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Dissecting the molecular puzzle of the editosome core in Arabidopsis organelles
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International audience. Over the last decade, the composition of the C-to-U RNA editing complex in embryophyte organelles has turnedout to be much more complex than first expected. While PPR proteins were initially thought to act alone, sig-nificant evidences have clearly depicted a sophisticated mechanism with numerous protein-protein interactioninvolving PPR and non-PPR proteins. Moreover, the identification of specific functional partnership betweenPPRs also suggests that, in addition to the highly specific PPRs directly involved in the RNA target recognition,non-RNA-specific ones are required. Although some of them, such as DYW1 and DYW2, were shown to be thecatalytic domains of the editing complex, the molecular function of others, such as NUWA, remains elusive. Itwas suggested that they might stabilize the complex by acting as a scaffold. We here performed functionalcomplementation of the crr28–2 mutant with truncated CRR28 proteins mimicking PPR without the catalyticdomain and show that they exhibit a specific dependency to one of the catalytic proteins DYW1 or DYW2.Moreover, we also characterized the role of the PPR NUWA in the editing reaction and show that it likely acts as ascaffolding factor. NUWA is no longer required for efficient editing of the CLB19 editing sites once this RNAspecific PPR is fused to the DYW catalytic domain of its partner DYW2. Altogether, our results strongly support aflexible, evolutive and resilient editing complex in which RNA binding activity, editing activity and stabilization/scaffolding function can be provided by one or more PPRs.
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