Poly(ADP-ribose) polymerase from Ehrlich ascites tumor cells. Properties of the purified polymerase.

Poly(ADP-ribose) polymerase from Ehrlich ascites tumor cells, partially purified by chromatography on DNA-agarose, was obtained as a more than 80% homogeneous preparation by isoelectric focusing in a sucrose gradient. The polymerase activity was shown to be associated with the major protein in the preparation. Results obtained by electrophoresis in the presence of sodium dodecyl-sulfate indicated that poly(ADP-ribose) polymerase consists of a polypeptide chain with a molecular weight of 130 000. Ultracentrifugation at non-denaturating conditions indicated that the active enzyme may be an oligomeric form of this polypeptide chain. The isoelectric point of the polymerase was 9.40. The effects of various additions to the assay mixture on the synthesis of poly(ADP-ribose) as well as some kinetic data, are given. It is shown that poly(ADP-ribose) is a highly efficient inhibitor of its own synthesis, and results are presented which suggest that the well-known stimulatory effect of DNA on the synthesis is due to reduction of this inhibitory effect of the product.