Hitoshi Nakagama

Role of Poly-ADP-Ribosylation in Cancer Development

Elucidation of the relationship between poly-ADP-ribosylation and carcinogenesis has markedly progressed by the recent development of knockout or transgenic mice models of poly(ADP-ribose) polymerase (Parp)-1, Parp-2, and poly(ADP-ribose) glycohydrolase (Parg). Parp-1 is involved in base excision repair (BER), single- and |double-strand break repair, and chromosomal stability. These multiple functions explain why Parp-1 deficiency enhances carcinogenesis induced by alkylating agents and that in aged animals. Parp-1 is also involved in transcriptional regulation through protein-protein interaction as a coactivator and/or poly-ADP-ribosylation reaction and is possibly involved in epigenetic alteration during carcinogenesis and modulation of tumor phenotypes. Parp-1-dependent cell-death accompanying NAD depletion may be another important issue in carcinogenesis because this process could lead to the selection of Parp-1 deficient cells due to their survival advantage during cancer growth. The relationship of Parp-2, Parp-3, tankyrase and Parg with carcinogenesis is also discussed.

Poly(ADP-ribose) Preparation Using Anion-Exchange Column Chromatography

Poly(ADP-ribose) polymerase (PARP) polyADP-ribosylates proteins involved in various physiological processes. Accumulated evidence suggests not only protein-conjugated poly(ADP-ribose) but also protein-free poly(ADP-ribose) function in various physiological processes. There are increasing occasions that require protein-free poly(ADP-ribose) to study the function and dynamics of poly(ADP-ribose) in cells. However, the availability of poly(ADP-ribose) is still limited because a chemical synthesis method has not been established. Here, we describe an improved method for the preparation of protein-free poly(ADP-ribose), synthesized enzymatically by using a recombinant PARP-1 expression system and purified with an anion-exchange column chromatography. This method will be useful for biochemical and biological investigation of poly(ADP-ribose) functions and dynamics.