Pleiotropic effects of Ubp6 loss on drug sensitivities and yeast prion are due to depletion of the free ubiquitin pool
Pleiotropic effects of Ubp6 loss on drug sensitivities and yeast prion are due to depletion of the free ubiquitin pool
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DOI：
10.1074/jbc.m310283200
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发表时间：
2003-12-26
影响因子：
4.8
通讯作者：
Wilkinson, KD
中科院分区：
文献类型：
--
作者：
Chernova, TA;Allen, KD;Wilkinson, KD
编码酵母去泛素化酶Ubp 6同源物的小鼠Usp 14基因突变导致共济失调。在这里，我们表明，在酿酒酵母中的UBP 6基因的缺失引起的敏感性，广泛的有毒化合物和拮抗表型表达和从头诱导的酵母朊病毒[PSI+]，一个功能缺陷的自我永存异构体的翻译终止因子Sup 35。相反，泛素（Ub）的过表达增加野生型细胞中[PSI+]的表型表达和诱导，并抑制所有测试的ubp 6Delta缺陷，表明它们主要是由于细胞Ub水平的耗尽。一些证据表明Ubp 6在蛋白酶体上起作用。首先，Ubp 6 δ细胞中的Ub水平可以通过蛋白酶体抑制剂部分恢复，这表明Ubp 6的缺失通过增加Ub的蛋白酶体依赖性降解来降低Ub水平。其次，荧光显微镜分析表明，Ubp 6-GFP融合蛋白定位于酵母细胞的细胞核，因为大多数蛋白酶体。第三，N-末端Ub样结构域，虽然它不是Ubp 6的核定位所必需的，但将Ubp 6靶向蛋白酶体，并且不能在功能上被Ub取代。Ubp 6的人类直系同源物USP 14可能在高等真核生物中发挥类似的作用，因为它完全补偿了ubp 6Delta缺陷并与酵母蛋白酶体结合。这些数据将Ub系统与朊病毒的表达和繁殖联系起来，并对其他神经元包涵体疾病具有广泛的意义。
Mutation of the mouse Usp14 gene, encoding the homolog of yeast deubiquitinating enzyme Ubp6, causes ataxia. Here we show that deletion of the UBP6 gene in Saccharomyces cerevisiae causes sensitivity to a broad range of toxic compounds and antagonizes phenotypic expression and de novo induction of the yeast prion [PSI+], a functionally defective self-perpetuating isoform of the translation termination factor Sup35. Conversely, overexpression of ubiquitin (Ub) increases phenotypic expression and induction of [PSI+] in the wild type cells and suppresses all tested ubp6Delta defects, indicating that they are primarily due to depletion of cellular Ub levels. Several lines of evidence suggest that Ubp6 functions on the proteasome. First, Ub levels in the ubp6Delta cells can be partly restored by proteasome inhibitors, suggesting that deletion of Ubp6 decreases Ub levels by increasing proteasome-dependent degradation of Ub. Second, fluorescence microscopy analysis shows that Ubp6-GFP fusion protein is localized to the nucleus of yeast cell, as are most proteasomes. Third, the N-terminal Ub-like domain, although it is not required for nuclear localization of Ubp6, targets Ubp6 to the proteasome and cannot be functionally replaced by Ub. The human ortholog of Ubp6, USP14, probably plays a similar role in higher eukaryotes, since it fully compensates for ubp6Delta defects and binds to the yeast proteasome. These data link the Ub system to prion expression and propagation and have broad implications for other neuronal inclusion body diseases.