DNA-dependent DNA polymerase activities from Paramecia macronuclei

Abstract

Three DNA-dependent DNA polymerase activities, A, B and C, have been detected from the macronucleus of Paramecium. The enzymes were separated and partially purified by DEAE-cellulose and phosphocellulose chromatography. These three enzymes can be further distinguished from each other by the effect of KCl, araCTP and different DNA templates on their activities. All three enzymes have the same molecular weight (90 000–110 000), are dependent on Mg²⁺ and added DNA template and are inhibited by sodium pyrophosphate.

The relative amounts of the three enzyme activities vary with the growth stage of the Paramecia from which they are isolated. In balanced growth, three polymerase activities (A, B and C) are observed, whereas in late log or stationary phase polymerase C is absent, while the level of polymerase B decreases by a larger factor than polymerase A. These results have been related to the possible functional roles of the three activities and their relationship to activities in other organisms studied is discussed.