查看文章

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 …