Structure and activation of the RING E3 ubiquitin ligase TRIM72 on the membrane

Abstract

Plasma membrane repair defects cause human muscle and heart diseases. In the early stage of membrane repair, TRIM72/MG53 nucleates vesicles to the damaged site within seconds. Despite the therapeutic potential of TRIM72/MG53, the molecular mechanisms are poorly understood. Here, we present the structure of TRIM72, the first complete model of a TRIM E3 ligase. Structure-guided functional analysis revealed a unique phospholipid recognition mode in which a pair of PRYSPRY domains interacts with negatively charged membranes. In subsequent biochemical analyses, the interaction between TRIM72 and the phosphatidylserine-enriched membrane was shown to be critical for both the oligomeric assembly and ubiquitination activity of TRIM72. We elucidated a higher-order model of TRIM72 assembly on the phospholipid bilayer using cryogenic electron tomography followed by subtomogram averaging. We developed a working molecular model of TRIM72 through integrated structural and biochemical techniques. The findings provide a fundamental basis for the study of TRIM E3 ligases, which share a conserved molecular architecture, and provide further insights into the general regulation of RING-type E3 ligases through the cooperation of multiple domains like those in higher-order assemblies.