Degradation signals for ubiquitin system proteolysis in Saccharomyces cerevisiae
Degradation signals for ubiquitin system proteolysis in Saccharomyces cerevisiae
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DOI：
10.1093/emboj/17.10.2759
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发表时间：
1998-05-15
期刊：
影响因子：
11.4
通讯作者：
Kulka, RG
中科院分区：
文献类型：
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作者：
Gilon, T;Chomsky, O;Kulka, RG
不同的泛素偶联(UBC)酶和其他因子的组合构成了泛素系统的辅助途径，每一条途径都泛素化特定的蛋白质子集。有证据表明，靶蛋白的某些序列元件或结构基序是降解信号，标志着它们被泛素系统的特定分支泛素化和随后的降解。我们的目标是设计一种系统地搜索降解信号的方法，并确定它们将蛋白质引导到哪个泛素系统亚途径。我们已经构建了两个基于LacZ或URA3基因的报告基因文库，它们在酿酒酵母中表达具有多种C末端延伸的融合蛋白。从这些克隆中，我们分离出了产生不稳定融合蛋白的克隆，这些融合蛋白在各种UBC突变体中稳定。其中有10个克隆的产物稳定在ubc6、ubc7或ubc6ubc7双突变体中。这些克隆的C末端延伸长度从16到50个氨基酸残基不等，被认为含有降解信号，通过泛素系统的UBC6和/或UBC7亚途径进行降解，其中一些C末端尾部具有相似的序列基序，并且几乎所有这些序列的一个共同特征是高度疏水区域，通常位于球状蛋白内或插入膜中。
Combinations of different ubiquitin-conjugating (Ubc) enzymes and other factors constitute subsidiary pathways of the ubiquitin system, each of which ubiquitinates a specific subset of proteins. There is evidence that certain sequence elements or structural motifs of target proteins are degradation signals which mark them for ubiquitination by a particular branch of the ubiquitin system and for subsequent degradation. Our aim was to devise a way of searching systematically for degradation signals and to determine to which ubiquitin system subpathways they direct the proteins. We have constructed two reporter gene libraries based on the lacZ or URA3 genes which, in Saccharomyces cerevisiae, express fusion proteins with a wide variety of C-terminal extensions. From these, we have isolated clones producing unstable fusion proteins which are stabilized in various ubc mutants. Among these are 10 clones whose products are stabilized in ubc6, ubc7 or ubc6ubc7 double mutants. The C-terminal extensions of these clones, which vary in length from 16 to 50 amino acid residues, are presumed to contain degradation signals channeling proteins for degradation via the UBC6 and/or UBC7 subpathways of the ubiquitin system, Some of these C-terminal tails share similar sequence motifs, and a feature common to almost all of these sequences is a highly hydrophobic region such as is usually located inside globular proteins or inserted into membranes.