Vms1 Relieves a Mitochondrial Import Chokehold Lilian Lamech, Cole M. Haynes  Developmental Cell  Volume 43, Issue 3, Pages 259-260 (November 2017) DOI: 10.1016/j.devcel.2017.10.022 Copyright © 2017 Terms and Conditions

Figure 1 Ribosome Quality Control during Synthesis of Cytosolic and Mitochondrial-Targeted Proteins When stalled ribosomes disassociate, they leave a flawed nascent chain bound to the 60S ribosome subunit. (1) The ribosome quality control complex component, Rqc2, adds alanine and threonine residues (CAT-tail) to help push the nascent chain out of the exit tunnel to expose lysine residues for the E3 ligase, Ltn1, to polyubiquitinate (Poly-Ub). The ATPase, Cdc48, is then recruited to extract the aberrant protein for degradation by proteasomes. (2) Some proteins targeted to mitochondria via a mitochondria-targeting sequence (MTS) are co-translationally imported. In this case, the ribosome interacts with the mitochondrial outer membrane and the TOM complex, and the nascent peptide resides inside of mitochondria. During mitochondrial RQC, Vms1 impairs Rqc2 recruitment to prevent the addition of CAT tails, which are inefficiently processed in mitochondria. (3) In the absence of both Ltn1 and Vms1, CAT-tailed mitochondrial proteins form aggregates within mitochondria, where they severely perturb mitochondrial proteostasis and function. Developmental Cell 2017 43, 259-260DOI: (10.1016/j.devcel.2017.10.022) Copyright © 2017 Terms and Conditions