Structure and function of the yeast listerin (Ltn1) conserved N-terminal domain in binding to stalled 60S ribosomal subunits

Abstract

Significance The listerin (Ltn1) E3 ubiquitin ligase ubiquitylates and promotes degradation of aberrant nascent chains that become stalled on ribosomal 60S subunits. Ltn1-dependent nascent chain ubiquitylation was reconstituted in vitro using extracts of genetically manipulated Neurospora strains. Such extracts, supplemented or not with recombinant factors (such as Ltn1 from Saccharomyces cerevisiae ), represent a new system to study ribosome-associated protein quality control. Utilizing this system, we show that mutations in Ltn1’s conserved N-terminal domain result in defective 60S binding and nascent chain ubiquitylation, without affecting Ltn1’s intrinsic E3 activity. Furthermore, we have solved the crystal structure of Ltn1’s N-terminal domain, which provides detailed information and insights into how Ltn1 interacts with stalled 60S subunits. Our observations shed light on how cells handle protein quality control substrates.