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Caractérisation de la fonction "La" chez Arabidopsis thaliana et identification d'une structure conservée pour les ARN non-codants de type SINE

Abstract : SINEs are mobile DNA elements found in almost all eukaryotes. Study of SINEs first focused on their retroposition mechanism, mutagenic effect and general impact on the structure and evolution of genomes. However SINE RNAs have recently been proposed to act as cellular riboregulators. Studying cis and trans elements taking part in the metabolism of SINE RNA in the model plant Arabidopsis thaliana, we aim to better understand SINE element biology. First, we experimentally defined the secondary structure of two tRNA-related SINE RNA: SB1 from Brassica napus and SB2 from Arabidopsis. Although unrelated at the primary sequence level, we found that these RNAs present similar secondary structures. Following this observation, an in silico analysis including tRNA-related SINE RNAs from various eukaryotes has been performed by FJ Sun, G Caetano-Anollés and JM Deragon. This study underlines the existence of common evolutionary trends for SINE RNA secondary structure that could be linked with the SINE RNA riboregulators function. Searching for trans factors involved in SINE RNA metabolism, we have chosen to characterise the La protein, an ubiquitous RNA-binding protein involved in the metabolism of various RNAs, from non-coding RNA to cellular or viral mRNA. Unlike other eukaryotes, which have only one La protein, we identified in Arabidopsis two proteins with the phylogenetic and structural characteristics of genuine La protein: At32 and At79. We showed that At32 (renamed AtLa1) is able to fulfil La nuclear functions in non-coding RNA maturation, including SINE RNA. We also demonstrate that loss of AtLa1 function leads to embryonic lethality. Although AtLa1 and At79 have the same nuclear localisation, loss of At79 function did not affect viability. AtLa1 and At79 have differing levels and profiles of expression. Furthermore, the AtLa1 and At79 proteins apparently bind distinct sets of RNA. We thus propose that Arabidopsis possess two functional homologues of the La protein, which have partially specialised to fulfil different aspects of the La function.
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https://tel.archives-ouvertes.fr/tel-00718377
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Submitted on : Monday, July 16, 2012 - 5:36:40 PM
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Sophie Fleurdépine. Caractérisation de la fonction "La" chez Arabidopsis thaliana et identification d'une structure conservée pour les ARN non-codants de type SINE. Génétique. Université Blaise Pascal - Clermont-Ferrand II; Université d'Auvergne - Clermont-Ferrand I, 2007. Français. ⟨NNT : 2007CLF21791⟩. ⟨tel-00718377⟩

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