Molecular mechanisms of E3 ubiquitin ligase - E2 ubiquitin-conjugating enzyme pairings
Final Report Abstract
The results and the tools generated throughout the course of this project provide a framework to interrogate in vivo E2–E3 pairing for the study of ubiquitination in plants. For the first time we show the pairing specificities between E2s and E3s under near physiological conditions. Key results include the observation that domains other than the U-box mediate pairing specificity. E3s interact with a defined set of E2s that possess different catalytic properties. For instance the E3 ligase PUB22 interacts with eleven E2s belonging to four different groups. Consequently, PUB22 is able to mediate the generation of different types of ubiquitin chains and thus, of ubiquitin signals that can mediate the degradation of the modified target protein via the proteasome, or trigger its intracellular relocalization. Most importantly, we show that the pairing between E2s and E3s is dynamic and changes in response to the activation of the immune response. Moreover, functional analysis of ubc35 ubc36 mutants shows that they partially mimic pub22 pub23 pub24 enhanced activation of immune responses. The work carried out revealed a multi-tiered and dynamic E2–E3 network in plants. As detailed above, the gained insight has set the stage for further analyses to study how different ubiquitin chains are generated and to elucidate their function in relation to the maintenance of general protein homeostasis.
Publications
- (2017) News from the PUB: An up-date on Plant U-box proteins. Journal of Experimental Botany, 69: 371–384
Marco Trujillo
(See online at https://doi.org/10.1093/jxb/erx411) - (2018) Multi-tiered pairing selectivity between E2 ubiquitin-conjugating enzymes and E3 ligases. Journal of Biological Chemistry
Ilona Turek, Nadine Tischer, Roman Lassig, Marco Trujillo
(See online at https://doi.org/10.1074/jbc.RA118.004226)
