In vitro activity: HSF1A is a cell-permeable and small-molecule activator of heat shock transcription factor 1 (HSF1). HSF1A protects cells from stress-induced apoptosis, binds TRiC subunits in vivo and in vitro, and inhibits TRiC activity without perturbation of ATP hydrolysis. Genetic inactivation or depletion of the TRiC complex results in human HSF1 activation, and HSF1A inhibits the direct interaction between purified TRiC and HSF1 in vitro. Heat shock transcription factor 1 (HSF1) is an evolutionarily conserved transcription factor that protects cells from protein-misfolding-induced stress and apoptosis.

Kinase Assay: Protein extracts are generated from mammalian, yeast and E. coli cultures using biotin-binding buffer (20 mM HEPES, 5 mM MgCl2, 1 mM EDTA, 100 mM KCl, 0.03% NP-40) supplemented with 1% Trition-X100 and protease inhibitors. Approximately 0.5 mg of protein extract is incubated with 100 μM HSF1A-Biotin for 4 h at 4°C and HSF1A-Biotin associated proteins captured by with NeutrAvidin Agarose Resin. After washing in biotin binding buffer proteins are eluted using 50 μL biotin elution buffer (100 mM Tris, 150 mM NaCl, 0.1 mM EDTA, 2 mM D-biotin), resolved on a 4-20% SDS-PAGE, and immunoblotted. For purified TRiC and Hsp70 analyses, 5 nM protein is incubated in biotin-binding buffer+0.5% Triton X-100 with 100 μM biotin or 100 μM HSF1A-Biotin for 4 h at 4°C and captured with NeutrAvidin Resin. For NiNTA purified yeast Tcp1, different concentrations of Tcp1 0.5 μM, 1 mM, 2 mM, 3 mM and 4 mM in 25 mM Hepes pH 7.5, 150 mM NaCl are incubated with 0.5 μM Biotin or HSF1A-Biotin for 4 h at 4°C and captured with NeutrAvidin Resin.

Cell Assay: HSF1A protects cells from stress-induced apoptosis, binds TRiC subunits and inhibits TRiC activity without perturbation of ATP hydrolysis. Genetic inactivation or depletion of the TRiC complex results in human HSF1 activation and HSF1A inhibits the direct interaction between purified TRiC and HSF1 in vitro. Moreover, fluorescence anisotropy experiments using FITC coupled to HSF1A demonstrates that HSF1A-FITC binds to a purified Tcp1 subunit of TRiC with an affinity of approximately 600 nM. This is validated qualitatively via titration of purified Tcp1 into binding reactions containing 500 nM Biotin or HSF1A-Biotin.Quantification by counting the number of cell containing aggregates as a function of the total number of cells reveals that at HSF1A concentrations as low as 2 μM, a reduced number of aggregate-containing cells are observed. The fraction of cells containing aggregates continued to decrease in a dose-dependent manner such that pretreatment with 12 μM HSF1A resulta in ~20% of the cells exhibiting aggregates visible by fluorescence microscopy. PC12 cells seeded into a 96-well plate (5×104 cells/well) are treated with increasing concentrations of HSF1A (2, 4, 8 and 12 μM) for 15 h, at which time httQ74-GFP expression is stimulated by incubation in the presence of 1 μg/mL Doxycycline for 5 d. Cell viability is assessed via the XTT viability assay