References of "Kettmann, Richard"
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See detailHomologies entre les deux retrovirus BLV et HTLV-1 et developpement d'une nouvelle approche therapeutique basee sur la levee de la latence virale.
Gillet, Nicolas ULg; Kettmann, Richard ULg; Willems, Luc ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2007), 11(2),

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See detailLes chémokines et leurs récepteurs : rôle dans les infections virales et dans les pathologies cancéreuses
Burteau, C.; Willems, Luc ULg; Kettmann, Richard ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2007)

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See detailHuman T-cell leukemia virus type-1 Tax oncoprotein regulates G-protein signaling.
Twizere, Jean-Claude ULg; Springael, Jean-Yves; Boxus, Mathieu ULg et al

in Blood (2007), 109(3), 1051-60

Human T-cell leukemia virus type-1 (HTLV-1) is associated with adult T-cell leukemia (ATL) and neurological syndromes. HTLV-1 encodes the oncoprotein Tax-1, which modulates viral and cellular gene ... [more ▼]

Human T-cell leukemia virus type-1 (HTLV-1) is associated with adult T-cell leukemia (ATL) and neurological syndromes. HTLV-1 encodes the oncoprotein Tax-1, which modulates viral and cellular gene expression leading to T-cell transformation. Guanine nucleotide-binding proteins (G proteins) and G protein-coupled receptors (GPCRs) constitute the largest family of membrane proteins known and are involved in the regulation of most biological functions. Here, we report an interaction between HTLV-1 Tax oncoprotein and the G-protein beta subunit. Interestingly, though the G-protein beta subunit inhibits Tax-mediated viral transcription, Tax-1 perturbs G-protein beta subcellular localization. Functional evidence for these observations was obtained using conditional Tax-1-expressing transformed T-lymphocytes, where Tax expression correlated with activation of the SDF-1/CXCR4 axis. Our data indicated that HTLV-1 developed a strategy based on the activation of the SDF-1/CXCR4 axis in the infected cell; this could have tremendous implications for new therapeutic strategies. [less ▲]

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See detailClass IIa histone deacetylases: regulating the regulators.
Martin, Maud ULg; Kettmann, Richard ULg; Dequiedt, Franck ULg

in Oncogene (2007), 26(37),

n the last decade, the identification of enzymes that regulate acetylation of histones and nonhistone proteins has revealed the key role of dynamic acetylation and deacetylation in various cellular ... [more ▼]

n the last decade, the identification of enzymes that regulate acetylation of histones and nonhistone proteins has revealed the key role of dynamic acetylation and deacetylation in various cellular processes. Mammalian histone deacetylases (HDACs), which catalyse the removal of acetyl groups from lysine residues, are grouped into three classes, on the basis of similarity to yeast counterparts. An abundance of experimental evidence has established class IIa HDACs as crucial transcriptional regulators of various developmental and differentiation processes. In the past 5 years, a tremendous effort has been dedicated to characterizing the regulation of these enzymes. In this review, we summarize the latest discoveries in the field and discuss the molecular and structural determinants of class IIa HDACs regulation. Finally, we emphasize that comprehension of the mechanisms underlying class IIa HDAC functions is essential for potential therapeutic applications. [less ▲]

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See detailPeripheral blood B-cell death compensates for excessive proliferation in lymphoid tissues and maintains homeostasis in bovine leukemia virus-infected sheep.
Debacq, Christophe; Gillet, Nicolas ULg; Asquith, Becca et al

in Journal of Virology (2006), 80(19), 9710-9719

The size of a lymphocyte population is primarily determined by a dynamic equilibrium between cell proliferation and death. Hence, lymphocyte recirculation between the peripheral blood and lymphoid tissues ... [more ▼]

The size of a lymphocyte population is primarily determined by a dynamic equilibrium between cell proliferation and death. Hence, lymphocyte recirculation between the peripheral blood and lymphoid tissues is a key determinant in the maintenance of cell homeostasis. Insights into these mechanisms can be gathered from large-animal models, where lymphatic cannulation from individual lymph nodes is possible. In this study, we assessed in vivo lymphocyte trafficking in bovine leukemia virus (BLV)-infected sheep. With a carboxyfluorescein diacetate succinimidyl ester labeling technique, we demonstrate that the dynamics of lymphocyte recirculation is unaltered but that accelerated proliferation in the lymphoid tissues is compensated for by increased death in the peripheral blood cell population. Lymphocyte homeostasis is thus maintained by biphasic kinetics in two distinct tissues, emphasizing a very dynamic process during BLV infection. [less ▲]

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See detailSpleen-dependent turnover of CD11b peripheral blood B lymphocytes in bovine leukemia virus-infected sheep.
Florins, Arnaud-Francois ULg; Gillet, Nicolas ULg; Asquith, Becca et al

in Journal of virology (2006), 80(24), 11998-2008

Lymphocyte homeostasis is determined by a critical balance between cell proliferation and death, an equilibrium which is deregulated in bovine leukemia virus (BLV)-infected sheep. We have previously shown ... [more ▼]

Lymphocyte homeostasis is determined by a critical balance between cell proliferation and death, an equilibrium which is deregulated in bovine leukemia virus (BLV)-infected sheep. We have previously shown that an excess of proliferation occurs in lymphoid tissues and that the peripheral blood population is prone to increased cell death. To further understand the mechanisms involved, we evaluated the physiological role of the spleen in this accelerated turnover. To this end, B lymphocytes were labeled in vivo using a fluorescent marker (carboxyfluorescein diacetate succinimidyl ester), and the cell kinetic parameters (proliferation and death rates) of animals before and after splenectomy were compared. We show that the enhanced cell death observed in BLV-infected sheep is abrogated after splenectomy, revealing a key role of the spleen in B-lymphocyte dynamics. [less ▲]

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See detailNew Role For Hpar-1 Kinases Emk And C-Tak1 In Regulating Localization And Activity Of Class Iia Histone Deacetylases
Dequiedt, Franck ULg; Martin, Maud ULg; Von Blume, Julia et al

in Molecular and Cellular Biology (2006), 26(19), 7086-102

Class IIa histone deacetylases (HDACs) are found both in the cytoplasm and in the nucleus where they repress genes involved in several major developmental programs. In response to specific signals, the ... [more ▼]

Class IIa histone deacetylases (HDACs) are found both in the cytoplasm and in the nucleus where they repress genes involved in several major developmental programs. In response to specific signals, the repressive activity of class IIa HDACs is neutralized through their phosphorylation on multiple N-terminal serine residues and 14-3-3-mediated nuclear exclusion. Here, we demonstrate that class IIa HDACs are subjected to signal-independent nuclear export that relies on their constitutive phosphorylation. We identify EMK and C-TAK1, two members of the microtubule affinity-regulating kinase (MARK)/Par-1 family, as regulators of this process. We further show that EMK and C-TAK1 phosphorylate class IIa HDACs on one of their multiple 14-3-3 binding sites and alter their subcellular localization and repressive function. Using HDAC7 as a paradigm, we extend these findings by demonstrating that signal-independent phosphorylation of the most N-terminal serine residue by the MARK/Par-1 kinases, i.e., Ser155, is a prerequisite for the phosphorylation of the nearby 14-3-3 site, Ser181. We propose that this multisite hierarchical phosphorylation by a variety of kinases allows for sophisticated regulation of class IIa HDACs function. [less ▲]

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See detailThe homeobox protein MSX2 interacts with tax oncoproteins and represses their transactivation activity.
Twizere, Jean-Claude ULg; Lefebvre, Laurent; Collete, Delphine et al

in Journal of Biological Chemistry (2005), 280(33), 29804-11

Bovine leukemia virus (BLV) tax is an essential gene involved in the transcriptional activation of viral expression. Tax is also believed to be implicated in leukemogenesis because of its ability to ... [more ▼]

Bovine leukemia virus (BLV) tax is an essential gene involved in the transcriptional activation of viral expression. Tax is also believed to be implicated in leukemogenesis because of its ability to immortalize primary cells in vitro. To gain insight into the molecular pathways mediating the activities of this important gene, we identified cellular proteins interacting with Tax. By means of a two-hybrid approach, we show that Tax specifically interacts with MSX2, a general repressor of gene expression. GST pull-down experiments and co-immunoprecipitation assays further confirmed binding specificity. Furthermore, the N-terminal residues 1-79 of MSX2 are required for binding, whereas the C-terminal residues 201-267 of MSX2 do not play a critical role. Whereas the oncogenic potential of Tax in primary cells was only slightly affected by overexpression of MSX2, the other function of Tax, namely LTR-dependent transcriptional activation, was inhibited by MSX2 in human HeLa and bovine B-lymphoblastoid (BL3) cell lines. This MSX2 repression function can be counteracted by overexpression of transcription factors CREB2 and RAP74. The Tax/MSX2 interplay thus results in repression of viral transcriptional activation possibly acting as a regulatory feedback loop. Importantly, this viral gene silencing is not strictly associated with a concomitant loss of Tax oncogenicity as measured by its ability to immortalize primary cells. And interestingly, MSX2 also interacts with and inhibits the transactivation function of the related Tax1 protein encoded by the Human T-cell leukemia virus type 1 (HTLV-1). [less ▲]

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See detailValproate activates bovine leukemia virus gene expression, triggers apoptosis, and induces leukemia/lymphoma regression in vivo.
Achachi, Amine; Florins, Arnaud-Francois ULg; Gillet, Nicolas ULg et al

in Proceedings of the National Academy of Sciences of the United States of America (2005), 102(29), 10309-14

Leukemogenic viruses like human T-lymphotropic virus and bovine leukemia virus (BLV) presumably persist in the host partly by latent integration of the provirus in a fraction of infected cells, leading to ... [more ▼]

Leukemogenic viruses like human T-lymphotropic virus and bovine leukemia virus (BLV) presumably persist in the host partly by latent integration of the provirus in a fraction of infected cells, leading to accumulative increase in the outgrowth of transformed cells. Furthermore, viral infection also correlates with a blockade of the apoptotic mechanisms concomitant with an apparent latency of the host cell. Conceptually, induction of viral or cellular gene expression could thus also be used as a therapeutic strategy against retroviral-associated leukemia. Here, we provide evidence that valproate, an inhibitor of deacetylases, activates BLV gene expression in transient transfection experiments and in short-term cultures of primary B-lymphocytes. In vivo, valproate injection into newly BLV-inoculated sheep did not abrogate primary infection. However, valproate treatment, in the absence of any other cytotoxic drug, was efficient for leukemia/lymphoma therapy in the sheep model leading to decreased lymphocyte numbers (respectively from 25.6, 35.7, and 46.5 x 10(3) cells per mm3 to 1.0, 10.6, and 24.3 x 10(3) cells per mm3 in three leukemic sheep) and tumor regression (from >700 cm3 to undetectable). The concept of a therapy that targets the expression of viral and cellular genes might be a promising treatment of adult T cell leukemia or tropical spastic paraparesis/human T-lymphotropic virus-associated myelopathy, diseases for which no satisfactory treatment exists so far. [less ▲]

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See detailPhosphorylation Of Histone Deacetylase 7 By Protein Kinase D Mediates T Cell Receptor-Induced Nur77 Expression And Apoptosis
Dequiedt, Franck ULg; Van Lint, J.; Lecomte, E. et al

in Journal of Experimental Medicine (2005), 201(5),

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See detailReduced cell turnover in lymphocytic monkeys infected by human T-lymphotropic virus type 1.
Debacq, Christophe; Heraud, Jean-Michel; Asquith, Becca et al

in Oncogene (2005), 24(51), 7514-23

Understanding cell dynamics in animal models have implications for therapeutic strategies elaborated against leukemia in human. Quantification of the cell turnover in closely related primate systems is ... [more ▼]

Understanding cell dynamics in animal models have implications for therapeutic strategies elaborated against leukemia in human. Quantification of the cell turnover in closely related primate systems is particularly important for rare and aggressive forms of human cancers, such as adult T-cell leukemia. For this purpose, we have measured the death and proliferation rates of the CD4+ T lymphocyte population in squirrel monkeys (Saimiri sciureus) infected by human T-lymphotropic virus type 1 (HTLV-1). The kinetics of in vivo bromodeoxyuridine labeling revealed no modulation of the cell turnover in HTLV-1-infected monkeys with normal CD4 cell counts. In contrast, a substantial decrease in the proliferation rate of the CD4+ T population was observed in lymphocytic monkeys (e.g. characterized by excessive proportions of CD4+ T lymphocytes and by the presence of abnormal flower-like cells). Unexpectedly, onset of HTLV-associated leukemia thus occurs in the absence of increased CD4+ T-cell proliferation. This dynamics significantly differs from the generalized activation of the T-cell turnover induced by other primate lymphotropic viruses like HIV and SIV. [less ▲]

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See detailBovine leukaemia as an experimental model of viral T-cell leukaemia in humans.
Russev, R.; Shikova, E.; Dimitrov, P. et al

in Cyprus Journal of Sciences (2005), 3

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See detailMapk Pathway Contributes To Density- And Hypoxia-Induced Expression Of The Tumor-Associated Carbonic Anhydrase Ix
Kopacek, J.; Barathova, M.; Dequiedt, Franck ULg et al

in Biochimica et Biophysica Acta-Gene Structure and Expression (2005), 1729(1),

Transcription of the CA9 gene coding for a tumor-associated carbonic anhydrase IX (CA IX) isoform is regulated by hypoxia via the hypoxia-inducible factor 1 (HIF-1) and by high cell density via the ... [more ▼]

Transcription of the CA9 gene coding for a tumor-associated carbonic anhydrase IX (CA IX) isoform is regulated by hypoxia via the hypoxia-inducible factor 1 (HIF-1) and by high cell density via the phosphatidylinositol-3-kinase (PI3K) pathway. We examined the role of the mitogen-activated protein kinase (MAPK) pathway in the control of CA9 gene expression. Inhibition of MAPK signaling by U0126 in HeLa cells led to reduced activity of the PR1-HRE-luc CA9 promoter construct and decreased CA IX protein levels in dense culture as well as in hypoxia. Similar reduction was obtained by expression of a dominant-negative ERK1 mutant and was also observed in U0126-treated HIF-1alpha-deficient Ka13 cells. Simultaneous treatment with the MAPK and PI3K inhibitors U0126 and LY 294002 had stronger effect than individual inhibition of these pathways. Taken together, our results suggest that besides the PI3K pathway, the MAPK cascade is involved in the regulation of CA9 gene expression under both hypoxia and high cell density. [less ▲]

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See detailInvolvement of glutathione as a mechanism of indirect protection against spontaneous ex vivo apoptosis associated with bovine leukemia virus.
Sanchez Alcaraz, Teresa; Kerkhofs, Pierre; Reichert, Michal et al

in Journal of virology (2004), 78(12),

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See detailReduced proviral loads during primo-infection of sheep by Bovine Leukemia virus attenuated mutants.
Debacq, Christophe; Sanchez Alcaraz, Maria Teresa; Mortreux, Franck et al

in Retrovirology (2004), 1(1),

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See detailInteraction of retroviral Tax oncoproteins with tristetraprolin and regulation of tumor necrosis factor-alpha expression.
Twizere, Jean-Claude ULg; Kruys, Veronique; Lefebvre, Laurent et al

in Journal of the National Cancer Institute (2003), 95(24), 1846-59

BACKGROUND: The Tax oncoproteins are transcriptional regulators of viral expression involved in pathogenesis induced by complex leukemogenic retroviruses (or delta-retroviruses, i.e., primate T-cell ... [more ▼]

BACKGROUND: The Tax oncoproteins are transcriptional regulators of viral expression involved in pathogenesis induced by complex leukemogenic retroviruses (or delta-retroviruses, i.e., primate T-cell leukemia viruses and bovine leukemia virus). To better understand the molecular pathways leading to cell transformation, we aimed to identify cellular proteins interacting with Tax. METHODS: We used a yeast two-hybrid system to identify interacting cellular proteins. Interactions between Tax and candidate interacting cellular proteins were confirmed by glutathione S-transferase (GST) pulldown assays, co-immunoprecipitation, and confocal microscopy. Functional interactions between Tax and one interacting protein, tristetraprolin (TTP), were assessed by analyzing the expression of tumor necrosis factor-alpha (TNF-alpha), which is regulated by TTP, in mammalian cells (HeLa, D17, HEK 293, and RAW 264.7) transiently transfected with combinations of intact and mutant Tax and TTP. RESULTS: We obtained seven interacting cellular proteins, of which one, TTP, was further characterized. Tax and TTP were found to interact specifically through their respective carboxyl-terminal domains. The proteins colocalized in the cytoplasm in a region surrounding the nucleus of HeLa cells. Furthermore, coexpression of Tax was associated with nuclear accumulation of TTP. TTP is an immediate-early protein that inhibits expression of TNF-alpha at the post-transcriptional level. Expression of Tax reverted this inhibition, both in transient transfection experiments and in stably transfected macrophage cell lines. CONCLUSION: Tax, through its interactions with the TTP repressor, indirectly increases TNF-alpha expression. This observation is of importance for the cell transformation process induced by leukemogenic retroviruses, because TNF-alpha overexpression plays a central role in pathogenesis. [less ▲]

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See detailReduced Cell Turnover In Bovine Leukemia Virus-Infected, Persistently Lymphocytotic Cattle
Debacq, C.; Asquith, B.; Reichert, M. et al

in Journal of Virology (2003), 77(24),

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See detailIncreased cell proliferation-but not reduced cell death-induces lymphocytosis in Bovine Leukaemia Virus-infected sheep
Debacq, Christophe; Asquith, B.; Kerkhofs, Pierre et al

in Abstracts of papers presented at the 2002 meeting of retroviruses (2002, May)

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See detailInteracting surface of the receptor-binding domain.
Gatot, Jean-Stéphane; Callebaut, Isabelle; Van Lint, Carine et al

in Société Belge de Biochimie et de Biologie moléculaire. (2002, February 22)

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