Human endogenous retrovirus K106 (HERV-K106) was infectious after the emergence of anatomically modern humans.

HERV-K113 and HERV-K115 have been considered to be among the youngest HERVs because they are the only known full-length proviruses that are insertionally polymorphic and maintain the open reading frames of their coding genes. However, recent data suggest that HERV-K113 is at least 800,000 years old, and HERV-K115 even older. A systematic study of HERV-K HML2 members to identify HERVs that may have infected the human genome in the more recent evolutionary past is lacking. Therefore, we sought to determine how recently HERVs were exogenous and infectious by examining sequence variation in the long terminal repeat (LTR) regions of all full-length HERV-K loci. We used the traditional method of inter-LTR comparison to analyze all full length HERV-Ks and determined that two insertions, HERV-K106 and HERV-K116 have no differences between their 5' and 3' LTR sequences, suggesting that these insertions were endogenized in the recent evolutionary past. Among these insertions with no sequence differences between their LTR regions, HERV-K106 had the most intact viral sequence structure. Coalescent analysis of HERV-K106 3' LTR sequences representing 51 ethnically diverse individuals suggests that HERV-K106 integrated into the human germ line approximately 150,000 years ago, after the emergence of anatomically modern humans

Generation of Transgenic Mice to Evaluate Promoter Activity and Specificity of Two Human Endogenous Retrovirus Long Terminal Repeats = Untersuchungen zur Promotor-Aktivität und -Spezifität von zwei Long Terminal Repeats humaner endogener Retroviren in transgenen Mäusen

Generation of Transgenic Mice to Evaluate Promoter Activity and Specificity of two Human Endogenous Retrovirus Long Terminal Repeats Human Endogenous Retrovirus Long Terminal Repeats (HERV-LTRs) comprise 1.8% of the human genome (52.7 Mb). These sequences contain all the signal structures necessary for the regulation of gene transcription, such as promoters, enhancers and transcription factor binding sites. There is evidence that HERV-LTRs regulate gene expression in tissue-specific manner. This potential could be used to drive the expression of therapeutic genes, delivered by retroviral vector systems, in a safe and efficient manner. The HERV-H-H6 LTR and the HERV-L LTR were chosen for the generation of transgenic mice. Their promoter activity and specificity had prior been tested in a luciferase expression vector in vitro (Schoen et al., 2001). HERV-L was cloned into a luciferase expression vector and HERV-H-H6 was inserted into a enhanced green fluorescent protein (EGFP) expression vector. Transgenic mice were generated by DNAmicroinjection into pronuclei of zygotes. One pBL-HERV-L transgenic line and four pEGFP-HERV-H-H6 transgenic lines were established and analyzed. While the HERV-L promoter was not active in transgenic animals, pEGFP-HERV-H-H6 was expressed in gonads of mice of two transgenic lines. As only a single, non-expressing transgenic line was available, HERV-L promoter activity and specificity could not be evaluated. Additional transgenic lines have to be established. Expression level and pattern of the HERV-H-H6 promoter indicate specificity for gonad tissue. Whether the HERV-H-H6 promoter activity is linked to steroid production in cells remains to be clarified. Evaluating promoter activity in transgenic mice in two different expression vectors is not exclusively about the promoters, but also involves knowledge about the reporter genes. Advantages and limits of current applications of both luciferase and EGFP (with focus on the EGFP gene) are described in REVIEW OF THE LITERATURE. The conjunction of EGFP with the HERV-H-H6 promoter is to be seen critically, as all published methods for detection of EGFP in mice are described with EGFP linked to strong promoters. Problems like autofluorescence in fluorescence microscopy might be encountered when weaker promoters, such as HERV-LTRs, drive EGFP expression.Untersuchungen zur Promotor-Aktivität und –Spezifität von zwei Long Terminal Repeats humaner endogener Retroviren in transgenen Mäusen 1.8% des humanen Genoms bestehen aus Long Terminal Repeats Humaner Endogener Retroviren (HERV-LTRs). Solche Sequenzen enthalten alle Strukturen, die für die Regulierung von Transkription benötigt werden: Promotoren, Enhancer and Bindungsstellen für Transkriptionsfaktoren. Es gibt Hinweise, daß HERV-LTRs die Expression von Genen gewebespezifisch regulieren können. Eingebaut in retrovirale Genfähren, könnten HERV-LTRs therapeutische Gene sicher und effizient aktivieren. Zur Generierung transgener Mäuse wurden der HERV-H-H6 LTR und der HERV-L LTR ausgewählt. Deren Promoter Eigenschaften, wie Aktivität und Gewebespezifität, waren bereits in vitro untersucht worden (Schoen et al., 2001). Der HERV-L LTR wurde in einen Luciferase Expressionsvektor und der HERV-H-H6 LTR in einen Enhanced Green Fluorescent Protein (EGFP) Expressionsvektor kloniert. Transgene Mäuse enstanden durch DNA-Mikroinjektion in den Vorkern von Zygoten. Eine pBL-HERV-L transgene Linie und vier pEGFP-HERV-H-H6 transgene Linien wurden gezüchtet und auf Integration sowie Expression der Genkonstrukte untersucht. Während der HERV-L Promoter keine Aktivität zeigte, war Expression von pEGFP-HERV-H-H6 in Keimdrüsen von Mäusen aus zwei transgenen Linien nachweisbar. Da für das Genkonstrukt pBL-HERV-L nur eine einzige, nicht-exprimierende transgene Linie aufgebaut werden konnte, können keine Aussagen über die Aktivität und Gewebespezifität des HERV-L Promoters getroffen werden. Zu diesem Zwecke müssten weitere pBL-HERV-L transgene Linien untersucht werden. Das Expressionsmuster des pEGFP-HERV-H-H6 Genkonstruktes, weißt auf eine mögliche Gewebespezifität für Keimdrüsen hin. Eine eventuelle Verknüpfung der Aktivität des HERV-H-H6 LTRs mit der Produktion von Steroidhormonen müsste weitergehend geklärt werden.Da in dieser Arbeit zwei unterschiedliche Reportergen Systeme in der Maus angewandt wurden, sind im Literaturteil Vorteile und Einschränkungen von aktuellen Nachweisverfahren beider Reportergene, mit Schwerpunkt EGFP, in Mausgewebe zusammengefasst. Die Verbindung von EGFP mit dem HERV-H-H6 Promoter ist als kritisch zu beurteilen: Alle beschriebenen Nachweisverfahren für EGFP in der Maus gründen auf Mausmodellen, in denen das EGFP von einem starken Promoter kontrolliert wurde. Bei potenziell schwächeren Promotoren, wie HERV-LTRs, können Probleme auftreten, wie z.B. Autofluoreszenz bei der Fluoreszenzmikroskopie

Co-option of an endogenous retrovirus envelope for host defense in hominid ancestors

Endogenous retroviral sequences provide a molecular fossil record of ancient infections whose analysis might illuminate mechanisms of viral extinction. A close relative of gammaretroviruses, HERV-T, circulated in primates for ~25 million years (MY) before apparent extinction within the past ~8 MY. Construction of a near-complete catalog of HERV-T fossils in primate genomes allowed us to estimate a ~32 MY old ancestral sequence and reconstruct a functional envelope protein (ancHTenv) that could support infection of a pseudotyped modern gammaretrovirus. Using ancHTenv, we identify monocarboxylate transporter-1 (MCT-1) as a receptor used by HERV-T for attachment and infection. A single HERV-T provirus in hominid genomes includes an env gene (hsaHTenv) that has been uniquely preserved. This apparently exapted HERV-T env could not support virion infection but could block ancHTenv mediated infection, by causing MCT-1 depletion from cell surfaces. Thus, hsaHTenv may have contributed to HERV-T extinction, and could also potentially regulate cellular metabolism

Transcriptionally active HERV-H retrotransposons demarcate topologically associating domains in human pluripotent stem cells.

Chromatin architecture has been implicated in cell type-specific gene regulatory programs, yet how chromatin remodels during development remains to be fully elucidated. Here, by interrogating chromatin reorganization during human pluripotent stem cell (hPSC) differentiation, we discover a role for the primate-specific endogenous retrotransposon human endogenous retrovirus subfamily H (HERV-H) in creating topologically associating domains (TADs) in hPSCs. Deleting these HERV-H elements eliminates their corresponding TAD boundaries and reduces the transcription of upstream genes, while de novo insertion of HERV-H elements can introduce new TAD boundaries. The ability of HERV-H to create TAD boundaries depends on high transcription, as transcriptional repression of HERV-H elements prevents the formation of boundaries. This ability is not limited to hPSCs, as these actively transcribed HERV-H elements and their corresponding TAD boundaries also appear in pluripotent stem cells from other hominids but not in more distantly related species lacking HERV-H elements. Overall, our results provide direct evidence for retrotransposons in actively shaping cell type- and species-specific chromatin architecture

Vaccination directed against the human endogenous retrovirus-K envelope protein inhibits tumor growth in a murine model system

Human endogenous retrovirus (HERV) genomes are chromosomally integrated in all cells of an individual. They are normally transcriptionally silenced and transmitted only vertically. Enhanced expression of HERV-K accompanied by the emergence of anti-HERV-K-directed immune responses has been observed in tumor patients and HIV-infected individuals. As HERV-K is usually not expressed and immunological tolerance development is unlikely, it is an appropriate target for the development of immunotherapies. We generated a recombinant vaccinia virus (MVA-HKenv) expressing the HERV-K envelope glycoprotein (ENV), based on the modified vaccinia virus Ankara (MVA), and established an animal model to test its vaccination efficacy. Murine renal carcinoma cells (Renca) were genetically altered to express E. coli beta-galactosidase (RLZ cells) or the HERV-K ENV gene (RLZ-HKenv cells). Intravenous injection of RLZ-HKenv cells into syngenic BALB/c mice led to the formation of pulmonary metastases, which were detectable by X-gal staining. A single vaccination of tumor-bearing mice with MVA-HKenv drastically reduced the number of pulmonary RLZ-HKenv tumor nodules compared to vaccination with wild-type MVA. Prophylactic vaccination of mice with MVA-HKenv precluded the formation of RLZ-HKenv tumor nodules, whereas wild-type MVA-vaccinated animals succumbed to metastasis. Protection from tumor formation correlated with enhanced HERV-K ENV-specific killing activity of splenocytes. These data demonstrate for the first time that HERV-K ENV is a useful target for vaccine development and might offer new treatment opportunities for diverse types of cancer

The association between human endogenous retroviruses and multiple sclerosis: a systematic review and meta-analysis

Background: The interaction between genetic and environmental factors is crucial to multiple sclerosis (MS) pathogenesis. Human Endogenous Retroviruses (HERVs) are endogenous viral elements of the human genome whose expression is associated with MS. Objective: To perform a systematic review and meta-analysis and to assess qualitative and quantitative evidence on the expression of HERV families in MS patients. Methods: Medline, Embase and the Cochrane Library were searched for published studies on the association of HERVs and MS. Meta-analysis was performed on the HERV-W family. Odds Ratio (OR) and 95% confidence interval (CI) were calculated for association. Results: 43 reports were extracted (25 related to HERV-W, 13 to HERV-H, 9 to HERV-K, 5 to HRES-1 and 1 to HER-15 family). The analysis showed an association between expression of all HERV families and MS. For HERV-W, adequate data was available for meta-analysis. Results from meta-analyses of HERV-W were OR = 22.66 (95%CI 6.32 to 81.20) from 4 studies investigating MSRV/HERV-W(MS-associated retrovirus) envelope mRNA in peripheral blood mononuclear cells, OR = 44.11 (95%CI 12.95 to 150.30) from 6 studies of MSRV/ HERV-W polymerase mRNA in serum/plasma and OR = 6.00 (95%CI 3.35 to 10.74) from 4 studies of MSRV/HERV-W polymerase mRNA in CSF

Human Endogenous Retrovirus K106 (HERV-K106) Was Infectious after the Emergence of Anatomically Modern Humans

HERV-K113 and HERV-K115 have been considered to be among the youngest HERVs because they are the only known full-length proviruses that are insertionally polymorphic and maintain the open reading frames of their coding genes. However, recent data suggest that HERV-K113 is at least 800,000 years old, and HERV-K115 even older. A systematic study of HERV-K HML2 members to identify HERVs that may have infected the human genome in the more recent evolutionary past is lacking. Therefore, we sought to determine how recently HERVs were exogenous and infectious by examining sequence variation in the long terminal repeat (LTR) regions of all full-length HERV-K loci. We used the traditional method of inter-LTR comparison to analyze all full length HERV-Ks and determined that two insertions, HERV-K106 and HERV-K116 have no differences between their 5′ and 3′ LTR sequences, suggesting that these insertions were endogenized in the recent evolutionary past. Among these insertions with no sequence differences between their LTR regions, HERV-K106 had the most intact viral sequence structure. Coalescent analysis of HERV-K106 3′ LTR sequences representing 51 ethnically diverse individuals suggests that HERV-K106 integrated into the human germ line approximately 150,000 years ago, after the emergence of anatomically modern humans.</p

HERVs, transposons and human diseases : part II

Part 1 and part 3 of the article can be found through this link : https://www.um.edu.mt/library/oar//handle/123456789/12961 https://www.um.edu.mt/library/oar//handle/123456789/13132Part 2 of the article. It has been found that the human genome is full of relic retroviral DNA sequences called HERVs (Human Endogenous RetroViruses). A HERV is a type of a transposon, the latter being a piece of DNA sequence that can move from one position to another position in the genome, hence its other name of ‘jumping gene’. HERVs and other transposons are held in check from doing havoc in the genome by several mechanisms, one of which is epigenetic in nature (namely DNA methylation and histone modifications). HERVs and other transposons are being implicated to have physiological and pathological functions in the genomes of the cells that host them. Accumulating evidence is showing that they may be associated with certain human diseases, specifically in some autoimmune diseases (e.g. rheumatoid arthritis, psoriasis, systemic lupus erythematosus, insulin-dependent diabetes mellitus), neurological diseases (e.g. schizophrenia, multiple sclerosis, motor neuron disease) and cancer. Understanding how these relic viruses and other jumping genes bring about these human diseases could help in their prevention and treatment.peer-reviewe

Expression pattern analysis of transcribed HERV sequences is complicated by ex vivo recombination

<p>Abstract</p> <p>Background</p> <p>The human genome comprises numerous human endogenous retroviruses (HERVs) that formed millions of years ago in ancestral species. A number of loci of the HERV-K(HML-2) family are evolutionarily much younger. A recent study suggested an infectious HERV-K(HML-2) variant in humans and other primates. Isolating such a variant from human individuals would be a significant finding for human biology.</p> <p>Results</p> <p>When investigating expression patterns of specific HML-2 proviruses we encountered HERV-K(HML-2) cDNA sequences without proviral homologues in the human genome, named HERV-KX, that could very well support recently suggested infectious HML-2 variants. However, detailed sequence analysis, using the software RECCO, suggested that HERV-KX sequences were produced by recombination, possibly arising <it>ex vivo</it>, between transcripts from different HML-2 proviral loci.</p> <p>Conclusion</p> <p>As RT-PCR probably will be instrumental for isolating an infectious HERV-K(HML-2) variant, generation of "new" HERV-K(HML-2) sequences by <it>ex vivo </it>recombination seems inevitable. Further complicated by an unknown amount of allelic sequence variation in HERV-K(HML-2) proviruses, newly identified HERV-K(HML-2) variants should be interpreted very cautiously.</p