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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.

Pubmed ID: 18499666

Authors

  • Mullen JR
  • Brill SJ

Journal

The Journal of biological chemistry

Publication Data

July 18, 2008

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM 071268
  • Agency: NIGMS NIH HHS, Id: R01 GM071268
  • Agency: NIGMS NIH HHS, Id: R01 GM071268-09

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