A SMALL INFLUENCE OF HSP90 LEVELS ON THE TREHALOSE AND HEAT-SHOCK ELEMENT INDUCTIONS OF THE YEAST HEAT-SHOCK RESPONSE

Heat shock protein (HSP) induction is only one change elicited in yeast by heat shock. Trehalose is also accumulated, while declining intracellular pH stimulates plasma membrane ATPase activity. Recently the trehalose induction was shown to be regulated by levels of HSP70 and, to a lesser extent, HSP104. Another HSP which might contribute to regulation is HSP90, especially as HSP90 forms complexes with heat shock transcription factor and several of the regulatory proteins of eukaryotic cells. This possibility was investigated using isogenic yeast strains with normal, decreased or elevated HSP90. The results show HSP90 levels having a small negative influence over the heat inductions of trehalose and the heat shock element, a minor effect compared with the major regulation exerted by HSP70. © 1993 Academic Press, Inc.