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Updated: Jul 19, 2026

In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones
Published on: July 25, 2019
Monoubiquitylation of GGA3 by hVPS18 regulates its ubiquitin-binding ability
Satomi Yogosawa1, Masato Kawasaki, Soichi Wakatsuki
1Department of Neurochemistry, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan.
Abstract:
GGAs (Golgi-localizing, gamma-adaptin ear domain homology, ADP-ribosylation factor (ARF)-binding proteins), constitute a family of monomeric adaptor proteins and are associated with protein trafficking from the trans-Golgi network to endosomes. Here, we show that GGA3 is monoubiquitylated by a RING-H2 type-ubiquitin ligase hVPS18 (human homologue of vacuolar protein sorting 18). By in vitro ubiquitylation assays, we have identified lysine 258 in the GAT domain as a major ubiquitylation site that resides adjacent to the ubiquitin-binding site. The ubiquitylation is abolished by a mutation in either the GAT domain or ubiquitin that disrupts the GAT-ubiquitin interaction, indicating that the ubiquitin binding is a prerequisite for the ubiquitylation. Furthermore, the GAT domain ubiquitylated by hVPS18 no longer binds to ubiquitin, indicating that ubiquitylation negatively regulates the ubiquitin-binding ability of the GAT domain. These results suggest that the ubiquitin binding and ubiquitylation of GGA3-GAT domain are mutually inseparable through a ubiquitin ligase activity of hVPS18.
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