Figure 6. Hsf1 phosphorylation accounts for sustained Hsf1 transcriptional activity during heat shock.

(A) Western blot of Hsf1 phosphorylation, indicated by its mobility shift, over time following temperature upshift. (B) The HSE-YFP reporter was measured by flow cytometry in wild type Hsf1 and Hsf1^∆po4 cells over time following upshift to 39°C. Data points are the average of median YFP values for three biological replicates, and error bars are the standard deviation. See Materials and methods for assay and analysis details. The sustained activation attributable to phosphorylation is depicted as the orange segment of the wild type curve. (C) Cartoon schematic of the integrated phosphorylation/chaperone titration model of Hsf1 regulation. Phosphorylation (PO4) increases the transcriptional activity of Hsf1 in a manner uncoupled from the Hsp70 feedback loop.

DOI: http://dx.doi.org/10.7554/eLife.18638.019

Figure 6—figure supplement 1. Inclusion of the role of phosphorylation in the mathematical model of Hsf1 regulation.

(A) Phosphorylation gain (β) is incorporated dynamically according to the kinetics determined experimentally. (B) Simulation of the HSE-YFP reporter over a heat shock time course in wild type Hsf1 and Hsf1^∆po4 cells using a model that includes both the Hsp70 negative feedback loop and uncoupled activation gain control by phosphorylation (see Materials and methods for details.)

DOI: http://dx.doi.org/10.7554/eLife.18638.020