Dynamics of auxin sensing by an SCF-E3 type ubiquitin ligase and its degradation targets
Final Report Abstract
With this work we sought to contribute toward the overall understanding of mechanisms controlling protein stability, and ultimately, to how intracellular signals like auxin are perceived and processed in plants. We combined quantitative in vitro and in vivo tools to reveal underlying consequences of discriminatory auxin perception. Specifically, we gave unique insights into the evolution, dynamics and the wiring of the auxin response system. Our results illustrate how evolution of primary protein structure may be amplified through interaction with small molecules and protein complexes downstream. In our studies we found the consequence of differential TIR1-AUX/IAA interactions is distinct degradation kinetics of transcriptional repressors central to auxin response. Thus, we offered a model strategy for interpretation of small molecule concentrations into fine-tuned control of gene expression. Additionally, by carrying out a structural proteomics approach combined with biochemistry, we showed AUX/IAAs adopt a highly dynamic conformational fold. Although AUX/IAAs might exhibit conformational heterogeneity, we observed that, while in solution, AUX/IAAs maintain unprecedented flexibility that seems to favor recruitment by the SCFTIR1. We contributed to solving a long standing question. We found AUX/IAAs are secured on the solenoid fold of TIR1 not only via the degron, but identified intrinsically disorder regions (IDRs) upstream of the degron, as well as their folded PB1-C-terminal domain which offer alternative contacts with TIR1. Thus, we have captured for the first time a highly flexible ubiquitylation target being engaged by an SCF-type E3 ubiquitin ligase, which at the same time, constitutes a phytohormone receptor. Our strategy offers an opportunity to visualize how IDR-driven allostery might influence a complex signaling network.
Publications
- (2015) Solution structure of the PsIAA4 oligomerization domain reveals interaction modes for transcription factors in early auxin response. Proc Natl Acad Sci USA 112(19):6230-5
Dinesh DC, Kovermann M, Gopalswamy M, Hellmuth A, Calderón Villalobos LI, Lilie H, Balbach J, Abel S
(See online at https://doi.org/10.1073/pnas.1424077112) - (2016) Radioligand Binding Assays for Determining Dissociation Constants of Phytohormone Receptors. Methods Mol Biol 1450:23-34
Hellmuth A, Calderón Villalobos LI
(See online at https://doi.org/10.1007/978-1-4939-3759-2_3) - (2016) Structural Biology of Nuclear Auxin Action. Trends Plant Sci 21(4):302-16
Dinesh DC, Calderón Villalobos LIA, Abel S
(See online at https://doi.org/10.1016/j.tplants.2015.10.019) - (2017) Variation in auxin sensing guides AUX/IAA transcriptional repressor ubiquitylation and destruction. Nat Comms 7;8:15706
Winkler M, Niemeyer M, Hellmuth A, Janitza P, Christ G, Samodelov S, Wilde V, Majovsky P, Trujillo M, Zurbriggen M, Hoehenwarter W, Quint M, Calderón Villalobos LIA
(See online at https://doi.org/10.1038/ncomms15706) - (2019) Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin coreceptor assemblies
Niemeyer M, Moreno Castillo E, Ihling C, Iacobucci C, Wilde V, Hellmuth A, Hoehenwarter W, Samodelov SL, Zurbriggen M, Kastritis P, Sinz A, Calderón Villalobos LIA
(See online at https://doi.org/10.1101/787770)
