Medical Sciences, Indiana University School of Medicine, Bloomington, IN, USA.
Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN, USA.
FEBS J. 2022 Jul;289(13):3876-3893. doi: 10.1111/febs.16375. Epub 2022 Feb 11.
The heat stress response activates the transcription factor heat shock factor 1 (HSF1), which subsequently upregulates heat shock proteins to maintain the integrity of the proteome. HSF1 activation requires nuclear localization, trimerization, DNA binding, phosphorylation and gene transactivation. Phosphorylation at S326 is an important regulator of HSF1 transcriptional activity. Phosphorylation at S326 is mediated by AKT1, mTOR, p38, MEK1 and DYRK2. Here, we observed activation of HSF1 by AKT1 independently of mTOR. AKT2 also phosphorylated S326 of HSF1 but showed weak ability to activate HSF1. Similarly, mTOR, p38, MEK1 and DYRK2 all phosphorylated S326 but AKT1 was the most potent activator. Mass spectrometry showed that AKT1 also phosphorylated HSF1 at T142, S230 and T527 in addition to S326, whereas the other kinases did not. Subsequent investigation revealed that phosphorylation at T142 is necessary for HSF1 trimerization and that S230, S326 and T527 are required for HSF1 gene transactivation and recruitment of TFIIB and CDK9. Interestingly, T527 as a phosphorylated residue has not been previously shown and sits in the transactivation domain, further implying a role for this site in HSF1 gene transactivation. This study suggests that HSF1 hyperphosphorylation is targeted and these specific residues have direct function in regulating HSF1 transcriptional activity.
热应激反应激活转录因子热休克因子 1（HSF1），随后上调热休克蛋白以维持蛋白质组的完整性。HSF1 的激活需要核定位、三聚化、DNA 结合、磷酸化和基因转录激活。S326 的磷酸化是 HSF1 转录活性的重要调节因子。S326 的磷酸化由 AKT1、mTOR、p38、MEK1 和 DYRK2 介导。在这里，我们观察到 AKT1 独立于 mTOR 激活 HSF1。AKT2 也磷酸化 HSF1 的 S326，但激活 HSF1 的能力较弱。同样，mTOR、p38、MEK1 和 DYRK2 都磷酸化 S326，但 AKT1 是最有效的激活剂。质谱分析表明，AKT1 还在 S326 以外的 T142、S230 和 T527 处磷酸化 HSF1，而其他激酶则没有。进一步的研究表明，T142 的磷酸化对于 HSF1 的三聚化是必需的，而 S230、S326 和 T527 对于 HSF1 的基因转录激活和 TFIIB 和 CDK9 的募集是必需的。有趣的是，T527 作为一个磷酸化残基以前没有被发现，它位于转录激活域内，进一步暗示该位点在 HSF1 基因转录激活中起作用。本研究表明，HSF1 的过度磷酸化是有针对性的，这些特定残基在调节 HSF1 转录活性方面具有直接功能。
