title: Regulation of the ubiquitin ligase Ubr1 during protein quality control
creator: Peters, Niklas
subject: ddc-500
subject: 500 Natural sciences and mathematics
subject: ddc-570
subject: 570 Life sciences
description: Cells control the degradation of aberrant or damaged proteins through ubiquitin ligases. When yeast faces protein folding imbalance, the disordered protein Roq1 binds the ubiquitin ligase Ubr1 as a substrate mimic that profoundly changes Ubr1 activity and substrate specificity from N-degron substrates to misfolded proteins. How Roq1 reprograms Ubr1 is not known on a mechanistic level.  In my PhD thesis I biochemically dissected the underlying principles how Roq1 controls Ubr1 using a defined in vitro system. I could demonstrate that Roq1 governs the ubiquitination of Ubr1 substrates through two cooperating motifs. The Roq1 Nterminus controls N-degron substrate ubiquitination. The Roq1 hydrophobic motif enhances the ubiquitination of endogenous Ubr1 substrates with internal degrons and of misfolded proteins. The N-terminus and hydrophobic motif allow Roq1 to bind Ubr1 heterobivalently to generate avidity for efficient Ubr1 reprograming. Furthermore, I could show that amino acid residues C-terminal of the hydrophobic motif are dispensable for Roq1 function. How does Roq1 regulate Ubr1? Instead of promoting ubiquitin-conjugating enzyme or substrate recruitment, Roq1 enhances the ubiquitin transfer by increasing the efficiency of ubiquitin chain initiation. To understand how Roq1 manipulates Ubr1 on a structural level I determined the cryogenic electron microscopy structure of a Roq1-Ubr1 complex with an overall resolution of 6.3 Ångström, which awaits further optimization.  Overall, I unraveled in my PhD thesis how the small, disordered protein Roq1 comprehensively regulates the complex ubiquitin ligase Ubr1. Given the essential role of ubiquitin ligases in diseases, the Roq1 bipartite mode of action could therefore inspire the design of new therapeutic modulators for other ubiquitin ligases.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/35772/1/PhD%20Thesis%20Niklas%20Peters.pdf
identifier: DOI:10.11588/heidok.00035772
identifier: urn:nbn:de:bsz:16-heidok-357722
identifier:   Peters, Niklas  (2024) Regulation of the ubiquitin ligase Ubr1 during protein quality control.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/35772/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng