DNA is continously subjected to the damaging effects of environmental genotoxic agents. In the eucaryotic cells, one of the enzymes involved in the DNA repair process is poly(ADP-ribose) polymerase (PARP), which plays a key role in the recognition of single and double DNA strand breaks. We created stable cell lines expressing PARP DNA-binding domain which behaves as a dominant negative mutant. We observed that PARP inhibition has drastic effects on cell survival and cell death by apoptosis, the cell cycle is delayed and cells accumulated in G2+M phase concomitently with an increase in sister chromatid exchanges.
Now we are interested to study the physiological role of PARP using either the PARP null mouse as animal model or derived cell lines (PARP--) as a cellular model. The resistance of different genotoxic agents and the genetic instability will be tested using the mouse skin model of carcinogenesis in the transgenic mice and in the derived cells respectively. To evalueted the role of PARP in the induction of apoptosis by genotoxic agents, thymocytes from PARP know-out mice will be used and their viability will be assessed in the glucocorticoid dependent pathway as well as in the DNA damage p53- dependent pathway. It will be interesting to evaluate the possible connection between the activation of PARP and the induction of the p53, mediated both by DNA strand breaks.