Poly(ADP-ribose) polymerase: Correlation of enzyme activity with the life span of mammalian species and use of a dominant negative version to elucidate biological functions of poly(ADP-ribosyl)ation

Poly(ADP-ribosyl)ation is an enzymatic posttranslational modification of nuclear proteins occurring in the presence of DNA strand breaks. Thus treatment of cells with DNA-damaging agents (e.g., alkylating agents, γ-radiation, or oxygen free radicals) increases the cellular levels of poly(ADP-ribose). The biological functions and molecular mechanisms of poly(ADP-ribosyl)ation are not fully understood. It appears, however, that poly(ADP-ribosyl)ation can function as a “double-edged sword”, on the one hand by contributing to DNA base-excision repair, on the other hand by acting as a cell suicide mechanism. We compared poly(ADP-ribose) polymerase activity in different mammalian species. Testing permeabilized mononuclear blood cells (MNC), we found a strong correlation of maximal enzyme activity with species-specific life span. Likewise, by applying a poly(ADP-ribose)-specific immunofluorescence method on living γ-irradiated MNC we detected a higher percentage of polymer-producing cells in human versus rat samples. So as to elucidate biological functions of poly(ADP-ribosyl)ation, we have developed a molecular genetic approach to modulate poly(ADP-ribose) metabolism in living cells in culture, i.e., the overexpression of the 42-kDa DNA-binding domain of poly(ADP-ribose) polymerase, causing a trans-dominant inhibition of poly(ADP-ribosyl)ation.