A General Strategy for Discovery of Inhibitors and Activators of RING and U-box E3 Ligases with Ubiquitin Variants.

Mads Gabrielsen, Lori Buetow, Mark A Nakasone, Syed Feroj Ahmed, Gary J Sibbet, Brian O Smith, Wei Zhang, Sachdev S Sidhu, Danny T Huang

Molecular cell 2017 Oct 19

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RING and U-box E3 ubiquitin ligases regulate diverse eukaryotic processes and have been implicated in numerous diseases, but targeting these enzymes remains a major challenge. We report the development of three ubiquitin variants (UbVs), each binding selectively to the RING or U-box domain of a distinct E3 ligase: monomeric UBE4B, phosphorylated active CBL, or dimeric XIAP. Structural and biochemical analyses revealed that UbVs specifically inhibited the activity of UBE4B or phosphorylated CBL by blocking the E2∼Ub binding site. Surprisingly, the UbV selective for dimeric XIAP formed a dimer to stimulate E3 activity by stabilizing the closed E2∼Ub conformation. We further verified the inhibitory and stimulatory functions of UbVs in cells. Our work provides a general strategy to inhibit or activate RING/U-box E3 ligases and provides a resource for the research community to modulate these enzymes. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Citation

Mads Gabrielsen, Lori Buetow, Mark A Nakasone, Syed Feroj Ahmed, Gary J Sibbet, Brian O Smith, Wei Zhang, Sachdev S Sidhu, Danny T Huang. A General Strategy for Discovery of Inhibitors and Activators of RING and U-box E3 Ligases with Ubiquitin Variants. Molecular cell. 2017 Oct 19;68(2):456-470.e10