Baptist Jammart

Institut de Génétique Moléculaire de Montpellier, Montpelhièr, Languedoc-Roussillon, France

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Publications (3)25.18 Total impact

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    ABSTRACT: Author Summary Viruses exploit cellular functions during entry and exit of cells. To redirect cellular functions for their own purpose, viruses encode high-affinity binding sites for key-cellular factors. One such domain is the PPxY motif, which is present in structural proteins of several, mainly enveloped viruses. This motif binds to ubiquitin ligases of the Nedd4 family and recruits their function to sites of virus budding from cells. Here we show that adenoviruses also encode a PPxY motif in the internal structural protein VI and that the PPxY motif has an unprecedented function in virus entry. Adenoviruses with mutations in the protein VI PPxY motif undergo normal endosomal uptake and membrane penetration but have reduced infectivity, altered intracellular targeting and lack efficient gene-delivery. We also find that protein VI is ubiquitylated by Nedd4 ligases in a PPxY dependent manner following partial capsid disassembly and displays rapid intracellular movement. Depletion of Nedd4 ligases also alters virus movement within cells during entry and reduces viral infectivity. Given that PPxY motifs are important for virus exit our findings might have uncovered an additional function for PPxY motifs in virus entry, potentially expanding the significance of PPxY motifs and functionally related domains for viral replication.
    PLoS Pathogens 03/2010; 6(3):e1000808. DOI:10.1371/journal.ppat.1000808 · 8.06 Impact Factor
  • Oncogene 07/2009; · 8.56 Impact Factor
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    ABSTRACT: HIPK2 is a eukaryotic Serine-Threonine kinase that controls cellular proliferation and survival in response to exogenous signals. Here, we show that the human transcription factor ZBTB4 is a new target of HIPK2. The two proteins interact in vitro, colocalize and associate in vivo, and HIPK2 phosphorylates several conserved residues of ZBTB4. Overexpressing HIPK2 causes the degradation of ZBTB4, whereas overexpressing a kinase-deficient mutant of HIPK2 has no effect. The chemical activation of HIPK2 also decreases the amount of ZBTB4 in cells. Conversely, the inhibition of HIPK2 by drugs or by RNA interference causes a large increase in ZBTB4 levels. This negative regulation of ZBTB4 by HIPK2 occurs under normal conditions of cell growth. In addition, the degradation is increased by DNA damage. These findings have two consequences. First, we have recently shown that ZBTB4 inhibits the transcription of p21. Therefore, the activation of p21 by HIPK2 is two-pronged: stimulation of the activator p53, and simultaneous repression of the inhibitor ZBTB4. Second, ZBTB4 is also known to bind methylated DNA and repress methylated sequences. Consequently, our findings raise the possibility that HIPK2 might influence the epigenetic regulation of gene expression at loci that remain to be identified.
    Oncogene 06/2009; 28(27):2535-44. DOI:10.1038/onc.2009.109 · 8.56 Impact Factor