Role of Varicella Zoster virus ORF9p in the secondary egress : importance of its interaction with the cellular Adaptin Protein-1.
Lebrun, Marielle ; ; et al
Poster (2016, May 20)Detailed reference viewed: 51 (7 ULg)
The transcription factor ERG recruits CCR4-NOT to control mRNA decay and mitotic progression.
Rambout, Xavier ; ; et al
in Nature Structural & Molecular Biology (2016)
Control of mRNA levels, a fundamental aspect in the regulation of gene expression, is achieved through a balance between mRNA synthesis and decay. E26-related gene (Erg) proteins are canonical ... [more ▼]
Control of mRNA levels, a fundamental aspect in the regulation of gene expression, is achieved through a balance between mRNA synthesis and decay. E26-related gene (Erg) proteins are canonical transcription factors whose previously described functions are confined to the control of mRNA synthesis. Here, we report that ERG also regulates gene expression by affecting mRNA stability and identify the molecular mechanisms underlying this function in human cells. ERG is recruited to mRNAs via interaction with the RNA-binding protein RBPMS, and it promotes mRNA decay by binding CNOT2, a component of the CCR4-NOT deadenylation complex. Transcriptome-wide mRNA stability analysis revealed that ERG controls the degradation of a subset of mRNAs highly connected to Aurora signaling, whose decay during S phase is necessary for mitotic progression. Our data indicate that control of gene expression by mammalian transcription factors may follow a more complex scheme than previously anticipated, integrating mRNA synthesis and degradation. [less ▲]Detailed reference viewed: 48 (13 ULg)
Systematic interactome mapping of acute lymphoblastic leukemia cancer gene products reveals EXT-1 tumor suppressor as a Notch1 and FBWX7 common interactor.
Daakour, Sarah ; ; et al
in BMC Cancer (2016), 16(1), 335
BACKGROUND: Perturbed genotypes in cancer can now be identified by whole genome sequencing of large number of diverse tumor samples, and observed gene mutations can be used for prognosis and ... [more ▼]
BACKGROUND: Perturbed genotypes in cancer can now be identified by whole genome sequencing of large number of diverse tumor samples, and observed gene mutations can be used for prognosis and classification of cancer subtypes. Although mutations in a few causative genes are directly linked to key signaling pathways perturbation, a global understanding of how known cancer genes drive oncogenesis in human is difficult to assess. METHODS: We collected available information about mutated genes in Acute Lymphoblastic Leukemia (ALL). Validated human protein interactions (PPI) were collected from IntAct, HPRD and BioGRID interactomics databases, or obtained using yeast two-hybrid screening assay. RESULTS: We have mapped interconnections between 116 cancer census gene products associated with ALL. Combining protein-protein interactions data and cancer-specific gene mutations information, we observed that 63 ALL-gene products are interconnected and identified 37 human proteins interacting with at least 2 ALL-gene products. We highlighted exclusive and coexistence genetic alterations in key signaling pathways including the PI3K/AKT and the NOTCH pathways. We then used different cell lines and reporter assay systems to validate the involvement of EXT1 in the Notch pathway. CONCLUSION: We propose that novel ALL-gene candidates can be identified based on their functional association with well-known cancer genes. We identified EXT1, a gene not previously linked to ALL via mutations, as a common interactor of NOTCH1 and FBXW7 regulating the NOTCH pathway in an FBXW7-dependend manner. [less ▲]Detailed reference viewed: 59 (7 ULg)
Apoptosis-induced ectodomain shedding of hypoxia-regulated carbonic anhydrase IX from tumor cells: a double-edged response to chemotherapy.
; Dequiedt, Franck ; et al
in BMC Cancer (2016), 16(1), 239
BACKGROUND: Carbonic anhydrase IX (CA IX) is a tumor-associated, highly active, transmembrane carbonic anhydrase isoform regulated by hypoxia and implicated in pH control and adhesion-migration-invasion ... [more ▼]
BACKGROUND: Carbonic anhydrase IX (CA IX) is a tumor-associated, highly active, transmembrane carbonic anhydrase isoform regulated by hypoxia and implicated in pH control and adhesion-migration-invasion. CA IX ectodomain (ECD) is shed from the tumor cell surface to serum/plasma of patients, where it can signify cancer prognosis. We previously showed that the CA IX ECD release is mediated by disintegrin and metalloproteinase ADAM17. Here we investigated the CA IX ECD shedding in tumor cells undergoing apoptosis in response to cytotoxic drugs, including cycloheximide and doxorubicin. METHODS: Presence of cell surface CA IX was correlated to the extent of apoptosis by flow cytometry in cell lines with natural or ectopic CA IX expression. CA IX ECD level was assessed by ELISA using CA IX-specific monoclonal antibodies. Effect of recombinant CA IX ECD on the activation of molecular pathways was evaluated using the cell-based dual-luciferase reporter assay. RESULTS: We found a significantly lower occurrence of apoptosis in the CA IX-positive cell subpopulation than in the CA IX-negative one. We also demonstrated that the cell-surface CA IX level dropped during the death progress due to an increased ECD shedding, which required a functional ADAM17. Inhibitors of metalloproteinases reduced CA IX ECD shedding, but not apoptosis. The CA IX ECD release induced by cytotoxic drugs was connected to elevated expression of CA IX in the surviving fraction of cells. Moreover, an externally added recombinant CA IX ECD activated a pathway driven by the Nanog transcription factor implicated in epithelial-mesenchymal transition and stemness. CONCLUSIONS: These findings imply that the increased level of the circulating CA IX ECD might be useful as an indicator of an effective antitumor chemotherapy. Conversely, elevated CA IX ECD might generate unwanted effects through autocrine/paracrine signaling potentially contributing to resistance and tumor progression. [less ▲]Detailed reference viewed: 44 (3 ULg)
Study of Developmental and Molecular Processes Regulated by Sorbs1 using a Combination of in vitro and in vivo models Alexandra Veloso1, Anouk Bleuart1, Maud Martin1, Jonathan Bruyr1, Marie-Ange Mavaccarella1, and Franck Dequiedt1
Bacquelaine Veloso, Alexandra ; Dequiedt, Franck
Poster (2015, August 24)
SoHo proteins belong to a family that includes three members: Sorbs1 (Cbl associated protein CAP/ponsin), Sorbs2 (Arg-Binding Protein 2, ArgBP2) and Sorbs3 (Vinexin). These proteins share a similar ... [more ▼]
SoHo proteins belong to a family that includes three members: Sorbs1 (Cbl associated protein CAP/ponsin), Sorbs2 (Arg-Binding Protein 2, ArgBP2) and Sorbs3 (Vinexin). These proteins share a similar structure with a SoHo domain in N-terminal region and three SH3 domains in carboxy terminal region. These characteristic domains bind to several signaling molecules involved in a variety of cytoskeleton-related processes, and SoHo family members are thus thought to function as adaptor proteins. However, the precise role of these proteins in the cytoskeleton regulation and associated biological functions remains unknown. It is well established that cytoskeleton regulation is critical for various developmental events including angiogenesis, the process by which new blood vessels develop from pre-existing ones, and myogenesis, the process responsible for muscle formation and regeneration. The goal of this project is to identify the developmental function of Sorbs1 and characterize the underlying molecular events by exploiting a combination of in vivo (Zebrafish) and in vitro models. Phenotype analysis revealed that Morpholino-mediated knock-down of Sorbs1 induces abnormal development of cardiac, angiogenic and muscles structures. Knock-down zebrafish embryos were unable to form cardiac looping and present a cardiac edema. Also, it was noticed that tail morphology was altered by Sorbs1 knock-down suggesting that Sorbs1 plays a role in trunk muscle formation. Finally, the development of venous angiogenic structures, such as caudal vein plexus (CVP) and subintestinal veins (SIV), was specifically affected by Sorbs1inactivation. Interestingly, Sorbs1 seems to have a specific role in venous angiogenesis (CVP and SIV), since arterial angiogenic structures, such as Intersegmental vessels, were not affected in Sorbs1 morphants. In conclusion, these preliminary results of our work highlighted important developmental defects by consequence of Sorbs1 inactivation in Zebrafish. Some of these defects appear to be regulated by angiogenesis and myogenesis, two developmental processes for which the therapeutic implications are undeniable. [less ▲]Detailed reference viewed: 40 (8 ULg)
Identification of VZV ORF9p potential cellular partners that could be important for the viral egress.
Lebrun, Marielle ; ; Rambout, Xavier et al
Poster (2015, July 26)
ORF9p (homologous to HSV-1 VP22) is a VZV tegument protein essential for the viral replication. During the lytic cycle it is the mostly expressed gene. We have recently demonstrated that it is a substrate ... [more ▼]
ORF9p (homologous to HSV-1 VP22) is a VZV tegument protein essential for the viral replication. During the lytic cycle it is the mostly expressed gene. We have recently demonstrated that it is a substrate of the viral kinase ORF47p and that its ORF47p-dependent phosphorylation is important for the secondary envelopment process. We also have identified an acidic cluster (AC) within the protein that is important for its correct localization in the infected cells and for the interaction with ORF47p. The recombinant VZV expressing ORF9p-ΔAC presents an accumulation of capsids in the perinuclear space. ORF9p seems then to play an important role in several steps of the egress process. In this context, we sought to identify cellular partners of ORF9p that might be important for these functions. We performed a yeast two hybrid screen against the human ORFeome 5.1. and picked out 44 candidates among which 5 proteins playing roles in membrane organization and targeting. We currently are trying to confirm these interactions in infected cells and to assess the role of these interactions for the viral lytic cycle. [less ▲]Detailed reference viewed: 42 (12 ULg)
The class IIa HDACs prevent degradation of RBFOX2 by Chaperone-Mediated Autophagy
Detiffe, Cécile ; Dequiedt, Franck ; Rambout, Xavier
Poster (2015, June)
By modulating the acetylation level of histones, histone deacetylases (HDACs) are enzymes playing a key role in the control of gene expression. In addition to histones, HDACs also have non-histone ... [more ▼]
By modulating the acetylation level of histones, histone deacetylases (HDACs) are enzymes playing a key role in the control of gene expression. In addition to histones, HDACs also have non-histone substrates, which may relate to potential roles for HDACs outside of gene regulation. Because HDACs are key regulators of major cellular processes such as cell division, apoptosis and differentiation, it is not surprising that these enzymes have emerged as attractive therapeutic targets for cancer. While the in vivo antitumoral activities of several small molecules HDACs inhibitors have generated a lot of hope, these molecules often showed dramatic side-effects. It is suspected that these side effects could be related to unknown functions of HDACs. The goal of this project is to identify novel, unsuspected functions of HDACs that will help developing more efficient and specific HDAC-based antitumoral therapies. To identify novel functions of HDACs, we used a high-throughput yeast two hybrid (Y2H) approach. This led to the first comprehensive interactomic map of class IIa HDACs that includes 84 protein partners. Among new HDACs partners, we identified several RNA-binding proteins (RBPs) involved in mRNA processing. In this work, we focused on one, the alternative splicing regulator RBFOX2, and investigated its regulation by class IIa HDACs. Through various approaches, we verified that HDAC7 interacts with RBFOX2. In addition, we found that silencing of HDAC7 correlates with a decrease in stability of RBFOX2. Because we identified a potential CMA-specific KFERQ motif in RBFOX2, we tested the possibility that RBFOX2 might be degraded through Chaperone-Mediated Autophagy (CMA). Supporting this hypothesis, we found that RBFOX2 interacts with the co-chaperone HSC70. RBFOX2 levels are sensitive to CMA inducers, including serum starvation and 6AN. Interestingly, we found that a lysine residue in the KFERQ motif of RBFOX2 is acetylated, suggesting that HDAC7 might control RBFOX2 degradation through reversible acetylation. Indeed, degradation of RBFOX2 following HDAC7 silencing was reverted with an inhibitor of autophagy, bafilomycin A1. Analysis of RNA splicing pattern in cells depleted for HDAC7 showed that absence of HDAC7 is associated with 159 alternative splicing events. These events mostly include exon skipping that is known to be the major splicing event in which RBFOX2 is involved. In addition, we observed a highly statistically overlap between splicing events associated with RBFOX2 and HDAC7 depletion. [less ▲]Detailed reference viewed: 68 (5 ULg)
Sulforaphane reduces molecular response to hypoxia in ovarian tumor cells independently of their resistance to chemotherapy.
; ; et al
in International Journal of Oncology (2015), 47(1), 51-60
One of the recently emerging anticancer strategies is the use of natural dietary compounds, such as sulforaphane, a cancer-chemopreventive isothiocyanate found in broccoli. Based on the growing evidence ... [more ▼]
One of the recently emerging anticancer strategies is the use of natural dietary compounds, such as sulforaphane, a cancer-chemopreventive isothiocyanate found in broccoli. Based on the growing evidence, sulforaphane acts through molecular mechanisms that interfere with multiple oncogenic pathways in diverse tumor cell types. Herein, we investigated the anticancer effects of bioavailable concentrations of sulforaphane in ovarian carcinoma cell line A2780 and its two derivatives, adriamycin-resistant A2780/ADR and cisplatin-resistant A2780/CP cell lines. Since tumor microenvironment is characterized by reduced oxygenation that induces aggressive tumor phenotype (such as increased invasiveness and resistance to chemotherapy), we evaluated the effects of sulforaphane in ovarian cancer cells exposed to hypoxia (2% O2). Using the cell-based reporter assay, we identified several oncogenic pathways modulated by sulforaphane in hypoxia by activating anticancer responses (p53, ARE, IRF-1, Pax-6 and XRE) and suppressing responses supporting tumor progression (AP-1 and HIF-1). We further showed that sulforaphane decreases the level of HIF-1alpha protein without affecting its transcription and stability. It can also diminish transcription and protein level of the HIF-1 target, CA IX, which protects tumor cells from hypoxia-induced pH imbalance and facilitates their migration/invasion. Accordingly, sulforaphane treatment leads to diminished pH regulation and reduced migration of ovarian carcinoma cells. These effects occur in all three ovarian cell lines suggesting that sulforaphane can overcome the chemoresistance of cancer cells. This offers a path potentially exploitable in sensitizing resistant cancer cells to therapy, and opens a window for the combined treatments of sulforaphane either with conventional chemotherapy, natural compounds, or with other small molecules. [less ▲]Detailed reference viewed: 10 (2 ULg)
Myeloperoxidase Oxidized LDL Interferes with Endothelial Cell Motility through miR-22 and Heme Oxygenase 1 Induction: Possible Involvement in Reendothelialization of Vascular Injuries
; ; et al
in Mediators of Inflammation (2014)Detailed reference viewed: 14 (1 ULg)
DUSP3/VHR is a pro-angiogenic atypical dual-specificity phosphatase
Amand, Mathieu ; Erpicum, Charlotte ; BAJOU, Khalid et al
Poster (2014, January 27)Detailed reference viewed: 63 (24 ULg)
DUSP3/VHR is a pro-angiogenic atypical dual-specificity phosphatase
Amand, Mathieu ; Erpicum, Charlotte ; BAJOU, Khalid et al
in Molecular Cancer (2014)
Background DUSP3 phosphatase, also known as Vaccinia-H1 Related (VHR) phosphatase, encoded by DUSP3/Dusp3 gene, is a relatively small member of the dual-specificity protein phosphatases. In vitro studies ... [more ▼]
Background DUSP3 phosphatase, also known as Vaccinia-H1 Related (VHR) phosphatase, encoded by DUSP3/Dusp3 gene, is a relatively small member of the dual-specificity protein phosphatases. In vitro studies showed that DUSP3 is a negative regulator of ERK and JNK pathways in several cell lines. On the other hand, DUSP3 is implicated in human cancer. It has been alternatively described as having tumor suppressive and oncogenic properties. Thus, the available data suggest that DUSP3 plays complex and contradictory roles in tumorigenesis that could be cell type-dependent. Since most of these studies were performed using recombinant proteins or in cell-transfection based assays, the physiological function of DUSP3 has remained elusive. Results Using immunohistochemistry on human cervical sections, we observed a strong expression of DUSP3 in endothelial cells (EC) suggesting a contribution for this phosphatase to EC functions. DUSP3 downregulation, using RNA interference, in human EC reduced significantly in vitro tube formation on Matrigel and spheroid angiogenic sprouting. However, this defect was not associated with an altered phosphorylation of the documented in vitro DUSP3 substrates, ERK1/2, JNK1/2 and EGFR but was associated with an increased PKC phosphorylation. To investigate the physiological function of DUSP3, we generated Dusp3-deficient mice by homologous recombination. The obtained DUSP3-/- mice were healthy, fertile, with no spontaneous phenotype and no vascular defect. However, DUSP3 deficiency prevented neo-vascularization of transplanted b-FGF containing Matrigel and LLC xenograft tumors as evidenced by hemoglobin (Hb) and FITC-dextran quantifications. Furthermore, we found that DUSP3 is required for b-FGF-induced microvessel outgrowth in the aortic ring assay. Conclusions All together, our data identify DUSP3 as a new important player in angiogenesis. [less ▲]Detailed reference viewed: 95 (25 ULg)
An interaction map for HTLV-1 Tax and PDZ-containing proteins
Blibek, Karim ; Rambout, Xavier ; et al
in Retrovirology (2014), 11Detailed reference viewed: 20 (3 ULg)
Predicting interactome networks perturbations in human cancer: application to gene fusions in acute lymphoblastic leukemia.
; Daakour, Sarah ; Martin, Maud et al
in Molecular biology of the cell (2014)
Genomic variations such as point mutations and gene fusions are directly or indirectly associated with human diseases. They are recognized as diagnostic, prognostic markers and therapeutic targets ... [more ▼]
Genomic variations such as point mutations and gene fusions are directly or indirectly associated with human diseases. They are recognized as diagnostic, prognostic markers and therapeutic targets. However, predicting the functional impact of these genetic alterations beyond affected genes and their products is challenging because diseased phenotypes are likely dependent of complex molecular interaction networks. Using as models three different chromosomal translocations ETV6-RUNX1 (TEL-AML1), BCR-ABL1, and TCF3-PBX1 (E2A-PBX1), frequently found in precursor-B cell acute lymphoblastic leukemia (preB-ALL), we develop an approach to extract perturbed molecular interactions from gene expression changes. We show that the MYC and JunD transcriptional circuits are specifically deregulated following ETV6-RUNX1 and TCF3-PBX1 gene fusions, respectively. We also identified the bulk mRNA NXF1-dependent machinery as a direct target for the TCF3-PBX1 fusion protein. Through a novel approach combining gene expression and interactome data analysis, we provide new insight into TCF3-PBX1 and ETV6-RUNX1 acute lymphoblastic leukemia. [less ▲]Detailed reference viewed: 61 (5 ULg)
An interaction map for HTLV-1 Tax and PDZ-containing proteins.
Blibek, Karim ; Rambout, Xavier ; 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 ▲]Detailed reference viewed: 69 (17 ULg)
Inhibition of Tax transformation activity using a small molecule targetting Tax/PDZ domain interactions.
Blibek, Karim ; ; et al
Poster (2013, June 29)
Primate T-lymphotropic virus species comprise four members (HTLV-1 to -4) that have been discovered in human. Only the HTLV-1 infection leads to adult T-cell leukemia/lymphoma (ATLL) and tropical spastic ... [more ▼]
Primate T-lymphotropic virus species comprise four members (HTLV-1 to -4) that have been discovered in human. Only the HTLV-1 infection leads to adult T-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis (TSP), an immune degenerative neurologic syndrome. All the four viruses share a similar genomic organization and encode transforming Tax oncoproteins. In contrast to HTLV-2 and 4, HTLV-1 and 3 Tax proteins contain a PSD-95/Drosophila Discs Large/Zona Occludens-I (PDZ) binding motif at their C-terminal that has been shown to play crucial roles in the distinct transforming properties of the Tax proteins. To systematically investigate PDZ-containing proteins roles in HTLV-1 biology, we initiated a global interactome network analysis of Tax and associated human PDZ-containing proteins. This was accomplished through the use of our framework of binary interactome mapping that includes stringent yeast two hybrid and pulldown screening, systematic retesting by protein complementation assay and evaluation of PDZ gene expression in T lymphocytes. [less ▲]Detailed reference viewed: 55 (5 ULg)
Interactomic map of the Ets factors family : Identification of unexpected functions in mRNA processing
Rambout, Xavier ; ; 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 ▲]Detailed reference viewed: 78 (13 ULg)
CTIP2 is a negative regulator of P-TEFb.
Cherrier, Thomas ; ; et al
in Proceedings of the National Academy of Sciences of the United States of America (2013), 110(31), 12655-60
The positive transcription elongation factor b (P-TEFb) is involved in physiological and pathological events including inflammation, cancer, AIDS, and cardiac hypertrophy. The balance between its active ... [more ▼]
The positive transcription elongation factor b (P-TEFb) is involved in physiological and pathological events including inflammation, cancer, AIDS, and cardiac hypertrophy. The balance between its active and inactive form is tightly controlled to ensure cellular integrity. We report that the transcriptional repressor CTIP2 is a major modulator of P-TEFb activity. CTIP2 copurifies and interacts with an inactive P-TEFb complex containing the 7SK snRNA and HEXIM1. CTIP2 associates directly with HEXIM1 and, via the loop 2 of the 7SK snRNA, with P-TEFb. In this nucleoprotein complex, CTIP2 significantly represses the Cdk9 kinase activity of P-TEFb. Accordingly, we show that CTIP2 inhibits large sets of P-TEFb- and 7SK snRNA-sensitive genes. In hearts of hypertrophic cardiomyopathic mice, CTIP2 controls P-TEFb-sensitive pathways involved in the establishment of this pathology. Overexpression of the beta-myosin heavy chain protein contributes to the pathological cardiac wall thickening. The inactive P-TEFb complex associates with CTIP2 at the MYH7 gene promoter to repress its activity. Taken together, our results strongly suggest that CTIP2 controls P-TEFb function in physiological and pathological conditions. [less ▲]Detailed reference viewed: 45 (3 ULg)
PP2A regulatory subunit Balpha controls endothelial contractility and vessel lumen integrity via regulation of HDAC7.
Martin, Maud ; ; et al
in EMBO Journal (2013)
To supply tissues with nutrients and oxygen, the cardiovascular system forms a seamless, hierarchically branched, network of lumenized tubes. Here, we show that maintenance of patent vessel lumens ... [more ▼]
To supply tissues with nutrients and oxygen, the cardiovascular system forms a seamless, hierarchically branched, network of lumenized tubes. Here, we show that maintenance of patent vessel lumens requires the Balpha regulatory subunit of protein phosphatase 2A (PP2A). Deficiency of Balpha in zebrafish precludes vascular lumen stabilization resulting in perfusion defects. Similarly, inactivation of PP2A-Balpha in cultured ECs induces tubulogenesis failure due to alteration of cytoskeleton dynamics, actomyosin contractility and maturation of cell-extracellular matrix (ECM) contacts. Mechanistically, we show that PP2A-Balpha controls the activity of HDAC7, an essential transcriptional regulator of vascular stability. In the absence of PP2A-Balpha, transcriptional repression by HDAC7 is abrogated leading to enhanced expression of the cytoskeleton adaptor protein ArgBP2. ArgBP2 hyperactivates RhoA causing inadequate rearrangements of the EC actomyosin cytoskeleton. This study unravels the first specific role for a PP2A holoenzyme in development: the PP2A-Balpha/HDAC7/ArgBP2 axis maintains vascular lumens by balancing endothelial cytoskeletal dynamics and cell-matrix adhesion. [less ▲]Detailed reference viewed: 62 (20 ULg)
Phosphorylation of p65(RelA) on Ser547 by ATM represses NF-κB-dependent transcription of specific genes after genotoxic stress.
Sabatel, Hélène ; Di Valentin, Emmanuel ; Gloire, Geoffrey et al
in PLoS ONE (2012)
The NF-κB pathway is involved in immune and inflammation responses, proliferation, differentiation and cell death or survival. It is activated by many external stimuli including genotoxic stress. DNA ... [more ▼]
The NF-κB pathway is involved in immune and inflammation responses, proliferation, differentiation and cell death or survival. It is activated by many external stimuli including genotoxic stress. DNA double-strand breaks activate NF-κB in an ATM-dependent manner. In this manuscript, a direct interaction between p65(RelA) and the N-terminal extremity of ATM is reported. We also report that only one of the five potential ATM-(S/T)Q target sites present in p65, namely Ser547, is specifically phosphorylated by ATM in vitro. A comparative transcriptomic analysis performed in HEK-293 cells expressing either wild-type HA-p65 or a non-phosphorylatable mutant HA-p65S547A identified several differentially transcribed genes after an etoposide treatment (e.g. IL8, A20, SELE). The transcription of these genes is increased in cells expressing the mutant. Substitution of Ser547 to alanine does not affect p65 binding abilities on the κB site of the IL8 promoter but reduces p65 interaction with HDAC1. Cells expressing p65S547A have a higher level of histone H3 acetylated on Lys9 at the IL8 promoter, which is in agreement with the higher gene induction observed. These results indicate that ATM regulates a sub-set of NF-κB dependent genes after a genotoxic stress by direct phosphorylation of p65. [less ▲]Detailed reference viewed: 53 (19 ULg)