The Yeast Hex3·Slx8 Heterodimer Is a Ubiquitin Ligase Stimulated by Substrate Sumoylation
Year: 2007
Type: article
Abstract: 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.
Source: Journal of Biological Chemistry
Institutions: Yale University, William & Mary
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1490806999