There are three heat shock transcription factors (HSFs) (HSF-1, -2, and -4) mediating transcriptional regulation of the human heat shock response/ unfolded protein response (HSR/UPR). Is this molecule activators of the heat shock response signaling pathway? There are three heat shock transcription factors (HSFs) (HSF-1, -2, and -4) mediating transcriptional regulation of the human heat shock response/ unfolded protein response (HSR/UPR). Is this molecule toxic to the heat shock response signaling pathway? There are three heat shock transcription factors (HSFs) (HSF-1, -2, and -4) mediating transcriptional regulation of the human heat shock response/ unfolded protein response (HSR/UPR). Is this molecule toxic to the heat shock response signaling pathway?