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Caracterisation moleculaire et fonctionn Caracterisation moleculaire et fonctionn... - PDF Document (8 M)
Caracterisation moleculaire et fonctionnelle de la proteine DYWI dans le complexe d'edition chloroplastique d'Arabidopsis thaliana = Molecular and functional characterization of the DYWI protein in the chloroplast editing of Arabidopsis thaliana / par Clement Boussardon
In plant organelles, RNA editing mostly takes the form of conversions of cytidines to uridines at specific sites in mRNAs. Thirty-four editing sites have been found in Arabidopsis thaliana chloroplast transcripts and more than 500 sites in mitochondrial transcripts. Since 2005, lots of proteins have been found to act as RNA editing factors. Most of these proteins belong to the PentatricoPeptide Repeat (PPR) family. Amongst these PPR proteins, some contain a DYW domain with weak similarity to cytidine deaminases (CDA), whilst others lack such a domain, creating doubts about whether this domain could have CDA activity and whether it is required for editing. The gene At1g47580 (named DYW1) encodes a protein in Arabidopsis thaliana that contains "only" a DYW domain. Our initial hypothesis was that the DYW1 protein might interact with PPR proteins that lack a DYW domain, in order to form a heterodimer, able to perform site-specific editing. In accordance with this hypothesis, we discovered that DYW1 is involved in editing the same site as CRR4, a PPR lacking a DYW domain, and that these two proteins interact together in vivo. Moreover, we showed that DYW1 replaces all the missing parts of CRR4 for editing. However, DYW1 is highly specific for CRR4, so other partners need to be hypothesized for the dozens of other DYW-lacking editing factors if this hypothesis is to be generalized. In an attempt to learn more about the function of the DYW domain, point mutations were introduced into DYW1. The highly conserved residues making up the CDA signature in DYW proteins were found to be essential for RNA editing and are also required for zinc binding, which is a known characteristic of CDAs. All the data so far are consistent with the DYW domain being (part of) a CDA activity; nevertheless, no CDA activity could be detected in vitro, or following expression in yeast or bacteria. It
is likely that at least one required cofactor remains to be identified.
Thesis (Ph.D.)--University of Western Australia, 2014
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