Inhibition of HeLa cell protein synthesis under heat shock conditions in the absence of initiation factor eIF-2α phosphorylation

Subjecting a HeLa cell suspension culture to an increase in incubation temperature (from 37° to 42°C) results in the rapid cessation of polypeptide chain synthesis followed by a gradual increase in the synthesis of a class of polypeptides referred to as the heat-shock proteins. It has been proposed that the initial, rapid shutoff of protein synthesis (<20 min) is due to the phosphorylation of initiation factor eIF-2 in its α subunit, a modification known to result in the inhibition of polypeptide synthesis. Using an in vitro translation system derived from heat-shocked HeLa cells grown in suspension culture, we were unable to find any evidence implicating eIF-2α phosphorylation in the initial shutoff of translation during the heat shock response. These results suggest that the rapid inhibition of protein synthesis observed under heat shock conditions is mediated by a mechanism(s) other than eIF-2α phosphorylation.