Heat-induced translational suppression is associated with initiator tRNA degradation in thermotolerant cells

Heat stress induces multiple stress responses, including translational suppression, upregulation of heat shock proteins (HSPs), and RNA degradation. Transient exposure to heat stress also induces thermotolerance. Thermotolerant cells exhibit transient resistance to subsequent stress and reduced translational suppression and apoptotic cell death. Thermotolerance is closely correlated with the upregulation of HSPs. Heat stress induces translational suppression via degradation of the initiator tRNA (iMet). In this study, we investigated the relationship between iMet expression and translational suppression in re-exposed cells and examined how these processes are associated with cell death following re-exposure to heat stress. Translational suppression was closely correlated with iMet expression in re-exposed cells, and the pattern of apoptosis was similar to that of translational activity and iMet expression. The expression patterns of HSP27 and HSP70 showed a weak association with apoptosis. The temporal patterns of translational activity, iMet expression, and apoptosis after the initial heat stress suggest a possible association among these thermotolerant responses.