Effects of ubiquitin system alterations on the formation and loss of a yeast prion
Effects of ubiquitin system alterations on the formation and loss of a yeast prion
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DOI：
10.1074/jbc.m609597200
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发表时间：
2007-02-02
影响因子：
4.8
通讯作者：
Chernoff, Yury O.
中科院分区：
文献类型：
--
作者：
Allen, Kim D.;Chernova, Tatiana A.;Chernoff, Yury O.
酵母朊病毒[PSI+]是翻译终止因子Sup35的自繁殖淀粉样蛋白生成同种型。伴侣蛋白Hsp104的过量产生导致[PSI+]的损失。在这里，我们证明，这种效果是减少了一个主要的酵母泛素结合酶，Ubc4，或基因编码的泛素回收酶，Ubp6的基因编码的基因的缺失。UBC 4 Delta对[PSI+]损失的影响通过耗尽Hsp70伴侣Ssb而增加，但不受Ubp6耗尽的影响。这表明Ubc4通过与受Ubp6影响的途径相同但不受Ssb影响的途径影响[PSI+]损失。在Rnq1蛋白的存在下，ubc4 Delta也促进[PSI+]的自发从头形成。这种刺激是独立的[PIN+]，朊病毒亚型的Rnq 1。许多尝试未能在酵母提取物中检测到泛素化的Sup35。虽然ubc4 Delta和本研究中使用的泛素系统的其他改变导致了一些Hsps的轻微诱导，但这些变化不足以解释它们对[PSI+]的影响。然而，ubc4 Delta增加了与Sup35结合的Hsp70分子伴侣Ssa的比例，表明错误折叠的Sup35在不存在Ubc4的情况下更丰富或更容易接近分子伴侣。含有大的聚集的Sup35结构的[PSI+]细胞的比例也通过ubc4 Delta增加。我们认为UPS的改变诱导了适应性反应，导致了大的“侵略者”样聚集体的积累，这些聚集体促进了从头朊病毒的产生和从伴侣蛋白治疗中的朊病毒恢复。
The yeast prion [PSI+] is a self-propagating amyloidogenic isoform of the translation termination factor Sup35. Overproduction of the chaperone protein Hsp104 results in loss of [PSI+]. Here we demonstrate that this effect is decreased by deletion of either the gene coding for one of the major yeast ubiquitin-conjugating enzymes, Ubc4, or the gene coding for the ubiquitin-recycling enzyme, Ubp6. The effect of ubc4 Delta on [PSI+] loss was increased by depletion of the Hsp70 chaperone Ssb but was not influenced by depletion of Ubp6. This indicates that Ubc4 affects [PSI+] loss via a pathway that is the same as the one affected by Ubp6 but not by Ssb. In the presence of Rnq1 protein, ubc4 Delta also facilitates spontaneous de novo formation of [PSI+]. This stimulation is independent of [PIN+], the prion isoform of Rnq1. Numerous attempts failed to detect ubiquitinated Sup35 in the yeast extracts. While ubc4 Delta and other alterations of ubiquitin system used in this work cause slight induction of some Hsps, these changes are insufficient to explain their effect on [PSI+]. However, ubc4 Delta increases the proportion of the Hsp70 chaperone Ssa bound to Sup35, suggesting that mis-folded Sup35 is either more abundant or more accessible to the chaperones in the absence of Ubc4. The proportion of [PSI+] cells containing large aggregated Sup35 structures is also increased by ubc4 Delta. We propose that UPS alterations induce an adaptive response, resulting in accumulation of the large "aggresome" like aggregates that promote de novo prion generation and prion recovery from the chaperone treatment.