title: Heat shock factor 2 (HSF2) contributes to inducible expression of hsp genes through interplay with HSF1.
abstract: The heat shock response is a defense reaction activated by proteotoxic damage induced by physiological or environmental stress. Cells respond to the proteotoxic damage by elevated expression of heat shock proteins (Hsps) that function as molecular chaperones and maintain the vital homeostasis of protein folds. Heat shock factors (HSFs) are the main transcriptional regulators of the stress-induced expression of hsp genes. Mammalian HSF1 was originally identified as the transcriptional regulator of the heat shock response, whereas HSF2 has not been implicated a role in the stress response. Previously, we and others have demonstrated that HSF1 and HSF2 interact through their trimerization domains, but the functional consequence of this interaction remained unclear. We have now demonstrated on chromatin that both HSF1 and HSF2 were able to bind the hsp70 promoter not only in response to heat shock but also during hemin-induced differentiation of K562 erythroleukemia cells. In both cases an intact HSF1 was required in order to reach maximal levels of promoter occupancy, suggesting that HSF1 influences the DNA binding activity of HSF2. The functional consequence of the HSF1-HSF2 interplay was demonstrated by real-time reverse transcription-PCR analyses, which showed that HSF2 was able to modulate the HSF1-mediated expression of major hsp genes. Our results reveal, contrary to the predominant model, that HSF2 indeed participates in the transcriptional regulation of the heat shock response.
authors.affiliation: Department of Biochemistry, Abo Akademi University, Turku, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Ostling
authors.forename: Johanna K
authors.initials: JK
authors.lastname: Björk
authors.forename: Pia
authors.initials: P
authors.lastname: Roos-Mattjus
authors.forename: Valérie
authors.initials: V
authors.lastname: Mezger
authors.forename: Lea
authors.initials: L
authors.lastname: Sistonen
mesh_terms: D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000502:physiology*; D006427:Hemin / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D020014:K562 Cells; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C070389:HSF2 protein, human; D006427:Hemin; D004247:DNA