Ruprecht-Karls-Universität Heidelberg
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Joazeiro0217 - Scientist (f/m) / PhD position
Project no:

Project leader:

Project supervisor:
Joazeiro, Claudio
Application deadline:
15. Aug 2020
Start of PhD project:
1. Sep 2020

Project description:

Ribosome-associated quality control and neurodegeneration
Our earlier work had shown that mutation of a novel E3 ligase, Listerin, causes neurodegeneration in mice (1). Subsequently, we elucidated the function of the yeast Listerin ortholog—yeast Listerin (Ltn1) acts in a protein quality control pathway that targets stalled ribosomes unable to proceed with translational elongation or termination (2).

Ltn1 functions as a component of the ribosome-associated quality control (RQC) complex, along with Rqc1 and Rqc2/Tae2 (NEMF in mammals) subunits (3,4). Cryo-EM structures of this complex have led to a model in which Rqc2 first recognizes the stalled 60S ribosomal subunit and then stabilizes binding of Ltn1, which, in turn, ubiquitylates the aberrant nascent chain for proteasomal degradation (5-7).

In addition, Rqc2 has been found by others to modify stalled nascent chains with a carboxy-terminal, Ala- and Thr-containing extension—the “CAT tail” (7). We subsequently discovered that CAT tails mediate formation of insoluble nascent chain aggregates (8). CAT tail modification and aggregation of nascent chains could be observed under conditions of limiting Ltn1 function, suggesting that inefficient targeting by Ltn1 favors the Rqc2-mediated processes (8). These findings uncover a translational stalling-dependent protein aggregation mechanism that may be relevant to the pathophysiology of neurodegeneration.

The project is to study fundamental mechanisms of RQC function and/or to utilize the available knowledge acquired from yeast and other models to elucidate molecular mechanisms of neurodegeneration in RQC-deficient mice.
(1) Chu, J. et al. A mouse forward genetics screen identifies LISTERIN as an E3 ubiquitin ligase involved in neurodegeneration. Proc Natl Acad Sci U S A 106, 2097-2103 (2009)

(2) Bengtson, M. H. & Joazeiro, C. A. Role of a ribosome-associated E3 ubiquitin ligase in protein quality control. Nature 467, 470-473 (2010).

(3) Brandman, O. et al. A ribosome-bound quality control complex triggers degradation of nascent peptides and signals translation stress. Cell 151, 1042-1054 (2012)

(4) Defenouillere, Q. et al. Cdc48-associated complex bound to 60S particles is required for the clearance of aberrant translation products. Proc. Natl. Acad. Sci. USA 110, 5046-5051 (2013)

(5) Lyumkis, D. et al. Structural basis for translational surveillance by the large ribosomal subunit-associated protein quality control complex. Proc Natl Acad Sci U S A 111, 15981-15986 (2014)

(6) Shao, S., Brown, A., Santhanam, B. & Hegde, R. S. Structure and assembly pathway of the ribosome quality control complex. Mol Cell 57, 433-444 (2015)

(7) Shen, P. S. et al. Protein synthesis. Rqc2p and 60S ribosomal subunits mediate mRNA-independent elongation of nascent chains. Science 347, 75-78 (2015)

(8) Yonashiro, R. et al. The Rqc2/Tae2 subunit of the Ribosome-Associated Quality Control (RQC) complex marks ribosome-stalled nascent polypeptide chains for aggregation. Elife 5, e11794 (2016)
Methods that will be used:
Methods utilized will be among, but not limited, to the following:

• Genetic manipulation of the yeast, S. cerevisiae, including genetic screens
• Genetic manipulation of mice
• Biochemical analyses of yeast strains (immunoblot, immunoprecipitation, sucrose gradient fractionation, etc.)
• Biochemical and immunohistochemical analyses of mouse tissues
• Fluorescence imaging techniques to analyse protein expression and subcellular distribution
• Characterization of motor defects of mutant mice
Cooperation partners:
Personal qualifications:
• M.S. in Biochemistry, Molecular Biology, Neurobiology, or related disciplines
• Excellent previous Academic performance
• Strong analytical and technical skills
• Good English language skills (no German language requirement)
• Problem-solving, proactive attitude
Listerin/Ltn1 E3 ligase, RQC, Protein quality control, Neurodegeneration, ALS