Uncoupling Stress-Inducible Phosphorylation of Heat Shock Factor 1 from Its Activation
Uncoupling Stress-Inducible Phosphorylation of Heat Shock Factor 1 from Its Activation
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DOI：
10.1128/mcb.00816-14
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发表时间：
2015-07-01
影响因子：
5.3
通讯作者：
Sistonen, Lea
中科院分区：
文献类型：
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作者：
Budzynski, Marek A.;Puustinen, Mikael C.;Sistonen, Lea
在哺乳动物中，应激诱导的编码热休克蛋白的基因的表达受热休克转录因子1（HSF 1）的控制。HSF1的激活是一个多步骤的过程，涉及三聚体，DNA结合和转录活性的获得，这与几个翻译后修饰相一致。应激诱导的HSF1磷酸化或过度磷酸化，主要发生在调节结构域（RD）内，已被认为是HSF驱动转录的必要条件，并广泛用于评估HSF1活化。然而，过度磷酸化对HSF1活性的贡献仍然未知。在这项研究中，我们产生了一个磷酸化缺陷的HSF1突变体（HSF1 Delta类似于PRD），其中RD内的15个已知磷酸化位点被破坏。我们的结果表明RD的磷酸化状态不影响HSF 1的亚细胞定位和DNA结合活性。令人惊讶的是，在应激条件下，类似于PRD的HSF1 Delta是内源性靶标和报告基因两者的有效反式激活因子，并且类似于PRD的HSF1 Delta具有降低的激活阈值。我们的研究结果提供了第一个直接的证据解偶联应激诱导的磷酸化HSF1从其激活，我们建议，磷酸化签名单独是不是一个合适的标记HSF1的活动。
In mammals the stress-inducible expression of genes encoding heat shock proteins is under the control of the heat shock transcription factor 1 (HSF1). Activation of HSF1 is a multistep process, involving trimerization, acquisition of DNA-binding and transcriptional activities, which coincide with several posttranslational modifications. Stress-inducible phosphorylation of HSF1, or hyperphosphorylation, which occurs mainly within the regulatory domain (RD), has been proposed as a requirement for HSF-driven transcription and is widely used for assessing HSF1 activation. Nonetheless, the contribution of hyperphosphorylation to the activity of HSF1 remains unknown. In this study, we generated a phosphorylation-deficient HSF1 mutant (HSF1 Delta similar to PRD), where the 15 known phosphorylation sites within the RD were disrupted. Our results show that the phosphorylation status of the RD does not affect the subcellular localization and DNA-binding activity of HSF1. Surprisingly, under stress conditions, HSF1 Delta similar to PRD is a potent transactivator of both endogenous targets and a reporter gene, and HSF1 Delta similar to PRD has a reduced activation threshold. Our results provide the first direct evidence for uncoupling stress-inducible phosphorylation of HSF1 from its activation, and we propose that the phosphorylation signature alone is not an appropriate marker for HSF1 activity.