Ribosomes that cannot terminate translation pause and their 60S subunits remain stalled with peptidyl-tRNA-associated nascent chains. The listerin E3 ubiquitin protein ligase 1 (Ltn1) and its cofactors, which make up the large ribosomal subunit-associated quality control complex (RQC), then target these chains for proteasomal degradation. Lyumkis et al. determined the structure of the yeast RQC bound to stalled 60S ribosome subunits using single-particle cryoelectron microscopy. They revealed that the RQC subunit Tae2 recognizes, and interacts with, the exposed tRNA of the stalled 60S-associated peptidyl-tRNA, providing insight into how RQC selectively recognizes aberrant nascent chains. They also showed that the C terminus of Ltn1 binds to the 60S subunit near the nascent polypeptide exit tunnel, which positions the Ltn1 RING domain to ubiquitylate the stalled nascent chains. This study increases our understanding of how protein translation and degradation are co-regulated.
References
Lyumkis, D. et al. Structural basis for translational surveillance by the large ribosomal subunit-associated protein quality control complex. Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1413882111 (2014)
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Wrighton, K. Piecing together protein quality control. Nat Rev Mol Cell Biol 15, 767 (2014). https://doi.org/10.1038/nrm3913
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DOI: https://doi.org/10.1038/nrm3913