Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, S-10691 Stockholm, Sweden.
Mol Biol Cell. 2023 Sep 1;34(10):ar101. doi: 10.1091/mbc.E23-05-0153. Epub 2023 Jul 19.
Heat Shock Factor 1 (Hsf1) in yeast drives the basal transcription of key proteostasis factors and its activity is induced as part of the core heat shock response. Exploring Hsf1 specific functions has been challenging due to the essential nature of the gene and the extensive overlap of target promoters with environmental stress response (ESR) transcription factors Msn2 and Msn4 (Msn2/4). In this study, we constructed a viable ∆ strain by replacing the open reading frame with genes that constitutively express Hsp40, Hsp70, and Hsp90 from Hsf1-independent promoters. Phenotypic analysis showed that the ∆ strain grows slowly, is sensitive to heat as well as protein misfolding and accumulates protein aggregates. Transcriptome analysis revealed that the transcriptional response to protein misfolding induced by azetidine-2-carboxylic acid is fully dependent on Hsf1. In contrast, the ∆ strain responded to heat shock through the ESR. Following HS, Hsf1 and Msn2/4 showed functional compensatory induction with stronger activation of the remaining stress pathway when the other branch was inactivated. Thus, we provide a long-overdue genetic test of the function of Hsf1 in yeast using the novel ∆ construct. Our data highlight that the accumulation of misfolded proteins is uniquely sensed by Hsf1-Hsp70 chaperone titration inducing a highly selective transcriptional stress response.
热休克因子 1（Hsf1）在酵母中驱动关键蛋白质稳态因子的基础转录，其活性作为核心热休克反应的一部分被诱导。由于该基因的本质是必需的，并且与环境应激反应（ESR）转录因子 Msn2 和 Msn4（Msn2/4）的靶启动子有广泛的重叠，因此探索 Hsf1 的特定功能具有挑战性。在这项研究中，我们通过用来自 Hsf1 非依赖性启动子的基因替换开放阅读框来构建可行的 ∆ 菌株，这些基因持续表达 Hsp40、Hsp70 和 Hsp90。表型分析表明，∆ 菌株生长缓慢，对热、蛋白质错误折叠和蛋白质聚集敏感。转录组分析显示，对氮唑羧酸诱导的蛋白质错误折叠的转录反应完全依赖于 Hsf1。相比之下，∆ 菌株通过 ESR 对热休克做出反应。HS 后，Hsf1 和 Msn2/4 显示出功能补偿性诱导，当另一个分支失活时，剩余应激途径的激活更强。因此，我们使用新型的 ∆ 构建体对酵母中 Hsf1 的功能进行了长期以来急需的遗传测试。我们的数据强调，错误折叠蛋白的积累被 Hsf1-Hsp70 伴侣的滴定独特地感知，诱导高度选择性的转录应激反应。
