Molecular mechanisms of E3 ubiquitin ligase - E2 ubiquitin-conjugating enzyme pairings

• Applicant: Professor Dr. Marco Trujillo Linke
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 261074271

Ubiquitination (or ubiquitylation) is a central process intricately involved in the regulation of most cellular processes and it is mediated by three enzymes. The E2 ubiquitin conjugating enzymes have largely been neglected because they were considered to be only auxiliary. However, E2s are responsible for receiving ubiquitin from the ubiquitin activating enzyme E1, interacting with the E3 ubiquitin ligase and finally, catalysing the attachment of ubiquitin to the substrate. Therefore, the E2s are at the heart of the ubiquitination pathways and also accountable for the diversity of ubiquitin-mediated processes leading to protein degradation, relocalization or modulation of activity. To date no physiological E2-E3 pair has been reported in plants. The proposed project aims to identify molecular E2-E3 networks that shape ubiquitination. To do so we will use the plant U-box type E3 ubiquitin ligase (PUB)22, a negative regulator of responses to both biotic and abiotic stresses, as well as related ligases. Our results suggest that PUB22-E2 pairs are specified at different layers. Pairing specificities can be imposed by domain composition and also be regulated by cellular signalling. Furthermore, our data indicates that the cellular localization of E2-E3 pairs can be both dictated by the E3, as well as, the E2. In the course of this work we plan to shed light on the determinants of the E2-E3 interaction specificities, regulatory mechanisms and identify the type of ubiquitination mediated by E2-E3 pairs (number of attached moieties and linkage type). A detailed functional analysis will also give insight into the biological roles of selected E2s. In addition, we will generate tools and develop methods that will enable the identification of true E2-E3 pairs and thus also enable the in-depth analysis of E3 ubiquitin ligases.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Peter Beyer