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Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
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Role of E2-RING Interactions in Governing RNF4-Mediated Substrate Ubiquitination
Anthony DiBello1, Ajit B Datta1, Xiangbin Zhang1
1Department of Biophysics and Biophysical Chemistry, The Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA.
Journal of Molecular Biology
|September 29, 2016
Summary
The study reveals how specific E2 enzyme surfaces dictate ubiquitination type. Modifying RAD6B
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Biology
Background:
- The really interesting new gene (RING) E3 ubiquitin ligase family mediates protein ubiquitination, a process crucial for cellular signaling.
- Ubiquitination can involve single ubiquitin molecules or polyubiquitin chains, with distinct modifications leading to different cellular outcomes.
- E2 enzymes are key regulators of ubiquitination type, but the structural features determining their mono- versus polyubiquitinating activity remain largely unknown.
Purpose of the Study:
- To investigate the structural determinants of E2 enzyme activity in governing ubiquitination multiplicity.
- To understand how the interaction between E3 ligase RNF4 and different E2 enzymes (RAD6B and UBCH5B) influences ubiquitination outcomes.
Main Methods:
- Site-directed mutagenesis of the RAD6B E2 enzyme to alter its RING-binding surface.
- In vitro ubiquitination assays using RNF4 E3 ligase with wild-type and mutant RAD6B, as well as UBCH5B.
- Analysis of ubiquitination products, including monoubiquitination and polyubiquitination of polySUMO chains.
- Measurement of E2-E3 binding affinity.
Main Results:
- RNF4 exhibits differential ubiquitination activity with RAD6B (monoubiquitination) and UBCH5B (polyubiquitination).
- Divergent ubiquitination activities are attributed to differences in the RING-binding surface of RAD6B and UBCH5B.
- Mutating the RAD6B RING-binding surface to mimic UBCH5B converted RAD6B into a polyubiquitinating E2 enzyme.
- This functional switch in RAD6B correlated with an increased binding affinity for RNF4.
Conclusions:
- The affinity between E3 ligases and their cognate E2 enzymes is a critical determinant of ubiquitination multiplicity.
- Structural features on the E2 RING-binding surface directly influence E2-E3 interaction strength and subsequent ubiquitination outcomes.
- This work provides insights into the regulation of ubiquitin signaling pathways and potential therapeutic targets.
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