Fig. 2: SIRT1 inhibition reduces the HSF1 protein level and decreases the HSP90AA1 gene expression.

A SIRT1 knockdown decreases the HSP90α protein level in OxPhos-dependent DLBCL cell lines. B SIRT1 knockdown decreases the HSF1 protein level and impairs the HSP90AA1 gene expression in cells in normal conditions (-HS) and after heat shock (+HS, 42 °C, 2 h). C Inhibition of SIRT1 with tenovin-6 (ten6) reduces the HSF1 protein level and impairs expression of the HSP90AA1 gene in cells in normal conditions (-HS) and after heat shock (+HS). Cells were incubated with 4 µM tenovin 6 (ten6) or vehicle (DMSO) overnight and then lysed. Heat shock was induced by 2 h incubation at 42 °C. Protein extracts and RNA were used for western blots and RQ-PCR analyses. D SIRT1 activator, SRT-2183, increases HSF1 protein level and HSP90AA1 gene expression in OxPhos-dependent DLBCL cell lines. Cells were incubated with 1 µM SRT-2183 or DMSO for 24 h. Heat shock was induced as described above. In A, B, C and D, representative immunoblots from 3 independent experiments are shown. GAPDH was used as a loading control. Values beneath the blots indicate densitometric bands intensities, in which HSF1 level in controls (scr or ctr) was assigned the value 100%. RQ-PCR graphs in B, C and D represent an average of three independent experiments ± SDs. **** for p < 0.0001, ** for p < 0.01 and * for p < 0.05. The statistical comparisons were performed with t test.