SUMMARY: Exponential phase cells of the yeast when treated with a non-lethal concentration of hydrogen peroxide (HO 0·2 mM) for 60 min adapted to become resistant to the lethal effects of a higher dose of HO (2 mM). From studies using cycloheximide to inhibit protein synthesis it appears that protein synthesis is required for maximal induction of resistance but that some degree of protection from the lethal effects of peroxide can be acquired in the absence of protein synthesis. Treatment of cells with 50 μg cycloheximide ml alone led to them acquirng some protection from peroxide. Cells subjected to heat shock became more resistant to 2 mM-HO; however, peroxide pretreatment did not confer thermotolerance. L-[S]Methionine labelling of cells subjected to 0·2 mM-HO stress showed that synthesis of at least ten polypeptides was induced by peroxide treatment. Some of these were also induced in cells subjected to heat shock (23 to 37 °C shift) but the synthesis of at least four polypeptides (45,39·5,38 and 24 kDa) was unique to peroxide-stressed cells. Resistance to peroxide was also inducible in an isogenic petite and an isogenic strain with a mutation in the gene, indicating that the adaptive response does not require functional mitochondria.


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