Abstract
All organisms have evolved mechanisms that protect them against environmental stress. The major fungal pathogen of humans, Candida albicans, has evolved robust stress responses that protect it against human immune defences and promote its pathogenicity. However, C. albicans is unlikely to be exposed to heat shock as it is obligatorily associated with warm-blooded animals. Therefore, we examined the role of the heat shock transcription factor (Hsf1) in this pathogen. We show that C. albicans expresses an evolutionarily conserved Hsf1 (orf19.4775) that is phosphorylated in response to heat shock, induces transcription via the heat shock element (HSE), contributes to the global transcriptional response to heat shock, and is essential for viability. Why has Hsf1 been conserved in this obligate animal saprophyte? We reasoned that Hsf1 might contribute to medically relevant stress responses. However, this is not the case, as an Hsf1-specific HSE-lacZ reporter is not activated by oxidative, osmotic, weak acid or pH stress. Rather, Hsf1 is required for the expression of essential chaperones in the absence of heat shock (e.g. Hsp104, Hsp90, Hsp70). Furthermore, Hsf1 regulates the expression of HSE-containing genes in response to growth temperature in C. albicans. Therefore, the main role of Hsf1 in this pathogen might be the homeostatic modulation of chaperone levels in response to growth temperature, rather than the activation of acute responses to sudden thermal transitions.
Highlights
Organisms exist in constantly changing and complex environments where they are subject to wide-ranging perturbations that are often perceived as stresses
C. albicans is unlikely to be exposed to heat shock as it is obligatorily associated with warmblooded animals
We show that C. albicans expresses an evolutionarily conserved Hsf1 that is phosphorylated in response to heat shock, induces transcription via the heat shock element (HSE), contributes to the global transcriptional response to heat shock, and is essential for viability
Summary
Organisms exist in constantly changing and complex environments where they are subject to wide-ranging perturbations that are often perceived as stresses. The heat shock response protects cells against sudden changes in temperature by inducing the expression of heat shock proteins (HSPs) that protect proteins during thermal stress and facilitate the repair or degradation of damaged proteins (Panaretou and Zhai, 2008). This response is highly conserved across the eukaryotic kingdom from the fungi to plants and animals. Functional homologues of Hsf are conserved in metazoans (Morimoto, 1998; Pirkkala et al, 2001; Voellmy, 2004) These homologues execute equivalent roles to ScHsf, but they can be activated by stress through alternative post-translational mechanisms (Hietakangas et al, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
