Download MendeleyMimicry of Canonical Translation Elongation Underlies Alanine Tail Synthesis in RQC.
Filbeck, S., Cerullo, F., Paternoga, H., Tsaprailis, G., Joazeiro, C.A.P., Pfeffer, S.(2021) Mol Cell 81: 104
- PubMed: 33259811
- DOI: https://doi.org/10.1016/j.molcel.2020.11.001
- Primary Citation of Related Structures:
7AQC, 7AQD - PubMed Abstract:
Aborted translation produces large ribosomal subunits obstructed with tRNA-linked nascent chains, which are substrates of ribosome-associated quality control (RQC). Bacterial RqcH, a widely conserved RQC factor, senses the obstruction and recruits tRNA Ala(UGC) to modify nascent-chain C termini with a polyalanine degron. However, how RqcH and its eukaryotic homologs (Rqc2 and NEMF), despite their relatively simple architecture, synthesize such C-terminal tails in the absence of a small ribosomal subunit and mRNA has remained unknown. Here, we present cryoelectron microscopy (cryo-EM) structures of Bacillus subtilis RQC complexes representing different Ala tail synthesis steps. The structures explain how tRNA Ala is selected via anticodon reading during recruitment to the A-site and uncover striking hinge-like movements in RqcH leading tRNA Ala into a hybrid A/P-state associated with peptidyl-transfer. Finally, we provide structural, biochemical, and molecular genetic evidence identifying the Hsp15 homolog (encoded by rqcP) as a novel RQC component that completes the cycle by stabilizing the P-site tRNA conformation. Ala tailing thus follows mechanistic principles surprisingly similar to canonical translation elongation.
Organizational Affiliation:
Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
