Maintenance of protein homeostasis in eukaryotes under normal growth and stress conditions requires the functions of Hsp70 chaperones and associated cochaperones. Here, we investigate an evolutionarily conserved serine phosphorylation that occurs at the site of communication between the nucleotide-binding and substrate-binding domains of Hsp70. Ser151 phosphorylation in yeast Hsp70 (Ssa1) is promoted by cyclin-dependent kinase (Cdk1) during normal growth. Phosphomimetic substitutions at this site (S151D) dramatically downregulate heat shock responses, a result conserved with HSC70 S153 in human cells. Phosphomimetic forms of Ssa1 also fail to relocalize in response to starvation conditions, do not associate in vivo with Hsp40 cochaperones Ydj1 and Sis1, and do not catalyze refolding of denatured proteins in vitro in cooperation with Ydj1 and Hsp104. Despite these negative effects on HSC70/HSP70 function, the S151D phosphomimetic allele promotes survival of heavy metal exposure and suppresses the Sup35-dependent [PSI+ ] prion phenotype, consistent with proposed roles for Ssa1 and Hsp104 in generating self-nucleating seeds of misfolded proteins. Taken together, these results suggest that Cdk1 can downregulate Hsp70 function through phosphorylation of this site, with potential costs to overall chaperone efficiency but also advantages with respect to reduction of metal-induced and prion-dependent protein aggregate production.

中文翻译：

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生长调节的 Hsp70 磷酸化调节应激反应和朊病毒维持。


真核生物在正常生长和应激条件下维持蛋白质稳态需要 Hsp70 伴侣和相关辅助伴侣的功能。在这里，我们研究了进化上保守的丝氨酸磷酸化，该磷酸化发生在 Hsp70 的核苷酸结合域和底物结合域之间的通讯位点。在正常生长过程中，细胞周期蛋白依赖性激酶 (Cdk1) 会促进酵母 Hsp70 (Ssa1) 中 Ser151 的磷酸化。该位点 (S151D) 的拟磷替换可显着下调热休克反应，这一结果在人类细胞中的 HSC70 S153 中是保守的。 Ssa1 的拟磷拟态形式也无法响应饥饿条件而重新定位，在体内不与 Hsp40 共伴侣 Ydj1 和 Sis1 结合，并且在体外不与 Ydj1 和 Hsp104 协同催化变性蛋白的重折叠。尽管对 HSC70/HSP70 功能有这些负面影响，S151D 拟磷等位基因仍能促进重金属暴露的存活并抑制 Sup35 依赖性的 [PSI+] 朊病毒表型，这与 Ssa1 和 Hsp104 在生成错误折叠蛋白的自成核种子中的作用一致。总而言之，这些结果表明 Cdk1 可以通过该位点的磷酸化下调 Hsp70 功能，这可能会降低整体伴侣效率，但在减少金属诱导和朊病毒依赖性蛋白质聚集体产生方面也具有优势。