摘要：

A cell has more than one option when it comes to protecting itself and surrounding tissues against the repercussions of DNA damage. One approach is repair; another is to cut losses and sacrifice itself. Poly(ADP-ribose) polymerase-I (PARP-I) is a nuclear protein that appears to play a hand in both DNA repair and cell death. "PARP is doing a very simple job," says Csaba Szabo, chief scientist at Inotek Pharmaceuticals in Beverly, Mass. "It's sticking these poly(ADP-ribose) polymers onto things." Activated by DNA nicks and breaks, PARP-I uses NAD+ to synthesize polymers of ADP-ribose onto various nuclear proteins, including histones, topoisomerases, DNA polymerases, DNA ligases, and transcription factors, as well as to itself, and in doing so, opens up chromatin structure for access by repair enzymes. But depending on the degree of enthusiasm with which it undertakes its "simple job," PARP can push a cell towards recovery or death.

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