Abstract
Publisher Summary This chapter provides an overview of poly(ADP-ribosyl)ation. The formation of poly(ADP-ribose) by chromatin enzymes is actually initiated by ADP-ribosylation on chromatin proteins. The ADP-ribosylation reaction is catalyzed by enzymes which transfer the ADP-ribose residue of NAD + to various acceptor proteins. The DNA requirement for enzymatic reaction and formation of the unique polymer, poly(ADP-ribose), is the most interesting characteristic of the poly(ADP-ribosyl)ation reaction, catalyzed by poly(ADP-ribose) polymerase or synthetase. The enzyme involved in poly(ADP-ribosyl)ation has been purified from various tissues including calf and pig thymus, rat liver, Ehrlich ascites tumor cells, and HeLa cells. The poly(ADP ribosyl)ation reaction has been shown to correlate with the number of strand breaks present in the DNA which is required by the polymerase for activity. Poly(ADP-ribose) attached to acceptors is the product of poly(ADP-ribosyl)ation reaction. These acceptors include histones, nonhistone nuclear proteins and poly(ADP-ribose) polymerase itself. Poly(ADP-ribose) is hydrolyzed by two major classes of enzymes —namely, (1) poly(ADP-ribose) glycohydrolase, which hydrolyzes the ribose-ribose bond or the ribose-ribose-ribose bond in the branched form of the polymer and (2) phosphodiesterase (or pyrophosphatase), which hydrolyzes the pyrophosphate bonds.
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