Ubiquitin Substrates Dramatically Increase Ataxin3 Deubiquitinating Activity: Allosteric crosstalk connects three distinct sites

Abstract

SignificanceUbiquitin signaling networks modulate almost all aspects of eukaryotic biology, and their outputs reflect the dynamic balance between ubiquitin attachment and removal. The latter process is catalyzed by deubiquitinating enzymes (DUBs), which must be carefully regulated to ensure that their activities are applied appropriately. Ataxin3 is a DUB that participates in quality-control pathways that support cellular health; however, the regulation of its activity has remained poorly understood. Here, we show that ataxin3 can be dramatically activated by naturally occurring ubiquitin species, and that this activation involves a previously uncharacterized interplay between three distinct sites on the enzyme. Our improved understanding of ataxin3 regulation provides insights into allosteric mechanisms that may prove applicable to other enzymes in the ubiquitin universe.

Capturing the Conformational Ensemble of the Mixed Folded Polyglutamine Protein Ataxin-3

“…Furthermore, our study makes it possible to determine accurately previously unknown interaction surfaces within the C-terminal tail and to characterize interactions occurring at multiple sites, for example involving simultaneously the Josephin domain and the C-terminal tail, as might be the case for polyubi-quitin chains. Rao et al (2020), for instance, have recently proposed a model for allosteric activation of ataxin-3. Ubiquitin conjugates increase markedly the activity of ataxin-3 by bridging together site 2 on the Josephin domain with the UIMs in the C-terminal tail, as shown by fluorescence resonance energy transfer experiments.…”

Spinocerebellar Ataxia Type 3 Pathophysiology—Implications for Translational Research and Clinical Studies

“…Mutations in both UIMs only, allow ATXN3 to also trim shorter ubiquitin chains, which potentially results in decreased substrate degradation [20,25]. Interestingly, a study from Rao et al in 2020 showed that ATXN3s DUB activity can be dramatically activated by naturally occurring ubiquitin species [26].…”