DIFFERENTIAL RELOCALIZATION OF EACH MEMBER OF HSP70 AND HSP28 FAMILIES DURING CHRONIC HEATING

1. A correlation between preferential synthesis and redistribution of 70- and 28-kDa heat shock proteins (HSP70 and HSP28) and chronic thermotolerance development was investigated. 2. Chronic thermotolerance was observed as biphasic survival curve during heating at 42-degrees-C. 3. The redistribution of newly synthesized heat shock proteins was studied at early stage (phase I: 0-4 h) and late stage (phase II: 4-8 h) of biphasic survival curve. Constitutive and inducible HSP70, and phosphorylated HSP28 were preferentially relocalized in the nucleus during heating at 42-degrees-C for 4 h (phase 1). 4. However, the rates of redistribution of these polypeptides, except unphosphorylated HSP28, markedly decreased when cells were heated continuously (phase 11). 5. These results suggest that rates of redistribution of HSP70 and HSP28 families correlated with chronic thermotolerance development.