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RQT complex dissociates ribosomes collided on endogenous RQC substrate SDD1
Yoshitaka Matsuo1, Petr Tesina2, Shizuka Nakajima1
1Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Nature Structural & Molecular Biology
|March 24, 2020
Summary
Ribosome-associated quality control (RQC) rescues cells from stalled protein synthesis. This study reveals how specific mRNA sequences trigger RQC, leading to ribosome dissociation and peptide degradation for cellular protein homeostasis.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Ribosome-associated quality control (RQC) is a cellular pathway that resolves translational stalling.
- RQC involves ribosome dissociation and nascent peptide degradation.
- Endogenous triggers and mechanisms of RQC are not fully understood.
Purpose of the Study:
- To identify endogenous RQC-inducing sequences.
- To elucidate the mechanism of RQC-mediated ribosome dissociation.
- To understand the role of RQC in maintaining protein homeostasis.
Main Methods:
- In vitro translation assays using Saccharomyces cerevisiae SDD1 mRNA.
- Cryo-electron microscopy (cryo-EM) for structural analysis.
- Biochemical assays to study ubiquitination and ribosome dissociation.
Main Results:
- SDD1 mRNA was identified as an endogenous RQC substrate.
- Hel2-dependent polyubiquitination of collided ribosomes (disomes and trisomes) was reconstituted in vitro.
- Cryo-EM revealed a trisome architecture facilitating Hel2 recognition.
- The RQT complex, containing Slh1, dissociates stalled polyubiquitinated ribosomes.
Conclusions:
- SDD1 mRNA triggers RQC through mRNA- and peptide-dependent stalling.
- The study provides structural and mechanistic insights into Hel2-mediated ubiquitination of collided ribosomes.
- Slh1 facilitates the dissociation of stalled ribosomes, contributing to protein homeostasis.
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