VARIATIONS OF DNA POLYMERASE ALPHA AND DNA POLYMERASE BETA DURING PROLONGED STIMULATION OF HUMAN LYMPHOCYTES

In the present work the levels of the DNA polymerases ? and ? were measured in phytohemagglutinin stimulated lymphocytes during a 12 day period; both enzymes are present at detectable levels at time zero. A peak of DNA polymerase ? was observed corresponding to the peak of DNA synthesis rate (between the fourth and fifth day) and increasing by a factor of approximately 20 times the zero time value; subsequently, the level of DNA polymerase ? decreased in parallel with the DNA synthesis rate. The DNA polymerase ? also increased in ratio to the peak of the DNA synthesis rate, but reached its maximum later between the eighth and tenth days of incubation. The capacity of stimulated lymphocytes to perform repair synthesis following UV damage was measured in the same cells used for the enzyme activity determinations; this capacity also shows two maxima: a first one correlated with the peak in DNA replication rate, and a second one correlated with the peak of DNA polymerase ?. These data suggest a certain tendency to the specialization of functions in human cell DNA polymerases; the ? enzyme seems mainly correlated with DNA replication, whereas the ? enzyme seems more correlated with the ability of the cell to perform repair type synthesis.