DNA polymerase activity associated with endogenous template: release by ribonuclease treatment

A ribonuclease-sensitive DNA polymerase, which uses an endogenous template, is detectable in the 39,000 g supernatant of a rat thymus homogenate, and appears as a single peak of activity in the void volume after Sephadex G 150 or G 200 gel filtration chromatography. Native and "activated" DNA-dependent DNA polymerase activities coincide with the endogenous-templated polymerase activity. Treatment of the thymus extract with ribonuclease(s) prior to gel filtration chromatography yields two other peaks of activity in addition to the void volume peak. The appearance of the two lower molecular weight peaks of activity is accompanied by a concomitant decrease in the endogenous-templated activity. The effect of ribonuclease is specific and cannot be reproduced by a similar deoxyribonuclease treatment.