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Plant E, Bellefroid M, Van Lint C. A complex network of transcription factors and epigenetic regulators involved in bovine leukemia virus transcriptional regulation. Retrovirology 2023; 20:11. [PMID: 37268923 DOI: 10.1186/s12977-023-00623-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Accepted: 05/09/2023] [Indexed: 06/04/2023] Open
Abstract
Bovine Leukemia Virus (BLV) is the etiological agent of enzootic bovine leukosis, a disease characterized by the neoplastic proliferation of B cells in cattle. While most European countries have introduced efficient eradication programs, BLV is still present worldwide and no treatment is available. A major feature of BLV infection is the viral latency, which enables the escape from the host immune system, the maintenance of a persistent infection and ultimately the tumoral development. BLV latency is a multifactorial phenomenon resulting in the silencing of viral genes due to genetic and epigenetic repressions of the viral promoter located in the 5' Long Terminal Repeat (5'LTR). However, viral miRNAs and antisense transcripts are expressed from two different proviral regions, respectively the miRNA cluster and the 3'LTR. These latter transcripts are expressed despite the viral latency affecting the 5'LTR and are increasingly considered to take part in tumoral development. In the present review, we provide a summary of the experimental evidence that has enabled to characterize the molecular mechanisms regulating each of the three BLV transcriptional units, either through cis-regulatory elements or through epigenetic modifications. Additionally, we describe the recently identified BLV miRNAs and antisense transcripts and their implications in BLV-induced tumorigenesis. Finally, we discuss the relevance of BLV as an experimental model for the closely related human T-lymphotropic virus HTLV-1.
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Affiliation(s)
- Estelle Plant
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), 6041, Gosselies, Belgium
| | - Maxime Bellefroid
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), 6041, Gosselies, Belgium
| | - Carine Van Lint
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), 6041, Gosselies, Belgium.
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Bellefroid M, Rodari A, Galais M, Krijger PHL, Tjalsma SJD, Nestola L, Plant E, Vos ESM, Cristinelli S, Van Driessche B, Vanhulle C, Ait-Ammar A, Burny A, Ciuffi A, de Laat W, Van Lint C. Role of the cellular factor CTCF in the regulation of bovine leukemia virus latency and three-dimensional chromatin organization. Nucleic Acids Res 2022; 50:3190-3202. [PMID: 35234910 PMCID: PMC8989512 DOI: 10.1093/nar/gkac107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 01/31/2022] [Accepted: 02/05/2022] [Indexed: 01/12/2023] Open
Abstract
Bovine leukemia virus (BLV)-induced tumoral development is a multifactorial phenomenon that remains incompletely understood. Here, we highlight the critical role of the cellular CCCTC-binding factor (CTCF) both in the regulation of BLV transcriptional activities and in the deregulation of the three-dimensional (3D) chromatin architecture surrounding the BLV integration site. We demonstrated the in vivo recruitment of CTCF to three conserved CTCF binding motifs along the provirus. Next, we showed that CTCF localized to regions of transitions in the histone modifications profile along the BLV genome and that it is implicated in the repression of the 5′Long Terminal Repeat (LTR) promoter activity, thereby contributing to viral latency, while favoring the 3′LTR promoter activity. Finally, we demonstrated that BLV integration deregulated the host cellular 3D chromatin organization through the formation of viral/host chromatin loops. Altogether, our results highlight CTCF as a new critical effector of BLV transcriptional regulation and BLV-induced physiopathology.
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Affiliation(s)
- Maxime Bellefroid
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Anthony Rodari
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Mathilde Galais
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Peter H L Krijger
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht 3584, CT, The Netherlands
| | - Sjoerd J D Tjalsma
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht 3584, CT, The Netherlands
| | - Lorena Nestola
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Estelle Plant
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Erica S M Vos
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht 3584, CT, The Netherlands
| | - Sara Cristinelli
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Lausanne 1011, Switzerland
| | - Benoit Van Driessche
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Caroline Vanhulle
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Amina Ait-Ammar
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Arsène Burny
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
| | - Angela Ciuffi
- Institute of Microbiology, Lausanne University Hospital, University of Lausanne, Lausanne 1011, Switzerland
| | - Wouter de Laat
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht 3584, CT, The Netherlands
| | - Carine Van Lint
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies 6041, Belgium
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Murakami H, Murakami-Kawai M, Kamisuki S, Hisanobu S, Tsurukawa Y, Uchiyama J, Sakaguchi M, Tsukamoto K. Specific antiviral effect of violaceoid E on bovine leukemia virus. Virology 2021; 562:1-8. [PMID: 34242747 DOI: 10.1016/j.virol.2021.06.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 06/28/2021] [Accepted: 06/29/2021] [Indexed: 11/28/2022]
Abstract
Bovine leukemia virus (BLV) infection has spread worldwide causing significant economic losses in the livestock industry. In countries with a high prevalence of BLV, minimizing economic losses is challenging; thus, research into various countermeasures is important for improving BLV control. Because anti-BLV drugs have not been developed, the present study explored a promising chemical compound with anti-BLV activity. Initially, screening of a chemical compound library revealed that violaceoid E (vioE), which is isolated from fungus, showed antiviral activity. Further analysis demonstrated that the antiviral effect of vioE inhibited transcriptional activation of BLV. Cellular thermal shift assay and pulldown assays provided evidence for a direct interaction between vioE and the viral transactivator protein, Tax. These data indicate that interference with Tax-dependent transcription could be a novel target for development of anti-BLV drugs. Therefore, it is suggested that vioE is a novel antiviral compound against BLV.
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Affiliation(s)
- Hironobu Murakami
- Laboratory of Animal Health II, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan; Center for Human and Animal Symbiosis Science, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan.
| | - Makoto Murakami-Kawai
- Laboratory of Animal Health II, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Shinji Kamisuki
- Center for Human and Animal Symbiosis Science, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan; Laboratory of Chemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Shibasaki Hisanobu
- Laboratory of Chemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Yukine Tsurukawa
- Laboratory of Chemistry, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Jumpei Uchiyama
- Center for Human and Animal Symbiosis Science, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan; Laboratory of Veterinary Microbiology I, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Masahiro Sakaguchi
- Laboratory of Veterinary Microbiology I, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Kenji Tsukamoto
- Laboratory of Animal Health II, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
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Regulation of Expression and Latency in BLV and HTLV. Viruses 2020; 12:v12101079. [PMID: 32992917 PMCID: PMC7601775 DOI: 10.3390/v12101079] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 09/20/2020] [Accepted: 09/21/2020] [Indexed: 12/14/2022] Open
Abstract
Human T-lymphotrophic virus type 1 (HTLV-1) and Bovine leukemia virus (BLV) belong to the Deltaretrovirus genus. HTLV-1 is the etiologic agent of the highly aggressive and currently incurable cancer adult T-cell leukemia (ATL) and a neurological disease HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). BLV causes neoplastic proliferation of B cells in cattle: enzootic bovine leucosis (EBL). Despite the severity of these conditions, infection by HTLV-1 and BLV appear in most cases clinically asymptomatic. These viruses can undergo latency in their hosts. The silencing of proviral gene expression and maintenance of latency are central for the establishment of persistent infection, as well as for pathogenesis in vivo. In this review, we will present the mechanisms that control proviral activation and retroviral latency in deltaretroviruses, in comparison with other exogenous retroviruses. The 5′ long terminal repeats (5′-LTRs) play a main role in controlling viral gene expression. While the regulation of transcription initiation is a major mechanism of silencing, we discuss topics that include (i) the epigenetic control of the provirus, (ii) the cis-elements present in the LTR, (iii) enhancers with cell-type specific regulatory functions, (iv) the role of virally-encoded transactivator proteins, (v) the role of repressors in transcription and silencing, (vi) the effect of hormonal signaling, (vii) implications of LTR variability on transcription and latency, and (viii) the regulatory role of non-coding RNAs. Finally, we discuss how a better understanding of these mechanisms may allow for the development of more effective treatments against Deltaretroviruses.
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Sato H, Watanuki S, Bai L, Borjigin L, Ishizaki H, Matsumoto Y, Hachiya Y, Sentsui H, Aida Y. A sensitive luminescence syncytium induction assay (LuSIA) based on a reporter plasmid containing a mutation in the glucocorticoid response element in the long terminal repeat U3 region of bovine leukemia virus. Virol J 2019; 16:66. [PMID: 31109347 PMCID: PMC6528319 DOI: 10.1186/s12985-019-1172-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/30/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Bovine leukemia virus (BLV) causes enzootic bovine leukosis, the most common neoplastic disease of cattle. Previously, we reported the luminescence syncytium induction assay (LuSIA), an assay for BLV infectivity based on CC81-BLU3G cells, which form syncytia expressing enhanced green fluorescent protein (EGFP) when co-cultured with BLV-infected cells. To develop a more sensitive LuSIA, we here focused on the glucocorticoid response element (GRE) within the U3 region of the BLV long terminal repeat (LTR). METHODS We changed five nucleotide sites of the GRE in a pBLU3-EGFP reporter plasmid containing the BLV-LTR U3 region promoter by site-directed mutagenesis and we then constructed a new reporter plasmid (pBLU3GREM-EGFP) in which the EGFP reporter gene was expressed under control of the GRE-mutated LTR-U3 promoter. We also established a new CC81-derived reporter cell line harboring the GRE-mutated LTR-U3 promoter (CC81-GREMG). To evaluate the sensibility, the utility and the specificity of the LuSIA using CC81-GREMG, we co-cultured CC81-GREMG cells with BLV-persistently infected cells, free-viruses, white blood cells (WBCs) from BLV-infected cows, and bovine immunodeficiency-like virus (BIV)- and bovine foamy virus (BFV)-infected cells. RESULTS We successfully constructed a new reporter plasmid harboring a mutation in the GRE and established a new reporter cell line, CC81-GREMG; this line was stably transfected with pBLU3GREM-EGFP in which the EGFP gene is expressed under control of the GRE-mutated LTR-U3 promoter and enabled direct visualization of BLV infectivity. The new LuSIA protocol using CC81-GREMG cells measures cell-to-cell infectivity and cell-free infectivity of BLV more sensitively than previous protocol using CC81-BLU3G. Furthermore, it did not respond to BIV and BFV infections, indicating that the LuSIA based on CC81-GREMG is specific for BLV infectivity. Moreover, we confirmed the utility of a new LuSIA based on CC81-GREMG cells using white blood cells (WBCs) from BLV-infected cows. Finally, the assay was useful for assessing the activity of neutralizing antibodies in plasma collected from BLV-infected cows. CONCLUSION The new LuSIA protocol is quantitative and more sensitive than the previous assay based on CC81-BLU3G cells and should facilitate development of several new BLV assays.
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Affiliation(s)
- Hirotaka Sato
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan.,Virus Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan
| | - Sonoko Watanuki
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan.,Virus Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan.,Laboratory of Global Animal Resource Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Lanlan Bai
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan.,Virus Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan
| | - Liushiqi Borjigin
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan
| | - Hiroshi Ishizaki
- Grazing Animal Unit, Division of Grassland Farming, Institute of Livestock and Grassland Science, NARO, 768 Senbonmatsu, Nasushiobara, Tochigi, 329-2793, Japan
| | - Yasunobu Matsumoto
- Laboratory of Global Animal Resource Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Yuma Hachiya
- Department of Veterinary Medicine, Nihon University, Kameino 1866, Fujisawa, Kanagawa, 252-0880, Japan
| | - Hiroshi Sentsui
- Department of Veterinary Medicine, Nihon University, Kameino 1866, Fujisawa, Kanagawa, 252-0880, Japan
| | - Yoko Aida
- Nano Medical Engineering Laboratory, RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan. .,Virus Infectious Diseases Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama, 3510198, Japan. .,Laboratory of Global Animal Resource Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
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Pluta A, Rola-Łuszczak M, Douville RN, Kuźmak J. Bovine leukemia virus long terminal repeat variability: identification of single nucleotide polymorphisms in regulatory sequences. Virol J 2018; 15:165. [PMID: 30359262 PMCID: PMC6202831 DOI: 10.1186/s12985-018-1062-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 09/25/2018] [Indexed: 12/03/2022] Open
Abstract
Background Limited data are available on the incidence of variations in nucleotide sequences of long terminal repeat (LTR) regions of Bovine Leukemia Virus (BLV). Consequently, the possible impact of SNPs on BLV LTR function are poorly elucidated. Thus, a detailed and representative study of full-length LTR sequences obtained from sixty-four BLV isolates from different geographical regions of Poland, Moldova, Croatia, Ukraine and Russia were analyzed for their genetic variability. Methods Overlap extension PCR, sequencing and Bayesian phylogenetic reconstruction of LTR sequences were performed. These analyses were followed by detailed sequence comparison, estimation of genetic heterogeneity and identification of transcription factor binding site (TFBS) modifications. Results Phylogenetic analysis of curated LTR sequences and those available in the GenBank database reflected the acknowledged env gene classification of BLV into 10 genotypes, and further clustered analysed sequences into three genotypes - G4, G7 and G8. Additional molecular studies revealed the presence of 97 point mutations distributed at 89 positions throughout all 64 LTR sequences. The highest rate of variability was noted in U3 and U5 subregions. However, the variability in regulatory sequences (VR) was assessed as lower than the variability within non-regulatory sequences (VNR) for both, U3 and U5 subregions. In contrast, VR value for R subregion, as well as for the total LTR, was higher than the VNR suggesting the existence of positive selection. Twelve unique SNPs for these LTR sequences localized in regulatory and non-regulatory elements were identified. The presence of different types of substitutions lead to the abrogation of present or to the creation of additional TFBS. Conclusion This study represents the largest study of LTR genetic variability of BLV field isolates from Eastern part of Europe. Phylogenetic analysis of LTRs supports the clustering BLV variants based on their geographic origin. The SNP screening showed variations modifying LTR regulatory sequences, as well as altering TFBS. These features warrant further exploration as they could be related to proviral load and distinctive regulation of BLV transcription and replication. Electronic supplementary material The online version of this article (10.1186/s12985-018-1062-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aneta Pluta
- Department of Biochemistry, National Veterinary Research Institute, Puławy, Poland.
| | | | - Renée N Douville
- Department of Biology, The University of Winnipeg, Winnipeg, MB, Canada.,Department of Immunology, University of Manitoba, Winnipeg, MB, Canada
| | - Jacek Kuźmak
- Department of Biochemistry, National Veterinary Research Institute, Puławy, Poland
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Development of a luminescence syncytium induction assay (LuSIA) for easily detecting and quantitatively measuring bovine leukemia virus infection. Arch Virol 2018; 163:1519-1530. [PMID: 29455325 DOI: 10.1007/s00705-018-3744-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 01/02/2018] [Indexed: 01/11/2023]
Abstract
Bovine leukemia virus (BLV) causes enzootic bovine leukosis and is closely related to the human T cell leukemia virus. Since BLV infection mostly occurs via cell-to-cell transmission, BLV infectivity is generally measured by culturing BLV-infected cells with reporter cells that form syncytia upon BLV infection. However, this method is time-consuming and requires skill. To visualize the infectivity of BLV, we developed a new assay called the luminescence syncytium induction assay (LuSIA) that is based on a new reporter cell line designated CC81-BLU3G. CC81-BLU3G is stably transfected with pBLU3-EGFP, which contains the BLV long terminal repeat U3 region linked to the enhanced-green fluorescence protein (EGFP) gene. CC81-BLU3G expresses the EGFP in response to BLV Tax expression specifically, and forms fluorescing syncytia when transfected with an infectious BLV plasmid or when cultured with BLV-infected cells. Compared to the conventional assay, LuSIA was more specific and detected cattle samples with low proviral loads. The fluorescing syncytia was easily detected by eye and automated scanning and LuSIA counts correlated strongly with the proviral load of infected cattle (R2 = 0.8942).
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8
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Frie MC, Droscha CJ, Greenlick AE, Coussens PM. MicroRNAs Encoded by Bovine Leukemia Virus (BLV) Are Associated with Reduced Expression of B Cell Transcriptional Regulators in Dairy Cattle Naturally Infected with BLV. Front Vet Sci 2018; 4:245. [PMID: 29379791 PMCID: PMC5775267 DOI: 10.3389/fvets.2017.00245] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 12/22/2017] [Indexed: 11/13/2022] Open
Abstract
Bovine leukemia virus (BLV) is estimated to infect over 83% of dairy herds and over 40% of all dairy cows in the United States. While, BLV only causes leukemia in a small proportion of animals, research indicates that BLV+ cattle exhibit reduced milk production and longevity that is distinct from lymphoma development. It is hypothesized that BLV negatively affects production by interfering with cattle immunity and increasing the risk of secondary infections. In particular, BLV+ cows demonstrate reduced circulating levels of both antigen-specific and total IgM. This study investigated possible mechanisms by which BLV could interfere with the production of IgM in naturally infected cattle. Specifically, total plasma IgM and the expression of genes IGJ, BLIMP1, BCL6, and PAX5 in circulating IgM+ B cells were measured in 15 naturally infected BLV+ and 15 BLV− cows. In addition, BLV proviral load (PVL) (a relative measurement of BLV provirus integrated into host DNA) and the relative expression of BLV TAX and 5 BLV microRNAs (miRNAs) were characterized and correlated to the expression of selected endogenous genes. BLV+ cows exhibited lower total plasma IgM and lower expression of IGJ, BLIMP1, and BCL6. While, BLV TAX and BLV miRNAs failed to correlate with IGJ expression, both BLV TAX and BLV miRNAs exhibited negative associations with BLIMP1 and BCL6 gene expression. The results suggest a possible transcriptional pathway by which BLV interferes with IgM production in naturally infected cattle.
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Affiliation(s)
- Meredith C Frie
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, United States
| | | | - Ashley E Greenlick
- Department of Animal Science, Michigan State University, East Lansing, MI, United States
| | - Paul M Coussens
- Department of Animal Science, Michigan State University, East Lansing, MI, United States
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Characterization of new RNA polymerase III and RNA polymerase II transcriptional promoters in the Bovine Leukemia Virus genome. Sci Rep 2016; 6:31125. [PMID: 27545598 PMCID: PMC4992882 DOI: 10.1038/srep31125] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 07/11/2016] [Indexed: 12/23/2022] Open
Abstract
Bovine leukemia virus latency is a viral strategy used to escape from the host immune system and contribute to tumor development. However, a highly expressed BLV micro-RNA cluster has been reported, suggesting that the BLV silencing is not complete. Here, we demonstrate the in vivo recruitment of RNA polymerase III to the BLV miRNA cluster both in BLV-latently infected cell lines and in ovine BLV-infected primary cells, through a canonical type 2 RNAPIII promoter. Moreover, by RPC6-knockdown, we showed a direct functional link between RNAPIII transcription and BLV miRNAs expression. Furthermore, both the tumor- and the quiescent-related isoforms of RPC7 subunits were recruited to the miRNA cluster. We showed that the BLV miRNA cluster was enriched in positive epigenetic marks. Interestingly, we demonstrated the in vivo recruitment of RNAPII at the 3′LTR/host genomic junction, associated with positive epigenetic marks. Functionally, we showed that the BLV LTR exhibited a strong antisense promoter activity and identified cis-acting elements of an RNAPII-dependent promoter. Finally, we provided evidence for an in vivo collision between RNAPIII and RNAPII convergent transcriptions. Our results provide new insights into alternative ways used by BLV to counteract silencing of the viral 5′LTR promoter.
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Characterization of novel Bovine Leukemia Virus (BLV) antisense transcripts by deep sequencing reveals constitutive expression in tumors and transcriptional interaction with viral microRNAs. Retrovirology 2016; 13:33. [PMID: 27141823 PMCID: PMC4855707 DOI: 10.1186/s12977-016-0267-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 04/28/2016] [Indexed: 11/10/2022] Open
Abstract
Background Bovine Leukemia Virus (BLV) is a deltaretrovirus closely related to the Human T cell leukemia virus-1 (HTLV-1). Cattle are the natural host of BLV where it integrates into B-cells, producing a lifelong infection. Most infected animals remain asymptomatic but following a protracted latency period about 5 % develop an aggressive leukemia/lymphoma, mirroring the disease trajectory of HTLV-1. The mechanisms by which these viruses provoke cellular transformation remain opaque. In both viruses little or no transcription is observed from the 5′LTR in tumors, however the proviruses are not transcriptionally silent. In the case of BLV a cluster of RNA polymerase III transcribed microRNAs are highly expressed, while the HTLV-1 antisense transcript HBZ is consistently found in all tumors examined. Results Here, using RNA-seq, we demonstrate that the BLV provirus also constitutively expresses antisense transcripts in all leukemic and asymptomatic samples examined. The first transcript (AS1) can be alternately polyadenylated, generating a transcript of ~600 bp (AS1-S) and a less abundant transcript of ~2200 bp (AS1-L). Alternative splicing creates a second transcript of ~400 bp (AS2). The coding potential of AS1-S/L is ambiguous, with a small open reading frame of 264 bp, however the transcripts are primarily retained in the nucleus, hinting at a lncRNA-like role. The AS1-L transcript overlaps the BLV microRNAs and using high throughput sequencing of RNA-ligase-mediated (RLM) 5′RACE, we show that the RNA-induced silencing complex (RISC) cleaves AS1-L. Furthermore, experiments using altered BLV proviruses with the microRNAs either deleted or inverted point to additional transcriptional interference between the two viral RNA species. Conclusions The identification of novel viral antisense transcripts shows the BLV provirus to be far from silent in tumors. Furthermore, the consistent expression of these transcripts in both leukemic and nonmalignant clones points to a vital role in the life cycle of the virus and its tumorigenic potential. Additionally, the cleavage of the AS1-L transcript by the BLV encoded microRNAs and the transcriptional interference between the two viral RNA species suggest a shared role in the regulation of BLV. Electronic supplementary material The online version of this article (doi:10.1186/s12977-016-0267-8) contains supplementary material, which is available to authorized users.
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Bovine leukemia virus: a major silent threat to proper immune responses in cattle. Vet Immunol Immunopathol 2014; 163:103-14. [PMID: 25554478 DOI: 10.1016/j.vetimm.2014.11.014] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/27/2014] [Accepted: 11/26/2014] [Indexed: 11/22/2022]
Abstract
Bovine leukemia virus (BLV) infection is widespread in the US dairy industry and the majority of producers do not actively try to manage or reduce BLV incidence within their herds. However, BLV is estimated to cost the dairy industry hundreds of millions of dollars annually and this is likely a conservative estimate. BLV is not thought to cause animal distress or serious pathology unless infection progresses to leukemia or lymphoma. However, a wealth of research supports the notion that BLV infection causes widespread abnormal immune function. BLV infection can impact cells of both the innate and adaptive immune system and alter proper functioning of uninfected cells. Despite strong evidence of abnormal immune signaling and functioning, little research has investigated the large-scale effects of BLV infection on host immunity and resistance to other infectious diseases. This review focuses on mechanisms of immune suppression associated with BLV infection, specifically aberrant signaling, proliferation and apoptosis, and the implications of switching from BLV latency to activation. In addition, this review will highlight underdeveloped areas of research relating to BLV infection and how it causes immune suppression.
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Distribution and characteristics of bovine leukemia virus integration sites in the host genome at three different clinical stages of infection. Arch Virol 2014; 160:39-46. [PMID: 25240623 DOI: 10.1007/s00705-014-2224-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 08/30/2014] [Indexed: 10/24/2022]
Abstract
Bovine leukemia virus (BLV) is an oncogenic retrovirus closely related to human T-cell lymphotropic virus. BLV-infected cattle are categorized as asymptomatic carriers or as having persistent lymphocytosis or enzootic bovine leukemia, depending on the clinical stage. We investigated the BLV integration site distribution at three BLV clinical stages and examined genome sequence features around the integration sites. In all, 264 BLV integration sites, at various locations on each chromosome, were identified in 28 cattle by inverse PCR and BLAST searches. Approximately one-third of BLV proviruses were independently integrated within transcriptional units, and approximately 10 % were integrated near transcription start sites. Moreover, less than 7 % of BLV integration sites were located near CpG islands. BLV did not preferentially integrate into transcriptionally active regions during any of the clinical stages. At the nucleotide level, regions around BLV integration points were significantly A/T rich with weak sequence consensus. BLV preferentially integrated within long interspersed nuclear repeat elements. Although BLV integration sites may not be associated with disease progression, integration is selective at the nucleotide level.
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Moratorio G, Fischer S, Bianchi S, Tomé L, Rama G, Obal G, Carrión F, Pritsch O, Cristina J. A detailed molecular analysis of complete bovine leukemia virus genomes isolated from B-cell lymphosarcomas. Vet Res 2013; 44:19. [PMID: 23506507 PMCID: PMC3618307 DOI: 10.1186/1297-9716-44-19] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 01/30/2013] [Indexed: 01/08/2023] Open
Abstract
It is widely accepted that the majority of cancers result from multiple cellular events leading to malignancy after a prolonged period of clinical latency, and that the immune system plays a critical role in the control of cancer progression. Bovine leukemia virus (BLV) is an oncogenic member of the Retroviridae family. Complete genomic sequences of BLV strains isolated from peripheral blood mononuclear cells (PBMC) from cattle have been previously reported. However, a detailed characterization of the complete genome of BLV strains directly isolated from bovine tumors is much needed in order to contribute to the understanding of the mechanisms of leukemogenesis induced by BLV in cattle. In this study, we performed a molecular characterization of BLV complete genomes from bovine B-cell lymphosarcoma isolates. A nucleotide substitution was found in the glucocorticoid response element (GRE) site of the 5' long terminal repeat (5'LTR) of the BLV isolates. All amino acid substitutions in Tax previously found to be related to stimulate high transcriptional activity of 5'LTR were not found in these studies. Amino acid substitutions were found in the nucleocapsid, gp51 and G4 proteins. Premature stop-codons in R3 were observed. Few mutations or amino acid substitutions may be needed to allow BLV provirus to achieve silencing. Substitutions that favor suppression of viral expression in malignant B cells might be a strategy to circumvent effective immune attack.
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Affiliation(s)
- Gonzalo Moratorio
- Laboratorio de Virología Molecular, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo 11400, Uruguay.
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14
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Gu J, Zhang Y, Lian X, Sun H, Wang J, Liu W, Meng G, Li P, Zhu D, Jin Y, Cao R. Functional analysis of the interferon-stimulated response element of porcine circovirus type 2 and its role during viral replication in vitro and in vivo. Virol J 2012; 9:152. [PMID: 22871036 PMCID: PMC3487966 DOI: 10.1186/1743-422x-9-152] [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: 11/06/2011] [Accepted: 07/27/2012] [Indexed: 12/03/2022] Open
Abstract
Background Porcine circovirus type 2 (PCV2) is associated with post-weaning multi-systemic wasting syndrome (PMWS) in young weaned pigs. Immune stimulation was found to activate the replication of PCV2 and exacerbate the clinical outcome of the infection. Proper amount of interferon-α (IFN-α) is able to enhance PCV2 infection and production in Porcine kidney-15 (PK-15) cells when administered after inoculation. Methods In the present study, luciferase reporter assays, construction of mutant viruses, Analysis the replication efficiency and the response to IFN-α treatment in PK-15 cells and animal experiments were carried out to analyze the function of interferon-stimulated response element (ISRE) of PCV2 and its role during viral replication in vitro and in vivo. Results A functional viral ISRE sequence, 5′-CTGAAAACGAAAGA-3′, was identified in Rep gene promoter (Prep) of PCV2. PCV2 Prep is composed of two mini promoters, the proximal one span the sequence +1 to -106, containing an ISRE while the distal mini promoter is composed of three tandem GC box like sites locate at -85 to -194. It was demonstrated that viral ISRE is necessary for porcine IFN-α initiated luciferase expression enhancement and it plays an important role in affecting the replication efficiency of PCV2 in vivo and in vitro. Conclusions These findings provide a theoretical basis for the Phenomenon of immunostimulation is able to enhance PCV2 infection, and improve the understanding of the complicated mechanisms involved in the host and pathogen interactions of PCV2.
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Affiliation(s)
- Jinyan Gu
- Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agriculture University, Nanjing 210095, Jiangsu, China
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Colin L, Dekoninck A, Reichert M, Calao M, Merimi M, Van den Broeke A, Vierendeel V, Cleuter Y, Burny A, Rohr O, Van Lint C. Chromatin disruption in the promoter of bovine leukemia virus during transcriptional activation. Nucleic Acids Res 2011; 39:9559-73. [PMID: 21890901 PMCID: PMC3239207 DOI: 10.1093/nar/gkr671] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Bovine leukemia virus expression relies on its chromatin organization after integration into the host cell genome. Proviral latency, which results from transcriptional repression in vivo, represents a viral strategy to escape the host immune system and likely allows for tumor progression. Here, we discriminated two types of latency: an easily reactivable latent state of the YR2 provirus and a ‘locked’ latent state of the L267 provirus. The defective YR2 provirus was characterized by the presence of nuclease hypersensitive sites at the U3/R junction and in the R/U5 region of the 5′-long terminal repeat (5′-LTR), whereas the L267 provirus displayed a closed chromatin configuration at the U3/R junction. Reactivation of viral expression in YR2 cells by the phorbol 12-myristate 13-acetate (PMA) plus ionomycin combination was accompanied by a rapid but transient chromatin remodeling in the 5′-LTR, leading to an increased PU.1 and USF-1/USF-2 recruitment in vivo sustained by PMA/ionomycin-mediated USF phosphorylation. In contrast, viral expression was not reactivated by PMA/ionomycin in L267 cells, because the 5′-LTR U3/R region remained inaccessible to nucleases and hypermethylated at CpG dinucleotides. Remarkably, we elucidated the BLV 5′-LTR chromatin organization in PBMCs isolated from BLV-infected cows, thereby depicting the virus hiding in vivo in its natural host.
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Affiliation(s)
- Laurence Colin
- Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
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Pierard V, Guiguen A, Colin L, Wijmeersch G, Vanhulle C, Van Driessche B, Dekoninck A, Blazkova J, Cardona C, Merimi M, Vierendeel V, Calomme C, Nguyên TLA, Nuttinck M, Twizere JC, Kettmann R, Portetelle D, Burny A, Hirsch I, Rohr O, Van Lint C. DNA cytosine methylation in the bovine leukemia virus promoter is associated with latency in a lymphoma-derived B-cell line: potential involvement of direct inhibition of cAMP-responsive element (CRE)-binding protein/CRE modulator/activation transcription factor binding. J Biol Chem 2010; 285:19434-49. [PMID: 20413592 PMCID: PMC2885223 DOI: 10.1074/jbc.m110.107607] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 03/31/2010] [Indexed: 02/02/2023] Open
Abstract
Bovine leukemia virus (BLV) proviral latency represents a viral strategy to escape the host immune system and allow tumor development. Besides the previously demonstrated role of histone deacetylation in the epigenetic repression of BLV expression, we showed here that BLV promoter activity was induced by several DNA methylation inhibitors (such as 5-aza-2'-deoxycytidine) and that overexpressed DNMT1 and DNMT3A, but not DNMT3B, down-regulated BLV promoter activity. Importantly, cytosine hypermethylation in the 5'-long terminal repeat (LTR) U3 and R regions was associated with true latency in the lymphoma-derived B-cell line L267 but not with defective latency in YR2 cells. Moreover, the virus-encoded transactivator Tax(BLV) decreased DNA methyltransferase expression levels, which could explain the lower level of cytosine methylation observed in the L267(LTaxSN) 5'-LTR compared with the L267 5'-LTR. Interestingly, DNA methylation inhibitors and Tax(BLV) synergistically activated BLV promoter transcriptional activity in a cAMP-responsive element (CRE)-dependent manner. Mechanistically, methylation at the -154 or -129 CpG position (relative to the transcription start site) impaired in vitro binding of CRE-binding protein (CREB) transcription factors to their respective CRE sites. Methylation at -129 CpG alone was sufficient to decrease BLV promoter-driven reporter gene expression by 2-fold. We demonstrated in vivo the recruitment of CREB/CRE modulator (CREM) and to a lesser extent activating transcription factor-1 (ATF-1) to the hypomethylated CRE region of the YR2 5'-LTR, whereas we detected no CREB/CREM/ATF recruitment to the hypermethylated corresponding region in the L267 cells. Altogether, these findings suggest that site-specific DNA methylation of the BLV promoter represses viral transcription by directly inhibiting transcription factor binding, thereby contributing to true proviral latency.
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Affiliation(s)
- Valérie Pierard
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Allan Guiguen
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Laurence Colin
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Gaëlle Wijmeersch
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Caroline Vanhulle
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Benoît Van Driessche
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Ann Dekoninck
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Jana Blazkova
- the Institut de Cancérologie de Marseille, UMR 599 INSERM, Institut Paoli-Calmettes, Université de la Méditerranée, Boulevard Lei Roure 27, 13009 Marseille, France
| | - Christelle Cardona
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Makram Merimi
- the Laboratory of Experimental Hematology, Institut Jules Bordet, Université Libre de Bruxelles, Boulevard de Waterloo 121, 1000 Bruxelles, Belgium
| | - Valérie Vierendeel
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Claire Calomme
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Thi Liên-Anh Nguyên
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Michèle Nuttinck
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Jean-Claude Twizere
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Richard Kettmann
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Daniel Portetelle
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Arsène Burny
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Ivan Hirsch
- the Institut de Cancérologie de Marseille, UMR 599 INSERM, Institut Paoli-Calmettes, Université de la Méditerranée, Boulevard Lei Roure 27, 13009 Marseille, France
| | - Olivier Rohr
- the Institut Universitaire de Technologie Louis Pasteur de Schiltigheim, University of Strasbourg, 1 Allée d'Athènes, 67300 Schiltigheim, France
| | - Carine Van Lint
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
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Gómez-Lucía E, Collado VM, Miró G, Doménech A. Effect of type-I interferon on retroviruses. Viruses 2009; 1:545-73. [PMID: 21994560 PMCID: PMC3185530 DOI: 10.3390/v1030545] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 10/05/2009] [Accepted: 10/26/2009] [Indexed: 12/21/2022] Open
Abstract
Type-I interferons (IFN-I) play an important role in the innate immune response to several retroviruses. They seem to be effective in controlling the in vivo infection, though many of the clinical signs of retroviral infection may be due to their continual presence which over-stimulates the immune system and activates apoptosis. IFN-I not only affect the immune system, but also operate directly on virus replication. Most data suggest that the in vitro treatment with IFN-I of retrovirus infected cells inhibits the final stages of virogenesis, avoiding the correct assembly of viral particles and their budding, even though the mechanism is not well understood. However, in some retroviruses IFN-I may also act at a previous stage as some retroviral LTRs posses sequences homologous to the IFN-stimulated response element (ISRE). When stimulated, ISREs control viral transcription. HIV-1 displays several mechanisms for evading IFN-I, such as through Tat and Nef. Besides IFN-α and IFN-β, some other type I IFN, such as IFN-τ and IFN-ω, have potent antiviral activity and are promising treatment drugs.
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Affiliation(s)
- Esperanza Gómez-Lucía
- Departamento de Sanidad Animal, Facultad Veterinaria, Universidad Complutense, 28040 Madrid, Spain; E-mails: (V.M.C.); (G.M.); (A.D.)
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18
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Gillet N, Florins A, Boxus M, Burteau C, Nigro A, Vandermeers F, Balon H, Bouzar AB, Defoiche J, Burny A, Reichert M, Kettmann R, Willems L. Mechanisms of leukemogenesis induced by bovine leukemia virus: prospects for novel anti-retroviral therapies in human. Retrovirology 2007; 4:18. [PMID: 17362524 PMCID: PMC1839114 DOI: 10.1186/1742-4690-4-18] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Accepted: 03/16/2007] [Indexed: 12/15/2022] Open
Abstract
In 1871, the observation of yellowish nodules in the enlarged spleen of a cow was considered to be the first reported case of bovine leukemia. The etiological agent of this lymphoproliferative disease, bovine leukemia virus (BLV), belongs to the deltaretrovirus genus which also includes the related human T-lymphotropic virus type 1 (HTLV-1). This review summarizes current knowledge of this viral system, which is important as a model for leukemogenesis. Recently, the BLV model has also cast light onto novel prospects for therapies of HTLV induced diseases, for which no satisfactory treatment exists so far.
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Affiliation(s)
- Nicolas Gillet
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Arnaud Florins
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Mathieu Boxus
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Catherine Burteau
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Annamaria Nigro
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Fabian Vandermeers
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Hervé Balon
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Amel-Baya Bouzar
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Julien Defoiche
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Arsène Burny
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | | | - Richard Kettmann
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
| | - Luc Willems
- Molecular and Cellular Biology, Faculté Universitaire des Sciences Agronomiques, Gembloux, Belgium
- Luc Willems, National fund for Scientific Research, Molecular and Cellular Biology laboratory, 13 avenue Maréchal Juin, 5030 Gembloux, Belgium
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Zhao X, McGirr KM, Buehring GC. Potential evolutionary influences on overlapping reading frames in the bovine leukemia virus pXBL region. Genomics 2007; 89:502-11. [PMID: 17239558 DOI: 10.1016/j.ygeno.2006.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 11/27/2006] [Accepted: 12/14/2006] [Indexed: 01/25/2023]
Abstract
Bovine leukemia virus contains a pXBL region encoding the 3' parts of four regulatory proteins (Tax, Rex, G4, R3) in overlapping reading frames. Here we report the pXBL polymorphisms of 30 isolates from four countries. Rates of overall and synonymous substitutions were consistently lower, and nucleotide/amino acid composition bias and codon bias higher, in more-overlapped than in less-overlapped regions. Ratios of nonsynonymous/synonymous substitutions were lowest in the tax gene and its subregions. The 5' parts of the four genes showed selection patterns corresponding to their genomic context outside of the pXBL region. Longer G4 variants due to a natural stop codon mutation had additional triple overlap with reduced sequence variability. These data support the concept that a higher level of overlapping in coding regions correlates with greater evolutionary constraint. Tax, the most conserved among the four regulatory proteins, showed purifying selection consistent with its importance in the viral life cycle.
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Affiliation(s)
- Xiangrong Zhao
- Graduate Program in Endocrinology, University of California at Berkeley, 3060 Valley Life Science Building, Berkeley, CA 94720-3140, USA.
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20
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Zhao X, Jimenez C, Sentsui H, Buehring GC. Sequence polymorphisms in the long terminal repeat of bovine leukemia virus: evidence for selection pressures in regulatory sequences. Virus Res 2006; 124:113-24. [PMID: 17123656 DOI: 10.1016/j.virusres.2006.10.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Revised: 10/15/2006] [Accepted: 10/20/2006] [Indexed: 10/23/2022]
Abstract
Bovine leukemia virus (BLV) is an oncogenic virus widespread in cattle. It belongs to the genus Deltaretrovirus of the family Retroviridae along with human and simian T-lymphotropic viruses. The BLV transcriptional promoter is located in the proviral 5' long terminal repeat (LTR), composed of U3, R, and U5 regions. BLV LTR contains multiple cis-acting elements important for promoter activity, a short coding sequence (encoding the NH(2) terminus of the G4 regulatory protein), and non-regulatory/non-coding regions. Variation in coding sequences of BLV structural proteins has been studied extensively, but little work has been done on sequence variability of non-coding regions, mostly located in LTR. Here, we report the first study on the natural diversity of the BLV LTR, using viral isolates from 52 cattle in several different areas worldwide. Nucleotide variations from the consensus sequence were observed in most isolates and clustered phylogenetically, corresponding to the geographic distribution of donor cattle. Overall, regulatory regions were significantly more conserved than non-regulatory regions in the BLV LTR, as well as in LTR sub-regions (U3, R, and U5). Evidence of selection pressures in BLV LTR suggests that selection occurs not only in coding sequences, but may also involve regulatory sequences.
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Affiliation(s)
- Xiangrong Zhao
- Graduate Program in Endocrinology, University of California, Berkeley, CA 94720-3140, USA.
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Calomme C, Dekoninck A, Nizet S, Adam E, Nguyên TLA, Van Den Broeke A, Willems L, Kettmann R, Burny A, Van Lint C. Overlapping CRE and E box motifs in the enhancer sequences of the bovine leukemia virus 5' long terminal repeat are critical for basal and acetylation-dependent transcriptional activity of the viral promoter: implications for viral latency. J Virol 2004; 78:13848-64. [PMID: 15564493 PMCID: PMC533944 DOI: 10.1128/jvi.78.24.13848-13864.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Accepted: 08/04/2004] [Indexed: 11/20/2022] Open
Abstract
Bovine leukemia virus (BLV) infection is characterized by viral latency in a large proportion of cells containing an integrated provirus. In this study, we postulated that mechanisms directing the recruitment of deacetylases to the BLV 5' long terminal repeat (LTR) could explain the transcriptional repression of viral expression in vivo. Accordingly, we showed that BLV promoter activity was induced by several deacetylase inhibitors (such as trichostatin A [TSA]) in the context of episomal LTR constructs and in the context of an integrated BLV provirus. Moreover, treatment of BLV-infected cells with TSA increased H4 acetylation at the viral promoter, showing a close correlation between the level of histone acetylation and transcriptional activation of the BLV LTR. Among the known cis-regulatory DNA elements located in the 5' LTR, three E box motifs overlapping cyclic AMP responsive elements (CREs) in U3 were shown to be involved in transcriptional repression of BLV basal gene expression. Importantly, the combined mutations of these three E box motifs markedly reduced the inducibility of the BLV promoter by TSA. E boxes are susceptible to recognition by transcriptional repressors such as Max-Mad-mSin3 complexes that repress transcription by recruiting deacetylases. However, our in vitro binding studies failed to reveal the presence of Mad-Max proteins in the BLV LTR E box-specific complexes. Remarkably, TSA increased the occupancy of the CREs by CREB/ATF. Therefore, we postulated that the E box-specific complexes exerted their negative cooperative effect on BLV transcription by steric hindrance with the activators CREB/ATF and/or their transcriptional coactivators possessing acetyltransferase activities. Our results thus suggest that the overlapping CRE and E box elements in the BLV LTR were selected during evolution as a novel strategy for BLV to allow better silencing of viral transcription and to escape from the host immune response.
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Affiliation(s)
- Claire Calomme
- Université Libre de Bruxelles (ULB), Institut de Biologie et de Médecine Moléculaires (IBMM), Service de Chimie Biologique, Laboratoire de Virologie Moléculaire, Rue des Profs Jeener et Brachet, 12, 6041 Gosselies, Belgium
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Dekoninck A, Calomme C, Nizet S, de Launoit Y, Burny A, Ghysdael J, Van Lint C. Identification and characterization of a PU.1/Spi-B binding site in the bovine leukemia virus long terminal repeat. Oncogene 2003; 22:2882-96. [PMID: 12771939 DOI: 10.1038/sj.onc.1206392] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Bovine leukemia virus (BLV) is a B-lymphotropic oncogenic retrovirus whose transcriptional promoter is located in the viral 5' long terminal repeat (LTR). To date, no B-lymphocyte-specific cis-regulatory element has been identified in this region. Since ETS proteins are known to regulate transcription of numerous retroviruses, we searched for the presence in the BLV promoter region of binding sites for PU.1/Spi-1, a B-cell- and macrophage-specific ETS family member. In this report, nucleotide sequence analysis of the viral LTR identified a PUbox located at -95/-84 bp. We demonstrated by gel shift and supershift assays that PU.1 and the related Ets transcription factor Spi-B interacted specifically with this PUbox. A 2-bp mutation (GGAA-->CCAA) within this motif abrogated PU.1/Spi-B binding. This mutation caused a marked decrease in LTR-driven basal gene expression in transient transfection assays of B-lymphoid cell lines, but did not impair the responsiveness of the BLV promoter to the virus-encoded transactivator Tax(BLV). Moreover, ectopically expressed PU.1 and Spi-B proteins transactivated the BLV promoter in a PUbox-dependent manner. Taken together, our results provide the first demonstration of regulation of the BLV promoter by two B-cell-specific Ets transcription factors, PU.1 and Spi-B. The PU.1/Spi-B binding site identified here could play an important role in BLV replication and B-lymphoid tropism.
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Affiliation(s)
- Ann Dekoninck
- Laboratoire de Virologie Moléculaire, Service de Chimie Biologique, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
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Merezak C, Reichert M, Van Lint C, Kerkhofs P, Portetelle D, Willems L, Kettmann R. Inhibition of histone deacetylases induces bovine leukemia virus expression in vitro and in vivo. J Virol 2002; 76:5034-42. [PMID: 11967319 PMCID: PMC136152 DOI: 10.1128/jvi.76.10.5034-5042.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Packaging into nucleosomes results in a global transcriptional repression as a consequence of exclusion of sequence-specific factors. This inhibition can be relieved by using inhibitors of histone deacetylases, acetylation being a major characteristic of transcriptionally active chromatin. Paradoxically, the expression of only approximately 2% of the total cellular genes is modulated by histone hyperacetylation. To unravel the potential role of this transcriptional control on BLV expression, we tested the effect of two highly specific inhibitors of deacetylases, trichostatin A (TSA) and trapoxin (TPX). Our results demonstrate that treatment with TSA efficiently enhanced long terminal repeat-directed gene expression of integrated reporter constructs in heterologous D17 stable cell lines. To further examine the biological relevance of these observations made in vitro, we analyzed ex vivo-isolated peripheral blood mononuclear cells (PBMCs) from bovine leukemia virus (BLV)-infected sheep. TSA deacetylase inhibitor induced a drastic increase in viral expression at levels comparable to those induced by treatment with phorbol-12-myristate 13-acetate and ionomycin, the most efficient activators of BLV expression known to date. TSA acted directly on BLV-infected B lymphocytes to increase viral expression and does not seem to require T-cell cooperation. Inhibition of deacetylation after treatment with TSA or TPX also significantly increased viral expression in PBMCs from cattle, the natural host for BLV. Together, our results show that BLV gene expression is, like that of a very small fraction of cellular genes, also regulated by deacetylation.
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Affiliation(s)
- C Merezak
- Molecular and Cellular Biology, Faculty of Agronomy, Gembloux, Belgium
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Calomme C, Nguyen TLA, de Launoit Y, Kiermer V, Droogmans L, Burny A, Van Lint C. Upstream stimulatory factors binding to an E box motif in the R region of the bovine leukemia virus long terminal repeat stimulates viral gene expression. J Biol Chem 2002; 277:8775-89. [PMID: 11741930 DOI: 10.1074/jbc.m107441200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bovine leukemia virus (BLV) promoter is located in its 5'-long terminal repeat and is composed of the U3, R, and U5 regions. BLV transcription is regulated by cis-acting elements located in the U3 region, including three 21-bp enhancers required for transactivation of the BLV promoter by the virus-encoded transactivator Tax(BLV). In addition to the U3 cis-acting elements, both the R and U5 regions contain stimulatory sequences. To date, no transcription factor-binding site has been identified in the R region. Here sequence analysis of this region revealed the presence of a potential E box motif (5'-CACGTG-3'). By competition and supershift gel shift assays, we demonstrated that the basic helix-loop-helix transcription factors USF1 and USF2 specifically interacted with this R region E box motif. Mutations abolishing upstream stimulatory factor (USF) binding caused a reproducible decrease in basal or Tax-activated BLV promoter-driven gene expression in transient transfection assays of B-lymphoid cell lines. Cotransfection experiments showed that the USF1 and USF2a transactivators were able to act through the BLV R region E box. Taken together, these results physically and functionally characterize a USF-binding site in the R region of BLV. This E box motif located downstream of the transcription start site constitutes a new positive regulatory element involved in the transcriptional activity of the BLV promoter and could play an important role in virus replication.
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Affiliation(s)
- Claire Calomme
- Université Libre de Bruxelles, Institut de Biologie et de Médecine Moléculaires, Service de Chimie Biologique, Laboratoire de Virologie Moléculaire, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
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Merezak C, Pierreux C, Adam E, Lemaigre F, Rousseau GG, Calomme C, Van Lint C, Christophe D, Kerkhofs P, Burny A, Kettmann R, Willems L. Suboptimal enhancer sequences are required for efficient bovine leukemia virus propagation in vivo: implications for viral latency. J Virol 2001; 75:6977-88. [PMID: 11435578 PMCID: PMC114426 DOI: 10.1128/jvi.75.15.6977-6988.2001] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Repression of viral expression is a major strategy developed by retroviruses to escape from the host immune response. The absence of viral proteins (or derived peptides) at the surface of an infected cell does not permit the establishment of an efficient immune attack. Such a strategy appears to have been adopted by animal oncoviruses such as bovine leukemia virus (BLV) and human T-cell leukemia virus (HTLV). In BLV-infected animals, only a small fraction of the infected lymphocytes (between 1 in 5,000 and 1 in 50,000) express large amounts of viral proteins; the vast majority of the proviruses are repressed at the transcriptional level. Induction of BLV transcription involves the interaction of the virus-encoded Tax protein with the CREB/ATF factors; the resulting complex is able to interact with three 21-bp Tax-responsive elements (TxRE) located in the 5' long terminal repeat (5' LTR). These TxRE contain cyclic AMP-responsive elements (CRE), but, remarkably, the "TGACGTCA" consensus is never strictly conserved in any viral strain (e.g.,AGACGTCA, TGACGGCA, TGACCTCA). To assess the role of these suboptimal CREs, we introduced a perfect consensus sequence within the TxRE and showed by gel retardation assays that the binding efficiency of the CREB/ATF proteins was increased. However, trans-activation of a luciferase-based reporter by Tax was not affected in transient transfection assays. Still, in the absence of Tax, the basal promoter activity of the mutated LTR was increased as much as 20-fold. In contrast, mutation of other regulatory elements within the LTR (the E box, NF-kappa B, and glucocorticoid- or interferon-responsive sites [GRE or IRF]) did not induce a similar alteration of the basal transcription levels. To evaluate the biological relevance of these observations made in vitro, the mutations were introduced into an infectious BLV molecular clone. After injection into sheep, it appeared that all the recombinants were infectious in vivo and did not revert into a wild-type virus. All of them, except one, propagated at wild-type levels, indicating that viral spread was not affected by the mutation. The sole exception was the CRE mutant; proviral loads were drastically reduced in sheep infected with this type of virus. We conclude that a series of sites (NF-kappa B, IRF, GRE, and the E box) are not required for efficient viral spread in the sheep model, although mutation of some of these motifs might induce a minor phenotype during transient transfection assays in vitro. Remarkably, a provirus (pBLV-Delta 21-bp) harboring only two TxRE was infectious and propagated at wild-type levels. And, most importantly, reconstitution of a consensus CRE, within the 21-bp enhancers increases binding of CREB/ATF proteins but abrogates basal repression of LTR-directed transcription in vitro. Suboptimal CREs are, however, essential for efficient viral spread within infected sheep, although these sites are dispensable for infectivity. These results suggest an evolutionary selection of suboptimal CREs that repress viral expression with escape from the host immune response. These observations, which were obtained in an animal model for HTLV-1, are of interest for oncovirus-induced pathogenesis in humans.
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Affiliation(s)
- C Merezak
- Molecular and Cellular Biology, Faculty of Agronomy, Gembloux, Belgium
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Nakao K, Nakata K, Yamashita M, Tamada Y, Hamasaki K, Ishikawa H, Kato Y, Eguchi K, Ishii N. p48 (ISGF-3gamma) is involved in interferon-alpha-induced suppression of hepatitis B virus enhancer-1 activity. J Biol Chem 1999; 274:28075-8. [PMID: 10497156 DOI: 10.1074/jbc.274.40.28075] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Interferon-alpha (IFN-alpha) suppresses hepatitis B virus (HBV) gene expression by reducing its enhancer-1 activity. IFN-alpha induces transcription factors, interferon-stimulated gene factor 3 (ISGF3), and interferon regulatory factor-1 (IRF-1), which activate interferon-inducible gene expression through binding to the interferon-stimulated regulatory element (ISRE) "AGTTTCNNTTTCNC" in the gene promoters. We found the ISRE-like sequence "AGGCTTTCACTTTCTC" in the HBV enhancer-1 region and elucidated the role of this sequence. Gel mobility shift assay showed binding of in vitro translated IRF-1 and in vitro translated p48 (ISGF3-gamma), which is a component of ISGF3 to this sequence. However, nuclear extracts binding to this sequence from human hepatoma cells (HuH-7) treated with IFN-alpha contained only the protein consisted of p48. In transfection experiments, IFN-alpha suppressed the HBV enhancer-1 activity, and overexpression of p48 enhanced this inhibitory effect. Both mutation and deletion of the ISRE-like sequence in the HBV enhancer-1 region reduced the suppressive effect of IFN-alpha. Our results suggest that the ISRE-like sequence in the HBV enhancer-1 can interact with the protein containing p48 and mediate the IFN-alpha-induced suppression of the enhancer activity.
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Affiliation(s)
- K Nakao
- Health Research Center, Nagasaki University School of Medicine, 1-7-1, Sakamoto, Nagasaki 852-8501, Japan.
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