Acetylated HSF1 was detected in lysates of human embryonic kidney 293T cells which were transfected with vectors encoding a Flag-HSF1 fusion and p300 proteins and exposed to various stress conditions (Westerheide SD et al. 2012). No acetylation was found in lysates of unstressed cells. Acetylation of HSF1 may occurs on multiple lysines, such as Lys80 within the DNA binding domain. Mutation of Lys80 disrupted the DNA-binding ability of recombinant HSF1, indicating that the acetylation at Lys80 caused the regulated release of the HSF1 trimers from DNA and thus represents a regulatory step in the attenuation of the heat shock responce (Westerheide SD et al. 2009; Herbomel G et al 2013).