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Wu Y, Sun A, Yang Q, Wang M, Tian B, Yang Q, Jia R, Chen S, Ou X, Huang J, Sun D, Zhu D, Liu M, Zhang S, Zhao XX, He Y, Wu Z, Cheng A. An alpha-herpesvirus employs host HEXIM1 to promote viral transcription. J Virol 2024; 98:e0139223. [PMID: 38363111 PMCID: PMC10949456 DOI: 10.1128/jvi.01392-23] [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: 11/07/2023] [Accepted: 01/29/2024] [Indexed: 02/17/2024] Open
Abstract
Although it is widely accepted that herpesviruses utilize host RNA polymerase II (RNAPII) to transcribe viral genes, the mechanism of utilization varies significantly among herpesviruses. With the exception of herpes simplex virus 1 (HSV-1) in alpha-herpesviruses, the mechanism by which RNAPII transcribes viral genes in the remaining alpha-herpesviruses has not been reported. In this study, we investigated the transcriptional mechanism of an avian alpha-herpesvirus, Anatid herpesvirus 1 (AnHV-1). We discovered for the first time that hexamethylene-bis-acetamide-inducing protein 1 (HEXIM1), a major inhibitor of positive elongation factor B (P-TEFb), was significantly upregulated during AnHV-1 infection, and its expression was dynamically regulated throughout the progression of the disease. However, the expression level of HEXIM1 remained stable before and after HSV-1 infection. Excessive HEXIM1 assists AnHV-1 in progeny virus production, gene expression, and RNA polymerase II recruitment by promoting the formation of more inactive P-TEFb and the loss of RNAPII S2 phosphorylation. Conversely, the expression of some host survival-related genes, such as SOX8, CDK1, MYC, and ID2, was suppressed by HEXIM1 overexpression. Further investigation revealed that the C-terminus of the AnHV-1 US1 gene is responsible for the upregulation of HEXIM1 by activating its promoter but not by interacting with P-TEFb, which is the mechanism adopted by its homologs, HSV-1 ICP22. Additionally, the virus proliferation deficiency caused by US1 deletion during the early infection stage could be partially rescued by HEXIM1 overexpression, suggesting that HEXIM1 is responsible for AnHV-1 gaining transcription advantages when competing with cells. Taken together, this study revealed a novel HEXIM1-dependent AnHV-1 transcription mechanism, which has not been previously reported in herpesvirus or even DNA virus studies.IMPORTANCEHexamethylene-bis-acetamide-inducing protein 1 (HEXIM1) has been identified as an inhibitor of positive transcriptional elongation factor b associated with cancer, AIDS, myocardial hypertrophy, and inflammation. Surprisingly, no previous reports have explored the role of HEXIM1 in herpesvirus transcription. This study reveals a mechanism distinct from the currently known herpesvirus utilization of RNA polymerase II, highlighting the dependence on high HEXIM1 expression, which may be a previously unrecognized facet of the host shutoff manifested by many DNA viruses. Moreover, this discovery expands the significance of HEXIM1 in pathogen infection. It raises intriguing questions about whether other herpesviruses employ similar mechanisms to manipulate HEXIM1 and if this molecular target can be exploited to limit productive replication. Thus, this discovery not only contributes to our understanding of herpesvirus infection regulation but also holds implications for broader research on other herpesviruses, even DNA viruses.
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Affiliation(s)
- Ying Wu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Anyang Sun
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Qiqi Yang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Mingshu Wang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Bin Tian
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Qiao Yang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Renyong Jia
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Shun Chen
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Xumin Ou
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Juan Huang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Di Sun
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Dekang Zhu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Mafeng Liu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Shaqiu Zhang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Xin-Xin Zhao
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Yu He
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Zhen Wu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
| | - Anchun Cheng
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People’s Republic of China, Chengdu, China
- Science & Technology Department of Sichuan Province, International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Wenjiang, China
- Avian Disease Research Center, College of Veterinary Medicine of Sichuan Agricultural University, Wenjiang, China
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2
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Yan Y, Tang YD, Zheng C. When cyclin-dependent kinases meet viral infections, including SARS-CoV-2. J Med Virol 2022; 94:2962-2968. [PMID: 35288942 PMCID: PMC9088476 DOI: 10.1002/jmv.27719] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 02/18/2022] [Accepted: 02/25/2022] [Indexed: 11/16/2022]
Abstract
Cyclin‐dependent kinases (CDKs) are protein kinases that play a key role in cell division and transcriptional regulation. Recent studies have demonstrated the critical roles of CDKs in various viral infections. However, the molecular processes underpinning CDKs' roles in viral infection and host antiviral defense are unknown. This minireview briefly overviews CDKs' functions and highlights the most recent discoveries of CDKs' emerging roles during viral infections, thereby providing a scientific and theoretical foundation for antiviral regulation and shedding light on developing novel drug targets and therapeutic strategies against viral infection.
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Affiliation(s)
- Yan Yan
- Center of Clinical Laboratory, The Fifth People's Hospital of Wuxi, Affiliated Hospital of Jiangnan University, Wuxi, China
| | - Yan-Dong Tang
- Department of Immunology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.,State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin, China
| | - Chunfu Zheng
- Department of Immunology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.,Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada
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3
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Boyd PS, Brown JB, Brown JD, Catazaro J, Chaudry I, Ding P, Dong X, Marchant J, O’Hern CT, Singh K, Swanson C, Summers MF, Yasin S. NMR Studies of Retroviral Genome Packaging. Viruses 2020; 12:v12101115. [PMID: 33008123 PMCID: PMC7599994 DOI: 10.3390/v12101115] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/18/2020] [Accepted: 09/26/2020] [Indexed: 12/03/2022] Open
Abstract
Nearly all retroviruses selectively package two copies of their unspliced RNA genomes from a cellular milieu that contains a substantial excess of non-viral and spliced viral RNAs. Over the past four decades, combinations of genetic experiments, phylogenetic analyses, nucleotide accessibility mapping, in silico RNA structure predictions, and biophysical experiments were employed to understand how retroviral genomes are selected for packaging. Genetic studies provided early clues regarding the protein and RNA elements required for packaging, and nucleotide accessibility mapping experiments provided insights into the secondary structures of functionally important elements in the genome. Three-dimensional structural determinants of packaging were primarily derived by nuclear magnetic resonance (NMR) spectroscopy. A key advantage of NMR, relative to other methods for determining biomolecular structure (such as X-ray crystallography), is that it is well suited for studies of conformationally dynamic and heterogeneous systems—a hallmark of the retrovirus packaging machinery. Here, we review advances in understanding of the structures, dynamics, and interactions of the proteins and RNA elements involved in retroviral genome selection and packaging that are facilitated by NMR.
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4
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Telwatte S, Morón-López S, Aran D, Kim P, Hsieh C, Joshi S, Montano M, Greene WC, Butte AJ, Wong JK, Yukl SA. Heterogeneity in HIV and cellular transcription profiles in cell line models of latent and productive infection: implications for HIV latency. Retrovirology 2019; 16:32. [PMID: 31711503 PMCID: PMC6849327 DOI: 10.1186/s12977-019-0494-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 11/04/2019] [Indexed: 12/14/2022] Open
Abstract
Background HIV-infected cell lines are widely used to study latent HIV infection, which is considered the main barrier to HIV cure. We hypothesized that these cell lines differ from each other and from cells from HIV-infected individuals in the mechanisms underlying latency. Results To quantify the degree to which HIV expression is inhibited by blocks at different stages of HIV transcription, we employed a recently-described panel of RT-ddPCR assays to measure levels of 7 HIV transcripts (“read-through,” initiated, 5′ elongated, mid-transcribed/unspliced [Pol], distal-transcribed [Nef], polyadenylated, and multiply-sliced [Tat-Rev]) in bulk populations of latently-infected (U1, ACH-2, J-Lat) and productively-infected (8E5, activated J-Lat) cell lines. To assess single-cell variation and investigate cellular genes associated with HIV transcriptional blocks, we developed a novel multiplex qPCR panel and quantified single cell levels of 7 HIV targets and 89 cellular transcripts in latently- and productively-infected cell lines. The bulk cell HIV transcription profile differed dramatically between cell lines and cells from ART-suppressed individuals. Compared to cells from ART-suppressed individuals, latent cell lines showed lower levels of HIV transcriptional initiation and higher levels of polyadenylation and splicing. ACH-2 and J-Lat cells showed different forms of transcriptional interference, while U1 cells showed a block to elongation. Single-cell studies revealed marked variation between/within cell lines in expression of HIV transcripts, T cell phenotypic markers, antiviral factors, and genes implicated in latency. Expression of multiply-spliced HIV Tat-Rev was associated with expression of cellular genes involved in activation, tissue retention, T cell transcription, and apoptosis/survival. Conclusions HIV-infected cell lines differ from each other and from cells from ART-treated individuals in the mechanisms governing latent HIV infection. These differences in viral and cellular gene expression must be considered when gauging the suitability of a given cell line for future research on HIV. At the same time, some features were shared across cell lines, such as low expression of antiviral defense genes and a relationship between productive infection and genes involved in survival. These features may contribute to HIV latency or persistence in vivo, and deserve further study using novel single cell assays such as those described in this manuscript.
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Affiliation(s)
- Sushama Telwatte
- San Francisco VA Medical Center, San Francisco, CA, USA.,University of California San Francisco, San Francisco, CA, USA
| | - Sara Morón-López
- San Francisco VA Medical Center, San Francisco, CA, USA.,University of California San Francisco, San Francisco, CA, USA
| | - Dvir Aran
- Bakar Computational Health Sciences Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Peggy Kim
- San Francisco VA Medical Center, San Francisco, CA, USA
| | - Christine Hsieh
- San Francisco VA Medical Center, San Francisco, CA, USA.,University of California San Francisco, San Francisco, CA, USA
| | - Sunil Joshi
- San Francisco VA Medical Center, San Francisco, CA, USA.,University of California San Francisco, San Francisco, CA, USA
| | - Mauricio Montano
- University of California San Francisco, San Francisco, CA, USA.,Gladstone Institute of Virology and Immunology, San Francisco, CA, USA
| | - Warner C Greene
- University of California San Francisco, San Francisco, CA, USA.,Gladstone Institute of Virology and Immunology, San Francisco, CA, USA
| | - Atul J Butte
- Bakar Computational Health Sciences Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Joseph K Wong
- San Francisco VA Medical Center, San Francisco, CA, USA.,University of California San Francisco, San Francisco, CA, USA
| | - Steven A Yukl
- San Francisco VA Medical Center, San Francisco, CA, USA. .,University of California San Francisco, San Francisco, CA, USA.
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5
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Andrews RJ, Roche J, Moss WN. ScanFold: an approach for genome-wide discovery of local RNA structural elements-applications to Zika virus and HIV. PeerJ 2018; 6:e6136. [PMID: 30627482 PMCID: PMC6317755 DOI: 10.7717/peerj.6136] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 11/15/2018] [Indexed: 12/24/2022] Open
Abstract
In addition to encoding RNA primary structures, genomes also encode RNA secondary and tertiary structures that play roles in gene regulation and, in the case of RNA viruses, genome replication. Methods for the identification of functional RNA structures in genomes typically rely on scanning analysis windows, where multiple partially-overlapping windows are used to predict RNA structures and folding metrics to deduce regions likely to form functional structure. Separate structural models are produced for each window, where the step size can greatly affect the returned model. This makes deducing unique local structures challenging, as the same nucleotides in each window can be alternatively base paired. We are presenting here a new approach where all base pairs from analysis windows are considered and weighted by favorable folding. This results in unique base pairing throughout the genome and the generation of local regions/structures that can be ranked by their propensity to form unusually thermodynamically stable folds. We applied this approach to the Zika virus (ZIKV) and HIV-1 genomes. ZIKV is linked to a variety of neurological ailments including microcephaly and Guillain-Barré syndrome and its (+)-sense RNA genome encodes two, previously described, functionally essential structured RNA regions. HIV, the cause of AIDS, contains multiple functional RNA motifs in its genome, which have been extensively studied. Our approach is able to successfully identify and model the structures of known functional motifs in both viruses, while also finding additional regions likely to form functional structures. All data have been archived at the RNAStructuromeDB (www.structurome.bb.iastate.edu), a repository of RNA folding data for humans and their pathogens.
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Affiliation(s)
- Ryan J. Andrews
- Roy J. Carver Department of Biophysics, Biochemistry and Molecular Biology, Iowa State University, Ames, IA, USA
| | - Julien Roche
- Roy J. Carver Department of Biophysics, Biochemistry and Molecular Biology, Iowa State University, Ames, IA, USA
| | - Walter N. Moss
- Roy J. Carver Department of Biophysics, Biochemistry and Molecular Biology, Iowa State University, Ames, IA, USA
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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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7
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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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8
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Thomas T, Seay K, Zheng JH, Zhang C, Ochsenbauer C, Kappes JC, Goldstein H. High-Throughput Humanized Mouse Models for Evaluation of HIV-1 Therapeutics and Pathogenesis. Methods Mol Biol 2016; 1354:221-35. [PMID: 26714715 DOI: 10.1007/978-1-4939-3046-3_15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mice cannot be used as a model to evaluate HIV-1 therapeutics because they do not become infected by HIV-1 due to structural differences between several human and mouse proteins required for HIV-1 replication. This has limited their use for in vivo assessment of anti-HIV-1 therapeutics and the mechanism by which cofactors, such as illicit drug use accelerate HIV-1 replication and disease course in substance abusers. Here, we describe the development and application of two in vivo humanized mouse models that are highly sensitive and useful models for the in vivo evaluation of candidate anti-HIV therapeutics. The first model, hu-spl-PBMC-NSG mice, uses NOD-SCID IL2rγ(-/-) (NSG) mice intrasplenically injected with human peripheral blood mononuclear cells (PBMC) which develop productive splenic HIV-1 infection after intrasplenic inoculation with a replication-competent HIV-1 expressing Renilla reniformis luciferase (HIV-LucR) and enables investigators to use bioluminescence to visualize and quantitate the temporal effects of therapeutics on HIV-1 infection. The second model, hCD4/R5/cT1 mice, consists of transgenic mice carrying human CD4, CCR5 and cyclin T1 genes, which enables murine CD4-expressing cells to support HIV-1 entry, Tat-mediated LTR transcription and consequently develop productive infection. The hCD4/R5/cT1 mice develop disseminated infection of tissues including the spleen, small intestine, lymph nodes and lungs after intravenous injection with HIV-1-LucR. Because these mice can be infected with HIV-LucR expressing transmitted/founder and clade A/E and C Envs, these mouse models can also be used to evaluate the in vivo efficacy of broadly neutralizing antibodies and antibodies induced by candidate HIV-1 vaccines. Furthermore, because hCD4/R5/cT1 mice can be infected by vaginal inoculation with replication-competent HIV-1 expressing NanoLuc (HIV-nLucR)-, this mouse model can be used to evaluate the mechanisms by which substance abuse and other factors enhance mucosal transmission of HIV-1.
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Affiliation(s)
- Tynisha Thomas
- Departments of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Kieran Seay
- Departments of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Jian Hua Zheng
- Departments of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Cong Zhang
- Departments of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Christina Ochsenbauer
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - John C Kappes
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.,Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, AL, 35294, USA
| | - Harris Goldstein
- Departments of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA. .,Departments of Pediatrics, Albert Einstein College of Medicine, Forchheimer Building, Room 408, 1300 Morris Park Avenue, Bronx, NY, 10461, USA.
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9
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The Vaginal Acquisition and Dissemination of HIV-1 Infection in a Novel Transgenic Mouse Model Is Facilitated by Coinfection with Herpes Simplex Virus 2 and Is Inhibited by Microbicide Treatment. J Virol 2015; 89:9559-70. [PMID: 26157126 DOI: 10.1128/jvi.01326-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/02/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Epidemiological studies have demonstrated that herpes simplex virus 2 (HSV-2) infection significantly increases the risk of HIV-1 acquisition, thereby contributing to the expanding HIV-1 epidemic. To investigate whether HSV-2 infection directly facilitates mucosal HIV-1 acquisition, we used our transgenic hCD4/R5/cT1 mouse model which circumvents major entry and transcription blocks preventing murine HIV-1 infection by targeting transgenic expression of human CD4, CCR5, and cyclin T1 genes to CD4(+) T cells and myeloid-committed cells. Productive infection of mucosal leukocytes, predominantly CD4(+) T cells, was detected in all hCD4/R5/cT1 mice intravaginally challenged with an HIV-1 infectious molecular clone, HIV-Du151.2env-NLuc, which expresses an env gene (C.Du151.2) cloned from an acute heterosexually infected woman and a NanoLuc luciferase reporter gene. Lower genital tract HIV-1 infection after HIV-Du151.2env-NLuc intravaginal challenge was increased ~4-fold in hCD4/R5/cT1 mice coinfected with HSV-2. Furthermore, HIV-1 dissemination to draining lymph nodes was detected only in HSV-2-coinfected mice. HSV-2 infection stimulated local infiltration and activation of CD4(+) T cells and dendritic cells, likely contributing to the enhanced HIV-1 infection and dissemination in HSV-2-coinfected mice. We then used this model to demonstrate that a novel gel containing tenofovir disoproxil fumarate (TDF), the more potent prodrug of tenofovir (TFV), but not the TFV microbicide gel utilized in the recent CAPRISA 004, VOICE (Vaginal and Oral Interventions to Control the Epidemic), and FACTS 001 clinical trials, was effective as preexposure prophylaxis (PrEP) to completely prevent vaginal HIV-1 infection in almost half of HSV-2-coinfected mice. These results also support utilization of hCD4/R5/cT1 mice as a highly reproducible immunocompetent preclinical model to evaluate HIV-1 acquisition across the female genital tract. IMPORTANCE Multiple epidemiological studies have reported that genital herpes simplex virus 2 (HSV-2) infection increases the risk of HIV-1 sexual acquisition by severalfold. Understanding the underlying mechanisms by which HSV-2 facilitates HIV-1 infection and optimizing the efficacy of therapies to inhibit HIV-1 infection during HSV-2 coinfection should contribute to reducing HIV-1 transmission. Using our novel transgenic hCD4/R5/cT1 mouse model infectible with HIV-1, we demonstrated that HSV-2 infection enhances vaginal transmission and dissemination of HIV-1 infection while stimulating recruitment and activation of CD4(+) T cells and dendritic cells in the lower genital tract. HIV acquisition by hCD4/R5/cT1 mice vaginally coinfected with HSV-2 could be completely prevented in almost half the mice by preexposure prophylaxis (PrEP) with a novel gel containing tenofovir disoproxil fumarate (TDF), the tenofovir prodrug, but not with the tenofovir microbicide gel utilized in CAPRISA-004, VOICE, and FACTS-001 clinical trials. The hCD4/R5/cT1 mice represent a new preclinical mouse model to evaluate vaginal HIV-1 acquisition.
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In silico design of small molecule inhibitors of CDK9/cyclin T1 interaction. J Mol Graph Model 2014; 50:100-12. [PMID: 24769691 DOI: 10.1016/j.jmgm.2014.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 04/02/2014] [Accepted: 04/03/2014] [Indexed: 11/23/2022]
Abstract
In order to design a small molecule which potentially may interfere with CDK9/cyclin T1 complex formation and therefore influence its physiological role, a computational study of dynamics and druggability of CDK9 binding surface was conducted. Druggability estimates and pocket opening analyses indicated binding regions of cyclin T1 residues, Phe 146 and Lys 6, as starting points for the design of small molecules with the potential to inhibit the CDK9/cyclin T1 association. A pharmacophore model was created, based on these two residues and used to select potential inhibitor structures. Binding energies of the inhibitors were estimated with MM-GBSA. A good correlation of MM-GBSA energies and FTMap druggability predictions was observed. Amongst studied compounds a derivative of 2-amino-8-hydroxyquinoline was identified as the best potential candidate to inhibit CDK9/cyclin T1 interactions.
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Kuzembayeva M, Dilley K, Sardo L, Hu WS. Life of psi: how full-length HIV-1 RNAs become packaged genomes in the viral particles. Virology 2014; 454-455:362-70. [PMID: 24530126 DOI: 10.1016/j.virol.2014.01.019] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 01/03/2014] [Accepted: 01/24/2014] [Indexed: 12/27/2022]
Abstract
As a member of the retrovirus family, HIV-1 packages its RNA genome into particles and replicates through a DNA intermediate that integrates into the host cellular genome. The multiple genes encoded by HIV-1 are expressed from the same promoter and their expression is regulated by splicing and ribosomal frameshift. The full-length HIV-1 RNA plays a central role in viral replication as it serves as the genome in the progeny virus and is used as the template for Gag and GagPol translation. In this review, we summarize findings that contribute to our current understanding of how full-length RNA is expressed and transported, cis- and trans-acting elements important for RNA packaging, the locations and timing of RNA:RNA and RNA:Gag interactions, and the processes required for this RNA to be packaged into viral particles.
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Affiliation(s)
- Malika Kuzembayeva
- Viral Recombination Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA
| | - Kari Dilley
- Viral Recombination Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA
| | - Luca Sardo
- Viral Recombination Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA
| | - Wei-Shau Hu
- Viral Recombination Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA.
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Brd4 and HEXIM1: multiple roles in P-TEFb regulation and cancer. BIOMED RESEARCH INTERNATIONAL 2014; 2014:232870. [PMID: 24592384 PMCID: PMC3925632 DOI: 10.1155/2014/232870] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 12/19/2013] [Indexed: 12/31/2022]
Abstract
Bromodomain-containing protein 4 (Brd4) and hexamethylene bisacetamide (HMBA) inducible protein 1 (HEXIM1) are two opposing regulators of the positive transcription elongation factor b (P-TEFb), which is the master modulator of RNA polymerase II during transcriptional elongation. While Brd4 recruits P-TEFb to promoter-proximal chromatins to activate transcription, HEXIM1 sequesters P-TEFb into an inactive complex containing the 7SK small nuclear RNA. Besides regulating P-TEFb's transcriptional activity, recent evidence demonstrates that both Brd4 and HEXIM1 also play novel roles in cell cycle progression and tumorigenesis. Here we will discuss the current knowledge on Brd4 and HEXIM1 and their implication as novel therapeutic options against cancer.
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Lew QJ, Chu KL, Chia YL, Cheong N, Chao SH. HEXIM1, a New Player in the p53 Pathway. Cancers (Basel) 2013; 5:838-56. [PMID: 24202322 PMCID: PMC3795367 DOI: 10.3390/cancers5030838] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 06/24/2013] [Accepted: 06/24/2013] [Indexed: 01/10/2023] Open
Abstract
Hexamethylene bisacetamide-inducible protein 1 (HEXIM1) is best known as the inhibitor of positive transcription elongation factor b (P-TEFb), which controls transcription elongation of RNA polymerase II and Tat transactivation of human immunodeficiency virus. Besides P-TEFb, several proteins have been identified as HEXIM1 binding proteins. It is noteworthy that more than half of the HEXIM1 binding partners are involved in cancers. P53 and two key regulators of the p53 pathway, nucleophosmin (NPM) and human double minute-2 protein (HDM2), are among the factors identified. This review will focus on the functional importance of the interactions between HEXIM1 and p53/NPM/HDM2. NPM and the cytoplasmic mutant of NPM, NPMc+, were found to regulate P-TEFb activity and RNA polymerase II transcription through the interaction with HEXIM1. Importantly, more than one-third of acute myeloid leukemia (AML) patients carry NPMc+, suggesting the involvement of HEXIM1 in tumorigenesis of AML. HDM2 was found to ubiquitinate HEXIM1. The HDM2-mediated ubiquitination of HEXIM1 did not lead to protein degradation of HEXIM1 but enhanced its inhibitory activity on P-TEFb. Recently, HEXIM1 was identified as a novel positive regulator of p53. HEXIM1 prevented p53 ubiquitination by competing with HDM2 in binding to p53. Taken together, the new evidence suggests a role of HEXIM1 in regulating the p53 pathway and tumorigenesis.
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Affiliation(s)
- Qiao Jing Lew
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way, #06-01, Singapore 138668, Singapore.
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Seay K, Qi X, Zheng JH, Zhang C, Chen K, Dutta M, Deneroff K, Ochsenbauer C, Kappes JC, Littman DR, Goldstein H. Mice transgenic for CD4-specific human CD4, CCR5 and cyclin T1 expression: a new model for investigating HIV-1 transmission and treatment efficacy. PLoS One 2013; 8:e63537. [PMID: 23691059 PMCID: PMC3655194 DOI: 10.1371/journal.pone.0063537] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 04/03/2013] [Indexed: 12/16/2022] Open
Abstract
Mice cannot be used to evaluate HIV-1 therapeutics and vaccines because they are not infectible by HIV-1 due to structural differences between several human and mouse proteins required for HIV-1 entry and replication including CD4, CCR5 and cyclin T1. We overcame this limitation by constructing mice with CD4 enhancer/promoter-regulated human CD4, CCR5 and cyclin T1 genes integrated as tightly linked transgenes (hCD4/R5/cT1 mice) promoting their efficient co-transmission and enabling the murine CD4-expressing cells to support HIV-1 entry and Tat-mediated LTR transcription. All of the hCD4/R5/cT1 mice developed disseminated infection of tissues that included the spleen, small intestine, lymph nodes and lungs after intravenous injection with an HIV-1 infectious molecular clone (HIV-IMC) expressing Renilla reniformis luciferase (LucR). Furthermore, localized infection of cervical-vaginal mucosal leukocytes developed after intravaginal inoculation of hCD4/R5/cT1 mice with the LucR-expressing HIV-IMC. hCD4/R5/cT1 mice reproducibly developed in vivo infection after inoculation with LucR-expressing HIV-IMC which could be bioluminescently quantified and visualized with a high sensitivity and specificity which enabled them to be used to evaluate the efficacy of HIV-1 therapeutics. Treatment with highly active anti-retroviral therapy or one dose of VRC01, a broadly neutralizing anti-HIV-1 antibody, almost completed inhibited acute systemic HIV-1 infection of the hCD4/R5/cT1 mice. hCD4/R5/cT1 mice could also be used to evaluate the capacity of therapies delivered by gene therapy to inhibit in vivo HIV infection. VRC01 secreted in vivo by primary B cells transduced with a VRC01-encoding lentivirus transplanted into hCD4/R5/cT1 mice markedly inhibited infection after intravenous challenge with LucR-expressing HIV-IMC. The reproducible infection of CD4/R5/cT1 mice with LucR-expressing HIV-IMC after intravenous or mucosal inoculation combined with the availability of LucR-expressing HIV-IMC expressing transmitted/founder and clade A/E and C Envs will provide researchers with a highly accessible pre-clinical in vivo HIV-1-infection model to study HIV-1 acquisition, treatment, and prevention.
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Affiliation(s)
- Kieran Seay
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Xiaohua Qi
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Jian Hua Zheng
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Cong Zhang
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Ken Chen
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Monica Dutta
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Kathryn Deneroff
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Christina Ochsenbauer
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - John C. Kappes
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Birmingham Veterans Affairs Medical Center, Research Service, Birmingham, Alabama, United States of America
| | - Dan R. Littman
- Molecular Pathogenesis Program, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, New York, United States of America
- Howard Hughes Medical Institute, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, New York, United States of America
| | - Harris Goldstein
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Gao G, Wu X, Zhou J, He M, He JJ, Guo D. Inhibition of HIV-1 transcription and replication by a newly identified cyclin T1 splice variant. J Biol Chem 2013; 288:14297-14309. [PMID: 23569210 DOI: 10.1074/jbc.m112.438465] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A variety of cellular factors participates in the HIV-1 life cycle. Among them is the well characterized cyclin T1 (CYCT1). CycT1 binds to cyclin-dependent kinase 9 (CDK9) and forms the positive transcription elongation factor-b (P-TEFb). P-TEFb is then recruited by HIV-1 TAT to the HIV-1 long terminal repeat (LTR) promoter and subsequently leads to phosphorylation of the C-terminal domain of RNA polymerase II (pol II), enhanced processivity of pol II, and transcription of a full-length HIV-1 RNA. In this study, we report the identification of a new CYCT1 splice variant, designated as CYCT1b, and accordingly we renamed CYCT1 as CYCT1a. CYCT1b was detected in several cell lines, including primary human CD4 T cells, and its expression was subject to cell cycle regulation. Similar to CYCT1a, CYCT1b was primarily localized in the nucleus. CYCT1b expression was found to be inversely correlated with HIV-1 gene expression and replication. This inverse correlation appeared to involve TAT transactivation, CDK9 binding, and subsequent recruitment of P-TEFb to the HIV-1 LTR promoter and pol II C-terminal domain phosphorylation. In agreement with these findings, CYCT1b expression led to direct inhibition of TAT-transactivated transcription of the HIV-1 LTR promoter. Taken together, these results show that the newly identified CYCT1b splice variant inhibits HIV-1 transcription and may provide new clues for the development of anti-HIV strategies.
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Affiliation(s)
- Guozhen Gao
- State Key Laboratory of Virology and Modern Virology Research Center, Wuhan University College of Life Sciences, 430072 Wuhan, China; Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Xiaoyun Wu
- State Key Laboratory of Virology and Modern Virology Research Center, Wuhan University College of Life Sciences, 430072 Wuhan, China
| | - Jieqiong Zhou
- State Key Laboratory of Virology and Modern Virology Research Center, Wuhan University College of Life Sciences, 430072 Wuhan, China
| | - Mingfeng He
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Johnny J He
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Center for AIDS Research, Indiana University School of Medicine, Indianapolis, Indiana 46202; University of North Texas Health Science Center, Fort Worth, Texas 76107.
| | - Deyin Guo
- State Key Laboratory of Virology and Modern Virology Research Center, Wuhan University College of Life Sciences, 430072 Wuhan, China; Institute of Medical Virology, Wuhan University School of Medicine, 430071 Wuhan, China.
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Guo HY, Ma YG, Gai YM, Liang ZB, Ma J, Su Y, Zhang QC, Chen QM, Tan J. Bovine HEXIM1 inhibits bovine immunodeficiency virus replication through regulating BTat-mediated transactivation. Vet Res 2013; 44:21. [PMID: 23537346 PMCID: PMC3630055 DOI: 10.1186/1297-9716-44-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 03/05/2013] [Indexed: 11/11/2022] Open
Abstract
The bovine immunodeficiency virus (BIV) transactivator (BTat) recruits the bovine cyclin T1 (B-cyclin T1) to the LTR to facilitate the transcription of BIV. Here, we demonstrate that bovine hexamethylene bisacetamide (HMBA)-induced protein 1 (BHEXIM1) inhibits BTat-mediated BIV LTR transcription. The results of in vivo and in vitro assays show direct binding of BHEXIM1 to the B-cyclin T1. These results suggest that the repression arises from BHEXIM1-BTat competition for B-cyclin T1, which allows BHEXIM1 to displace BTat from B-cyclin T1. Furthermore, we found that the C-terminal region and the centrally located region of BHEXIM1 are required for BHEXIM1 to associate with B-cyclin T1. Knockdown of BHEXIM1 enhances BIV replication. Taken together, our study provides the first clear evidence that BHEXIM1 is involved in BIV replication through regulating BTat-mediated transactivation.
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Affiliation(s)
- Hong-yan Guo
- Key Laboratory of Molecular Microbiology and Biotechnology (Ministry of Education) and Key Laboratory Microbial Functional Genomics (Tianjin), College of Life Sciences, Nankai University, Tianjin, 300071, China.
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Lin MH, Sivakumaran H, Apolloni A, Wei T, Jans DA, Harrich D. Nullbasic, a potent anti-HIV tat mutant, induces CRM1-dependent disruption of HIV rev trafficking. PLoS One 2012; 7:e51466. [PMID: 23251541 PMCID: PMC3519632 DOI: 10.1371/journal.pone.0051466] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 11/02/2012] [Indexed: 12/30/2022] Open
Abstract
Nullbasic, a mutant of the HIV-1 Tat protein, has anti-HIV-1 activity through mechanisms that include inhibition of Rev function and redistribution of the HIV-1 Rev protein from the nucleolus to the nucleoplasm and cytoplasm. Here we investigate the mechanism of this effect for the first time, establishing that redistribution of Rev by Nullbasic is not due to direct interaction between the two proteins. Rather, Nullbasic affects subcellular localization of cellular proteins that regulate Rev trafficking. In particular, Nullbasic induced redistribution of exportin 1 (CRM1), nucleophosmin (B23) and nucleolin (C23) from the nucleolus to the nucleus when Rev was coexpressed, but never in its absence. Inhibition of the Rev:CRM1 interaction by leptomycin B or a non-interacting RevM10 mutant completely blocked redistribution of Rev by Nullbasic. Finally, Nullbasic did not inhibit importin β- or transportin 1-mediated nuclear import, suggesting that cytoplasmic accumulation of Rev was due to increased export by CRM1. Overall, our data support the conclusion that CRM1-dependent subcellular redistribution of Rev from the nucleolus by Nullbasic is not through general perturbation of either nuclear import or export. Rather, Nullbasic appears to interact with and disrupt specific components of a Rev trafficking complex required for its nucleocytoplasmic shuttling and, in particular, its nucleolar accumulation.
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Affiliation(s)
- Min-Hsuan Lin
- Queensland Institute of Medical Research, Molecular Virology Laboratory, Herston, Brisbane, Australia
- School of Chemistry and Molecular Biosciences, University of Queensland, St. Lucia, Queensland, Australia
| | - Haran Sivakumaran
- Queensland Institute of Medical Research, Molecular Virology Laboratory, Herston, Brisbane, Australia
| | - Ann Apolloni
- Queensland Institute of Medical Research, Molecular Virology Laboratory, Herston, Brisbane, Australia
| | - Ting Wei
- Queensland Institute of Medical Research, Molecular Virology Laboratory, Herston, Brisbane, Australia
| | - David A. Jans
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - David Harrich
- Queensland Institute of Medical Research, Molecular Virology Laboratory, Herston, Brisbane, Australia
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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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Lu K, Heng X, Summers MF. Structural determinants and mechanism of HIV-1 genome packaging. J Mol Biol 2011; 410:609-33. [PMID: 21762803 DOI: 10.1016/j.jmb.2011.04.029] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/11/2011] [Accepted: 04/11/2011] [Indexed: 11/30/2022]
Abstract
Like all retroviruses, the human immunodeficiency virus selectively packages two copies of its unspliced RNA genome, both of which are utilized for strand-transfer-mediated recombination during reverse transcription-a process that enables rapid evolution under environmental and chemotherapeutic pressures. The viral RNA appears to be selected for packaging as a dimer, and there is evidence that dimerization and packaging are mechanistically coupled. Both processes are mediated by interactions between the nucleocapsid domains of a small number of assembling viral Gag polyproteins and RNA elements within the 5'-untranslated region of the genome. A number of secondary structures have been predicted for regions of the genome that are responsible for packaging, and high-resolution structures have been determined for a few small RNA fragments and protein-RNA complexes. However, major questions regarding the RNA structures (and potentially the structural changes) that are responsible for dimeric genome selection remain unanswered. Here, we review efforts that have been made to identify the molecular determinants and mechanism of human immunodeficiency virus type 1 genome packaging.
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Affiliation(s)
- Kun Lu
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD 21250, USA
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Functional characterization of a new member of the Cdk9 family in Aspergillus nidulans. EUKARYOTIC CELL 2010; 9:1901-12. [PMID: 20952582 DOI: 10.1128/ec.00384-09] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cdk9-like kinases in complex with T-type cyclins are essential components of the eukaryotic transcription elongation machinery. The full spectrum of Cdk9/cyclin T targets, as well as the specific consequences of phosphorylations, is still largely undefined. We identify and characterize here a Cdk9 kinase (PtkA) in the filamentous ascomycete Aspergillus nidulans. Deletion of ptkA had a lethal effect in later stages of vegetative growth and completely impeded asexual development. Overexpression of ptkA affected directionality of polarized growth and the initiation of new branching sites. A green fluorescent protein-tagged PtkA version localized inside the nucleus during interphase, supporting a role of PtkA in transcription elongation, as observed in other organisms. We also identified a putative cyclin T homolog, PchA, in the A. nidulans genome and confirmed its interaction with PtkA in vivo. Surprisingly, the Pcl-like cyclin PclA, previously described to be involved in asexual development, was also found to interact with PtkA, indicating a possible role of PtkA in linking transcriptional activity with development and/or morphogenesis in A. nidulans. This is the first report of a Cdk9 kinase interacting with a Pcl-like cyclin, revealing interesting new aspects about the involvement of this Cdk-subfamily in differential gene expression.
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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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Van Duyne R, Kehn-Hall K, Carpio L, Kashanchi F. Cell-type-specific proteome and interactome: using HIV-1 Tat as a test case. Expert Rev Proteomics 2010; 6:515-26. [PMID: 19811073 DOI: 10.1586/epr.09.73] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
HIV-1 is a small retrovirus that wreaks havoc on the human immune system. It is a puzzle to the scientific community how a virus that encodes only nine proteins can take complete control of its host and redirect the cell to complete replication or maintain latency when necessary. One way to explain the control elicited by HIV-1 is through numerous protein partners that exist between viral and host proteins, allowing HIV-1 to be intimately involved in virtually every aspect of cellular biology. In addition, we postulate that the complexity exerted by HIV-1 can not merely be explained by the large number of protein-protein interactions documented in the literature but, rather, cell-type-specific interactions and post-translational modifications of viral proteins must be taken into account. We use HIV-1 Tat and its influence on viral transcription as an example of cell-type-specific complexity. The influence of post-translational modifications (acetylation and methylation), as well as subcellular localization on Tat binding partners, is also discussed.
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Affiliation(s)
- Rachel Van Duyne
- The George Washington University, Department of Microbiology, Immunology and Tropical Medicine, 2300 I Street, NW, Washington, DC 20037, USA
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Abstract
Regulation of gene expression is essential to all aspects of physiological processes in single-cell as well as multicellular organisms. It gives ultimately cells the ability to efficiently respond to extra- and intracellular stimuli participating in cell cycle, growth, differentiation and survival. Regulation of gene expression is executed primarily at the level of transcription of specific mRNAs by RNA polymerase II (RNAPII), typically in several distinct phases. Among them, transcription elongation is positively regulated by the positive transcription elongation factor b (P-TEFb), consisting of CDK9 and cyclin T1, T2 or K. P-TEFb enables transition from abortive to productive transcription elongation by phosphorylating carboxyl-terminal domain (CTD) in RNAPII and negative transcription elongation factors. Over the years, we have learned a great deal about molecular composition of P-TEFb complexes, their assembly and their role in transcription of specific genes, but function of P-TEFb in other physiological processes was not apparent until just recently. In light of emerging discoveries connecting P-TEFb to regulation of cell cycle, development and several diseases, I would like to discuss these observations as well as future perspectives.
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Affiliation(s)
- Jiri Kohoutek
- Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic.
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24
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Guendel I, Carpio L, Easley R, Van Duyne R, Coley W, Agbottah E, Dowd C, Kashanchi F, Kehn-Hall K. 9-Aminoacridine inhibition of HIV-1 Tat dependent transcription. Virol J 2009; 6:114. [PMID: 19630958 PMCID: PMC2723079 DOI: 10.1186/1743-422x-6-114] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 07/24/2009] [Indexed: 11/30/2022] Open
Abstract
As part of a continued search for more efficient anti-HIV-1 drugs, we are focusing on the possibility that small molecules could efficiently inhibit HIV-1 replication through the restoration of p53 and p21WAF1 functions, which are inactivated by HIV-1 infection. Here we describe the molecular mechanism of 9-aminoacridine (9AA) mediated HIV-1 inhibition. 9AA treatment resulted in inhibition of HIV LTR transcription in a specific manner that was highly dependent on the presence and location of the amino moiety. Importantly, virus replication was found to be inhibited in HIV-1 infected cell lines by 9AA in a dose-dependent manner without inhibiting cellular proliferation or inducing cell death. 9AA inhibited viral replication in both p53 wildtype and p53 mutant cells, indicating that there is another p53 independent factor that was critical for HIV inhibition. p21WAF1 is an ideal candidate as p21WAF1 levels were increased in both p53 wildtype and p53 mutant cells, and p21WAF1 was found to be phosphorylated at S146, an event previously shown to increase its stability. Furthermore, we observed p21WAF1 in complex with cyclin T1 and cdk9 in vitro, suggesting a direct role of p21WAF1 in HIV transcription inhibition. Finally, 9AA treatment resulted in loss of cdk9 from the viral promoter, providing one possible mechanism of transcriptional inhibition. Thus, 9AA treatment was highly efficient at reactivating the p53 – p21WAF1 pathway and consequently inhibiting HIV replication and transcription.
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Affiliation(s)
- Irene Guendel
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University, Washington, DC 20037,
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25
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Abstract
The positive transcription elongation factor b (P-TEFb) is essential for the elongation of transcription and cotranscriptional processing by RNA polymerase II. In mammals, it contains predominantly the C-type cyclin cyclin T1 (CycT1) or CycT2 and cyclin-dependent kinase 9 (Cdk9). To determine if these cyclins have redundant functions or affect distinct sets of genes, we genetically inactivated the CycT2 gene (Ccnt2) using the beta-galactosidase-neomycin gene (beta-geo) gene trap technology in the mouse. Visualizing beta-galactosidase during mouse embryogenesis revealed that CycT2 is expressed abundantly during embryogenesis and throughout the organism in the adult. This finding was reflected in the expression of CycT2 in all adult tissues and organs. However, despite numerous matings of heterozygous mice, we observed no CycT2(-/-) embryos, pups, or adult mice. This early lethality could have resulted from decreased expression of critical genes, which were revealed by short interfering RNAs against CycT2 in embryonic stem cells. Thus, CycT1 and CycT2 are not redundant, and these different P-TEFb complexes regulate subsets of distinct genes that are important for embryonic development.
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26
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Michels AA, Bensaude O. RNA-driven cyclin-dependent kinase regulation: When CDK9/cyclin T subunits of P-TEFb meet their ribonucleoprotein partners. Biotechnol J 2008; 3:1022-32. [DOI: 10.1002/biot.200800104] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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27
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Hou T, Ray S, Brasier AR. The functional role of an interleukin 6-inducible CDK9.STAT3 complex in human gamma-fibrinogen gene expression. J Biol Chem 2007; 282:37091-102. [PMID: 17956865 DOI: 10.1074/jbc.m706458200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signal transducer and activator of transcription 3 (STAT3) is an IL-6-inducible transcription factor that mediates the hepatic acute phase response (APR). Using gamma-fibrinogen (FBG) as a model of the APR, we investigated the requirement of an IL-6-inducible complex of STAT3 with cyclin-dependent kinase 9 (CDK9) on gamma-FBG expression in HepG2 hepatocarcinoma cells. IL-6 induces rapid nuclear translocation of Tyr-phosphorylated STAT3 that forms a nuclear complex with CDK9 in nondenaturing co-immunoprecipitation and confocal colocalization assays. To further understand this interaction, we found that CDK9-STAT3 binding is mediated via both STAT NH2-terminal modulatory and COOH-terminal transactivation domains. Both IL-6-inducible gamma-FBG reporter gene and endogenous mRNA expression are significantly decreased after CDK9 inhibition using the potent CDK inhibitor, flavopiridol (FP), or specific CDK9 siRNA. Moreover, chromatin immunoprecipitation (ChIP) experiments revealed an IL-6-inducible STAT3 and CDK9 binding to the proximal gamma-FBG promoter as well as increased loading of RNA Pol II and phospho-Ser2 CTD Pol II on the TATA box and coding regions. Finally, FP specifically and efficiently inhibits association of phospho-Ser2 CTD RNA Pol II on the gamma-FBG promoter, indicating that CDK9 kinase activity mediates IL-6-inducible CTD phosphorylation. Our data indicate that IL-6 induces a STAT3.CDK9 complex mediated by bivalent STAT3 domains and CDK9 kinase activity is necessary for licensing Pol II to enter a transcriptional elongation mode. Therefore, disruption of IL-6 signaling by CDK9 inhibitors could be a potential therapeutic strategy for inflammatory disease.
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Affiliation(s)
- Tieying Hou
- Department of Biochemistry, and Sealy Center for Molecular Medicine, University of Texas Medical Branch, Galveston, Texas 77555-1060, USA
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28
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Chiu YL, Cao H, Rana TM. Quantitative analysis of RNA-mediated protein-protein interactions in living cells by FRET. Chem Biol Drug Des 2007; 69:233-9. [PMID: 17461970 DOI: 10.1111/j.1747-0285.2007.00501.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Specific assembly of ribonucleoprotein complexes is essential in controlling various cellular functions including gene regulation. Diverse scaffolds containing proteins or nucleic acids could play key roles in stabilizing specific ribonucleoprotein complexes by enhancing protein-protein or RNA-protein interactions. One such example is the assembly of active RNA polymerase II transcription elongation complex originating from HIV-1 long terminal repeat promoter that involves HIV-1-encoded Tat protein and viral mRNA structure, trans-activation responsive RNA, and human CyclinT1 which is a subunit of the positive transcription elongation factor complex b. By using genetically encoded fluorescent proteins fused with Tat and human CyclinT1, here we demonstrate that human CyclinT1 was diffused throughout the nucleus and specific interactions between Tat and human CyclinT1 altered the localization of human CyclinT1 to specific nuclear foci. We also found that trans-activation responsive RNA enhanced protein-protein interactions between human CyclinT1 and Tat in living cells. Our results highlights the importance of trans-activation responsive RNA as a scaffold for stable and high affinity assembly of two protein partners to form a regulatory switch essential in HIV-1 gene regulation. RNA-mediated assembly of ribonucleoprotein complexes could be a general mechanism for stable ribonucleoprotein complex formation and a key step in regulating other cellular processes and viral replication. Furthermore, our results suggest that Tat interactions with human CyclinT1 change the nuclear location of positive transcription elongation factor complex b to modulate positive transcription elongation factor complex b function and transcription of cellular genes.
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Affiliation(s)
- Ya-Lin Chiu
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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29
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Marshall RM, Salerno D, Garriga J, Graña X. Cyclin T1 expression is regulated by multiple signaling pathways and mechanisms during activation of human peripheral blood lymphocytes. THE JOURNAL OF IMMUNOLOGY 2006; 175:6402-11. [PMID: 16272292 DOI: 10.4049/jimmunol.175.10.6402] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Stimulation of primary human T lymphocytes results in up-regulation of cyclin T1 expression, which correlates with phosphorylation of the C-terminal domain of RNA polymerase II (RNAP II). Up-regulation of cyclin T1 and concomitant stabilization of cyclin-dependent kinase 9 (CDK9) may facilitate productive replication of HIV in activated T cells. We report that treatment of PBLs with two mitogens, PHA and PMA, results in accumulation of cyclin T1 via distinct mechanisms. PHA induces accumulation of cyclin T1 mRNA and protein, which results from cyclin T1 mRNA stabilization, without significant change in cyclin T1 promoter activity. Cyclin T1 mRNA stabilization requires the activation of both calcineurin and JNK because inhibition of either precludes cyclin T1 accumulation. In contrast, PMA induces cyclin T1 protein up-regulation by stabilizing cyclin T1 protein, apparently independently of the proteasome and without accumulation of cyclin T1 mRNA. This process is dependent on Ca2+-independent protein kinase C activity but does not require ERK1/2 activation. We also found that PHA and anti-CD3 Abs induce the expression of both the cyclin/CDK complexes involved in RNAP II C-terminal domain phosphorylation and the G1-S cyclins controlling cell cycle progression. In contrast, PMA alone is a poor inducer of the expression of G1-S cyclins but often as potent as PHA in inducing RNAP II cyclin/CDK complexes. These findings suggest coordination in the expression and activation of RNAP II kinases by pathways that independently stimulate gene expression but are insufficient to induce S phase entry in primary T cells.
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Affiliation(s)
- Renée M Marshall
- Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA
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30
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Garriga J, Graña X. Cellular control of gene expression by T-type cyclin/CDK9 complexes. Gene 2004; 337:15-23. [PMID: 15276198 DOI: 10.1016/j.gene.2004.05.007] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2004] [Revised: 04/12/2004] [Accepted: 05/06/2004] [Indexed: 11/24/2022]
Abstract
The family of Cyclin-Dependent Kinases (CDKs) can be subdivided into two major functional groups based on their roles in cell cycle and/or transcriptional control. This review is centered on CDK9, which is activated by T-type cyclins and cyclin K generating distinct Positive-Transcription Elongation Factors termed P-TEFb. P-TEFb positively regulates transcriptional elongation by phosphorylating the C-terminal domain (CTD) of RNA polymerase II (RNA pol II), as well as negative elongation factors, which block elongation by RNA pol II shortly after the initiation of transcription. Work over the past few years has led to a dramatic increase in our understanding of how productive transcriptional elongation occurs. This review will briefly describe the mechanisms regulating the activity of T-type cyclin/CDK9 complexes and discuss how these complexes regulate gene expression. For further information, the reader is directed to excellent existing reviews on transcriptional elongation and HIV transcription.
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Affiliation(s)
- Judit Garriga
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, 3307 North Broad St., Philadelphia, PA 19140, USA
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31
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Chiu YL, Cao H, Jacque JM, Stevenson M, Rana TM. Inhibition of human immunodeficiency virus type 1 replication by RNA interference directed against human transcription elongation factor P-TEFb (CDK9/CyclinT1). J Virol 2004; 78:2517-29. [PMID: 14963154 PMCID: PMC369228 DOI: 10.1128/jvi.78.5.2517-2529.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The human positive transcription elongation factor P-TEFb is composed of two subunits, cyclin T1 (hCycT1) and CDK9, and is involved in transcriptional regulation of cellular genes as well as human immunodeficiency virus type 1 (HIV-1) mRNA. Replication of HIV-1 requires the Tat protein, which activates elongation of RNA polymerase II at the HIV-1 promoter by interacting with hCycT1. To understand the cellular functions of P-TEFb and to test whether suppression of host proteins such as P-TEFb can modulate HIV infectivity without causing cellular toxicity or lethality, we used RNA interference (RNAi) to specifically knock down P-TEFb expression by degrading hCycT1 or CDK9 mRNA. RNAi-mediated gene silencing of P-TEFb in HeLa cells was not lethal and inhibited Tat transactivation and HIV-1 replication in host cells. We also found that CDK9 protein stability depended on hCycT1 protein levels, suggesting that the formation of P-TEFb CDK-cyclin complexes is required for CDK9 stability. Strikingly, P-TEFb knockdown cells showed normal P-TEFb kinase activity. Our studies suggest the existence of a dynamic equilibrium between active and inactive pools of P-TEFb in the cell and indicate that this equilibrium shifts towards the active kinase form to sustain cell viability when P-TEFb protein levels are reduced. The finding that a P-TEFb knockdown was not lethal and still showed normal P-TEFb kinase activity suggested that there is a critical threshold concentration of activated P-TEFb required for cell viability and HIV replication. These results provide new insights into the regulation of P-TEFb function and suggest the possibility that similar mechanisms for monitoring protein levels to modulate the activity of proteins may exist for the regulation of a variety of other enzymatic pathways.
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Affiliation(s)
- Ya-Lin Chiu
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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32
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Das AT, Verhoef K, Berkhout B. A Conditionally Replicating Virus as a Novel Approach Toward an HIV Vaccine. Methods Enzymol 2004; 388:359-79. [PMID: 15289083 DOI: 10.1016/s0076-6879(04)88028-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Atze T Das
- Department of Human Retrovirology, Academic Medical Center, Amsterdam, The Netherlands
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33
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Kulinski T, Olejniczak M, Huthoff H, Bielecki L, Pachulska-Wieczorek K, Das AT, Berkhout B, Adamiak RW. The apical loop of the HIV-1 TAR RNA hairpin is stabilized by a cross-loop base pair. J Biol Chem 2003; 278:38892-901. [PMID: 12882959 DOI: 10.1074/jbc.m301939200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The TAR hairpin of the HIV-1 RNA genome is indispensable for trans-activation of the viral promoter and virus replication. The TAR structure has been studied extensively, but most attention has been directed at the three-nucleotide bulge that constitutes the binding site of the viral Tat protein. In contrast, the conformational properties of the apical loop have remained elusive. We performed biochemical studies and molecular dynamics simulations, which indicate that the TAR loop is structured and stabilized by a cross-loop base pair between residues C30 and G34. Mutational disruption of the cross-loop base pair results in reduced Tat response of the LTR promoter, which can be rescued by compensatory mutations that restore the base pair. Thus, Tat-mediated transcriptional activation depends on the structure of the TAR apical loop. The C30-G34 cross-loop base pair classes TAR in a growing family of hairpins with a structured loop that was recently identified in ribosomal RNA, tRNA, and several viral and cellular mRNAs.
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Affiliation(s)
- Tadeusz Kulinski
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12-14, 61-704 Poznañ, Poland
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34
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Reza SM, Rosetti M, Mathews MB, Pe'ery T. Differential activation of Tat variants in mitogen-stimulated cells: implications for HIV-1 postintegration latency. Virology 2003; 310:141-56. [PMID: 12788638 DOI: 10.1016/s0042-6822(03)00106-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Like other HIV-1 (human immunodeficiency virus type 1) proteins, Tat undergoes rapid mutation and occurs in numerous sequence variants in nature. Virus isolated from patients often has defects in Tat that lower its activity. The levels of P-TEFb, an essential cellular cofactor for Tat, are elevated by T-cell activation. To test the hypothesis that stimulation of P-TEFb levels might compensate for attenuation of Tat activity, we generated Tat constructs with a range of transactivation function. Transactivation by the Tat mutants correlated with their ability to bind to P-TEFb in vitro. Treatment of U937 cells with the phorbol ester PMA (phorbol myristate acetate) induced P-TEFb and stimulated Tat transactivation for alleles with basal transcription activity above a threshold (>5% compared to wild-type). Highly active alleles (>66% of wild-type) were stimulated to a lesser extent than those with activity in the intermediate range. Thus, attenuation of Tat function, in concert with low levels of P-TEFb activity, could serve to keep the virus in a latent state in quiescent cells yet permit viral replication after cell activation.
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Affiliation(s)
- Syed M Reza
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103-1709, USA
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35
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Abstract
Positive transcription factor b (P-TEFb) is required for RNA polymerase II to make the transition from abortive to productive elongation. This important factor is a heterodimer of a cyclin-dependent kinase, cyclin-dependent kinase 9 (Cdk9), and one of four cyclin partners, cyclin T1, T2a, T2b or K. We demonstrate here that there exists in cells a second form of Cdk9 that is 13 kDa larger than the protein originally identified. Both of these forms, which we name Cdk9(42) and Cdk9(55), are present in HeLa and NIH/3T3 cells. Cdk9(55) is generated from an mRNA that originates from a second promoter located upstream of the startpoint of transcription used to generate mRNAs encoding Cdk9(42). Antibodies specific for Cdk9(55) immunoprecipitate Cdk(55) and cyclin T1, but not Cdk9(42). Cdk9(55) in the immunoprecipitates is active as judged by its ability to phosphorylate the carboxyl-terminal domain of the largest subunit of RNA polymerase II. Recently it has been shown that the activity of P-TEFb is negatively regulated in cells by reversible association with a small cellular RNA called 7SK. We show here that P-TEFb molecules containing either form of Cdk9 are found in association with 7SK and both complexes are disrupted by treatment with 600 mM KCl. The relative abundance of Cdk9(55) and Cdk9(42) changes in different cell types, including HeLa, NIH/3T3, human macrophages and mouse lung tissue. Additionally, treatment of macrophages with lipopolysaccharides or infection with human immunodeficiency virus alters the relative abundance of the two forms of Cdk9.
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Affiliation(s)
- Sarah M Shore
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA
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36
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Hoque M, Young TM, Lee CG, Serrero G, Mathews MB, Pe'ery T. The growth factor granulin interacts with cyclin T1 and modulates P-TEFb-dependent transcription. Mol Cell Biol 2003; 23:1688-702. [PMID: 12588988 PMCID: PMC151712 DOI: 10.1128/mcb.23.5.1688-1702.2003] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cyclin T1, together with the kinase CDK9, is a component of the transcription elongation factor P-TEFb which binds the human immunodeficiency virus type 1 (HIV-1) transactivator Tat. P-TEFb facilitates transcription by phosphorylating the carboxy-terminal domain (CTD) of RNA polymerase II. Cyclin T1 is an exceptionally large cyclin and is therefore a candidate for interactions with regulatory proteins. We identified granulin as a cyclin T1-interacting protein that represses expression from the HIV-1 promoter in transfected cells. The granulins, mitogenic growth factors containing repeats of a cysteine-rich motif, were reported previously to interact with Tat. We show that granulin formed stable complexes in vivo and in vitro with cyclin T1 and Tat. Granulin bound to the histidine-rich domain of cyclin T1, which was recently found to bind to the CTD, but not to cyclin T2. Binding of granulin to P-TEFb inhibited the phosphorylation of a CTD peptide. Granulin expression inhibited Tat transactivation, and tethering experiments showed that this effect was due, at least in part, to a direct action on cyclin T1 in the absence of Tat. In addition, granulin was a substrate for CDK9 but not for the other transcription-related kinases CDK7 and CDK8. Thus, granulin is a cellular protein that interacts with cyclin T1 to inhibit transcription.
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Affiliation(s)
- Mainul Hoque
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07013-1709, USA
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37
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Sano M, Abdellatif M, Oh H, Xie M, Bagella L, Giordano A, Michael LH, DeMayo FJ, Schneider MD. Activation and function of cyclin T-Cdk9 (positive transcription elongation factor-b) in cardiac muscle-cell hypertrophy. Nat Med 2002; 8:1310-7. [PMID: 12368904 DOI: 10.1038/nm778] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2002] [Accepted: 09/16/2002] [Indexed: 12/12/2022]
Abstract
Hypertrophic growth is a risk factor for mortality in heart diseases. Mechanisms are lacking for this global increase in RNA and protein per cell, which underlies hypertrophy. Hypertrophic signals cause phosphorylation of the RNA polymerase II C-terminal domain, required for transcript elongation. RNA polymerase II kinases include cyclin-dependent kinases-7 (Cdk7) and Cdk9, components of two basal transcription factors. We report activation of Cdk7 and -9 in hypertrophy triggered by signaling proteins (Galphaq, calcineurin) or chronic mechanical stress. Only Cdk9 was activated by acute load or, in culture, by endothelin. A preferential role for Cdk9 was shown in RNA polymerase II phosphorylation and growth induced by endothelin, using pharmacological and dominant-negative inhibitors. All four hypertrophic signals dissociated 7SK small nuclear RNA, an endogenous inhibitor, from cyclin T-Cdk9. Cdk9 was limiting for cardiac growth, shown by suppressing its inhibitor (7SK) in culture and preventing downregulation of its activator (cyclin T1) in mouse myocardium.Note: In the AOP version of this article, the numbering of the author affiliations was incorrect. This has now been fixed, and the affiliations appear correctly online and in print.
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Affiliation(s)
- Motoaki Sano
- Center for Cardiovascular Development, Baylor College of Medicine, Texas, USA
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38
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Lin PS, Marshall NF, Dahmus ME. CTD phosphatase: role in RNA polymerase II cycling and the regulation of transcript elongation. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2002; 72:333-65. [PMID: 12206456 DOI: 10.1016/s0079-6603(02)72074-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The repetitive C-terminal domain (CTD) of the largest RNA polymerase II subunit plays a critical role in the regulation of gene expression. The activity of the CTD is dependent on its state of phosphorylation. A variety of CTD kinases act on RNA polymerase II at specific steps in the transcription cycle and preferentially phosphorylate distinct positions within the CTD consensus repeat. A single CTD phosphatase has been identified and characterized that in concert with CTD kinases establishes the level of CTD phosphorylation. The involvement of CTD phosphatase in controlling the progression of RNAP II around the transcription cycle, the mobilization of stored RNAP IIO, and the regulation of transcript elongation and RNA processing is discussed.
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39
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Kobor MS, Greenblatt J. Regulation of transcription elongation by phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1577:261-275. [PMID: 12213657 DOI: 10.1016/s0167-4781(02)00457-8] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The synthesis of mRNA by RNA polymerase II (RNAPII) is a multistep process that is regulated by different mechanisms. One important aspect of transcriptional regulation is phosphorylation of components of the transcription apparatus. The phosphorylation state of RNAPII carboxy-terminal domain (CTD) is controlled by a variety of protein kinases and at least one protein phosphatase. We discuss emerging genetic and biochemical evidence that points to a role of these factors not only in transcription initiation but also in elongation and possibly termination. In addition, we review phosphorylation events involving some of the general transcription factors (GTFs) and other regulatory proteins. As an interesting example, we describe the modulation of transcription associated kinases and phosphatase by the HIV Tat protein. We focus on bringing together recent findings and propose a revised model for the RNAPII phosphorylation cycle.
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Affiliation(s)
- Michael S Kobor
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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40
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Zhou C, Rana TM. A bimolecular mechanism of HIV-1 Tat protein interaction with RNA polymerase II transcription elongation complexes. J Mol Biol 2002; 320:925-42. [PMID: 12126615 DOI: 10.1016/s0022-2836(02)00556-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Transcriptional activation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) promoter element is regulated by the essential viral Tat protein that binds to the viral TAR RNA target and recruits a positive transcription elongation complex (P-TEFb). We have used a stepwise transcription approach and a highly sensitive assay to determine the dynamics of interactions between HIV-1 Tat and the transcription complexes actively engaged in elongation. Our results demonstrate that Tat protein associates with RNA polymerase II complexes during early transcription elongation after the promoter clearance and before the synthesis of full-length TAR RNA transcript. This interaction of Tat with RNA polymerase II elongation complexes is P-TEFb-independent. Our results also show that there are two Tat binding sites on each transcription elongation complex; one is located on TAR RNA and the other one on RNA polymerase II near the exit site for nascent mRNA transcripts. These findings suggest that two Tat molecules are involved in performing various functions during a single round of HIV-1 mRNA synthesis.
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Affiliation(s)
- Chao Zhou
- Chemical Biology Program, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605-2324, USA
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41
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Simone C, Bagella L, Bellan C, Giordano A. Physical interaction between pRb and cdk9/cyclinT2 complex. Oncogene 2002; 21:4158-65. [PMID: 12037672 DOI: 10.1038/sj.onc.1205511] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2001] [Revised: 03/13/2002] [Accepted: 03/21/2002] [Indexed: 11/09/2022]
Abstract
Cyclin-dependent kinase 9 (cdk9) is a multifunctional kinase with roles in different cellular pathways such as transcriptional elongation, differentiation and apoptosis. Cdk9/cyclin T differs functionally from other cdk/cyclin complexes that regulate cell cycle progression, but maintains structural affinity with those complexes. In addition, previous reports have demonstrated that the cdk9 complex is able to phosphorylate p56/pRb in vitro. In this report we show in vitro and in vivo interaction between cdk9/cyclinT2 and the protein product of the retinoblastoma gene (pRb) in human cell lines. The interaction involves the region composed of residues 129-195 of cdk9, cyclinT2 (1-642 aa) and the C-terminal domain of pRb (835-928 aa). We located the minimal region of cdk9 phosphorylation on the C-terminus of pRb, by identifying the residues between 793 and 834. This region contains at least three proline-directed serines (sp), S795, S807 and S811, which have been reported to be phosphorylated in vivo and which could be targeted by the cdk9 complex. These data suggest that, in logarithmically growing cells, cdk9/cyclin T2 and pRb are located in a nuclear multiprotein complex probably involved in transduction of cellular signals to the basal transcription machinery and that one of these signals could be the cdk9 phosphorylation of pRb.
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Affiliation(s)
- Cristiano Simone
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, PA 19107, USA
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42
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Simone C, Stiegler P, Bagella L, Pucci B, Bellan C, De Falco G, De Luca A, Guanti G, Puri PL, Giordano A. Activation of MyoD-dependent transcription by cdk9/cyclin T2. Oncogene 2002; 21:4137-48. [PMID: 12037670 DOI: 10.1038/sj.onc.1205493] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2001] [Revised: 03/01/2002] [Accepted: 03/18/2002] [Indexed: 11/09/2022]
Abstract
Myogenic transcription is repressed in myoblasts by serum-activated cyclin-dependent kinases, such as cdk2 and cdk4. Serum withdrawal promotes muscle-specific gene expression at least in part by down-regulating the activity of these cdks. Unlike the other cdks, cdk9 is not serum- or cell cycle-regulated and is instead involved in the regulation of transcriptional elongation by phosphorylating the carboxyl-terminal domain (CTD) of RNA polymerase II. While ectopic expression of cdk2 together with its regulatory subunits (cyclins E and A) inhibits myogenic transcription, overproduction of cdk9 and its associated cyclin (cyclin T2a) strengthens MyoD-dependent transcription and stimulates myogenic differentiation in both MyoD-converted fibroblasts and C2C12 muscle cells. Conversely, inhibition of cdk9 activity by a dominant negative form (cdk9-dn) represses the myogenic program. Cdk9, cyclinT2 and MyoD can be detected in a multimeric complex in C2C12 cells, with the minimal cdk9-binding region of MyoD mapping within 101-161 aa of the bHLH region. Finally, cdk9 can phosphorylate MyoD in vitro, suggesting the possibility that cdk9/cycT2a regulation of muscle differentiation includes the direct enzymatic activity of the kinase on MyoD.
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Affiliation(s)
- Cristiano Simone
- Sbarro Institute for Cancer Research and Molecular Medicine, Temple University, Philadelphia, Pennsylvania, PA 19122, USA
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43
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Richter S, Ping YH, Rana TM. TAR RNA loop: a scaffold for the assembly of a regulatory switch in HIV replication. Proc Natl Acad Sci U S A 2002; 99:7928-33. [PMID: 12048247 PMCID: PMC122997 DOI: 10.1073/pnas.122119999] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2002] [Indexed: 11/18/2022] Open
Abstract
Replication of HIV requires the Tat protein, which activates elongation of RNA polymerase II transcription at the HIV-1 promoter by interacting with the cyclin T1 (CycT1) subunit of the positive transcription elongation factor complex b (P-TEFb). The transactivation domain of Tat binds directly to the CycT1 subunit of P-TEFb and induces loop sequence-specific binding of P-TEFb onto nascent HIV-1 trans-activation responsive region (TAR) RNA. We used systematic RNA-protein photocross-linking, Western blot analysis, and protein footprinting to show that residues 252-260 of CycT1 interact with one side of the TAR RNA loop and enhance interaction of Tat residue K50 to the other side of the loop. Our results show that TAR RNA provides a scaffold for two protein partners to bind and assemble a regulatory switch in HIV replication. RNA-mediated assembly of RNA-protein complexes could be a general mechanism for stable ribonucleoprotein complex formation and a key step in regulating other cellular processes and viral replication.
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Affiliation(s)
- Sara Richter
- Chemical Biology Program, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA
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44
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Du Z, Lind KE, James TL. Structure of TAR RNA complexed with a Tat-TAR interaction nanomolar inhibitor that was identified by computational screening. CHEMISTRY & BIOLOGY 2002; 9:707-12. [PMID: 12079782 DOI: 10.1016/s1074-5521(02)00151-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
HIV-1 TAR RNA functions critically in viral replication by binding the transactivating regulatory protein Tat. We recently identified several compounds that experimentally inhibit the Tat-TAR interaction completely at a 100 nM concentration. We used computational screening of the 181,000-compound Available Chemicals Directory against the three-dimensional structure of TAR [1]. Here we report the NMR-derived structure of TAR complexed with acetylpromazine. This structure represents a new class of compounds with good bioavailability and low toxicity that bind with high affinity to TAR. NMR data unambiguously show that acetylpromazine binds only to the unique 5' bulge site to which the Tat protein binds. Specificity and affinity of binding are conferred primarily by a network of base stacking and hydrophobic interactions. Acetylpromazine alters the structure of free TAR less than Tat peptides and neomycin do.
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Affiliation(s)
- Zhihua Du
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Franciso, CA 94143, USA
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45
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Lind KE, Du Z, Fujinaga K, Peterlin BM, James TL. Structure-based computational database screening, in vitro assay, and NMR assessment of compounds that target TAR RNA. CHEMISTRY & BIOLOGY 2002; 9:185-93. [PMID: 11880033 DOI: 10.1016/s1074-5521(02)00106-0] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
There has been little prior effort to discover new drugs on the basis of a unique RNA structure. Binding of the viral transactivator Tat to the 5' bulge of the transactivation response (TAR) element is necessary for HIV-1 replication, so TAR RNA is a superb target. A computational approach was developed to screen a large chemical library for binding to a three-dimensional RNA structure. Scoring function development, flexible ligand docking, and limited target flexibility were essential. From the ranked list of compounds predicted to bind TAR, 43 were assayed for inhibition of the Tat-TAR interaction via electrophoretic mobility shift assays. Eleven compounds (between 0.1 and 1 microM) inhibited the Tat-TAR interaction, and some inhibited Tat transactivation in cells. NMR spectra verified specific binding to the 5' bulge and no interaction with other regions of TAR.
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Affiliation(s)
- Kenneth E Lind
- Department of Pharmaceutical Chemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143, USA
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46
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Martin-Serrano J, Li K, Bieniasz PD. Cyclin T1 expression is mediated by a complex and constitutively active promoter and does not limit human immunodeficiency virus type 1 Tat function in unstimulated primary lymphocytes. J Virol 2002; 76:208-19. [PMID: 11739686 PMCID: PMC135689 DOI: 10.1128/jvi.76.1.208-219.2002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cyclin T1 (CycT1), a component of positive-transcription-elongation factor-b (P-TEFb), is an essential cofactor for transcriptional activation by lentivirus Tat proteins. It is thought that low CycT1 expression levels restrict human immunodeficiency virus type 1 (HIV-1) expression levels and replication in resting CD4+ lymphocytes. In this study, we undertook a functional analysis of the cycT1 promoter to determine which, if any, promoter elements might be responsible for cellular activation state-dependent CycT1 expression. The cycT1 gene contains a complex promoter that exhibits an extreme degree of functional redundancy: five nonoverlapping fragments were found to exhibit significant promoter activity in immortalized cell lines, and these elements could interact in a synergistic or redundant manner to mediate cycT1 transcription. Reporter gene expression, mediated by the cycT1 promoter, was detectable in unstimulated transfected primary lymphocytes and multiple sites within the promoter could serve to initiate transcription. While utilization of these start sites was significantly altered by the application of exogenous stimuli to primary lymphocytes and two distinct promoter elements exhibited enhanced activity in the presence of phorbol ester, overall cycT1 transcription was only modestly enhanced in response to cell activation. These observations prompted a reexamination of CycT1 protein expression in primary lymphocytes. In fact, steady-state CycT1 expression is only slightly lower in unstimulated lymphocytes compared to phorbol ester-treated cells or a panel of immortalized cell lines. Importantly, CycT1 is expressed at sufficient levels in unstimulated primary cells to support robust Tat activity. These results strongly suggest that CycT1 expression levels in unstimulated primary lymphocytes do not profoundly limit HIV-1 gene expression or provide an adequate mechanistic explanation for proviral latency in vivo.
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Affiliation(s)
- Juan Martin-Serrano
- Aaron Diamond AIDS Research Center, Rockefeller University, New York, New York 10016, USA
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47
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Zhou M, Nekhai S, Bharucha DC, Kumar A, Ge H, Price DH, Egly JM, Brady JN. TFIIH inhibits CDK9 phosphorylation during human immunodeficiency virus type 1 transcription. J Biol Chem 2001; 276:44633-40. [PMID: 11572868 DOI: 10.1074/jbc.m107466200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tat stimulates human immunodeficiency virus, type 1 (HIV-1), transcription elongation by recruitment of the human transcription elongation factor P-TEFb, consisting of CDK9 and cyclin T1, to the TAR RNA structure. It has been demonstrated further that CDK9 phosphorylation is required for high affinity binding of Tat/P-TEFb to the TAR RNA structure and that the state of P-TEFb phosphorylation may regulate Tat transactivation. We now demonstrate that CDK9 phosphorylation is uniquely regulated in the HIV-1 preinitiation and elongation complexes. The presence of TFIIH in the HIV-1 preinitiation complex inhibits CDK9 phosphorylation. As TFIIH is released from the elongation complex between +14 and +36, CDK9 phosphorylation is observed. In contrast to the activity in the "soluble" complex, phosphorylation of CDK9 is increased by the presence of Tat in the transcription complexes. Consistent with these observations, we have demonstrated that purified TFIIH directly inhibits CDK9 autophosphorylation. By using recombinant TFIIH subcomplexes, our results suggest that the XPB subunit of TFIIH is responsible for this inhibition of CDK9 phosphorylation. Interestingly, our results further suggest that the phosphorylated form of CDK9 is the active kinase for RNA polymerase II carboxyl-terminal domain phosphorylation.
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Affiliation(s)
- M Zhou
- Virus Tumor Biology Section, Basic Research Laboratory, Division of Basic Sciences, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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Deng L, Wang D, de la Fuente C, Wang L, Li H, Lee CG, Donnelly R, Wade JD, Lambert P, Kashanchi F. Enhancement of the p300 HAT activity by HIV-1 Tat on chromatin DNA. Virology 2001; 289:312-26. [PMID: 11689053 DOI: 10.1006/viro.2001.1129] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
HIV-1 Tat is able to form a ternary complex with P/CAF and p300 and increase the affinity for CDK9/P-TEFb CTD kinase complex. Our previous study demonstrated that Tat binds to p300/CBP in the minimal HAT domain (aa 1253-1790) and that the interaction results in a change of conformation on p300/CBP. Here, we show that the Tat-p300 interaction increases the HAT activity of p300 on histone H4 that is associated with nucleosomal DNA and not with free histones. Nucleosomal histone H4 was acetylated on lysines 8, 12, and 16. Acetylation of H4 was inhibited by Lys-coenzyme A (CoA), a selective inhibitor of p300 acetyltransferase activity. Unexpectedly, we also found that Tat could autoacetylate itself, which was specific to lysine residues 41 and 71. Peptides lacking these two lysines could not enhance the HAT activity of p300. Comparison of the sequences of Tat with other HIV-1 clades and HAT containing transcription factors indicated sequence identity in the acetyl-CoA binding motif A, KGXG. Furthermore, when utilizing an in vitro transcription assay, as well as a Tat mutant virus, we found that ectopic expression of only wild-type Tat in the presence of p300, and not a lysine 41 Tat mutant, could activate HIV-1 chromatin DNA, as evidenced by the absence of HIV-1 virion antigen. Therefore, transcription of integrated viral DNA in vivo requires the HAT activity of coactivators that are modulated by Tat to derepress the HIV-1 chromatin structure and aid in activated transcription.
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Affiliation(s)
- L Deng
- Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School, Newark, New Jersey 07103, USA
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49
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Marcello A, Cinelli RA, Ferrari A, Signorelli A, Tyagi M, Pellegrini V, Beltram F, Giacca M. Visualization of in vivo direct interaction between HIV-1 TAT and human cyclin T1 in specific subcellular compartments by fluorescence resonance energy transfer. J Biol Chem 2001; 276:39220-5. [PMID: 11504720 DOI: 10.1074/jbc.m104830200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human cyclin T1, a component of the P-TEFb kinase complex, was originally identified through its biochemical interaction with the Tat transactivator protein of human immunodeficiency virus type 1 (HIV-1). Current understanding suggests that binding of Tat to P-TEFb is required to promote efficient transcriptional elongation of viral RNAs. However, the dynamics and the subnuclear localization of this process are still largely unexplored in vivo. Here we exploit high resolution fluorescence resonance energy transfer (FRET) to visualize and quantitatively analyze the direct interaction between Tat and cyclin T1 inside the cells. We observed that cyclin T1 resides in specific subnuclear foci which are in close contact with nuclear speckles and that Tat determines its redistribution outside of these compartments. Consistent with this observation, strong FRET was observed between the two proteins both in the cytoplasm and in regions of the nucleus outside of cyclin T1 foci and overlapping with Tat localization. These results are consistent with a model by which Tat recruits cyclin T1 outside of the nuclear compartments where the protein resides to promote transcriptional activation.
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Affiliation(s)
- A Marcello
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, 34012 Trieste, Italy
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50
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Fraldi A, Licciardo P, Majello B, Giordano A, Lania L. Distinct regions of cyclinT1 are required for binding to CDK9 and for recruitment to the HIV-1 Tat/TAR complex. JOURNAL OF CELLULAR BIOCHEMISTRY. SUPPLEMENT 2001; Suppl 36:247-53. [PMID: 11455589 DOI: 10.1002/jcb.1149] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Tat-mediated activation of the HIV-1 promoter activity requires Tat-dependent recruitment of the cyclinT1/CDK9 complex (P-TEFb) to the transacting element (TAR) RNA. Tat interaction with the cyclinT1, the regulatory partner of CDK9, results in a specific recruitment of the heterodimer CycT1/CDK9 complex to TAR, whereby it promotes transcription elongation of the HIV-1 LTR-mediated transcription. Using the yeast two-hybrid protein interaction assay we analyzed the binding between cyclinT1 and CDK9. Moreover, using a modified three-hybrid yeast interaction system, we analyzed the recruitment of CycT1 to the Tat/TAR complex. The data presented here demonstrated that distinct domains of cyclinT1 interact with CDK9 and Tat/TAR in vivo. These findings will be instrumental for the designing of proper dominant-negative P-TEFb components capable to interfere with Tat function. J. Cell. Biochem. Suppl. 36: 247-253, 2001.
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Affiliation(s)
- A Fraldi
- Department of Genetics, Molecular and General Biology, University Federico II, Via Mezzocannone 8, 80134 Naples, Italy
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