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Hypoxia abolishes transience of the heat-shock response in the methylotrophic yeast Hansenula polymorpha

Emanuela Guerra^1,

¹ Laboratorio di Genetica Microbica, DiSA, Università Politecnica delle Marche, 60131 Ancona, Italy
² Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK

Correspondence
Peter Piper
peter.piper{at}sheffield.ac.uk

The heat-shock response is conserved amongst practically all organisms. Almost invariably, the massive heat-shock protein (Hsp) synthesis that it induces is subsequently down-regulated, making this a transient, not a sustained, stress response. This study investigated whether the heat-shock response displays any unusual features in the methylotrophic yeast Hansenula polymorpha, since this organism exhibits the highest growth temperature (49–50 °C) identified to date for any yeast and grows at 47 °C without either thermal death or detriment to final biomass yield. Maximal levels of Hsp induction were observed with a temperature upshift of H. polymorpha from 30 °C to 47–49 °C. This heat shock induces a prolonged growth arrest, heat-shock protein synthesis being down-regulated long before growth resumes at such high temperatures. A 30 °C to 49 °C heat shock also induced thermotolerance, although H. polymorpha cells in balanced growth at 49 °C were intrinsically thermotolerant. Unexpectedly, the normal transience of the H. polymorpha heat-shock response was suppressed completely by imposing the additional stress of hypoxia at the time of the 30 °C to 49 °C temperature upshift. Hypoxia abolishing the transience of the heat-shock response appears to operate at the level of Hsp gene transcription, since the heat-induced Hsp70 mRNA was transiently induced in a heat-shocked normoxic culture but displayed sustained induction in a culture deprived of oxygen at the time of temperature upshift.

Present address: Unit of Cancer Pathology, University ‘G. D’ Annunzio', Via Colle dell' Ara, 66013 Chieti Scalo, Italy.

This article has been cited by other articles:

				A. W. Truman, S. H. Millson, J. M. Nuttall, M. Mollapour, C. Prodromou, and P. W. Piper In the Yeast Heat Shock Response, Hsf1-Directed Induction of Hsp90 Facilitates the Activation of the Slt2 (Mpk1) Mitogen-Activated Protein Kinase Required for Cell Integrity Eukaryot. Cell, April 1, 2007; 6(4): 744 - 752. [Abstract] [Full Text] [PDF]