Yeast self-perpetuating protein aggregates (yeast prions) provide a framework to investigate the interaction of misfolded proteins with the protein quality control machinery. The major component of this system that facilitates propagation of all known yeast amyloid prions is the Hsp104 chaperone that catalyzes fibril fragmentation. Overproduction of Hsp104 cures some yeast prions via a fragmentation-independent mechanism. Importantly, major cytosolic chaperones of the Hsp40 group, Sis1 and Ydj1, oppositely affect yeast prion propagation, and are capable of stimulating different activities of Hsp104. In this work, we developed a quantitative method to investigate the Hsp40 binding to amyloid aggregates. We demonstrate that Sis1 binds fibrils formed by the Sup35NM protein with higher affinity compared to Ydj1. Moreover, the interaction of Sis1 with the fibrils formed by the other yeast prion protein, Rnq1, is orders of magnitude weaker. We show that the deletion of the dimerization domain of Sis1 (crucial for the curing of [PSI⁺] by excess Hsp104) decreases its affinity to both Sup35NM and Rnq1 fibrils. Taken together, these results suggest that tight binding of Hsp40 to the amyloid fibrils is likely to enhance aggregate malpartition instead of fibril fragmentation.

中文翻译：

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伴侣蛋白与淀粉样蛋白聚集体结合的定量评估确定了Hsp40与酵母病毒原纤维相互作用的特异性。

酵母自身永存的蛋白质聚集体（酵母病毒）提供了一个框架，可研究错误折叠的蛋白质与蛋白质质量控​​制机制之间的相互作用。该系统可促进所有已知酵母淀粉样蛋白propagation的繁殖，其主要成分是催化原纤维断裂的Hsp104分子伴侣。Hsp104的过量生产通过不依赖片段化的机制治愈了一些酵母病毒。重要的是，Hsp40组的主要胞质分子伴侣Sis1和Ydj1相反地影响酵母病毒的繁殖，并能够刺激Hsp104的不同活性。在这项工作中，我们开发了一种定量方法来研究Hsp40与淀粉样蛋白聚集体的结合。我们证明，Sis1结合由Sup35NM蛋白形成的原纤维，与Ydj1相比具有更高的亲和力。此外，Sis1与其他酵母蛋白Rnq1形成的原纤维之间的相互作用减弱了几个数量级。我们显示，Sis1二聚结构域的缺失（对于[PSI ⁺ ]通过过量的Hsp104）降低了它对Sup35NM和Rnq1原纤维的亲和力。综上所述，这些结果表明Hsp40与淀粉样蛋白原纤维的紧密结合很可能会增强聚集的分配不良而不是原纤维断裂。