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Cell. 2017 Nov 2;171(4):890-903.e18. doi: 10.1016/j.cell.2017.10.002. Epub 2017 Oct 26.

Cytosolic Protein Vms1 Links Ribosome Quality Control to Mitochondrial and Cellular Homeostasis.

Author information

1
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Division of Cell Biology, Biomedical Center, Faculty of Medicine, University of Munich, GroƟhaderner Strasse 9, 82152 Martinsried, Germany.
2
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
3
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany. Electronic address: uhartl@biochem.mpg.de.
4
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany; Division of Cell Biology, Biomedical Center, Faculty of Medicine, University of Munich, GroƟhaderner Strasse 9, 82152 Martinsried, Germany. Electronic address: neupert@med.uni-muenchen.de.

Abstract

Eukaryotic cells have evolved extensive protein quality-control mechanisms to remove faulty translation products. Here, we show that yeast cells continually produce faulty mitochondrial polypeptides that stall on the ribosome during translation but are imported into the mitochondria. The cytosolic protein Vms1, together with the E3 ligase Ltn1, protects against the mitochondrial toxicity of these proteins and maintains cell viability under respiratory conditions. In the absence of these factors, stalled polypeptides aggregate after import and sequester critical mitochondrial chaperone and translation machinery. Aggregation depends on C-terminal alanyl/threonyl sequences (CAT-tails) that are attached to stalled polypeptides on 60S ribosomes by Rqc2. Vms1 binds to 60S ribosomes at the mitochondrial surface and antagonizes Rqc2, thereby facilitating import, impeding aggregation, and directing aberrant polypeptides to intra-mitochondrial quality control. Vms1 is a key component of a rescue pathway for ribosome-stalled mitochondrial polypeptides that are inaccessible to ubiquitylation due to coupling of translation and translocation.

KEYWORDS:

CAT-tails; Ltn1; Rqc2; Vms1; mitochondria; mitochondrial toxicity; protein aggregation; protein import; ribosome quality control; ribosome stalling

PMID:
29107329
DOI:
10.1016/j.cell.2017.10.002
[Indexed for MEDLINE]

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