Wss1 is a SUMO-dependent isopeptidase that interacts genetically with the Slx5-Slx8 SUMO-targeted ubiquitin ligase.
Protein sumoylation plays an important but poorly understood role in controlling genome integrity. In Saccharomyces cerevisiae, the Slx5-Slx8 SUMO-targeted Ub ligase appears to be needed to ubiquitinate sumoylated proteins that arise in the absence of the Sgs1 DNA helicase. WSS1, a high-copy-number suppressor of a mutant SUMO, was implicated in this pathway because it shares phenotypes with SLX5-SLX8 mutants, including a wss1Delta sgs1Delta synthetic-fitness defect. Here we show that Wss1, a putative metalloprotease, physically binds SUMO and displays in vitro isopeptidase activity on poly-SUMO chains. Like that of SLX5, overexpression of WSS1 suppresses sgs1Delta slx5Delta lethality and the ulp1ts growth defect. Interestingly, although Wss1 is relatively inactive on ubiquitinated substrates and poly-Ub chains, it efficiently deubiquitinates a Ub-SUMO isopeptide conjugate and a Ub-SUMO fusion protein. Wss1 was further implicated in Ub metabolism on the basis of its physical association with proteasomal subunits. The results suggest that Wss1 is a SUMO-dependent isopeptidase that acts on sumoylated substrates as they undergo proteasomal degradation.
Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA.
Janet R
JR
Mullen
Chi-Fu
CF
Chen
Steven J
SJ
Brill
D019759:Carbon-Nitrogen Lyases; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism
D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; D004265:DNA Helicases; D019759:Carbon-Nitrogen Lyases; C034300:isopeptidase