Cdc48-associated complex bound to 60S particles is required for the clearance of aberrant translation products

Quentin Defenouillere (1) , Yanhua Yao , John Mouaikel (1) , Abdelkader Namane (1) , Aurélie Galopier (1) , Laurence Decourty (1) , Antonia Doyen (1) , Christophe Malabat (1) , Cosmin Saveanu (1) , Alain Jacquier (1) , Micheline Fromont-Racine (1)

1 Génétique des Interactions macromoléculaires / Genetics of Macromolecular Interactions

Ribosome stalling on eukaryotic mRNAs triggers cotranslational RNA and protein degradation through conserved mechanisms. For example, mRNAs lacking a stop codon are degraded by the exosome in association with its cofactor, the SKI complex, whereas the corresponding aberrant nascent polypeptides are ubiquitinated by the E3 ligases Ltn1 and Not4 and become proteasome substrates. How translation arrest is linked with polypeptide degradation is still unclear. Genetic screens with SKI and LTN1 mutants allowed us to identify translation-associated element 2 (Tae2) and ribosome quality control 1 (Rqc1), two factors that we found associated, together with Ltn1 and the AAA-ATPase Cdc48, to 60S ribosomal subunits. Translation-associated element 2 (Tae2), Rqc1, and Cdc48 were all required for degradation of polypeptides synthesized from Non-Stop mRNAs (Non-Stop protein decay; NSPD). Both Ltn1 and Rqc1 were essential for the recruitment of Cdc48 to 60S particles. Polysome gradient analyses of mutant strains revealed unique intermediates of this pathway, showing that the polyubiquitination of Non-Stop peptides is a progressive process. We propose that ubiquitination of the nascent peptide starts on the 80S and continues on the 60S, on which Cdc48 is recruited to escort the substrate for proteasomal degradation.

Mots clés: Ubiquitin-Protein Ligases; Large; Eukaryotic; Saccharomyces cerevisiae; Adenosine Triphosphatases; Cell Cycle Proteins; Proteasome Endopeptidase Complex; Protein Biosynthesis; Proteolysis; Ribosome Subunits; Saccharomyces cerevisiae Proteins; Ubiquitination

Domaines: Sciences du Vivant [q-bio]; Biochimie, Biologie Moléculaire

Quentin Defenouillere, Yanhua Yao, John Mouaikel, Abdelkader Namane, Aurélie Galopier, et al.. Cdc48-associated complex bound to 60S particles is required for the clearance of aberrant translation products. Proceedings of the National Academy of Sciences of the United States of America, 2013, 110 (13), pp.5046--5051. ⟨10.1073/pnas.1221724110⟩. ⟨pasteur-01404018⟩