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See detailL’expérimentation animale reste indispensable (OPINION)
Amorim, Christiani; Andris, Fabienne; Arckens, Lut et al

Article for general public (2017)

Trop fréquemment, l’expérimentation animale est présentée comme une pratique archaïque. Elle a bien changé. Et 100 % des patients traités le sont grâce aux concepts et techniques développés grâce à elle.

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See detailKPC2 relocalizes HOXA2 to the cytoplasm and decreases its transcriptional activity.
Bridoux, Laure; Bergiers, Isabelle; Draime, Amandine et al

in Biochimica et Biophysica Acta (2015), 1849(10), 1298-311

Regulation of transcription factor activity relies on molecular interactions or enzymatic modifications which influence their interaction with DNA cis-regulatory sequences, their transcriptional ... [more ▼]

Regulation of transcription factor activity relies on molecular interactions or enzymatic modifications which influence their interaction with DNA cis-regulatory sequences, their transcriptional activation or repression, and stability or intracellular distribution of these proteins. Regarding the well-conserved Hox protein family, a restricted number of activity regulators have been highlighted thus far. In the framework of a proteome-wide screening aiming at identifying proteins interacting with Hoxa2, KPC2, an adapter protein constitutive of the KPC ubiquitin-ligase complex, was identified. In this work, KPC2 was confirmed as being a genuine interactor of Hoxa2 by co-precipitation and bimolecular fluorescence complementation assays. At functional level, KPC2 diminishes the transcriptional activity and induces the nuclear exit of Hoxa2. Gene expression analyses revealed that Kpc2 is active in restricted areas of the developing mouse embryo which overlap with the Hoxa2 expression domain. Together, our data support that KPC2 regulates Hoxa2 by promoting its relocation to the cytoplasm. [less ▲]

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See detailHox protein interactions: screening and network building.
Bergiers, Isabelle; Lambert, Barbara; Daakour, Sarah ULiege et al

in Methods in Molecular Biology (2014), 1196

Understanding the mode of action of Hox proteins requires the identification of molecular and cellular pathways they take part in. This includes to characterize the networks of protein-protein ... [more ▼]

Understanding the mode of action of Hox proteins requires the identification of molecular and cellular pathways they take part in. This includes to characterize the networks of protein-protein interactions involving Hox proteins. In this chapter we propose a strategy and methods to map Hox interaction networks, from yeast two-hybrid and high-throughput yeast two-hybrid interaction screening to bioinformatic analyses based on the software platform Cytoscape. [less ▲]

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See detailThe homeodomain transcription factor Hoxa2 interacts with and promotes the proteasomal degradation of the E3 ubiquitin protein ligase RCHY1.
Bergiers, Isabelle; Bridoux, Laure; Nguyen, Nathan et al

in PLoS ONE (2013), 8(11), 80387

Hox proteins are conserved homeodomain transcription factors known to be crucial regulators of animal development. As transcription factors, the functions and modes of action (co-factors, target genes) of ... [more ▼]

Hox proteins are conserved homeodomain transcription factors known to be crucial regulators of animal development. As transcription factors, the functions and modes of action (co-factors, target genes) of Hox proteins have been very well studied in a multitude of animal models. However, a handful of reports established that Hox proteins may display molecular activities distinct from gene transcription regulation. Here, we reveal that Hoxa2 interacts with 20S proteasome subunits and RCHY1 (also known as PIRH2), an E3 ubiquitin ligase that targets p53 for degradation. We further show that Hoxa2 promotes proteasome-dependent degradation of RCHY1 in an ubiquitin-independent manner. Correlatively, Hoxa2 alters the RCHY1-mediated ubiquitination of p53 and promotes p53 stabilization. Together, our data establish that Hoxa2 can regulate the proteasomal degradation of RCHY1 and stabilization of p53. [less ▲]

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See detailProtein interactions of the transcription factor Hoxa1.
Lambert, Barbara; Vandeputte, Julie; Remacle, Sophie et al

in BMC Developmental Biology (2012), 12

BACKGROUND: Hox proteins are transcription factors involved in crucial processes during animal development. Their mode of action remains scantily documented. While other families of transcription factors ... [more ▼]

BACKGROUND: Hox proteins are transcription factors involved in crucial processes during animal development. Their mode of action remains scantily documented. While other families of transcription factors, like Smad or Stat, are known cell signaling transducers, such a function has never been squarely addressed for Hox proteins. RESULTS: To investigate the mode of action of mammalian Hoxa1, we characterized its interactome by a systematic yeast two-hybrid screening against ~12,200 ORF-derived polypeptides. Fifty nine interactors were identified of which 45 could be confirmed by affinity co-purification in animal cell lines. Many Hoxa1 interactors are proteins involved in cell-signaling transduction, cell adhesion and vesicular trafficking. Forty-one interactions were detectable in live cells by Bimolecular Fluorescence Complementation which revealed distinctive intracellular patterns for these interactions consistent with the selective recruitment of Hoxa1 by subgroups of partner proteins at vesicular, cytoplasmic or nuclear compartments. CONCLUSIONS: The characterization of the Hoxa1 interactome presented here suggests unexplored roles for Hox proteins in cell-to-cell communication and cell physiology. [less ▲]

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See detailThe Pbx Interaction Motif of Hoxa1 Is Essential for Its Oncogenic Activity
Delval, Stéphanie; Taminiau, Arnaud; Lamy, Juliette et al

in PLoS ONE (2011), 6(9), 2547

Hoxa1 belongs to the Hox family of homeodomain transcription factors involved in patterning embryonic territories and governing organogenetic processes. In addition to its developmental functions, Hoxa1 ... [more ▼]

Hoxa1 belongs to the Hox family of homeodomain transcription factors involved in patterning embryonic territories and governing organogenetic processes. In addition to its developmental functions, Hoxa1 has been shown to be an oncogene and to be overexpressed in the mammary gland in response to a deregulation of the autocrine growth hormone. It has therefore been suggested that Hoxa1 plays a pivotal role in the process linking autocrine growth hormone misregulation and mammary carcinogenesis. Like most Hox proteins, Hoxa1 can interact with Pbx proteins. This interaction relies on a Hox hexapeptidic sequence centred on conserved Tryptophan and Methionine residues. To address the importance of the Hox-Pbx interaction for the oncogenic activity of Hoxa1, we characterized here the properties of a Hoxa1 variant with substituted residues in the hexapeptide and demonstrate that the Hoxa1 mutant lost its ability to stimulate cell proliferation, anchorage-independent cell growth, and loss of contact inhibition. Therefore, the hexapeptide motif of Hoxa1 is required to confer its oncogenic activity, supporting the view that this activity relies on the ability of Hoxa1 to interact with Pbx. [less ▲]

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See detailExpression of Hoxa2 in cells entering chondrogenesis impairs overall cartilage development.
Massip, Laurent; Ectors, Fabien ULiege; Deprez, Pierre et al

in Differentiation: Research in Biological Diversity (2007), 75(3), 256-67

Vertebrate Hox genes act as developmental architects by patterning embryonic structures like axial skeletal elements, limbs, brainstem territories, or neural crest derivatives. While active during the ... [more ▼]

Vertebrate Hox genes act as developmental architects by patterning embryonic structures like axial skeletal elements, limbs, brainstem territories, or neural crest derivatives. While active during the patterning steps of development, these genes turn out to be down-regulated in specific differentiation programs like that leading to chondrogenesis. To investigate why chondrocyte differentiation is correlated to the silencing of a Hox gene, we generated transgenic mice allowing Cre-mediated conditional misexpression of Hoxa2 and induced this gene in Collagen 2 alpha 1-expressing cells committed to enter chondrogenesis. Persistent Hoxa2 expression in chondrogenic cells resulted in overall chondrodysplasia with delayed cartilage hypertrophy, mineralization, and ossification but without proliferation defects. The absence of skeletal patterning anomaly and the regular migration of precursor cells indicated that the condensation step of chondrogenesis was normal. In contrast, closer examination at the differentiation step showed severely impaired chondrocyte differentiation. In addition, this inhibition affected structures independently of their embryonic origin. In conclusion, for the first time here, by a cell-type specific misexpression, we precisely uncoupled the patterning function of Hoxa2 from its involvement in regulating differentiation programs per se and demonstrate that Hoxa2 displays an anti-chondrogenic activity that is distinct from its patterning function. [less ▲]

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