Julie Charollais

École Polytechnique Fédérale de Lausanne, Lausanne, VD, Switzerland

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Publications (5)18.25 Total impact

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    Julie Charollais, F Gisou Van Der Goot
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    ABSTRACT: S-Palmitoylation is a reversible post-translational modification that results in the addition of a C16-carbon saturated fatty acyl chain to cytoplasmic cysteine residues. This modification is mediated by Palmitoyl-acyl Transferases that are starting to be investigated, and reversed by Protein Palmitoyl Thioesterases, which remain enigmatic. Palmitoylation of cytoplasmic proteins has been well described to regulate the interaction of these soluble proteins with specific membranes or membrane domains. Less is known about the consequences of palmitoylation in transmembrane proteins not only due to the dual difficulty of following a lipid modification and dealing with membrane proteins, but also due to the complexity of the palmitoylation-induced behavior. Moreover, possibly because the available data set is limited, the change in behavior induced by palmitoylation of a transmembrane protein is currently not predictable. We here review the various consequences reported for the palmitoylation of membrane proteins, which include improper folding in the endoplasmic reticulum, retention in the Golgi, inability to assemble into protein platforms, altered signaling capacity, premature endocytosis and missorting in the endocytic pathway. We then discuss the possible underlying mechanisms, in particular the ability of palmitoylation to control the conformation of transmembrane segments, to modify the affinity of a membrane protein for specific membrane domains and to control protein-protein interactions.
    Molecular Membrane Biology 01/2009; 26(1):55-66. · 3.13 Impact Factor
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    ABSTRACT: This chapter describes the purification of ribosomal particles from a mutant strain of Escherichia coli using sucrose gradients and the characterization of their protein composition by a combination of mass spectrometry (MS) techniques. The main objective is to identify the ribosomal proteins that are missing in an aberrant ribosomal particle corresponding to a defective large subunit. To address this question, the tryptic digests of the purified ribosomal particles are analyzed by the coupling between liquid chromatography and tandem MS. The presence or absence of a given ribosomal protein in the defective particle is determined by comparing the MS intensities of its identified tryptic peptides with that of the mature large subunit. These analyses also allow identification of proteins copurifying with the ribosomal particles. To detect low-mass proteins escaping identification by the above method, intact proteins are also analyzed by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) and nano-ESI-QqTOF MS.
    Methods in molecular biology (Clifton, N.J.) 02/2008; 432:321-41. · 1.29 Impact Factor
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    ABSTRACT: This chapter describes the purification of ribosomal particles from a mutant strain of Escherichia coli using sucrose gradients and the characterization of their protein composition by a combination of mass spectrometry (MS) techniques. The main objective is to identify the ribosomal proteins that are missing in an aberrant ribosomal particle corresponding to a defective large subunit. To address this question, the tryptic digests of the purified ribosomal particles are analyzed by the coupling between liquid chromatography and tandem MS. The presence or absence of a given ribosomal protein in the defective particle is determined by comparing the MS intensities of its identified tryptic peptides with that of the mature large subunit. These analyses also allow identification of proteins copurifying with the ribosomal particles. To detect low-mass proteins escaping identification by the above method, intact proteins are also analyzed by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) and nano-ESI-QqTOF MS. Key Words E. coli –ribosomes–capillary liquid chromatography–tandem mass spectrometry–MALDI-TOF–nano-ESI-QqTOF
    12/2007: pages 321-341;
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    Julie Charollais, Marc Dreyfus, Isabelle Iost
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    ABSTRACT: CsdA, a DEAD-box protein from Escherichia coli, has been proposed to participate in a variety of processes, such as translation initiation, gene regulation after cold-shock, mRNA decay and biogenesis of the small ribosomal subunit. Whether the protein really plays a direct role in these multiple processes is however, not clear. Here, we show that CsdA is involved in the biogenesis of the large rather than the small ribosomal subunit. Deletion of the csdA gene leads to a deficit in free 50S subunits at low temperatures and to the accumulation of a new particle sedimenting around 40S. Analysis of the RNA and protein contents of this particle indicates that it corresponds to a mis-assembled large subunit. Sucrose gradient fractionation shows that in wild-type cells CsdA associates mainly with a pre50S particle. Presumably the RNA helicase activity of CsdA permits a structural rearrangement during 50S biogenesis at low temperature. We showed previously that SrmB, another DEAD-box RNA helicase, is also involved in 50S assembly in E.coli. Our results suggest that CsdA is required at a later step than SrmB. However, over-expression of CsdA corrects the ribosome defect of the srmB-deleted strain, indicating that some functional overlap exists between the two proteins.
    Nucleic Acids Research 02/2004; 32(9):2751-9. · 8.81 Impact Factor
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    ABSTRACT: Ribosome assembly in Escherichia coli involves 54 ribosomal proteins and three RNAs. Whereas functional subunits can be reconstituted in vitro from the isolated components, this process requires long incubation times and high temperatures compared with the in vivo situation, suggesting that non-ribosomal factors facilitate assembly in vivo. Here, we show that SrmB, a putative DEAD-box RNA helicase, is involved in ribosome assembly. The deletion of the srmB gene causes a slow-growth phenotype at low temperature. Polysome profile analyses of the corresponding cells reveal a deficit in free 50S ribosomal subunits and the accumulation of a new particle sedimenting around 40S. Analysis of the ribosomal RNA and protein contents of the 40S particle indicates that it represents a large subunit that is incompletely assembled. In particular, it lacks L13, one of the five ribosomal proteins that are essential for the early assembly step in vitro. Sucrose gradient fractionation also shows that, in wild-type cells, SrmB associates with a pre50S particle. From our results, we propose that SrmB is involved in an early step of 50S assembly that is necessary for the binding of L13. This step may consist of a structural rearrangement that, at low temperature, cannot occur without the assistance of this putative RNA helicase.
    Molecular Microbiology 07/2003; 48(5):1253-65. · 5.03 Impact Factor