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Human Immunodeficiency Virus Type 1 Tat and Rev as Potential Targets for Drug Development. Antiviral Res 2014. [DOI: 10.1128/9781555815493.ch6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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2
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Bahr GM. Immune deficiency in HIV-1 infection: novel therapeutic approaches targeting innate and adaptive responses. Expert Rev Clin Immunol 2014; 1:529-47. [DOI: 10.1586/1744666x.1.4.529] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Yasuda-Inoue M, Kuroki M, Ariumi Y. DDX3 RNA helicase is required for HIV-1 Tat function. Biochem Biophys Res Commun 2013; 441:607-11. [PMID: 24183723 DOI: 10.1016/j.bbrc.2013.10.107] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 10/21/2013] [Indexed: 10/26/2022]
Abstract
Host RNA helicase has been involved in human immunodeficiency virus type 1 (HIV-1) replication, since HIV-1 does not encode an RNA helicase. Indeed, DDX1 and DDX3 DEAD-box RNA helicases are known to be required for efficient HIV-1 Rev-dependent RNA export. However, it remains unclear whether DDX RNA helicases modulate the HIV-1 Tat function. In this study, we demonstrate, for the first time, that DDX3 is required for the HIV-1 Tat function. Notably, DDX3 colocalized and interacted with HIV-1 Tat in cytoplasmic foci. Indeed, DDX3 localized in the cytoplasmic foci P-bodies or stress granules under stress condition after the treatment with arsenite. Importantly, only DDX3 enhanced the Tat function, while various distinct DEAD-box RNA helicases including DDX1, DDX3, DDX5, DDX17, DDX21, and DDX56, stimulated the HIV-1 Rev-dependent RNA export function, indicating a specific role of DDX3 in Tat function. Indeed, the ATPase-dependent RNA helicase activity of DDX3 seemed to be required for the Tat function as well as the colocalization with Tat. Furthermore, the combination of DDX3 with other distinct DDX RNA helicases cooperated to stimulate the Rev but not Tat function. Thus, DDX3 seems to interact with the HIV-1 Tat and facilitate the Tat function.
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Shadrick WR, Ndjomou J, Kolli R, Mukherjee S, Hanson AM, Frick DN. Discovering new medicines targeting helicases: challenges and recent progress. ACTA ACUST UNITED AC 2013; 18:761-81. [PMID: 23536547 PMCID: PMC4427233 DOI: 10.1177/1087057113482586] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Helicases are ubiquitous motor proteins that separate and/or rearrange nucleic acid duplexes in reactions fueled by adenosine triphosphate (ATP) hydrolysis. Helicases encoded by bacteria, viruses, and human cells are widely studied targets for new antiviral, antibiotic, and anticancer drugs. This review summarizes the biochemistry of frequently targeted helicases. These proteins include viral enzymes from herpes simplex virus, papillomaviruses, polyomaviruses, coronaviruses, the hepatitis C virus, and various flaviviruses. Bacterial targets examined include DnaB-like and RecBCD-like helicases. The human DEAD-box protein DDX3 is the cellular antiviral target discussed, and cellular anticancer drug targets discussed are the human RecQ-like helicases and eIF4A. We also review assays used for helicase inhibitor discovery and the most promising and common helicase inhibitor chemotypes, such as nucleotide analogues, polyphenyls, metal ion chelators, flavones, polycyclic aromatic polymers, coumarins, and various DNA binding pharmacophores. Also discussed are common complications encountered while searching for potent helicase inhibitors and possible solutions for these problems.
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Affiliation(s)
- William R Shadrick
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA
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5
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Chen CY, Liu X, Boris-Lawrie K, Sharma A, Jeang KT. Cellular RNA helicases and HIV-1: insights from genome-wide, proteomic, and molecular studies. Virus Res 2013; 171:357-65. [PMID: 22814432 PMCID: PMC3493675 DOI: 10.1016/j.virusres.2012.06.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Revised: 06/25/2012] [Accepted: 06/25/2012] [Indexed: 11/24/2022]
Abstract
RNA helicases are ubiquitous in plants and animals and function in many cellular processes. Retroviruses, such as human immunodeficiency virus (HIV-1), encode no RNA helicases in their genomes and utilize host cellular RNA helicases at various stages of their life cycle. Here, we briefly summarize the roles RNA helicases play in HIV-1 replication that have been identified recently, in part, through genome-wide screenings, proteomics, and molecular studies. Some of these helicases augment virus propagation while others apparently participate in antiviral defenses against viral replication.
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Affiliation(s)
- Chia-Yen Chen
- Molecular Virology Section1, Laboratory of Molecular, Microbiology, the National Institute of Allergy and Infectious Diseases, the National Institutes of Health, Bethesda, MD, USA 20892
| | - Xiang Liu
- Molecular Virology Section1, Laboratory of Molecular, Microbiology, the National Institute of Allergy and Infectious Diseases, the National Institutes of Health, Bethesda, MD, USA 20892
| | - Kathleen Boris-Lawrie
- Department of Veterinary Biosciences, Center for Retrovirus Research, Ohio State University, Columbus, OH USA 43210
| | - Amit Sharma
- Department of Veterinary Biosciences, Center for Retrovirus Research, Ohio State University, Columbus, OH USA 43210
| | - Kuan-Teh Jeang
- Molecular Virology Section1, Laboratory of Molecular, Microbiology, the National Institute of Allergy and Infectious Diseases, the National Institutes of Health, Bethesda, MD, USA 20892
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6
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Abstract
RNA helicases unwind their RNA substrates in an ATP-dependent reaction, and are central to all cellular processes involving RNA. They have important roles in viral life cycles, where RNA helicases are either virus-encoded or recruited from the host. Vertebrate RNA helicases sense viral infections, and trigger the innate antiviral immune response. RNA helicases have been implicated in protozoic, bacterial and fungal infections. They are also linked to neurological disorders, cancer, and aging processes. Genome-wide studies continue to identify helicase genes that change their expression patterns after infection or disease outbreak, but the mechanism of RNA helicase action has been defined for only a few diseases. RNA helicases are prognostic and diagnostic markers and suitable drug targets, predominantly for antiviral and anti-cancer therapies. This review summarizes the current knowledge on RNA helicases in infection and disease, and their growing potential as drug targets.
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Affiliation(s)
- Lenz Steimer
- University of Muenster, Institute for Physical Chemistry, Muenster, Germany
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7
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Abstract
RNA helicases are encoded by all eukaryotic and prokaryotic cells and a minority of viruses. Activity of RNA helicases is necessary for all steps in the expression of cells and viruses and the host innate response to virus infection. Their vast functional repertoire is attributable to the core ATP-dependent helicase domain in conjunction with flanking domains that are interchangeable and engage viral and cellular cofactors. Here, we address the important issue of host RNA helicases that are necessary for replication of a virus. This chapter covers approaches to identification and characterization of candidate helicases and methods to define the biochemical and biophysical parameters of specificity and functional activity of the enzymes. We discuss the context of cellular RNA helicase activity and virion-associated RNA helicases. The methodology and choice of controls fosters the assessment of the virologic scope of RNA helicases across divergent cell lineages and viral replication cycles.
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Affiliation(s)
- Amit Sharma
- Department of Veterinary Biosciences, Ohio State University, Columbus, Ohio, USA,Center for Retrovirus Research, Ohio State University, Columbus, Ohio, USA,Center for RNA Biology, Ohio State University, Columbus, Ohio, USA,Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, USA
| | - Kathleen Boris-Lawrie
- Department of Veterinary Biosciences, Ohio State University, Columbus, Ohio, USA,Center for Retrovirus Research, Ohio State University, Columbus, Ohio, USA,Center for RNA Biology, Ohio State University, Columbus, Ohio, USA,Comprehensive Cancer Center, Ohio State University, Columbus, Ohio, USA
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8
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Lever AML, Jeang KT. Insights into cellular factors that regulate HIV-1 replication in human cells. Biochemistry 2011; 50:920-31. [PMID: 21218853 DOI: 10.1021/bi101805f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Retroviruses integrate into the host cell's chromosome. Accordingly, many aspects of the life cycle of retroviruses like HIV-1 are intimately linked to the functions of cellular proteins and RNAs. In this review, we discuss in brief recent genomewide screens for the identification of cellular proteins that assist HIV-1 replication in human cells. We also review findings for other cellular moieties that help or restrict the viral life cycle.
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Affiliation(s)
- Andrew M L Lever
- Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, U.K
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9
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Antiretroviral therapy down-regulates innate antiviral response genes in patients with AIDS in sub-saharan Africa. J Acquir Immune Defic Syndr 2011; 55:428-38. [PMID: 20838227 DOI: 10.1097/qai.0b013e3181ef4963] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
OBJECTIVE HIV pathogenesis is characterized by destructive imbalances between virus-mediated immune damage, antiviral immune responses, and immune activation. We characterized the effects of successful antiretroviral therapy (ART) to identify the breadth and patterns of HIV-associated gene expression. METHODS In a prospective observational, longitudinal cohort study of 10 ART-naive Ugandans with AIDS (median 30 CD4/μL), we measured mRNA gene profiles in peripheral blood using Affymetrix U133_Plus2.0 microarrays at 0, 2, 4, 8, and 24 weeks after ART initiation. RESULTS We identified 160 mRNA transcripts that were consistently down-regulated and 48 that were up-regulated after ART at each point over 24 weeks based on linear regression modeling (adjusted P < 0.05), Of these 208 transcripts, approximately half represent heretofore unrecognized ART-responsive genes and one-third have no known function. The down-regulated genes with known function encoded mediators of innate antiviral responses, including antiviral restriction factors, pattern recognition receptors, and interferon response proteins, and mediators of immune activation, cellular proliferation, and apoptosis. CONCLUSIONS By using ART to block the viral stimulus, we identified transcripts involved in innate antiviral immunity, including antiviral restriction factors and pattern recognition receptors, that were not previously known to be induced by HIV infection.
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Ranji A, Boris-Lawrie K. RNA helicases: emerging roles in viral replication and the host innate response. RNA Biol 2010; 7:775-87. [PMID: 21173576 DOI: 10.4161/rna.7.6.14249] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
RNA helicases serve multiple roles at the virus-host interface. In some situations, RNA helicases are essential host factors to promote viral replication; however, in other cases they serve as a cellular sensor to trigger the antiviral state in response to viral infection. All family members share the conserved ATP-dependent catalytic core linked to different substrate recognition and protein-protein interaction domains. These flanking domains can be shuffled between different helicases to achieve functional diversity. This review summarizes recent studies, which have revealed two types of activity by RNA helicases. First, RNA helicases are catalysts of progressive RNA-protein rearrangements that begin at gene transcription and culminate in mRNA translation. Second, RNA helicases can act as a scaffold for alternative protein-protein interactions that can defeat the antiviral state. The mounting fundamental understanding of RNA helicases is being used to develop selective and efficacious drugs against human and animal pathogens. The analysis of RNA helicases in virus model systems continues to provide insights into virology, cell biology and immunology, and has provided fresh perspective to continue unraveling the complexity of virus-host interactions.
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Affiliation(s)
- Arnaz Ranji
- Department of Veterinary Biosciences, Ohio State University, Columbus, OH, USA
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Barral PM, Sarkar D, Su ZZ, Barber GN, DeSalle R, Racaniello VR, Fisher PB. Functions of the cytoplasmic RNA sensors RIG-I and MDA-5: key regulators of innate immunity. Pharmacol Ther 2009; 124:219-34. [PMID: 19615405 DOI: 10.1016/j.pharmthera.2009.06.012] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 06/22/2009] [Indexed: 12/13/2022]
Abstract
The innate immune system responds within minutes of infection to produce type I interferons and pro-inflammatory cytokines. Interferons induce the synthesis of cell proteins with antiviral activity, and also shape the adaptive immune response by priming T cells. Despite the discovery of interferons over 50 years ago, only recently have we begun to understand how cells sense the presence of a virus infection. Two families of pattern recognition receptors have been shown to distinguish unique molecules present in pathogens, such as bacterial and fungal cell wall components, viral RNA and DNA, and lipoproteins. The first family includes the membrane-bound toll-like receptors (TLRs). Studies of the signaling pathways that lead from pattern recognition to cytokine induction have revealed extensive and overlapping cascades that involve protein-protein interactions and phosphorylation, and culminate in activation of transcription proteins that control the transcription of genes encoding interferons and other cytokines. A second family of pattern recognition receptors has recently been identified, which comprises the cytoplasmic sensors of viral nucleic acids, including MDA-5, RIG-I, and LGP2. In this review we summarize the discovery of these cytoplasmic sensors, how they recognize nucleic acids, the signaling pathways leading to cytokine synthesis, and viral countermeasures that have evolved to antagonize the functions of these proteins. We also consider the function of these cytoplasmic sensors in apoptosis, development and differentiation, and diabetes.
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Affiliation(s)
- Paola M Barral
- Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA, USA.
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12
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Huang M, Mitchell BS. Guanine nucleotide depletion mediates translocation of nucleolar proteins, including RNA helicase A (DHX-9). NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2008; 27:704-11. [PMID: 18600529 DOI: 10.1080/15257770802145132] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
DHX-9, a member of the DEXH family of RNA helicases, unwinds dsRNA/dsDNA by ATP or GTP-dependent hydrolysis. We asked whether DHX-9 played a role in the GTP depletion-induced inhibition of rRNA synthesis and/or nucleolar disruption. MPA, a specific inhibitor of inosine monophosphate dehydrogenase (IMPDH), induced a rapid translocation of DHX-9 from the nucleolus to the nucleus. EGFP-tagged DHX-9 mutated at the GTP binding site also localized to the nucleus. However, knockdown of DHX-9 by siRNA did not inhibit the rRNA synthesis or cause the nucleolar disruption. Thus, DHX-9 translocation found with IMPDH inhibition does not mediate the inhibition of rRNA synthesis.
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Affiliation(s)
- Min Huang
- Department of Medicine, Division of Oncology, Stanford Cancer Center, Stanford University, Stanford, California 94305-5796, USA
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13
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Yedavalli VSRK, Zhang N, Cai H, Zhang P, Starost MF, Hosmane RS, Jeang KT. Ring expanded nucleoside analogues inhibit RNA helicase and intracellular human immunodeficiency virus type 1 replication. J Med Chem 2008; 51:5043-51. [PMID: 18680273 DOI: 10.1021/jm800332m] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A series of ring expanded nucleoside (REN) analogues were synthesized and screened for inhibition of cellular RNA helicase activity and human immunodeficiency virus type 1 (HIV-1) replication. We identified two compounds, 1 and 2, that inhibited the ATP dependent activity of human RNA helicase DDX3. Compounds 1 and 2 also suppressed HIV-1 replication in T cells and monocyte-derived macrophages. Neither compound at therapeutic doses was significantly toxic in ex vivo cell culture or in vivo in mice. Our findings provide proof-of-concept that a cellular factor, an RNA helicase, could be targeted for inhibiting HIV-1 replication.
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Affiliation(s)
- Venkat S R K Yedavalli
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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14
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Ma J, Rong L, Zhou Y, Roy BB, Lu J, Abrahamyan L, Mouland AJ, Pan Q, Liang C. The requirement of the DEAD-box protein DDX24 for the packaging of human immunodeficiency virus type 1 RNA. Virology 2008; 375:253-64. [PMID: 18289627 DOI: 10.1016/j.virol.2008.01.025] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 01/10/2008] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
RNA helicases play important roles in RNA metabolism. Human immunodeficiency virus type 1 (HIV-1) does not carry its own RNA helicase, the virus thus needs to exploit cellular RNA helicases to promote the replication of its RNA at various steps such as transcription, folding and transport. In this study, we report that knockdown of a DEAD-box protein named DDX24 inhibits the packaging of HIV-1 RNA and thus diminishes viral infectivity. The decreased viral RNA packaging as a result of DDX24-knockdown is observed only in the context of the Rev/RRE (Rev response element)-dependent but not the CTE (constitutive transport element)-mediated nuclear export of viral RNA, which is explained by the specific interaction of DDX24 with the Rev protein. We propose that DDX24 acts at the early phase of HIV-1 RNA metabolism prior to nuclear export and the consequence of this action extends to the viral RNA packaging stage during virus assembly.
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15
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Ishaq M, Hu J, Wu X, Fu Q, Yang Y, Liu Q, Guo D. Knockdown of cellular RNA helicase DDX3 by short hairpin RNAs suppresses HIV-1 viral replication without inducing apoptosis. Mol Biotechnol 2008; 39:231-8. [PMID: 18259889 DOI: 10.1007/s12033-008-9040-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 01/14/2008] [Indexed: 02/02/2023]
Abstract
The targeting of a cellular co-factor, rather than the HIV-1-specific RNAs, by small interfering RNAs holds promise as the rapid mutational ability of the HIV-1 genome may obviate the potential clinical use of RNAi against this virus. The DEAD-box RNA helicase DDX3 is an essential Rev co-factor in the CRM1-Rev-RRE complex that promotes the export of unspliced and single-spliced HIV-1 RNAs from the nucleus to cytoplasm. In this report, human DDX3 was targeted by specific short hairpin RNAs, and the down-regulation of cell's endogenous DDX3 suppressed the nuclear export of unspliced HIV-1 RNAs but did not affect the cell viability. We further showed that the knockdown of cellular DDX3 could effectively inhibit the replication of HIV-1. Therefore, the current results suggest that the RNA helicase DDX3 may become a potential target by RNAi for future genetic therapy of HIV/AIDS.
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Affiliation(s)
- Musarat Ishaq
- State Key Laboratory of Virology and Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, China
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16
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Zhou Y, Ma J, Bushan Roy B, Wu JYY, Pan Q, Rong L, Liang C. The packaging of human immunodeficiency virus type 1 RNA is restricted by overexpression of an RNA helicase DHX30. Virology 2007; 372:97-106. [PMID: 18022663 DOI: 10.1016/j.virol.2007.10.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Revised: 08/21/2007] [Accepted: 10/23/2007] [Indexed: 10/22/2022]
Abstract
RNA helicases are a large family of proteins that are able to unwind RNA duplex and remodel the structure of RNA-protein (RNP) complexes using energy derived from hydrolysis of nucleotide triphosphates (NTPs). Every step of cellular RNA metabolism involves the activity of RNA helicases. Not surprisingly, more and more RNA helicases are reported to participate in the replication of viruses including the human immunodeficiency virus type 1 (HIV-1). Here, we provide evidence that overexpression of an RNA helicase named DHX30 enhances HIV-1 gene expression, but leads to the generation of viruses that package significantly low levels of viral RNA and exhibit severely decreased infectivity. These data reveal the complex roles of DHX30 in HIV-1 replication and implicate an inhibitory activity of DHX30 in HIV-1 RNA packaging.
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Affiliation(s)
- Yongdong Zhou
- McGill AIDS Centre, Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada
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Audigé A, Urosevic M, Schlaepfer E, Walker R, Powell D, Hallenberger S, Joller H, Simon HU, Dummer R, Speck RF. Anti-HIV state but not apoptosis depends on IFN signature in CD4+ T cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:6227-37. [PMID: 17056552 DOI: 10.4049/jimmunol.177.9.6227] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
To gain insights into the molecular mechanisms underlying early host responses to HIV in the CD4(+) T cell target population, we examined gene expression in CD4(+) T cells isolated 24 h after ex vivo HIV infection of lymphocyte aggregate cultures derived from human tonsils. Gene profiling showed a distinct up-regulation of genes related to immune response and response to virus, notably of IFN-stimulated genes (ISGs), irrespective of the coreceptor tropism of the virus. This mostly IFN-alpha-dependent gene signature suggested the involvement of plasmacytoid dendritic cells, a principal component of the antiviral immune response. Indeed, depletion of plasmacytoid dendritic cells before HIV inoculation abrogated transcriptional up-regulation of several ISGs and resulted in increased levels of HIV replication. Treatment with a blocking anti-IFN-alphaR Ab yielded increased HIV replication; conversely, HIV replication was decreased in pDC-depleted cultures treated with IFN-alpha. Among up-regulated ISGs was also TRAIL, indicating a potential role of the IFN signature in apoptosis. However, a blocking anti-TRAIL Ab did not abrogate apoptosis of CD4(+) T cells in CXCR4-tropic HIV-infected cultures, suggesting the involvement of pathways other than TRAIL mediated. We conclude that acute HIV infection of lymphoid tissue results in up-regulation of ISGs in CD4(+) T cells, which induces an anti-HIV state but not apoptosis.
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Affiliation(s)
- Annette Audigé
- Division of Infectious Diseases and Hospital Epidemiology, University Hospital of Zurich, Raemistrasse 100, 8091 Zurich, Switzerland
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18
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Abstract
Viruses are replication competent genomes which are relatively gene-poor. Even the largest viruses (i.e. Herpesviruses) encode only slightly >200 open reading frames (ORFs). However, because viruses replicate obligatorily inside cells, and considering that evolution may be driven by a principle of economy of scale, it is reasonable to surmise that many viruses have evolved the ability to co-opt cell-encoded proteins to provide needed surrogate functions. An in silico survey of viral sequence databases reveals that most positive-strand and double-stranded RNA viruses have ORFs for RNA helicases. On the other hand, the genomes of retroviruses are devoid of virally-encoded helicase. Here, we review in brief the notion that the human immunodeficiency virus (HIV-1) has adopted the ability to use one or more cellular RNA helicases for its replicative life cycle.
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Affiliation(s)
- Kuan-Teh Jeang
- Molecular Virology Section, Laboratory of Molecular Medicine, NIAID, NIH, Bethesda, MD 20892, USA.
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19
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Lin L, Su Z, Lebedeva IV, Gupta P, Boukerche H, Rai T, Barber GN, Dent P, Sarkar D, Fisher PB. Activation of Ras/Raf protects cells from melanoma differentiation-associated gene-5-induced apoptosis. Cell Death Differ 2006; 13:1982-93. [PMID: 16575407 DOI: 10.1038/sj.cdd.4401899] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Melanoma differentiation-associated gene-5 (mda-5) was the first molecule identified in nature whose encoded protein embodied the unique structural combination of an N-terminal caspase recruitment domain and a C-terminal DExD/H RNA helicase domain. As suggested by its structure, cumulative evidences documented that ectopic expression of mda-5 leads to growth inhibition and/or apoptosis in various cell lines. However, the signaling pathways involved in mda-5-mediated killing have not been elucidated. In this study, we utilized either genetically modified cloned rat embryo fibroblast cells overexpressing different functionally and structurally distinct oncogenes or human pancreatic and colorectal carcinoma cells containing mutant active ras to resolve the role of the Ras/Raf signaling pathway in mda-5-mediated growth inhibition/apoptosis induction. Rodent and human tumor cells containing constitutively activated Raf/Raf/MEK/ERK pathways were resistant to mda-5-induced killing and this protection was antagonized by intervening in this signal transduction cascade either by directly inhibiting ras activity using an antisense strategy or by targeting ras-downstream factors, such as MEK1/2, with the pharmacological inhibitor PD98059. The present findings provide a further example of potential cross-talk between growth-inhibitory and growth-promoting pathways in which the ultimate balance of these factors defines cellular homeostasis, leading to survival or induction of programmed cell death.
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Affiliation(s)
- L Lin
- Department of Pathology, Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, College of Physicians and Surgeons, New York, NY 10032, USA
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Roy BB, Hu J, Guo X, Russell RS, Guo F, Kleiman L, Liang C. Association of RNA helicase a with human immunodeficiency virus type 1 particles. J Biol Chem 2006; 281:12625-35. [PMID: 16527808 DOI: 10.1074/jbc.m510596200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RNA helicase A (RHA) belongs to the DEAH family of proteins that are capable of unwinding double-stranded RNA structure. In addition to its involvement in the metabolism of cellular RNA, RHA has been shown to stimulate RNA transcription from the long terminal repeat promoter of human immunodeficiency virus type 1 (HIV-1) as well as to enhance Rev/Rev response element-mediated gene expression. In this study, we provide evidence that RHA associates with HIV-1 Gag in an RNA-dependent manner. This interaction results in specific incorporation of RHA into HIV-1 particles. Knockdown of endogenous RHA in virus producer cells leads to generation of HIV-1 particles that are less infectious in part as a result of restricted reverse transcription. Therefore, RHA represents the first example of cellular RNA helicases that participate in HIV-1 particle production and promote viral reverse transcription.
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Affiliation(s)
- Bibhuti Bhusan Roy
- McGill AIDS Centre, Lady Davis Institute, Jewish General Hospital, Montreal, Quebec, Canada H3T 1E2
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21
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Li K, Chen Z, Kato N, Gale M, Lemon SM. Distinct poly(I-C) and virus-activated signaling pathways leading to interferon-beta production in hepatocytes. J Biol Chem 2005; 280:16739-47. [PMID: 15737993 DOI: 10.1074/jbc.m414139200] [Citation(s) in RCA: 290] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Innate cellular antiviral defenses are likely to influence the outcome of infections by many human viruses, including hepatitis B and C viruses, agents that frequently establish persistent infection leading to chronic hepatitis, cirrhosis, and liver cancer. However, little is known of the pathways by which hepatocytes, the cell type within which these hepatitis agents replicate, sense infection, and initiate protective responses. We show that cultured hepatoma cells, including Huh7 cells, do not activate the interferon (IFN)-beta promoter in response to extracellular poly(I-C). In contrast, the addition of poly(I-C) to culture media activates the IFN-beta promoter and results in robust expression of IFN-stimulated genes (ISG) in PH5CH8 cells, which are derived from non-neoplastic hepatocytes transformed with large T antigen. Small interfering RNA knockdown of TLR3 or its adaptor, Toll-interleukin-1 receptor domain-containing adaptor inducing IFN-beta (TRIF), blocked extracellular poly(I-C) signaling in PH5CH8 cells, whereas poly(I-C) responsiveness could be conferred on Huh7 hepatoma cells by ectopic expression of Toll-like receptor 3 (TLR3). In contrast to poly(I-C), both cell types signal the presence of Sendai virus infection through a TLR3-independent intracellular pathway requiring expression of retinoic acid-inducible gene I (RIG-I), a putative cellular RNA helicase. Silencing of RIG-I expression impaired only the response to Sendai virus and not extracellular poly(I-C). We conclude that hepatocytes contain two distinct antiviral signaling pathways leading to expression of type I IFNs, one dependent upon TLR3 and the other dependent on RIG-I, with little cross-talk between these pathways.
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Affiliation(s)
- Kui Li
- Department of Microbiology and Immunology, Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas 77555-1019, USA.
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Truong MJ, Delsart V, Bahr GM. Differentially expressed genes in HIV-1-infected macrophages following treatment with the virus-suppressive immunomodulator murabutide. Virus Res 2004; 99:25-33. [PMID: 14687943 DOI: 10.1016/j.virusres.2003.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The synthetic immunomodulator murabutide has been found to suppress human immunodeficiency virus type-1 (HIV-1) replication, in macrophages, through a regulated expression of cellular factors needed at different steps in the virus replication cycle. To identify cellular genes implicated in the murabutide-induced virus inhibition, we have carried out a differential display analysis on HIV-1-infected macrophages that were treated, or not, with murabutide. Sequencing of the differentially regulated cDNA bands and verification of the reproducibility of the murabutide effects, by reverse transcription-polymerase chain reaction or by Northern blotting, revealed an up-regulated expression of 21 genes and a down-regulation of seven others. The murabutide-regulated genes encoded proteins implicated in DNA binding, regulation of transcription, oxidative stress, metal binding, and other physiological functions. Six of the genes corresponded to unassigned/expressed sequence tags with yet unknown function. Among the genes which were up-regulated by murabutide and with established effects on inhibiting virus transcription, was the octamer binding factor 1 (Oct-1). We demonstrate the ability of murabutide to induce enhanced Oct-1 protein expression and DNA-binding activity in macrophages. Furthermore, our findings suggest the potential implication of additional transcription factors and metal-binding proteins in mediating the inhibitory effect of murabutide on virus transcription.
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Affiliation(s)
- Marie José Truong
- Laboratory of Molecular Immunology of Infection and Inflammation, Pasteur Institute in Lille, 1 Rue du Pr Calmette, BP 245, Lille Cedex 59019, France
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