Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA.
Mol Cell Biol. 2010 Aug;30(15):3737-48. doi: 10.1128/MCB.01649-09. Epub 2010 Jun 1.
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.
蛋白质 SUMO 化在控制基因组完整性方面起着重要但尚未被充分理解的作用。在酿酒酵母中，Slx5-Slx8 SUMO 靶向 Ub 连接酶似乎需要泛素化在没有 Sgs1 DNA 解旋酶的情况下产生的 SUMO 化蛋白。WSS1 是一种突变 SUMO 的高拷贝数抑制剂，因为它与 SLX5-SLX8 突变体具有表型，包括 wss1Delta sgs1Delta 合成适应性缺陷，因此被牵连到该途径中。在这里，我们表明，Wss1 是一种假定的金属蛋白酶，可与 SUMO 物理结合，并在体外对多 SUMO 链表现出异构酶活性。与 SLX5 一样，WSS1 的过表达可抑制 sgs1Delta slx5Delta 致死性和 ulp1ts 生长缺陷。有趣的是，尽管 Wss1 对泛素化底物和多 Ub 链的活性相对较低，但它可有效地去泛素化 Ub-SUMO 异肽轭合物和 Ub-SUMO 融合蛋白。基于其与蛋白酶体亚基的物理关联，Wss1 进一步牵连到 Ub 代谢中。结果表明，Wss1 是一种 SUMO 依赖性异构酶，可在 SUMO 化底物进行蛋白酶体降解时对其发挥作用。
