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Updated: Jul 3, 2026

In Vitro SUMOylation Assay to Study SUMO E3 Ligase Activity
Published on: January 29, 2018
SMT3IP1, a nucleolar SUMO-specific protease, deconjugates SUMO-2 from nucleolar and cytoplasmic nucleophosmin
Tamotsu Nishida1, Yoshiji Yamada
1Department of Human Functional Genomics, Life Science Research Center, Mie University, 1577 Kurima-machiya, Tsu 514-8507, Japan. nishida@gene.mie-u.ac.jp
Abstract:
Sumoylation is reversibly regulated by SUMO-specific proteases. We characterized a nucleolar SUMO-specific protease, SMT3IP1, which has a preference for SUMO-2/3. To elucidate SMT3IP1 function, we screened for its interacting proteins that may be its substrates or regulate its activity. By using yeast two-hybrid screening, we identified nucleophosmin (NPM) as an SMT3IP1-binding partner. SMT3IP1 could preferentially remove SUMO-2 from sumoylated NPM. A catalytically inactive SMT3IP1 mutant increased intracellular accumulation of SUMO-2-modified NPM in a dominant-negative manner. Sumoylation of cytoplasmic mutated NPM was markedly elevated in an ARF-dependent manner. Despite the divergence in their localization, ectopic expression of SMT3IP1 could desumoylate a SUMO-2-modified NPM mutant. Additionally, genotoxic drugs caused the dissociation of NPM from nucleolar co-localization with SMT3IP1, but did not affect desumoylation of NPM by SMT3IP1. Our findings suggest that SMT3IP1-mediated desumoylation might control NPM physiological functions at both the nucleolus and other subcellular compartments.
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