Activation of the Slx5-Slx8 ubiquitin ligase by poly-small ubiquitin-like modifier conjugates.

Protein sumoylation is a regulated process that is important for the health of human and yeast cells. In budding yeast, a subset of sumoylated proteins is targeted for ubiquitination by a conserved heterodimeric ubiquitin (Ub) ligase, Slx5-Slx8, which is needed to suppress the accumulation of high molecular weight small ubiquitin-like ...
modifier (SUMO) conjugates. Structure-function analysis indicates that the Slx5-Slx8 complex contains multiple SUMO-binding domains that are collectively required for in vivo function. To determine the specificity of Slx5-Slx8, we assayed its Ub ligase activity using sumoylated Siz2 as an in vitro substrate. In contrast to unsumoylated or multisumoylated Siz2, substrates containing poly-SUMO conjugates were efficiently ubiquitinated by Slx5-Slx8. Although Siz2 itself was ubiquitinated, the bulk of the Ub was conjugated to SUMO residues. Slx5-Slx8 primarily mono-ubiquitinated the N-terminal SUMO moiety of the chain. These data indicate that the Slx5-Slx8 Ub ligase is stimulated by poly-SUMO conjugates and that it can ubiquitinate a poly-SUMO chain.
Mesh Terms:
DNA-Binding Proteins, Mutation, Proteasome Endopeptidase Complex, Protein Binding, Repressor Proteins, SUMO-1 Protein, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Small Ubiquitin-Related Modifier Proteins, Substrate Specificity, Ubiquitin-Protein Ligases
J. Biol. Chem.
Date: Jul. 18, 2008
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