Poly(ADP-ribosyl)ation in response to DNA damage in Trypanosoma cruzi.

SALOMÉ VILCHEZ LARREA; GUILLERMO D. ALONSO; HÉCTOR N. TORRES; MIRTHA M. FLAWIÁ; SILVIA H. FERNÁNDEZ VILLAMIL

Rosario, Santa Fé

Congreso; VIII Congreso de Protozoologia y Enfermedades Parasitarias; 2008

Sociedad Argentina de protozoologia

The ability of a cell to maintain genome integrity relies on the existence of different pathways of damage recognition, signaling and restoration, adequate for each type of injury. Chromatin dynamic structural changes are crucial in these processes, as they grant the implicated molecular machinery access to the site of DNA damage. In higher eukaryotes, a NAD+ dependent signal mechanism protects cells against genetic instability caused by the presence of DNA single strand breaks. As a main character of this path, the nuclear enzyme poly(ADP-ribose)polymerase (PARP) is able to modify various proteins, including itself, by attaching polymers of ADP-ribose (PAR), altering their ability to interact with DNA and other proteins. In Trypanosoma cruzi only one PARP (TcPARP) has been identified, contrasting to the large PARP family found in other organisms. Previous studies by our group have shown that TcPARP is strongly activated in the presence of sbDNA, triggering an automodification reaction. This indicates that TcPARP might be implicated in DNA damage recognition; our aim is to elucidate its role in this process. Exposure of T. cruzi epimastigotes to UV radiation and H2O2, agents that induce different types of damage, triggers the formation of PAR, as shown by Western blot and IFI, and this raise is concentration-dependent. Moreover, in transgenic parasites bearing an extra copy of PARP, higher levels of PAR are found compared to wild type T. cruzi when exposed to the same damaging conditions. Post-injury survival assays have shown that the inhibition of TcPARP can allow the cells to avoid death when subjected to long UV irradiation times. In vitro, we have demonstrated that TcPARP can ADP-ribosylate histones and AUK1 from T. cruzi, proteins that have been associated with chromatin remodeling processes, which are necessary for damage repair of genomic DNA.