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Dysfunction of bovine endogenous retrovirus K2 envelope glycoprotein is related to unsuccessful intracellular trafficking. J Virol 2014; 88:6896-905. [PMID: 24696495 DOI: 10.1128/jvi.00288-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Endogenous retroviruses (ERVs) are the remnants of retroviral infection of ancestral germ cells. Mutations introduced into ERVs halt the production of infectious agents, but their effects on the function of retroviral proteins are not fully understood. Retroviral envelope glycoproteins (Envs) are utilized in membrane fusion during viral entry, and we recently identified intact coding sequences for bovine endogenous retrovirus K1 (BERV-K1) and BERV-K2 Envs. Amino acid sequences of BERV-K1 Env (also called Fematrin-1) and BERV-K2 Env are similar, and both viruses are classified in the genus Betaretrovirus. While Fematrin-1 plays an important role in cell-to-cell fusion in bovine placenta, the BERV-K2 envelope gene is marginally expressed in vivo, and its recombinant Env protein is defective in membrane fusion due to inefficient cleavage of surface (SU) and transmembrane subunits. Here, we conducted chimeric analyses of Fematrin-1 and BERV-K2 Envs and revealed that defective maturation of BERV-K2 Env contributed to failed intracellular trafficking. Fluorescence microscopy and flow cytometric analysis suggested that in contrast to Fematrin-1 Env, BERV-K2 Env could not be transported from the endoplasmic reticulum to the trans-Golgi network, where cellular proteases required for processing retroviral Envs are localized. We also identified that one of the responsive regions of this phenomenon resided within a 65-amino-acid region of BERV-K2 SU. This is the first report to identify that retroviral Env SU is involved in the regulation of intracellular trafficking, and it may help to elucidate the maturation process of Fematrin-1 and other related Envs. IMPORTANCE Retroviruses utilize envelope glycoproteins (Envs) to enter host target cells. Mature retroviral Env is a heterodimer, which consists of surface (SU) and transmembrane (TM) subunits that are generated by the cleavage of an Env precursor protein in the trans-Golgi network. SU and TM mediate the recognition of the entry receptor and virus-host membrane fusion, respectively. However, unexplained issues remain for the maturation process of retroviral Env. We previously reported that bovine endogenous retrovirus K2 (BERV-K2) Env lost fusogenicity due to a defect in the cleavage of SU and TM. In this study, we identified that mutations residing in BERV-K2 SU disturbed intracellular trafficking of BERV-K2 Env and resulted its inefficient cleavage. Because SU is not known to play an important role in this process, our study may provide novel insights into the maturation mechanism of retroviral Envs.
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Abstract
Joint infectious causation of cancer has been accepted in a few well-studied instances, including Burkitt's lymphoma and liver cancer. In general, evidence for the involvement of parasitic agents in oncogenesis has expanded, and recent advances in the application of molecular techniques have revealed specific mechanisms by which host cells are transformed. Many parasites evolve to circumvent immune-mediated detection and destruction and to control critical aspects of host cell reproduction and survival: cell proliferation, apoptosis, adhesion, and immortalization. The host has evolved tight regulation of these cellular processes-the control of each represents a barrier to cancer. These barriers need to be compromised for oncogenesis to occur. The abrogation of a barrier is therefore referred to as an essential cause of cancer. Alternatively, some aspects of cellular regulation restrain but do not block oncogenesis. Relaxation of a restraint is therefore referred to as an exacerbating cause of cancer. In this chapter, we explore past and current evidence for joint infectious causation of cancer in the context of essential and exacerbating causes. We stress that discovery of joint infectious causation may provide great improvements in controlling cancer, particularly through the identification of many additional nonhuman targets for synergistic interventions for prevention and treatment.
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Affiliation(s)
- Paul W Ewald
- Department of Biology, University of Louisville, Louisville, Kentucky, USA.
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203
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Meyerson NR, Rowley PA, Swan CH, Le DT, Wilkerson GK, Sawyer SL. Positive selection of primate genes that promote HIV-1 replication. Virology 2014; 454-455:291-8. [PMID: 24725956 DOI: 10.1016/j.virol.2014.02.029] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 02/19/2014] [Accepted: 02/28/2014] [Indexed: 12/22/2022]
Abstract
Evolutionary analyses have revealed that most host-encoded restriction factors against HIV have experienced virus-driven selection during primate evolution. However, HIV also depends on the function of many human proteins, called host factors, for its replication. It is not clear whether virus-driven selection shapes the evolution of host factor genes to the extent that it is known to shape restriction factor genes. We show that five out of 40 HIV host factor genes (13%) analyzed do bear strong signatures of positive selection. Some of these genes (CD4, NUP153, RANBP2/NUP358) have been characterized with respect to the HIV lifecycle, while others (ANKRD30A/NY-BR-1 and MAP4) remain relatively uncharacterized. One of these, ANKRD30A, shows the most rapid evolution within this set of genes and is induced by interferon stimulation. We discuss how evolutionary analysis can aid the study of host factors for viral replication, just as it has the study of host immunity systems.
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Affiliation(s)
- Nicholas R Meyerson
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, TX 78712-1191, USA
| | - Paul A Rowley
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, TX 78712-1191, USA
| | - Christina H Swan
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, TX 78712-1191, USA; Regents School of Austin, 3230 Travis Country Circle, Austin, TX, USA
| | - Dona T Le
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, TX 78712-1191, USA
| | - Gregory K Wilkerson
- Department of Veterinary Sciences, Michale E Keeling Center for Comparative Medicine and Research, University of Texas, MD Anderson Cancer Center, Bastrop, TX, USA
| | - Sara L Sawyer
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, TX 78712-1191, USA.
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204
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Yap MW, Colbeck E, Ellis SA, Stoye JP. Evolution of the retroviral restriction gene Fv1: inhibition of non-MLV retroviruses. PLoS Pathog 2014; 10:e1003968. [PMID: 24603659 PMCID: PMC3948346 DOI: 10.1371/journal.ppat.1003968] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 01/16/2014] [Indexed: 11/18/2022] Open
Abstract
Fv1 is the prototypic restriction factor that protects against infection by the murine leukemia virus (MLV). It was first identified in cells that were derived from laboratory mice and was found to be homologous to the gag gene of an endogenous retrovirus (ERV). To understand the evolution of the host restriction gene from its retroviral origins, Fv1s from wild mice were isolated and characterized. Most of these possess intact open reading frames but not all restricted N-, B-, NR-or NB-tropic MLVs, suggesting that other viruses could have played a role in the selection of the gene. The Fv1s from Mus spretus and Mus caroli were found to restrict equine infectious anemia virus (EIAV) and feline foamy virus (FFV) respectively, indicating that Fv1 could have a broader target range than previously thought, including activity against lentiviruses and spumaviruses. Analyses of the Fv1 sequences revealed a number of residues in the C-terminal region that had evolved under positive selection. Four of these selected residues were found to be involved in the novel restriction by mapping studies. These results strengthen the similarities between the two capsid binding restriction factors, Fv1 and TRIM5α, which support the hypothesis that Fv1 defended mice against waves of retroviral infection possibly including non-MLVs as well as MLVs. We have followed the evolution of the retroviral restriction gene, Fv1, by functional analysis. We show that Fv1 can recognize and restrict a wider range of retroviruses than previously thought including examples from the gammaretrovirus, lentivirus and foamy virus genera. Nearly every Fv1 tested showed a different pattern of restriction activity. We also identify several hypervariable regions in the coding sequence containing positively selected amino acids that we show to be directly involved in determining restriction specificity. Our results strengthen the analogy between Fv1 and another capsid-binding, retrovirus restriction factor, TRIM5α. Although they share no sequence identity they appear to share a similar design and appear likely to recognise different targets by a mechanism involving multiple weak interactions between a virus-binding domain containing several variable regions and the surface of the viral capsid. We also describe a pattern of constant genetic change, implying that different species of Mus have evolved in the face of ever-changing retroviral threats by viruses of different kinds.
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Affiliation(s)
- Melvyn W. Yap
- Division of Virology, National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Emily Colbeck
- Division of Virology, National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Scott A. Ellis
- Division of Virology, National Institute for Medical Research, Mill Hill, London, United Kingdom
| | - Jonathan P. Stoye
- Division of Virology, National Institute for Medical Research, Mill Hill, London, United Kingdom
- Faculty of Medicine, Imperial College London, London, United Kingdom
- * E-mail:
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205
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Human endogenous retrovirus HERV-Fc1 association with multiple sclerosis susceptibility: a meta-analysis. PLoS One 2014; 9:e90182. [PMID: 24594754 PMCID: PMC3971560 DOI: 10.1371/journal.pone.0090182] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 01/27/2014] [Indexed: 01/07/2023] Open
Abstract
Background Human endogenous retroviruses (HERVs) are repetitive sequences derived from ancestral germ-line infections by exogenous retroviruses and different HERV families have been integrated in the genome. HERV-Fc1 in chromosome X has been previously associated with multiple sclerosis (MS) in Northern European populations. Additionally, HERV-Fc1 RNA levels of expression have been found increased in plasma of MS patients with active disease. Considering the North-South latitude gradient in MS prevalence, we aimed to evaluate the role of HERV-Fc1on MS risk in three independent Spanish cohorts. Methods A single nucleotide polymorphism near HERV-Fc1, rs391745, was genotyped by Taqman chemistry in a total of 2473 MS patients and 3031 ethnically matched controls, consecutively recruited from: Northern (569 patients and 980 controls), Central (883 patients and 692 controls) and Southern (1021 patients and 1359 controls) Spain. Our results were pooled in a meta-analysis with previously published data. Results Significant associations of the HERV-Fc1 polymorphism with MS were observed in two Spanish cohorts and the combined meta-analysis with previous data yielded a significant association [rs391745 C-allele carriers: pM-H = 0.0005; ORM-H (95% CI) = 1.27 (1.11–1.45)]. Concordantly to previous findings, when the analysis was restricted to relapsing remitting and secondary progressive MS samples, a slight enhancement in the strength of the association was observed [pM-H = 0.0003, ORM-H (95% CI) = 1.32 (1.14–1.53)]. Conclusion Association of the HERV-Fc1 polymorphism rs391745 with bout-onset MS susceptibility was confirmed in Southern European cohorts.
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206
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Cui J, Zhao W, Huang Z, Jarvis ED, Gilbert MTP, Walker PJ, Holmes EC, Zhang G. Low frequency of paleoviral infiltration across the avian phylogeny. Genome Biol 2014; 15:539. [PMID: 25496498 PMCID: PMC4272516 DOI: 10.1186/s13059-014-0539-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 11/10/2014] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND Mammalian genomes commonly harbor endogenous viral elements. Due to a lack of comparable genome-scale sequence data, far less is known about endogenous viral elements in avian species, even though their small genomes may enable important insights into the patterns and processes of endogenous viral element evolution. RESULTS Through a systematic screening of the genomes of 48 species sampled across the avian phylogeny we reveal that birds harbor a limited number of endogenous viral elements compared to mammals, with only five viral families observed: Retroviridae, Hepadnaviridae, Bornaviridae, Circoviridae, and Parvoviridae. All nonretroviral endogenous viral elements are present at low copy numbers and in few species, with only endogenous hepadnaviruses widely distributed, although these have been purged in some cases. We also provide the first evidence for endogenous bornaviruses and circoviruses in avian genomes, although at very low copy numbers. A comparative analysis of vertebrate genomes revealed a simple linear relationship between endogenous viral element abundance and host genome size, such that the occurrence of endogenous viral elements in bird genomes is 6- to 13-fold less frequent than in mammals. CONCLUSIONS These results reveal that avian genomes harbor relatively small numbers of endogenous viruses, particularly those derived from RNA viruses, and hence are either less susceptible to viral invasions or purge them more effectively.
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Affiliation(s)
- Jie Cui
- />Marie Bashir Institute for Infectious Diseases and Biosecurity, Charles Perkins Centre, School of Biological Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006 Australia
- />Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore, 169857 Singapore
| | - Wei Zhao
- />China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
| | - Zhiyong Huang
- />China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
| | - Erich D Jarvis
- />Howard Hughes Medical Institute, Duke University Medical Center, Department of Neurobiology, Box 3209, Durham, North Carolina 27710 USA
| | - M Thomas P Gilbert
- />Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark
- />Trace and Environmental DNA Laboratory, Department of Environment and Agriculture, Curtin University, Perth, Western Australia 6102 Australia
| | - Peter J Walker
- />CSIRO Animal, Food and Health Sciences, Australian Animal Health Laboratory, Geelong, Victoria 3220 Australia
| | - Edward C Holmes
- />Marie Bashir Institute for Infectious Diseases and Biosecurity, Charles Perkins Centre, School of Biological Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006 Australia
| | - Guojie Zhang
- />China National GeneBank, BGI-Shenzhen, Shenzhen, 518083 China
- />Centre for Social Evolution, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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207
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Zhang A, Dong B, Doucet AJ, Moldovan JB, Moran JV, Silverman RH. RNase L restricts the mobility of engineered retrotransposons in cultured human cells. Nucleic Acids Res 2013; 42:3803-20. [PMID: 24371271 PMCID: PMC3973342 DOI: 10.1093/nar/gkt1308] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Retrotransposons are mobile genetic elements, and their mobility can lead to genomic instability. Retrotransposon insertions are associated with a diverse range of sporadic diseases, including cancer. Thus, it is not a surprise that multiple host defense mechanisms suppress retrotransposition. The 2′,5′-oligoadenylate (2-5A) synthetase (OAS)-RNase L system is a mechanism for restricting viral infections during the interferon antiviral response. Here, we investigated a potential role for the OAS-RNase L system in the restriction of retrotransposons. Expression of wild type (WT) and a constitutively active form of RNase L (NΔ385), but not a catalytically inactive RNase L mutant (R667A), impaired the mobility of engineered human LINE-1 (L1) and mouse intracisternal A-type particle retrotransposons in cultured human cells. Furthermore, WT RNase L, but not an inactive RNase L mutant (R667A), reduced L1 RNA levels and subsequent expression of the L1-encoded proteins (ORF1p and ORF2p). Consistently, confocal immunofluorescent microscopy demonstrated that WT RNase L, but not RNase L R667A, prevented formation of L1 cytoplasmic foci. Finally, siRNA-mediated depletion of endogenous RNase L in a human ovarian cancer cell line (Hey1b) increased the levels of L1 retrotransposition by ∼2-fold. Together, these data suggest that RNase L might function as a suppressor of structurally distinct retrotransposons.
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Affiliation(s)
- Ao Zhang
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland Clinic, Cleveland, OH, 44195, USA, Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA, Department of Human Genetics, Ann Arbor, MI 48109, USA, Cellular and Molecular Biology Program, Ann Arbor, MI 48109, USA, Department of Internal Medicine, Ann Arbor, MI 48109, USA and Howard Hughes Medical Institute, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA
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208
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Hayward A, Grabherr M, Jern P. Broad-scale phylogenomics provides insights into retrovirus-host evolution. Proc Natl Acad Sci U S A 2013; 110:20146-51. [PMID: 24277832 PMCID: PMC3864273 DOI: 10.1073/pnas.1315419110] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Genomic data provide an excellent resource to improve understanding of retrovirus evolution and the complex relationships among viruses and their hosts. In conjunction with broad-scale in silico screening of vertebrate genomes, this resource offers an opportunity to complement data on the evolution and frequency of past retroviral spread and so evaluate future risks and limitations for horizontal transmission between different host species. Here, we develop a methodology for extracting phylogenetic signal from large endogenous retrovirus (ERV) datasets by collapsing information to facilitate broad-scale phylogenomics across a wide sample of hosts. Starting with nearly 90,000 ERVs from 60 vertebrate host genomes, we construct phylogenetic hypotheses and draw inferences regarding the designation, host distribution, origin, and transmission of the Gammaretrovirus genus and associated class I ERVs. Our results uncover remarkable depths in retroviral sequence diversity, supported within a phylogenetic context. This finding suggests that current infectious exogenous retrovirus diversity may be underestimated, adding credence to the possibility that many additional exogenous retroviruses may remain to be discovered in vertebrate taxa. We demonstrate a history of frequent horizontal interorder transmissions from a rodent reservoir and suggest that rats may have acted as important overlooked facilitators of gammaretrovirus spread across diverse mammalian hosts. Together, these results demonstrate the promise of the methodology used here to analyze large ERV datasets and improve understanding of retroviral evolution and diversity for utilization in wider applications.
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Affiliation(s)
- Alexander Hayward
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala Biomedical Centre, SE-75123 Uppsala, Sweden
| | - Manfred Grabherr
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala Biomedical Centre, SE-75123 Uppsala, Sweden
| | - Patric Jern
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala Biomedical Centre, SE-75123 Uppsala, Sweden
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209
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Differentiation-defective phenotypes revealed by large-scale analyses of human pluripotent stem cells. Proc Natl Acad Sci U S A 2013; 110:20569-74. [PMID: 24259714 DOI: 10.1073/pnas.1319061110] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We examined the gene expression and DNA methylation of 49 human induced pluripotent stem cells (hiPSCs) and 10 human embryonic stem cells and found overlapped variations in gene expression and DNA methylation in the two types of human pluripotent stem cell lines. Comparisons of the in vitro neural differentiation of 40 hiPSCs and 10 human embryonic stem cells showed that seven hiPSC clones retained a significant number of undifferentiated cells even after neural differentiation culture and formed teratoma when transplanted into mouse brains. These differentiation-defective hiPSC clones were marked by higher expression levels of several genes, including those expressed from long terminal repeats of specific human endogenous retroviruses. These data demonstrated a subset of hiPSC lines that have aberrant gene expression and defective potential in neural differentiation, which need to be identified and eliminated before applications in regenerative medicine.
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210
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Chudak C, Beimforde N, George M, Zimmermann A, Lausch V, Hanke K, Bannert N. Identification of late assembly domains of the human endogenous retrovirus-K(HML-2). Retrovirology 2013; 10:140. [PMID: 24252269 PMCID: PMC3874623 DOI: 10.1186/1742-4690-10-140] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 11/11/2013] [Indexed: 11/10/2022] Open
Abstract
Background Late assembly (L)-domains are protein interaction motifs, whose dysfunction causes characteristic budding defects in enveloped viruses. Three different amino acid motifs, namely PT/SAP, PPXY and YPXnL have been shown to play a major role in the release of exogenous retroviruses. Although the L-domains of exogenous retroviruses have been studied comprehensively, little is known about these motifs in endogenous human retroviruses. Results Using a molecular clone of the human endogenous retrovirus K113 that had been engineered to reverse the presumed non-synonymous postinsertional mutations in the major genes, we identified three functional L-domains of the virus, all located in the Gag p15 protein. A consensus PTAP tetrapeptide serves as the core of a main L-domain for the virus and its inactivation reduces virus release in HEK 293T cells by over 80%. Electron microscopy of cells expressing the PTAP mutant revealed predominantly late budding structures and budding chains at the plasma membrane. The fact that this motif determines subcellular colocalization with Tsg101, an ESCRT-I complex protein known to bind to the core tetrapeptide, supports its role as an L-domain. Moreover, two YPXnL motifs providing additional L-domain function were identified in the p15 protein. One is adjacent to the PTAP sequence and the other is in the p15 N-terminus. Mutations in either motif diminishes virus release and induces an L-domain phenotype while inactivation of all three L-domains results in a complete loss of particle release in HEK 293T cells. The flexibility of the virus in the use of L-domains for gaining access to the ESCRT machinery is demonstrated by overexpression of Tsg101 which rescues the release of the YPXnL mutants. Similarly, overexpression of Alix not only enhances release of the PTAP mutant by a factor of four but also the release of a triple mutant, indicating that additional cryptic YPXnL domains with a low affinity for Alix may be present. No L-domain activity is provided by the proline-rich peptides at the Gag C-terminus. Conclusions Our data demonstrate that HERV-K(HML-2) release is predominantly mediated through a consensus PTAP motif and two auxiliary YPXnL motifs in the p15 protein of the Gag precursor.
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Affiliation(s)
| | | | | | | | | | | | - Norbert Bannert
- Department for HIV and other Retroviruses, Robert Koch Institute, Nordufer 20, 13353 Berlin, Germany.
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211
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RNA in unexpected places: long non-coding RNA functions in diverse cellular contexts. Nat Rev Mol Cell Biol 2013; 14:699-712. [PMID: 24105322 DOI: 10.1038/nrm3679] [Citation(s) in RCA: 1106] [Impact Index Per Article: 100.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The increased application of transcriptome-wide profiling approaches has led to an explosion in the number of documented long non-coding RNAs (lncRNAs). While these new and enigmatic players in the complex transcriptional milieu are encoded by a significant proportion of the genome, their functions are mostly unknown. Early discoveries support a paradigm in which lncRNAs regulate transcription via chromatin modulation, but new functions are steadily emerging. Given the biochemical versatility of RNA, lncRNAs may be used for various tasks, including post-transcriptional regulation, organization of protein complexes, cell-cell signalling and allosteric regulation of proteins.
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212
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Maliniemi P, Vincendeau M, Mayer J, Frank O, Hahtola S, Karenko L, Carlsson E, Mallet F, Seifarth W, Leib-Mösch C, Ranki A. Expression of human endogenous retrovirus-w including syncytin-1 in cutaneous T-cell lymphoma. PLoS One 2013; 8:e76281. [PMID: 24098463 PMCID: PMC3788054 DOI: 10.1371/journal.pone.0076281] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 08/22/2013] [Indexed: 12/03/2022] Open
Abstract
The pathomechanism of mycosis fungoides (MF), the most common type of primary cutaneous T-cell lymphomas (CTCLs) and a malignancy of non-recirculating, skin-resident T-cells, is unknown albeit underlying viral infections have been sought for. Human endogenous retroviruses (HERVs) are ancient retroviral sequences in the human genome and their transcription is often deregulated in cancers. We explored the transcriptional activity of HERV sequences in a total of 34 samples comprising MF and psoriasis skin lesions, as well as corresponding non-malignant skin using a retrovirus-specific microarray and quantitative RT-PCR. To identify active HERV-W loci, we cloned the HERV-W specific RT-PCR products, sequenced the cDNA clones and assigned the sequences to HERV-W loci. Finally, we used immunohistochemistry on MF patient and non-malignant inflammatory skin samples to confirm specific HERV-encoded protein expression. Firstly, a distinct, skin-specific transcription profile consisting of five constitutively active HERV groups was established. Although individual variability was common, HERV-W showed significantly increased transcription in MF lesions compared to clinically intact skin from the same patient. Predominantly transcribed HERV-W loci were found to be located in chromosomes 6q21 and 7q21.2, chromosomal regions typically altered in CTCL. Surprisingly, we also found the expression of 7q21.2/ERVWE1-encoded Syncytin-1 (Env) protein in MF biopsies and expression of Syncytin-1 was seen in malignant lymphocytes, especially in the epidermotropic ones, in 15 of 30 cases studied. Most importantly, no Syncytin-1 expression was detected in inflammatory dermatosis (Lichen ruber planus) with skin-homing, non-malignant T lymphocytes. The expression of ERVWE1 mRNA was further confirmed in 3/7 MF lesions analyzed. Our observations strengthen the association between activated HERVs and cancer. The study offers a new perspective into the pathogenesis of CTCL since we demonstrate that differences in HERV-W transcription levels between lesional MF and non-malignant skin are significant, and that ERVWE1-encoded Syncytin-1 is expressed in MF lymphoma cells.
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Affiliation(s)
- Pilvi Maliniemi
- Department of Dermatology and Allergology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland
- * E-mail:
| | - Michelle Vincendeau
- Institute of Virology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Research Unit Cellular Signal Integration, Institute of Molecular Toxicology and Pharmacology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Jens Mayer
- Department of Human Genetics, Center of Human and Molecular Biology, Medical Faculty, University of Saarland, Homburg, Germany
| | - Oliver Frank
- Department of Hematology and Oncology, Mannheim Medical Center, University of Heidelberg, Mannheim, Germany
| | - Sonja Hahtola
- Department of Dermatology and Allergology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland
| | - Leena Karenko
- Department of Dermatology and Allergology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland
| | - Emilia Carlsson
- Department of Dermatology and Allergology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland
| | - Francois Mallet
- Joint Unit Hospices Civils de Lyon-bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, Pierre Bénite, France
| | - Wolfgang Seifarth
- Department of Hematology and Oncology, Mannheim Medical Center, University of Heidelberg, Mannheim, Germany
| | - Christine Leib-Mösch
- Institute of Virology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Department of Hematology and Oncology, Mannheim Medical Center, University of Heidelberg, Mannheim, Germany
| | - Annamari Ranki
- Department of Dermatology and Allergology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland
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Abstract
The mammalian placenta exhibits elevated expression of endogenous retroviruses (ERVs), but the evolutionary significance of this feature remains unclear. I propose that ERV-mediated regulatory evolution was, and continues to be, an important mechanism underlying the evolution of placental development. Many recent studies have focused on the co-option of ERV-derived genes for specific functional adaptations in the placenta. However, the co-option of ERV-derived regulatory elements could potentially lead to the incorporation of entire gene regulatory networks, which, I argue, would facilitate relatively rapid developmental evolution of the placenta. I suggest a model in which an ancient retroviral infection led to the establishment of the ancestral placental developmental gene network through the co-option of ERV-derived regulatory elements. Consequently, placental development would require elevated tolerance to ERV activity. This in turn would expose a continuous stream of novel ERV mutations that may have catalyzed the developmental diversification of the mammalian placenta.
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Affiliation(s)
- Edward B Chuong
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
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214
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Yap MW, Stoye JP. Apparent effect of rabbit endogenous lentivirus type K acquisition on retrovirus restriction by lagomorph Trim5αs. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120498. [PMID: 23938750 PMCID: PMC3758185 DOI: 10.1098/rstb.2012.0498] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To test the hypothesis that rabbit endogenous lentivirus type K (RELIK) could play a role in shaping the evolution of TRIM5α, the susceptibility of viruses containing the RELIK capsid (CA) to TRIM5 restriction was evaluated. RELIK CA-containing viruses were susceptible to the TRIM5αs from Old World monkeys but were unaffected by most ape or New World monkey factors. TRIM5αs from various lagomorph species were also isolated and tested for anti-retroviral activity. The TRIM5αs from both cottontail rabbit and pika restrict a range of retroviruses, including HIV-1, HIV-2, FIV, EIAV and N-MLV. TRIM5αs from the European and cottontail rabbit, which have previously been found to contain RELIK, also restricted RELIK CA-containing viruses, whereas a weaker restriction was observed with chimeric TRIM5α containing the B30.2 domain from the pika, which lacks RELIK. Taken together, these results could suggest that the pika had not been exposed to exogenous RELIK and that endogenized RELIK might exert a selective pressure on lagomorph TRIM5α.
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Affiliation(s)
| | - Jonathan P. Stoye
- Division of Virology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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215
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Sanz-Ramos M, Stoye JP. Capsid-binding retrovirus restriction factors: discovery, restriction specificity and implications for the development of novel therapeutics. J Gen Virol 2013; 94:2587-2598. [PMID: 24026671 DOI: 10.1099/vir.0.058180-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The development of drugs against human immunodeficiency virus type 1 infection has been highly successful, and numerous combinational treatments are currently available. However, the risk of the emergence of resistance and the toxic effects associated with prolonged use of antiretroviral therapies have emphasized the need to consider alternative approaches. One possible area of investigation is provided by the properties of restriction factors, cellular proteins that protect organisms against retroviral infection. Many show potent viral inhibition. Here, we describe the discovery, properties and possible therapeutic uses of the group of restriction factors known to interact with the capsid core of incoming retroviruses. This group comprises Fv1, TRIM5α and TRIMCypA: proteins that all act shortly after virus entry into the target cell and block virus replication at different stages prior to integration of viral DNA into the host chromosome. They have different origins and specificities, but share general structural features required for restriction, with an N-terminal multimerization domain and a C-terminal capsid-binding domain. Their overall efficacy makes it reasonable to ask whether they might provide a framework for developing novel antiretroviral strategies.
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Affiliation(s)
- Marta Sanz-Ramos
- Division of Virology, MRC National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
| | - Jonathan P Stoye
- Department of Medicine, Imperial College London, London W2 1PG, UK.,Division of Virology, MRC National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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216
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Schmitt K, Reichrath J, Roesch A, Meese E, Mayer J. Transcriptional profiling of human endogenous retrovirus group HERV-K(HML-2) loci in melanoma. Genome Biol Evol 2013; 5:307-28. [PMID: 23338945 PMCID: PMC3590776 DOI: 10.1093/gbe/evt010] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent studies suggested a role for the human endogenous retrovirus (HERV) group HERV-K(HML-2) in melanoma because of upregulated transcription and expression of HERV-K(HML-2)-encoded proteins. Very little is known about which HML-2 loci are transcribed in melanoma. We assigned >1,400 HML-2 cDNA sequences generated from various melanoma and related samples to genomic HML-2 loci, identifying a total of 23 loci as transcribed. Transcription profiles of loci differed significantly between samples. One locus was found transcribed only in melanoma-derived samples but not in melanocytes and might represent a marker for melanoma. Several of the transcribed loci harbor ORFs for retroviral Gag and/or Env proteins. Env-encoding loci were transcribed only in melanoma. Specific investigation of rec and np9 transcripts indicated transcription of protein encoding loci in melanoma and melanocytes hinting at the relevance of Rec and Np9 in melanoma. UVB irradiation changed transcription profiles of loci and overall transcript levels decreased in melanoma and melanocytes. We further identified transcribed HML-2 loci formed by reverse transcription of spliced HML-2 transcripts by L1 machinery or in a retroviral fashion, with loci potentially encoding HML-2-like proteins. We reveal complex, sample-specific transcription of HML-2 loci in melanoma and related samples. Identified HML-2 loci and proteins encoded by those loci are particularly relevant for further studying the role of HML-2 in melanoma. Transcription of HERVs appears as a complex mechanism requiring specific studies to elucidate which HERV loci are transcribed and how transcribed HERVs may be involved in disease.
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Affiliation(s)
- Katja Schmitt
- Institute of Human Genetics, Medical Faculty, University of Saarland, Homburg/Saar, Germany
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217
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Niewiadomska AM, Gifford RJ. The extraordinary evolutionary history of the reticuloendotheliosis viruses. PLoS Biol 2013; 11:e1001642. [PMID: 24013706 PMCID: PMC3754887 DOI: 10.1371/journal.pbio.1001642] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 07/19/2013] [Indexed: 11/18/2022] Open
Abstract
The reticuloendotheliosis viruses (REVs) comprise several closely related amphotropic retroviruses isolated from birds. These viruses exhibit several highly unusual characteristics that have not so far been adequately explained, including their extremely close relationship to mammalian retroviruses, and their presence as endogenous sequences within the genomes of certain large DNA viruses. We present evidence for an iatrogenic origin of REVs that accounts for these phenomena. Firstly, we identify endogenous retroviral fossils in mammalian genomes that share a unique recombinant structure with REVs-unequivocally demonstrating that REVs derive directly from mammalian retroviruses. Secondly, through sequencing of archived REV isolates, we confirm that contaminated Plasmodium lophurae stocks have been the source of multiple REV outbreaks in experimentally infected birds. Finally, we show that both phylogenetic and historical evidence support a scenario wherein REVs originated as mammalian retroviruses that were accidentally introduced into avian hosts in the late 1930s, during experimental studies of P. lophurae, and subsequently integrated into the fowlpox virus (FWPV) and gallid herpesvirus type 2 (GHV-2) genomes, generating recombinant DNA viruses that now circulate in wild birds and poultry. Our findings provide a novel perspective on the origin and evolution of REV, and indicate that horizontal gene transfer between virus families can expand the impact of iatrogenic transmission events.
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Affiliation(s)
| | - Robert J. Gifford
- Aaron Diamond AIDS Research Center, New York, New York, United States of America
- * E-mail:
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218
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Abstract
Endogenous retrovirus (ERV) genomes integrated into the chromosomal DNA of the host were first detected in chickens and mice as Mendelian determinants of Gag and Env proteins and of the release of infectious virus particles. The presence of ERV was confirmed by DNA hybridization. With complete host genomes available for analysis, we can now see the great extent of viral invasion into the genomes of numerous vertebrate species, including humans. ERVs are found at many loci in host DNA and also in the genomes of large DNA viruses, such as herpesviruses and poxviruses. The evolution of xenotropism and cross-species infection is discussed in the light of the dynamic relationship between exogenous and endogenous retroviruses.
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Affiliation(s)
- Robin A Weiss
- Division of Infection and Immunity, Wohl Virion Centre, University College London, , Cruciform Building, Gower Street, London WC1 6BT, UK
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219
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Lavialle C, Cornelis G, Dupressoir A, Esnault C, Heidmann O, Vernochet C, Heidmann T. Paleovirology of 'syncytins', retroviral env genes exapted for a role in placentation. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120507. [PMID: 23938756 DOI: 10.1098/rstb.2012.0507] [Citation(s) in RCA: 259] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The development of the emerging field of 'paleovirology' allows biologists to reconstruct the evolutionary history of fossil endogenous retroviral sequences integrated within the genome of living organisms and has led to the retrieval of conserved, ancient retroviral genes 'exapted' by ancestral hosts to fulfil essential physiological roles, syncytin genes being undoubtedly among the most remarkable examples of such a phenomenon. Indeed, syncytins are 'new' genes encoding proteins derived from the envelope protein of endogenous retroviral elements that have been captured and domesticated on multiple occasions and independently in diverse mammalian species, through a process of convergent evolution. Knockout of syncytin genes in mice provided evidence for their absolute requirement for placenta development and embryo survival, via formation by cell-cell fusion of syncytial cell layers at the fetal-maternal interface. These genes of exogenous origin, acquired 'by chance' and yet still 'necessary' to carry out a basic function in placental mammals, may have been pivotal in the emergence of mammalian ancestors with a placenta from egg-laying animals via the capture of a founding retroviral env gene, subsequently replaced in the diverse mammalian lineages by new env-derived syncytin genes, each providing its host with a positive selective advantage.
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Affiliation(s)
- Christian Lavialle
- UMR 8122, Unité des Rétrovirus Endogènes et Éléments Rétroïdes des Eucaryotes Supérieurs, CNRS, Institut Gustave Roussy, , 94805 Villejuif, France
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220
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Involvement of endogenous retroviruses in prion diseases. Pathogens 2013; 2:533-43. [PMID: 25437206 PMCID: PMC4235691 DOI: 10.3390/pathogens2030533] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 07/25/2013] [Accepted: 08/09/2013] [Indexed: 11/17/2022] Open
Abstract
For millions of years, vertebrates have been continuously exposed to infection by retroviruses. Ancient retroviral infection of germline cells resulted in the formation and accumulation of inherited retrovirus sequences in host genomes. These inherited retroviruses are referred to as endogenous retroviruses (ERVs), and recent estimates have revealed that a significant portion of animal genomes is made up of ERVs. Although various host factors have suppressed ERV activation, both positive and negative functions have been reported for some ERVs in normal and abnormal physiological conditions, such as in disease states. Similar to other complex diseases, ERV activation has been observed in prion diseases, and this review will discuss the potential involvement of ERVs in prion diseases.
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221
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Young GR, Stoye JP, Kassiotis G. Are human endogenous retroviruses pathogenic? An approach to testing the hypothesis. Bioessays 2013; 35:794-803. [PMID: 23864388 PMCID: PMC4352332 DOI: 10.1002/bies.201300049] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A number of observations have led researchers to postulate that, despite being replication-defective, human endogenous retroviruses (HERVs) may have retained the potential to cause or contribute to disease. However, mechanisms of HERV pathogenicity might differ substantially from those of modern infectious retroviruses or of the infectious precursors of HERVs. Therefore, novel pathways of HERV involvement in disease pathogenesis should be investigated. Recent technological advances in sequencing and bioinformatics are making this task increasingly feasible. The accumulating knowledge of HERV biology may also facilitate the definition and general acceptance of criteria that establish HERV pathogenicity. Here, we explore possible mechanisms whereby HERVs may cause disease and examine the evidence that either has been or should be obtained in order to decisively address the pathogenic potential of HERVs.
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Affiliation(s)
- George R Young
- Division of Virology, MRC National Institute for Medical Research, London, UK
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222
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Schlesinger S, Lee AH, Wang GZ, Green L, Goff SP. Proviral silencing in embryonic cells is regulated by Yin Yang 1. Cell Rep 2013; 4:50-8. [PMID: 23810560 DOI: 10.1016/j.celrep.2013.06.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 03/20/2013] [Accepted: 06/03/2013] [Indexed: 12/25/2022] Open
Abstract
Embryonic cells transcriptionally repress the expression of endogenous and exogenous retroelements. Trim28, a key player in this silencing, is known to act in a large DNA-bound complex, but the other components of the complex are not fully characterized. Here, we show that the zinc finger protein Yin Yang 1 (YY1) is one such component. YY1 binds to the long terminal repeat (LTR) region of both exogenous and endogenous retroviruses (ERVs). Deletion of the YY1-binding site from the retroviral genome leads to a major loss of silencing in embryonic cells and a coordinated loss of repressive histone marks from the proviral chromatin. Depletion of YY1 protein results in marked upregulation of expression of exogenous viruses and of selected ERVs. Finally, we report an embryonic cell-specific interaction between YY1 and Trim28. Our results suggest a major role for YY1 in the silencing of both exogenous retroviruses and ERVs in embryonic cells.
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Affiliation(s)
- Sharon Schlesinger
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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223
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Gallo PM, Gallucci S. The dendritic cell response to classic, emerging, and homeostatic danger signals. Implications for autoimmunity. Front Immunol 2013; 4:138. [PMID: 23772226 PMCID: PMC3677085 DOI: 10.3389/fimmu.2013.00138] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 05/23/2013] [Indexed: 12/18/2022] Open
Abstract
Dendritic cells (DCs) initiate and control immune responses, participate in the maintenance of immunological tolerance and are pivotal players in the pathogenesis of autoimmunity. In patients with autoimmune disease and in experimental animal models of autoimmunity, DCs show abnormalities in both numbers and activation state, expressing immunogenic levels of costimulatory molecules and pro-inflammatory cytokines. Exogenous and endogenous danger signals activate DCs to stimulate the immune response. Classic endogenous danger signals are released, activated, or secreted by host cells and tissues experiencing stress, damage, and non-physiologic cell death; and are therefore referred to as damage-associated molecular patterns (DAMPs). Some DAMPs are released from cells, where they are normally sequestered, during necrosis (e.g., heat shock proteins, uric acid, ATP, HMGB1, mitochondria-derived molecules). Others are actively secreted, like Type I Interferons. Here we discuss important DAMPs in the context of autoimmunity. For some, there is a clear pathogenic link (e.g., nucleic acids and lupus). For others, there is less evidence. Additionally, we explore emerging danger signals. These include inorganic materials and man-made technologies (e.g., nanomaterials) developed as novel therapeutic approaches. Some nanomaterials can activate DCs and may trigger unintended inflammatory responses. Finally, we will review “homeostatic danger signals,” danger signals that do not derive directly from pathogens or dying cells but are associated with perturbations of tissue/cell homeostasis and may signal pathological stress. These signals, like acidosis, hypoxia, and changes in osmolarity, also play a role in inflammation and autoimmunity.
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Affiliation(s)
- Paul M Gallo
- Laboratory of Dendritic Cell Biology, Department of Microbiology and Immunology, Temple Autoimmunity Center, Temple University School of Medicine , Philadelphia, PA , USA
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224
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Mavrommatis B, Young GR, Kassiotis G. Counterpoise between the microbiome, host immune activation and pathology. Curr Opin Immunol 2013; 25:456-62. [PMID: 23743081 DOI: 10.1016/j.coi.2013.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/03/2013] [Accepted: 05/08/2013] [Indexed: 12/13/2022]
Abstract
The role of the mammalian intestinal microbiota in health and disease of the host has long been recognized and extensively studied. Largely, these studies have focused on the bacterial component of the microbiota. However, recent technological advances have shed new light on the microbiome at distinct anatomical locations and uncovered the role of additional microbial symbionts, including the virome and endogenous retroelements. Together, they have revealed interactions more intricate than previously recognized. Here, we review recent advances in our knowledge of this collective microbiome and the interactions with the immune system of their host.
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Affiliation(s)
- Bettina Mavrommatis
- Division of Immunoregulation, MRC National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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225
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Demogines A, Abraham J, Choe H, Farzan M, Sawyer SL. Dual host-virus arms races shape an essential housekeeping protein. PLoS Biol 2013; 11:e1001571. [PMID: 23723737 PMCID: PMC3665890 DOI: 10.1371/journal.pbio.1001571] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 04/17/2013] [Indexed: 02/07/2023] Open
Abstract
Relentless selective pressures exerted by viruses trigger arms race dynamics that shape the evolution of even critical host genes like those involved in iron homeostasis. Transferrin Receptor (TfR1) is the cell-surface receptor that regulates iron uptake into cells, a process that is fundamental to life. However, TfR1 also facilitates the cellular entry of multiple mammalian viruses. We use evolutionary and functional analyses of TfR1 in the rodent clade, where two families of viruses bind this receptor, to mechanistically dissect how essential housekeeping genes like TFR1 successfully balance the opposing selective pressures exerted by host and virus. We find that while the sequence of rodent TfR1 is generally conserved, a small set of TfR1 residue positions has evolved rapidly over the speciation of rodents. Remarkably, all of these residues correspond to the two virus binding surfaces of TfR1. We show that naturally occurring mutations at these positions block virus entry while simultaneously preserving iron-uptake functionalities, both in rodent and human TfR1. Thus, by constantly replacing the amino acids encoded at just a few residue positions, TFR1 divorces adaptation to ever-changing viruses from preservation of key cellular functions. These dynamics have driven genetic divergence at the TFR1 locus that now enforces species-specific barriers to virus transmission, limiting both the cross-species and zoonotic transmission of these viruses. Genetic differences between mammalian species dictate the patterns of viral infection observed in nature. They also define how viruses must evolve in order to infect new mammalian hosts, giving rise to new and sometimes pandemic diseases. Because viruses must enter cells before they can replicate, new diseases often emerge when existing viruses evolve the ability to bind to the cell-surface receptor of a new species. At the same time, host cell receptors also evolve to counteract virus attacks. This back-and-forth evolution between virus and host can lead to an arms race that shapes the sequences of the proteins involved. In wild rodent populations, the retrovirus MMTV and New World arenaviruses both exploit Transferrin Receptor 1 (TfR1) to enter the cells of their hosts. Here we show that the physical interactions between these viruses and TfR1 have triggered evolutionary arms race dynamics that have directly modified the sequence of TfR1 and at least one of the viruses involved. Computational evolutionary analysis allowed us to identify specific residues in TfR1 that define patterns of viral infection in nature. The approach presented here can theoretically be applied to the study of any virus, through analysis of host genes known to be key to controlling viral infection. As such, this approach can expand our understanding of how viruses emerge from wildlife reservoirs, and how they drive the evolution of host genes.
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Affiliation(s)
- Ann Demogines
- Department of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Jonathan Abraham
- Department of Medicine, Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Hyeryun Choe
- Department of Medicine, Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael Farzan
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Sara L. Sawyer
- Department of Molecular Genetics and Microbiology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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226
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Abstract
Viruses incorporated into vertebrate genomes may reemerge after long periods of dormancy to play a range of biological roles in their host.
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Affiliation(s)
- Robin A Weiss
- Division of Infection and Immunity, University College London, Gower Street, London WC1E 6BT, UK.
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227
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Abstract
The following state-of-the-art seminar was delivered as part of the Aspen Lung Conference on Pulmonary Hypertension and Vascular Diseases held in Aspen, Colorado in June 2012. This paper will summarize the lecture and present results from a nonhuman primate model of infection with Simian (Human) Immunodeficiency Virus - nef chimeric virions as well as the idea that polymorphisms in the HIV-1 nef gene may be driving the immune response that results in exuberant inflammation and aberrant endothelial cell (EC) function. We will present data gathered from primary HIV nef isolates where we tested the biological consequences of these polymorphisms and how their presence in human populations may predict patients at risk for developing this disease. In this article, we also discuss how a dysregulated immune system, in conjunction with a viral infection, could contribute to pulmonary arterial hypertension (PAH). Both autoimmune diseases and some viruses are associated with defects in the immune system, primarily in the function of regulatory T cells. These T-cell defects may be a common pathway in the formation of plexiform lesions. Regardless of the route by which viruses may lead to PAH, it is important to recognize their role in this rare disease.
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Affiliation(s)
- Sonia C Flores
- Section of Pulmonary Sciences and Critical Care Medicine, University of Colorado School of Medicine, Aurora, Colorado, USA
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228
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A comparison of murine leukemia viruses that escape from human and rhesus macaque TRIM5αs. J Virol 2013; 87:6455-68. [PMID: 23536686 DOI: 10.1128/jvi.03425-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To better understand the binding mechanism of TRIM5α to retrovirus capsid, we had previously selected N-tropic murine leukemia virus (N-MLV) mutants escaping from rhesus macaque TRIM5α (rhTRIM5α) by passaging the virus in rhTRIM5α-expressing cells and selecting for nonrestricted variants. To test the commonality of the findings from the rhTRIM5α study, we have now employed a similar genetic approach using human TRIM5α (huTRIM5α). Consistent with the rhTRIM5α study, the mapped huTRIM5α escape mutations were distributed across the capsid exterior, confirming the extended binding surface between virus and restriction factor. Compared to the results of the previous study, fewer escape mutations were identified, with particular mutants being repeatedly selected. Three out four huTRIM5α escape variants showed resistance to all primate TRIM5αs tested, but two of them sacrificed viral fitness, observations that were not made in the rhTRIM5α study. Moreover, differences in amino acid changes associated with escape from hu- and rhTRIM5αs suggested a charge dependence of the restriction by different TRIM5αs. Taken together, these results suggest that the recognition of the entire capsid surface is a general strategy for TRIM5α to restrict MLV but that significantly different specific interactions are involved in the binding of TRIM5α from different species to the MLV capsid core.
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229
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Hayward JA, Tachedjian M, Cui J, Field H, Holmes EC, Wang LF, Tachedjian G. Identification of diverse full-length endogenous betaretroviruses in megabats and microbats. Retrovirology 2013; 10:35. [PMID: 23537098 PMCID: PMC3621094 DOI: 10.1186/1742-4690-10-35] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 03/11/2013] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Betaretroviruses infect a wide range of species including primates, rodents, ruminants, and marsupials. They exist in both endogenous and exogenous forms and are implicated in animal diseases such as lung cancer in sheep, and in human disease, with members of the human endogenous retrovirus-K (HERV-K) group of endogenous betaretroviruses (βERVs) associated with human cancers and autoimmune diseases. To improve our understanding of betaretroviruses in an evolutionarily distinct host species, we characterized βERVs present in the genomes and transcriptomes of mega- and microbats, which are an important reservoir of emerging viruses. RESULTS A diverse range of full-length βERVs were discovered in mega- and microbat genomes and transcriptomes including the first identified intact endogenous retrovirus in a bat. Our analysis revealed that the genus Betaretrovirus can be divided into eight distinct sub-groups with evidence of cross-species transmission. Betaretroviruses are revealed to be a complex retrovirus group, within which one sub-group has evolved from complex to simple genomic organization through the acquisition of an env gene from the genus Gammaretrovirus. Molecular dating suggests that bats have contended with betaretroviral infections for over 30 million years. CONCLUSIONS Our study reveals that a diverse range of betaretroviruses have circulated in bats for most of their evolutionary history, and cluster with extant betaretroviruses of divergent mammalian lineages suggesting that their distribution may be largely unrestricted by host species barriers. The presence of βERVs with the ability to transcribe active viral elements in a major animal reservoir for viral pathogens has potential implications for public health.
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Affiliation(s)
- Joshua A Hayward
- Retroviral Biology and Antivirals Laboratory, Centre for Virology, Burnet Institute, Melbourne, VIC 3004, Australia
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230
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Strissel PL, Ruebner M, Thiel F, Wachter D, Ekici AB, Wolf F, Thieme F, Ruprecht K, Beckmann MW, Strick R. Reactivation of codogenic endogenous retroviral (ERV) envelope genes in human endometrial carcinoma and prestages: Emergence of new molecular targets. Oncotarget 2013; 3:1204-19. [PMID: 23085571 PMCID: PMC3717959 DOI: 10.18632/oncotarget.679] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Endometrial carcinoma (EnCa) is the most common invasive gynaecologic carcinoma. Over 85% of EnCa are classified as endometrioid, expressing steroid hormone receptors and mostly involving pathological prestages. Human endogenous retroviruses (ERV) are chromosomally integrated genes, account for about 8% of the human genome and are implicated in the etiology of carcinomas. The majority of ERV envelope (env) coding genes are either not present or not consistently represented between common gene expression microarrays. The aim of this study was to analyse the absolute gene expression of all known 21 ERV env genes including 19 codogenic and two env genes with premature stop codons in EnCa, endometrium as well as in hyperplasia and polyps. For EnCa seven env genes had high expression with >200 mol/ng cDNA (e.g. envH1-3, Syncytin-1, envT), two middle >50 mol/ng cDNA (envFc2, erv-3) and 12 low <50 mol/ng cDNA (e.g. Syncytin-2, envV2). Regarding tumor parameters, Syncytin-1 and Syncytin-2 were significantly over-expressed in advanced stage pT2 compared to pT1b. In less differentiated EnCa Syncytin-1, erv-3, envT and envFc2 were significantly over-expressed. Syncytin-1, Syncytin-2 and erv-3 were specific to glandular epithelial cells of polyps, hyperplasia and EnCa using immunohistochemistry. An analysis of 10 patient-matched EnCa with endometrium revealed that the ERV-W 5' long terminal repeat regulating Syncytin-1 was hypomethylated, including the ERE and CRE overlapping MeCP2 sites. Functional analyses showed that 10 env genes were regulated by methylation in EnCa using the RL95-2 cell line. In conclusion, over-expressed env genes could serve as indicators for pathological pre-stages and EnCa.
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Affiliation(s)
- Pamela L Strissel
- University-Clinic Erlangen, Department of Gynecology and Obstetrics, Laboratory for Molecular Medicine, Erlangen, Germany
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231
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Abstract
In this issue of Immunity, Yu et al. (2012) outline a fascinating model in which TLR7-mediated antibody production acts as a dominant immunosurveillance mechanism against endogenous retroviruses (ERVs), with additional support of TLR3 and TLR9 that function to prevent ERV-mediated malignancy.
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Affiliation(s)
- Arun K Mankan
- Institute for Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Bonn, Germany
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232
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Abstract
What good are transposable elements (TEs)? Although their activity can be harmful to host genomes and can cause disease, they nevertheless represent an important source of genetic variation that has helped shape genomes. In this review, we examine the impact of TEs, collectively referred to as the mobilome, on the transcriptome. We explore how TEs—particularly retrotransposons—contribute to transcript diversity and consider their potential significance as a source of small RNAs that regulate host gene transcription. We also discuss a critical role for the mobilome in engineering transcriptional networks, permitting coordinated gene expression, and facilitating the evolution of novel physiological processes.
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Affiliation(s)
- Michael Cowley
- Department of Medical & Molecular Genetics, King's College London, London, United Kingdom
| | - Rebecca J. Oakey
- Department of Medical & Molecular Genetics, King's College London, London, United Kingdom
- * E-mail:
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Cegolon L, Salata C, Weiderpass E, Vineis P, Palù G, Mastrangelo G. Human endogenous retroviruses and cancer prevention: evidence and prospects. BMC Cancer 2013; 13:4. [PMID: 23282240 PMCID: PMC3557136 DOI: 10.1186/1471-2407-13-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 12/02/2012] [Indexed: 12/05/2022] Open
Abstract
Background Cancer is a significant and growing problem worldwide. While this increase may, in part, be attributed to increasing longevity, improved case notifications and risk-enhancing lifestyle (such as smoking, diet and obesity), hygiene-related factors resulting in immuno-regulatory failure may also play a major role and call for a revision of vaccination strategies to protect against a range of cancers in addition to infections. Discussion Human endogenous retroviruses (HERVs) are a significant component of a wider family of retroelements that constitutes part of the human genome. They were originated by the integration of exogenous retroviruses into the human genome millions of years ago. HERVs are estimated to comprise about 8% of human DNA and are ubiquitous in somatic and germinal tissues. Physiologic and pathologic processes are influenced by some biologically active HERV families. HERV antigens are only expressed at low levels by the host, but in circumstances of inappropriate control their genes may initiate or maintain pathological processes. Although the precise mechanism leading to abnormal HERVs gene expression has yet to be clearly elucidated, environmental factors seem to be involved by influencing the human immune system. HERV-K expression has been detected in different types of tumors. Among the various human endogenous retroviral families, the K series was the latest acquired by the human species. Probably because of its relatively recent origin, the HERV-K is the most complete and biologically active family. The abnormal expression of HERV-K seemingly triggers pathological processes leading to melanoma onset, but also contributes to the morphological and functional cellular modifications implicated in melanoma maintenance and progression. The HERV-K-MEL antigen is encoded by a pseudo-gene incorporated in the HERV-K env-gene. HERV-K-MEL is significantly expressed in the majority of dysplastic and normal naevi, as well as other tumors like sarcoma, lymphoma, bladder and breast cancer. An amino acid sequence similar to HERV-K-MEL, recognized to cause a significant protective effect against melanoma, is shared by the antigenic determinants expressed by some vaccines such as BCG, vaccinia virus and the yellow fever virus. HERV-K are also reactivated in the majority of human breast cancers. Monoclonal and single-chain antibodies against the HERV-K Env protein recently proved capable of blocking the proliferation of human breast cancer cells in vitro, inhibiting tumor growth in mice bearing xenograft tumors. Summary A recent epidemiological study provided provisional evidence of how melanoma risk could possibly be reduced if the yellow fever virus vaccine (YFV) were received at least 10 years before, possibly preventing tumor initiation rather than culling melanoma cells already compromised. Further research is recommended to confirm the temporal pattern of this protection and eliminate/attenuate the potential role of relevant confounders as socio-economic status and other vaccinations. It appears also appropriate to examine the potential protective effect of YFV against other malignancies expressing high levels of HERV-K antigens, namely breast cancer, sarcoma, lymphoma and bladder cancer. Tumor immune-therapy, as described for the monoclonal antibodies against breast cancer, is indeed considered more complex and less advantageous than immune-prevention. Cellular immunity possibly triggered by vaccines as for YFV might also be involved in anti-cancer response, in addition to humoral immunity.
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Affiliation(s)
- Luca Cegolon
- Department of Molecular Medicine, Padua University, Padua, Italy.
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234
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Santoni FA, Guerra J, Luban J. HERV-H RNA is abundant in human embryonic stem cells and a precise marker for pluripotency. Retrovirology 2012; 9:111. [PMID: 23253934 PMCID: PMC3558390 DOI: 10.1186/1742-4690-9-111] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 12/16/2012] [Indexed: 01/10/2023] Open
Abstract
Background Certain post-translational modifications to histones, including H3K4me3, as well as binding sites for the transcription factor STAT1, predict the site of integration of exogenous gamma-retroviruses with great accuracy and cell-type specificity. Statistical methods that were used to identify chromatin features that predict exogenous gamma-retrovirus integration site selection were exploited here to determine whether cell type-specific chromatin markers are enriched in the vicinity of endogenous retroviruses (ERVs). Results Among retro-elements in the human genome, the gamma-retrovirus HERV-H was highly associated with H3K4me3, though this association was only observed in embryonic stem (ES) cells (p < 10-300) and, to a lesser extent, in induced pluripotent stem (iPS) cells. No significant association was observed in nearly 40 differentiated cell types, nor was any association observed with other retro-elements. Similar strong association was observed between HERV-H and the binding sites within ES cells for the pluripotency transcription factors NANOG, OCT4, and SOX2. NANOG binding sites were located within the HERV-H 5′LTR itself. OCT4 and SOX2 binding sites were within 1 kB and 2 kB of the 5′LTR, respectively. In keeping with these observations, HERV-H RNA constituted 2% of all poly A RNA in ES cells. As ES cells progressed down a differentiation pathway, the levels of HERV-H RNA decreased progressively. RNA-Seq datasets showed HERV-H transcripts to be over 5 kB in length and to have the structure 5′LTR-gag-pro-3′LTR, with no evidence of splicing and no intact open reading frames. Conclusion The developmental regulation of HERV-H expression, the association of HERV-H with binding sites for pluripotency transcription factors, and the extremely high levels of HERV-H RNA in human ES cells suggest that HERV-H contributes to pluripotency in human cells. Proximity of HERV-H to binding sites for pluripotency transcription factors within ES cells might be due to retention of the same chromatin features that determined the site of integration of the ancestral, exogenous, gamma-retrovirus that gave rise to HERV-H in the distant past. Retention of these markers, or, alternatively, recruitment of them to the site of the established provirus, may have acted post-integration to fix the provirus within the germ-line of the host species. Either way, HERV-H RNA provides a specific marker for pluripotency in human cells.
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Affiliation(s)
- Federico A Santoni
- Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland.
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235
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Affiliation(s)
| | - Gavin Giovannoni
- Queen Mary University of London, Barts and The London School of Medicine, UK
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236
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Zhang Q, Rahim MMA, Allan DSJ, Tu MM, Belanger S, Abou-Samra E, Ma J, Sekhon HS, Fairhead T, Zein HS, Carlyle JR, Anderson SK, Makrigiannis AP. Mouse Nkrp1-Clr gene cluster sequence and expression analyses reveal conservation of tissue-specific MHC-independent immunosurveillance. PLoS One 2012; 7:e50561. [PMID: 23226525 PMCID: PMC3514311 DOI: 10.1371/journal.pone.0050561] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 10/23/2012] [Indexed: 01/23/2023] Open
Abstract
The Nkrp1 (Klrb1)-Clr (Clec2) genes encode a receptor-ligand system utilized by NK cells as an MHC-independent immunosurveillance strategy for innate immune responses. The related Ly49 family of MHC-I receptors displays extreme allelic polymorphism and haplotype plasticity. In contrast, previous BAC-mapping and aCGH studies in the mouse suggest the neighboring and related Nkrp1-Clr cluster is evolutionarily stable. To definitively compare the relative evolutionary rate of Nkrp1-Clr vs. Ly49 gene clusters, the Nkrp1-Clr gene clusters from two Ly49 haplotype-disparate inbred mouse strains, BALB/c and 129S6, were sequenced. Both Nkrp1-Clr gene cluster sequences are highly similar to the C57BL/6 reference sequence, displaying the same gene numbers and order, complete pseudogenes, and gene fragments. The Nkrp1-Clr clusters contain a strikingly dissimilar proportion of repetitive elements compared to the Ly49 clusters, suggesting that certain elements may be partly responsible for the highly disparate Ly49 vs. Nkrp1 evolutionary rate. Focused allelic polymorphisms were found within the Nkrp1b/d (Klrb1b), Nkrp1c (Klrb1c), and Clr-c (Clec2f) genes, suggestive of possible immune selection. Cell-type specific transcription of Nkrp1-Clr genes in a large panel of tissues/organs was determined. Clr-b (Clec2d) and Clr-g (Clec2i) showed wide expression, while other Clr genes showed more tissue-specific expression patterns. In situ hybridization revealed specific expression of various members of the Clr family in leukocytes/hematopoietic cells of immune organs, various tissue-restricted epithelial cells (including intestinal, kidney tubular, lung, and corneal progenitor epithelial cells), as well as myocytes. In summary, the Nkrp1-Clr gene cluster appears to evolve more slowly relative to the related Ly49 cluster, and likely regulates innate immunosurveillance in a tissue-specific manner.
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Affiliation(s)
- Qiang Zhang
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Mir Munir A. Rahim
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - David S. J. Allan
- Department of Immunology, University of Toronto, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Megan M. Tu
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Simon Belanger
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Elias Abou-Samra
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Jaehun Ma
- Department of Immunology, University of Toronto, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Harman S. Sekhon
- Department of Pathology and Laboratory Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada
| | - Todd Fairhead
- Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Haggag S. Zein
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
- Department of Genetics, Cairo University, Giza, Egypt
| | - James R. Carlyle
- Department of Immunology, University of Toronto, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Stephen K. Anderson
- Basic Science Program, SAIC-Frederick Inc., Laboratory of Experimental Immunology, Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
| | - Andrew P. Makrigiannis
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario, Canada
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Silencing of proviruses in embryonic cells: efficiency, stability and chromatin modifications. EMBO Rep 2012; 14:73-9. [PMID: 23154467 DOI: 10.1038/embor.2012.182] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 10/15/2012] [Accepted: 10/22/2012] [Indexed: 12/16/2022] Open
Abstract
Embryonic stem cells repress retroviral infection through transcriptional silencing of proviral DNAs. We characterized two distinct mechanisms of silencing in embryonic mouse cells infected by Moloney murine leukaemia virus (MLV): a highly efficient one targeting the proline transfer RNA primer-binding site (PBSpro), and a less efficient one operating independently of the PBS. Rare virus-expressing populations were isolated, and the timing and efficiency of establishment of silencing were determined. Superinfection of the selected virus-expressing cells with a second virus carrying a distinguishable reporter revealed that the PBSpro-directed silencing was still largely intact, whereas the PBS-independent silencing was partially reduced. The timing and stability of silencing, and the associated chromatin modifications on newly established and endogenous proviruses were determined. The results indicate that epigenetic mechanisms with different specificity and efficiency are used to silence the exogenous retroviral sequences in embryonic cells.
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HERV-E-mediated modulation of PLA2G4A transcription in urothelial carcinoma. PLoS One 2012; 7:e49341. [PMID: 23145155 PMCID: PMC3492278 DOI: 10.1371/journal.pone.0049341] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 10/09/2012] [Indexed: 12/30/2022] Open
Abstract
Human endogenous retroviruses (HERV) and related elements account for more than 8% of the human genome and significantly contribute to the human transcriptome by long terminal repeat (LTR) promoter activity. In this context, HERVs are thought to intervene in the expression of adjacent genes by providing regulatory sequences (cis-effect) or via noncoding RNA including natural antisense transcripts. To address the potential impact of HERV activity in urothelial carcinoma, we comparatively analyzed the HERV transcription profiles in paired samples of non-malignant urothelium and urothelial carcinoma derived from 13 patients with bladder cancer by means of a retrovirus-specific microarray (RetroArray). We established a characteristic HERV signature consisting of six ubiquitously active HERV subgroups (E4-1, HERV-Rb, ERV9, HERV-K-T47D, NMWV3, HERV-KC4). The transcription pattern is largely identical in human urothelial carcinoma, non-malignant urothelial tissue, four tumor-derived cell lines and in a non-malignant urothelial cell line (UROtsa). Quantitative reverse transcriptase PCR (qRT-PCR) of HERV-E4-1, HERV-K(HML-6) and HERV-T(S71-TK1) revealed a bias to lower HERV activity in carcinoma samples compared to non-malignant tissue. Determination of active HERV-E4-1 loci by cloning and sequencing revealed six HERV-E4-1 proviral loci that are differentially regulated in urothelial carcinoma cells and normal tissue. Two full-length HERV-E4-1 proviruses, HERV-Ec1 and HERV-Ec6, are located in antisense orientation in introns of the genes PLA2G4A and RNGTT, respectively. PLA2G4A encodes a cytosolic phospholipase A2 (cPLA2) that is dysregulated in many human tumors. PLA2G4A and HERV-Ec1 displayed reciprocal transcript levels in 7 of 11 urothelial carcinoma patients. Moreover, reciprocal shifts were observed after treatment of UROtsa cells with HERV-Ec1 and PLA2G4A-directed siRNAs or 5-aza-2′-deoxycytidine (aza-dC) pointing to an antagonistic regulation of PLA2G4A and HERV-Ec1 transcription in human urothelial cells. We suggest that transcription of HERV-Ec1 contributes to fine tuning of cPLA2 expression, thereby facilitating tumorigenesis.
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Young GR, Eksmond U, Salcedo R, Alexopoulou L, Stoye JP, Kassiotis G. Resurrection of endogenous retroviruses in antibody-deficient mice. Nature 2012; 491:774-8. [PMID: 23103862 PMCID: PMC3511586 DOI: 10.1038/nature11599] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 09/18/2012] [Indexed: 01/12/2023]
Abstract
The mammalian host has developed a long-standing symbiotic relationship with a considerable number of microbial species. These include the microbiota on environmental surfaces, such as the respiratory and gastrointestinal tracks1, and also endogenous retroviruses (ERVs), comprising a substantial fraction of the mammalian genome2,3. The long-term consequences for the host of interaction with these microbial species can range from mutualism to parasitism and are not always completely understood. The potential impact of one microbial symbiont on another is even less clear. We have studied the control of ERVs in the commonly-used C57BL/6 (B6) mouse strain, which lacks endogenous murine leukaemia viruses (MLVs) able to replicate in murine cells. We demonstrate the spontaneous emergence of fully infectious ecotropic4 MLV (eMLV) in B6 mice with a range of distinct immune deficiencies affecting antibody production. These recombinant retroviruses establish infection of immunodeficient mouse colonies, and ultimately result in retrovirus-induced lymphomas. Notably, ERV activation in immune-deficient mice is prevented in husbandry conditions associated with reduced or absent intestinal microbiota. Our results shed light onto a previously unappreciated role for immunity in the control of ERVs and provide a potential mechanistic link between immune activation by microbial triggers and a range of pathologies associated with ERVs, including cancer.
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Affiliation(s)
- George R Young
- Division of Immunoregulation, MRC National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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Abstract
Endogenous retroviruses (ERVs) were identified and characterized in three avian genomes to gain insight into early retroviral evolution. Using the computer program RetroTector to detect relatively intact ERVs, we identified 500 ERVs in the chicken genome, 150 in the turkey genome, and 1,200 in the zebra finch genome. Previous studies suggested that endogenous alpharetroviruses were present in chicken genomes. In this analysis, a small number of alpharetroviruses were seen in the chicken and turkey genomes; however, these were greatly outnumbered by beta-like, gamma-like, and alphabeta proviruses. While the avian ERVs belonged to the same major groups as mammalian ERVs, they were more heterogeneous. In particular, the beta-like viruses revealed an evolutionary continuum with the gradual acquisition and loss of betaretroviral markers and a transition from beta to alphabeta and then to alpharetroviruses. Thus, it appears that birds may resemble a melting pot for early ERV evolution. Many of the ERVs were integrated in clusters on chromosomes, often near centromeres. About 25% of the chicken ERVs were in or near cellular transcription units; this is nearly random. The majority of these integrations were in the sense orientation in introns. A higher-than-random number of integrations were >100 kb from the nearest gene. Deep-sequencing studies of chicken embryo fibroblasts revealed that about 20% of the 500 ERVs were transcribed and translated. A subset of these were also transcribed in vivo in chickens, showing tissue-specific patterns of expression. IMPORTANCE Studies of avian endogenous retroviruses (ERVs) have given us a glimpse of an earlier retroviral world. Three different classes of ERVs were observed with many features of mammalian retroviruses, as well as some important differences. Many avian ERVs were transcribed and translated.
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241
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Aswad A, Katzourakis A. Paleovirology and virally derived immunity. Trends Ecol Evol 2012; 27:627-36. [PMID: 22901901 DOI: 10.1016/j.tree.2012.07.007] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 07/11/2012] [Accepted: 07/16/2012] [Indexed: 01/04/2023]
Abstract
Paleovirology, the study of viruses on evolutionary timescales, can exploit information from endogenous viral elements (EVEs), which are the result of heritable horizontal gene transfer (HGT) from viruses to hosts. The availability of genomic data has increased opportunities to study EVEs, and bioinformatics techniques have been crucial in cataloguing EVE diversity and taxonomic coverage. Recent advances show that some EVEs have been co-opted as cellular genes, often as inhibitors of viral infection. These genes are an intriguing strategy in virus-host evolutionary battles in that genetic material is transferred from virus to host, and then used by the host against the virus. In this review, we consider the genes and processes involved in EVE-derived immunity (EDI), assess factors leading to its emergence, and outline how future work will benefit from incorporating evolutionary approaches.
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Affiliation(s)
- Amr Aswad
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK
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