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首页> 外文期刊>Nature >Editing of ubiquitin conjugates by an isopeptidase in the 26S proteasome
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Editing of ubiquitin conjugates by an isopeptidase in the 26S proteasome

机译：在26S蛋白酶体中通过异肽酶编辑泛素结合物

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摘要

In eukaryotes, ubiquitin (Ub)-dependent proteolysis is essential for bulk protein turnover as well as diverse processes including cell-cycle control, differentiation, antigen presentation, and the stress response. Generally, multiple ubiquitins are added onto a substrate to form an isopeptide-linked 'polyubiquitin' chain, which targets substrates for degradation by the 26S proteasome. The specificity of Ub-dependent degradation was thought to depend primarily on the selection of targets for ubiquitination, but recently we have reported evidence for a second level of specificity in which (poly)Ub-protein conjugates are partitioned among two fates: degradation of the protein substrate by the 26S proteasome; and disassembly by Ub isopeptidase(s) to regenerate the protein substrate. Potentially, an isopeptidase could influence degradation by 'editing' (poly)Ub-protein conjugates according to the extent of ubiquitination rather than the structure of the ubiquitination target itself. Here we describe a bovine isopeptidase that is well suited to such an editing function because of its unique localization and specificity. This enzyme is an intrinsic subunit of PA700, the 19S regulatory complex of the 26S proteasome. By disassembling the degradation signal from only the distal end of (poly)Ub chains, this isopeptidase can selectively rescue poorly ubiquitinated or slowly degraded Ub-protein conjugates from proteolysis.
机译：在真核生物中，依赖泛素（Ub）的蛋白水解对于大量蛋白质更新以及包括细胞周期控制，分化，抗原呈递和应激反应在内的各种过程至关重要。通常，将多种泛素添加到基质上以形成异肽连接的“聚泛素”链，该链靶向基质以被26S蛋白酶体降解。人们认为，依赖Ub的降解的特异性主要取决于泛素化靶标的选择，但是最近我们报道了第二种特异性水平的证据，其中（poly）Ub蛋白偶联物被划分为两个命运： 26S蛋白酶体的蛋白质底物；然后通过Ub异肽酶进行分解，以再生蛋白质底物。潜在地，异肽酶可能会根据泛素化的程度而不是泛素化靶标本身的结构，通过“编辑”（聚）Ub蛋白结合物来影响降解。在这里，我们描述了一种牛异肽酶，由于其独特的定位和特异性，非常适合这种编辑功能。此酶是26S蛋白酶体的19S调节复合物PA700的固有亚基。通过分解仅来自（poly）Ub链末端的降解信号，该异肽酶可以选择性地从蛋白水解中拯救泛素化程度低或降解缓慢的Ub蛋白结合物。

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