Uncoupling Stress-Inducible Phosphorylation of Heat Shock Factor 1 from Its Activation

Mol Cell Biol. 2015 Jul;35(14):2530-40. doi: 10.1128/MCB.00816-14. Epub 2015 May 11.


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 (HSF1Δ∼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, HSF1Δ∼PRD is a potent transactivator of both endogenous targets and a reporter gene, and HSF1Δ∼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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / genetics
  • Blotting, Western
  • Cell Movement / genetics
  • Cells, Cultured
  • DNA / genetics
  • DNA / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Embryo, Mammalian / cytology
  • Fibroblasts / cytology
  • Fibroblasts / metabolism*
  • HeLa Cells
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism
  • Hot Temperature
  • Humans
  • Mice, Knockout
  • Microscopy, Confocal
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism*
  • Phosphorylation
  • Protein Binding / genetics
  • Regulatory Sequences, Nucleic Acid / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Stress, Physiological*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcriptional Activation


  • DNA-Binding Proteins
  • Heat Shock Transcription Factors
  • Heat-Shock Proteins
  • Hsf1 protein, mouse
  • Mutant Proteins
  • Transcription Factors
  • DNA