Studies on poly (adenosine diphosphate-ribose)

The enzyme catalyzing the synthesis of poly (adenosine diphosphate-ribose) with an average of eight repetitions of ADP-ribose was purified 10-fold from rat liver nuclei in 15% yield. The enzyme required DNA, histone, MgCl2, and dithiothreitol for activity. DNA could not be replaced by polyanions such as poly (U), poly (A), poly (C), RNA, polyvinyl sulfate, methyl dextran sulfate, or heparin. The enzyme was as active on native DNA as on heat-denatured DNA and on poly [d (A-T)], but less active on poly(dG)·poly(dC) and on acid-soluble oligodeoxyribonucleotide. Whole histones of calf thymus or of rat liver, lysine-rich histone of calf thymus, and arginine-rich histone were similarly effective in stimulating the reaction. Casein, bovine serum albumin, cytochrome c, and spermidine did not replace lysine-rich histone. CaCl2 or MnCl2 was as effective for the reaction as MgCl2. Dithiothreitol could be replaced by 2-mercaptoethanol and by glutathione. Polyanions, such as RNA, poly(U), poly(C), poly(A), and polyvinyl sulfate inhibited the enzyme activity. The molecular weight of the enzyme was determined to be 78,000 by sucrose density gradient centrifugation.