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Real-time Tracking of Complex Ubiquitination Cascades Using a Fluorescent Confocal On-Bead Assay

Real-time Tracking of Complex Ubiquitination Cascades Using a Fluorescent Confocal On-Bead Assay

Joanna Koszela, Nhan T Pham, David Evans, Stefan Mann, Irene Perez-Pi, Steven Shave, Derek F J Ceccarelli, Frank Sicheri, Mike Tyers, Manfred Auer

BMC Biol. 2018 Aug 10;16(1):88.

PMID: 30097011

Abstract:

Background:
The ubiquitin-proteasome system (UPS) controls the stability, localization and/or activity of the proteome. However, the identification and characterization of complex individual ubiquitination cascades and their modulators remains a challenge. Here, we report a broadly applicable, multiplexed, miniaturized on-bead technique for real-time monitoring of various ubiquitination-related enzymatic activities. The assay, termed UPS-confocal fluorescence nanoscanning (UPS-CONA), employs a substrate of interest immobilized on a micro-bead and a fluorescently labeled ubiquitin which, upon enzymatic conjugation to the substrate, is quantitatively detected on the bead periphery by confocal imaging.
Results:
UPS-CONA is suitable for studying individual enzymatic activities, including various E1, E2, and HECT-type E3 enzymes, and for monitoring multi-step reactions within ubiquitination cascades in a single experimental compartment. We demonstrate the power of the UPS-CONA technique by simultaneously following ubiquitin transfer from Ube1 through Ube2L3 to E6AP. We applied this multi-step setup to investigate the selectivity of five ubiquitination inhibitors reportedly targeting different classes of ubiquitination enzymes. Using UPS-CONA, we have identified a new activity of a small molecule E2 inhibitor, BAY 11-7082, and of a HECT E3 inhibitor, heclin, towards the Ube1 enzyme.
Conclusions:
As a sensitive, quantitative, flexible, and reagent-efficient method with a straightforward protocol, UPS-CONA constitutes a powerful tool for interrogation of ubiquitination-related enzymatic pathways and their chemical modulators, and is readily scalable for large experiments.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP890605546	Heclin		890605-54-6	Price

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