References of "Rambout, Xavier"
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See detailConstruction of an interactomic map of Ets factors and identification of new functions in mRNA processing
Rambout, Xavier ULg

Doctoral thesis (2013)

The family of Ets factors is one of the largest families of human transcription factors. This thesis aimed at molecularly and biologically defining these well known though not well-understood ... [more ▼]

The family of Ets factors is one of the largest families of human transcription factors. This thesis aimed at molecularly and biologically defining these well known though not well-understood transcription factors using a system biology approach. Combination of interactomic and bioinformatics tools gave rise to the first interactome of the human Ets factors built on more than 400 interactions with nearly 300 interaction partners. We fragmented our interactome in 24 functional highly intraconnected sub-networks (clusters, or CL) and highlighted a new role for Ets transcription factors in mRNA processing (CL1). Steady-state levels of mRNAs result from the balance between transcription and mRNA decay, two events sitting at both ends of the mRNA life. In the traditional and still prominent view, these events are spatially, functionally and temporally independent. Here, we showed that the Erg subfamily of Ets factors (composed of the three members ERG, FLI1, and FEV) regulate mRNA decay of specific targets via promoter-mediated mRNA imprinting with sequence-specific RNA-binding proteins (CL1) and the CCR4-NOT deadenylation complex. This constitutes the first evidence, regardless of the organism, that DNA-binding transcription factors recruit RNA-binding proteins and mRNA decay components to control the degradation of specific mRNAs. This is also the most detailed demonstration of a functional coupling between transcription and mRNA decay machineries in humans. We showed that ERG promoted mRNA decay of key mitotic regulators, among which the Aurora kinases Aurora A and B. Depletion of ERG prevented degradation of Aurora A and B mRNAs during mitosis, leading to aberrant levels of Aurora proteins, accumulation of centrosome and mitotic spindle defects, and ultimately mitosis blockage. This consists in a significant advance in understanding of mitosis progression that was until now thought to be exclusively regulated by post-translational modifications and proteasomal degradation of proteins. Our results show that, in the contrary of bulk mRNAs whose decay is inhibited during mitosis, degradation of specific transcripts is a prerequisite for normal mitosis progression. [less ▲]

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See detailAn interaction map for HTLV-1 Tax and PDZ-containing proteins.
Blibek, Karim ULg; Rambout, Xavier ULg; beaufays, Jérôme et al

Poster (2013, June 29)

Human T-cell leukemia virus type 1 (HTLV-1) retrovirus encodes for the Tax protein, which has a transforming capacity in vitro. Tax contains at its C-terminus a binding motif for PDZ domain-containing ... [more ▼]

Human T-cell leukemia virus type 1 (HTLV-1) retrovirus encodes for the Tax protein, which has a transforming capacity in vitro. Tax contains at its C-terminus a binding motif for PDZ domain-containing proteins (PSD95-DLG1-ZO1). It has been shown that the C-terminal motif of Tax is involved in Tax oncogenic capacity. Ten different PDZ domain-containing proteins have been reported to interact with Tax, but the specificity of Tax-human PDZome interactions has not been investigated. The objective of this study is to obtain a comprehensive interactome map for Tax and the human PDZome and to determine a global role of Tax-PDZ interactions in HTLV-1 biology. [less ▲]

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See detailInteractomic map of the Ets factors family : Identification of unexpected functions in mRNA processing
Rambout, Xavier ULg; Simonis, Nicolas; Brohée, Sylvain et al

Poster (2013, January 28)

The Ets factors are a family of 27 transcription factors characterized by their unique DNA-binding domain. We aimed at building a protein-protein interaction (PPI) map (interactome) of the human Ets ... [more ▼]

The Ets factors are a family of 27 transcription factors characterized by their unique DNA-binding domain. We aimed at building a protein-protein interaction (PPI) map (interactome) of the human Ets factors in order to better define their roles and regulations in normal and oncogenic processes. The Ets interactome was built on a high-throughput yeast-two hybrid (Y2H) approach, and a literature and database curation. We identified 431 PPIs and 276 different protein partners. Clustering of the Ets interactome divided it into 24 functional subnetworks classified on their novelty index and their size. Cluster#1 was exclusively composed of newly identified interaction partners and was highly connected to the Erg subfamily of Ets factors. Gene ontology enrichment analysis revealed that it was associated to mRNA processing. In support of this result, we observed in HeLa cells that ERG and the components of cluster#1 localized in p-bodies and stress granules, physically linked cytoplasmic sites of mRNA degradation and silencing. Hence, we hypothesized that Erg proteins might have a role in post-transcriptional gene regulation and be involved in cellular mRNAs degradation. To test this hypothesis, we performed a MS2-based tethering assay and showed that the recruitment of ERG on a mRNA reporter promoted inhibition of its expression via a two-fold decrease of its half-life. ERG controls degradation of target mRNAs via different mechanisms including polysome stability, mRNA deadenylation, and p-bodies aggregation. A microarray-based appraoch identified 321 endogeneous genes whose mRNA decay rate was lowered in ERG silenced cells. Results point out the Nter domain of ERG as the predominant domain required for mRNA degradation. Importantly, oncogenic TET-Erg fusions described in AML and Ewing’s sarcoma exhibited diminished ability to degrade target mRNAs, concomitantly with the loss of the ERG Nter domain. This reinforces the important role of Erg proteins in mRNA degradation in cancer. [less ▲]

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See detailInteractomic map of the Ets factors family : Identification of unexpected functions in mRNA processing
Rambout, Xavier ULg; Simonis, Nicolas; Demoitié, Pauline et al

in Keystone symposium - Protein-RNA Interactions in Biology and Disease (C1) (2012, March 05)

The Ets factors are a family of 27 transcription factors characterized by their unique DNA-binding domain, the ETS domain. We aimed at building a protein-protein interaction (PPI) map (interactome) of the ... [more ▼]

The Ets factors are a family of 27 transcription factors characterized by their unique DNA-binding domain, the ETS domain. We aimed at building a protein-protein interaction (PPI) map (interactome) of the human Ets factors in order to better define their roles and regulations in normal and oncogenic processes. The Ets interactome was built on a high-throughput yeast-two hybrid (Y2H) approach, and a literature and database curation of confident interactions which led us to the identification of 602 PPIs and 369 different protein partners. Clusterization using the Network Analysis Tool box (NeAT) divided the ETS interactome into 39 functional sub-networks. Among these, we identified Cluster16 as highly connected to the Erg ETS subfamily. A gene ontology (GO) enrichment analysis revealed that Cluster16 was associated to various aspects of mRNA processing. We therefore hypothesized that Erg factors might have a role in post-transcriptional gene regulation. This would constitute a entirely new and undisclosed role for ETS factors, which are so far firmly established as transcription factors. In support of our hypothesis, we observed that ERG localized in p-bodies, cytoplasmic sites of mRNA decay. Interestingly, under various cellular stresses, a portion of ERG and its partners from Cluster16 localized in stress granules, cytoplasmic sites of mRNA silencing physically linked to p-bodies. Hence, we hypothesized that Erg proteins might be involved in cellular mRNAs degradation. To test this, we performed a MS2-based tethering assay and showed that the recruit-ment of Erg factors promoted degradation of a reporter mRNA, mainly via its N-ter domain. Very importantly, oncogenic TET-Erg fusions described in AML and Ewing’s sarcoma exhibited diminished ability to degrade target mRNAs, concomitantly with the loss of the N-ter domain of the corresponding Erg protein. This re-inforces the important role of Erg proteins in mRNA degradation in cancer. Our efforts are now concentrated on identifying the molecular determinants behind this new function of Erg proteins. [less ▲]

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See detailThe inositol phosphatase SHIP-1 inhibits NOD2-induced NF-κB activation by disturbing the interaction of XIAP with RIP2
Condé, Claude ULg; Rambout, Xavier ULg; Lebrun, Marielle ULg et al

in PLoS ONE (2012)

SHIP-1 is an inositol phosphatase predominantly expressed in hematopoietic cells. Over the ten past years, SHIP-1 has been described as an important regulator of immune functions. Here, we characterize a ... [more ▼]

SHIP-1 is an inositol phosphatase predominantly expressed in hematopoietic cells. Over the ten past years, SHIP-1 has been described as an important regulator of immune functions. Here, we characterize a new inhibitory function for SHIP-1 in NOD2 signaling. NOD2 is a crucial cytoplasmic bacterial sensor that activates proinflammatory and antimicrobial responses upon bacterial invasion. We observed that SHIP-1 decreases NOD2-induced NF-κB activation in macrophages. This negative regulation relies on its interaction with XIAP. Indeed, we observed that XIAP is an essential mediator of the NOD2 signaling pathway that enables proper NF-κB activation in macrophages. Upon NOD2 activation, SHIP-1 C-terminal proline rich domain (PRD) interacts with XIAP, thereby disturbing the interaction between XIAP and RIP2 in order to decrease NF-κB signaling. [less ▲]

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See detailEstablishment of an interactomic map of the Ets factors family: Towards a better understanding of their roles in oncogenic processes
Rambout, Xavier ULg; Simonis, Nicolas; Demoitié, Pauline et al

Poster (2011, April 29)

Ets transcription factors have been involved in several cancers such as leukemia, prostate cancer and Ewing’s sarcoma. They regulate the expression of genes controlling important biological processes such ... [more ▼]

Ets transcription factors have been involved in several cancers such as leukemia, prostate cancer and Ewing’s sarcoma. They regulate the expression of genes controlling important biological processes such as cellular proliferation, differentiation, apoptosis, metastasis, and transformation. This family of transcription factors is characterized by its highly conserved DNA-binding domain called the ETS domain and members are classified into subfamilies based on sequence homology criterion. We built a protein-protein interaction (PPI) network of the 27 Ets proteins and of their individual functional domains using a high-throughput yeast-two hybrid (Y2H) screening method. That Y2H network was expanded with confident literature-curated PPIs to obtain a comprehensive Ets interaction network. By considering connectivity between Ets interaction partners, we were able to segregate highly connected clusters of proteins from that network. Analysis of ontologies enrichment of those clusters enabled to confirm well-established roles and regulations of Ets factors, but also to suggest new ones. Biological validation of one precise cluster could be used as a rule of a thumb to globally confirm the bioinformatic analysis of our Ets PPI network and the potential physiological or pathological roles and regulation of Ets factors. [less ▲]

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See detailEstablishment of an interactomic map of the Ets factors family: Towards a better understanding of their roles in oncogenic processes
Rambout, Xavier ULg; Twizere, Jean-Claude ULg; Dequiedt, Franck ULg

in Inserm Workshop: Interactomics: at the crossroads of biology and bioinformatics (2010, March)

Ets transcription factors play key roles in several cancers such as leukemia, prostate cancer and Ewing’s sarcoma. They regulate the expression of genes controlling biological processes such as cellular ... [more ▼]

Ets transcription factors play key roles in several cancers such as leukemia, prostate cancer and Ewing’s sarcoma. They regulate the expression of genes controlling biological processes such as cellular proliferation, differentiation, apoptosis, metastasis, and transformation. This family is characterized by a highly conserved DNA-binding domain (ETS domain) and is classified into subfamilies according to sequence homology between the members. Using a high-throughput yeast two-hybrid (Y2H) method, we tested the interaction of the major splicing variants of the 28 human Ets factors and their functional domains of interest against the last available version of the human ORFeome (hORFeome v5.1). This screen has identified more than 200 new partners of Ets proteins. Further validation of these new interactions together with previously described interactions will enable a global evaluation of the regulation, and normal and cancerous roles of Ets factors. [less ▲]

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See detailNOD2 interactome
Lecat, Aurore ULg; Di Valentin, Emmanuel ULg; Fillet, Marianne ULg et al

Poster (2010, January 28)

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See detailInvestigating Prostaglandin E2 activation of the p38 pathway of oesophageal squamous cell carcinoma
Rambout, Xavier ULg

Master's dissertation (2008)

Background, aim and objectives: Oesophageal squamous cell carcinoma (OSCC) is an endemic disease. Epidemiologic studies driven by investigation of Sammon in a region with one of the highest prevalence ... [more ▼]

Background, aim and objectives: Oesophageal squamous cell carcinoma (OSCC) is an endemic disease. Epidemiologic studies driven by investigation of Sammon in a region with one of the highest prevalence, linked a predisposition to develop OSCC to a high consumption of maize via reflux disease and chronic oesophagitis. In that context, it was postulated that prostaglandin E2 (PGE2), a hormone derived from a main component of maize, continuously triggers activation of proliferation and inflammation pathways. This work aimed at assessing the role of p38, a mitogen-activated protein kinase (MAPK), in the potential of PGE2 to trigger cellular proliferation, transcription and expression of proliferative (Cyclin D1) and inflammatory (IL-6) mediators in a human epithelial oesophageal cell line (Het1a). Methods: The proliferation potential of PGE2 via p38 was assessed by MTT assay on Het1a. The effect of H2O2 treatments was also assessed as a positive control. Then, RNA and protein samples were extracted from that cell line previously PGE2-treated. Transcription and expression profiles were studied over time respectively by quantitative polymerase chain reaction (qPCR) and western blot. The role of p38 was assessed by addition of a specific inhibitor, SB203580, to the cells under investigation. Results and Discussion: It was shown that PGE2 alone could not trigger proliferation of the Het1a cell line. Though, the effect of p38 might be positive. Acute H2O2 treatments turned out encouraging in the development of a model of p38 activation. Regulation of Cyclin D1 and IL-6 transcription was suggested to occur through PGE2 and via the p38 pathway. The Cyclin D1 and IL-6 transcripts were respectively overexpressed and downregulated in a bimodal manner, the second peak relying exclusively on p38 activation. Both observations could be supported by a positive feedback theory involving cyclooxygenase (COX)-2. Conclusions: Even though PGE2 was shown not to be sufficient to promote Het1a proliferation, regulation of Cyclin D1 and IL-6 transcription via p38 was observed. Furthermore, the expression profile might support the Sammon-Pink theory. [less ▲]

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