CONICET | Buscador de Institutos y Recursos Humanos

Trypanosoma cruzi is the etiologic agent of Chagas´ disease, a public health problem that affects over 28 million people in South America. This parasite has a complex life cycle, each stage requiring differential expression of certain genes. The mechanisms that control such expression remain unclear. Chromatin remodelling by protein modifications, including poly(ADP-ribosyl)ation, may be important for this process. Our aim is to study the role of PARP in chromatin dynamic structural changes throughout the cell cycle as well as in damage recognition, signaling and restoration of the genetic and epigenetic information in trypanosomatids. We cloned the single PARP present in T.cruzi (TcPARP) and demonstrated that it is strongly activated by nicked DNA and attaches polymers of ADP-ribose (PAR) to itself and to T.cruzi histones. The enzyme is expressed in the amastigote, epimastigote and trypomastigote parasite stages. In synchronized cells, PARP content seems to be constant during cell cycle but PAR levels attached mainly to PARP are high at G1 phase, then decrease to rise again in the late S and G2 phases. Regarding its role in DNA repair, DNA damaging agents that trigger different repair mechanisms induce PAR synthesis in the parasite nucleus. By Western blot and IFI using antiPAR antibodies, we showed a concentration-dependent increase in the level of PAR when H2O2 was used in a 3-3000 µM range. UV exposition during 1 to 5 minutes showed PAR formation in parasites, which were able to grow in culture, but longer exposition times induced cell death and the amount of PAR detected decreased. We are currently looking for proteins involved in cell cycle and DNA repair in this organism, which could be PARP targets. The results presented here are a first approach and deserve a much deeper study in order to elucidate the role of PARP in trypanosomatids.