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A SKI subcomplex specifically required for the degradation of ribosome-free RNA regions

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Zhang, Elodie | Khanna, Varun | Namane, Abdelkader | Doyen, Antonia | Dacheux, Estelle | Turcotte, Bernard | Jacquier, Alain | Fromont-Racine, Micheline

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Posté sur bioRxiv le 6 septembre 2018.. The Ski2-Ski3-Ski8 (SKI) complex assists the RNA exosome during the 3’-5’ degradation of cytoplasmic transcripts. Previous reports showed that the SKI complex is involved in the 3’-5’ degradation of mRNA, including 3’ untranslated regions (UTRs), devoid of ribosomes. Paradoxically, we recently showed that the SKI complex directly interacts with ribosomes during the co-translational mRNA decay and that this interaction is necessary for its RNA degradation promoting activity. Here, we characterized a new SKI-associated factor, Ska1, which antagonizes the SKI-ribosome interaction. We showed that the SKI-Ska1-subcomplex is specifically involved in the degradation of ribosome-free RNA regions such as long mRNA 3’UTRs and cytoplasmic lncRNAs. We propose a model in which the SKI-exosome complex first targets ribosome-free RNA 3’ends in its Ska1-associated form. When the complex reaches the mRNA coding sequence, the Ska1-SKI-exosome complex is exchanged for the SKI-exosome, which interacts directly with ribosomes in order to resume the degradation process.

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