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Etude structurale de protéines virales impliquées dans la réplication et régulation du cycle de multiplication d'un virus de plante

Abstract : Turnip Yellow Mosaic Virus is an excellent model for positive-stranded RNA virus replication. It’s a small plant virus whose replication machinery is encoded in the viralgenome as a single polyprotein (206K). From N- to C-terminus, this 206K harbors amethyltransferase, a cysteine proteinase (PRO), a helicase and an RNA-dependent RNApolymerase (POL). As in all RNA(+) viruses known, the replication complex is bound to cellmembranes. For TYMV, it ,is the chloroplast envelope that is implicated. A key component inthe replication process is the polymerase, that allows the synthesis of new genomes. The regulation of its activity involves initially its cleavage by PRO from the 206K. Once liberated,the polymerase is recruited to the chloroplasts through a direct interaction with the PROdomain, contained in 140K, in order to form the replication complex. A second cleavage of140K by PRO at the PRO-helicase junction allows to continue the replication cycle. Recently,it has also been shown that the POL activity was regulated by the ubiquitin-proteasomesystem during the viral multiplication cycle. Ubiquitinilated by the host cell, POL is addressed to the proteasome where it is degraded. However, PRO, due to its second function as an ubiquitin hydrolase, is able to protect POL from its degradation. In order to characterizethis mechanism of replication regulation with a structural point of view, we crystallized,assisted by contaminant, PRO and resolved its structure. In the crystal packing, the C-terminalof a PRO domain is inserted into the catalytic cleft of the next PRO domain, thus providing us structural informations on its endopeptidase activity. In a second step, in order to obtain information about its second activity, we made a stable complex between PRO and amolecule of ubiquitin in order to cristallise it. Finally, we initiated the crystallographic studyof POL.Keywords:
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Submitted on : Friday, January 20, 2012 - 2:14:09 PM
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  • HAL Id : tel-00661702, version 1
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Charlotte Robin. Etude structurale de protéines virales impliquées dans la réplication et régulation du cycle de multiplication d'un virus de plante. Sciences agricoles. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA114853⟩. ⟨tel-00661702⟩



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