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Updated: Apr 19, 2026

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones
Published on: July 25, 2019
S5a/Rpn10, a UIM-protein, as a universal substrate for ubiquitination
Hyoung Tae Kim1, Alfred L Goldberg
1Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
Abstract:
The assay of the activity of ubiquitin (Ub) ligases (E3s) and screens for pharmacological agents that alter their function are a continual challenge for basic investigators as well as in drug development. The assay of different E3s requires distinct detection methods and reagents (e.g., specific antibodies against each E3 or substrate). So, a single assay applicable to many E3s could be very useful. Here, we demonstrate that S5a/Rpn10 binds to the growing polyUb chain formed on a substrate (or on the Ub ligase during autoubiquitination) and then itself becomes extensively ubiquitinated. S5a thus can serve as a universal substrate for ubiquitination. This biochemical property of S5a provides a method for measuring the enzymatic activity of any E3. This approach is valuable when substrates are not known or not available and when multiple ubiquitination reactions are being studied (e.g., in high-throughput screens).
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