cellular processes in eukaryotic cells, including alteration of cellular location, modulation of protein activity, and regulation of protein interaction, it is reasonable to suggest that the infecting HIV-1 and the invaded hosts exploit the UPS in a contest for survival and proliferation. However, to date, regulation of the HIV-1 life cycle has been mainly explained by the stage-specific expression of HIV-1 viral genes, not by elimination processes of the synthesized proteins after completion of their duties in the infected cells, which is also quintessential for understanding the molecular processes of the virus life cycle and thereby HIV-1 pathogenesis. In fact, several previous publications have indicated that the UPS plays a critical role in the regulation of the proteasomal degradation of viral and cellular counterparts at every step of the HIV-1 life cycle, from the virus entry to release of the assembled virus particles, which is integral for the regulation of survival and proliferation of the infecting HIV-1 and to replication restriction of the invading virus in the host. However, it is unknown whether and how these individual events taking place at different stages of the HIV-1 life cycle are orchestrated as an overall strategy to overcome the restrictions conferred by the host cells. Thus, in this review, we overview the interplay between HIV-1 viral and cellular proteins for restrictions/competitions for proliferation of the virus in the infected cell, which could open a new avenue for the development of therapeutics against HIV-1 via targeting a specific step of the proteasome degradation pathway during the HIV-1 life cycle.
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Affiliation(s)
- Vivian K Rojas
- Department of Microbiology, Immunology, and Genetics, University of North Texas, Health Science Center, Fort Worth, TX 76107, USA.
| | - In-Woo Park
- Department of Microbiology, Immunology, and Genetics, University of North Texas, Health Science Center, Fort Worth, TX 76107, USA.
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4
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Gatignol A, Duarte M, Daviet L, Chang YN, Jeang KT. Sequential steps in Tat trans-activation of HIV-1 mediated through cellular DNA, RNA, and protein binding factors. Gene Expr 2018; 5:217-28. [PMID: 8723388 PMCID: PMC6138028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The regulation of HIV expression is controlled by the activity of the Long Terminal Repeat (LTR). Trans-activation by the virally encoded Tat protein is one of the main mechanisms of LTR activation. Tat binds to its target, TAR RNA, and cellular proteins that bind the LTR, Tat, or TAR RNA are important components of the trans-activation process. We will review the factors that have been characterized for a possible involvement in this mechanism. Whereas LTR binding proteins consist of Sp1 and TBP, a large number of factors that bind TAR RNA have been isolated. We have previously cloned two of them by RNA probe recognition: TRBP and La. We have shown that the in vitro and in vivo binding of TRBP to TAR RNA correlates with a constant expression of the protein during HIV-1 infection. Several proteins that interact with Tat have mainly positive, but some negative, effects on trans-activation. Genetic studies have defined that human chromosome 12 encodes a protein that will allow trans-activation in rodent cells. The binding and the functional data about these proteins suggest sequential steps for the Tat trans-activation mechanism. Each of these intracellular molecular events could be the target for molecular intervention against the virus.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Cloning, Molecular
- DNA, Complementary/genetics
- DNA, Viral/genetics
- DNA, Viral/metabolism
- Gene Products, tat/genetics
- Gene Products, tat/metabolism
- HIV Long Terminal Repeat
- HIV-1/genetics
- HIV-1/metabolism
- HeLa Cells
- Humans
- Models, Biological
- Molecular Sequence Data
- Protein Binding
- RNA, Viral/genetics
- RNA, Viral/metabolism
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Transcriptional Activation
- tat Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- A Gatignol
- Unité 332 INSERM, Institut Cochin de Génétique Moléculaire, Paris, France
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5
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Rice AP. The HIV-1 Tat Protein: Mechanism of Action and Target for HIV-1 Cure Strategies. Curr Pharm Des 2018; 23:4098-4102. [PMID: 28677507 DOI: 10.2174/1381612823666170704130635] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 06/12/2017] [Accepted: 06/20/2017] [Indexed: 02/07/2023]
Abstract
The general mechanism involved in Tat activation of RNA Polymerase II (RNAP II) elongation of the integrated HIV-1 was elucidated over 20 years ago. This mechanism involves Tat binding to the TAR RNA element that forms at the 5' end of viral transcripts and recruiting a general RNAP II elongation factor termed as PTEFb. This elongation factor consists of CDK9 and Cyclin T1, and when recruited by Tat to TAR RNA, CDK9 was proposed to phosphorylate the carboxyl terminal domain of RNAP II and thereby activate elongation. Research in the past two decades has shown that the mechanism of Tat action is considerably more complicated than this simple model. In metabolically active cells, CDK9 and Cyclin T1 are now known to be largely sequestered in a RNA-protein complex termed the 7SK RNP. CDK9 and Cyclin T1 are released from the 7SK RNP by mechanisms not yet fully elucidated and along with Tat, bind to TAR RNA and orchestrate the assembly of a Super Elongation Complex (SEC) containing several additional proteins. CDK9 in the SEC then phosphorylates multiple substrates in the RNAP II complex to activate elongation. Importantly for therapeutic strategies, CDK9 and Cyclin T1 functions are down-regulated in resting CD4+ T cells that harbor latent HIV-1, and their up-regulation is required for reactivation of latent virus. Current strategies for a functional cure of HIV-1 infection therefore are likely to require development of latency reversal agents that up-regulate CDK9 and Cyclin T1 function in resting CD4+ T cells.
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Affiliation(s)
- Andrew P Rice
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030. United States
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6
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Changes in the cellular microRNA profile by the intracellular expression of HIV-1 Tat regulator: A potential mechanism for resistance to apoptosis and impaired proliferation in HIV-1 infected CD4+ T cells. PLoS One 2017; 12:e0185677. [PMID: 28968466 PMCID: PMC5624617 DOI: 10.1371/journal.pone.0185677] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 08/28/2017] [Indexed: 12/13/2022] Open
Abstract
HIV-1 induces changes in the miRNA expression profile of infected CD4+ T cells that could improve viral replication. HIV-1 regulator Tat modifies the cellular gene expression and has been appointed as an RNA silencing suppressor. Tat is a 101-residue protein codified by two exons that regulates the elongation of viral transcripts. The first exon of Tat (amino acids 1–72) forms the transcriptionally active protein Tat72, but the presence of the second exon (amino acids 73–101) results in a more competent regulatory protein (Tat101) with additional functions. Intracellular, full-length Tat101 induces functional and morphological changes in CD4+ T cells that contribute to HIV-1 pathogenesis such as delay in T-cell proliferation and protection against FasL-mediated apoptosis. But the precise mechanism by which Tat produces these changes remains unknown. We analyzed how the stable expression of intracellular Tat101 and Tat72 modified the miRNA expression profile in Jurkat cells and if this correlated with changes in apoptotic pathways and cell cycle observed in Tat-expressing cells. Specifically, the enhanced expression of hsa-miR-21 and hsa-miR-222 in Jurkat-Tat101 cells was associated with the reduced expression of target mRNAs encoding proteins related to apoptosis and cell cycle such as PTEN, PDCD4 and CDKN1B. We developed Jurkat cells with stable expression of hsa-miR-21 or hsa-miR-222 and observed a similar pattern to Jurkat-Tat101 in resistance to FasL-mediated apoptosis, cell cycle arrest in G2/M and altered cell morphology. Consequently, upregulation of hsa-miR-21 and hsa-miR-222 by Tat may contribute to protect against apoptosis and to anergy observed in HIV-infected CD4+ T cells.
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7
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Qi L, Zhang J, He T, Huo Y, Zhang ZQ. Probing interaction of a fluorescent ligand with HIV TAR RNA. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 173:93-98. [PMID: 27611591 DOI: 10.1016/j.saa.2016.08.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/15/2016] [Accepted: 08/29/2016] [Indexed: 06/06/2023]
Abstract
Trans-activator of Transcription (Tat) antagonists could block the interaction between Tat protein and its target, trans-activation responsive region (TAR) RNA, to inhibit Tat function and prevent human immunodeficiency virus type 1 (HIV-1) replication. For the first time, a small fluorescence ligand, ICR 191, was found to interact with TAR RNA at the Tat binding site and compete with Tat. It was also observed that the fluorescence of ICR 191 could be quenched when binding to TAR RNA and recovered when discharged via competition with Tat peptide or a well-known Tat inhibitor, neomycin B. The binding parameters of ICR 191 to TAR RNA were determined through theoretical calculations. Mass spectrometry, circular dichroism and molecular docking were used to further confirm the interaction of ICR 191 with TAR RNA. Inspired by these discoveries, a primary fluorescence model for the discovery of Tat antagonists was built using ICR 191 as a fluorescence indicator and the feasibility of this model was evaluated. This ligand-RNA interaction could provide a new strategy for research aimed at discovering Tat antagonists.
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MESH Headings
- Aminacrine/analogs & derivatives
- Aminacrine/chemistry
- Aminacrine/metabolism
- Aminacrine/pharmacology
- Binding, Competitive
- Circular Dichroism
- Drug Evaluation, Preclinical/methods
- Fluorescent Dyes/chemistry
- Fluorescent Dyes/metabolism
- Framycetin/chemistry
- Framycetin/metabolism
- HIV Long Terminal Repeat
- Models, Molecular
- Molecular Docking Simulation
- RNA, Viral/chemistry
- RNA, Viral/metabolism
- Spectrometry, Fluorescence
- Spectrometry, Mass, Electrospray Ionization
- tat Gene Products, Human Immunodeficiency Virus/antagonists & inhibitors
- tat Gene Products, Human Immunodeficiency Virus/chemistry
- tat Gene Products, Human Immunodeficiency Virus/metabolism
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Affiliation(s)
- Liang Qi
- Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China; Key Laboratory of Medicinal Resources and Natural Pharmaceutical Chemistry (Shaanxi Normal University), Ministry of Education, Xi'an 710062, China
| | - Jing Zhang
- Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China
| | - Tian He
- Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China
| | - Yuan Huo
- Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China
| | - Zhi-Qi Zhang
- Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China; Key Laboratory of Medicinal Resources and Natural Pharmaceutical Chemistry (Shaanxi Normal University), Ministry of Education, Xi'an 710062, China.
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8
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Hayash T. Preventive effect of ascorbic acid against biological function of human immunodeficiency virus trans-activator of transcription. JOURNAL OF COMPLEMENTARY MEDICINE RESEARCH 2016; 5:205-9. [PMID: 27104044 PMCID: PMC4835998 DOI: 10.5455/jice.20160316010322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/16/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Takuma Hayash
- Department of Immunology and Infectious Disease, Shinshu University School of Medicine, Japan
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Rodríguez-Mora S, Mateos E, Moran M, Martín MÁ, López JA, Calvo E, Terrón MC, Luque D, Muriaux D, Alcamí J, Coiras M, López-Huertas MR. Intracellular expression of Tat alters mitochondrial functions in T cells: a potential mechanism to understand mitochondrial damage during HIV-1 replication. Retrovirology 2015; 12:78. [PMID: 26376973 PMCID: PMC4571071 DOI: 10.1186/s12977-015-0203-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 08/26/2015] [Indexed: 01/22/2023] Open
Abstract
Background HIV-1 replication results in mitochondrial damage that is enhanced during antiretroviral therapy (ART). The onset of HIV-1 replication is regulated by viral protein Tat, a 101-residue protein codified by two exons that elongates viral transcripts. Although the first exon of Tat (aa 1–72) forms itself an active protein, the presence of the second exon (aa 73–101) results in a more competent transcriptional protein with additional functions. Results Mitochondrial overall functions were analyzed in Jurkat cells stably expressing full-length Tat (Tat101) or one-exon Tat (Tat72). Representative results were confirmed in PBLs transiently expressing Tat101 and in HIV-infected Jurkat cells. The intracellular expression of Tat101 induced the deregulation of metabolism and cytoskeletal proteins which remodeled the function and distribution of mitochondria. Tat101 reduced the transcription of the mtDNA, resulting in low
ATP production. The total amount of mitochondria increased likely to counteract their functional impairment. These effects were enhanced when Tat second exon was expressed. Conclusions Intracellular Tat altered mtDNA transcription, mitochondrial content and distribution in CD4+ T cells. The importance of Tat second exon in non-transcriptional functions was confirmed. Tat101 may be responsible for mitochondrial dysfunctions found in HIV-1 infected patients. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0203-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sara Rodríguez-Mora
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - Elena Mateos
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - María Moran
- Laboratorio de Enfermedades Raras: mitocondriales y neuromusculares, Instituto de Investigación Hospital 12 de Octubre, "i + 12", Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) U723, Madrid, Spain.
| | - Miguel Ángel Martín
- Laboratorio de Enfermedades Raras: mitocondriales y neuromusculares, Instituto de Investigación Hospital 12 de Octubre, "i + 12", Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) U723, Madrid, Spain.
| | - Juan Antonio López
- Unidad de Proteómica, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain.
| | - Enrique Calvo
- Unidad de Proteómica, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain.
| | - María Carmen Terrón
- Unidad de Microscopía Electrónica y Confocal, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - Daniel Luque
- Unidad de Microscopía Electrónica y Confocal, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - Delphine Muriaux
- Unité de Virologie Humaine - INSERM U758/École Normale Supérieure, Lyon, France. .,Laboratoire de Domaines Membranaires et Assemblage Viral, Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé, Montpellier, France.
| | - José Alcamí
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - Mayte Coiras
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.
| | - María Rosa López-Huertas
- Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain. .,Unité de Virologie Humaine - INSERM U758/École Normale Supérieure, Lyon, France.
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10
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Su Y, Deng G, Gai Y, Li Y, Gao Y, Du J, Geng Y, Chen Q, Qiao W. Comparative functional analysis of Jembrana disease virus Tat protein on lentivirus long terminal repeat promoters: evidence for flexibility at its N-terminus. Virol J 2009; 6:179. [PMID: 19860923 PMCID: PMC2775740 DOI: 10.1186/1743-422x-6-179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2009] [Accepted: 10/28/2009] [Indexed: 11/11/2022] Open
Abstract
Background Jembrana disease virus (JDV) encodes a potent regulatory protein Tat that strongly stimulates viral expression by transactivating the long terminal repeat (LTR) promoter. JDV Tat (jTat) promotes the transcription from its own LTR as well as non-cognate LTRs, by recruiting host transcription factors and facilitating transcriptional elongation. Here, we compared the sequence requirements of jTat for transactivation of JDV, bovine immunodeficiency virus (BIV) and human immunodeficiency virus (HIV) LTRs. Results In this study, we identified the minimal protein sequence for LTR activation using jTat truncation mutants. We found that jTat N-terminal residues were indispensable for transactivating the HIV LTR. In contrast, transactivation of BIV and JDV LTRs depended largely on an arginine-rich motif and some flanking residues. Competitive inhibition assay and knockdown analysis showed that P-TEFb was required for jTat-mediated LTR transactivation, and a mammalian two-hybrid assay revealed the robust interaction of jTat with cyclin T1. In addition, HIV LTR transactivation was largely affected by fusion protein at the jTat N-terminus despite the fact that the cyclin T1-binding affinity was not altered. Furthermore, the jTat N-terminal sequence enabled HIV Tat to transactivate BIV and JDV LTRs, suggesting the flexibility at the jTat N-terminus. Conclusion This study showed the distinct sequence requirements of jTat for HIV, BIV and JDV LTR activation. Residues responsible for interaction with cyclin T1 and transactivation response element are the key determinants for transactivation of its cognate LTR. N-terminal residues in jTat may compensate for transactivation of the HIV LTR, based on the flexibility.
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Affiliation(s)
- Yang Su
- Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education), College of Life Sciences, Nankai University, Tianjin 300071, China.
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11
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Coiras M, Camafeita E, Ureña T, López JA, Caballero F, Fernández B, López-Huertas MR, Pérez-Olmeda M, Alcamí J. Modifications in the human T cell proteome induced by intracellular HIV-1 Tat protein expression. Proteomics 2008; 6 Suppl 1:S63-73. [PMID: 16526095 DOI: 10.1002/pmic.200500437] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of the human immunodeficiency virus type 1 (HIV-1) Tat protein on cellular gene expression were analysed using a Jurkat cell line that was stably transfected with tat gene in a doxycycline-repressible expression system. Expressed Tat protein (aa 1-101) was proved to present basically a nuclear localisation, and to be fully functional to induce HIV LTR transactivation. Tat expression also resulted in protection from Tunicamycin-induced apoptosis as determined by DNA staining and TUNEL assays. We applied proteomics methods to investigate changes in differential protein expression in the transfected Jurkat-Tat cells. Protein identification was performed using 2-D DIGE followed by MS analysis. We identified the down-regulation of several cytoskeletal proteins such as actin, beta-tubulin, annexin II, as well as gelsolin, cofilin and the Rac/Rho-GDI complex. Down-expression of these proteins could be involved in the survival of long-term reservoirs of HIV-infected CD4+ T cells responsible for continuous viral production. In conclusion, in addition to its role in viral mRNA elongation, the proteomic approach has provided insight into the way that Tat modifies host cell gene expression.
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Affiliation(s)
- Mayte Coiras
- AIDS Immunopathology Unit, National Centre of Microbiology, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain
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12
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Hou T, Ray S, Brasier AR. The functional role of an interleukin 6-inducible CDK9.STAT3 complex in human gamma-fibrinogen gene expression. J Biol Chem 2007; 282:37091-102. [PMID: 17956865 DOI: 10.1074/jbc.m706458200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signal transducer and activator of transcription 3 (STAT3) is an IL-6-inducible transcription factor that mediates the hepatic acute phase response (APR). Using gamma-fibrinogen (FBG) as a model of the APR, we investigated the requirement of an IL-6-inducible complex of STAT3 with cyclin-dependent kinase 9 (CDK9) on gamma-FBG expression in HepG2 hepatocarcinoma cells. IL-6 induces rapid nuclear translocation of Tyr-phosphorylated STAT3 that forms a nuclear complex with CDK9 in nondenaturing co-immunoprecipitation and confocal colocalization assays. To further understand this interaction, we found that CDK9-STAT3 binding is mediated via both STAT NH2-terminal modulatory and COOH-terminal transactivation domains. Both IL-6-inducible gamma-FBG reporter gene and endogenous mRNA expression are significantly decreased after CDK9 inhibition using the potent CDK inhibitor, flavopiridol (FP), or specific CDK9 siRNA. Moreover, chromatin immunoprecipitation (ChIP) experiments revealed an IL-6-inducible STAT3 and CDK9 binding to the proximal gamma-FBG promoter as well as increased loading of RNA Pol II and phospho-Ser2 CTD Pol II on the TATA box and coding regions. Finally, FP specifically and efficiently inhibits association of phospho-Ser2 CTD RNA Pol II on the gamma-FBG promoter, indicating that CDK9 kinase activity mediates IL-6-inducible CTD phosphorylation. Our data indicate that IL-6 induces a STAT3.CDK9 complex mediated by bivalent STAT3 domains and CDK9 kinase activity is necessary for licensing Pol II to enter a transcriptional elongation mode. Therefore, disruption of IL-6 signaling by CDK9 inhibitors could be a potential therapeutic strategy for inflammatory disease.
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Affiliation(s)
- Tieying Hou
- Department of Biochemistry, and Sealy Center for Molecular Medicine, University of Texas Medical Branch, Galveston, Texas 77555-1060, USA
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Patsch C, Edenhofer F. Conditional mutagenesis by cell-permeable proteins: potential, limitations and prospects. Handb Exp Pharmacol 2007:203-32. [PMID: 17203657 DOI: 10.1007/978-3-540-35109-2_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The combination of two powerful technologies, the Cre/loxP recombination system and the protein transduction technique, holds great promise for the advancement of biomedical and genome research by enabling precise and rapid control over mutation events. Protein transduction is a recently developed technology to deliver biologically active proteins directly into mammalian cells. It involves the generation of fusion proteins consisting of the cargo molecule to be delivered and a so-called protein transduction domain. Recently, the derivation of cell permeable variants of the DNA recombinase Cre has been reported. Cre is a site-specific recombinase that recognizes 34 base pair loxP sites and has been widely used to genetically engineer mammalian cells in vitro and in vivo. Recombinant cell-permeable Cre recombinase was found to efficiently induce recombination of loxP-modified alleles in various mammalian cell lines. Here we review recent advances in conditional expression and mutagenesis employing cell-permeable Cre proteins. Moreover, this review summarizes recent findings of studies aimed at deciphering the molecular mechanism of the cellular uptake of cell-permeable fusion proteins.
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Affiliation(s)
- C Patsch
- Stem Cell Engineering Group, Institute of Reconstructive Neurobiology, University of Bonn, Life and Brain Center and Hertie Foundation, Sigmund-Freud Strasse 25, 53105 Bonn, Germany
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14
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Wan L, Zhang X, Gunaseelan S, Pooyan S, Debrah O, Leibowitz MJ, Rabson AB, Stein S, Sinko PJ. Novel multi-component nanopharmaceuticals derived from poly(ethylene) glycol, retro-inverso-Tat nonapeptide and saquinavir demonstrate combined anti-HIV effects. AIDS Res Ther 2006; 3:12. [PMID: 16635263 PMCID: PMC1481600 DOI: 10.1186/1742-6405-3-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Accepted: 04/24/2006] [Indexed: 11/10/2022] Open
Abstract
Background Current anti-AIDS therapeutic agents and treatment regimens can provide a dramatically improved quality of life for HIV-positive people, many of whom have no detectable viral load for prolonged periods of time. Despite this, curing AIDS remains an elusive goal, partially due to the occurrence of drug resistance. Since the development of resistance is linked to, among other things, fluctuating drug levels, our long-term goal has been to develop nanotechnology-based drug delivery systems that can improve therapy by more precisely controlling drug concentrations in target cells. The theme of the current study is to investigate the value of combining AIDS drugs and modifiers of cellular uptake into macromolecular conjugates having novel pharmacological properties. Results Bioconjugates were prepared from different combinations of the approved drug, saquinavir, the antiviral agent, R.I.CK-Tat9, the polymeric carrier, poly(ethylene) glycol and the cell uptake enhancer, biotin. Anti-HIV activities were measured in MT-2 cells, an HTLV-1-transformed human lymphoid cell line, infected with HIV-1 strain Vbu 3, while parallel studies were performed in uninfected cells to determine cellular toxicity. For example, R.I.CK-Tat9 was 60 times more potent than L-Tat9 while the addition of biotin resulted in a prodrug that was 2850 times more potent than L-Tat9. Flow cytometry and confocal microscopy studies suggest that variations in intracellular uptake and intracellular localization, as well as synergistic inhibitory effects of SQV and Tat peptides, contributed to the unexpected and substantial differences in antiviral activity. Conclusion Our results demonstrate that highly potent nanoscale multi-drug conjugates with low non-specific toxicity can be produced by combining moieties with anti-HIV agents for different targets onto macromolecules having improved delivery properties.
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Affiliation(s)
- Li Wan
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
| | - Xiaoping Zhang
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
| | - Simi Gunaseelan
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
| | - Shahriar Pooyan
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
| | - Olivia Debrah
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
| | - Michael J Leibowitz
- Department of Molecular Genetics, Microbiology, and Immunology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
- Cancer Institute of New Jersey, New Brunswick, New Jersey 08903-2681, USA
| | - Arnold B Rabson
- Department of Molecular Genetics, Microbiology, and Immunology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
- Cancer Institute of New Jersey, New Brunswick, New Jersey 08903-2681, USA
| | - Stanley Stein
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
- Cancer Institute of New Jersey, New Brunswick, New Jersey 08903-2681, USA
| | - Patrick J Sinko
- Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers University, 160Frelinghuysen Road, Piscataway, New Jersey 08854-0789, USA
- Cancer Institute of New Jersey, New Brunswick, New Jersey 08903-2681, USA
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15
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Barboric M, Zhang F, Besenicar M, Plemenitas A, Peterlin BM. Ubiquitylation of Cdk9 by Skp2 facilitates optimal Tat transactivation. J Virol 2005; 79:11135-41. [PMID: 16103164 PMCID: PMC1193628 DOI: 10.1128/jvi.79.17.11135-11141.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By recruiting the positive transcriptional elongation factor b (P-TEFb) to paused RNA polymerase II, the transactivator Tat stimulates transcriptional elongation of the human immunodeficiency virus type 1 (HIV-1) genome. We found that cyclin-dependent kinase 9 (Cdk9), the catalytic subunit of P-TEFb, is ubiquitylated in vivo. This ubiquitylation depended on the Skp1/Cul1/F-box protein E3 ubiquitin ligase Skp2. Likewise, Tat required Skp2 since its transactivation of the HIV-1 long terminal repeat decreased in primary mouse embryonic fibroblasts, which lacked Skp2. The ubiquitylation of Cdk9 by Skp2 facilitated the formation of the ternary complex between P-TEFb, Tat, and transactivation response element. Thus, our findings underscore the requirement of ubiquitylation for the coactivator function in regulating HIV-1 transcriptional elongation.
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Affiliation(s)
- Matjaz Barboric
- Rosalind Russell Medical Research Center, Department of Medicine, University of California, San Francisco, 94143, USA
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16
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Endo-Munoz L, Warby T, Harrich D, McMillan NAJ. Phosphorylation of HIV Tat by PKR increases interaction with TAR RNA and enhances transcription. Virol J 2005; 2:17. [PMID: 15737233 PMCID: PMC556014 DOI: 10.1186/1743-422x-2-17] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Accepted: 02/28/2005] [Indexed: 11/28/2022] Open
Abstract
Background The interferon (IFN)-induced, dsRNA-dependent serine/threonine protein kinase, PKR, plays a key regulatory role in the IFN-mediated anti-viral response by blocking translation in the infected cell by phosphorylating the alpha subunit of elongation factor 2 (eIF2). The human immunodeficiency virus type 1 (HIV-1) evades the anti-viral IFN response through the binding of one of its major transcriptional regulatory proteins, Tat, to PKR. HIV-1 Tat acts as a substrate homologue for the enzyme, competing with eIF2α, and inhibiting the translational block. It has been shown that during the interaction with PKR, Tat becomes phosphorylated at three residues: serine 62, threonine 64 and serine 68. We have investigated the effect of this phosphorylation on the function of Tat in viral transcription. HIV-1 Tat activates transcription elongation by first binding to TAR RNA, a stem-loop structure found at the 5' end of all viral transcripts. Our results showed faster, greater and stronger binding of Tat to TAR RNA after phosphorylation by PKR. Results We have investigated the effect of phosphorylation on Tat-mediated transactivation. Our results showed faster, greater and stronger binding of Tat to TAR RNA after phosphorylation by PKR. In vitro phosphorylation experiments with a series of bacterial expression constructs carrying the wild-type tat gene or mutants of the gene with alanine substitutions at one, two, or all three of the serine/threonine PKR phosphorylation sites, showed that these were subject to different levels of phosphorylation by PKR and displayed distinct kinetic behaviour. These results also suggested a cooperative role for the phosphorylation of S68 in conjunction with S62 and T64. We examined the effect of phosphorylation on Tat-mediated transactivation of the HIV-1 LTR in vivo with a series of analogous mammalian expression constructs. Co-transfection experiments showed a gradual reduction in transactivation as the number of mutated phosphorylation sites increased, and a 4-fold decrease in LTR transactivation with the Tat triple mutant that could not be phosphorylated by PKR. Furthermore, the transfection data also suggested that the presence of S68 is necessary for optimal Tat-mediated transactivation. Conclusion These results support the hypothesis that phosphorylation of Tat may be important for its function in HIV-1 LTR transactivation.
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Affiliation(s)
- Liliana Endo-Munoz
- Centre for Immunology and Cancer Research, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia
| | - Tammra Warby
- Centre for Immunology and Cancer Research, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia
| | - David Harrich
- Queensland Institute of Medical Research, Royal Brisbane Hospital, Brisbane, Australia
| | - Nigel AJ McMillan
- Centre for Immunology and Cancer Research, University of Queensland, Princess Alexandra Hospital, Brisbane, Australia
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17
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Das C, Edgcomb SP, Peteranderl R, Chen L, Frankel AD. Evidence for conformational flexibility in the Tat-TAR recognition motif of cyclin T1. Virology 2004; 318:306-17. [PMID: 14972556 DOI: 10.1016/j.virol.2003.10.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Revised: 10/08/2003] [Accepted: 10/08/2003] [Indexed: 11/16/2022]
Abstract
Cyclin T1 (CycT1) is a cellular transcription elongation factor that also participates in Tat-mediated activation of several lentiviral promoters. In human immunodeficiency virus (HIV), CycT1 is required for Tat to bind tightly to TAR and interacts in the ternary complex via its Tat-TAR recognition motif (TRM). In the related bovine immunodeficiency virus (BIV), Tat recognizes its cognate TAR element with high affinity and specificity in the absence of CycT1. At both promoters, CycT1 recruits the Cdk9 kinase, which phosphorylates RNA polymerase II to generate processive transcription complexes. To examine the physical properties of CycT1, we purified a functional domain corresponding to residues 1-272 and found that it possesses a stably folded core, as judged by partial proteolysis and circular dichroism experiments. Interestingly, the C-terminal 20 residues corresponding to the TRM appear conformationally flexible or disordered. The TRM of the bovine CycT1 (bCycT1) is similarly sensitive to proteolysis yet differs in sequence from the human protein. In particular, bCycT1 lacks a cysteine at residue 261 known to be critical for HIV but not BIV ternary complex formation, and mutagenesis data are consistent with a proposed role for this cysteine in metal binding. The apparent flexibility of the TRM suggests that conformational rearrangements may accompany formation of CycT1-Tat-TAR ternary complexes and may contribute to different TAR recognition strategies in different lentiviruses.
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Affiliation(s)
- Chandreyee Das
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-2280, USA
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18
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Hwang S, Tamilarasu N, Kibler K, Cao H, Ali A, Ping YH, Jeang KT, Rana TM. Discovery of a small molecule Tat-trans-activation-responsive RNA antagonist that potently inhibits human immunodeficiency virus-1 replication. J Biol Chem 2003; 278:39092-103. [PMID: 12857725 DOI: 10.1074/jbc.m301749200] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antiretroviral therapy to treat AIDS uses molecules that target the reverse transcriptase and protease enzymes of human immunodeficiency virus, type 1 (HIV-1). A major problem associated with these treatments, however, is the emergence of drug-resistant strains. Thus, there is a compelling need to find drugs against other viral targets. One such target is the interaction between Tat, an HIV-1 regulatory protein essential for viral replication, and trans-activation-responsive (TAR) RNA. Here we describe the design and synthesis of an encoded combinatorial library containing 39,304 unnatural small molecules. Using a rapid high through-put screening technology, we identified 59 compounds. Structure-activity relationship studies led to the synthesis of 19 compounds that bind TAR RNA with high affinities. In the presence of a representative Tat-TAR inhibitor (5 microM TR87), we observed potent and sustained suppression of HIV replication in cultured cells over 24 days. The same concentration of this inhibitor did not exhibit any toxicity in cell cultures or in mice. TR87 was also shown to specifically disrupt Tat-TAR binding in vitro and inhibit Tat-mediated transcriptional activation in vitro and in vivo, providing a strong correlation between its activities and inhibition of HIV-1 replication. These results provide a structural scaffold for further development of new drugs, alone or in combination with other drugs, for treatment of HIV-1-infected individuals. Our results also suggest a general strategy for discovering pharmacophores targeting RNA structures that are essential in progression of other infectious, inflammatory, and genetic diseases.
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Affiliation(s)
- Seongwoo Hwang
- Chemical Biology Program, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605-2324, USA
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19
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Lin X, Irwin D, Kanazawa S, Huang L, Romeo J, Yen TSB, Peterlin BM. Transcriptional profiles of latent human immunodeficiency virus in infected individuals: effects of Tat on the host and reservoir. J Virol 2003; 77:8227-36. [PMID: 12857891 PMCID: PMC165222 DOI: 10.1128/jvi.77.15.8227-8236.2003] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The persistence of human immunodeficiency virus (HIV) in optimally treated infected individuals poses a major therapeutic problem. In latently infected cells, one of the observed phenotypes is absent elongation of viral transcription. Thus, the positive elongation factor b (P-TEFb), which is usually recruited by NF-kappaB or Tat, is not present on the HIV long terminal repeat (LTR). Although most attempts to activate these proviruses centered on NF-kappaB, we investigated effects of Tat. To this end, we generated transgenic mice, which secreted a chimera between Tat and the green fluorescent protein from beta cells of the pancreas. This extracellular Tat distributed widely, entered nuclei of resting cells, and specifically transactivated the HIV LTR. No deleterious side effects of Tat were found. Next, we determined that Tat can activate latent proviruses in optimally treated infected individuals. In their cells, T-cell activation or exogenous Tat could induce viral replication equivalently. Thus, P-TEFb could activate the majority of the latent HIV, in this case by Tat.
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Affiliation(s)
- Xin Lin
- Department of Medicine, San Francisco General Hospital, Center for AIDS Research and Department of Pathology, University of California, San Francisco, USA
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20
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Ambrosino C, Palmieri C, Puca A, Trimboli F, Schiavone M, Olimpico F, Ruocco MR, di Leva F, Toriello M, Quinto I, Venuta S, Scala G. Physical and functional interaction of HIV-1 Tat with E2F-4, a transcriptional regulator of mammalian cell cycle. J Biol Chem 2002; 277:31448-58. [PMID: 12055184 DOI: 10.1074/jbc.m112398200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tat protein of the human immunodeficiency virus type-1 (HIV-1) plays a critical role in the regulation of viral transcription and replication. In addition, Tat regulates the expression of a variety of cellular genes and could account for AIDS-associated diseases including Kaposi's Sarcoma and non-Hodgkin's lymphoma by interfering with cellular processes such as proliferation, differentiation, and apoptosis. The molecular mechanisms underlying the pleiotropic activities of Tat may include the generation of functional heterodimers of Tat with cellular proteins. By screening a human B-lymphoblastoid cDNA library in the yeast two-hybrid system, we identified E2F-4, a member of E2F family of transcription factors, as a Tat-binding protein. The interaction between Tat and E2F-4 was confirmed by GST pull-down experiments performed with cellular extracts as well as with in vitro translated E2F-4. The physical association of Tat and E2F-4 was confirmed by in vivo binding experiments where Tat.E2F-4 heterodimers were recovered from Jurkat cells by immunoprecipitation and immunoblotting. By using plasmids expressing mutant forms of Tat and E2F-4, the domains involved in Tat.E2F-4 interaction were identified as the regions encompassing amino acids 1-49 of Tat and amino acids 1-184 of E2F-4. Tat x E2F-4 complexes were shown to bind to E2F cis-regions with increased efficiency compared with E2F-4 alone and to mediate the activity of E2F-dependent promoters including HIV-1 long terminal repeat and cyclin A. The data point to Tat as an adaptor protein that recruits cellular factors such as E2F-4 to exert its multiple biological activities.
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Affiliation(s)
- Concetta Ambrosino
- Department of Clinical and Experimental Medicine, Medical School, University of Catanzaro, 88100 Catanzaro, Italy
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21
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Mujtaba S, He Y, Zeng L, Farooq A, Carlson JE, Ott M, Verdin E, Zhou MM. Structural basis of lysine-acetylated HIV-1 Tat recognition by PCAF bromodomain. Mol Cell 2002; 9:575-86. [PMID: 11931765 DOI: 10.1016/s1097-2765(02)00483-5] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human immunodeficiency virus type 1 (HIV-1) trans-activator protein Tat stimulates transcription of the integrated HIV-1 genome and promotes viral replication in infected cells. Tat transactivation activity is dependent on lysine acetylation and its association with nuclear histone acetyltransferases p300/CBP (CREB binding protein) and p300/CBP-associated factor (PCAF). Here, we show that the bromodomain of PCAF binds specifically to HIV-1 Tat acetylated at lysine 50 and that this interaction competes effectively against HIV-1 TAR RNA binding to the lysine-acetylated Tat. The three-dimensional solution structure of the PCAF bromodomain in complex with a lysine 50-acetylated Tat peptide together with biochemical analyses provides the structural basis for the specificity of this molecular recognition and reveals insights into the differences in ligand selectivity of bromodomains.
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Affiliation(s)
- Shiraz Mujtaba
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York University, New York, NY 10029, USA
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22
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Barboric M, Nissen RM, Kanazawa S, Jabrane-Ferrat N, Peterlin BM. NF-kappaB binds P-TEFb to stimulate transcriptional elongation by RNA polymerase II. Mol Cell 2001; 8:327-37. [PMID: 11545735 DOI: 10.1016/s1097-2765(01)00314-8] [Citation(s) in RCA: 363] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To stimulate transcriptional elongation of HIV-1 genes, the transactivator Tat recruits the positive transcription elongation factor b (P-TEFb) to the initiating RNA polymerase II (RNAPII). We found that the activation of transcription by RelA also depends on P-TEFb. Similar to Tat, RelA activated transcription when tethered to RNA. Moreover, TNF-alpha triggered the recruitment of P-TEFb to the NF-kappaB-regulated IL-8 gene. While the formation of the transcription preinitiation complex (PIC) remained unaffected, DRB, an inhibitor of P-TEFb, prevented RNAPII from elongating on the IL-8 gene. Remarkably, DRB inhibition sensitized cells to TNF-alpha-induced apoptosis. Thus, NF-kappaB requires P-TEFb to stimulate the elongation of transcription and P-TEFb plays an unexpected role in regulating apoptosis.
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Affiliation(s)
- M Barboric
- Howard Hughes Medical Institute Departments of Medicine, Microbiology, and Immunology University of California at San Francisco 94143, USA
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23
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Ping YH, Rana TM. DSIF and NELF interact with RNA polymerase II elongation complex and HIV-1 Tat stimulates P-TEFb-mediated phosphorylation of RNA polymerase II and DSIF during transcription elongation. J Biol Chem 2001; 276:12951-8. [PMID: 11112772 DOI: 10.1074/jbc.m006130200] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Control of transcription elongation requires a complex interplay between the recently discovered positive transcription elongation factor b (P-TEFb) and negative transcription elongation factors, 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole (DRB) sensitivity inducing factors (DSIF) and the negative elongation factor (NELF). Activation of HIV-1 gene expression is regulated by a nascent RNA structure, termed TAR RNA, in concert with HIV-1 Tat protein and these positive and negative elongation factors. We have used a stepwise RNA pol II walking approach and Western blotting to determine the dynamics of interactions between HIV-1 Tat, DSIF/NELF, and the transcription complexes actively engaged in elongation. In addition, we developed an in vitro kinase assay to determine the phosphorylation status of proteins during elongation stages. Our results demonstrate that DSIF/NELF associates with RNA pol II complexes during early transcription elongation and travels with elongation complexes as the nascent RNA is synthesized. Our results also show that HIV-1 Tat protein stimulated DSIF and RNA pol II phosphorylation by P-TEFb during elongation. These findings reveal a molecular mechanism for the negative and positive regulation of transcriptional elongation at the HIV-1 promoter.
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Affiliation(s)
- Y H Ping
- Department of Pharmacology, Robert Wood Johnson Medical School, and Molecular Biosciences Graduate Program at Rutgers University, Piscataway, New Jersey 08854, USA
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24
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Cullen BR. Principles and applications of a Tat-based assay for analyzing specific RNA-protein interactions in mammalian cells. Methods Enzymol 2001; 328:322-9. [PMID: 11075353 DOI: 10.1016/s0076-6879(00)28405-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Affiliation(s)
- B R Cullen
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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25
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Browning CM, Smith MJ, Clark NM, Lane BR, Parada C, Montano M, KewalRamani VN, Littman DR, Essex M, Roeder RG, Markovitz DM. Human GLI-2 is a tat activation response element-independent Tat cofactor. J Virol 2001; 75:2314-23. [PMID: 11160734 PMCID: PMC114814 DOI: 10.1128/jvi.75.5.2314-2323.2001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2000] [Accepted: 12/07/2000] [Indexed: 11/20/2022] Open
Abstract
Zinc finger-containing GLI proteins are involved in the development of Caenorhabditis elegans, Xenopus, Drosophila, zebrafish, mice, and humans. In this study, we show that an isoform of human GLI-2 strongly synergizes with the Tat transactivating proteins of human immunodeficiency virus types 1 and 2 (HIV-1 and -2) and markedly stimulates viral replication. GLI-2 also synergizes with the previously described Tat cofactor cyclin T1 to stimulate Tat function. Surprisingly, GLI-2/Tat synergy is not dependent on either a typical GLI DNA binding site or an intact Tat activation response element but does require an intact TATA box. Thus, GLI-2/Tat synergy results from a mechanism of action which is novel both for a GLI protein and for a Tat cofactor. These findings link the GLI family of transcriptional and developmental regulatory proteins to Tat function and HIV replication.
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Affiliation(s)
- C M Browning
- Department of Microbiology and Immunology, Ann Arbor, Michigan 48109-0640,USA
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26
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Landt SG, Tan R, Frankel AD. Screening RNA-binding libraries using Tat-fusion system in mammalian cells. Methods Enzymol 2001; 318:350-63. [PMID: 10889998 DOI: 10.1016/s0076-6879(00)18062-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Affiliation(s)
- S G Landt
- Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA
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27
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Abstract
Equine infectious anemia virus (EIAV) is an ungulate lentivirus that is related to human immunodeficiency virus (HIV). Much of the understanding of lentiviral gene regulation comes from studies using HIV. HIV studies have provided insights into molecular regulation of EIAV expression; however, much of the regulation of EIAV expression stands in stark contrast to that of HIV. This review provides an overview of the current state of knowledge of EIAV regulation by comparing and contrasting EIAV gene regulation to HIV. The role of EIAV gene regulation is discussed in relation to EIAV pathogenesis.
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Affiliation(s)
- W Maury
- Department of Microbiology, University of South Dakota School of Medicine, Vermillion 57069, USA.
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28
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Zhou M, Halanski MA, Radonovich MF, Kashanchi F, Peng J, Price DH, Brady JN. Tat modifies the activity of CDK9 to phosphorylate serine 5 of the RNA polymerase II carboxyl-terminal domain during human immunodeficiency virus type 1 transcription. Mol Cell Biol 2000; 20:5077-86. [PMID: 10866664 PMCID: PMC85957 DOI: 10.1128/mcb.20.14.5077-5086.2000] [Citation(s) in RCA: 205] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tat stimulates human immunodeficiency virus type 1 (HIV-1) transcriptional elongation by recruitment of carboxyl-terminal domain (CTD) kinases to the HIV-1 promoter. Using an immobilized DNA template assay, we have analyzed the effect of Tat on kinase activity during the initiation and elongation phases of HIV-1 transcription. Our results demonstrate that cyclin-dependent kinase 7 (CDK7) (TFIIH) and CDK9 (P-TEFb) both associate with the HIV-1 preinitiation complex. Hyperphosphorylation of the RNA polymerase II (RNAP II) CTD in the HIV-1 preinitiation complex, in the absence of Tat, takes place at CTD serine 2 and serine 5. Analysis of preinitiation complexes formed in immunodepleted extracts suggests that CDK9 phosphorylates serine 2, while CDK7 phosphorylates serine 5. Remarkably, in the presence of Tat, the substrate specificity of CDK9 is altered, such that the kinase phosphorylates both serine 2 and serine 5. Tat-induced CTD phosphorylation by CDK9 is strongly inhibited by low concentrations of 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole, an inhibitor of transcription elongation by RNAP II. Analysis of stalled transcription elongation complexes demonstrates that CDK7 is released from the transcription complex between positions +14 and +36, prior to the synthesis of transactivation response (TAR) RNA. In contrast, CDK9 stays associated with the complex through +79. Analysis of CTD phosphorylation indicates a biphasic modification pattern, one in the preinitiation complex and the other between +36 and +79. The second phase of CTD phosphorylation is Tat-dependent and TAR-dependent. These studies suggest that the ability of Tat to increase transcriptional elongation may be due to its ability to modify the substrate specificity of the CDK9 complex.
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Affiliation(s)
- M Zhou
- Virus Tumor Biology Section, LRBGE, Division of Basic Sciences, National Cancer Institute, Bethesda, Maryland 20892, USA
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29
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Bogerd HP, Wiegand HL, Bieniasz PD, Cullen BR. Functional differences between human and bovine immunodeficiency virus Tat transcription factors. J Virol 2000; 74:4666-71. [PMID: 10775603 PMCID: PMC111987 DOI: 10.1128/jvi.74.10.4666-4671.2000] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional transactivation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) promoter element by the essential viral Tat protein requires recruitment of positive transcription elongation factor b (P-TEFb) to the viral TAR RNA target. The recruitment of P-TEFb, which has been proposed to be necessary and sufficient for activation of viral gene expression, is mediated by the highly cooperative interaction of Tat and cyclin T1, an essential component of P-TEFb, with the HIV-1 TAR element. Species, such as rodents, that encode cyclin T1 variants that are unable to support TAR binding by the Tat-cyclin T1 heterodimer are also unable to support HIV-1 Tat function. In contrast, we here demonstrate that the bovine immunodeficiency virus (BIV) Tat protein is fully able to bind to BIV TAR both in vivo and in vitro in the absence of any cellular cofactor. Nevertheless, BIV Tat can specifically recruit cyclin T1 to the BIV TAR element, and this recruitment is as essential for BIV Tat function as it is for HIV-1 Tat activity. However, because the cyclin T1 protein does not contribute to TAR binding, BIV Tat is able to function effectively in cells from several species that do not support HIV-1 Tat function. Thus, BIV Tat, while apparently dependent on the same cellular cofactor as the Tat proteins encoded by other lentiviruses, is nevertheless unique in terms of the mechanism used to recruit the BIV Tat-cyclin T1 complex to the viral LTR promoter.
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Affiliation(s)
- H P Bogerd
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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30
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Affiliation(s)
- D H Price
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA.
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31
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Albrecht TR, Lund LH, Garcia-Blanco MA. Canine cyclin T1 rescues equine infectious anemia virus tat trans-activation in human cells. Virology 2000; 268:7-11. [PMID: 10683321 DOI: 10.1006/viro.1999.0141] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human immunodeficiency virus-1 Tat protein and human Cyclin T1 mediate transcriptional activation by enhancing the elongation efficiency of RNA polymerase II. Activation of transcription of the related equine infectious anemia virus (EIAV) requires a similar protein known as eTat, which does not function in human cells. Expression of equine Cyclin T1 in human cells rescues eTat function, suggesting a general mechanism of transcription activation among lentiviruses. Here we present the cloning of Cyclin T1 from canine D17 osteosarcoma cells, which support EIAV transactivation, and show that canine Cyclin T1 confers eTat transactivation to human cells. A two-amino-acid change, from 79-proline-glycine-80 to 79-histidine-arginine-80, confers on the human Cyclin T1 the ability to cooperate with eTat in transcriptional activation. These findings suggested that the regions of Cyclin T1 that interact with lentiviral Tat proteins and TAR RNA elements form an extended domain, which very likely has a conserved fold.
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Affiliation(s)
- T R Albrecht
- Department of Genetics, Duke University Medical Center, Durham, North Carolina, 27710, USA
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32
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Taube R, Fujinaga K, Irwin D, Wimmer J, Geyer M, Peterlin BM. Interactions between equine cyclin T1, Tat, and TAR are disrupted by a leucine-to-valine substitution found in human cyclin T1. J Virol 2000; 74:892-8. [PMID: 10623752 PMCID: PMC111610 DOI: 10.1128/jvi.74.2.892-898.2000] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional transactivators (Tat) from human immunodeficiency and equine infectious anemia viruses (HIV and EIAV) interact with their transactivation response elements (TAR) to increase the rates of viral transcription. Whereas the human cyclin T1 is required for the binding of Tat to TAR from HIV, it is unknown how Tat from EIAV interacts with its TAR. Furthermore, Tat from EIAV functions in equine and canine cells but not in human cells. In this study, we present sequences of cyclins T1 from horse and dog and demonstrate that their N-terminal 300 residues rescue the transactivation of Tat from EIAV in human cells. Although human and equine cyclins T1 bind to this Tat, only the equine cyclin T1 supports the binding of Tat to TAR from EIAV. Finally, a reciprocal exchange of the valine for the leucine at position 29 in human and equine cyclins T1, respectively, renders the human cyclin T1 active and the equine cyclin T1 inactive for Tat transactivation from EIAV. Thus, the collaboration between a specific cyclin T1 and Tat for their high-affinity interaction with TAR is a common theme of lentiviral transactivation.
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Affiliation(s)
- R Taube
- Howard Hughes Medical Institute, Departments of Medicine, Microbiology, and Immunology, University of California at San Francisco, San Francisco, California 94143-0703, USA
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33
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Taube R, Fujinaga K, Wimmer J, Barboric M, Peterlin BM. Tat transactivation: a model for the regulation of eukaryotic transcriptional elongation. Virology 1999; 264:245-53. [PMID: 10562489 DOI: 10.1006/viro.1999.9944] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- R Taube
- Department of Medicine, University of California, San Francisco, San Francisco, California, 94143-0703, USA
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34
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Bieniasz PD, Grdina TA, Bogerd HP, Cullen BR. Recruitment of cyclin T1/P-TEFb to an HIV type 1 long terminal repeat promoter proximal RNA target is both necessary and sufficient for full activation of transcription. Proc Natl Acad Sci U S A 1999; 96:7791-6. [PMID: 10393900 PMCID: PMC22140 DOI: 10.1073/pnas.96.14.7791] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transcriptional activation of the HIV type 1 (HIV-1) long terminal repeat (LTR) promoter element by the viral Tat protein is an essential step in the HIV-1 life cycle. Tat function is mediated by the TAR RNA target element encoded within the LTR and is known to require the recruitment of a complex consisting of Tat and the cyclin T1 (CycT1) component of positive transcription elongation factor b (P-TEFb) to TAR. Here, we demonstrate that both TAR and Tat become entirely dispensable for activation of the HIV-1 LTR promoter when CycT1/P-TEFb is artificially recruited to a heterologous promoter proximal RNA target. The level of activation observed was indistinguishable from the level induced by Tat and was neither inhibited nor increased when Tat was expressed in trans. Activation by artificially recruited CycT1 depended on the ability to bind the CDK9 component of P-TEFb. In contrast, although binding to both Tat and TAR was essential for the ability of CycT1 to act as a Tat cofactor, these interactions became dispensable when CycT1 was directly recruited to the LTR. Importantly, activation of the LTR both by Tat and by directly recruited CycT1 was found to be at the level of transcription elongation. Together, these data demonstrate that recruitment of CycT1/P-TEFb to the HIV-1 LTR is fully sufficient to activate this promoter element and imply that the sole role of the Tat/TAR axis in viral transcription is to permit the recruitment of CycT1/P-TEFb.
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Affiliation(s)
- P D Bieniasz
- Howard Hughes Medical Institute and Department of Genetics, Box 3025, Duke University Medical Center, Durham, NC 27710, USA
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35
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Bieniasz PD, Grdina TA, Bogerd HP, Cullen BR. Analysis of the effect of natural sequence variation in Tat and in cyclin T on the formation and RNA binding properties of Tat-cyclin T complexes. J Virol 1999; 73:5777-86. [PMID: 10364329 PMCID: PMC112638 DOI: 10.1128/jvi.73.7.5777-5786.1999] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The biological activity of the human immunodeficiency virus type 1 (HIV-1) Tat (Tat1) transcriptional activator requires the recruitment of a Tat1-CyclinT1 (CycT1) complex to the TAR RNA target encoded within the viral long terminal repeat (LTR). While other primate immunodeficiency viruses, such as HIV-2 and mandrill simian immunodeficiency virus (SIVmnd), also encode Tat proteins that activate transcription via RNA targets, these proteins differ significantly, both from each other and from Tat1, in terms of their ability to activate transcription directed by LTR promoter elements found in different HIV and SIV isolates. Here, we show that CycT1 also serves as an essential cofactor for HIV-2 Tat (Tat2) and SIVmnd Tat (Tat-M) function. Moreover, the CycT1 complex formed by each Tat protein displays a distinct RNA target specificity that accurately predicts the level of activation observed with a particular LTR. While Tat2 and Tat-M share the ability of Tat1 to bind to CycT1, they differ from Tat1 in that they are also able to bind to the related but distinct CycT2. However, the resultant Tat-CycT2 complexes fail to bind TAR and are therefore abortive. Surprisingly, mutation of a single residue in CycT2 (asparagine 260 to cysteine) rescues the ability of CycT2 to bind Tat1 and also activates not only TAR binding by all three Tat-CycT2 complexes but also Tat function. Therefore, the RNA target specificity of different Tat-CycT1 complexes is modulated by natural sequence variation in both the viral Tat transcriptional activator and in the host cell CycT molecule recruited by Tat. Further, the RNA target specificity of the resultant Tat-CycT1 complex accurately predicts the ability of that complex to activate transcription from a given LTR promoter element.
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Affiliation(s)
- P D Bieniasz
- Howard Hughes Medical Institute and Department of Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA
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36
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Bieniasz PD, Grdina TA, Bogerd HP, Cullen BR. Highly divergent lentiviral Tat proteins activate viral gene expression by a common mechanism. Mol Cell Biol 1999; 19:4592-9. [PMID: 10373508 PMCID: PMC84257 DOI: 10.1128/mcb.19.7.4592] [Citation(s) in RCA: 35] [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
The human immunodeficiency virus type 1 (HIV-1) Tat protein (hTat) activates transcription initiated at the viral long terminal repeat (LTR) promoter by a unique mechanism requiring recruitment of the human cyclin T1 (hCycT1) cofactor to the viral TAR RNA target element. While activation of equine infectious anemia virus (EIAV) gene expression by the EIAV Tat (eTat) protein appears similar in that the target element is a promoter proximal RNA, eTat shows little sequence homology to hTat, does not activate the HIV-1 LTR, and is not active in human cells that effectively support hTat function. To address whether eTat and hTat utilize similar or distinct mechanisms of action, we have cloned the equine homolog of hCycT1 (eCycT1) and examined whether it is required to mediate eTat function. Here, we report that expression of eCycT1 in human cells fully rescues eTat function and that eCycT1 and eTat form a protein complex that specifically binds to the EIAV, but not the HIV-1, TAR element. While hCycT1 is also shown to interact with eTat, the lack of eTat function in human cells is explained by the failure of the resultant protein complex to bind to EIAV TAR. Critical sequences in eCycT1 required to support eTat function are located very close to the amino terminus, i.e., distal to the HIV-1 Tat-TAR interaction motif previously identified in the hCycT1 protein. Together, these data provide a molecular explanation for the species tropism displayed by eTat and demonstrate that highly divergent lentiviral Tat proteins activate transcription from their cognate LTR promoters by essentially identical mechanisms.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Cell Line, Transformed
- Cloning, Molecular
- Cyclin T
- Cyclins/metabolism
- Gene Expression Regulation, Viral
- Gene Products, tat/genetics
- Gene Products, tat/metabolism
- HIV-1/genetics
- HIV-1/metabolism
- Horses
- Humans
- Infectious Anemia Virus, Equine/genetics
- Infectious Anemia Virus, Equine/metabolism
- Mice
- Molecular Sequence Data
- RNA, Viral
- Sequence Homology, Amino Acid
- Terminal Repeat Sequences
- tat Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- P D Bieniasz
- Department of Genetics and Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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37
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Garber ME, Wei P, Jones KA. HIV-1 Tat interacts with cyclin T1 to direct the P-TEFb CTD kinase complex to TAR RNA. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 1999; 63:371-80. [PMID: 10384302 DOI: 10.1101/sqb.1998.63.371] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- M E Garber
- Regulatory Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA
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38
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Ivanov D, Kwak YT, Nee E, Guo J, García-Martínez LF, Gaynor RB. Cyclin T1 domains involved in complex formation with Tat and TAR RNA are critical for tat-activation. J Mol Biol 1999; 288:41-56. [PMID: 10329125 DOI: 10.1006/jmbi.1999.2663] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tat activates transcription from the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) by increasing the processivity of RNA polymerase II. Recently, it has been demonstrated that the cellular kinase CDK9 and its binding partner cyclin T1 are involved in regulating transcriptional elongation and tat-activation. Cyclin T1, CDK9 and Tat bind as a complex to elements in TAR RNA that are required for tat-activation. Here, we used cyclin T1 mutants to define domains in this protein that bind to both CDK9 and Tat and are involved in stimulating tat-activation. The region of cyclin T1 extending from amino acid residues 1 to 263 is necessary for complex formation with Tat bound to TAR RNA and for stimulation of tat-activation in murine cells that are normally poorly responsive to the actions of Tat. In contrast, a smaller region of cyclin T1 was required to bind to CDK9 and stimulate its kinase activity. Recombinant cyclin T1 and CDK9 stimulated both basal and tat-induced in vitro transcriptional elongation from the HIV-1 LTR. The effects of Tat on transcriptional elongation may be mediated by its ability to increase CDK9 phosphorylation of the RNA polymerase II C-terminal domain. These results demonstrate that cyclin T1 interactions with Tat and TAR RNA are critical for activation of HIV-1 gene expression.
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Affiliation(s)
- D Ivanov
- Division of Hematology-Oncology, Department of Medicine, Harold Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, 75235-8594, USA
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39
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Kwak YT, Ivanov D, Guo J, Nee E, Gaynor RB. Role of the human and murine cyclin T proteins in regulating HIV-1 tat-activation. J Mol Biol 1999; 288:57-69. [PMID: 10329126 DOI: 10.1006/jmbi.1999.2664] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human cyclin T1 markedly stimulates tat-activation in rodent cells which are normally poorly responsive to the effects of Tat. This result suggests that there are likely to be critical differences in the murine and human cyclin T1 proteins. Here, we analyzed the role of the murine and human cyclin T1 proteins in addition to the human cyclin T2a and T2b proteins on regulating tat-activation. Only the human cyclin T1 protein efficiently formed a complex with Tat bound to TAR RNA. This difference in function was due to the presence of a cysteine residue in human cyclin T1 at position 261 rather than a tyrosine or asparagine residue which are found in the murine cyclin T1 protein and the human cyclin T2a and T2b proteins, respectively. A mouse cyclin T1 protein containing a substitution of tyrosine residue 261 with a cysteine residue, was able to interact with Tat and stimulate tat-transactivation in rodent cells. Likewise, substitution of a cysteine residue for an asparagine residue at position 260 of the cyclin T2a and T2b proteins also resulted in their ability to interact with Tat and stimulate tat-activation in rodent cells. The data indicate that a specific residue in the cyclin T proteins is required for their in vitro interaction with Tat and their ability to stimulate in vivo tat-activation.
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Affiliation(s)
- Y T Kwak
- Division of Hematology-Oncology, Department of Medicine, Harold Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, 75235-8594, USA
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40
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Huq I, Ping YH, Tamilarasu N, Rana TM. Controlling human immunodeficiency virus type 1 gene expression by unnatural peptides. Biochemistry 1999; 38:5172-7. [PMID: 10213623 DOI: 10.1021/bi982638h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Small unnatural peptides that target specific RNA structures have the potential to control biological processes. RNA-protein interactions are important in many cellular functions, including transcription, RNA splicing, and translation. One example of such interactions is the mechanism of trans-activation of human immunodeficiency virus type 1 (HIV-1) gene expression that requires the interaction of Tat protein with the trans-activation responsive region (TAR) RNA, a 59-base stem-loop structure located at the 5'-end of all nascent HIV-1 transcripts. We report here a synthetic peptide derived from Tat sequence (37-72), containing all D-amino acids, that binds in the major groove of TAR RNA and interferes with transcriptional activation by Tat protein in vitro and in HeLa cells. Our results indicate that unnatural peptides can inhibit the transcription of specific genes regulated by RNA-protein interactions.
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Affiliation(s)
- I Huq
- Department of Pharmacology, Robert Wood Johnson Medical School, Molecular Biosciences Graduate Program, Rutgers University, Piscataway, New Jersey 08854, USA
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41
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Liu Y, Suñé C, Garcia-Blanco MA. Human immunodeficiency virus type 1 Tat-dependent activation of an arrested RNA polymerase II elongation complex. Virology 1999; 255:337-46. [PMID: 10069959 DOI: 10.1006/viro.1998.9585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human immunodeficiency virus type 1 (HIV-1) Tat protein is a transcriptional activator that is essential for efficient viral gene expression and replication. Tat increases the level of full-length transcripts from the HIV-1 promoter by dramatically enhancing the elongation efficiency of the RNA polymerase II complexes assembled on this promoter. Tat could potentially activate the transcription machinery during initiation, elongation, or both. We used an immobilized HIV-1 promoter template with a reversible lac repressor (LacR) elongation block inserted downstream to dissect the stages in transcription affected by Tat. Transcription complexes assembled in the absence of Tat and blocked by LacR cannot be activated by incubation with Tat alone. These complexes can, however, be activated if Tat is added in combination with cellular factors. In this system, Tat also promoted the assembly of preinitiation complexes capable of elongating efficiently, suggesting that Tat can associate with transcription complex at an early stage. These data indicate that Tat can activate elongation of RNA polymerase by modifying an already elongating transcription complex. The data also suggest the possibility that Tat can interact with initiation complexes.
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Affiliation(s)
- Y Liu
- Levine Science Research Center, Duke University Medical Center, Durham, North Carolina, 27710, USA
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42
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Fujinaga K, Taube R, Wimmer J, Cujec TP, Peterlin BM. Interactions between human cyclin T, Tat, and the transactivation response element (TAR) are disrupted by a cysteine to tyrosine substitution found in mouse cyclin T. Proc Natl Acad Sci U S A 1999; 96:1285-90. [PMID: 9990016 PMCID: PMC15455 DOI: 10.1073/pnas.96.4.1285] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The transcriptional transactivator Tat from HIV binds to the transactivation response element (TAR) RNA to increase rates of elongation of viral transcription. Human cyclin T supports these interactions between Tat and TAR. In this study, we report the sequence of mouse cyclin T and identify the residues from positions 1 to 281 in human cyclin T that bind to Tat and TAR. Mouse cyclin T binds to Tat weakly and is unable to facilitate interactions between Tat and TAR. Reciprocal exchanges of the cysteine and tyrosine at position 261 in human and mouse cyclin T proteins also render human cyclin T inactive and mouse cyclin T active. These findings reveal the molecular basis for the restriction of Tat transactivation in rodent cells.
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Affiliation(s)
- K Fujinaga
- Howard Hughes Medical Institute, Departments of Medicine, Microbiology, and Immunology, University of California, San Francisco, CA 94143-0703, USA
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43
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Bieniasz PD, Grdina TA, Bogerd HP, Cullen BR. Recruitment of a protein complex containing Tat and cyclin T1 to TAR governs the species specificity of HIV-1 Tat. EMBO J 1998; 17:7056-65. [PMID: 9843510 PMCID: PMC1171053 DOI: 10.1093/emboj/17.23.7056] [Citation(s) in RCA: 218] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Human cyclin T1 (hCycT1), a major subunit of the essential elongation factor P-TEFb, has been proposed to act as a cofactor for human immunodeficiency virus type 1 (HIV-1) Tat. Here, we show that murine cyclin T1 (mCycT1) binds the activation domain of HIV-1 Tat but, unlike hCycT1, cannot mediate Tat function because it cannot be recruited efficiently to TAR. In fact, overexpression of mCycT1, but not hCycT1, specifically inhibits Tat-TAR function in human cells. This discordant phenotype results from a single amino acid difference between hCycT1 and mCycT1, a tyrosine in place of a cysteine at residue 261. These data indicate that the ability of Tat to recruit CycT1/P-TEFb to TAR determines the species restriction of HIV-1 Tat function in murine cells and therefore demonstrate that this recruitment is a critical function of the Tat protein.
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Affiliation(s)
- P D Bieniasz
- Howard Hughes Medical Institute and Department of Genetics, Box 3025, Room 426, CARL Building, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
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44
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Garber ME, Wei P, KewalRamani VN, Mayall TP, Herrmann CH, Rice AP, Littman DR, Jones KA. The interaction between HIV-1 Tat and human cyclin T1 requires zinc and a critical cysteine residue that is not conserved in the murine CycT1 protein. Genes Dev 1998; 12:3512-27. [PMID: 9832504 PMCID: PMC317238 DOI: 10.1101/gad.12.22.3512] [Citation(s) in RCA: 356] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/1998] [Accepted: 09/30/1998] [Indexed: 11/24/2022]
Abstract
HIV-1 Tat activates transcription through binding to human cyclin T1, a regulatory subunit of the TAK/P-TEFb CTD kinase complex. Here we show that the cyclin domain of hCycT1 is necessary and sufficient to interact with Tat and promote cooperative binding to TAR RNA in vitro, as well as mediate Tat transactivation in vivo. A Tat:TAR recognition motif (TRM) was identified at the carboxy-terminal edge of the cyclin domain, and we show that hCycT1 can interact simultaneously with Tat and CDK9 on TAR RNA in vitro. Alanine-scanning mutagenesis of the hCycT1 TRM identified residues that are critical for the interaction with Tat and others that are required specifically for binding of the complex to TAR RNA. Interestingly, we find that the interaction between Tat and hCycT1 requires zinc as well as essential cysteine residues in both proteins. Cloning and characterization of the murine CycT1 protein revealed that it lacks a critical cysteine residue (C261) and forms a weak, zinc-independent complex with HIV-1 Tat that greatly reduces binding to TAR RNA. A point mutation in mCycT1 (Y261C) restores high-affinity, zinc-dependent binding to Tat and TAR in vitro, and rescues Tat transactivation in vivo. Although overexpression of hCycT1 in NIH3T3 cells strongly enhances transcription from an integrated proviral promoter, we find that this fails to overcome all blocks to productive HIV-1 infection in murine cells.
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Affiliation(s)
- M E Garber
- Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA
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45
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Fujinaga K, Cujec TP, Peng J, Garriga J, Price DH, Graña X, Peterlin BM. The ability of positive transcription elongation factor B to transactivate human immunodeficiency virus transcription depends on a functional kinase domain, cyclin T1, and Tat. J Virol 1998; 72:7154-9. [PMID: 9696809 PMCID: PMC109937 DOI: 10.1128/jvi.72.9.7154-7159.1998] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
By binding to the transactivation response element (TAR) RNA, the transcriptional transactivator (Tat) from the human immunodeficiency virus increases rates of elongation rather than initiation of viral transcription. Two cyclin-dependent serine/threonine kinases, CDK7 and CDK9, which phosphorylate the C-terminal domain of RNA polymerase II, have been implicated in Tat transactivation in vivo and in vitro. In this report, we demonstrate that CDK9, which is the kinase component of the positive transcription elongation factor b (P-TEFb) complex, can activate viral transcription when tethered to the heterologous Rev response element RNA via the regulator of expression of virion proteins (Rev). The kinase activity of CDK9 and cyclin T1 is essential for these effects. Moreover, P-TEFb binds to TAR only in the presence of Tat. We conclude that Tat-P-TEFb complexes bind to TAR, where CDK9 modifies RNA polymerase II for the efficient copying of the viral genome.
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Affiliation(s)
- K Fujinaga
- Departments of Medicine, Microbiology, and Immunology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California 94143-0703, USA
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46
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Coudronnière N, Devaux C. A novel complex of proteins binds the HIV-1 promoter upon virus interaction with CD4. J Biomed Sci 1998; 5:281-9. [PMID: 9691221 DOI: 10.1007/bf02255860] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
HIV-1Lai13EM is a mutant isolate which is less sensitive than the parental HIV-1Lai strain to an in vitro treatment with 13B8-2 anti-CD4 monoclonal antibody (mAb) that generally inhibits transcription of HIV-1 and HIV-2. In contrast to other clade B viruses, this isolate carries a point mutation G > A at position -188 of the viral promoter. The fact that HIV-1NDK, a clade D virus insensitive to 13B8-2 mAb, also carries an A nucleotide at this position has brought our attention to the sequence surrounding position -188. Here we analyzed whether a DNA-binding molecule interacts with this region. Electrophoretic mobility shift assays performed with the -201/-175 HIV-1Lai wild-type sequence or the sequence containing a point mutation G > A at position -188 demonstrated their ability to bind a heterotrimeric complex induced in CEM cells by stimulation with heat-inactivated HIV-1.
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Affiliation(s)
- N Coudronnière
- CRBM/CNRS UPR 1086, Laboratoire Infections Rétrovirales et Signalisation Cellulaire, Institut de Biologie, Montpellier, France
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47
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Speck RF, Penn ML, Wimmer J, Esser U, Hague BF, Kindt TJ, Atchison RE, Goldsmith MA. Rabbit cells expressing human CD4 and human CCR5 are highly permissive for human immunodeficiency virus type 1 infection. J Virol 1998; 72:5728-34. [PMID: 9621031 PMCID: PMC110246 DOI: 10.1128/jvi.72.7.5728-5734.1998] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
To evaluate the feasibility of using transgenic rabbits expressing CCR5 and CD4 as a small-animal model of human immunodeficiency virus type 1 (HIV) disease, we examined whether the expression of the human chemokine receptor (CCR5) and human CD4 would render a rabbit cell line (SIRC) permissive to HIV replication. Histologically, SIRC cells expressing CD4 and CCR5 formed multinucleated cells (syncytia) upon exposure to BaL, a macrophagetropic strain of HIV that uses CCR5 for cell entry. Intracellular viral capsid p24 staining showed abundant viral gene expression in BaL-infected SIRC cells expressing CD4 and CCR5. In contrast, neither SIRC cells expressing CD4 alone nor murine 3T3 cells expressing CCR5 and CD4 exhibited significant expression of p24. These stably transfected rabbit cells were also highly permissive for the production of virions upon infection by two other CCR5-dependent strains (JR-CSF and YU-2) but not by a CXCR4-dependent strain (NL4-3). The functional integrity of these virions was demonstrated by the successful infection of human peripheral blood mononuclear cells (PBMC) with viral stocks prepared from these transfected rabbit cells. Furthermore, primary rabbit PBMC were found to be permissive for production of infectious virions after circumventing the cellular entry step. These results suggest that a transgenic rabbit model for the study of HIV disease may be feasible.
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Affiliation(s)
- R F Speck
- Gladstone Institute of Virology and Immunology, University of California, San Francisco, California 94141-9100, USA
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Gold MO, Yang X, Herrmann CH, Rice AP. PITALRE, the catalytic subunit of TAK, is required for human immunodeficiency virus Tat transactivation in vivo. J Virol 1998; 72:4448-53. [PMID: 9557739 PMCID: PMC109679 DOI: 10.1128/jvi.72.5.4448-4453.1998] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The human cdc2-related kinase PITALRE is the catalytic component of TAK, the Tat-associated kinase. Previously, we have proposed that TAK is a cellular factor that mediates Tat transactivation function. Here we demonstrate that transient overexpression of PITALRE specifically squelches Tat-1 activation of both a transfected and an integrated human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR), suggesting that PITALRE mediates Tat function as a multiprotein complex. A catalytic mutant of PITALRE, D167N, was found to be more efficient than wild-type PITALRE in squelching Tat transactivation. Neither wild-type PITALRE nor D167N was able to squelch transactivation of the human T-cell leukemia type 1 LTR by the Tax protein. Additionally, we show that artificial targeting of PITALRE to a nascent RNA element, in the absence of Tat, activated HIV-1 LTR expression. These results indicate that a PITALRE-containing complex mediates transactivation by Tat and suggest that Tat proteins function by localizing such a PITALRE-containing complex to the site of the transcribing provirus.
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Affiliation(s)
- M O Gold
- Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA
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Xiao H, Tao Y, Greenblatt J, Roeder RG. A cofactor, TIP30, specifically enhances HIV-1 Tat-activated transcription. Proc Natl Acad Sci U S A 1998; 95:2146-51. [PMID: 9482853 PMCID: PMC19278 DOI: 10.1073/pnas.95.5.2146] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Replication of HIV-1 requires the viral Tat protein, which increases the extent of transcription elongation by RNA polymerase II after activation at the single viral long terminal repeat (LTR) promoter. This effect of Tat on transcription requires Tat interactions with a 5' region (TAR) in nascent transcripts as well as Tat-specific cofactors. The present study identifies a cellular protein, TIP30, that interacts with Tat and with an SRB-containing RNA polymerase II complex both in vivo and in vitro. Coexpression of TIP30 specifically enhances transactivation by Tat in transfected cells, and immunodepletion of TIP30 from nuclear extracts abolishes Tat-activated transcription without affecting Tat-independent transcription. These results implicate TIP30 as a specific coactivator that may enhance formation of a Tat-RNA polymerase II holoenzyme complex.
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Affiliation(s)
- H Xiao
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10021, USA
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50
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Wei P, Garber ME, Fang SM, Fischer WH, Jones KA. A novel CDK9-associated C-type cyclin interacts directly with HIV-1 Tat and mediates its high-affinity, loop-specific binding to TAR RNA. Cell 1998; 92:451-62. [PMID: 9491887 DOI: 10.1016/s0092-8674(00)80939-3] [Citation(s) in RCA: 974] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The HIV-1 Tat protein regulates transcription elongation through binding to the viral TAR RNA stem-loop structure. We have isolated a novel 87 kDa cyclin C-related protein (cyclin T) that interacts specifically with the transactivation domain of Tat. Cyclin T is a partner for CDK9, an RNAPII transcription elongation factor. Remarkably, the interaction of Tat with cyclin T strongly enhances the affinity and specificity of the Tat:TAR RNA interaction, and confers a requirement for sequences in the loop of TAR that are not recognized by Tat alone. Moreover, overexpression of human cyclin T rescues Tat activity in nonpermissive rodent cells. We propose that Tat directs cyclin T-CDK9 to RNAPII through cooperative binding to TAR RNA.
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Affiliation(s)
- P Wei
- Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA
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