IS HEAT-SHOCK PROTEIN RE-INDUCTION DURING TOLERANCE RELATED TO THE STRESSOR-SPECIFIC INDUCTION OF HEAT-SHOCK PROTEINS

The existence of stressor-specific induction programs of heat shock pr oteins (hsps) leads us to analyze the possible occurrence of a stresso r-specific tolerance induced by either heat shock, arsenite, or cadmiu m. As a measure of this tolerance re-induction of hsps was studied. In this paper, we tested whether the refractory state is either valid fo r each specific hsp (implying independent regulation of every member o f the heat shock protein family) or extends from small subsets of the hsp-family to even larger groups of proteins (indicating a more common denominator in their regulation). (Re-)induction of hsps does not see m to be regulated at the level of each individual hsp since difference s in induced synthesis of hsps between two stressor conditions are not supplemented systematically upon the sequential application of the tw o stressors. The most notable example in this respect is hsp60. A pret reatment with cadmium, which hardly induces synthesis of this hsp, doe s induce a tolerance to (re)-induction by heat shock, which normally i nduces hsp60. This suggests the existence of a more common denominator regulating the coordinate expression of at least some hsps. From our data we conclude that the degree, but not the pattern, of hsp re-induc tion is influenced by the type of stressor used in the pretreatment. T he pattern of hsps induced by a secondary applied stressor still shows most of its stressor-specificity and seems to be independent of any p retreatment. The possible implications of stressor-specificity are dis cussed. (C) 1996 Wiley-Liss, Inc.