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The yeast Hex3.Slx8 heterodimer is a ubiquitin ligase stimulated by substrate sumoylation.

http://www.ncbi.nlm.nih.gov/pubmed/17848550

Hex3 and Slx8 are Saccharomyces cerevisiae proteins with important functions in DNA damage control and maintenance of genomic stability. Both proteins have RING domains at their C termini. Such domains are common in ubiquitin and ubiquitin-like protein ligases (E3s), but little was known about the molecular functions of either protein. In this study we identified HEX3 as a high-copy suppressor of a temperature-sensitive small ubiquitin-related modifier (SUMO) protease mutant, ulp1ts, suggesting that it may affect cellular SUMO dynamics. Remarkably, even a complete deletion of ULP1 is strongly suppressed. Hex3 forms a heterodimer with Slx8. We found that the Hex3.Slx8 complex has a robust substrate-specific E3 ubiquitin ligase activity. In this E3 complex, Slx8 appears to bear the core ligase function, with Hex3 strongly enhancing its activity. Notably, SUMO attachment to a substrate stimulates its Hex3.Slx8-dependent ubiquitination, primarily through direct noncovalent interactions between SUMO and Hex3. Our data reveal a novel mechanism of substrate targeting in which sumoylation of a protein can help trigger its subsequent ubiquitination by recruiting a SUMO-binding ubiquitin ligase.

Pubmed ID: 17848550 RIS Download

Mesh terms: Cysteine Endopeptidases | DNA Damage | DNA-Binding Proteins | Gene Deletion | Genomic Instability | Multiprotein Complexes | RING Finger Domains | SUMO-1 Protein | Saccharomyces cerevisiae | Saccharomyces cerevisiae Proteins | Substrate Specificity | Ubiquitin | Ubiquitin-Protein Ligases | Ubiquitination

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Associated grants

  • Agency: NIGMS NIH HHS, Id: GM 046904
  • Agency: NIGMS NIH HHS, Id: GM 053756

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