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Faber GP, Nadav-Eliyahu S, Shav-Tal Y. Nuclear speckles - a driving force in gene expression. J Cell Sci 2022; 135:275909. [PMID: 35788677 DOI: 10.1242/jcs.259594] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Nuclear speckles are dynamic membraneless bodies located in the cell nucleus. They harbor RNAs and proteins, many of which are splicing factors, that together display complex biophysical properties dictating nuclear speckle formation and maintenance. Although these nuclear bodies were discovered decades ago, only recently has in-depth genomic analysis begun to unravel their essential functions in modulation of gene activity. Major advancements in genomic mapping techniques combined with microscopy approaches have enabled insights into the roles nuclear speckles may play in enhancing gene expression, and how gene positioning to specific nuclear landmarks can regulate gene expression and RNA processing. Some studies have drawn a link between nuclear speckles and disease. Certain maladies either involve nuclear speckles directly or dictate the localization and reorganization of many nuclear speckle factors. This is most striking during viral infection, as viruses alter the entire nuclear architecture and highjack host machinery. As discussed in this Review, nuclear speckles represent a fascinating target of study not only to reveal the links between gene positioning, genome subcompartments and gene activity, but also as a potential target for therapeutics.
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Affiliation(s)
- Gabriel P Faber
- The Mina and Everard Goodman Faculty of Life Sciences , Bar-Ilan University, Ramat Gan 5290002, Israel.,Institute of Nanotechnology , Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Shani Nadav-Eliyahu
- The Mina and Everard Goodman Faculty of Life Sciences , Bar-Ilan University, Ramat Gan 5290002, Israel.,Institute of Nanotechnology , Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Yaron Shav-Tal
- The Mina and Everard Goodman Faculty of Life Sciences , Bar-Ilan University, Ramat Gan 5290002, Israel.,Institute of Nanotechnology , Bar-Ilan University, Ramat Gan 5290002, Israel
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2
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Li K, Wang Z. Splicing factor SRSF2-centric gene regulation. Int J Biol Sci 2021; 17:1708-1715. [PMID: 33994855 PMCID: PMC8120470 DOI: 10.7150/ijbs.58888] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/04/2021] [Indexed: 01/14/2023] Open
Abstract
Serine/arginine-rich splicing factor 2 (SRSF2) is a splicing factor that is widely expressed in a variety of mammalian cell types. Increasing evidence has confirmed that SRSF2 plays vital roles in a number of biological and pathological processes. Therefore, it is important to understand how its expression is regulated, and how it regulates the expression of its target genes. Recently, we found that SRSF2 expression could be upregulated by herpes simplex virus-1 (HSV-1) infection, and that altered SRSF2 expression, in turn, epigenetically regulates the transcription of HSV-1 genes. Further studies on T cell exhaustion demonstrated that upregulated SRSF2 in exhausted T cells elevated the levels of multiple immune checkpoint molecules by associating with the acyl-transferases, P300 and CBP, and by altering histone modification near the transcription start sites of these genes, thereby influencing signal transducer and activator of transcription 3 binding to these gene promoters. These findings suggest that SRSF2 acts as an important sensor and effector during disease progression. Here, we discuss the molecules that regulate SRSF2 gene expression and their associated mechanisms, and the mechanisms via which SRSF2 regulates the expression of target genes, thus providing novel insights into the central role of SRSF2 in gene regulation.
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Affiliation(s)
- Kun Li
- Department of Nuclear Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan 250014, China
| | - Ziqiang Wang
- Department of Nuclear Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan 250014, China.,Biomedical Sciences College & Shandong Medicinal Biotechnology Centre, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250062, China
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3
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Rensen E, Mueller F, Scoca V, Parmar JJ, Souque P, Zimmer C, Di Nunzio F. Clustering and reverse transcription of HIV-1 genomes in nuclear niches of macrophages. EMBO J 2021; 40:e105247. [PMID: 33270250 PMCID: PMC7780146 DOI: 10.15252/embj.2020105247] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 10/04/2020] [Accepted: 10/16/2020] [Indexed: 01/07/2023] Open
Abstract
In order to replicate, human immunodeficiency virus (HIV-1) reverse-transcribes its RNA genome into DNA, which subsequently integrates into host cell chromosomes. These two key events of the viral life cycle are commonly viewed as separate not only in time, but also in cellular space, since reverse transcription (RT) is thought to be completed in the cytoplasm before nuclear import and integration. However, the spatiotemporal organization of the early viral replication cycle in macrophages, the natural non-dividing target cells that constitute reservoirs of HIV-1 and an obstacle to curing AIDS, remains unclear. Here, we demonstrate that infected macrophages display large nuclear foci of viral DNA (vDNA) and viral RNA, in which multiple viral genomes cluster together. These clusters form in the absence of chromosomal integration, sequester the paraspeckle protein CPSF6, and localize to nuclear speckles. Surprisingly, these viral RNA clusters consist mostly of genomic, incoming RNA, both in cells where reverse transcription is pharmacologically suppressed and in untreated cells. We demonstrate that following temporary inhibition, reverse transcription can resume in the nucleus and lead to vDNA accumulation in these clusters. We further show that nuclear reverse transcription can result in transcription-competent viral DNA. These findings change our understanding of the early HIV-1 replication cycle and may have implications for addressing HIV-1 persistence.
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Affiliation(s)
- Elena Rensen
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Florian Mueller
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
| | - Viviana Scoca
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Jyotsana J Parmar
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
| | - Philippe Souque
- Molecular Virology and VaccinologyInstitut PasteurParisFrance
| | - Christophe Zimmer
- Imaging and Modeling UnitInstitut PasteurUMR 3691 CNRSC3BI USR 3756 IP CNRSParisFrance
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4
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Wang Z, Liu Q, Lu J, Fan P, Xie W, Qiu W, Wang F, Hu G, Zhang Y. Serine/Arginine-rich Splicing Factor 2 Modulates Herpes Simplex Virus Type 1 Replication via Regulating Viral Gene Transcriptional Activity and Pre-mRNA Splicing. J Biol Chem 2016; 291:26377-26387. [PMID: 27784784 DOI: 10.1074/jbc.m116.753046] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/17/2016] [Indexed: 11/06/2022] Open
Abstract
Once it enters the host cell, herpes simplex virus type 1 (HSV-1) recruits a series of host cell factors to facilitate its life cycle. Here, we demonstrate that serine/arginine-rich splicing factor 2 (SRSF2), which is an important component of the splicing speckle, mediates HSV-1 replication by regulating viral gene expression at the transcriptional and posttranscriptional levels. Our results indicate that SRSF2 functions as a transcriptional activator by directly binding to infected cell polypeptide 0 (ICP0), infected cell polypeptide 27 (ICP27), and thymidine kinase promoters. Moreover, SRSF2 participates in ICP0 pre-mRNA splicing by recognizing binding sites in ICP0 exon 3. These findings provide insight into the functions of SRSF2 in HSV-1 replication and gene expression.
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Affiliation(s)
- Ziqiang Wang
- From the School of Life Sciences, Tsinghua University, Beijing 100084, China.,the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Qing Liu
- From the School of Life Sciences, Tsinghua University, Beijing 100084, China.,the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Jinhua Lu
- Shenzhen South China Pharmaceutical Co., Ltd., Shenzhen 518055, China, and
| | - Ping Fan
- From the School of Life Sciences, Tsinghua University, Beijing 100084, China.,the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Weidong Xie
- the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Wei Qiu
- From the School of Life Sciences, Tsinghua University, Beijing 100084, China.,the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Fan Wang
- From the School of Life Sciences, Tsinghua University, Beijing 100084, China.,the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
| | - Guangnan Hu
- the Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01655
| | - Yaou Zhang
- the Key Lab in Healthy Science and Technology, Division of Life Science, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China,
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5
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Nkeze J, Li L, Benko Z, Li G, Zhao RY. Molecular characterization of HIV-1 genome in fission yeast Schizosaccharomyces pombe. Cell Biosci 2015; 5:47. [PMID: 26309721 PMCID: PMC4549081 DOI: 10.1186/s13578-015-0037-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 07/27/2015] [Indexed: 11/25/2022] Open
Abstract
Background The human immunodeficiency virus type 1 (HIV-1) genome (~9 kb RNA) is flanked by two long terminal repeats (LTR) promoter regions with nine open reading frames, which encode Gag, Pol and Env polyproteins, four accessory proteins (Vpu, Vif, Vpr, Nef) and two regulatory proteins (Rev, Tat). In this study, we carried out a genome-wide and functional analysis of the HIV-1 genome in fission yeast (Schizosaccharomyces pombe). Results Each one of the HIV-1 genes was cloned and expressed individually in fission yeast. Subcellular localization of each viral protein was first examined. The effect of protein expression on cellular proliferation and colony formations, an indication of cytotoxicity, were observed. Overall, there is a general correlation of subcellular localization of each viral protein between fission yeast and mammalian cells. Three viral proteins, viral protein R (Vpr), protease (PR) and regulator of expression of viral protein (Rev), were found to inhibit cellular proliferation. Rev was chosen for further analysis in fission yeast and mammalian cells. Consistent with the observation in fission yeast, expression of HIV-1 rev gene also caused growth retardation in mammalian cells. However, the observed growth delay was neither due to the cytotoxic effect nor due to alterations in cell cycling. Mechanistic testing of the Rev effect suggests it triggers transient induction of cellular oxidative stress. Conclusions Some of the behavioral and functional similarities of Rev between fission yeast and mammalian cells suggest fission yeast might be a useful model system for further studies of molecular functions of Rev and other HIV-1 viral proteins.
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Affiliation(s)
- Joseph Nkeze
- Division of Molecular Pathology, Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA
| | - Lin Li
- Division of Molecular Pathology, Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA.,AIDS Research Department, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071 China
| | - Zsigmond Benko
- Division of Molecular Pathology, Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA.,Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Ge Li
- Division of Molecular Pathology, Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA
| | - Richard Y Zhao
- Division of Molecular Pathology, Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA.,Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA.,Institute of Human Virology, University of Maryland School of Medicine, Baltimore, MD 21201-1192 USA
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6
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Kula A, Marcello A. Dynamic Post-Transcriptional Regulation of HIV-1 Gene Expression. BIOLOGY 2012; 1:116-33. [PMID: 24832221 PMCID: PMC4009772 DOI: 10.3390/biology1020116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 06/15/2012] [Accepted: 06/18/2012] [Indexed: 01/08/2023]
Abstract
Gene expression of the human immunodeficiency virus type 1 (HIV-1) is a highly regulated process. Basal transcription of the integrated provirus generates early transcripts that encode for the viral products Tat and Rev. Tat promotes the elongation of RNA polymerase while Rev mediates the nuclear export of viral RNAs that contain the Rev-responsive RNA element (RRE). These RNAs are exported from the nucleus to allow expression of Gag-Pol and Env proteins and for the production of full-length genomic RNAs. A balance exists between completely processed mRNAs and RRE-containing RNAs. Rev functions as an adaptor that recruits cellular factors to re-direct singly spliced and unspliced viral RNAs to nuclear export. The aim of this review is to address the dynamic regulation of this post-transcriptional pathway in light of recent findings that implicate several novel cellular cofactors of Rev function.
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Affiliation(s)
- Anna Kula
- Laboratory of Molecular Virology, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano, Trieste 99 34012, Italy.
| | - Alessandro Marcello
- Laboratory of Molecular Virology, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano, Trieste 99 34012, Italy.
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7
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Stably integrated and expressed retroviral sequences can influence nuclear location and chromatin condensation of the integration locus. Chromosoma 2012; 121:353-67. [PMID: 22415776 PMCID: PMC3401306 DOI: 10.1007/s00412-012-0366-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 02/27/2012] [Accepted: 02/27/2012] [Indexed: 12/24/2022]
Abstract
The large-scale chromatin organization of retrovirus and retroviral gene vector integration loci has attracted little attention so far. We compared the nuclear organization of transcribed integration loci with the corresponding loci on the homologous chromosomes. Loci containing gamma-retroviral gene transfer vectors in mouse hematopoietic precursor cells showed small but significant repositioning of the integration loci towards the nuclear interior. HIV integration loci in human cells showed a significant repositioning towards the nuclear interior in two out of five cases. Notably, repositioned HIV integration loci also showed chromatin decondensation. Transcriptional activation of HIV by sodium butyrate treatment did not lead to a further enhancement of the differences between integration and homologous loci. The positioning relative to splicing speckles was indistinguishable for integration and homologous control loci. Our data show that stable retroviral integration can lead to alterations of the nuclear chromatin organization, and has the potential to modulate chromatin structure of the host cell. We thus present an example where a few kb of exogenous DNA are sufficient to significantly alter the large-scale chromatin organization of an endogenous locus.
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8
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Choi EA, Hope TJ. Mutational analysis of bovine leukemia virus Rex: identification of a dominant-negative inhibitor. J Virol 2005; 79:7172-81. [PMID: 15890956 PMCID: PMC1112096 DOI: 10.1128/jvi.79.11.7172-7181.2005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rex proteins of the delta-retroviruses act to facilitate the export of intron-containing viral RNAs. The Rex of bovine leukemia virus (BLV) is poorly characterized. To gain a better understanding of BLV Rex, we generated a reporter assay to measure BLV Rex function and used it to screen a series of point and deletion mutations. Using this approach, we were able to identify the nuclear export signal of BLV Rex. Further, we identified a dominant-negative form of BLV Rex. Protein localization analysis revealed that wild-type BLV Rex had a punctate nuclear localization and was associated with nuclear pores. In contrast, the dominant-negative BLV Rex mutation had a diffuse nuclear localization and no nuclear pore association. Overexpression of the dominant-negative BLV Rex altered the localization of the wild-type protein. This dominant-negative derivative of BLV Rex could be a useful tool to test the concept of intracellular immunization against viral infection in a large animal model.
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MESH Headings
- Active Transport, Cell Nucleus
- Amino Acid Sequence
- Animals
- Base Sequence
- Cattle
- Cell Line
- DNA, Viral/genetics
- Gene Products, rex/antagonists & inhibitors
- Gene Products, rex/genetics
- Gene Products, rex/physiology
- Genes, Reporter
- Genes, Viral
- HeLa Cells
- Humans
- Leukemia Virus, Bovine/genetics
- Leukemia Virus, Bovine/pathogenicity
- Leukemia Virus, Bovine/physiology
- Molecular Sequence Data
- Mutation
- Point Mutation
- Sequence Deletion
- Sequence Homology, Amino Acid
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Affiliation(s)
- Eun-A Choi
- Department of Microbiology and Immunology, University of Illinois at Chicago, 835 S. Wolcott, Chicago, IL 60612, USA
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9
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Ersvaer E, Bertelsen LT, Espenes LC, Bredholt T, Bøe SO, Iversen BM, Bruserud Ø, Ulvestad E, Gjertsen BT. Characterization of Ribosomal P Autoantibodies in Relation to Cell Destruction and Autoimmune Disease. Scand J Immunol 2004; 60:189-98. [PMID: 15238089 DOI: 10.1111/j.0300-9475.2004.01450.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Autoantibodies against the ribosomal P proteins are related to cell death and tissue destruction and are frequently exhibited in patients with systemic lupus erythematosus (SLE). In an attempt to explore the effect of tissue destruction on the induction of anti-P autoantibodies, we searched for anti-P autoantibodies by enzyme-linked immunosorbent assay in 201 antinuclear antibody (ANA)-positive individuals, in 10 patients with treated kidney SLE and in 45 acute leukaemia patients undergoing intensive chemotherapy. The autoantibody reactivity was further characterized using one- and two-dimensional immunoblot analysis and immunofluorescence. Anti-P were detected in 5.5% (11/201) of ANA-positive individuals, but not in kidney-affected SLE patients or in patients with leukaemia. Seven of 11 anti-P-positive patients had SLE (3/11), primary Sjögrens's syndrome (1/11) and other autoimmune diseases (3/11). A relation between disease activity and anti-P was suggested by follow-up examinations in one SLE patient, supported by the absence of anti-P autoantibodies in the 10 treated kidney SLE patients. Anti-P autoantibodies were detected by immunoblot in one patient with SLE indicating anti-P2 predominance and in the patient with Sjögrens's syndrome indicating anti-P1 predominance. Diverging humoral responses in these ANA- and anti-P-positive patients were further illustrated by immunofluorescence, elucidating varying nuclear reactivity and anti-P pattern. The observation of anti-P in individuals with active autoimmune disease, but not in patients with chemotherapy-induced cell damage, suggests that anti-P antibodies are part of a specific disease process, and not elicited as a response to cell destruction per se.
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Affiliation(s)
- E Ersvaer
- Institute of Medicine and Department of Internal Medicine, Hematology Section, University of Bergen, Haukeland University Hospital, N-5021 Bergen, Norway
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10
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Marcello A, Lusic M, Pegoraro G, Pellegrini V, Beltram F, Giacca M. Nuclear organization and the control of HIV-1 transcription. Gene 2004; 326:1-11. [PMID: 14729258 DOI: 10.1016/j.gene.2003.10.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The regulation of transcription of the human immunodeficiency virus (HIV) is a complex event of significant pathological relevance, which recapitulates general concepts of cellular transcription with some peculiarities. The viral promoter is embedded in a chromatin structure that exerts powerful repression on transcription; activation of gene expression relies on the combined activity of a series of cellular factors that respond to different external stimuli, and on the function of a single viral regulatory protein, the Tat transactivator. Transcriptional activation is consequent to both chromatin remodeling and to the recruitment of elongation-competent RNA polymerase II complexes onto the integrated promoter, two events that require the coordinate, but transient, assembly of different protein complexes. Application of optical imaging techniques now allows us to appreciate the spatial and temporal evolvement of these reactions in vivo. The picture that is emerging is not only descriptive, but also relevant to the understanding of the regulation of the process. In particular, it appears that the confinement of biomolecules within specific subcellular compartments represents a way to control and coordinate the assembly of functional complexes that regulate viral gene expression.
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Affiliation(s)
- Alessandro Marcello
- Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology, Area Science Park, Padriciano 99, 34012 Trieste, Italy
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11
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Cmarko D, Bøe SO, Scassellati C, Szilvay AM, Davanger S, Fu XD, Haukenes G, Kalland KH, Fakan S. Rev inhibition strongly affects intracellular distribution of human immunodeficiency virus type 1 RNAs. J Virol 2002; 76:10473-84. [PMID: 12239324 PMCID: PMC136536 DOI: 10.1128/jvi.76.20.10473-10484.2002] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2002] [Accepted: 06/27/2002] [Indexed: 11/20/2022] Open
Abstract
To define the human immunodeficiency virus type 1 (HIV-1) RNA maturation pathways, we analyzed the intracellular distribution of HIV-1 RNA and the viral regulatory proteins Rev and Tat in transfected COS cells and HIV-1-infected lymphoid C8166 cells by means of ultrastructural in situ hybridization using antisense RNA probes and immunoelectron microscopy. The intranuclear viral RNA occurs in ribonucleoprotein fibrils in the perichromatin and interchromatin regions. The simultaneous demonstration of Rev, Tat, Br-labeled RNA, and cellular proteins SC35 and CRM1 in such fibrils reveals the potential of Rev to associate with nascent HIV pre-mRNA and its splicing complex and transport machinery. In a rev-minus system, the env intron-containing, incompletely spliced viral RNAs are revealed only in the nucleus, indicating that Rev is required to initiate the transport to the cytoplasm. Moreover, env intron sequences frequently occur in the periphery of interchromatin granule clusters, while the probe containing the rev exon sequence does not associate with this nucleoplasmic domain. When cells were treated with the CRM1 inhibitor leptomycin B in the presence of Rev protein, the env intron containing HIV RNAs formed clusters throughout the nucleoplasm and accumulated at the nuclear pores. This suggests that Rev is necessary and probably also sufficient for the accumulation of incompletely spliced HIV RNAs at the nuclear pores while CRM1 is needed for translocation across the nuclear pore complex.
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MESH Headings
- Active Transport, Cell Nucleus
- Animals
- COS Cells
- Cell Nucleus/metabolism
- Chlorocebus aethiops
- Exons
- Gene Products, rev/genetics
- Gene Products, rev/metabolism
- Gene Products, tat/genetics
- Genes, env
- HIV-1/genetics
- Humans
- Intracellular Fluid/metabolism
- Introns
- Karyopherins/metabolism
- Nuclear Proteins/metabolism
- Plasmids
- RNA Splicing
- RNA, Messenger
- RNA, Viral/metabolism
- Receptors, Cytoplasmic and Nuclear
- Ribonucleoproteins
- Serine-Arginine Splicing Factors
- Transfection
- Virion
- rev Gene Products, Human Immunodeficiency Virus
- tat Gene Products, Human Immunodeficiency Virus
- Exportin 1 Protein
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Affiliation(s)
- Dusan Cmarko
- Centre of Electron Microscopy, University of Lausanne, 27 Bugnon, CH-1005 Lausanne, Switzerland
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12
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Affiliation(s)
- A Michienzi
- Molecular Biology Department, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
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13
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Bell P, Montaner LJ, Maul GG. Accumulation and intranuclear distribution of unintegrated human immunodeficiency virus type 1 DNA. J Virol 2001; 75:7683-91. [PMID: 11462040 PMCID: PMC115003 DOI: 10.1128/jvi.75.16.7683-7691.2001] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2001] [Accepted: 05/09/2001] [Indexed: 12/12/2022] Open
Abstract
The RNA genome of human immunodeficiency virus type 1 (HIV-1) is converted into DNA after infection in order to integrate into the host cell DNA. However, a large number of these reverse-transcribed genomes remain unintegrated in the nucleus of infected cells. Currently, there are no data available about the intranuclear distribution pattern of unintegrated HIV-1 DNA in relation to nuclear structures as observed on the single-cell level. In the present study, we investigated the intranuclear fate of unintegrated viral DNA in cell lines expressing CD4 and coreceptors (HOS-CD4.CCR5 and U373-MAGI-CXCR4(CEM)) infected with HIV-1 (strain 89.6). We used a novel approach to distinguish in situ unintegrated from integrated viral DNA by performing fluorescent in situ hybridization on cells in which stress-induced chromosome condensation had been induced, a procedure that contracts chromosomes independent of the cell cycle. Cells infected for 15 h accumulated large amounts of HIV-1 DNA which was located between the condensed chromosome strands, allowing the identification of this viral DNA as unintegrated. In contrast, in HeLa/LAV, a cell line carrying integrated HIV-1 genomes, the great majority of viral DNA colocalized with the cellular DNA. We show that unintegrated HIV-1 DNA does not evenly distribute within the host cell nucleus but tends to aggregate into clusters containing many copies of the viral genomes. The formation of these DNA clusters was independent of viral DNA replication and thus appeared to result solely from multiple infections. The DNA aggregates remained in the nuclei of infected cells for at least 25 h after the infection was stopped. The emergence of transcription sites, which most likely denote sites of the integrated provirus, lagged clearly behind the accumulation of viral DNA. These transcription foci could not be linked to unintegrated DNA molecules, suggesting that this DNA type is unable to transcribe, at least at levels comparable to those of integrated DNA. Neither unintegrated HIV-1 DNA nor transcription foci nor integrated DNA was observed to associate with nuclear domain 10 (ND10), a nuclear structure known to represent the site where several DNA viruses replicate and transcribe. Also, HIV-1 does not modify ND10 at early or late times of infection. There was no specific association of HIV-1 transcripts with splicing factor SC35 domains, in contrast to what has been reported for a number of both cellular and viral genes. Surprisingly, unintegrated HIV-1 DNA was found to accumulate within or in close association with SC35 domains, demonstrating a specific distribution of the viral DNA within the host cell nucleus. Taken together, our results demonstrate that unintegrated proviral HIV-1 DNA does not randomly localize within infected cells but preferentially aggregates in the nucleus within SC35 domains.
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Affiliation(s)
- P Bell
- The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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14
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Hauber J. Nuclear export mediated by the Rev/Rex class of retroviral Trans-activator proteins. Curr Top Microbiol Immunol 2001; 259:55-76. [PMID: 11417127 DOI: 10.1007/978-3-642-56597-7_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Affiliation(s)
- J Hauber
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg, Schlossgarten 4, 91054 Erlangen, Germany
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15
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Gjerdrum C, Stranda A, Szilvay AM. Functional role of the HIV-1 Rev exon 1 encoded region in complex formation and trans-dominant inhibition. FEBS Lett 2001; 495:106-10. [PMID: 11322956 DOI: 10.1016/s0014-5793(01)02364-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
To study functional aspects of the exon 1 encoded region of the human immunodeficiency virus type 1 Rev protein, the viral Tev protein which exhibits low Rev activity but lacks the rev exon 1 encoded region was examined. Neither Rev-Tev heteromer complex formation nor inhibition of Rev by an export deficient Tev mutant was observed. Insertion of the rev exon 1 encoded region into the Tev mutant allowed it to oligomerize with Rev and act as a trans-dominant negative mutant. This showed that the exon 1 encoded region of Rev is essential for oligomerization and that oligomerization is a prerequisite for trans-dominant inhibition.
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Affiliation(s)
- C Gjerdrum
- Department of Molecular Biology, University of Bergen, HIB, P.O. Box 7800, N-5020, Bergen, Norway
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16
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D'Agostino DM, Ferro T, Zotti L, Meggio F, Pinna LA, Chieco-Bianchi L, Ciminale V. Identification of a domain in human immunodeficiency virus type 1 rev that is required for functional activity and modulates association with subnuclear compartments containing splicing factor SC35. J Virol 2000; 74:11899-910. [PMID: 11090190 PMCID: PMC112473 DOI: 10.1128/jvi.74.24.11899-11910.2000] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2000] [Accepted: 09/15/2000] [Indexed: 11/20/2022] Open
Abstract
The activity of human immunodeficiency virus Rev as a regulator of viral mRNA expression is tightly linked to its ability to shuttle between the nucleus and cytoplasm; these properties are conferred by a leucine-rich nuclear export signal (NES) and by an arginine-rich nuclear localization signal/RNA binding domain (NLS/RBD) required for binding to the Rev-responsive element (RRE) located on viral unspliced and singly spliced mRNAs. Structure predictions and biophysical measurements indicate that Rev consists of an unstructured region followed by a helix-loop-helix motif containing the NLS/RBD and sequences directing multimerization and by a carboxy-terminal tail containing the NES. We present evidence that the loop portion of the helix-loop-helix region is an essential functional determinant that is required for binding to the RRE and for correct intracellular routing. Data obtained using a protein kinase CK2 phosphorylation assay indicated that the loop region is essential for juxtaposition of helices 1 and 2 and phosphorylation by protein kinase CK2. Deletion of the loop resulted in partial accumulation of Rev in SC35-positive nuclear bodies that resembled nuclear bodies that form in response to inhibition of transcription. Accumulation of the DeltaLoop mutant in nuclear bodies depended on the presence of an intact NES, suggesting that both the loop and the NES play a role in controlling intranuclear compartmentalization of Rev and its association with splicing factors.
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Affiliation(s)
- D M D'Agostino
- Dipartimento di Scienze Oncologiche e Chirurgiche, Sezione di Oncologia, University of Padova, Italy.
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17
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Michienzi A, Cagnon L, Bahner I, Rossi JJ. Ribozyme-mediated inhibition of HIV 1 suggests nucleolar trafficking of HIV-1 RNA. Proc Natl Acad Sci U S A 2000; 97:8955-60. [PMID: 10922055 PMCID: PMC16803 DOI: 10.1073/pnas.97.16.8955] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The HIV regulatory proteins Tat and Rev have a nucleolar localization property in human cells. However, no functional role has been attributed to this localization. Recently it has been demonstrated that expression of Rev induces nucleolar relocalization of some protein factors involved in Rev export. Because the function of Rev is to bind HIV RNA and facilitate transport of singly spliced and unspliced RNA to the cytoplasm, it is likely that the nucleolus plays a critical role in HIV-1 RNA export. As a test for trafficking of HIV-1 RNAs into the nucleolus, a hammerhead ribozyme that specifically cleaves HIV-1 RNA was inserted into the body of the U16 small nucleolar RNA, resulting in accumulation of the ribozyme within the nucleoli of human cells. HeLa CD4(+) and T cells expressing this nucleolar localized ribozyme exhibit dramatically suppressed HIV-1 replication. The results presented here suggest a trafficking of HIV-1 RNA through the nucleoli of human cells, thus posing a different paradigm for lentiviral RNA processing.
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Affiliation(s)
- A Michienzi
- Department of Molecular Biology, Beckman Research Institute of the City of Hope, and Graduate School of Biological Sciences, City of Hope, Duarte, CA 91010-3011, USA
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18
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Watts NR, Sackett DL, Ward RD, Miller MW, Wingfield PT, Stahl SS, Steven AC. HIV-1 rev depolymerizes microtubules to form stable bilayered rings. J Cell Biol 2000; 150:349-60. [PMID: 10908577 PMCID: PMC2180222 DOI: 10.1083/jcb.150.2.349] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We describe a novel interaction between HIV-1 Rev and microtubules (MTs) that results in the formation of bilayered rings that are 44-49 nm in external diameter, 3.4-4.2 MD (megadaltons) in mass, and have 28-, 30-, or 32-fold symmetry. Ring formation is not sensitive to taxol, colchicine, or microtubule-associated proteins, but requires Mg(2+) and is inhibited by maytansine. The interaction involves the NH(2)-terminal domain of Rev and the face of tubulin exposed on the exterior of the MTs. The NH(2)-terminal half of Rev has unexpected sequence similarity to the tubulin-binding portion of the catalytic/motor domains of the microtubule-destabilizing Kin I kinesins. We propose a model wherein binding of Rev dimers to MTs at their ends causes segments of two neighboring protofilaments to peel off and close into rings, circumferentially containing 14, 15, or 16 tubulin heterodimers, with Rev bound on the inside. Rev has a strong inhibitory effect on aster formation in Xenopus egg extracts, demonstrating that it can interact with tubulin in the presence of normal levels of cellular constituents. These results suggest that Rev may interact with MTs to induce their destabilization, a proposition consistent with the previously described disruption of MTs after HIV-1 infection.
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Affiliation(s)
- Norman R. Watts
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases
| | - Dan L. Sackett
- Laboratory of Integrative and Medical Biophysics, National Institute of Child Health and Human Development
| | - Rita D. Ward
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Mill W. Miller
- Department of Biological Sciences, Wright State University, Dayton, Ohio 45435
| | - Paul T. Wingfield
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases
| | - Stephen S. Stahl
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases
| | - Alasdair C. Steven
- Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases
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19
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Szilvay AM, Bøe SO, Kalland KH. Co-expression of a trans-dominant negative mutant of the human immunodeficiency virus type 1 (HIV-1) Rev protein affects the Rev-dependent splicing pattern and expression of HIV-1 RNAs. J Gen Virol 1999; 80 ( Pt 8):1965-1974. [PMID: 10466792 DOI: 10.1099/0022-1317-80-8-1965] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Trans-dominant negative mutants of the human immunodeficiency virus type 1 (HIV-1) regulatory protein Rev inhibit the function of wild-type Rev in a dose-dependent manner. This was previously shown to be caused by nuclear retention of the wild-type protein. In the present work, further analysis of the trans-dominant negative effect was performed using cotransfection experiments with different constructs encoding HIV-1 Rev and viral structural proteins together with a plasmid encoding a trans-dominant negative Rev mutant. Thus, one species of pre-mRNA was transcribed from the reporter plasmids. This pre-mRNA was then either spliced or exported by Rev as unspliced RNA for translation of the HIV structural proteins. An immunofluorescence assay and Western blot analysis were used for analysis of protein expression. In situ hybridization was applied for labelling of unspliced mRNA in transfected cells, and RNase protection analysis was used to determine the relative amount of unspliced versus spliced mRNAs. The experiments confirmed that the transdominant negative mutant inhibited nuclear export of unspliced mRNA. It was, in addition, demonstrated for the first time that the trans-dominant negative mutant also affected a Rev-dependent regulatory step connected with viral pre-mRNA splicing. As a consequence, proteins expressed from unspliced and singly spliced HIV mRNAs decreased while there was an increase in protein products encoded by spliced and alternatively spliced mRNAs.
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Affiliation(s)
- Anne Marie Szilvay
- Department of Molecular Biology1 and Centre for Research in Virology, Department of Microbiology and Immunology2, The Gade Institute, University of Bergen, HIB, Post-box 7800, N-5020 Bergen, Norway
| | - Stig-Ove Bøe
- Department of Molecular Biology1 and Centre for Research in Virology, Department of Microbiology and Immunology2, The Gade Institute, University of Bergen, HIB, Post-box 7800, N-5020 Bergen, Norway
| | - Karl-Henning Kalland
- Department of Molecular Biology1 and Centre for Research in Virology, Department of Microbiology and Immunology2, The Gade Institute, University of Bergen, HIB, Post-box 7800, N-5020 Bergen, Norway
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20
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Favaro JP, Borg KT, Arrigo SJ, Schmidt MG. Effect of Rev on the intranuclear localization of HIV-1 unspliced RNA. Virology 1998; 249:286-96. [PMID: 9791020 DOI: 10.1006/viro.1998.9312] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) Rev is a 19-kDa regulatory protein which binds to unspliced and partially spliced HIV-1 RNAs. Export, splicing, stability, and translation of HIV-1 RNAs are influenced by Rev. To further understand the effect of Rev on HIV-1 RNA splicing, the intranuclear localization of unspliced HIV-1 RNA and a cellular splicing factor was examined in the presence and absence of Rev. Splicing component-35 (SC-35) is an essential SR protein splicing factor which localizes into 20-40 nuclear granules (Fu, X. D., and Maniatis, T. Nature 343 (6257), 437-441, 1990). Laser scanning confocal microscopy was utilized to examine the colocalization of unspliced HIV-1 RNA and SC-35-containing granules. In the presence of Rev, many of the SC-35-containing granules were colocalized on their edges or completely colocalized with HIV-1 unspliced RNA speckles. In the absence of Rev, however, little colocalization of the unspliced HIV-1 RNA speckles and the SC-35-containing granules was observed. Quantitative RT-PCR was utilized to examine the effect of Rev on the level of fully spliced HIV-1 RNA. In the presence of Rev, a decrease in the level of fully spliced HIV-1 RNA was observed. Thus both the intranuclear localization and posttranscriptional processing of HIV-1 unspliced RNA are affected by Rev.
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Affiliation(s)
- J P Favaro
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina, 29425-2230, USA
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