THE YEAST POLYUBIQUITIN GENE IS ESSENTIAL FOR RESISTANCE TO HIGH-TEMPERATURES, STARVATION, AND OTHER STRESSES
THE YEAST POLYUBIQUITIN GENE IS ESSENTIAL FOR RESISTANCE TO HIGH-TEMPERATURES, STARVATION, AND OTHER STRESSES
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DOI：
10.1016/0092-8674(87)90711-2
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发表时间：
1987-03-27
期刊：
影响因子：
64.5
通讯作者：
VARSHAVSKY, A
中科院分区：
文献类型：
--
作者：
FINLEY, D;OZKAYNAK, E;VARSHAVSKY, A
真核生物中泛素与细胞内蛋白质的结合介导了它们的选择性降解。在酿酒酵母中，已经描述了四个不同的泛素编码基因座。UBI 1、UBI 2和UBI 3各自编码其中泛素与不相关序列融合的杂合蛋白。第四个基因，UBI 4，包含5个泛素编码元件，以头对尾的方式排列，因此编码多聚泛素前体蛋白。在体外构建了一个精确的、以寡核苷酸为指导的UBI 4缺失，并在酵母基因组中取代了野生型等位基因。泛素4缺失突变体作为营养细胞是有活力的，以野生型速率生长，并且在指数生长条件下含有野生型水平的游离泛素。然而，尽管ubi/4UBI 4二倍体可以形成四个最初有活力的孢子，但其中的两个ubi 4孢子非常迅速地丧失活力，显然是酵母中的一种新表型。此外，ubi 4/ubi 4二倍体是孢子形成缺陷的。Ubi 4突变体也对高温、饥饿和氨基酸类似物过敏。这三种条件虽然性质不同，但都已知会诱导应激蛋白。UBI 4基因的表达类似地由热应激或饥饿诱导。这些结果表明，UBI 4是细胞抵抗应激所必需的，并且泛素是应激反应系统的重要组成部分。
Conjugation of ubiquitin to intracellular proteins mediates their selective degradation in eukaryotes. In in yeast Saccharomyces cerevisiae, four distinct ubiquitin-coding loci have been described. UBI1, UBI2, and UBI3 each encode hybrid proteins in which ubiquitin is fused to unrelated sequences. The fourth gene, UBI4, contains five ubiquitin-coding elements in a head-to-tail arrangement, and thus encodes a polyubiquitin precursor protein. A precise, oligonucleotide-directed deletion of UBI4 was constructed in vitro and substituted in the yeast genome in place of the wild-type allele. ubi4 deletion mutants are viable as vegetative cells, grow at wild-type rates, and contain wild-type levels of free ubiquitin under exponential growth conditions. However, although ubi/4UBI4 diploids can form four initially viable spores, the two ubi4 spores within the ascus lose viability extremely rapidly, apparently a novel phenotype in yeast. Furthermore, ubi4/ubi4 diploids are sporulation-defective. ubi4 mutants are also hypersensitive to high temperatures, starvation, and amino acid analogs. These three conditions, while diverse in nature, are all known to induce stress proteins. Expression of the UBI4 gene is similarly induced by either heat stress or starvation. These results indicate that UBI4 is specifically required for the resistance of cells to stress, and that ubiquitin is an essential component of the stress response system.