1
|
Stricker E, Peckham-Gregory EC, Scheurer ME. HERVs and Cancer-A Comprehensive Review of the Relationship of Human Endogenous Retroviruses and Human Cancers. Biomedicines 2023; 11:936. [PMID: 36979914 PMCID: PMC10046157 DOI: 10.3390/biomedicines11030936] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/03/2023] [Accepted: 03/10/2023] [Indexed: 03/30/2023] Open
Abstract
Genomic instability and genetic mutations can lead to exhibition of several cancer hallmarks in affected cells such as sustained proliferative signaling, evasion of growth suppression, activated invasion, deregulation of cellular energetics, and avoidance of immune destruction. Similar biological changes have been observed to be a result of pathogenic viruses and, in some cases, have been linked to virus-induced cancers. Human endogenous retroviruses (HERVs), once external pathogens, now occupy more than 8% of the human genome, representing the merge of genomic and external factors. In this review, we outline all reported effects of HERVs on cancer development and discuss the HERV targets most suitable for cancer treatments as well as ongoing clinical trials for HERV-targeting drugs. We reviewed all currently available reports of the effects of HERVs on human cancers including solid tumors, lymphomas, and leukemias. Our review highlights the central roles of HERV genes, such as gag, env, pol, np9, and rec in immune regulation, checkpoint blockade, cell differentiation, cell fusion, proliferation, metastasis, and cell transformation. In addition, we summarize the involvement of HERV long terminal repeat (LTR) regions in transcriptional regulation, creation of fusion proteins, expression of long non-coding RNAs (lncRNAs), and promotion of genome instability through recombination.
Collapse
Affiliation(s)
- Erik Stricker
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77047, USA
- Department of Pediatrics, Baylor College of Medicine, Houston, TX 77047, USA
| | | | - Michael E. Scheurer
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77047, USA
- Department of Pediatrics, Baylor College of Medicine, Houston, TX 77047, USA
| |
Collapse
|
2
|
Lee DH, Bae WH, Ha H, Park EG, Lee YJ, Kim WR, Kim HS. Z-DNA-Containing Long Terminal Repeats of Human Endogenous Retrovirus Families Provide Alternative Promoters for Human Functional Genes. Mol Cells 2022; 45:522-530. [PMID: 35950452 PMCID: PMC9385571 DOI: 10.14348/molcells.2022.0060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 05/16/2022] [Accepted: 05/31/2022] [Indexed: 11/27/2022] Open
Abstract
Transposable elements (TEs) account for approximately 45% of the human genome. TEs have proliferated randomly and integrated into functional genes during hominoid radiation. They appear as right-handed B-DNA double helices and slightly elongated left-handed Z-DNAs. Human endogenous retrovirus (HERV) families are widely distributed in human chromosomes at a ratio of 8%. They contain a 5'-long terminal repeat (LTR)-gag-pol-env-3'-LTR structure. LTRs contain the U3 enhancer and promoter region, transcribed R region, and U5 region. LTRs can influence host gene expression by acting as regulatory elements. In this review, we describe the alternative promoters derived from LTR elements that overlap Z-DNA by comparing Z-hunt and DeepZ data for human functional genes. We also present evidence showing the regulatory activity of LTR elements containing Z-DNA in GSDML. Taken together, the regulatory activity of LTR elements with Z-DNA allows us to understand gene function in relation to various human diseases.
Collapse
Affiliation(s)
- Du Hyeong Lee
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Woo Hyeon Bae
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Hongseok Ha
- Division of Life Sciences, Korea University, Seoul 02841, Korea
| | - Eun Gyung Park
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Yun Ju Lee
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Woo Ryung Kim
- Department of Integrated Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| | - Heui-Soo Kim
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Busan 46231, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
| |
Collapse
|
3
|
Carter T, Singh M, Dumbovic G, Chobirko JD, Rinn JL, Feschotte C. Mosaic cis-regulatory evolution drives transcriptional partitioning of HERVH endogenous retrovirus in the human embryo. eLife 2022; 11:76257. [PMID: 35179489 PMCID: PMC8912925 DOI: 10.7554/elife.76257] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 02/17/2022] [Indexed: 12/05/2022] Open
Abstract
The human endogenous retrovirus type-H (HERVH) family is expressed in the preimplantation embryo. A subset of these elements are specifically transcribed in pluripotent stem cells where they appear to exert regulatory activities promoting self-renewal and pluripotency. How HERVH elements achieve such transcriptional specificity remains poorly understood. To uncover the sequence features underlying HERVH transcriptional activity, we performed a phyloregulatory analysis of the long terminal repeats (LTR7) of the HERVH family, which harbor its promoter, using a wealth of regulatory genomics data. We found that the family includes at least eight previously unrecognized subfamilies that have been active at different timepoints in primate evolution and display distinct expression patterns during human embryonic development. Notably, nearly all HERVH elements transcribed in ESCs belong to one of the youngest subfamilies we dubbed LTR7up. LTR7 sequence evolution was driven by a mixture of mutational processes, including point mutations, duplications, and multiple recombination events between subfamilies, that led to transcription factor binding motif modules characteristic of each subfamily. Using a reporter assay, we show that one such motif, a predicted SOX2/3 binding site unique to LTR7up, is essential for robust promoter activity in induced pluripotent stem cells. Together these findings illuminate the mechanisms by which HERVH diversified its expression pattern during evolution to colonize distinct cellular niches within the human embryo.
Collapse
Affiliation(s)
- Thomas Carter
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States [US]
| | - Manvendra Singh
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Gabrijela Dumbovic
- Department of Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Jason D Chobirko
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - John L Rinn
- Department of Biochemistry, University of Colorado Boulder, Boulder, United States
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| |
Collapse
|
4
|
Grandi N, Cadeddu M, Blomberg J, Mayer J, Tramontano E. HERV-W group evolutionary history in non-human primates: characterization of ERV-W orthologs in Catarrhini and related ERV groups in Platyrrhini. BMC Evol Biol 2018; 18:6. [PMID: 29351742 PMCID: PMC5775608 DOI: 10.1186/s12862-018-1125-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 01/14/2018] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The genomes of all vertebrates harbor remnants of ancient retroviral infections, having affected the germ line cells during the last 100 million years. These sequences, named Endogenous Retroviruses (ERVs), have been transmitted to the offspring in a Mendelian way, being relatively stable components of the host genome even long after their exogenous counterparts went extinct. Among human ERVs (HERVs), the HERV-W group is of particular interest for our physiology and pathology. A HERV-W provirus in locus 7q21.2 has been coopted during evolution to exert an essential role in placenta, and the group expression has been tentatively linked to Multiple Sclerosis and other diseases. Following up on a detailed analysis of 213 HERV-W insertions in the human genome, we now investigated the ERV-W group genomic spread within primate lineages. RESULTS We analyzed HERV-W orthologous loci in the genome sequences of 12 non-human primate species belonging to Simiiformes (parvorders Catarrhini and Platyrrhini), Tarsiiformes and to the most primitive Prosimians. Analysis of HERV-W orthologous loci in non-human Catarrhini primates revealed species-specific insertions in the genomes of Chimpanzee (3), Gorilla (4), Orangutan (6), Gibbon (2) and especially Rhesus Macaque (66). Such sequences were acquired in a retroviral fashion and, in the majority of cases, by L1-mediated formation of processed pseudogenes. There were also a number of LTR-LTR homologous recombination events that occurred subsequent to separation of Catarrhini sub-lineages. Moreover, we retrieved 130 sequences in Marmoset and Squirrel Monkeys (family Cebidae, Platyrrhini parvorder), identified as ERV1-1_CJa based on RepBase annotations, which appear closely related to the ERV-W group. Such sequences were also identified in Atelidae and Pitheciidae, representative of the other Platyrrhini families. In contrast, no ERV-W-related sequences were found in genome sequence assemblies of Tarsiiformes and Prosimians. CONCLUSIONS Overall, our analysis now provides a detailed picture of the ERV-W sequences colonization of the primate lineages genomes, revealing the exact dynamics of ERV-W locus formations as well as novel insights into the evolution and origin of the group.
Collapse
Affiliation(s)
- Nicole Grandi
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Marta Cadeddu
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Jonas Blomberg
- Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Jens Mayer
- Institute of Human Genetics, University of Saarland, Homburg, Germany
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
- Istituto di Ricerca Genetica e Biomedica (IRGB), CNR, Monserrato, Italy
| |
Collapse
|
5
|
Grandi N, Cadeddu M, Pisano MP, Esposito F, Blomberg J, Tramontano E. Identification of a novel HERV-K(HML10): comprehensive characterization and comparative analysis in non-human primates provide insights about HML10 proviruses structure and diffusion. Mob DNA 2017; 8:15. [PMID: 29118853 PMCID: PMC5667498 DOI: 10.1186/s13100-017-0099-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/24/2017] [Indexed: 11/23/2022] Open
Abstract
Background About half of the human genome is constituted of transposable elements, including human endogenous retroviruses (HERV). HERV sequences represent the 8% of our genetic material, deriving from exogenous infections occurred millions of years ago in the germ line cells and being inherited by the offspring in a Mendelian fashion. HERV-K elements (classified as HML1–10) are among the most studied HERV groups, especially due to their possible correlation with human diseases. In particular, the HML10 group was reported to be upregulated in persistent HIV-1 infected cells as well as in tumor cells and samples, and proposed to have a role in the control of host genes expression. An individual HERV-K(HML10) member within the major histocompatibility complex C4 gene has even been studied for its possible contribution to type 1 diabetes susceptibility. Following a first characterization of the HML10 group at the genomic level, performed with the innovative software RetroTector, we have characterized in detail the 8 previously identified HML10 sequences present in the human genome, and an additional HML10 partial provirus in chromosome 1p22.2 that is reported here for the first time. Results Using a combined approach based on RetroTector software and a traditional Genome Browser Blat search, we identified a novel HERV-K(HML10) sequence in addition to the eight previously reported in the human genome GRCh37/hg19 assembly. We fully characterized the nine HML10 sequences at the genomic level, including their classification in two types based on both structural and phylogenetic characteristics, a detailed analysis of each HML10 nucleotide sequence, the first description of the presence of an Env Rec domain in the type II HML10, the estimated time of integration of individual members and the comparative map of the HML10 proviruses in non-human primates. Conclusions We performed an unambiguous and exhaustive analysis of the nine HML10 sequences present in GRCh37/hg19 assembly, useful to increase the knowledge of the group’s contribution to the human genome and laying the foundation for a better understanding of the potential physiological effects and the tentative correlation of these sequences with human pathogenesis. Electronic supplementary material The online version of this article (10.1186/s13100-017-0099-7) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Nicole Grandi
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Marta Cadeddu
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Maria Paola Pisano
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Francesca Esposito
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Jonas Blomberg
- Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy.,Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche (CNR), Monserrato, Cagliari, Italy
| |
Collapse
|
6
|
Grandi N, Tramontano E. Type W Human Endogenous Retrovirus (HERV-W) Integrations and Their Mobilization by L1 Machinery: Contribution to the Human Transcriptome and Impact on the Host Physiopathology. Viruses 2017; 9:v9070162. [PMID: 28653997 PMCID: PMC5537654 DOI: 10.3390/v9070162] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/08/2017] [Accepted: 06/20/2017] [Indexed: 01/07/2023] Open
Abstract
Human Endogenous Retroviruses (HERVs) are ancient infection relics constituting ~8% of our DNA. While HERVs’ genomic characterization is still ongoing, impressive amounts of data have been obtained regarding their general expression across tissues. Among HERVs, one of the most studied is the W group, which is the sole HERV group specifically mobilized by the long interspersed element-1 (LINE-1) machinery, providing a source of novel insertions by retrotransposition of HERV-W processed pseudogenes, and comprising a member encoding a functional envelope protein coopted for human placentation. The HERV-W group has been intensively investigated for its putative role in several diseases, such as cancer, inflammation, and autoimmunity. Despite major interest in the link between HERV-W expression and human pathogenesis, no conclusive correlation has been demonstrated so far. In general, (i) the absence of a proper identification of the specific HERV-W sequences expressed in a given condition; and (ii) the lack of studies attempting to connect the various observations in the same experimental conditions are the major problems preventing the definitive assessment of the HERV-W impact on human physiopathology. In this review, we summarize the current knowledge on the HERV-W group presence within the human genome and its expression in physiological tissues as well as in the main pathological contexts.
Collapse
Affiliation(s)
- Nicole Grandi
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554, 09042 Monserrato, Cagliari, Italy.
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554, 09042 Monserrato, Cagliari, Italy.
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche (CNR), 09042 Monserrato, Cagliari, Italy.
| |
Collapse
|
7
|
Broecker F, Horton R, Heinrich J, Franz A, Schweiger MR, Lehrach H, Moelling K. The intron-enriched HERV-K(HML-10) family suppresses apoptosis, an indicator of malignant transformation. Mob DNA 2016; 7:25. [PMID: 27980690 PMCID: PMC5142424 DOI: 10.1186/s13100-016-0081-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 11/19/2016] [Indexed: 02/06/2023] Open
Abstract
Background Human endogenous retroviruses (HERVs) constitute 8% of the human genome and contribute substantially to the transcriptome. HERVs have been shown to generate RNAs that modulate host gene expression. However, experimental evidence for an impact of these regulatory transcripts on the cellular phenotype has been lacking. Results We characterized the previously little described HERV-K(HML-10) endogenous retrovirus family on a genome-wide scale. HML-10 invaded the ancestral genome of Old World monkeys about 35 Million years ago and is enriched within introns of human genes when compared to other HERV families. We show that long terminal repeats (LTRs) of HML-10 exhibit variable promoter activity in human cancer cell lines. One identified HML-10 LTR-primed RNA was in opposite orientation to the pro-apoptotic Death-associated protein 3 (DAP3). In HeLa cells, experimental inactivation of HML-10 LTR-primed transcripts induced DAP3 expression levels, which led to apoptosis. Conclusions Its enrichment within introns suggests that HML-10 may have been evolutionary co-opted for gene regulation more than other HERV families. We demonstrated such a regulatory activity for an HML-10 RNA that suppressed DAP3-mediated apoptosis in HeLa cells. Since HML-10 RNA appears to be upregulated in various tumor cell lines and primary tumor samples, it may contribute to evasion of apoptosis in malignant cells. However, the overall weak expression of HML-10 transcripts described here raises the question whether our result described for HeLa represent a rare event in cancer. A possible function in other cells or tissues requires further investigation. Electronic supplementary material The online version of this article (doi:10.1186/s13100-016-0081-9) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Felix Broecker
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany ; Institute of Medical Microbiology, University of Zurich, Gloriastr. 32, 8006 Zurich, Switzerland ; Current affiliation: Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14424 Potsdam, Germany
| | - Roger Horton
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany
| | - Jochen Heinrich
- Institute of Medical Microbiology, University of Zurich, Gloriastr. 32, 8006 Zurich, Switzerland
| | - Alexandra Franz
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany ; Current affiliation: University of Zurich, Institute of Molecular Life Sciences, Winterthurerstr. 190, 8057 Zurich, Switzerland
| | - Michal-Ruth Schweiger
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany ; Current affiliation: Functional Epigenomics, CCG, Cologne University Hospital, University of Cologne, Weyertal 115b, 50931 Cologne, Germany
| | - Hans Lehrach
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany ; Dahlem Centre for Genome Research and Medical Systems Biology, Fabeckstr. 60-62, 14195 Berlin, Germany
| | - Karin Moelling
- Max Planck Institute for molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany ; Institute of Medical Microbiology, University of Zurich, Gloriastr. 32, 8006 Zurich, Switzerland
| |
Collapse
|
8
|
Hu L, Uzhameckis D, Hedborg F, Blomberg J. Dynamic and selective HERV RNA expression in neuroblastoma cells subjected to variation in oxygen tension and demethylation. APMIS 2016; 124:140-9. [PMID: 26818268 DOI: 10.1111/apm.12494] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 11/09/2015] [Indexed: 12/15/2022]
Abstract
We studied HERV expression in cell lines after hypoxia, mitogenic stimulation, and demethylation, to better understand if hypoxia may play a role in ERV activation also within the nervous system, as represented by neuroblastoma cell lines. The level of RNA of four human ERV groups (HERVs) (HERVE, I/T, H, and W), and three housekeeping genes, of different cell lines including A549, COS-1, Namalwa, RD-L and Vero-E6, as well as human neuroblastoma cell lines SH-SY5Y, SK-N-DZ, and SK-N-AS were studied using reverse transcription and real-time quantitative PCR (QPCR). During the course of recovery from hypoxia a pronounced and selective activation of RNA expression of HERVW-like sequences, but not of HERVE, I/T, H, and three housekeeping genes, was found in the neuroblastoma cell lines, most pronounced in SK-N-DZ. In the SK-N-DZ cell line, we also tested the expression of HERVs after chemical treatments. HERVW-like sequences were selectively upregulated by 5-azacytidine, a demethylating agent. Some HERVW loci seem especially responsive to hypoxia and demethylation. HERV expression in neuroblastoma cells is selectively and profoundly influenced by some physiological and chemical stimuli.
Collapse
Affiliation(s)
- Lijuan Hu
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Dmitrijs Uzhameckis
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Fredrik Hedborg
- Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Jonas Blomberg
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| |
Collapse
|
9
|
Li F, Karlsson H. Expression and regulation of human endogenous retrovirus W elements. APMIS 2016; 124:52-66. [PMID: 26818262 DOI: 10.1111/apm.12478] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 10/12/2015] [Indexed: 01/06/2023]
Abstract
Human endogenous retroviruses (HERV) comprise 8% of the human genome and can be classified into at least 31 families. A typical HERV provirus consists of internal gag, pol and env genes, flanked by two long terminal repeats (LTRs). No single provirus is capable of engendering infectious particles. HERV are by nature repetitive and have with few notable exceptions lost their protein-coding capacity. Therefore, HERV have consistently been excluded from array-based expression studies and hence little is known of their expression, regulation, and potential functional significance. An increasing number of studies have, however, observed expression of the W family of HERV in various human tissues and cells, predominantly in placenta. HERV-W LTRs act as promoters in directing transcription of HERV-W members, contribute to their tissue-specific and highly diversified expression pattern. Furthermore, leaky transcription originating from adjacent genes plays a role in the transcription initiation of HERV-W psudoelements. It has been reported that HERV-W elements, including ERVWE1 (the so far only known HERV-W locus harboring a gene (env) functionally adopted by the human host to critically participate in placenta biogenesis), can become transactivated in a range of human non-placental cell-lines during exogenous virus infections. Aberrant expression of HERV-W has been associated with human diseases, such as cancer, multiple sclerosis, and schizophrenia. Based on published reports, transcriptional activities of HERV-W appear to be influenced by several mechanisms; binding of transcription factors to LTR promoters and enhancers outside of LTRs, genetic variation and alteration in DNA methylation and histone modification. Emerging mechanistic studies support the notion that HERV-W represents a potential marker or mediator of environmental exposures (e.g., virus infection) in the development of chronic complex diseases.
Collapse
Affiliation(s)
- Fang Li
- Department of Basic Medical Science, Changsha Medical University, Changsha, China.,Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Håkan Karlsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
10
|
Transcriptional derepression of the ERVWE1 locus following influenza A virus infection. J Virol 2014; 88:4328-37. [PMID: 24478419 DOI: 10.1128/jvi.03628-13] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Syncytin-1, a fusogenic protein encoded by a human endogenous retrovirus of the W family (HERV-W) element (ERVWE1), is expressed in the syncytiotrophoblast layer of the placenta. This locus is transcriptionally repressed in adult tissues through promoter CpG methylation and suppressive histone modifications. Whereas syncytin-1 appears to be crucial for the development and functioning of the human placenta, its ectopic expression has been associated with pathological conditions, such as multiple sclerosis and schizophrenia. We previously reported on the transactivation of HERV-W elements, including ERVWE1, during influenza A/WSN/33 virus infection in a range of human cell lines. Here we report the results of quantitative PCR analyses of transcripts encoding syncytin-1 in both cell lines and primary fibroblast cells. We observed that spliced ERVWE1 transcripts and those encoding the transcription factor glial cells missing 1 (GCM1), acting as an enhancer element upstream of ERVWE1, are prominently upregulated in response to influenza A/WSN/33 virus infection in nonplacental cells. Knockdown of GCM1 by small interfering RNA followed by infection suppressed the transactivation of ERVWE1. While the infection had no influence on CpG methylation in the ERVWE1 promoter, chromatin immunoprecipitation assays detected decreased H3K9 trimethylation (H3K9me3) and histone methyltransferase SETDB1 levels along with influenza virus proteins associated with ERVWE1 and other HERV-W loci in infected CCF-STTG1 cells. The present findings suggest that an exogenous influenza virus infection can transactivate ERVWE1 by increasing transcription of GCM1 and reducing H3K9me3 in this region and in other regions harboring HERV-W elements. IMPORTANCE Syncytin-1, a protein encoded by the env gene in the HERV-W locus ERVWE1, appears to be crucial for the development and functioning of the human placenta and is transcriptionally repressed in nonplacental tissues. Nevertheless, its ectopic expression has been associated with pathological conditions, such as multiple sclerosis and schizophrenia. In the present paper, we report findings suggesting that an exogenous influenza A virus infection can transactivate ERVWE1 by increasing the transcription of GCM1 and reducing the repressive histone mark H3K9me3 in this region and in other regions harboring HERV-W elements. These observations have implications of potential relevance for viral pathogenesis and for conditions associated with the aberrant transcription of HERV-W loci.
Collapse
|
11
|
Activation of elements in HERV-W family by caffeine and aspirin. Virus Genes 2013; 47:219-27. [PMID: 23813246 DOI: 10.1007/s11262-013-0939-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 06/11/2013] [Indexed: 10/26/2022]
Abstract
Caffeine and aspirin have been suggested to be involved in neurologic diseases, such as schizophrenia, and previous data have revealed that abnormal expression of HERV-W elements may be an important factor in the etiopathogenesis of those diseases. In this article, we reported that caffeine and aspirin contributed to the expression of HERV-W env and gag in Human SH-SY5Y neuroblastoma cells. Semi-quantitative RT-PCR and quantitative Real-time PCR were used to detect the mRNA of HERV-W env and gag in cells exposed to caffeine or aspirin. Western blotting was used to detect the protein of HERV-W env. Luciferase activity assay was employed to detect the activity of HERV-W env promoter. It was found that both caffeine and aspirin could increase the expression of HERV-W env and gag in human SH-SY5Y neuroblastoma cells. Caffeine could activate the HERV-W env promoter, while aspirin could not. With previous studies we can conjecture that HERVs might play a bridging role between environmental factors, such as drugs and neurologic diseases.
Collapse
|
12
|
do Olival GS, Faria TS, Nali LHS, de Oliveira ACP, Casseb J, Vidal JE, Cavenaghi VB, Tilbery CP, Moraes L, Fink MCS, Sumita LM, Perron H, Romano CM. Genomic analysis of ERVWE2 locus in patients with multiple sclerosis: absence of genetic association but potential role of human endogenous retrovirus type W elements in molecular mimicry with myelin antigen. Front Microbiol 2013; 4:172. [PMID: 23805135 PMCID: PMC3693062 DOI: 10.3389/fmicb.2013.00172] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 06/05/2013] [Indexed: 12/11/2022] Open
Abstract
Human endogenous retroviruses (HERVs) arise from ancient infections of the host germline cells by exogenous retroviruses, constituting 8% of the human genome. Elevated level of envelope transcripts from HERVs-W has been detected in CSF, plasma and brain tissues from patients with Multiple Sclerosis (MS), most of them from Xq22.3, 15q21.3, and 6q21 chromosomes. However, since the locus Xq22.3 (ERVWE2) lack the 5' LTR promoter and the putative protein should be truncated due to a stop codon, we investigated the ERVWE2 genomic loci from 84 individuals, including MS patients with active HERV-W expression detected in PBMC. In addition, an automated search for promoter sequences in 20 kb nearby region of ERVWE2 reference sequence was performed. Several putative binding sites for cellular cofactors and enhancers were found, suggesting that transcription may occur via alternative promoters. However, ERVWE2 DNA sequencing of MS and healthy individuals revealed that all of them harbor a stop codon at site 39, undermining the expression of a full-length protein. Finally, since plaque formation in central nervous system (CNS) of MS patients is attributed to immunological mechanisms triggered by autoimmune attack against myelin, we also investigated the level of similarity between envelope protein and myelin oligodendrocyte glycoprotein (MOG). Comparison of the MOG to the envelope identified five retroviral regions similar to the Ig-like domain of MOG. Interestingly, one of them includes T and B cell epitopes, capable to induce T effector functions and circulating Abs in rats. In sum, although no DNA substitutions that would link ERVWE2 to the MS pathogeny was found, the similarity between the envelope protein to MOG extends the idea that ERVEW2 may be involved on the immunopathogenesis of MS, maybe facilitating the MOG recognizing by the immune system. Although awaiting experimental evidences, the data presented here may expand the scope of the endogenous retroviruses involvement on MS pathogenesis.
Collapse
Affiliation(s)
- Guilherme S. do Olival
- Departamento de Neurologia, Irmandade da Santa Casa de Misericórdia de São PauloSão Paulo, Brazil
| | - Thiago S. Faria
- Departamento de Moléstias Infecciosas e Parasitárias – (LIMHC), Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | - Luiz H. S. Nali
- Departamento de Moléstias Infecciosas e Parasitárias – (LIMHC), Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | | | - Jorge Casseb
- Departamento de Neurologia, Instituto de Infectologia Emilio RibasSão Paulo, Brazil
- Laboratório de Imunodeficiências e Dermatologia, Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | - Jose E. Vidal
- Departamento de Neurologia, Instituto de Infectologia Emilio RibasSão Paulo, Brazil
| | - Vitor B. Cavenaghi
- Departamento de Neurologia, Irmandade da Santa Casa de Misericórdia de São PauloSão Paulo, Brazil
| | - Charles P. Tilbery
- Departamento de Neurologia, Irmandade da Santa Casa de Misericórdia de São PauloSão Paulo, Brazil
| | - Lenira Moraes
- Departamento de Neurologia, Hospital das Clínicas da Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | - Maria C. S. Fink
- Departamento de Moléstias Infecciosas e Parasitárias – (LIMHC), Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | - Laura M. Sumita
- Departamento de Moléstias Infecciosas e Parasitárias – (LIMHC), Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| | | | - Camila M. Romano
- Departamento de Moléstias Infecciosas e Parasitárias – (LIMHC), Instituto de Medicina Tropical de São Paulo e Faculdade de Medicina, Universidade de São PauloSão Paulo, Brazil
| |
Collapse
|
13
|
Jung YD, Ahn K, Kim YJ, Bae JH, Lee JR, Kim HS. Retroelements: molecular features and implications for disease. Genes Genet Syst 2013; 88:31-43. [PMID: 23676708 DOI: 10.1266/ggs.88.31] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Eukaryotic genomes comprise numerous retroelements that have a major impact on the structure and regulation of gene function. Retroelements are regulated by epigenetic controls, and they generate multiple miRNAs that are involved in the induction and progression of genomic instability. Elucidation of the biological roles of retroelements deserves continuous investigation to better understand their evolutionary features and implications for disease.
Collapse
Affiliation(s)
- Yi-Deun Jung
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Busan 609-735, Republic of Korea
| | | | | | | | | | | |
Collapse
|
14
|
Pačes J, Huang YT, Pačes V, Rídl J, Chang CM. New insight into transcription of human endogenous retroviral elements. N Biotechnol 2012. [PMID: 23201072 DOI: 10.1016/j.nbt.2012.11.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It is generally assumed that human endogenous retroviral elements (HERVs) belong to the class of genomic repetitive nucleotide sequences often called 'junk DNA'. These elements were categorized to families, and members of some of these families (e.g. HERV-H, HERV-W and HERV-K) were shown to be transcribed. These transcriptions were associated with several severe diseases such as mental disorders, AIDS, autoimmune diseases and cancer. In this review we discuss several bioinformatics strategies for genome-wide scan of HERVs transcription using high-throughput RNA sequencing on several platforms. We show that many more HERVs than previously described are transcribed to various levels and we discuss possible implications of these transcriptions.
Collapse
Affiliation(s)
- Jan Pačes
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Vídeňská 1083, CZ-14220 Prague, Czech Republic.
| | | | | | | | | |
Collapse
|
15
|
Kim HS. Genomic impact, chromosomal distribution and transcriptional regulation of HERV elements. Mol Cells 2012; 33:539-44. [PMID: 22562360 PMCID: PMC3887755 DOI: 10.1007/s10059-012-0037-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 10/28/2022] Open
Abstract
Human endogenous retroviruses (HERVs) mediate structural variation and genomic instability based on their multiple copy number, inherent ability to mobilize via reverse transcriptase, and high sequence similarity. Moreover, they undergo multiple amplification and retrotransposition events, resulting in the widespread distribution of complete or partial retroviral sequences throughout the primate genome. As such, HERV elements have played important biological roles in genome evolution, and their long terminal repeat (LTR) elements contain numerous regulatory sequences, including effective promoters, enhancers, polyadenylation signals, and transcription factorbinding sites. Lastly, HERV elements are capable of influencing the expression of neighboring genes, a process that also contributed to primate evolution.
Collapse
Affiliation(s)
- Heui-Soo Kim
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Busan 609-735, Korea.
| |
Collapse
|
16
|
Expression patterns of non-coding spliced transcripts from human endogenous retrovirus HERV-H elements in colon cancer. PLoS One 2012; 7:e29950. [PMID: 22238681 PMCID: PMC3253121 DOI: 10.1371/journal.pone.0029950] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/07/2011] [Indexed: 11/25/2022] Open
Abstract
Background Up-regulation of the most abundant H family human endogenous retrovirus (HERV-H), especially env-related transcripts, correlates with colon cancer. However, expression pattern of spliced non-coding transcripts of HERV-H is not clear. Methodology/Principal Findings In this study, expression of HERV-H spliced transcripts in colon cancer was investigated by a RT-PCR strategy using primers targeting the tRNAHis primer-binding site and the R region in the 3′ long terminal repeat (LTR), followed by cloning and sequencing of the amplicons. Sequences were then assigned to individual HERV-H loci by employing private nucleotide differences between loci. Different expression patterns of HERV-H spliced transcripts from distinct active elements were found in colon cancer cell lines HT29, LS 174T, RKO, SW480 and SW620. Furthermore, the expression patterns in SW480 and RKO were significantly changed by demethylation treatment. Interestingly, more HERV-H elements were found to be transcriptionally active in colon tumor tissues than in adjacent normal tissues (14 vs. 7). Conclusions/Significance This is the first research to study the character of expression of non-coding spliced transcripts of HERV-H elements in colon cancer. Expression patterns of HERV-H spliced transcripts differed among colon cancer cell lines and could be affected by genomic DNA methylation levels. More importantly, besides the commonly accepted view of up-regulation of HERV-H expression in colon tumor tissues, we found more active HERV-H loci in colon tumor as compared with adjacent normal tissues.
Collapse
|
17
|
Kim YJ, Huh JW, Kim DS, Han K, Kim HM, Kim HS. Evolutionary diversification of DYX1C1 transcripts via an HERV-H LTR integration event. Genes Genet Syst 2012; 86:277-84. [PMID: 22214596 DOI: 10.1266/ggs.86.277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
DYX1C1 is a candidate gene for developmental dyslexia and has three alternative pre-mRNA spliced forms in the human genome. One of the transcripts contains an HERV-H LTR that could affect the expression level of DYX1C1. We speculate that the HERV-H LTR integrated into the DYX1C1 locus in the catarrhine lineage after its divergence from the platyrrhine lineage. Reverse transcription-PCR of the HERV-H LTR-related transcript produced four alternative forms from several human tissues. All of alternative forms were also identified in various rhesus macaque tissues. Through sequencing analysis of various primate DNA samples, we found that a part of the HERV-H LTR sequence was duplicated within the DYX1C1 exon 9 only in catarrhines. However, the duplication event did not cause frameshift mutation of the DYX1C1 transcript. Taken together, this HERV-H LTR insertion into DYX1C1 has contributed to transcript diversification of DYX1C1 during primate evolution.
Collapse
Affiliation(s)
- Yun-Ji Kim
- Department of Biological Sciences, College of Natural Sciences, Pusan National University, Republic of Korea
| | | | | | | | | | | |
Collapse
|
18
|
Activation of LTRs from different human endogenous retrovirus (HERV) families by the HTLV-1 tax protein and T-cell activators. Viruses 2011; 3:2146-59. [PMID: 22163338 PMCID: PMC3230845 DOI: 10.3390/v3112146] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 10/22/2011] [Indexed: 11/16/2022] Open
Abstract
Human endogenous retroviruses (HERVs) represent approximately 8% of our genome. HERVs influence cellular gene expression and contribute to normal physiological processes such as cellular differentiation and morphogenesis. HERVs have also been associated with certain pathological conditions, including cancer and neurodegenerative diseases. As HTLV-1 causes adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and has been shown to modulate host gene expression mainly through the expression of the powerful Tax transactivator, herein we were interested in looking at the potential modulation capacity of HTLV-1 Tax on HERV expression. In order to evaluate the promoter activity of different HERV LTRs, pHERV-LTR-luc constructs were co-transfected in Jurkat T-cells with a Tax expression vector. Tax expression potently increased the LTR activity of HERV-W8 and HERV-H (MC16). In parallel, Jurkat cells were also stimulated with different T-cell-activating agents and HERV LTRs were observed to respond to different combination of Forskolin, bpV[pic] a protein tyrosine phosphatase inhibitor, and PMA. Transfection of expression vectors for different Tax mutants in Jurkat cells showed that several transcription factors including CREB appeared to be important for HERV-W8 LTR activation. Deletion mutants were derived from the HERV-W8 LTR and the region from −137 to −123 was found to be important for LTR response following Tax expression in Jurkat cells, while a different region was shown to be required in cells treated with activators. Our results thus demonstrated that HTLV-1 Tax activates several HERV LTRs. This raises the possibility that upregulated HERV expression could be involved in diseases associated with HTLV-1 infection.
Collapse
|
19
|
Li F, Nellåker C, Yolken RH, Karlsson H. A systematic evaluation of expression of HERV-W elements; influence of genomic context, viral structure and orientation. BMC Genomics 2011; 12:22. [PMID: 21226900 PMCID: PMC3031232 DOI: 10.1186/1471-2164-12-22] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 01/12/2011] [Indexed: 12/19/2022] Open
Abstract
Background One member of the W family of human endogenous retroviruses (HERV) appears to have been functionally adopted by the human host. Nevertheless, a highly diversified and regulated transcription from a range of HERV-W elements has been observed in human tissues and cells. Aberrant expression of members of this family has also been associated with human disease such as multiple sclerosis (MS) and schizophrenia. It is not known whether this broad expression of HERV-W elements represents transcriptional leakage or specific transcription initiated from the retroviral promoter in the long terminal repeat (LTR) region. Therefore, potential influences of genomic context, structure and orientation on the expression levels of individual HERV-W elements in normal human tissues were systematically investigated. Results Whereas intronic HERV-W elements with a pseudogene structure exhibited a strong anti-sense orientation bias, intronic elements with a proviral structure and solo LTRs did not. Although a highly variable expression across tissues and elements was observed, systematic effects of context, structure and orientation were also observed. Elements located in intronic regions appeared to be expressed at higher levels than elements located in intergenic regions. Intronic elements with proviral structures were expressed at higher levels than those elements bearing hallmarks of processed pseudogenes or solo LTRs. Relative to their corresponding genes, intronic elements integrated on the sense strand appeared to be transcribed at higher levels than those integrated on the anti-sense strand. Moreover, the expression of proviral elements appeared to be independent from that of their corresponding genes. Conclusions Intronic HERV-W provirus integrations on the sense strand appear to have elicited a weaker negative selection than pseudogene integrations of transcripts from such elements. Our current findings suggest that the previously observed diversified and tissue-specific expression of elements in the HERV-W family is the result of both directed transcription (involving both the LTR and internal sequence) and leaky transcription of HERV-W elements in normal human tissues.
Collapse
Affiliation(s)
- Fang Li
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | | | | | | |
Collapse
|
20
|
Abrarova ND, Stoukacheva EA, Pleshkan VV, Vinogradova TV, Sverdlov ED. Functional analysis of the HERV-K LTR residing in the KIAA1245/NBPF subfamily genes. Mol Biol 2010. [DOI: 10.1134/s0026893310040084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
21
|
Antony JM, Deslauriers AM, Bhat RK, Ellestad KK, Power C. Human endogenous retroviruses and multiple sclerosis: innocent bystanders or disease determinants? Biochim Biophys Acta Mol Basis Dis 2010; 1812:162-76. [PMID: 20696240 PMCID: PMC7172332 DOI: 10.1016/j.bbadis.2010.07.016] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 07/14/2010] [Accepted: 07/26/2010] [Indexed: 12/21/2022]
Abstract
Human endogenous retroviruses (HERVs) constitute 5–8% of human genomic DNA and are replication incompetent despite expression of individual HERV genes from different chromosomal loci depending on the specific tissue. Several HERV genes have been detected as transcripts and proteins in the central nervous system, frequently in the context of neuroinflammation. The HERV-W family has received substantial attention in large part because of associations with diverse syndromes including multiple sclerosis (MS) and several psychiatric disorders. A HERV-W-related retroelement, multiple sclerosis retrovirus (MSRV), has been reported in MS patients to be both a biomarker as well as an effector of aberrant immune responses. HERV-H and HERV-K have also been implicated in MS and other neurological diseases but await delineation of their contributions to disease. The HERV-W envelope-encoded glycosylated protein, syncytin-1, is encoded by chromosome 7q21 and exhibits increased glial expression within MS lesions. Overexpression of syncytin-1 in glia induces endoplasmic reticulum stress leading to neuroinflammation and the induction of free radicals, which damage proximate cells. Syncytin-1's receptor, ASCT1 is a neutral amino acid transporter expressed on glia and is suppressed in white matter of MS patients. Of interest, antioxidants ameliorate syncytin-1's neuropathogenic effects raising the possibility of using these agents as therapeutics for neuroinflammatory diseases. Given the multiple insertion sites of HERV genes as complete and incomplete open reading frames, together with their differing capacity to be expressed and the complexities of individual HERVs as both disease markers and bioactive effectors, HERV biology is a compelling area for understanding neuropathogenic mechanisms and developing new therapeutic strategies.
Collapse
|
22
|
Khodosevich K, Lebedev Y, Sverdlov E. Endogenous retroviruses and human evolution. Comp Funct Genomics 2010; 3:494-8. [PMID: 18629260 PMCID: PMC2448423 DOI: 10.1002/cfg.216] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2002] [Accepted: 10/09/2002] [Indexed: 11/12/2022] Open
Abstract
Humans share about 99% of their genomic DNA with chimpanzees and bonobos; thus, the differences between these species are unlikely to be in gene content but could be
caused by inherited changes in regulatory systems. Endogenous retroviruses (ERVs)
comprise ∼ 5% of the human genome. The LTRs of ERVs contain many regulatory
sequences, such as promoters, enhancers, polyadenylation signals and factor-binding
sites. Thus, they can influence the expression of nearby human genes. All known
human-specific LTRs belong to the HERV-K (human ERV) family, the most active
family in the human genome. It is likely that some of these ERVs could have integrated
into regulatory regions of the human genome, and therefore could have had an impact
on the expression of adjacent genes, which have consequently contributed to human
evolution. This review discusses possible functional consequences of ERV integration
in active coding regions.
Collapse
Affiliation(s)
- Konstantin Khodosevich
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, 16/10 Miklukho-Maklaya, Moscow 117997, Russia.
| | | | | |
Collapse
|
23
|
Gimenez J, Montgiraud C, Pichon JP, Bonnaud B, Arsac M, Ruel K, Bouton O, Mallet F. Custom human endogenous retroviruses dedicated microarray identifies self-induced HERV-W family elements reactivated in testicular cancer upon methylation control. Nucleic Acids Res 2010; 38:2229-46. [PMID: 20053729 PMCID: PMC2853125 DOI: 10.1093/nar/gkp1214] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Endogenous retroviruses (ERVs) are an inherited part of the eukaryotic genomes, and represent ∼400 000 loci in the human genome. Human endogenous retroviruses (HERVs) can be divided into distinct families, composed of phylogenetically related but structurally heterogeneous elements. The majority of HERVs are silent in most physiological contexts, whereas a significant expression is observed in pathological contexts, such as cancers. Owing to their repetitive nature, few of the active HERV elements have been accurately identified. In addition, there are no criteria defining the active promoters among HERV long-terminal repeats (LTRs). Hence, it is difficult to understand the HERV (de)regulation mechanisms and their implication on the physiopathology of the host. We developed a microarray to specifically detect the LTR-containing transcripts from the HERV-H, HERV-E, HERV-W and HERV-K(HML-2) families. HERV transcriptome was analyzed in the placenta and seven normal/tumoral match-pair samples. We identified six HERV-W loci overexpressed in testicular cancer, including a usually placenta-restricted transcript of ERVWE1. For each locus, specific overexpression was confirmed by quantitative RT-PCR, and comparison of the activity of U3 versus U5 regions suggested a U3-promoted transcription coupled with 5′R initiation. The analysis of DNA from tumoral versus normal tissue revealed that hypomethylation of U3 promoters in tumors is a prerequisite for their activation.
Collapse
Affiliation(s)
- Juliette Gimenez
- Laboratoire Commun de Recherche Hospices Civils de Lyon-bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, bâtiment 3F, 69495 Pierre Bénite Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|
24
|
The LTR of endogenous retrovirus ev21 retains promoter activity and exhibits tissue specific transcription in chicken. Sci Bull (Beijing) 2010. [DOI: 10.1007/s11434-009-0547-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
25
|
Nellåker C, Li F, Uhrzander F, Tyrcha J, Karlsson H. Expression profiling of repetitive elements by melting temperature analysis: variation in HERV-W gag expression across human individuals and tissues. BMC Genomics 2009; 10:532. [PMID: 19919688 PMCID: PMC2779825 DOI: 10.1186/1471-2164-10-532] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 11/17/2009] [Indexed: 01/12/2023] Open
Abstract
Background Human endogenous retroviruses (HERV) constitute approximately 8% of the human genome and have long been considered "junk". The sheer number and repetitive nature of these elements make studies of their expression methodologically challenging. Hence, little is known of transcription of genomic regions harboring such elements. Results Applying a recently developed technique for obtaining high resolution melting temperature data, we examined the frequency distributions of HERV-W gag element into 13 Tm categories in human tissues. Transcripts containing HERV-W gag sequences were expressed in non-random patterns with extensive variations in the expression between both tissues, including different brain regions, and individuals. Furthermore, the patterns of such transcripts varied more between individuals in brain regions than other tissues. Conclusion Thus, regulated expression of non-coding regions of the human genome appears to include the HERV-W family of repetitive elements. Although it remains to be established whether such expression patterns represent leakage from transcription of functional regions or specific transcription, the current approach proves itself useful for studying detailed expression patterns of repetitive regions.
Collapse
Affiliation(s)
- Christoffer Nellåker
- Department of Neuroscience, Karolinska Institutet, Retzius Väg 8 B2:5, 17177 Stockholm, Sweden.
| | | | | | | | | |
Collapse
|
26
|
Human endogenous retroviral long terminal repeat sequences as cell type-specific promoters in retroviral vectors. J Virol 2009; 83:12643-50. [PMID: 19741000 DOI: 10.1128/jvi.00858-09] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human genome contains more than half a million human endogenous retrovirus (HERV) long terminal repeats (LTRs) that can be regarded as mobile regulatory modules. Many of these HERV LTRs have been recruited during evolution as transcriptional control elements for cellular gene expression. We have cloned LTR sequences from two HERV families, HERV-H and HERV-L, differing widely in their activity and tissue specificity into a murine leukemia virus (MLV)-based promoter conversion vector (ProCon). Various human cell lines were infected with the HERV-MLV hybrid vectors, and cell type-specific expression of the reporter gene was compared with the promoter specificity of the corresponding HERV LTRs in transient-transfection assays. Transcription start site analysis of HERV-MLV hybrid vectors revealed preferential use of the HERV promoter initiation site. Our data show that HERV LTRs function in the context of retroviral vectors in certain cell types and have the potential to be useful as cell type-specific promoters in vector construction.
Collapse
|
27
|
Liang Q, Ding J, Xu R, Xu Z, Zheng S. Identification of a novel human endogenous retrovirus and promoter activity of its 5' U3. Biochem Biophys Res Commun 2009; 382:468-72. [PMID: 19289097 DOI: 10.1016/j.bbrc.2009.03.058] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 03/10/2009] [Indexed: 01/04/2023]
Abstract
Up-regulation of human endogenous retroviruses (HERVs) sometimes occurs in cancer. This study identifies a novel HERV (HERV-HX) in colon tumor tissues, which is an H family HERV (HERV-H) element located on chromosome Xp22.32. The full-length transcript sequence was identified and characterized. Quantitative RT-PCR indicated it is up-regulated in colon tumor samples. Using RT-PCR to analyze the transcription of the env-deleted HERV-HX and other env-intact HERV-H elements, it was demonstrated that transcription of HERV-H in colon cancer is not associated with the env gene. A 17-bp sequence was found within the 5' U3 region of HERV-HX, and only 8-bp sequences existed on its homologous U3 regions in the corresponding loci. Promoter activity assays indicated that replacing the 17-bp sequence with an 8-bp sequence or deleting it reduced its activity, suggesting that the 17-bp sequence is important to the expression of HERV-HX.
Collapse
Affiliation(s)
- Qiaoyi Liang
- Cancer Institute, Second Affiliated Hospital, and Ministry of Education Key Laboratory of Cancer Prevention and Intervention, Zhejiang University School of Medicine, Hangzhou, China
| | | | | | | | | |
Collapse
|
28
|
Cooperative exonization of MaLR and AluJo elements contributed an alternative promoter and novel splice variants of RNF19. Gene 2008; 424:63-70. [PMID: 18721867 DOI: 10.1016/j.gene.2008.07.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 07/01/2008] [Accepted: 07/28/2008] [Indexed: 11/22/2022]
Abstract
The RNF19 protein, which contains RING-finger and IBR motifs, acts as an E3 ubiquitin ligase localized to Lewy bodies. RNF19 is located on human chromosome 8q22.2, has a 4.4-kb transcript, and is ubiquitously expressed in various tissues. Here, we identified an alternative RNF19 promoter region and alternative RNF19 transcripts derived from MaLR (mammalian apparent LTR-retrotransposon) and AluJo elements. Comparative analyses indicated human-specific expression of the MaLR- and AluJo-related transcripts. From the expression analysis of 72 tissue samples including human normal, tumor, and primate tissues, three different isoforms (V1, V2, and V3) of MaLR-derived transcripts were identified. Quantitative RT-PCR analysis showed a dominant expression pattern of the V2 MaLR-derived transcript. A reporter gene assay for MaLR element promoter activity indicated that pGL2-RNF19/MaLR in the forward orientation is capable of driving luciferase gene expression in Cos7 and HCT116 cells. These findings suggest that RNF19 has acquired a new promoter and alternative exons via continuous retrotransposition events of MaLR and AluJo elements during mammalian and primate evolution, respectively.
Collapse
|
29
|
Transcriptional regulation of GSDML gene by antisense-oriented HERV-H LTR element. Arch Virol 2008; 153:1201-5. [DOI: 10.1007/s00705-008-0105-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2006] [Accepted: 04/02/2008] [Indexed: 11/25/2022]
|
30
|
Brudek T, Christensen T, Hansen HJ, Petersen T, Møller-Larsen A. Synergistic immune responses induced by endogenous retrovirus and herpesvirus antigens result in increased production of inflammatory cytokines in multiple sclerosis patients. Scand J Immunol 2008; 67:295-303. [PMID: 18261041 DOI: 10.1111/j.1365-3083.2007.02067.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human endogenous retroviruses (HERV) and herpesviruses are increasingly associated with the pathogenesis of the neurological inflammatory disease multiple sclerosis (MS). Herpesviruses are capable of HERV activation and simultaneous presence of HERV and herpesvirus antigens have a synergistic effect on cell-mediated immune responses, which tend to be higher in MS patients in comparison with healthy individuals. Here, we investigate whether these synergistic immune responses are reflected in changes in the production of proinflammatory cytokines. Using enzyme-linked immunosorbent assays (ELISAs), we have performed a comparative study between MS patients and healthy controls to investigate the production of interferon (IFN)-gamma, interleukin (IL) 2, or IL-10 as well as the balance between Th1 and Th2 responses in supernatants from peripheral blood mononuclear cells (PBMC) stimulated with HERV and herpes antigen combinations. We have found a significant disproportion in Th1/Th2 responses in PBMCs from MS patients caused by the joint presence of HERV and herpes antigens. The results also showed a significantly higher IFN-gamma production in cells from MS patients; additionally, this production correlated with the synergistic cell proliferations whereas we did not find such a correlation in healthy controls. Our findings suggest that the increased production of IFN-gamma and the induced imbalance in Th1/Th2 responses favouring the inflammatory reactions in MS patients may lead to progression of the disease.
Collapse
Affiliation(s)
- T Brudek
- Department of Medical Microbiology and Immunology, University of Aarhus, Aarhus, Denmark.
| | | | | | | | | |
Collapse
|
31
|
Lee YK, Chew A, Phan H, Greenhalgh DG, Cho K. Genome-wide expression profiles of endogenous retroviruses in lymphoid tissues and their biological properties. Virology 2008; 373:263-73. [PMID: 18187179 DOI: 10.1016/j.virol.2007.10.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2007] [Revised: 08/21/2007] [Accepted: 10/30/2007] [Indexed: 01/31/2023]
Abstract
Endogenous retroviruses (ERVs) constitute approximately 8-10% of the human and mouse genome. Some autoimmune diseases are attributed to the altered expression of ERVs. In this study, we examined the ERV expression profiles in lymphoid tissues and analyzed their biological properties. Tissues (spleen, thymus, and lymph nodes [axillary, inguinal, and mesenteric]) from C57BL/6J mice were analyzed for differential murine ERV (MuERV) expression by RT-PCR examination of polymorphic U3 sequences. Each tissue had a unique profile of MuERV expression. A genomic map identifying 60 putative MuERVs was established using 22 unique U3s as probes and their biological properties (primer binding site, coding potential, transcription regulatory element, tropism, recombination event, and integration age) were characterized. Interestingly, 12 putative MuERVs retained intact coding potentials for all three polypeptides essential for virus assembly and replication. We suggest that MuERV expression is differentially regulated in conjunction with the transcriptional environment of individual lymphoid tissues.
Collapse
Affiliation(s)
- Young-Kwan Lee
- Burn Research, Shriners Hospitals for Children and Department of Surgery, University of California, Davis, 2425 Stockton Blvd., Sacramento, CA 95817, USA
| | | | | | | | | |
Collapse
|
32
|
Variable transcriptional activity of endogenous retroviruses in human breast cancer. J Virol 2007; 82:1808-18. [PMID: 18077721 DOI: 10.1128/jvi.02115-07] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Human endogenous retroviruses (HERVs) account for up to 9% of the human genome and include more than 800 elements related to betaretroviruses. While mouse mammary tumor virus (MMTV) is the accepted etiological agent of mammary tumors in mice, the role of retroviral elements in human breast cancer remains elusive. Here, we performed a comprehensive microarray-based analysis of overall retroviral transcriptional activities in 46 mammary gland tissue specimens representing pairs of nonmalignant and tumor samples from 23 patients. An analysis of nonmalignant tissue samples revealed a distinct, mammary gland-specific HERV expression profile that consists of 18 constitutively active HERV taxa. For corresponding tumor samples, a general trend toward lower levels of HERV transcription was observed, suggesting common regulatory mechanisms. In various subsets of patients, however, increased transcript levels of single class I HERV families (HERV-T, HERV-E, and HERV-F) and several class II families, including HML-6, were detected. An analysis of transcribed HML-6 sequences revealed either the activation of some or the increased activity of several proviral loci. No evidence for MMTV or human MMTV-like virus transcripts was found, indicating that transcriptionally active, MMTV analogous, exogenous viruses were not present in the breast cancer samples analyzed.
Collapse
|
33
|
Abstract
Endogenous retroviruses (ERVs) integrated into human genome after cross-species infectious events millions of years ago. Few of the ERVs retain the basic structure of the integrated proviral form of infectious retroviruses. Human endogenous retroviruses (HERVs) represent a key molecular link between the host genome and infectious viral particles. They constitute a large reservoir of viral genes that could be activated by various factors such as mutations or carcinogenic chemical exposures and so forth. Endogenous retroviruses are transmitted genetically in a Mendelian fashion through the germline as proviral DNA. Expression pattern of HERVs can influence the outcome of their presence in many forms, which can be either beneficial or detrimental to the host. ERVs have been reported to play a role in both human physiology and human pathology. Along with their expression in many disease conditions, they have also been reported to be expressed on normal peripheral blood lymphocytes, salivary glands and keratinocytes.
Collapse
Affiliation(s)
- Sunit Kumar Singh
- Center for Cellular and Molecular Biology, Section of Infectious Diseases, Hyderabad, India.
| |
Collapse
|
34
|
Wentzensen N, Coy JF, Knaebel HP, Linnebacher M, Wilz B, Gebert J, von Knebel Doeberitz M. Expression of an endogenous retroviral sequence from the HERV-H group in gastrointestinal cancers. Int J Cancer 2007; 121:1417-23. [PMID: 17546591 DOI: 10.1002/ijc.22826] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human endogenous retroviruses (HERVs) account for approximately 8% of the human genome. Since the majority of HERV elements have accumulated inactivating mutations in the viral genes, only few expressed viral open reading frames (ORFs) have been described. In this study, we have analyzed the expression of a HERV-H copy located on Xp22.3 encompassing a potential ORF immediately downstream of the viral promoter. Conventional and real time RT-PCR based expression analysis of this specific HERV-H sequence showed overexpression in 16 of 34 (47%) colorectal, 25 of 63 (40%) gastric and 2 of 12 (17%) pancreatic cancers, whereas no overexpression was detected in bronchial and cervical cancers. Normal human testis, placenta and breast tissue did not show expression of this sequence. CpG methylation analysis of the viral promoter revealed a loss of methylation in cell lines expressing the HERV-H sequence as compared to nonexpressing cell lines and lymphocyte DNA derived from healthy individuals. Further investigations of the HERV-H long terminal repeat and the HERV-H RNA are necessary to assess the functional relevance of the HERV-H expression.
Collapse
Affiliation(s)
- Nicolas Wentzensen
- Department of Applied Tumor Biology, Institute of Pathology, University of Heidelberg, Heidelberg, Germany.
| | | | | | | | | | | | | |
Collapse
|
35
|
Yao Y, Schröder J, Nellåker C, Bottmer C, Bachmann S, Yolken RH, Karlsson H. Elevated levels of human endogenous retrovirus-W transcripts in blood cells from patients with first episode schizophrenia. GENES BRAIN AND BEHAVIOR 2007; 7:103-12. [PMID: 17559415 DOI: 10.1111/j.1601-183x.2007.00334.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We previously reported on the differential presence of transcripts related to the human endogenous retrovirus (HERV)-W family in cerebrospinal fluid and plasma from patients with first-episode schizophrenia compared with control individuals. Whether this is a consequence of qualitative or quantitative differences in transcription of genomic regions harboring HERV-W elements is not known. The purpose of the present study was therefore to characterize the transcribed HERV-W elements in mononuclear cells obtained from 30 patients first hospitalized for schizophrenia-related psychosis and from 26 healthy control individuals. We observed elevated total levels of HERV-W gag (2.1-fold, P < 0.01) but not env transcripts in the cells of patients compared with controls. By using the melting temperatures of the amplicons as a proxy marker for sequence identity, no absolute qualitative differences was detected between the two groups. Mapping of the detected transcripts identified several intronic and intergenic HERV-W elements transcribed in the cells, including elements previously considered transcriptionally silent. Element-specific assays revealed elevated levels of intronic transcripts containing HERV-W gag sequence from the putative gene PTD015 on chromosome 11q13.5 (1.6-fold, P < 0.05) in the patients compared with the controls. Thus, studies aiming to further understanding of complex human disease such as schizophrenia may need to be extended beyond the strictly protein-coding fraction of the transcriptome.
Collapse
Affiliation(s)
- Y Yao
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | | | | | | | | | | | | |
Collapse
|
36
|
Sin HS, Huh JW, Kim DS, Kim TH, Ha HS, Kim WY, Park HK, Kim CM, Kim HS. Endogenous retrovirus-related sequences provide an alternative transcript of MCJ genes in human tissues and cancer cells. Genes Genet Syst 2007; 81:333-9. [PMID: 17159294 DOI: 10.1266/ggs.81.333] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The MCJ gene is a member of the DNAJ family, and its transcriptional event is controlled by methylation of the CpG island. In our study, we found LTR33 and LTR7 elements provided an alternative transcript within the MCJ gene. To detect different expression patterns between the originally reported MCJ transcript and the LTR-related transcript, we performed a RT-PCR approach using various human tissues and cancer cells. The original MCJ transcript was detected in human tissues and cancer cells, whereas the LTR-related transcript was only revealed in some cancer cells (HCT106, MCF-3, TE-1, Hela, and CCHM). We also performed a PCR analysis to compare the insertion lineage of the LTR elements with the genomic DNAs of primates, indicating that those LTR33 and LTR7 elements of HERV-H have been integrated into the primate genome at different times. Taken together, we suggest that HERV-related elements trigger transcriptome diversification during primate evolution.
Collapse
Affiliation(s)
- Ho-Su Sin
- Division of Biological Sciences, College of Natural Sciences, Pusan National University, Busan, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Schulz WA, Steinhoff C, Florl AR. Methylation of endogenous human retroelements in health and disease. Curr Top Microbiol Immunol 2006; 310:211-50. [PMID: 16909913 DOI: 10.1007/3-540-31181-5_11] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Retroelements constitute approximately 45% of the human genome. Long interspersed nuclear element (LINE) autonomous retrotransposons are predominantly represented by LINE-1, nonautonomous small interspersed nuclear elements (SINEs) are primarily represented by ALUs, and LTR retrotransposons by several families of human endogenous retroviruses (HERVs). The vast majority of LINE and HERV elements are densely methylated in normal somatic cells and contained in inactive chromatin. Methylation and chromatin structure together ensure a stable equilibrium between retroelements and their host. Hypomethylation and expression in developing germ cells opens a "window of opportunity" for retrotransposition and recombination that contribute to human evolution, but also inherited disease. In somatic cells, the presence of retroelements may be exploited to organize the genome into active and inactive regions, to separate domains and functional regions within one chromatin domain, to suppress transcriptional noise, and to regulate transcript stability. Retroelements, particularly ALUs, may also fulfill physiological roles during responses to stress and infections. Reactivation and hypomethylation of LINEs and HERVs may be important in the pathophysiology of cancer and various autoimmune diseases, contributing to chromosomal instability and chronically aberrant immune responses. The emerging insights into the pathophysiological importance of endogenous retroelements accentuate the gaps in our knowledge of how these elements are controlled in normal developing and mature cells.
Collapse
Affiliation(s)
- W A Schulz
- Urologische Klinik, Heinrich Heine Universität, Düsseldorf, Germany.
| | | | | |
Collapse
|
38
|
Nellåker C, Yao Y, Jones-Brando L, Mallet F, Yolken RH, Karlsson H. Transactivation of elements in the human endogenous retrovirus W family by viral infection. Retrovirology 2006; 3:44. [PMID: 16822326 PMCID: PMC1539011 DOI: 10.1186/1742-4690-3-44] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Accepted: 07/06/2006] [Indexed: 11/30/2022] Open
Abstract
Background Aberrant expression of human endogenous retrovirus (HERV) elements in the W family has previously been associated with schizophrenia, multiple sclerosis and preeclampsia. Little is know regarding the basal expression, transcriptional regulation and functional significance of individual HERV-elements. Since viral infections have previously been reported to transactivate retroviral long terminal repeat regions we examined the basal expression of HERV-W elements and following infections by influenza A/WSN/33 and Herpes simplex 1 viruses in human cell-lines. Methods Relative levels of transcripts encoding HERV-W elements and cellular genes were analyzed by qPCR methods. An analysis of amplicon melting temperatures was used to detect variations in the frequencies of amplicons in discrete ranges of such melting temperatures. These frequency-distributions were taken as proxy markers for the repertoires of transcribed HERV-W elements in the cells. Results We report cell-specific expression patterns of HERV-W elements during base-line conditions. Expressed elements include those with intact regulatory long terminal repeat regions (LTRs) as well as elements flanked by truncated LTRs. Subsets of HERV-W elements were transactivated by viral infection in the different cell-lines. Transcriptional activation of these elements, including that encoding syncytin, was dependent on viral replication and was not induced by antiviral responses. Serum deprivation of cells induced similar changes in the expression of HERV-W elements suggesting that the observed phenomena are, in part, an effect of cellular stress. Conclusion We found that HERV-W elements, including elements lacking regulatory LTRs, are expressed in cell-specific patterns which can be modulated by environmental influences. This brings into light that mechanisms behind the regulation of expression of HERV-W elements are more complex than previously assumed and suggests biological functions of these transcripts.
Collapse
Affiliation(s)
- Christoffer Nellåker
- The Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 171 77 Stockholm, Sweden
| | - Yuanrong Yao
- The Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 171 77 Stockholm, Sweden
| | - Lorraine Jones-Brando
- The Stanley Division of Developmental Neurovirology, The Johns Hopkins University School of Medicine, 600 N Wolfe Street, Blalock 1105, Baltimore, MD, 21287-4933, USA
| | - François Mallet
- UMR 2714 CNRS-bioMérieux, IFR128 BioSciences Lyon-Gerland Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon cedex 07, France
| | - Robert H Yolken
- The Stanley Division of Developmental Neurovirology, The Johns Hopkins University School of Medicine, 600 N Wolfe Street, Blalock 1105, Baltimore, MD, 21287-4933, USA
| | - Håkan Karlsson
- The Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 171 77 Stockholm, Sweden
| |
Collapse
|
39
|
Sin HS, Huh JW, Kim DS, Kang DW, Min DS, Kim TH, Ha HS, Kim HH, Lee SY, Kim HS. Transcriptional control of the HERV-H LTR element of the GSDML gene in human tissues and cancer cells. Arch Virol 2006; 151:1985-94. [PMID: 16625320 DOI: 10.1007/s00705-006-0764-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 03/10/2006] [Indexed: 01/25/2023]
Abstract
Long terminal repeats (LTRs) of human endogenous retroviruses (HERVs) have been reported to serve as alternative promoters in functional genes. The GSDML (gasdermin-like protein) gene located on human chromosome 17q21 has been found to be an oncogenomic recombination hotspot. Here, we identified the LTR element of HERV-H with reverse orientation as an alternative promoter of the GSDML gene and analyzed its expression pattern in human tissues and cancer cells. A reporter gene assay of the promoter activity of the LTR on the GSDML gene in human cancer cell lines (HCT-116 and HeLa) and a kidney cell line (Cos7) of African green monkey indicated that the LTR promoter with reverse orientation had stronger promoter activity than forward one. The transcripts of this LTR-derived promoter were widely distributed in various human tissues and cancer cells, whereas the transcripts of the cellular promoter were found only in stomach tissues and some cancer cells (HCT116, MCF7, U937, C-33A, and PC3). These findings suggest that the LTR element on the GSDML gene was integrated into the hominoid lineage and acquired the role of transcriptional regulation of human tissues and cancer cells.
Collapse
Affiliation(s)
- H-S Sin
- Division of Biological Sciences, College of Natural Sciences, Pusan National University, Busan, Korea
| | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Ruprecht K, Obojes K, Wengel V, Gronen F, Kim KS, Perron H, Schneider-Schaulies J, Rieckmann P. Regulation of human endogenous retrovirus W protein expression by herpes simplex virus type 1: Implications for multiple sclerosis. J Neurovirol 2006; 12:65-71. [PMID: 16595376 DOI: 10.1080/13550280600614973] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The multiple sclerosis-associated retrovirus (MSRV), originally identified in cell cultures from patients with multiple sclerosis (MS), is closely related to the human endogenous retrovirus family W (HERV-W). Recently, HERV-W gag and env protein expression was demonstrated in MS lesions in situ. Here, the authors show that HERV-W gag and env proteins are induced by herpes simplex virus type 1 (HSV-1) in neuronal and brain endothelial cells in vitro. The transactivation of HERV-W proteins by HSV-1 could enhance their potential oligodendrotoxic and immunopathogenic effects, representing a mechanism by which HSV-1, and possibly also other herpesviruses associated with MS, may be linked to the pathogenesis of this disease.
Collapse
Affiliation(s)
- Klemens Ruprecht
- Department of Neurology, Clinical Research Unit for Multiple Sclerosis and Neuroimmunology, Würzburg, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Brosius J. Echoes from the past--are we still in an RNP world? Cytogenet Genome Res 2005; 110:8-24. [PMID: 16093654 DOI: 10.1159/000084934] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Accepted: 05/04/2004] [Indexed: 11/19/2022] Open
Abstract
Availability of the human genome sequence and those of other species is unmeasured in their value for a comprehensive understanding of the architecture, function and evolution of genomes and cells. Various mechanisms keep genomes in flux and generate intra- and interspecies variation. The conversion of RNA modules into DNA and their more or less random integration into chromosomes (retroposition) is in many lineages including our own the most pervasive and perhaps the most enigmatic. The proclivity of such events in extant multicellular eukaryotes, even in more recent evolutionary times, gives the impression that the transition period from the RNP (ribonucleoprotein) world to the emergence of modern cells, where DNA became the predominant carrier of genetic information, has lasted billions of years and is an endlessly drawn-out process rather than the punctuated event one might expect. Apart from the impact of such RNA-mediated processes as retroposition, the role of RNA in a wide variety of cellular functions has only recently become more widely appreciated.
Collapse
Affiliation(s)
- J Brosius
- Institute of Experimental Pathology, ZMBE, University of Munster, Munster, Germany.
| |
Collapse
|
42
|
Frank O, Giehl M, Zheng C, Hehlmann R, Leib-Mösch C, Seifarth W. Human endogenous retrovirus expression profiles in samples from brains of patients with schizophrenia and bipolar disorders. J Virol 2005; 79:10890-901. [PMID: 16103141 PMCID: PMC1193590 DOI: 10.1128/jvi.79.17.10890-10901.2005] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Accepted: 05/20/2005] [Indexed: 11/20/2022] Open
Abstract
The detection and identification of retroviral transcripts in brain samples, cerebrospinal fluid, and plasma of individuals with recent-onset schizophrenia and schizoaffective disorders suggest that activation or upregulation of distinct human endogenous retroviruses (HERVs) may play a role in the etiopathogenesis of neuropsychiatric diseases. To test this hypothesis, we performed a comprehensive microarray-based analysis of HERV transcriptional activity in human brains. We investigated 50 representative members of 20 HERV families in a total of 215 brain samples derived from individuals with schizophrenia or bipolar disorders and matched controls. A characteristic brain-specific retroviral activity profile was found that consists of members of the class I families HERV-E, HERV-F, and ERV9 and members of HERV-K taxa. In addition to these constitutively expressed HERVs, a number of differentially active HERV elements were identified in all brain samples independent of the disease pattern that may reflect differences in the genetic background of the tested individuals. Only a subgroup of the HML-2 family (HERV-K10) was significantly overrepresented in both bipolar-disorder- and schizophrenia-associated samples compared to healthy brains, suggesting a potential association with disease. Real-time PCR analysis of HERV env transcripts with coding capacity potentially involved in neuroinflammatory conditions revealed that env expression of HERV-W, HERV-FRD, and HML-2 remains unaffected regardless of the clinical picture. Our data suggest that HERV transcription in brains is weakly correlated with schizophrenia and related diseases but may be influenced by the individual genetic background, brain-infiltrating immune cells, or medical treatment.
Collapse
Affiliation(s)
- Oliver Frank
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Germany.
| | | | | | | | | | | |
Collapse
|
43
|
Dunn CA, van de Lagemaat LN, Baillie GJ, Mager DL. Endogenous retrovirus long terminal repeats as ready-to-use mobile promoters: the case of primate beta3GAL-T5. Gene 2005; 364:2-12. [PMID: 16112824 DOI: 10.1016/j.gene.2005.05.045] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 02/18/2005] [Accepted: 05/30/2005] [Indexed: 11/23/2022]
Abstract
Throughout the course of vertebrate evolution, germline retroviral infections have resulted in heritable provirus insertions into host DNA. These endogenous retroviruses (ERVs) contain long terminal repeat (LTR) promoters that can be adopted for use by nearby host genes. It is not known whether the transcription factor (TF) binding sites and tissue-specificities of modern LTR gene promoters have been retained since the time of ERV insertion, or if these features evolved later as the LTR became involved in host gene regulation. To address this issue, we have conducted a case study of the ERV-L LTR promoter of human beta1,3-galactosyltransferase 5 (beta3GAL-T5). We have previously shown that the human beta3GAL-T5 LTR promoter is responsible for the majority of gene transcripts in the colon. The murine beta3gal-t5 gene is also expressed primarily in the colon, despite the absence of an orthologous ERV-L LTR in the mouse genome. We therefore hypothesized that both the ERV-L LTR and the non-retroviral ancestral beta3GAL-T5 promoter were active in the colon at the time of ERV insertion. In support of this hypothesis, we have shown that the orthologous LTRs of four non-human primates are also active in a human colorectal cell line, and that the baboon LTR is active in primary baboon colon tissue. We also present evidence that the functional TF binding sites of the human beta3GAL-T5 LTR promoter were present in the original consensus sequence for this class of LTRs. Upon similar analysis of other ERV sequences, we have concluded that this evolutionary history is shared by certain other LTR gene promoters, and may be a general phenomenon.
Collapse
Affiliation(s)
- Catherine A Dunn
- Terry Fox Laboratory, BC Cancer Agency, Vancouver, British Columbia, Canada V5Z 1L3
| | | | | | | |
Collapse
|
44
|
Andersson AC, Yun Z, Sperber GO, Larsson E, Blomberg J. ERV3 and related sequences in humans: structure and RNA expression. J Virol 2005; 79:9270-84. [PMID: 15994821 PMCID: PMC1168766 DOI: 10.1128/jvi.79.14.9270-9284.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ERV3 locus at chromosome 7q11 is a much studied human endogenous retroviral (HERV) sequence, owing to an env open reading frame (ORF) and placental RNA and protein expression. An analysis of the human genome demonstrated that ERV3 is one of a group of 41 highly related elements (ERV3-like HERVs) which use proline, isoleucine, or arginine tRNA in their primer binding sites. In addition to elements closely related to ERV3, the group included the previously known retinoic acid-inducible element, RRHERVI, also referred to as HERV15, but was separate from the related HERV-E elements. The ERV3-like elements are defective. The only element with an ORF among gag, pro, pol, and env genes was the env ORF of the original ERV3 locus. A search in dbEST revealed ERV3 RNA expression in placenta, skin, carcinoid tumor, and adrenal glands. Expression was also studied with newly developed real-time quantitative PCRs (QPCR) of ERV3 and HERV-E(4-1) env sequences. Results from a novel histone 3.3 RNA QPCR result served as the expression control. QPCR results for ERV3 were compatible with previously published results, with a stronger expression in adrenal gland and placenta than in 15 other human tissues. The expression of the envelope (env) of ERV3 at chromosome 7q11 was also studied by using stringent in situ hybridization. Expression was found in corpus luteum, testis, adrenal gland, Hassal's bodies in thymus, brown fat, pituitary gland, and epithelium of the lung. We conclude that ERV3 env is most strongly expressed in adrenal and sebaceous glands as well as in placenta.
Collapse
|
45
|
Taruscio D, Mantovani A. Factors regulating endogenous retroviral sequences in human and mouse. Cytogenet Genome Res 2005; 105:351-62. [PMID: 15237223 DOI: 10.1159/000078208] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Accepted: 12/23/2003] [Indexed: 11/19/2022] Open
Abstract
Endogenous retroviruses (ERVs) are stably integrated in the genome of vertebrates and inherited as Mendelian genes. The several human ERV (HERV) families and related elements represent up to 5-8% of the DNA of our species. ERVs may be involved in the regulation of adjacent genomic loci, especially promoting the tissue-specific expression of genes; some HERVs may have functional roles, e.g., coding for the placental fusogenic protein, syncytin. This paper reviews the growing evidence about factors that may modulate ERVs, including: cell and tissue types (with special attention to placenta and germ cells), processes related to differentiation and aging, cytokines, agents that disrupt cell functions (e.g., DNA hypomethylating agents) and steroids. Special attention is given to HERVs, due to their possible involvement in autoimmunity and reproduction, as well as altered expression in some cancer types; moreover, different HERV families may deserve specific attention, due to remarkable differences concerning, e.g., expression in tissues. A comparison with factors interacting with murine ERV-related sequences indicates that the mouse may be a useful model for studying some patterns of HERV regulation. Overall, the available evidence identifies the diverse, potential interactions with endogenous or exogenous factors as a promising field for investigating the roles of ERVs in physiology and disease.
Collapse
Affiliation(s)
- D Taruscio
- National Centre on Rare Diseases, Istituto Superiore di Sanità, Rome, Italy
| | | |
Collapse
|
46
|
Seifarth W, Frank O, Zeilfelder U, Spiess B, Greenwood AD, Hehlmann R, Leib-Mösch C. Comprehensive analysis of human endogenous retrovirus transcriptional activity in human tissues with a retrovirus-specific microarray. J Virol 2005; 79:341-52. [PMID: 15596828 PMCID: PMC538696 DOI: 10.1128/jvi.79.1.341-352.2005] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Retrovirus-like sequences account for 8 to 9% of the human genome. Among these sequences, about 8,000 pol-containing proviral elements have been identified to date. As part of our ongoing search for active and possibly disease-relevant human endogenous retroviruses (HERVs), we have recently developed an oligonucleotide-based microarray. The assay allows for both the detection and the identification of most known retroviral reverse transcriptase (RT)-related nucleic acids in biological samples. In the present study, we have investigated the transcriptional activity of representative members of 20 HERV families in 19 different normal human tissues. Qualitative evaluation of chip hybridization signals and quantitative analysis by real-time RT-PCR revealed distinct HERV activity in the human tissues under investigation, suggesting that HERV elements are active in human cells in a tissue-specific manner. Most active members of HERV families were found in mRNA prepared from skin, thyroid gland, placenta, and tissues of reproductive organs. In contrast, only few active HERVs were detectable in muscle cells. Human tissues that lack HERV transcription could not be found, confirming that human endogenous retroviruses are permanent components of the human transcriptome. Distinct activity patterns may reflect the characteristics of the regulatory machinery in these cells, e.g., cell type-dependent occurrence of transcriptional regulatory factors.
Collapse
Affiliation(s)
- Wolfgang Seifarth
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany.
| | | | | | | | | | | | | |
Collapse
|
47
|
Prudhomme S, Oriol G, Mallet F. A retroviral promoter and a cellular enhancer define a bipartite element which controls env ERVWE1 placental expression. J Virol 2004; 78:12157-68. [PMID: 15507602 PMCID: PMC525085 DOI: 10.1128/jvi.78.22.12157-12168.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The HERV-W family contains hundreds of loci diversely expressed in several physiological and pathological contexts. A unique locus termed ERVWE1 encodes an envelope glycoprotein (syncytin) involved in hominoid placental physiology. Here we show that syncytin expression is regulated by a bipartite element consisting of a cyclic AMP (cAMP)-inducible long terminal repeat (LTR) retroviral promoter adjacent to a cellular enhancer conferring a high level of expression and placental tropism. Deletion mutant analysis showed that the ERVWE1 5' LTR contains binding sites essential for basal placental activity in the region from positions +1 to +125. The region from positions +125 to +310 represents a cAMP-responsive core HERV-W promoter active in all cell types. Site-directed mutagenesis analysis highlighted the complexity of U3 regulation. ERVWE1 placenta-specific positive (e.g., T240) and negative (e.g., G71) regulatory sites were identified, as were essential sites required for basic activity (e.g., A247). The flanking sequences of the ERVWE1 provirus contain several putative regulatory elements. The upstream HERV-H and HERV-P LTRs were found to be inactive. Conversely, the 436-bp region located between the HERV-P LTR and ERVWE1 was shown to be an upstream regulatory element (URE) which is significantly active in placenta cells. This URE acts as a tissue-specific enhancer. Genetic and functional analyses of hominoid UREs revealed large differences between UREs of members of the Hominidae and the Hylobatidae. These data allowed the identification of a positive regulatory region from positions -436 to -128, a mammalian apparent LTR retrotransposon negative regulatory region from positions -128 to -67, and a trophoblast-specific enhancer (TSE) from positions -67 to -35. Putative AP-2, Sp-1, and GCMa binding sites are essential constituents of the 33-bp TSE.
Collapse
Affiliation(s)
- Sarah Prudhomme
- UMR2714, CNRS-bioMérieux, Ecole Normale Supérieure de Lyon, 46 All. d'Italie, 69364 Lyon Cedex 07, France
| | | | | |
Collapse
|
48
|
Boonyaratanakornkit J, Chew A, Ryu DDY, Greenhalgh DG, Cho K. Murine endogenous retroviruses and their transcriptional potentials. Mamm Genome 2004; 15:914-23. [PMID: 15672595 DOI: 10.1007/s00335-004-2409-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jerry Boonyaratanakornkit
- Biochemistry and Molecular Biology Graduate Group, University of California at Davis, Davis, California 95616, USA
| | | | | | | | | |
Collapse
|
49
|
Khodosevich K, Lebedev Y, Sverdlov ED. Large-scale determination of the methylation status of retrotransposons in different tissues using a methylation tags approach. Nucleic Acids Res 2004; 32:e31. [PMID: 14973327 PMCID: PMC373429 DOI: 10.1093/nar/gnh035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Revised: 01/24/2004] [Accepted: 01/24/2004] [Indexed: 12/13/2022] Open
Abstract
A technique for simultaneous determination of the methylation status of numerous loci containing retroelements (REs) is reported. It is based on the observation that methylated and unmethylated areas in the genome are usually extended, and therefore the methylation of particular methyl-sensitive restriction endonuclease recognition sites might reflect the methylation status of DNA regions around them. The method includes dot-blot hybridization of repeat flanking sequences arrayed on a solid support with specifically amplified flanking regions of presumably unmethylated repeats. A multitude of flanking regions of REs adjacent to unmethylated restriction sites are amplified simultaneously, providing a complex hybridization probe. The technique thus allows the determination of the methylation status of restriction sites, which serve as tags of the methylation status of the surrounding regions. The validity of the technique was confirmed by various means, including bisulfite sequencing. The technique was successfully applied to the identification of methylation patterns of the regions surrounding 38 human-specific HERV-K(HML-2) long terminal repeats in cerebellum- and lymph node-derived genomic DNAs. The described technique can be readily adapted to the use of DNA microarray technology.
Collapse
Affiliation(s)
- Konstantin Khodosevich
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, 16/10 Miklukho-Maklaya St., 117997 Moscow, Russia.
| | | | | |
Collapse
|
50
|
Mallet F, Bouton O, Prudhomme S, Cheynet V, Oriol G, Bonnaud B, Lucotte G, Duret L, Mandrand B. The endogenous retroviral locus ERVWE1 is a bona fide gene involved in hominoid placental physiology. Proc Natl Acad Sci U S A 2004; 101:1731-6. [PMID: 14757826 PMCID: PMC341840 DOI: 10.1073/pnas.0305763101] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The definitive demonstration of a role for a recently acquired gene is a difficult task, requiring exhaustive genetic investigations and functional analysis. The situation is indeed much more complicated when facing multicopy gene families, because most or portions of the gene are conserved among the hundred copies of the family. This is the case for the ERVWE1 locus of the human endogenous retrovirus W family (HERV-W), which encodes an envelope glycoprotein (syncytin) likely involved in trophoblast differentiation. Here we describe, in 155 individuals, the positional conservation of this locus and the preservation of the envelope ORF. Sequencing of the critical elements of the ERVWE1 provirus showed a striking conservation among the 48 alleles of 24 individuals, including the LTR elements involved in the transcriptional machinery, the splice sites involved in the maturation of subgenomic Env mRNA, and the Env ORF. The functionality and tissue specificity of the 5' LTR were demonstrated, as well as the fusogenic activity of the envelope polymorphic variants. Such functions were also shown to be preserved in the orthologous loci isolated from chimpanzee, gorilla, orangutan, and gibbon. This functional preservation among humans and during evolution strongly argued for the involvement of this recently acquired retroviral envelope glycoprotein in hominoid placental physiology.
Collapse
Affiliation(s)
- François Mallet
- Unité Mixte de Recherche 2142, Centre National de la Recherche Scientifique-bioMérieux, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
| | | | | | | | | | | | | | | | | |
Collapse
|