Reidy Michael, Sharma Ruchika, Shastry Shankar, Roberts Brittany-Lee, Albino-Flores Ivan, Wickner Sue, Masison Daniel C
Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, United States of America.
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
PLoS Genet. 2014 Oct 16;10(10):e1004720. doi: 10.1371/journal.pgen.1004720. eCollection 2014 Oct.
Hsp100 family chaperones of microorganisms and plants cooperate with the Hsp70/Hsp40/NEF system to resolubilize and reactivate stress-denatured proteins. In yeast this machinery also promotes propagation of prions by fragmenting prion polymers. We previously showed the bacterial Hsp100 machinery cooperates with the yeast Hsp40 Ydj1 to support yeast thermotolerance and with the yeast Hsp40 Sis1 to propagate [PSI+] prions. Here we find these Hsp40s similarly directed specific activities of the yeast Hsp104-based machinery. By assessing the ability of Ydj1-Sis1 hybrid proteins to complement Ydj1 and Sis1 functions we show their C-terminal substrate-binding domains determined distinctions in these and other cellular functions of Ydj1 and Sis1. We find propagation of [URE3] prions was acutely sensitive to alterations in Sis1 activity, while that of [PIN+] prions was less sensitive than [URE3], but more sensitive than [PSI+]. These findings support the ideas that overexpressing Ydj1 cures [URE3] by competing with Sis1 for interaction with the Hsp104-based disaggregation machine, and that different prions rely differently on activity of this machinery, which can explain the various ways they respond to alterations in chaperone function.
微生物和植物的Hsp100家族伴侣蛋白与Hsp70/Hsp40/NEF系统协同作用，使应激变性的蛋白质重新溶解并重新激活。在酵母中，这种机制还通过切割朊病毒聚合物来促进朊病毒的传播。我们之前表明，细菌Hsp100机制与酵母Hsp40 Ydj1协同作用以支持酵母耐热性，并与酵母Hsp40 Sis1协同作用以传播[PSI+]朊病毒。在这里，我们发现这些Hsp40同样指导基于酵母Hsp104的机制的特定活性。通过评估Ydj1-Sis1杂合蛋白补充Ydj1和Sis1功能的能力，我们表明它们的C端底物结合结构域决定了Ydj1和Sis1在这些及其他细胞功能上的差异。我们发现[URE3]朊病毒的传播对Sis1活性的改变极为敏感，而[PIN+]朊病毒的传播比[URE3]敏感性低，但比[PSI+]更敏感。这些发现支持了以下观点：过表达Ydj1通过与Sis1竞争与基于Hsp104的解聚机器的相互作用来治愈[URE3]，并且不同的朊病毒对该机器活性的依赖程度不同，这可以解释它们对伴侣蛋白功能改变的各种反应方式。
