Le sepsis est défini par l’apparition de dysfonctions d’organes, multiples et mortelles, causées par une réponse de l’hôte dérégulée suite à une infection. L’hétérogénéité de la maladie représente un défi clinique majeur au regard de la prise en charge thérapeutique, et à ce jour les marqueurs proposés ne suffisent pas à stratifier les patients. Les rétrovirus endogènes humains (HERV) pourraient être des marqueurs pertinents,compte tenu des propriétés immunosuppressives de leurs enveloppes et de leur expression dans des maladies inflammatoires et auto-immunes. Cette thèse a pour objectif de savoir dans quelle mesure les HERV sont exprimés et modulés, dans des conditions d’inflammation et d’immunosuppression. Pour cela,nous avons utilisé une puce à ADN haute densité permettant (i) l’analyse de la transcription de 363 689HERV et 1500 gènes, et (ii) une lecture fonctionnelle de l’activité des LTR. L’expression des HERV a été objectivée (i) dans un modèle ex-vivo de tolérance à l’endotoxine sur des cellules mononuclées du sang périphérique (PBMC) d’individus sains et (ii) sur sang total provenant d’individus sains et de patients en choc septique, stratifiés ou non en fonction du statut immunitaire. (1) De 5,6% à 6,9% des HERV sont exprimés dans le compartiment sanguin et environ 20% des LTR possèdent une fonction promotrice ou polyA, les deux fonctions étant mutuellement exclusives. (2) Le contenu du transcriptome HERV est modulé ex vivo dans le contexte de tolérance à l’endotoxine laissant apparaitre deux grands phénotypes transcriptionnels. L’expression de certains loci HERV est corrélée au statut immunitaire de patient septique.L’évaluation d’une signature moléculaire complexe sur une cohorte de validation, permet la séparation en deux groupes présentant des critères de sévérité distincts, suggérant les HERV/MaLR comme biomarqueurs de stratification. (3) L’analyse de la co-expression des gènes et des HERV a permis d’intégrer ceux-ci au sein de réseaux associées à la réponse de l’hôte et de proposer des hypothèses fonctionnelles. / Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection.The heterogeneity of the disease present a major clinical challenge with regard to the therapeutic coverage,and this day the proposed markers are not enough to stratify patients. The human endogenous retrovirus(HERV) could be relevant markers, considering the immunosuppressives properties of their envelopes andtheir expression in inflammatory and autoimmune disease. The aim of this thesis is to know to what extentthe HERVs are expressed and modulated, in inflammatory and immunocompromised contexts. For this, weused a high density DNA chip allowing (i) the transcription analysis of 363,689 HERV and 1500 genes,and (ii) a functional reading of LTRs activities. The HERVs expression was objectified (i) in endotoxintolerance ex vivo model in peripheral blood mononuclear cells (PBMCs) of healthy volunteers and (ii) inwhole blood of healthy volunteers and septic shock patients, stratified or not according to immunity state.(1) Of 5,6% at 6,9% of HERVs are expressed in the blood compartment and around 20% of LTRs have apromoter or polyA function, both functions being mutually exclusive. (2) The HERV transcriptome ismodulated in ex vivo endotoxin tolerance model letting appear two higher transcriptional phenotypes. Theexpression of some HERVs loci are correlated of the immunity state of the septic shock patients. Theevaluation of molecular signature in validation cohort, allowed to separate in two patients groupspresenting different severity criteria, suggesting HERV/MaLR as biomarkers of stratification. (3) The coexpressedanalysis of genes and HERVs allowed to integrate these within signaling pathways associated atthe host immune response and to provide functional hypothesis.

Human endogenous retroviruses (HERVs) constitute about 8% of the human genome. There are around 4000 pol-containing retroviral integrations in the human genome, which makes it impractical to measure each of them separately. Therefore we developed a set of degenerate real time PCRs to detect major groups bearing sequence similarities to gammaretroviruses, one of the largest groups of human endogenous retrovirus, and betaretroviruses, some of which have integrated into the human genome most recently and which remain the most intact. It was found that, although both gammaretroviral and betaretroviral RNAs were broadly expressed in various healthy tissues including reproductive tissues and brain, a differential expression pattern was observed. My work further revealed that HERVE and HERVW, two gammaretroviral sequences, were ubiquitously and highly expressed in pathologic and normal female reproductive tissues with tissue specific patterns. Expression of HERVE was higher in endometriotic tissue than in normal endometrium. HERVE and HERVW RNAs were higher in normal ovarian tissue than in ovarian cancer. Besides these tissue- and neoplasia-related differences, there were wide differences in HERV expression among individuals. Next, a selective pattern of HERVW upregulation was demonstrated in SK-N-DZ, a neuroblastoma cell line, upon re-oxygenation after a period of hypoxia or with 5-azacytidine, a demethylating agent. Furthermore, broad and high expressions of gammaretrovirus-like transcripts in different brain areas analyzed were identified. The expression levels were variable among different donors. In conclusion a ubiquitous HERV expression was observed in tissues and cell lines, with various patterns. At this stage the data are not sufficient to conclude whether HERV has any physiological or pathological roles in humans. However, their differential expression patterns are compatible with functional roles of HERV in humans.

Artificial divergent selection of chickens for high and low body weight at 8 weeks of age has produced two lines: the high (HWS) and low (LWS) body weight chicken lines. In addition to the difference in body weight, the lines show extreme differences in feeding behaviour and body composition. The aim of this study was to uncover the genetic and molecular factors that contribute to and determine these differences, especially regarding body energy regulation and appetite. In papers I and II, genome-wide gene expression in a brain sample containing hypothalamus and in dissected hypothalamus was analysed using DNA microarray and qRT-PCR. We found that levels of differential expression were generally moderate, which was consistent with the idea that polygenic factors were involved in the establishment of the chicken lines. Genes associated with neural plasticity, lipid metabolism and body energy regulation were differentially expressed. This result indicated that the neural systems regulating feeding behaviour and body weight were altered in the chicken lines. However, genes that were involved in the central melanocortin system were not systematically differentially expressed. Interestingly, the biggest differences in expression between the lines found in endogenous retrovirus sequences of the ALV subgroup E. Thus, in paper III, we characterized the number of integrations, the expression of ALVE retroviral elements and their effects on body weight. A significant correlation between low body weight and high ALVE expression was observed in female F9 birds from an HWS x LWS advanced intercross line. This implied that ev-loci contributing to increased ALVE expression levels were genetically linked to loci influencing the low body weight of the pullets. In paper IV, the carnitine palmitoyltransferase-1b gene (CPT1B), which was highly differentially expressed in the hypothalami, was investigated. We mapped chicken CPT1B to the distal tip of chromosome 1p. The levels of CPT1B mRNA in the HWS line were higher in the hypothalamus and lower in muscle than in the LWS line. This pattern of differential expression indicates that this gene could contribute to the remarkable phenotypic differences between HWS and LWS chickens. However, comparison with quantitative trait loci data showed that the expression of CPT1B is a trans effect, rather than a direct causative locus. In conclusion, the data suggested that the long-term selection for body weight resulted in differential gene expression in the brains of the selected chicken lines. These results may have relevance for the poultry industry and will also contribute to increasing knowledge about human diseases such as obesity and anorexia.

An exogenous retrovirus (XRV) that integrates into a germ cell may be inherited as a Mendelian gene; it becomes an endogenous retrovirus (ERV). The human genome consists of up to 8% HERVs. The gammaretroviral (ERV class I) HERV-H, with 926 members, is the largest ERV group. Despite millions of years since integration, it has polymorphic envelope open reading frames in at least three loci. Selections for functional envelopes are indicated on chromosomes 1 and 2. However, envelopes were present only in a fraction of the total HERV-H. Mutated polymerases, indicating old ERVs, contradicted relatively intact long terminal repeats. To explain this, we formulated a “Midwife” element theory where proteins are complemented in trans. A phylogenetic analysis did not support separate HERV-H and -F groups. The new taxonomy included HERV-H like (RGH2-like and RTVLH2-like subgroups) and Adjacent HERV-H like. A bioinformatic reconstruction of a putative ancestral HERV-H exposed novel traits. Two nucleocapsid zinc fingers and a pronounced nucleotide bias for C in the HERV-H like were unique among the gammaretroviruses. Two recently integrated gammaretroviral groups (PtNeo-I[PTERV1] and -II) were found in chimpanzees but not in humans. The PtNeo groups were most similar to baboon ERVs and a macaque sequence, but neither to other chimpanzee nor to any human gammaretroviruses. The pattern was consistent with cross-species transfer via predation. To advance the retroviral taxonomy, we projected structural markers over sequence phylogenetic trees. A number of markers were useful to distinguish between genera and to delineate groups. Basic retroviral knowledge is vital to understand emerging infections. Phylogenetic analyses of taxonomically improved sequences, facilitates the search for common retroviral denominators to target. This thesis provided new insights in retroviral evolution and taxonomy using the ERVs, with special focus on the large gammaretroviral HERV-H group, as an additional source of information next to that of XRVs.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22333号 / 医博第4574号 / 新制||医||1041(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 朝長 啓造, 教授 萩原 正敏, 教授 齊藤 博英 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Einleitung: Der seit über 30 Jahren ausgiebig erforschte Transkriptionsfaktor p53 besitzt offenbar Funktionen, die über seine bekannte und gut untersuchte Aktivität als Tumorsuppressor hinausgehen. So scheint er auch an der Regulation der menschlichen Lebenserwartung - über die Vermittlung einer allgemeinen physischen Robustheit - sowie der weiblichen Fertilität beteiligt zu sein. Insbesondere Primaten zeichnen sich durch eine vergleichsweise lange Lebenserwartung und eine lange reproduktive Phase aus. Ob p53 hier eine Rolle spielen könnte, ist unbekannt. Unsere Arbeitsgruppe entdeckte vor einigen Jahren das humane endogene Retrovirus-K (HERV-K) Protein Np9, dessen Gen sich in mehreren Kopien nur bei Menschen, Schimpansen und Gorillas findet. Weitere Untersuchungen wiesen außerdem darauf hin, dass Np9 an den Tumorsuppressor p53 zu binden vermag. Ziele der Untersuchungen: Es stellte sich also die Frage, ob die Funktion von p53 durch die Bindung an Np9 moduliert werden kann. Eine derartige Modulation des multifunktionellen Transkriptionsfaktors wäre natürlich auf Hominiden beschränkt. In der vorliegenden Arbeit sollten einige Teilaspekte der Interaktion von p53 und Np9 näher untersucht werden. Material und Methoden: Für die Bindungskartierung von p53 und Np9 wurden GST-Pulldown-Analysen durchgeführt. Die GST-Protein-Plasmide wurden in E.coli BL21 transformiert und nach Induktion mit IPTG exprimiert. Sie dienten als „Fängerproteine“ und waren dank ihres Glutathion-S-Transferase-tags in der Lage an GST-Sepharose-Kügelchen zu binden. Der putative Interaktionspartner als „Beuteprotein“ wurde in vitro translatiert und in diesem Zuge auch mit 35S radioaktiv markiert. Dann wurde er mit den an die Beads gebundenen GST-Proteinen inkubiert und anschließend die Proben auf ein SDS-Gel aufgetragen und aufgetrennt. Das Gel wurde anschließend auf eine Membran übertragen und der Blot auf einen Radioaktivfilm aufgelegt, woraufhin die Protein-Protein-Bindungen anhand des radioaktiven Beuteproteins als Banden erkennbar waren. Abschließend wurde der Blot mit GST-Antikörper inkubiert, dann am Folgetag mit Anti-Mouse-Antikörper. Mittels ECL Substrat konnte nun die Bindung der GST-getaggten Proteine an die Sepharosebeads nachgewiesen werden. Für den Electrophoretic Mobility Shift Assay wurden verschiedene Versuchsansätze pipettiert, welchen nach einer Inkubationszeit das zuvor mit 32P radioaktiv markierte Oligonukleotid zugegeben wurde. Nach erneuter Inkubation wurden die Proben auf das nicht-denaturiende EMSA-Gel aufgetragen und elektrophoretisch aufgetrennt. Dabei wurden die Protein-Oligonukleotid-Verbindungen gemäß ihrer Ladung, Größe und Konformation getrennt. Die Gele wurden im Geltrockner getrocknet und direkt mit einer Verstärkerfolie auf den Radioaktivfilm in einer Radioaktivkassette aufgelegt. Ergebnisse: Zunächst war es notwendig, die Bindung der beiden Partner biochemisch zu kartieren. Dies geschah mittels der GST-Pulldown-Analyse, in der Fragmente der Proteine exprimiert, miteinander inkubiert und schließlich kopräzipitiert wurden. Es stellte sich heraus, dass p53 mit seinem C-Terminus an Np9 bindet. Np9 hingegen band mit seinen Aminosäureresten (aa) 1-64 (ohne den C-terminus mit den aa 65-74) an p53. Das Np9-Fragment 36-74 zeigte nur eine schwache Bindung an p53. Interessanterweise band das Np9-Fragment 36-64 stärker an p53 als Volllängen-Np9 (1-74), was auf eine die Interaktion hemmende Domäne im C-Terminus von Np9 hinweisen könnte. Um zu untersuchen, ob die Bindung von Np9 an den C-Terminus von p53 die p53-DNA-Interaktion beeinflusst, wurden Electrophoretic Mobility Shift Assays (EMSAs) durchgeführt. Es konnte gezeigt werden, dass Np9-zumindest in vitro-durch Bindung an die regulatorische Domäne von p53 und in Anwesenheit des p53-aktivierenden Antikörpers PAb421 in der Lage war, die spezifische Bindungsfähigkeit von p53 an DNA zu erhöhen und somit seine Funktion als Transkriptionsfaktor zu unterstützen. Schlussfolgerungen: Die Resultate weisen also erstmals darauf hin, dass das nukleäre HERV-K Protein Np9 spezifisch in Hominiden eine p53-abhängige Tumorsuppressoreigenschaft aufweisen könnte. Weitere Untersuchungen-insbesondere in vivo-sind nun notwendig. Dies könnte auch als Forschungsgrundlage zu endogenen Retrovirusproteinen beim Pferd dienen.:1 Einleitung und Zielsetzung der Arbeit 1 2 Literaturübersicht 2 2.1 Der Tumorsuppressor p53 2 2.2 Das Kernprotein Np9 7 2.2.1 Retroviren 7 2.2.2 Endogene Retroviren 8 2.2.3 Humane endogene Retroviren 8 2.2.4 HERV-K 10 2.2.5 Das nukleäre Protein Np9 10 3 Material und Methoden 15 3.1 Material 15 3.1.1 Chemikalien 15 3.1.2 Puffer und Lösungen 17 3.1.3 Antikörper 21 3.1.4 Enzyme 22 3.1.5 Reaktionskits 22 3.1.6 Bakterienstämme 23 3.1.7 Kulturmedien 23 3.1.8 Oligonukleotide für EMSA 23 3.1.9 Größenstandards 24 3.1.10 Plasmide 26 3.2 Methoden 28 3.2.1 Nukleinsäuretechniken 28 3.2.2 Protein-Methoden 31 3.2.3 Prokaryonten 40 4 Ergebnisse 42 4.1 Interaktion zwischen Np9 und dem Tumorsuppressorprotein p53 42 4.2 GST-Pulldown 43 4.2.1 Klonierung für die GST-Pulldown-Analysen 43 4.2.2 Induktion der Proteinexpression 48 4.2.3 GST-Pulldown-Experimente 53 4.3 EMSA (Electrophoretic Mobility Shift Assay) 57 4.3.1 Radioaktive Markierung der Sonden 58 4.3.2 EMSA-Experimente 58 5 Diskussion 63 6 Zusammenfassung 68 7 Summary 70 8 Literaturverzeichnis 72 Danksagung 86 Abbildungsverzeichnis 87 Tabellenverzeichnis 88 / Introduction: The transcription factor p53, extensively investigated for over 30 years, apparently has functions which exceeds his known and well examined activity as a tumor suppressor. It seems to be involved in the regulation of the human life expectancy – by providing a general physical robustness - as well as of the female fecundity. Primates too are characterized by a comparatively long life expectancy and long reproductive phases, yet the possible influence of p53 is unknown. Our research group has discovered some years ago the Np9 protein of human endogenous retrovirus K (HERV K), which is found in several copies only with humans, chimpanzees and gorillas. Other investigations by our group suggested that Np9 might be able to interact with the tumor suppressor p53. Objective of the investigations: To study whether the function of p53 can be modulated by the interaction with Np9. Such a modulation of the multifunctional transcription factor would of course be limited to hominids. In the present work some aspects of the interaction between p53 and Np9 were analysed. Materials and methods: For the mapping of the interaction of p53 and Np9, GST pulldown assays were carried out. The GST protein plasmids were transformed in E. coli BL21 and expressed after IPTG induction. They served as bait proteins and bound to GST sepharose beads because of their Glutathione S-transferase-tags. The putative interaction partner as a prey protein was translated in vitro and radioactively marked with 35S. After being incubated with the GST-proteins bound to the beads, the samples were transferred on a SDS gel and separated. The gel was transferred to a membrane and the blot was exposed to an X-ray film. Thus, the radioactively labelled prey protein forms bands that identify the protein-protein interaction. Finally the blot was incubated with GST antibody, then on the following day with anti-mouse antibody. Using ECL-substrate it was now possible to demonstrate that the GST-tagged proteins bound to the sepharose beads. For the Electrophoretic Mobility Shift Assay different samples were prepared and, after an incubation time, the oligonucleotide radioactively marked with 32P was added. After additional incubation it was transferred on non-denaturating EMSA gel and separated by electrophoresis. Thus the protein oligonucleotide conjugates were separated according to charge, size and conformation. The gels were dried in the gel dryer, transferred to a membrane and placed against an X-ray film in a cassette. Results: Initially a biochemical mapping of the binding of the two partners had to be carried out. This was done by means of the GST pulldown assay, in which fragments of the proteins were extruded, incubated together and finally co-precipitated. It turned out that the C-terminus of p53 bound to Np9. However, Np9 bound to p53 with his amino acid residues (aa) 1-64 (lacking the C-terminal aa 65-74). The Np9 fragment 36-74 showed only a weak binding to p53. Interestingly the Np9 fragment 36-64 was binding stronger to p53 than a full length Np9 (1-74), which could point to a C-terminal domain in Np 9 inhibiting the interaction. In order to examine whether the binding of Np9 to the C-terminal of p53 affects the interaction of p53 with DNA, Electrophoretic Mobility Shift Assays (EMSAs) were carried out. It could be shown that Np9 was able to raise the specific binding ability of p53 with DNA and to support therefore its function as a transcription factor, by binding to the regulatory domain of p53 in presence of the activating p53 antibody PAB421. Conclusions: The results show for the first time that, specifically in hominids, the nuclear HERV-K protein Np9 could have a tumor suppressing quality that is dependent on p53. Further investigations, in particular in vivo, are necessary. This could be the starting point for research on equine endogenous retrovirusproteins in horses.:1 Einleitung und Zielsetzung der Arbeit 1 2 Literaturübersicht 2 2.1 Der Tumorsuppressor p53 2 2.2 Das Kernprotein Np9 7 2.2.1 Retroviren 7 2.2.2 Endogene Retroviren 8 2.2.3 Humane endogene Retroviren 8 2.2.4 HERV-K 10 2.2.5 Das nukleäre Protein Np9 10 3 Material und Methoden 15 3.1 Material 15 3.1.1 Chemikalien 15 3.1.2 Puffer und Lösungen 17 3.1.3 Antikörper 21 3.1.4 Enzyme 22 3.1.5 Reaktionskits 22 3.1.6 Bakterienstämme 23 3.1.7 Kulturmedien 23 3.1.8 Oligonukleotide für EMSA 23 3.1.9 Größenstandards 24 3.1.10 Plasmide 26 3.2 Methoden 28 3.2.1 Nukleinsäuretechniken 28 3.2.2 Protein-Methoden 31 3.2.3 Prokaryonten 40 4 Ergebnisse 42 4.1 Interaktion zwischen Np9 und dem Tumorsuppressorprotein p53 42 4.2 GST-Pulldown 43 4.2.1 Klonierung für die GST-Pulldown-Analysen 43 4.2.2 Induktion der Proteinexpression 48 4.2.3 GST-Pulldown-Experimente 53 4.3 EMSA (Electrophoretic Mobility Shift Assay) 57 4.3.1 Radioaktive Markierung der Sonden 58 4.3.2 EMSA-Experimente 58 5 Diskussion 63 6 Zusammenfassung 68 7 Summary 70 8 Literaturverzeichnis 72 Danksagung 86 Abbildungsverzeichnis 87 Tabellenverzeichnis 88

Syncytin-1 is an endogenous retroviral envelope glycoprotein specifically expressed in human placenta, where the protein was adopted for its physiological function. After interaction with specific receptors, transmembrane proteins ASCT1 and ASCT2, Syncytin-1 initiates cell-cell fusion leading to formation of multinucleated syncytiotrophoblast, which is essential for feto-maternal nutrients exchange. In this diploma thesis a new cell-cell fusion quantification assay was implemented for characterisation of Syncytin-1 fusion determinants. The assay uses Syncytin-1 and ASCT2 expressed separately with fragments of luciferase in heterologous cell-culture system. The assay enables to specifically quantify cell-cell fusions based on activity of reconstituted luciferase reporter. This study discovered new facts about the role of intracytoplasmic tail of Syncytin-1 in the process of the cell- cell fusion. This specific part of protein contains a tandem motif sensitive to changes in amino acid sequence that led to loss of fusogenic potential of Syncytin-1. It was further confirmed, that the protein Suppressyn works as an inhibitor of cell-cell fusions initiated by Syncytin-1. Suppressyn however does not bind to receptors of Syncytin-1 and the mechanism of its inhibition remains unsolved. Finally, it was demonstrated...

Daten des humanen Genomprojektes zeigen, dass ca. 8% des gesamten humanen Genoms aus retroviralen Sequenzen besteht. Der überwiegende Teil dieser Proviren ist aufgrund verschiedener Mutationen defekt. Im Gegensatz zu allen anderen HERV Proviren scheinen einige HERV-K Proviren intakt zu sein und besitzen offene Leserahmen für alle viralen Proteine. Die Familie des humanen endogenen Retrovirus K HML2 umfasst ca. 30 eng verwandte Proviren. Zusätzlich zu den Strukturproteinen Gag und Env und der Reversen Transkriptase, exprimiert HERV-K zwei regulatorische Proteine, Rec und Np9. Beide sind im Nukleus lokalisiert und tumorigene Eigenschaften bzw. eine Expression in Assoziation mit Tumorgeweben wurde nachgewiesen. Neben Zelllinien, wie die Teratokarzinomzelllinie GH und einigen Brustkrebszelllinien, für die die Expression von HERV-K mRNA und die Produktion von Viruspartikeln bekannt ist, konnte die Expression von HERV-K Proteinen und Partikeln für Melanomzellen gezeigt werden. Volllängen mRNA von HERV-K war in allen untersuchten humanen Proben nachweisbar. Gespleißtes env und rec war in 39% der Gewebe und in 38% der Melanomzelllinien exprimiert. Zusätzlich werden HERV-H, -R und -W exprimiert. Von den auf spezifische Antikörper gegen HERV-K Proteine untersuchten Seren der Melanompatienten waren 16% positiv für das transmembrane Hüllprotein, jedoch reagierte kein Serum mit Re oder Np9. Da im Zuge der Entstehung von Tumoren immer auch eine Dedifferenzierung der entarteten Zellen diskutiert wird, wurde die Expression von HERVs in undifferenzierten, embryonalen Stammzellen bestimmt. In den untersuchten embryonalen Stammzellen lässt sich Volllängen mRNA, sowie gespleißte env, rec und np9 mRNA nachweisen. Während der Differenzierung zu neuronalen Vorläuferzellen sinkt die Expression jedoch wieder auf ein mit normalen Zellen vergleichbares Niveau. Obwohl gespleißte RNA und virale Proteine von HERV-K vor allem in Tumoren und Tumorzelllinien exprimiert werden, ist deren Funktion während der Tumorentstehung noch immer ungeklärt. Auch die Bedeutung der HERV-K Expression in humanen Stammzellen ist noch unklar, insbesondere in Hinblick auf eine mögliche Tumorigenität. / In contrast to all other human endogenous retroviruses, proviruses of the human endogenous retrovirus family HERV-K have maintained open reading frames for all viral proteins. Although most proviruses are defective, structural proteins Gag and Env, the reverse transcriptase and two regulatory proteins, Rec and Np9, have been described. Rec resembles the Rev protein of HIV and tumourigenic potential was confirmed. Np9 as well is located in the nucleus and expression in association with tumour tissues was observed. Additionally to cell lines known to produce HERV-K virus particles, such as the teratocarcinoma cell line GH and breast cancer cell lines, recently melanoma cells were described to express HERV-K proteins and particles. In order to study the expression of HERV-K, -H, -R and -W, in melanoma cell lines and biopsies primer sets were used. Antisera specific for HERV-K proteins were used for immunohistochemistry and sera from melanoma patients were investigated for HERV-K specific antibodies. Full length mRNAs of all HERVs were found in all human cells. Spliced env and rec of HERV-K were detected in 39% of the melanoma biopsies and in 38% of the melanoma cell lines. Expression of HERV-K in situ was shown by immunohistochemistry. In addition, 16% of the patients sera tested showed antibodies against the HERV-K transmembrane envelope protein, but no antibodies against Np9 or Rec could be detected. A certain dedifferentiation of cells as a consequence of tumour development is discussed. Therefore the expression of HERV-K in undifferentiated embryonic stem cells was investigated. The investigated stem cells showed expression of HERV-K full length, env, rec and np9 mRNA. Although the expression decreased with differentiation to neuronal precursor cells. Even though HERV-K mRNA and proteins were expressed in a high percentage of melanomas their function in tumour development is still unclear. As well as the meaning of the HERV-K expression in embryonic stem cells, particularly for a tumourigenic potential.

No description available.

Les rétrovirus sont des virus à ARN, enveloppés présents dans de nombreuses espèces animales de rente, chez les animaux de compagnie et chez l’homme. Une des particularités des rétrovirus concerne l’intégration du génome viral au sein du génome de la cellule infectée; cette intégration est réalisée par une enzyme virale, l’intégrase. Le projet de cette thèse vise à mieux comprendre le fonctionnement de cette enzyme notamment en identifiant des facteurs cellulaires interagissant avec celle-ci, facteurs qui pourraient être des agents favorisant le processus intégratif ou, au contraire, des agents restrictifs. Les intégrases de deux modèles de rétrovirus ont été utilisées dans cette étude : L’intégrase de RAV1, un rétrovirus exogène aviaire du genre des alpharétrovirus appartenant au sous-groupe A de la famille des ASLV. Cette enzyme virale est largement étudiée soit au niveau structural ou fonctionnel, mais les données concernant ses partenaires cellulaires sont rares et insuffisantes. La seconde intégrase est celle du PERV A/C, un rétrovirus endogène porcin du genre gammarétrovirus. Aucune information sur cette enzyme n’a été décrite jusqu’à présent. Ces deux enzymes, en fusion avec une étiquette 6xHistidine, ont été donc produites en bactérie, et en cellules d’insecte puis purifiées sur colonne d’affinité en FPLC. Leurs activités catalytiques ont été testées in vitro. Ces tests permettent de valoriser la capacité de l’intégrase à exercer principalement les 2 fonctions dont elle est responsable in vivo, le clivage en 3’ et le transfert de brins, et une activité qu’elle exerce exclusivement in vitro, la désintégration. Les protéines pures et actives ont ensuite servies à la vérification de leur interaction avec une protéine cellulaire, Brd2. La technique ‘Far western blot’ a ainsi permis de valider l’interaction entre l’intégrase de PERV et la protéine cellulaire, puis d’identifier les domaines de l’intégrase et de Brd2 impliqués dans cette interaction. A terme, l’identification de ce facteur cellulaire et la validation de son rôle dans le processus intégratif permettront de mieux comprendre ce processus particulier développé par les rétrovirus et pourront conduire au développement d’inhibiteurs dirigés contre cette interaction / A critical step for retroviral replication is the stable integration of the provirus genome into the genome of its host; this integration is realized by a viral enzyme, the integrase. The aim of this work was to better understand the functioning of the integrase, particularly, by identifying host factors that might interact with it, and which could be factors favoring the integration process or, restrictive factors. Therefore, we used two models of retroviral integrases: The integrase of RAV1, an alpharetrovirus belonging to the subgroup A of the family of ALSV. Although this viral enzyme is widely studied, still not enough data are available about its cellular cofactors. The second enzyme studied here is the integrase of PERV, a gammaretrovirus. No studies of either PERV integrase activities in vitro or of proteins interacting with this viral enzyme have been available until now. In the present study, we have expressed the PERV and ALSV integrases as fusion proteins with a 6xHistidine Tag in both Escherichia coli and insect SF9 cells. After that, we analysed their ability to mediate catalytic activities (3’-end processing, strand transfer and disintegration) in vitro. We also investigated the interaction of these two viral enzymes with the cellular protein Brd2, using the Far western blot method. Our results validate Brd2 as a cofactor of PERV integrase and point to the important role of particular domains of the PERV integrase and Brd2 in mediating the interaction. Finally, this study contibute to a better understanding of the precise interaction between cellular proteins and integrase, and may lead in the future to the development of protein-protein interaction inhibitors