Heat-induced Alterations in DNA Polymerase Activity of HeLa Cells and of Isolated Nuclei. Relation to Cell Survival

Abstract

The activity of DNA polymerase .alpha. and .beta. was assayed in heated HeLa S3 cells as well as in nuclei isolated from these cells. The enzyme activity as measured in cells and in nuclei was compared with the extent of cell survival after the different hyperthermic doses. Although the activity of the cellular DNA polymerases evidently was related to cell survival after single heat doses, no correlation was found when thermotolerant cells were heated. When the activity of the DNA polymerases was determined in nuclei isolated from nonheated and heated cells, more polymerase activity was found in the nuclei of the heated cells. However, the heat sensitivity of DNA polymerase activity was the same for nuclei isolated from control, preheated and thermotolerant cells. Heat protection of polymerase activity by erythritol and sensitization by procaine was found when cells, but not when nuclei, were heated in the presence of these modifiers. Apparently, (the nuclear bound) DNA polymerases are not to be considered as key enzymes in cellular heat sensitivity of HeLa S3 cells.