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Kufera JT, Armstrong C, Wu F, Singhal A, Zhang H, Lai J, Wilkins HN, Simonetti FR, Siliciano JD, Siliciano RF. CD4+ T cells with latent HIV-1 have reduced proliferative responses to T cell receptor stimulation. J Exp Med 2024; 221:e20231511. [PMID: 38270554 PMCID: PMC10818065 DOI: 10.1084/jem.20231511] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 11/04/2023] [Accepted: 01/09/2024] [Indexed: 01/26/2024] Open
Abstract
The latent reservoir for HIV-1 in resting CD4+ T cells persists despite antiretroviral therapy as a barrier to cure. The antigen-driven proliferation of infected cells is a major mechanism of reservoir persistence. However, activation through the T cell antigen receptor (TCR) can induce latent proviruses, leading to viral cytopathic effects and immune clearance. In single-cell studies, we show that, relative to uninfected cells or cells with a defective provirus, CD4+ T cells with an intact provirus have a profound proliferative defect in response to TCR stimulation. Virion production was observed in only 16.5% of cultures with an intact provirus, but proliferation was reduced even when no virion production was detected. Proliferation was inversely correlated with in vivo clone size. These results may reflect the effects of previous in vivo proliferation and do not support attempts to reduce the reservoir with antiproliferative agents, which may have greater effects on normal T cell responses.
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Affiliation(s)
- Joshua T. Kufera
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ciara Armstrong
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Fengting Wu
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anushka Singhal
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hao Zhang
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Jun Lai
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hannah N. Wilkins
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | | | - Janet D. Siliciano
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Robert F. Siliciano
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Howard Hughes Medical Institute, Baltimore, MD, USA
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2
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Yapo V, Majumder K, Tedbury PR, Wen X, Ong YT, Johnson MC, Sarafianos SG. HIV-2 inhibits HIV-1 gene expression via two independent mechanisms during cellular co-infection. J Virol 2023; 97:e0187022. [PMID: 37991365 PMCID: PMC10734542 DOI: 10.1128/jvi.01870-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 06/28/2023] [Indexed: 11/23/2023] Open
Abstract
IMPORTANCE Twenty-five years after the first report that HIV-2 infection can reduce HIV-1-associated pathogenesis in dual-infected patients, the mechanisms are still not well understood. We explored these mechanisms in cell culture and showed first that these viruses can co-infect individual cells. Under specific conditions, HIV-2 inhibits HIV-1 through two distinct mechanisms, a broad-spectrum interferon response and an HIV-1-specific inhibition conferred by the HIV-2 TAR. The former could play a prominent role in dually infected individuals, whereas the latter targets HIV-1 promoter activity through competition for HIV-1 Tat binding when the same target cell is dually infected. That mechanism suppresses HIV-1 transcription by stalling RNA polymerase II complexes at the promoter through a minimal inhibitory region within the HIV-2 TAR. This work delineates the sequence of appearance and the modus operandi of each mechanism.
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Affiliation(s)
- Vincent Yapo
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Kinjal Majumder
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Philip R. Tedbury
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Xin Wen
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Yee T. Ong
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Marc C. Johnson
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Stefan G. Sarafianos
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
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Sarott R, Gourisankar S, Karim B, Nettles S, Yang H, Dwyer BG, Simanauskaite JM, Tse J, Abuzaid H, Krokhotin A, Zhang T, Hinshaw SM, Green MR, Crabtree GR, Gray NS. Borrowing Transcriptional Kinases to Activate Apoptosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.23.563687. [PMID: 37961702 PMCID: PMC10634765 DOI: 10.1101/2023.10.23.563687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Protein kinases are disease drivers whose therapeutic targeting traditionally centers on inhibition of enzymatic activity. Here chemically induced proximity is leveraged to convert kinase inhibitors into context-specific activators of therapeutic genes. Bivalent molecules that link ligands of the transcription factor B-cell lymphoma 6 (BCL6) to ATP-competitive inhibitors of cyclin-dependent kinases (CDKs) were developed to re-localize CDK to BCL6-bound loci on chromatin and direct phosphorylation of RNA Pol II. The resulting BCL6-target proapoptotic gene expression translated into killing of diffuse large B-cell lymphoma (DLBCL) cells at 72 h with EC50s of 0.9 - 10 nM and highly specific ablation of the BCL6-regulated germinal center response in mice. The molecules exhibited 10,000-fold lower cytotoxicity in normal lymphocytes and are well tolerated in mice. Genomic and proteomic evidence corroborated a gain-of-function mechanism where, instead of global enzyme inhibition, a fraction of total kinase activity is borrowed and re-localized to BCL6-bound loci. The strategy demonstrates how kinase inhibitors can be used to context-specifically activate transcription, accessing new therapeutic space.
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4
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Heterogeneity of Latency Establishment in the Different Human CD4
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T Cell Subsets Stimulated with IL-15. J Virol 2022; 96:e0037922. [PMID: 35499323 PMCID: PMC9131862 DOI: 10.1128/jvi.00379-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
HIV integrates into the host genome, creating a viral reservoir of latently infected cells that persists despite effective antiretroviral treatment. CD4-positive (CD4+) T cells are the main contributors to the HIV reservoir. CD4+ T cells are a heterogeneous population, and the mechanisms of latency establishment in the different subsets, as well as their contribution to the reservoir, are still unclear. In this study, we analyzed HIV latency establishment in different CD4+ T cell subsets stimulated with interleukin 15 (IL-15), a cytokine that increases both susceptibility to infection and reactivation from latency. Using a dual-reporter virus that allows discrimination between latent and productive infection at the single-cell level, we found that IL-15-treated primary human CD4+ T naive and CD4+ T stem cell memory (TSCM) cells are less susceptible to HIV infection than CD4+ central memory (TCM), effector memory (TEM), and transitional memory (TTM) cells but are also more likely to harbor transcriptionally silent provirus. The propensity of these subsets to harbor latent provirus compared to the more differentiated memory subsets was independent of differential expression of pTEFb components. Microscopy analysis of NF-κB suggested that CD4+ T naive cells express smaller amounts of nuclear NF-κB than the other subsets, partially explaining the inefficient long terminal repeat (LTR)-driven transcription. On the other hand, CD4+ TSCM cells display similar levels of nuclear NF-κB to CD4+ TCM, CD4+ TEM, and CD4+ TTM cells, indicating the availability of transcription initiation and elongation factors is not solely responsible for the inefficient HIV gene expression in the CD4+ TSCM subset. IMPORTANCE The formation of a latent reservoir is the main barrier to HIV cure. Here, we investigated how HIV latency is established in different CD4+ T cell subsets in the presence of IL-15, a cytokine that has been shown to efficiently induce latency reversal. We observed that, even in the presence of IL-15, the less differentiated subsets display lower levels of productive HIV infection than the more differentiated subsets. These differences were not related to different expression of pTEFb, and modest differences in NF-κB were observed for CD4+ T naive cells only, implying the involvement of other mechanisms. Understanding the molecular basis of latency establishment in different CD4+ T cell subsets might be important for tailoring specific strategies to reactivate HIV transcription in all the CD4+ T subsets that compose the latent reservoir.
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Lu WC, Omari R, Ray H, Wang J, Williams I, Jacobs C, Hockaden N, Bochman ML, Carpenter RL. AKT1 mediates multiple phosphorylation events that functionally promote HSF1 activation. FEBS J 2022; 289:3876-3893. [PMID: 35080342 PMCID: PMC9309721 DOI: 10.1111/febs.16375] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 12/22/2021] [Accepted: 01/24/2022] [Indexed: 12/26/2022]
Abstract
The heat stress response activates the transcription factor heat shock factor 1 (HSF1), which subsequently upregulates heat shock proteins to maintain the integrity of the proteome. HSF1 activation requires nuclear localization, trimerization, DNA binding, phosphorylation and gene transactivation. Phosphorylation at S326 is an important regulator of HSF1 transcriptional activity. Phosphorylation at S326 is mediated by AKT1, mTOR, p38, MEK1 and DYRK2. Here, we observed activation of HSF1 by AKT1 independently of mTOR. AKT2 also phosphorylated S326 of HSF1 but showed weak ability to activate HSF1. Similarly, mTOR, p38, MEK1 and DYRK2 all phosphorylated S326 but AKT1 was the most potent activator. Mass spectrometry showed that AKT1 also phosphorylated HSF1 at T142, S230 and T527 in addition to S326, whereas the other kinases did not. Subsequent investigation revealed that phosphorylation at T142 is necessary for HSF1 trimerization and that S230, S326 and T527 are required for HSF1 gene transactivation and recruitment of TFIIB and CDK9. Interestingly, T527 as a phosphorylated residue has not been previously shown and sits in the transactivation domain, further implying a role for this site in HSF1 gene transactivation. This study suggests that HSF1 hyperphosphorylation is targeted and these specific residues have direct function in regulating HSF1 transcriptional activity.
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Affiliation(s)
- Wen-Cheng Lu
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Ramsey Omari
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Haimanti Ray
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - John Wang
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Imade Williams
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Curteisha Jacobs
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Natasha Hockaden
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA
| | - Matthew L Bochman
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN, USA.,Melvin and Bren Simon Comprehensive Cancer Center, Indiana University School of Medicine, IN, USA
| | - Richard L Carpenter
- Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA.,Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, IN, USA.,Melvin and Bren Simon Comprehensive Cancer Center, Indiana University School of Medicine, IN, USA
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6
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McHugh BJ, Stephen J, Robb CT, Fox S, Kipari T, Cartwright JA, Haslett C, Duffin R, Lucas CD, Rossi AG. Inhibition of Cyclin-Dependent Kinase 9 Downregulates Cytokine Production Without Detrimentally Affecting Human Monocyte-Derived Macrophage Viability. Front Cell Dev Biol 2022; 10:905315. [PMID: 35693926 PMCID: PMC9178253 DOI: 10.3389/fcell.2022.905315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 05/03/2022] [Indexed: 12/15/2022] Open
Abstract
Cyclin-dependent kinase (CDK) inhibitor drugs (CDKi), such as R-roscovitine and AT7519, induce neutrophil apoptosis in vitro and enhance the resolution of inflammation in a number of in vivo models. This class of compounds are potential novel therapeutic agents that could promote the resolution of acute and chronic inflammatory conditions where neutrophil activation contributes to tissue damage and aberrant tissue repair. In this study we investigated CDKi effects on macrophage pro-inflammatory mediator production and viability. Treatment of human monocyte-derived macrophages (MDMs) with the CDKi AT7519 and R-roscovitine at concentrations that induce neutrophil apoptosis had no significant effect on control or LPS-activated MDM apoptosis and viability, and did not detrimentally affect MDM efferocytosis of apoptotic cells. In addition, enhanced efferocytosis, induced by the glucocorticoid dexamethasone, was also unaffected after a short time treatment with R-roscovitine. Macrophage cytokine responses to inflammatory stimuli are also of importance during inflammation and resolution. As a key target of CDKi, CDK9, is involved in protein transcription via the RNA polymerase II complex, we investigated the effect of CDKi drugs on cytokine production. Our data show that treatment with AT7519 significantly downregulated expression and release of key MDM cytokines IL-6, TNF, IL-10 and IL-1β, as well as markers of pro-inflammatory macrophage polarisation. R-Roscovitine was also able to downregulate inflammatory cytokine protein secretion from MDMs. Using siRNA transfection, we demonstrate that genetic knock-down of CDK9 replicates these findings, reducing expression and release of pro-inflammatory cytokines. Furthermore, overexpression of CDK9 in THP-1 cells can promote a pro-inflammatory phenotype in these cells, suggesting that CDK9 plays an important role in the inflammatory phenotype of macrophages. Overall, this study demonstrates that pharmacological and genetic targeting of CDK9 inhibits an inflammatory phenotype in human MDMs. As such these data indicate that CDK9 may be key to therapeutically targeting pro-inflammatory macrophage functions during chronic inflammation.
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7
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Bush JA, Williams CC, Meyer SM, Tong Y, Haniff HS, Childs-Disney JL, Disney MD. Systematically Studying the Effect of Small Molecules Interacting with RNA in Cellular and Preclinical Models. ACS Chem Biol 2021; 16:1111-1127. [PMID: 34166593 PMCID: PMC8867596 DOI: 10.1021/acschembio.1c00014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The interrogation and manipulation of biological systems by small molecules is a powerful approach in chemical biology. Ideal compounds selectively engage a target and mediate a downstream phenotypic response. Although historically small molecule drug discovery has focused on proteins and enzymes, targeting RNA is an attractive therapeutic alternative, as many disease-causing or -associated RNAs have been identified through genome-wide association studies. As the field of RNA chemical biology emerges, the systematic evaluation of target validation and modulation of target-associated pathways is of paramount importance. In this Review, through an examination of case studies, we outline the experimental characterization, including methods and tools, to evaluate comprehensively the impact of small molecules that target RNA on cellular phenotype.
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Affiliation(s)
- Jessica A Bush
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Christopher C Williams
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Samantha M Meyer
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Yuquan Tong
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Hafeez S Haniff
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Jessica L Childs-Disney
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
| | - Matthew D Disney
- The Scripps Research Institute, Department of Chemistry, 130 Scripps Way, Jupiter, Florida 33458, United States
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8
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Basu S, Nandy A, Biswas D. Keeping RNA polymerase II on the run: Functions of MLL fusion partners in transcriptional regulation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1863:194563. [PMID: 32348849 DOI: 10.1016/j.bbagrm.2020.194563] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 01/13/2020] [Accepted: 04/13/2020] [Indexed: 12/21/2022]
Abstract
Since the identification of key MLL fusion partners as transcription elongation factors regulating expression of HOX cluster genes during hematopoiesis, extensive work from the last decade has resulted in significant progress in our overall mechanistic understanding of role of MLL fusion partner proteins in transcriptional regulation of diverse set of genes beyond just the HOX cluster. In this review, we are going to detail overall understanding of role of MLL fusion partner proteins in transcriptional regulation and thus provide mechanistic insights into possible MLL fusion protein-mediated transcriptional misregulation leading to aberrant hematopoiesis and leukemogenesis.
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Affiliation(s)
- Subham Basu
- Laboratory of Transcription Biology, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Kolkata 32, India
| | - Arijit Nandy
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Debabrata Biswas
- Laboratory of Transcription Biology, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S. C. Mullick Road, Kolkata 32, India.
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Resistance to the Tat Inhibitor Didehydro-Cortistatin A Is Mediated by Heightened Basal HIV-1 Transcription. mBio 2019; 10:mBio.01750-18. [PMID: 31266880 PMCID: PMC6606815 DOI: 10.1128/mbio.01750-18] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) Tat binds the viral RNA structure transactivation-responsive element (TAR) and recruits transcriptional cofactors, amplifying viral mRNA expression. The Tat inhibitor didehydro-cortistatin A (dCA) promotes a state of persistent latency, refractory to viral reactivation. Here we investigated mechanisms of HIV-1 resistance to dCA in vitro Mutations in Tat and TAR were not identified, consistent with the high level of conservation of these elements. Instead, viruses resistant to dCA developed higher Tat-independent basal transcription. We identified a combination of mutations in the HIV-1 promoter that increased basal transcriptional activity and modifications in viral Nef and Vpr proteins that increased NF-κB activity. Importantly, these variants are unlikely to enter latency due to accrued transcriptional fitness and loss of sensitivity to Tat feedback loop regulation. Furthermore, cells infected with these variants become more susceptible to cytopathic effects and immune-mediated clearance. This is the first report of viral escape to a Tat inhibitor resulting in heightened Tat-independent activity, all while maintaining wild-type Tat and TAR.IMPORTANCE HIV-1 Tat enhances viral RNA transcription by binding to TAR and recruiting activating factors. Tat enhances its own transcription via a positive-feedback loop. Didehydro-cortistatin A (dCA) is a potent Tat inhibitor, reducing HIV-1 transcription and preventing viral rebound. dCA activity demonstrates the potential of the "block-and-lock" functional cure approaches. We investigated the viral genetic barrier to dCA resistance in vitro While mutations in Tat and TAR were not identified, mutations in the promoter and in the Nef and Vpr proteins promoted high Tat-independent activity. Promoter mutations increased the basal transcription, while Nef and Vpr mutations increased NF-κB nuclear translocation. This heightened transcriptional activity renders CD4+ T cells infected with these viruses more susceptible to cytotoxic T cell-mediated killing and to cell death by cytopathic effects. Results provide insights on drug resistance to a novel class of antiretrovirals and reveal novel aspects of viral transcriptional regulation.
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Krasnopolsky S, Marom L, Victor RA, Kuzmina A, Schwartz JC, Fujinaga K, Taube R. Fused in sarcoma silences HIV gene transcription and maintains viral latency through suppressing AFF4 gene activation. Retrovirology 2019; 16:16. [PMID: 31238957 PMCID: PMC6593535 DOI: 10.1186/s12977-019-0478-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/11/2019] [Indexed: 12/12/2022] Open
Abstract
Background The human immunodeficiency virus (HIV) cell reservoir is currently a main obstacle towards complete eradication of the virus. This infected pool is refractory to anti-viral therapy and harbors integrated proviruses that are transcriptionally repressed but replication competent. As transcription silencing is key for establishing the HIV reservoir, significant efforts have been made to understand the mechanism that regulate HIV gene transcription, and the role of the elongation machinery in promoting this step. However, while the role of the super elongation complex (SEC) in enhancing transcription activation of HIV is well established, the function of SEC in modulating viral latency is less defined and its cell partners are yet to be identified. Results In this study we identify fused in sarcoma (FUS) as a partner of AFF4 in cells. FUS inhibits the activation of HIV transcription by AFF4 and ELL2, and silences overall HIV gene transcription. Concordantly, depletion of FUS elevates the occupancy of AFF4 and Cdk9 on the viral promoter and activates HIV gene transcription. Live cell imaging demonstrates that FUS co-localizes with AFF4 within nuclear punctuated condensates, which are disrupted upon treating cells with aliphatic alcohol. In HIV infected cells, knockout of FUS delays the gradual entry of HIV into latency, and similarly promotes viral activation in a T cell latency model that is treated with JQ1. Finally, effects of FUS on HIV gene transcription are also exhibited genome wide, where FUS mainly occupies gene promoters at transcription starting sites, while its knockdown leads to an increase in AFF4 and Cdk9 occupancy on gene promoters of FUS affected genes. Conclusions Towards eliminating the HIV infected reservoir, understanding the mechanisms by which the virus persists in the face of therapy is important. Our observations show that FUS regulates both HIV and global gene transcription and modulates viral latency, thus can potentially serve as a target for future therapy that sets to reactivate HIV from its latent state. Electronic supplementary material The online version of this article (10.1186/s12977-019-0478-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Simona Krasnopolsky
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel
| | - Lital Marom
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel
| | - Rachel A Victor
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Alona Kuzmina
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel
| | - Jacob C Schwartz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Koh Fujinaga
- Department of Medicine, University of California, San Francisco, CA, USA
| | - Ran Taube
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer Sheva, Israel.
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11
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Splicing Factor 3B Subunit 1 Interacts with HIV Tat and Plays a Role in Viral Transcription and Reactivation from Latency. mBio 2018; 9:mBio.01423-18. [PMID: 30401776 PMCID: PMC6222122 DOI: 10.1128/mbio.01423-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The reason why HIV cannot be cured by current therapy is because of viral persistence in resting T cells. One approach to permanent HIV remission that has received less attention is the so-called “block and lock” approach. The idea behind this approach is that the virus could be permanently disabled in patients if viral genome or surrounding chromatin could be altered to silence the virus, thus enabling patients to stop therapy. In this work, we have identified splicing factor 3B subunit 1 (SF3B1) as a potential target for this approach. SF3B1 interacts with the viral protein Tat, which is critical for viral transcription. Inhibition of SF3B1 prevents HIV transcription and reactivation from latency. Since there are preclinical inhibitors for this protein, our findings could pave the way to silence HIV transcription, potentially leading to prolonged or permanent remission. The main obstacle to an HIV cure is the transcriptionally inert proviruses that persist in resting CD4 T cells and other reservoirs. None of the current approaches has significantly reduced the size of the viral reservoir. Hence, alternative approaches, such as permanent blocking of viral transcription, to achieve a sustained remission, need urgent attention. To identify cellular factors that may be important for this approach, we sought for host targets that when altered could block HIV transcription and reactivation. Here, we identified splicing factor 3B subunit 1 (SF3B1) as a critical HIV dependency factor required for viral replication. SF3B1 is a splicing factor involved in directing chromatin and nascent gene transcripts to appropriate splice sites. Inhibitors of SF3B1 are currently in development for cancer and have been found to be nontoxic to normal cells compared to malignant cells. Knockdown of SF3B1 abrogated HIV replication in all cell types tested. SF3B1 interacted with viral protein Tat in vitro and in vivo. Genetic or pharmacologic inhibition of SF3B1 prevented Tat-mediated HIV transcription and RNA polymerase II association with the HIV promoter. In addition, an inhibitor of SF3B1 prevented HIV reactivation from latency irrespective of the latency-reversing agent used. The data show that SF3B1 is involved in viral transcription and reactivation from latency and may serve as a therapeutic target in the HIV cure efforts.
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12
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Roebuck KA, Saifuddin M. Regulation of HIV-1 transcription. Gene Expr 2018; 8:67-84. [PMID: 10551796 PMCID: PMC6157391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Human immunodeficiency virus type-1 (HIV-1) is a highly pathogenic lentivirus that requires transcription of its provirus genome for completion of the viral life cycle and the production of progeny virions. Since the first genetic analysis of HIV-1 in 1985, much has been learned about the transcriptional regulation of the HIV-1 genome in infected cells. It has been demonstrated that HIV-1 transcription depends on a varied and complex interaction of host cell transcription factors with the viral long terminal repeat (LTR) promoter. The regulatory elements within the LTR interact with constitutive and inducible transcription factors to direct the assembly of a stable transcription complex that stimulates multiple rounds of transcription by RNA polymerase II (RNAPII). However, the majority of these transcripts terminate prematurely in the absence of the virally encoded trans-activator protein Tat, which stimulates HIV-1 transcription elongation by interacting with a stem-loop RNA element (TAR) formed at the extreme 5' end of all viral transcripts. The Tat-TAR interaction recruits a cellular kinase into the initiation-elongation complex that alters the elongation properties of RNAPII during its transit through TAR. This review summarizes our current knowledge and understanding of the regulation of HIV-1 transcription in infected cells and highlights the important contributions human lentivirus gene regulation has made to our general understanding of the transcription process.
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Affiliation(s)
- K A Roebuck
- Department of Immunology/Microbiology, Rush Presbyterian St. Luke's Medical Center, Chicago, IL 60612, USA.
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13
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Mbonye U, Wang B, Gokulrangan G, Shi W, Yang S, Karn J. Cyclin-dependent kinase 7 (CDK7)-mediated phosphorylation of the CDK9 activation loop promotes P-TEFb assembly with Tat and proviral HIV reactivation. J Biol Chem 2018; 293:10009-10025. [PMID: 29743242 DOI: 10.1074/jbc.ra117.001347] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 04/29/2018] [Indexed: 11/06/2022] Open
Abstract
The HIV trans-activator Tat recruits the host transcription elongation factor P-TEFb to stimulate proviral transcription. Phosphorylation of Thr-186 on the activation loop (T-loop) of cyclin-dependent kinase 9 (CDK9) is essential for its kinase activity and assembly of CDK9 and cyclin T1 (CycT1) to form functional P-TEFb. Phosphorylation of a second highly conserved T-loop site, Ser-175, alters the competitive binding of Tat and the host recruitment factor bromodomain containing 4 (BRD4) to P-TEFb. Here, we investigated the intracellular mechanisms that regulate these key phosphorylation events required for HIV transcription. Molecular dynamics simulations revealed that the CDK9/CycT1 interface is stabilized by intramolecular hydrogen bonding of pThr-186 by an arginine triad and Glu-96 of CycT1. Arginine triad substitutions that disrupted CDK9/CycT1 assembly accumulated Thr-186-dephosphorylated CDK9 associated with the cytoplasmic Hsp90/Cdc37 chaperone. The Hsp90/Cdc37/CDK9 complex was also present in resting T cells, which lack CycT1. Hsp90 inhibition in primary T cells blocked P-TEFb assembly, disrupted Thr-186 phosphorylation, and suppressed proviral reactivation. The selective CDK7 inhibitor THZ1 blocked CDK9 phosphorylation at Ser-175, and in vitro kinase assays confirmed that CDK7 activity is principally responsible for Ser-175 phosphorylation. Mutation of Ser-175 to Lys had no effect on CDK9 kinase activity or P-TEFb assembly but strongly suppressed both HIV expression and BRD4 binding. We conclude that the transfer of CDK9 from the Hsp90/Cdc37 complex induced by Thr-186 phosphorylation is a key step in P-TEFb biogenesis. Furthermore, we demonstrate that CDK7-mediated Ser-175 phosphorylation is a downstream nuclear event essential for facilitating CDK9 T-loop interactions with Tat.
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Affiliation(s)
- Uri Mbonye
- From the Department of Molecular Biology and Microbiology and
| | - Benlian Wang
- the Center for Proteomics and Bioinformatics and Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Giridharan Gokulrangan
- the Center for Proteomics and Bioinformatics and Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Wuxian Shi
- the Center for Proteomics and Bioinformatics and Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Sichun Yang
- the Center for Proteomics and Bioinformatics and Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Jonathan Karn
- From the Department of Molecular Biology and Microbiology and
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Paparidis NFDS, Durvale MC, Canduri F. The emerging picture of CDK9/P-TEFb: more than 20 years of advances since PITALRE. MOLECULAR BIOSYSTEMS 2017; 13:246-276. [PMID: 27833949 DOI: 10.1039/c6mb00387g] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
CDK9 is a prominent member of the transcriptional CDKs subfamily, a group of kinases whose function is to control the primary steps of mRNA synthesis and processing by eukaryotic RNA polymerase II. As a cyclin-dependent kinase, CDK9 activation in vivo depends upon its association with T-type cyclins to assemble the positive transcription elongation factor (P-TEFb). Although CDK9/P-TEFb phosphorylates the C-terminal domain of RNAP II in the same positions targeted by CDK7 (TFIIH) and CDK8 (Mediator), the former does not participate in the transcription initiation, but rather plays a unique role by driving the polymerase to productive elongation. In addition to RNAP II CTD, the negative transcription elongation factors DSIF and NELF also represent major CDK9 substrates, whose phosphorylation is required to overcome the proximal pause of the polymerase. CDK9 is recruited to specific genes through proteins that interact with both P-TEFb and distinct elements in DNA, RNA or chromatin, where it modulates the activity of individual RNAP II transcription complexes. The regulation of CDK9 function is an intricate network that includes post-translational modifications (phosphorylation/dephosphorylation and acetylation/deacetylation of key residues) as well as the association of P-TEFb with various proteins that can stimulate or inhibit its kinase activity. Several cases of CDK9 deregulation have been linked to important human diseases, including various types of cancer and also AIDS (due to its essential role in HIV replication). Not only HIV, but also many other human viruses have been shown to depend strongly on CDK9 activity to be transcribed within host cells. This review summarizes the main advances made on CDK9/P-TEFb field in more than 20 years, introducing the structural, functional and genetic aspects that have been elucidated ever since.
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Affiliation(s)
- Nikolas Ferreira Dos Santos Paparidis
- Department of Chemistry and Molecular Physics, Institute of Chemistry of Sao Carlos, Sao Paulo University, Av. Trabalhador Sãocarlense, 400, Zip Code 780, 13560-970, São Carlos-SP, Brazil.
| | - Maxwell Castro Durvale
- Department of Biochemistry, Institute of Chemistry, Sao Paulo University, Av. Prof. Lineu Prestes, 748, 05508-000, Butantã - São Paulo - SP, Brazil
| | - Fernanda Canduri
- Department of Chemistry and Molecular Physics, Institute of Chemistry of Sao Carlos, Sao Paulo University, Av. Trabalhador Sãocarlense, 400, Zip Code 780, 13560-970, São Carlos-SP, Brazil.
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Asamitsu K, Omagari K, Okuda T, Hibi Y, Okamoto T. Quantification of the HIV transcriptional activator complex in live cells by image-based protein-protein interaction analysis. Genes Cells 2016; 21:706-16. [PMID: 27193293 DOI: 10.1111/gtc.12375] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 04/17/2016] [Indexed: 01/16/2023]
Abstract
The virus-encoded Tat protein is essential for HIV transcription in infected cells. The interaction of Tat with the cellular transcription elongation factor P-TEFb (positive transcriptional elongation factor b) containing cyclin T1 (CycT1) and cyclin-dependent kinase 9 (CDK9) is critical for its activity. In this study, we use the Fluoppi (fluorescent-based technology detecting protein-protein interaction) system, which enables the quantification of interactions between biomolecules, such as proteins, in live cells. Quantitative measurement of the molecular interactions among Tat, CycT1 and CDK9 has showed that any third molecule enhances the binding between the other two molecules. These findings suggest that each component of the Tat:P-TEFb complex stabilizes the overall complex, thereby supporting the efficient transcriptional elongation during viral RNA synthesis. These interactions may serve as appropriate targets for novel anti-HIV therapy.
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Affiliation(s)
- Kaori Asamitsu
- Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, 467-8601, Japan
| | - Katsumi Omagari
- Department of Virology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, 467-8601, Japan
| | - Tomoya Okuda
- Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, 467-8601, Japan
| | - Yurina Hibi
- Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, 467-8601, Japan
| | - Takashi Okamoto
- Department of Molecular and Cellular Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, 467-8601, Japan
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The Smad3/Smad4/CDK9 complex promotes renal fibrosis in mice with unilateral ureteral obstruction. Kidney Int 2015. [DOI: 10.1038/ki.2015.235] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Huang H, Santoso N, Power D, Simpson S, Dieringer M, Miao H, Gurova K, Giam CZ, Elledge SJ, Zhu J. FACT Proteins, SUPT16H and SSRP1, Are Transcriptional Suppressors of HIV-1 and HTLV-1 That Facilitate Viral Latency. J Biol Chem 2015; 290:27297-27310. [PMID: 26378236 DOI: 10.1074/jbc.m115.652339] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Indexed: 11/06/2022] Open
Abstract
Our functional genomic RNAi screens have identified the protein components of the FACT (facilitates chromatin transcription) complex, SUPT16H and SSRP1, as top host factors that negatively regulate HIV-1 replication. FACT interacts specifically with histones H2A/H2B to affect assembly and disassembly of nucleosomes, as well as transcription elongation. We further investigated the suppressive role of FACT proteins in HIV-1 transcription. First, depletion of SUPT16H or SSRP1 protein enhances Tat-mediated HIV-1 LTR (long terminal repeat) promoter activity. Second, HIV-1 Tat interacts with SUPT16H but not SSRP1 protein. However, both SUPT16H and SSRP1 are recruited to LTR promoter. Third, the presence of SUPT16H interferes with the association of Cyclin T1 (CCNT1), a subunit of P-TEFb, with the Tat-LTR axis. Removing inhibitory mechanisms to permit HIV-1 transcription is an initial and key regulatory step to reverse post-integrated latent HIV-1 proviruses for purging of reservoir cells. We therefore evaluated the role of FACT proteins in HIV-1 latency and reactivation. Depletion of SUPT16H or SSRP1 protein affects both HIV-1 transcriptional initiation and elongation and spontaneously reverses latent HIV-1 in U1/HIV and J-LAT cells. Similar effects were observed with a primary CD4+ T cell model of HIV-1 latency. FACT proteins also interfere with HTLV-1 Tax-LTR-mediated transcription and viral latency, indicating that they may act as general transcriptional suppressors for retroviruses. We conclude that FACT proteins SUPT16H and SSRP1 play a key role in suppressing HIV-1 transcription and promoting viral latency, which may serve as promising gene targets for developing novel HIV-1 latency-reversing agents.
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Affiliation(s)
- Huachao Huang
- Departments of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642
| | - Netty Santoso
- Departments of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642
| | - Derek Power
- Departments of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642
| | - Sydney Simpson
- the School of Arts and Sciences, University of Rochester, Rochester, New York 14627
| | - Michael Dieringer
- the School of Arts and Sciences, University of Rochester, Rochester, New York 14627
| | - Hongyu Miao
- Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, New York 14642
| | - Katerina Gurova
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Chou-Zen Giam
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
| | - Stephen J Elledge
- the Division of Genetics, Brigham and Women's Hospital, Howard Hughes Medical Institute, Boston, Massachusetts 02115; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Jian Zhu
- Departments of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642; Departments of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642.
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Stable Phenotypic Changes of the Host T Cells Are Essential to the Long-Term Stability of Latent HIV-1 Infection. J Virol 2015; 89:6656-72. [PMID: 25878110 DOI: 10.1128/jvi.00571-15] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 04/10/2015] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED The extreme stability of the latent HIV-1 reservoir in the CD4(+) memory T cell population prevents viral eradication with current antiretroviral therapy. It has been demonstrated that homeostatic T cell proliferation and clonal expansion of latently infected T cells due to viral integration into specific genes contribute to this extraordinary reservoir stability. Nevertheless, given the constant exposure of the memory T cell population to specific antigen or bystander activation, this reservoir stability seems remarkable, unless it is assumed that latent HIV-1 resides exclusively in memory T cells that recognize rare antigens. Another explanation for the stability of the reservoir could be that the latent HIV-1 reservoir is associated with an unresponsive T cell phenotype. We demonstrate here that host cells of latent HIV-1 infection events were functionally altered in ways that are consistent with the idea of an anergic, unresponsive T cell phenotype. Manipulations that induced or mimicked an anergic T cell state promoted latent HIV-1 infection. Kinome analysis data reflected this altered host cell phenotype at a system-wide level and revealed how the stable kinase activity changes networked to stabilize latent HIV-1 infection. Protein-protein interaction networks generated from kinome data could further be used to guide targeted genetic or pharmacological manipulations that alter the stability of latent HIV-1 infection. In summary, our data demonstrate that stable changes to the signal transduction and transcription factor network of latently HIV-1 infected host cells are essential to the ability of HIV-1 to establish and maintain latent HIV-1 infection status. IMPORTANCE The extreme stability of the latent HIV-1 reservoir allows the infection to persist for the lifetime of a patient, despite completely suppressive antiretroviral therapy. This extreme reservoir stability is somewhat surprising, since the latently HIV-1 infected CD4(+) memory T cells that form the structural basis of the viral reservoir should be exposed to cognate antigen over time. Antigen exposure would trigger a recall response and should deplete the reservoir, likely over a relatively short period. Our data demonstrate that stable and system-wide phenotypic changes to host cells are a prerequisite for the establishment and maintenance of latent HIV-1 infection events. The changes observed are consistent with an unresponsive, anergy-like T cell phenotype of latently HIV-1 infected host cells. An anergy-like, unresponsive state of the host cells of latent HIV-1 infection events would explain the stability of the HIV-1 reservoir in the face of continuous antigen exposure.
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Martinez-Zapien D, Saliou JM, Han X, Atmanene C, Proux F, Cianférani S, Dock-Bregeon AC. Intermolecular recognition of the non-coding RNA 7SK and HEXIM protein in perspective. Biochimie 2015; 117:63-71. [PMID: 25863285 DOI: 10.1016/j.biochi.2015.03.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/25/2015] [Indexed: 11/18/2022]
Abstract
A 7SKsnRNP complex, comprising the non-coding RNA 7SK and proteins MePCE and LARP7, participates in the regulation of the transcription elongation by RNA-polymerase II in higher eukaryotes. Binding of a HEXIM protein triggers the inhibition of the kinase complex P-TEFb, a key actor of the switch from paused transcription to elongation. The present paper reviews what is known about the specific recognition of the 7SK RNA by the HEXIM protein. HEXIM uses an arginine-rich motif (ARM) peptide to bind one specific site in the 5'-hairpin of the 7SK RNA. Since HEXIM forms a dimer, what happens with the second ARM impacts the assembly symmetry. In order to help sort through possible models, a combination of native mass spectrometry and electrophoretic mobility shift assays was used. It provides evidence that only one ARM of the HEXIM dimer is directly binding to the RNA hairpin and that another sequence downstream of the ARM participates in a second binding event allowing the other monomer of HEXIM to bind the RNA.
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Affiliation(s)
- Denise Martinez-Zapien
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), Institute of Genetics and of Molecular and Cellular Biology (IGBMC) 67404 Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France; Biotechnologie et Signalisation Cellulaire UMR 7242, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard Sébastien Brant, BP 10413, F-67412 Illkirch, France.
| | - Jean-Michel Saliou
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France; Center for Infection and Immunity of Lille (CIIL), Institut Pasteur de Lille, CNRS UMR 8204, INSERM U1019, Université Lille Nord de France, 1 rue du Pr. Calmette, 59000 Lille, France.
| | - Xiao Han
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France; Key Laboratory of Brain Functional Genomics, East China Normal University (ECNU), Shanghai, PR China.
| | - Cedric Atmanene
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
| | - Florence Proux
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France.
| | - Sarah Cianférani
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
| | - Anne-Catherine Dock-Bregeon
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France.
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Molecular dynamics simulation and experimental verification of the interaction between cyclin T1 and HIV-1 Tat proteins. PLoS One 2015; 10:e0119451. [PMID: 25781978 PMCID: PMC4363469 DOI: 10.1371/journal.pone.0119451] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 01/13/2015] [Indexed: 11/19/2022] Open
Abstract
The viral encoded Tat protein is essential for the transcriptional activation of HIV proviral DNA. Interaction of Tat with a cellular transcription elongation factor P-TEFb containing CycT1 is critically required for its action. In this study, we performed MD simulation using the 3D data for wild-type and 4CycT1mutants3D data. We found that the dynamic structural change of CycT1 H2’ helix is indispensable for its activity for the Tat action. Moreover, we detected flexible structural changes of the Tat-recognition cavity in the WT CycT1 comprising of ten AAs that are in contact with Tat. These structural fluctuations in WT were lost in the CycT1 mutants. We also found the critical importance of the hydrogen bond network involving H1, H1’ and H2 helices of CycT1. Since similar AA substitutions of the Tat-CycT1 chimera retained the Tat-supporting activity, these interactions are considered primarily involved in interaction with Tat. These findings described in this paper should provide vital information for the development of effective anti-Tat compound.
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Guendel I, Meltzer BW, Baer A, Dever SM, Valerie K, Guo J, Wu Y, Kehn-Hall K. BRCA1 functions as a novel transcriptional cofactor in HIV-1 infection. Virol J 2015; 12:40. [PMID: 25879655 PMCID: PMC4359766 DOI: 10.1186/s12985-015-0266-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 02/14/2015] [Indexed: 01/20/2023] Open
Abstract
Background Viruses have naturally evolved elegant strategies to manipulate the host’s cellular machinery, including ways to hijack cellular DNA repair proteins to aid in their own replication. Retroviruses induce DNA damage through integration of their genome into host DNA. DNA damage signaling proteins including ATR, ATM and BRCA1 contribute to multiple steps in the HIV-1 life cycle, including integration and Vpr-induced G2/M arrest. However, there have been no studies to date regarding the role of BRCA1 in HIV-1 transcription. Methods Here we performed various transcriptional analyses to assess the role of BRCA1 in HIV-1 transcription by overexpression, selective depletion, and treatment with small molecule inhibitors. We examined association of Tat and BRCA1 through in vitro binding assays, as well as BRCA1-LTR association by chromatin immunoprecipitation. Results BRCA1 was found to be important for viral transcription as cells that lack BRCA1 displayed severely reduced HIV-1 Tat-dependent transcription, and gain or loss-of-function studies resulted in enhanced or decreased transcription. Moreover, Tat was detected in complex with BRCA1 aa504-802. Small molecule inhibition of BRCA1 phosphorylation effector kinases, ATR and ATM, decreased Tat-dependent transcription, whereas a Chk2 inhibitor showed no effect. Furthermore, BRCA1 was found at the viral promoter and treatment with curcumin and ATM inhibitors decreased BRCA1 LTR occupancy. Importantly, these findings were validated in a highly relevant model of HIV infection and are indicative of BRCA1 phosphorylation affecting Tat-dependent transcription. Conclusions BRCA1 presence at the HIV-1 promoter highlights a novel function of the multifaceted protein in HIV-1 infection. The BRCA1 pathway or enzymes that phosphorylate BRCA1 could potentially be used as complementary host-based treatment for combined antiretroviral therapy, as there are multiple potent ATM inhibitors in development as chemotherapeutics.
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Affiliation(s)
- Irene Guendel
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
| | - Beatrix W Meltzer
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
| | - Alan Baer
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
| | - Seth M Dever
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298, USA. .,Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
| | - Kristoffer Valerie
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
| | - Jia Guo
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
| | - Yuntao Wu
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
| | - Kylene Kehn-Hall
- National Center for Biodefense & Infectious Diseases, School of Systems Biology, George Mason University, Biomedical Research Lab, 10650 Pyramid Place, MS 1J5, Manassas, VA, 20110, USA.
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Fujinaga K, Luo Z, Peterlin BM. Genetic analysis of the structure and function of 7SK small nuclear ribonucleoprotein (snRNP) in cells. J Biol Chem 2015; 289:21181-90. [PMID: 24917669 DOI: 10.1074/jbc.m114.557751] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The positive transcription elongation factor b (P-TEFb), comprised of cyclin-dependent kinase 9 (CDK9) and cyclins T1 (CycT1) or T2 (CycT2), activates eukaryotic transcription elongation. In growing cells, P-TEFb exists in active and inactive forms. In the latter, it is incorporated into the 7SK small nuclear ribonucleoprotein, which contains hexamethylene bisacetamide-induced proteins (HEXIM) 1 or 2, La-related protein 7 (LaRP7), methyl phosphate capping enzyme, and 7SK small nuclear RNA (7SK). HEXIM1 inhibits the kinase activity of CDK9 via interactions between 7SK, HEXIM1, and CycT1. LaRP7 and methyl phosphate capping enzyme interact with 7SK independently of HEXIM1 and P-TEFb. To analyze genetic interactions between HEXIM1 and/or LaRP7 and 7SK using a cell-based system, we established artificial heterologous RNA tethering assays in which reporter gene expression depended on interactions between selected regions of 7SK and its cognate binding partners fused to a strong activator. This system enabled us to map the HEXIM1- and LaRP7- binding regions of 7SK. Assays with various mutant 7SK plasmid targets revealed that the 5'U-Ubulge and central loop of stem-loop I or RNA motif 3 of 7SK are required for transactivation, suggesting that HEXIM1 and CycT1 form a combinatorial binding surface for 7SK. Moreover, a region in HEXIM1 C-terminal to its previously mapped RNA-binding motif was also required for interactions between HEXIM1 and 7SK. Finally, a tyrosine-to-alanine mutation in HEXIM1, which is critical for its inhibitory effect on CDK9, changed HEXIM1 into an activator. These cell-based assays elucidate this important aspect of transcription elongation in vivo.
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Transcriptional Pause Release Is a Rate-Limiting Step for Somatic Cell Reprogramming. Cell Stem Cell 2014; 15:574-88. [DOI: 10.1016/j.stem.2014.09.018] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 08/07/2014] [Accepted: 09/26/2014] [Indexed: 02/07/2023]
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Kuzmina A, Verstraete N, Galker S, Maatook M, Bensaude O, Taube R. A single point mutation in cyclin T1 eliminates binding to Hexim1, Cdk9 and RNA but not to AFF4 and enforces repression of HIV transcription. Retrovirology 2014; 11:51. [PMID: 24985467 PMCID: PMC4226998 DOI: 10.1186/1742-4690-11-51] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 06/10/2014] [Indexed: 11/21/2022] Open
Abstract
Background Human immunodeficiency virus (HIV) gene expression is primarily regulated at the step of transcription elongation. The viral Tat protein recruits the Positive Transcription Elongation Factor b (P-TEFb) and the Super Elongation Complex (SEC) to the HIV promoter and enhances transcription by host RNA polymerase II. Results To map residues in the cyclin box of cyclin T1 that mediate the binding of P-TEFb to its interacting host partners and support HIV transcription, a pool of N-terminal cyclin T1 mutants was generated. Binding and functional assays in cells identified specific positions in cyclin T1 that are important for (i) association of P-TEFb with Hexim1, Cdk9 and SEC/AFF4 (ii) supporting Tat-transactivation in murine cells and (iii) inhibition of basal and Tat-dependent HIV transcription in human cells. Significantly, a unique cyclin T1 mutant where a Valine residue at position 107 was mutated to Glutamate (CycT1-V107E) was identified. CycT1-V107E did not bind to Hexim1 or Cdk9, and also could not assemble on HIV TAR or 7SK-snRNA. However, it bound strongly to AFF4 and its association with HIV Tat was slightly impaired. CycT1-V107E efficiently inhibited HIV replication in human T cell lines and in CD4(+) primary cells, and enforced HIV transcription repression in T cell lines that harbor a transcriptionally silenced integrated provirus. Conclusions This study outlines the mechanism by which CycT1-V107E mutant inhibits HIV transcription and enforces viral latency. It defines the importance of N-terminal residues of cyclin T1 in mediating contacts of P-TEFb with its transcription partners, and signifies the requirement of a functional P-TEFb and SEC in mediating HIV transcription.
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Affiliation(s)
| | | | | | | | | | - Ran Taube
- The Shraga Segal Department of Microbiology, Immunology and Genetics Faculty of Health Sciences, Ben-Gurion University of the Negev, P,O, Box 653, Beer-Sheva 84105, ISRAEL.
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Mbonye U, Karn J. Transcriptional control of HIV latency: cellular signaling pathways, epigenetics, happenstance and the hope for a cure. Virology 2014; 454-455:328-39. [PMID: 24565118 DOI: 10.1016/j.virol.2014.02.008] [Citation(s) in RCA: 178] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 01/23/2014] [Accepted: 02/07/2014] [Indexed: 02/06/2023]
Abstract
Replication-competent latent HIV-1 proviruses that persist in the genomes of a very small subset of resting memory T cells in infected individuals under life-long antiretroviral therapy present a major barrier towards viral eradication. Multiple molecular mechanisms are required to repress the viral trans-activating factor Tat and disrupt the regulatory Tat feedback circuit leading to the establishment of the latent viral reservoir. In particular, latency is due to a combination of transcriptional silencing of proviruses via host epigenetic mechanisms and restrictions on the expression of P-TEFb, an essential co-factor for Tat. Induction of latent proviruses in the presence of antiretroviral therapy is expected to enable clearance of latently infected cells by viral cytopathic effects and host antiviral immune responses. An in-depth comprehensive understanding of the molecular control of HIV-1 transcription should inform the development of optimal combinatorial reactivation strategies that are intended to purge the latent viral reservoir.
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Affiliation(s)
- Uri Mbonye
- Department of Molecular Biology and Microbiology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, United States
| | - Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, United States.
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Bagashev A, Sawaya BE. Roles and functions of HIV-1 Tat protein in the CNS: an overview. Virol J 2013; 10:358. [PMID: 24359561 PMCID: PMC3879180 DOI: 10.1186/1743-422x-10-358] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/06/2013] [Indexed: 01/01/2023] Open
Abstract
Nearly 50% of HIV-infected individuals suffer from some form of HIV-associated neurocognitive disorders (HAND). HIV-1 Tat (a key HIV transactivator of transcription) protein is one of the first HIV proteins to be expressed after infection occurs and is absolutely required for the initiation of the HIV genome transcription. In addition to its canonical functions, various studies have shown the deleterious role of HIV-1 Tat in the development and progression of HAND. Within the CNS, only specific cell types can support productive viral replication (astrocytes and microglia), however Tat protein can be released form infected cells to affects HIV non-permissive cells such as neurons. Therefore, in this review, we will summarize the functions of HIV-1 Tat proteins in neural cells and its ability to promote HAND.
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Affiliation(s)
| | - Bassel E Sawaya
- Molecular Studies of Neurodegenerative Diseases Lab, The Fels Institute for Cancer Research & Molecular Biology, Philadelphia, PA 19140, USA.
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27
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Abstract
The implementation of new antiretroviral therapies targeting transcription of early viral proteins in postintegrated HIV-1 can aid in overcoming current therapy limitations. Using high-throughput screening assays, we have previously described a novel Tat-dependent HIV-1 transcriptional inhibitor named 6-bromoindirubin-3'-oxime (6BIO). The screening of 6BIO derivatives yielded unique compounds that show potent inhibition of HIV-1 transcription. We have identified a second-generation derivative called 18BIOder as an inhibitor of HIV-1 Tat-dependent transcription in TZM-bl cells and a potent inhibitor of GSK-3β kinase in vitro. Structurally, 18BIOder is half the molecular weight and structure of its parental compound, 6BIO. More importantly, we also have found a different GSK-3β complex present only in HIV-1-infected cells. 18BIOder preferentially inhibits this novel kinase complex from infected cells at nanomolar concentrations. Finally, we observed that neuronal cultures treated with Tat protein are protected from Tat-mediated cytotoxicity when treated with 18BIOder. Overall, our data suggest that HIV-1 Tat-dependent transcription is sensitive to small-molecule inhibition of GSK-3β.
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28
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Jiang L, Huang Y, Deng M, Liu T, Lai W, Ye X. Polo-like kinase 1 inhibits the activity of positive transcription elongation factor of RNA Pol II b (P-TEFb). PLoS One 2013; 8:e72289. [PMID: 23977272 PMCID: PMC3745420 DOI: 10.1371/journal.pone.0072289] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/15/2013] [Indexed: 11/19/2022] Open
Abstract
Polo-like kinase 1 (Plk1) is a highly conserved Ser/Thr kinase in eukaryotes and plays a critical role in various aspects of the cell cycle. Plk1 exerts its multiple functions by phosphorylating its substrates. In this study, we found that Plk1 can interact with cyclin T1/Cdk9 complex-the main form of the positive transcription elongation complex b (P-TEFb), and its C-terminal polo-box domain is responsible for the binding. Further analysis indicated that Plk1 could phosphorylate cyclin T1 at Ser564 and inhibit the kinase activity of cyclin T1/Cdk9 complex on phosphorylation of the C-terminal domain (CTD) of RNA polymerase II. By taking the approach of luciferase assay, we demonstrated that over-expression of both wild type Plk1 and constitutively active form of Plk1 inhibits the P-TEFb dependent HIV-1 LTR transcription, while knockdown of Plk1 increases the HIV-1 LTR transcription. Consistently, the data from the HIV-1 pseudovirus reporter assay indicated that Plk1 blocks the gene expression of HIV-1 pseudovirus. Taken together, our results revealed that Plk1 negatively regulates the RNA polymerase II-dependent transcription through inhibiting the activity of cyclin T1/Cdk9 complex.
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Affiliation(s)
- Liangzhen Jiang
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
- Graduate University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Yan Huang
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
- Graduate University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Min Deng
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
- Graduate University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Ting Liu
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
- Graduate University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Wenbin Lai
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
- Graduate University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Xin Ye
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P. R. China
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29
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Karn J, Stoltzfus CM. Transcriptional and posttranscriptional regulation of HIV-1 gene expression. Cold Spring Harb Perspect Med 2013; 2:a006916. [PMID: 22355797 DOI: 10.1101/cshperspect.a006916] [Citation(s) in RCA: 276] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Control of HIV-1 gene expression depends on two viral regulatory proteins, Tat and Rev. Tat stimulates transcription elongation by directing the cellular transcriptional elongation factor P-TEFb to nascent RNA polymerases. Rev is required for the transport from the nucleus to the cytoplasm of the unspliced and incompletely spliced mRNAs that encode the structural proteins of the virus. Molecular studies of both proteins have revealed how they interact with the cellular machinery to control transcription from the viral LTR and regulate the levels of spliced and unspliced mRNAs. The regulatory feedback mechanisms driven by HIV-1 Tat and Rev ensure that HIV-1 transcription proceeds through distinct phases. In cells that are not fully activated, limiting levels of Tat and Rev act as potent blocks to premature virus production.
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Affiliation(s)
- Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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30
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Kim S, Min IM, Ren S, Spector A, Jin MM, Lis JT. Development of temperature-sensitive mutants of the Drosophila melanogaster P-TEFb (Cyclin T/CDK9) heterodimer using yeast two-hybrid screening. Biochem Biophys Res Commun 2013; 433:243-8. [PMID: 23500466 DOI: 10.1016/j.bbrc.2013.02.091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 02/28/2013] [Indexed: 10/27/2022]
Abstract
P-TEFb complex, a heterodimer of the kinase CDK9 and Cyclin T, is a critical factor that stimulates the process of transcription elongation. Here, we explored a fast and large-scale screening method to induce a temperature-dependent conditional disruption of the CDK9/Cyclin T interaction and developed an assay to validate their mutant phenotypes in a biological context. First, we used the yeast two-hybrid system to screen Drosophila melanogaster Cyclin T mutants at a large scale for temperature or cold sensitive (TS or CS) CDK9 interaction phenotypes. The isolated P-TEFb TS mutants were then expressed in Drosophila cells and were investigated for their effects on Drosophila hsp70 transcriptional activity. Our results showed that these P-TEFb TS mutants had a reduced level of hsp70 transcription at restrictive temperatures. A model structure of the Cyclin T and CDK9 complex suggested that the key TS mutations were found within the α2- and α3-helices at the interface of the complex, which may disrupt the binding of Cyclin T to CDK9 directly or indirectly by affecting the conformation of Cyclin T. The yeast two-hybrid-based screening strategy described here for isolating TS or CS interaction phenotypes can be directly applicable to other complexes in higher organisms. The use of TS or CS mutants will enable a 'real-time and reversible perturbation' restricted to specific protein-protein interactions, providing a mechanistic insight into the biological process mediated by a target complex.
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Affiliation(s)
- Soyoun Kim
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
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31
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Abstract
Current assays for quantification of HIV-1 virions rely on real-time reverse transcriptase (RT)-PCR detection of conserved regions of HIV-1 RNA and can be limited by detection of contaminating viral or plasmid DNA. We developed a novel RT-PCR assay using a reverse primer that hybridizes with the poly(A) tail of HIV-1 mRNAs, anchored by conserved viral nucleotides at the most distal region of the transcript. This assay can detect and quantify HIV-1 RNA with high specificity and sensitivity.
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32
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Mousseau G, Clementz MA, Bakeman WN, Nagarsheth N, Cameron M, Shi J, Baran P, Fromentin R, Chomont N, Valente ST. An analog of the natural steroidal alkaloid cortistatin A potently suppresses Tat-dependent HIV transcription. Cell Host Microbe 2013; 12:97-108. [PMID: 22817991 DOI: 10.1016/j.chom.2012.05.016] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 04/03/2012] [Accepted: 05/14/2012] [Indexed: 12/11/2022]
Abstract
The human immunodeficiency virus type 1 (HIV) Tat protein, a potent activator of HIV gene expression, is essential for integrated viral genome expression and represents a potential antiviral target. Tat binds the 5'-terminal region of HIV mRNA's stem-bulge-loop structure, the transactivation-responsive (TAR) element, to activate transcription. We find that didehydro-Cortistatin A (dCA), an analog of a natural steroidal alkaloid from a marine sponge, inhibits Tat-mediated transactivation of the integrated provirus by binding specifically to the TAR-binding domain of Tat. Working at subnanomolar concentrations, dCA reduces Tat-mediated transcriptional initiation/elongation from the viral promoter to inhibit HIV-1 and HIV-2 replication in acutely and chronically infected cells. Importantly, dCA abrogates spontaneous viral particle release from CD4(+)T cells from virally suppressed subjects on highly active antiretroviral therapy (HAART). Thus, dCA defines a unique class of anti-HIV drugs that may inhibit viral production from stable reservoirs and reduce residual viremia during HAART.
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MESH Headings
- Alkaloids/chemical synthesis
- Alkaloids/chemistry
- Alkaloids/pharmacokinetics
- Alkaloids/pharmacology
- Animals
- Anti-HIV Agents/pharmacology
- Antiretroviral Therapy, Highly Active
- Binding Sites
- CD4-Positive T-Lymphocytes/virology
- Cells, Cultured/drug effects
- Cells, Cultured/virology
- Female
- Gene Expression Regulation, Viral/drug effects
- HIV Core Protein p24/metabolism
- HIV Infections/drug therapy
- HIV Infections/virology
- HIV-1/drug effects
- HIV-1/genetics
- HIV-1/physiology
- Heterocyclic Compounds, 4 or More Rings/pharmacology
- Humans
- Isoquinolines/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Microsomes, Liver/drug effects
- Polycyclic Compounds/chemistry
- Promoter Regions, Genetic
- Proviruses/drug effects
- Proviruses/genetics
- Transcription, Genetic/drug effects
- Virus Replication/drug effects
- tat Gene Products, Human Immunodeficiency Virus/antagonists & inhibitors
- tat Gene Products, Human Immunodeficiency Virus/genetics
- tat Gene Products, Human Immunodeficiency Virus/metabolism
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Affiliation(s)
- Guillaume Mousseau
- Department of Infectology, The Scripps Research Institute, Scripps Florida, Jupiter, 33458, USA
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33
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Hsin JP, Manley JL. The RNA polymerase II CTD coordinates transcription and RNA processing. Genes Dev 2012; 26:2119-37. [PMID: 23028141 DOI: 10.1101/gad.200303.112] [Citation(s) in RCA: 461] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The C-terminal domain (CTD) of the RNA polymerase II largest subunit consists of multiple heptad repeats (consensus Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7), varying in number from 26 in yeast to 52 in vertebrates. The CTD functions to help couple transcription and processing of the nascent RNA and also plays roles in transcription elongation and termination. The CTD is subject to extensive post-translational modification, most notably phosphorylation, during the transcription cycle, which modulates its activities in the above processes. Therefore, understanding the nature of CTD modifications, including how they function and how they are regulated, is essential to understanding the mechanisms that control gene expression. While the significance of phosphorylation of Ser2 and Ser5 residues has been studied and appreciated for some time, several additional modifications have more recently been added to the CTD repertoire, and insight into their function has begun to emerge. Here, we review findings regarding modification and function of the CTD, highlighting the important role this unique domain plays in coordinating gene activity.
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Affiliation(s)
- Jing-Ping Hsin
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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34
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Devaiah BN, Singer DS. Cross-talk among RNA polymerase II kinases modulates C-terminal domain phosphorylation. J Biol Chem 2012; 287:38755-66. [PMID: 23027873 DOI: 10.1074/jbc.m112.412015] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The RNA polymerase II (Pol II) C-terminal domain (CTD) serves as a docking site for numerous proteins, bridging various nuclear processes to transcription. The recruitment of these proteins is mediated by CTD phospho-epitopes generated during transcription. The mechanisms regulating the kinases that establish these phosphorylation patterns on the CTD are not known. We report that three CTD kinases, CDK7, CDK9, and BRD4, engage in cross-talk, modulating their subsequent CTD phosphorylation. BRD4 phosphorylates PTEFb/CDK9 at either Thr-29 or Thr-186, depending on its relative abundance, which represses or activates CDK9 CTD kinase activity, respectively. Conversely, CDK9 phosphorylates BRD4 enhancing its CTD kinase activity. The CTD Ser-5 kinase CDK7 also interacts with and phosphorylates BRD4, potently inhibiting BRD4 kinase activity. Additionally, the three kinases regulate each other indirectly through the general transcription factor TAF7. An inhibitor of CDK9 and CDK7 CTD kinase activities, TAF7 also binds to BRD4 and inhibits its kinase activity. Each of these kinases phosphorylates TAF7, affecting its subsequent ability to inhibit the other two. Thus, a complex regulatory network governs Pol II CTD kinases.
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Affiliation(s)
- Ballachanda N Devaiah
- Experimental Immunology Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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35
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Transition step during assembly of HIV Tat:P-TEFb transcription complexes and transfer to TAR RNA. Mol Cell Biol 2012; 32:4780-93. [PMID: 23007159 DOI: 10.1128/mcb.00206-12] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Transcription factors regulate eukaryotic RNA polymerase II (Pol II) activity by assembling and remodeling complexes at multiple steps in the transcription cycle. In HIV, we previously proposed a two-step model where the viral Tat protein first preassembles at the promoter with an inactive P-TEFb:7SK snRNP complex and later transfers P-TEFb to TAR on the nascent transcript, displacing the inhibitory snRNP and resulting in Pol II phosphorylation and stimulation of elongation. It is unknown how the Tat:P-TEFb complex transitions to TAR to activate the P-TEFb kinase. Here, we show that P-TEFb artificially recruited to the nascent transcript is not competent for transcription but rather remains inactive due to its assembly with the 7SK snRNP. Tat supplied in trans is able to displace the kinase inhibitor Hexim1 from the snRNP and activate P-TEFb, thereby uncoupling Tat requirements for kinase activation and TAR binding. By combining comprehensive mutagenesis of Tat with multiple cell-based reporter assays that probe the activity of Tat in different arrangements, we genetically defined a transition step in which preassembled Tat:P-TEFb complexes switch to TAR. We propose that a conserved network of residues in Tat has evolved to control this transition and thereby switch the host elongation machinery to viral transcription.
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36
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Abstract
Three-dimensional molecular structures can provide detailed information on biological mechanisms and, for cases in which the molecular function affects human health, can significantly aid in the development of therapeutic interventions. For almost 25 years, key components of the lentivirus HIV-1, including the envelope glycoproteins, the capsid and the replication enzymes reverse transcriptase, integrase and protease, have been scrutinized to near atomic-scale resolution. Moreover, structural analyses of the interactions between viral and host cell components have yielded key insights into the mechanisms of viral entry, chromosomal integration, transcription and egress from cells. Here, we review recent advances in HIV-1 structural biology, focusing on the molecular mechanisms of viral replication and on the development of new therapeutics.
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37
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Kinase control prevents HIV-1 reactivation in spite of high levels of induced NF-κB activity. J Virol 2012; 86:4548-58. [PMID: 22345467 DOI: 10.1128/jvi.06726-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Despite its clinical importance, the molecular biology of HIV-1 latency control is at best partially understood, and the literature remains conflicting. The most recent description that latent HIV-1 is integrated into actively expressed host genes has further confounded the situation. This lack of molecular understanding complicates our efforts to identify therapeutic compounds or strategies that could reactivate latent HIV-1 infection in patients, a prerequisite for the eradication of HIV-1 infection. Currently, many therapeutic development efforts operate under the assumption that a restrictive histone code could govern latent infection and that either dissipation of the histone-based restrictions or NF-κB activation could be sufficient to trigger HIV-1 reactivation. We here present data that suggest an additional, higher level of molecular control. During a high-content drug screening effort, we identified AS601245 as a potent inhibitor of HIV-1 reactivation in latently infected primary T cells and T cell lines. In either system, AS601245 inhibited HIV-1 reactivation despite high levels of induced NF-κB activation. This finding suggests the presence of a gatekeeper kinase activity that controls latent HIV-1 infection even in the presence of high levels of NF-κB activity. Potential therapeutic stimuli that do not target this gatekeeper kinase will likely fail to trigger efficient system-wide HIV-1 reactivation.
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38
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Toossi Z, Wu M, Hirsch CS, Mayanja-Kizza H, Baseke J, Aung H, Canaday DH, Fujinaga K. Activation of P-TEFb at sites of dual HIV/TB infection, and inhibition of MTB-induced HIV transcriptional activation by the inhibitor of CDK9, Indirubin-3'-monoxime. AIDS Res Hum Retroviruses 2012; 28:182-7. [PMID: 21453127 DOI: 10.1089/aid.2010.0211] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
At sites of Mycobacterium tuberculosis (MTB) infection, HIV-1 replication is increased during tuberculosis (TB). Here we investigated the role of positive transcription elongation factor (P-TEFb), comprised of CycT1 and CDK9, as the cellular cofactor of HIV-1 Tat protein in transcriptional activation of HIV-1 in mononuclear cells from HIV-1-infected patients with pleural TB. Expression of CycT1 in response to MTB was assessed in mononuclear cells from pleural fluid (PFMC) and blood (PBMC) from HIV/TB patients with pleural TB, and in blood monocytes (MN) from singly infected HIV-1-seropositive subjects. We then examined whether the CDK9 inhibitor, Indirubin 3'-monoxime (IM), was effective in inhibition of MTB-induced HIV-1 mRNA expression. We found higher expression of CycT1 mRNA in PFMCs as compared to PBMCs from HIV/TB-coinfected subjects. MTB induced the expression of CycT1 and HIV-1 gag/pol mRNA in both PFMCs from HIV/TB subjects and MN from HIV-1-infected subjects. CycT1 protein was also induced by MTB stimulation in PFMCs from HIV/TB patients, and both MN and in vitro-derived macrophages. Inhibition of CDK9 by IM in both PFMCs from HIV/TB and MN from HIV-1-infected subjects in response to MTB led to inhibition of HIV-1 mRNA expression. These data imply that IM may be useful as an adjunctive therapy in control of HIV-1 replication in HIV/TB dually infected subjects.
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Affiliation(s)
- Zahra Toossi
- Case Western Reserve University, Cleveland, Ohio
- Veterans Affairs Medical Center, Cleveland, Ohio
| | - Mianda Wu
- Case Western Reserve University, Cleveland, Ohio
| | | | - Harriet Mayanja-Kizza
- Makerere University and National Tuberculosis and Leprosy Program, Kampala, Uganda
- Joint Clinical Research Center, Kampala, Uganda
| | - Joy Baseke
- Joint Clinical Research Center, Kampala, Uganda
| | - Htin Aung
- Case Western Reserve University, Cleveland, Ohio
| | | | - Koh Fujinaga
- Case Western Reserve University, Cleveland, Ohio
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39
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Mbonye U, Karn J. Control of HIV latency by epigenetic and non-epigenetic mechanisms. Curr HIV Res 2011; 9:554-67. [PMID: 22211660 PMCID: PMC3319922 DOI: 10.2174/157016211798998736] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 10/10/2011] [Accepted: 10/21/2011] [Indexed: 12/17/2022]
Abstract
Intensive antiretroviral therapy successfully suppresses viral replication but is unable to eradicate the virus. HIV persists in a small number of resting memory T cells where HIV has been transcriptionally silenced. This review will focus on recent insights into the HIV transcriptional control mechanisms that provide the biochemical basis for understanding latency. There are no specific repressors of HIV transcription encoded by the virus, instead latency arises when the regulatory feedback mechanism driven by HIV Tat expression is disrupted. Small changes in transcriptional initiation, induced by epigenetic silencing, lead to profound restrictions in Tat levels and force the entry of proviruses into latency. In resting memory T cells, which carry the bulk of the latent viral pool, additional restrictions, especially the limiting cellular levels of the essential Tat cofactor P-TEFb and the transcription initiation factors NF-κB and NFAT ensure that the provirus remains silenced unless the host cell is activated. The detailed understanding of HIV transcription is providing a framework for devising new therapeutic strategies designed to purge the latent viral pool. Importantly, the recognition that there are multiple restrictions imposed on latent proviruses suggest that proviral reactivation will not be achieved when only a single reactivation step is targeted and that any optimal activation strategy will require both removal of epigenetic blocks and the activation of P-TEFb.
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Affiliation(s)
| | - Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106, USA
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40
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Kehn-Hall K, Guendel I, Carpio L, Skaltsounis L, Meijer L, Al-Harthi L, Steiner JP, Nath A, Kutsch O, Kashanchi F. Inhibition of Tat-mediated HIV-1 replication and neurotoxicity by novel GSK3-beta inhibitors. Virology 2011; 415:56-68. [PMID: 21514616 DOI: 10.1016/j.virol.2011.03.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 01/10/2011] [Accepted: 03/27/2011] [Indexed: 10/18/2022]
Abstract
The HIV-1 protein Tat is a critical regulator of viral transcription and has also been implicated as a mediator of HIV-1 induced neurotoxicity. Here using a high throughput screening assay, we identified the GSK-3 inhibitor 6BIO, as a Tat-dependent HIV-1 transcriptional inhibitor. Its ability to inhibit HIV-1 transcription was confirmed in TZM-bl cells, with an IC(50) of 40nM. Through screening 6BIO derivatives, we identified 6BIOder, which has a lower IC(50) of 4nM in primary macrophages and 0.5nM in astrocytes infected with HIV-1. 6BIOder displayed an IC(50) value of 0.03nM through in vitro GSK-3β kinase inhibition assays. Finally, we demonstrated 6BIO and 6BIOder have neuroprotective effects on Tat induced cell death in rat mixed hippocampal cultures. Therefore 6BIO and its derivatives are unique compounds which, due to their complex mechanisms of action, are able to inhibit HIV-1 transcription as well as to protect against Tat induced neurotoxicity.
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Affiliation(s)
- Kylene Kehn-Hall
- Department of Molecular and Microbiology, National Center for Biodefense & Infectious Diseases, George Mason University, Manassas, VA 20110, USA
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41
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Razooky BS, Weinberger LS. Mapping the architecture of the HIV-1 Tat circuit: A decision-making circuit that lacks bistability and exploits stochastic noise. Methods 2011; 53:68-77. [PMID: 21167940 PMCID: PMC4096296 DOI: 10.1016/j.ymeth.2010.12.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2010] [Indexed: 01/02/2023] Open
Abstract
Upon infection of a CD4(+) T cell, HIV-1 appears to 'choose' between two alternate fates: active replication or a long-lived dormant state termed proviral latency. A transcriptional positive-feedback loop generated by the HIV-1 Tat protein appears sufficient to mediate this decision. Here, we describe a coupled wet-lab and computational approach that uses mathematical modeling and live-cell time-lapse microscopy to map the architecture of the HIV-1 Tat transcriptional regulatory circuit and generate predictive models of HIV-1 latency. This approach provided the first characterization of a 'decision-making' circuit that lacks bistability and instead exploits stochastic fluctuations in cellular molecules (i.e. noise) to generate a decision between an on or off transcriptional state.
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Affiliation(s)
- Brandon S. Razooky
- Department of Chemistry and Biochemistry, U niversity of California, San Diego 9500 Gilman Drive #0314, La Jolla, CA 92093-0314
| | - Leor S. Weinberger
- Department of Chemistry and Biochemistry, U niversity of California, San Diego 9500 Gilman Drive #0314, La Jolla, CA 92093-0314
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42
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Khurana B, Zhuang L, Moitra PK, Stantchev TS, Broder CC, Cutler ML, D'Arpa P. Human TOP1 residues implicated in species specificity of HIV-1 infection are required for interaction with BTBD2, and RNAi of BTBD2 in old world monkey and human cells increases permissiveness to HIV-1 infection. Virol J 2010; 7:332. [PMID: 21092135 PMCID: PMC3002306 DOI: 10.1186/1743-422x-7-332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2010] [Accepted: 11/20/2010] [Indexed: 11/29/2022] Open
Abstract
Background Host determinants of HIV-1 viral tropism include factors from producer cells that affect the efficiency of productive infection and factors in target cells that block infection after viral entry. TRIM5α restricts HIV-1 infection at an early post-entry step through a mechanism associated with rapid disassembly of the retroviral capsid. Topoisomerase I (TOP1) appears to play a role in HIV-1 viral tropism by incorporating into or otherwise modulating virions affecting the efficiency of a post-entry step, as the expression of human TOP1 in African Green Monkey (AGM) virion-producing cells increased the infectivity of progeny virions by five-fold. This infectivity enhancement required human TOP1 residues 236 and 237 as their replacement with the AGM counterpart residues abolished the infectivity enhancement. Our previous studies showed that TOP1 interacts with BTBD1 and BTBD2, two proteins which co-localize with the TRIM5α splice variant TRIM5δ in cytoplasmic bodies. Because BTBD1 and BTBD2 interact with one HIV-1 viral tropism factor, TOP1, and co-localize with a splice variant of another, we investigated the potential involvement of BTBD1 and BTBD2 in HIV-1 restriction. Results We show that the interaction of BTBD1 and BTBD2 with TOP1 requires hu-TOP1 residues 236 and 237, the same residues required to enhance the infectivity of progeny virions when hu-TOP1 is expressed in AGM producer cells. Additionally, interference with the expression of BTBD2 in AGM and human 293T target cells increased their permissiveness to HIV-1 infection two- to three-fold. Conclusions These results do not exclude the possibility that BTBD2 may modestly restrict HIV-1 infection via colocation with TRIM5 variants in cytoplasmic bodies.
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Affiliation(s)
- Bharat Khurana
- Department of Pathology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
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Cyclin T1/CDK9 interacts with influenza A virus polymerase and facilitates its association with cellular RNA polymerase II. J Virol 2010; 84:12619-27. [PMID: 20943989 DOI: 10.1128/jvi.01696-10] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Influenza virus RNA-dependent RNA polymerase scavenges the 5' cap from host pre-mRNA to prime viral transcription initiation. It is also well established that viral RNA-dependent RNA polymerase (vRNP) associates with cellular RNA polymerase II (Pol II), on which viral replication depends. Here we report that cyclin T1/CDK9 can interact with influenza virus polymerase and facilitate its association with cellular Pol II. The immunodepletion of cyclin T1/CDK9 totally abolished the association of vRNP with the C-terminal domain (CTD) Ser-2-phosphorylated form of RNA polymerase II. Further studies showed that overexpression of cyclin T1/CDK9 increased the transcription activity of vRNP, while knockdown of cyclin T1/CDK9 impaired viral replication. Our results suggest that cyclin T1/CDK9 serves as an adapter to mediate the interaction of vRNP and RNA Pol II and promote viral transcription.
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High natural permissivity of primary rabbit cells for HIV-1, with a virion infectivity defect in macrophages as the final replication barrier. J Virol 2010; 84:12300-14. [PMID: 20861260 DOI: 10.1128/jvi.01607-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
An immunocompetent, permissive, small-animal model would be valuable for the study of human immunodeficiency virus type 1 (HIV-1) pathogenesis and for the testing of drug and vaccine candidates. However, the development of such a model has been hampered by the inability of primary rodent cells to efficiently support several steps of the HIV-1 replication cycle. Although transgenesis of the HIV receptor complex and human cyclin T1 have been beneficial, additional late-phase blocks prevent robust replication of HIV-1 in rodents and limit the range of in vivo applications. In this study, we explored the HIV-1 susceptibility of rabbit primary T cells and macrophages. Envelope-specific and coreceptor-dependent entry of HIV-1 was achieved by expressing human CD4 and CCR5. A block of HIV-1 DNA synthesis, likely mediated by TRIM5, was overcome by limited changes to the HIV-1 gag gene. Unlike with mice and rats, primary cells from rabbits supported the functions of the regulatory viral proteins Tat and Rev, Gag processing, and the release of HIV-1 particles at levels comparable to those in human cells. While HIV-1 produced by rabbit T cells was highly infectious, a macrophage-specific infectivity defect became manifest by a complex pattern of mutations in the viral genome, only part of which were deamination dependent. These results demonstrate a considerable natural HIV-1 permissivity of the rabbit species and suggest that receptor complex transgenesis combined with modifications in gag and possibly vif of HIV-1 to evade species-specific restriction factors might render lagomorphs fully permissive to infection by this pathogenic human lentivirus.
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Crystal structure of HIV-1 Tat complexed with human P-TEFb. Nature 2010; 465:747-51. [PMID: 20535204 PMCID: PMC2885016 DOI: 10.1038/nature09131] [Citation(s) in RCA: 222] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 04/27/2010] [Indexed: 01/07/2023]
Abstract
Regulation of the expression of the human immunodeficiency virus (HIV) genome is accomplished in large part by controlling transcription elongation. The viral protein Tat hijacks the host cell's RNA polymerase II elongation control machinery through interaction with the positive transcription elongation factor, P-TEFb, and directs the factor to promote productive elongation of HIV mRNA. Here we describe the crystal structure of the Tat.P-TEFb complex containing HIV-1 Tat, human Cdk9 (also known as CDK9), and human cyclin T1 (also known as CCNT1). Tat adopts a structure complementary to the surface of P-TEFb and makes extensive contacts, mainly with the cyclin T1 subunit of P-TEFb, but also with the T-loop of the Cdk9 subunit. The structure provides a plausible explanation for the tolerance of Tat to sequence variations at certain sites. Importantly, Tat induces significant conformational changes in P-TEFb. This finding lays a foundation for the design of compounds that would specifically inhibit the Tat.P-TEFb complex and block HIV replication.
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Michel N, Goffinet C, Ganter K, Allespach I, Kewalramani VN, Saifuddin M, Littman DR, Greene WC, Goldsmith MA, Keppler OT. Human cyclin T1 expression ameliorates a T-cell-specific transcriptional limitation for HIV in transgenic rats, but is not sufficient for a spreading infection of prototypic R5 HIV-1 strains ex vivo. Retrovirology 2009; 6:2. [PMID: 19144136 PMCID: PMC2631513 DOI: 10.1186/1742-4690-6-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 01/13/2009] [Indexed: 12/20/2022] Open
Abstract
Background Cells derived from native rodents have limits at distinct steps of HIV replication. Rat primary CD4 T-cells, but not macrophages, display a profound transcriptional deficit that is ameliorated by transient trans-complementation with the human Tat-interacting protein Cyclin T1 (hCycT1). Results Here, we generated transgenic rats that selectively express hCycT1 in CD4 T-cells and macrophages. hCycT1 expression in rat T-cells boosted early HIV gene expression to levels approaching those in infected primary human T-cells. hCycT1 expression was necessary, but not sufficient, to enhance HIV transcription in T-cells from individual transgenic animals, indicating that endogenous cellular factors are critical co-regulators of HIV gene expression in rats. T-cells from hCD4/hCCR5/hCycT1-transgenic rats did not support productive infection of prototypic wild-type R5 HIV-1 strains ex vivo, suggesting one or more significant limitation in the late phase of the replication cycle in this primary rodent cell type. Remarkably, we identify a replication-competent HIV-1 GFP reporter strain (R7/3 YU-2 Env) that displays characteristics of a spreading, primarily cell-to-cell-mediated infection in primary T-cells from hCD4/hCCR5-transgenic rats. Moreover, the replication of this recombinant HIV-1 strain was significantly enhanced by hCycT1 transgenesis. The viral determinants of this so far unique replicative ability are currently unknown. Conclusion Thus, hCycT1 expression is beneficial to de novo HIV infection in a transgenic rat model, but additional genetic manipulations of the host or virus are required to achieve full permissivity.
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Affiliation(s)
- Nico Michel
- Department of Virology, University of Heidelberg, 69120 Heidelberg, Germany.
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Burnett JC, Miller-Jensen K, Shah PS, Arkin AP, Schaffer DV. Control of stochastic gene expression by host factors at the HIV promoter. PLoS Pathog 2009; 5:e1000260. [PMID: 19132086 PMCID: PMC2607019 DOI: 10.1371/journal.ppat.1000260] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 12/09/2008] [Indexed: 12/21/2022] Open
Abstract
The HIV promoter within the viral long terminal repeat (LTR) orchestrates many aspects of the viral life cycle, from the dynamics of viral gene expression and replication to the establishment of a latent state. In particular, after viral integration into the host genome, stochastic fluctuations in viral gene expression amplified by the Tat positive feedback loop can contribute to the formation of either a productive, transactivated state or an inactive state. In a significant fraction of cells harboring an integrated copy of the HIV-1 model provirus (LTR-GFP-IRES-Tat), this bimodal gene expression profile is dynamic, as cells spontaneously and continuously flip between active (Bright) and inactive (Off) expression modes. Furthermore, these switching dynamics may contribute to the establishment and maintenance of proviral latency, because after viral integration long delays in gene expression can occur before viral transactivation. The HIV-1 promoter contains cis-acting Sp1 and NF-κB elements that regulate gene expression via the recruitment of both activating and repressing complexes. We hypothesized that interplay in the recruitment of such positive and negative factors could modulate the stability of the Bright and Off modes and thereby alter the sensitivity of viral gene expression to stochastic fluctuations in the Tat feedback loop. Using model lentivirus variants with mutations introduced in the Sp1 and NF-κB elements, we employed flow cytometry, mRNA quantification, pharmacological perturbations, and chromatin immunoprecipitation to reveal significant functional differences in contributions of each site to viral gene regulation. Specifically, the Sp1 sites apparently stabilize both the Bright and the Off states, such that their mutation promotes noisy gene expression and reduction in the regulation of histone acetylation and deacetylation. Furthermore, the NF-κB sites exhibit distinct properties, with κB site I serving a stronger activating role than κB site II. Moreover, Sp1 site III plays a particularly important role in the recruitment of both p300 and RelA to the promoter. Finally, analysis of 362 clonal cell populations infected with the viral variants revealed that mutations in any of the Sp1 sites yield a 6-fold higher frequency of clonal bifurcation compared to that of the wild-type promoter. Thus, each Sp1 and NF-κB site differentially contributes to the regulation of viral gene expression, and Sp1 sites functionally “dampen” transcriptional noise and thereby modulate the frequency and maintenance of this model of viral latency. These results may have biomedical implications for the treatment of HIV latency. After HIV genome integration into the host chromosome, the viral promoter coordinates a complex set of inputs to control the establishment of viral latency, the onset of viral gene expression, and the ensuing gene expression levels. Among these inputs are chromatin structure at the site of integration, host transcription factors, and the virally encoded transcriptional regulator Tat. Importantly, transcriptional noise from host and viral transcriptional regulators may play a critical role in the decision between replication versus latency, because stochastic fluctuations in gene expression are amplified by a Tat-mediated positive transcriptional feedback loop. To evaluate the individual contributions of key transcription factor binding elements in gene expression dynamics, we employ model HIV viruses with mutations introduced into numerous promoter elements. Extensive analysis of gene expression dynamics and transcription factor recruitment to the viral promoter reveals that each site differentially contributes to viral gene expression and to the establishment of a low expression state that may contribute to viral latency. This systems-level approach elucidates the synergistic contributions of host and viral factors to the dynamics, magnitudes, and stochastic effects in viral gene expression, as well as provides insights into mechanisms that contribute to proviral latency.
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Affiliation(s)
- John C Burnett
- Department of Chemical Engineering and the Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
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Gilchrist DA, Nechaev S, Lee C, Ghosh SKB, Collins JB, Li L, Gilmour DS, Adelman K. NELF-mediated stalling of Pol II can enhance gene expression by blocking promoter-proximal nucleosome assembly. Genes Dev 2008; 22:1921-33. [PMID: 18628398 DOI: 10.1101/gad.1643208] [Citation(s) in RCA: 232] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Negative Elongation Factor (NELF) is a transcription regulatory complex that induces stalling of RNA polymerase II (Pol II) during early transcription elongation and represses expression of several genes studied to date, including Drosophila Hsp70, mammalian proto-oncogene junB, and HIV RNA. To determine the full spectrum of NELF target genes in Drosophila, we performed a microarray analysis of S2 cells depleted of NELF and discovered that NELF RNAi affects many rapidly inducible genes involved in cellular responses to stimuli. Surprisingly, only one-third of NELF target genes were, like Hsp70, up-regulated by NELF-depletion, whereas the majority of target genes showed decreased expression levels upon NELF RNAi. Our data reveal that the presence of stalled Pol II at this latter group of genes enhances gene expression by maintaining a permissive chromatin architecture around the promoter-proximal region, and that loss of Pol II stalling at these promoters is accompanied by a significant increase in nucleosome occupancy and a decrease in histone H3 Lys 4 trimethylation. These findings identify a novel, positive role for stalled Pol II in regulating gene expression and suggest that there is a dynamic interplay between stalled Pol II and chromatin structure.
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Affiliation(s)
- Daniel A Gilchrist
- Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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Acetylation of conserved lysines in the catalytic core of cyclin-dependent kinase 9 inhibits kinase activity and regulates transcription. Mol Cell Biol 2008; 28:2201-12. [PMID: 18250157 DOI: 10.1128/mcb.01557-07] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Promoter clearance and transcriptional processivity in eukaryotic cells are fundamentally regulated by the phosphorylation of the carboxy-terminal domain of RNA polymerase II (RNAPII). One of the kinases that essentially performs this function is P-TEFb (positive transcription elongation factor b), which is composed of cyclin-dependent kinase 9 (CDK9) associated with members of the cyclin T family. Here we show that cellular GCN5 and P/CAF, members of the GCN5-related N-acetyltransferase family of histone acetyltransferases, regulate CDK9 function by specifically acetylating the catalytic core of the enzyme and, in particular, a lysine that is essential for ATP coordination and the phosphotransfer reaction. Acetylation markedly reduces both the kinase function and transcriptional activity of P-TEFb. In contrast to unmodified CDK9, the acetylated fraction of the enzyme is specifically found in the insoluble nuclear matrix compartment. Acetylated CDK9 associates with the transcriptionally silent human immunodeficiency virus type 1 provirus; upon transcriptional activation, it is replaced by the unmodified form, which is involved in the elongating phase of transcription marked by Ser2-phosphorylated RNAPII. Given the conservation of the CDK9 acetylated residues in the catalytic task of virtually all CDK proteins, we anticipate that this mechanism of regulation might play a broader role in controlling the function of other members of this kinase family.
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Vardabasso C, Manganaro L, Lusic M, Marcello A, Giacca M. The histone chaperone protein Nucleosome Assembly Protein-1 (hNAP-1) binds HIV-1 Tat and promotes viral transcription. Retrovirology 2008; 5:8. [PMID: 18226242 PMCID: PMC2266780 DOI: 10.1186/1742-4690-5-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2007] [Accepted: 01/28/2008] [Indexed: 12/22/2022] Open
Abstract
Background Despite the large amount of data available on the molecular mechanisms that regulate HIV-1 transcription, crucial information is still lacking about the interplay between chromatin conformation and the events that regulate initiation and elongation of viral transcription. During transcriptional activation, histone acetyltransferases and ATP-dependent chromatin remodeling complexes cooperate with histone chaperones in altering chromatin structure. In particular, human Nucleosome Assembly Protein-1 (hNAP-1) is known to act as a histone chaperone that shuttles histones H2A/H2B into the nucleus, assembles nucleosomes and promotes chromatin fluidity, thereby affecting transcription of several cellular genes. Results Using a proteomic screening, we identified hNAP-1 as a novel cellular protein interacting with HIV-1 Tat. We observed that Tat specifically binds hNAP1, but not other members of the same family of factors. Binding between the two proteins required the integrity of the basic domain of Tat and of two separable domains of hNAP-1 (aa 162–290 and 290–391). Overexpression of hNAP-1 significantly enhanced Tat-mediated activation of the LTR. Conversely, silencing of the protein decreased viral promoter activity. To explore the effects of hNAP-1 on viral infection, a reporter HIV-1 virus was used to infect cells in which hNAP-1 had been either overexpressed or knocked-down. Consistent with the gene expression results, these two treatments were found to increase and inhibit viral infection, respectively. Finally, we also observed that the overexpression of p300, a known co-activator of both Tat and hNAP-1, enhanced hNAP-1-mediated transcriptional activation as well as its interaction with Tat. Conclusion Our study reveals that HIV-1 Tat binds the histone chaperone hNAP-1 both in vitro and in vivo and shows that this interaction participates in the regulation of Tat-mediated activation of viral gene expression.
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Affiliation(s)
- Chiara Vardabasso
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34012 Trieste, Italy.
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