In situ detection and characterization of DNA polymerase activities in the nucleus of eukaryotic cells.

We have developed a cytoenzymological method for localizing DNA polymerase activities in situ and for studying their responses to various chemical agents or environmental conditions. The incubation mixtures and the stimulatory or inhibitory agents added to these media were defined with reference to in vitro biochemical tests used to detect and to characterize DNA polymerases-alpha or -beta found in eukaryotic cells. This method has already been used to study DNA polymerase activities during cell differentiation or cell senescence. Apart from two exceptions found with lower organisms, the nuclear DNA polymerase activity was always higher under conditions which favoured the in vitro expression of DNA polymerase-beta rather than DNA polymerase-alpha. --In the various cell types studied, the cellular DNA polymerase activities were almost exclusively found in the nuclei. It is hoped that this methodology will be useful for obtaining more complete biochemical data on the intracellular localization of various DNA polymerases.