
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.08.24.608776
preprint
1
Article
Poly-alanine-tailing is a modifier of neurodegeneration caused by Listerin mutation
Hung Hao-Chih
Costas-Insua Carlos http://orcid.org/0000-0003-3446-6899

Holbrook Sarah E.
Stauffer Jennifer E.
Martin Paige B.
Müller Tina A.
Schroeder David G.
Kigoshi-Tansho Yu
Xu Haifei
Rudolf Rüdiger
Cox Gregory A.
Joazeiro Claudio A. P. http://orcid.org/0000-0003-1433-8013

24 8 2024
2024.08.24.608776https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.08.24.608776
nihpp-2024.08.24.608776.pdf
Abstract

The surveillance of translation is critical for the fitness of organisms from bacteria to humans. Ribosome-associated Quality Control (RQC) is a surveillance mechanism that promotes the elimination of truncated polypeptides, byproducts of ribosome stalling during translation. In canonical mammalian RQC, NEMF binds to the large ribosomal subunit and recruits the E3 ubiquitin ligase Listerin, which marks the nascent-chains for proteasomal degradation. NEMF additionally extends the nascent-chain’s C-terminus with poly-alanine (‘Ala-tail’), exposing lysines in the ribosomal exit tunnel for ubiquitination. In an alternative, Listerin-independent RQC pathway, released nascent-chains are targeted by Ala-tail-binding E3 ligases. While mutations in Listerin or in NEMF selectively elicit neurodegeneration in mice and humans, the physiological significance of Ala-tailing and its role in disease have remained unknown. Here, we report the analysis of mice in which NEMF’s Ala-tailing activity was selectively impaired. Whereas the Nemf homozygous mutation did not affect lifespan and only led to mild motor defects, genetic interaction analyses uncovered its synthetic lethal phenotype when combined with the lister neurodegeneration-causing mutation. Conversely, the lister phenotype was markedly improved when Ala-tailing capacity was partially reduced by a heterozygous Nemf mutation. Providing a plausible mechanism for this striking switch from early neuroprotection to subsequent neurotoxicity, we found that RQC substrates that evade degradation form amyloid-like aggregates in an Ala-tail dependent fashion. These findings uncover a critical role for Ala-tailing in mammalian proteostasis, and deepen our molecular understanding of pathophysiological roles of RQC in neurodegeneration.
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