Poly(ADP-ribose)polymerase (PARP) is involved in DNA break signal mechanisms in Trypanosoma cruzi

VILCHEZ LARREA, SALOME; ALONSO, GUILLERMO; FLAWIÁ, MIRTHA M; TORRES, HÉCTOR N; FERNÁNDEZ VILLAMIL, SILVIA

Mar del Plata

Congreso; XLIII Reunión Anual de SAIB; 2007

SAIB

DNA damage signaling is crucial for the maintenance of genome integrity. In higher eukaryotes a NAD dependent signal transduction mechanism protects cells against the genome destabilizing effects of DNA strand breaks. The nuclear enzyme poly (ADP-ribose)polymerase has been implicated in this pathway. We demonstrated that the recombinant enzyme from Trypanosoma cruzi (TcPARP) is strongly activated in presence of nicked DNA and, subsequently, polymers of ADP-ribose (PAR) are attached to PARP itself and to T. cruzi histones. According to this, PAR synthesized could dissociate histones from DNA granting the DNA repairing machinery access to damaged DNA. Nucleic acid damaging agents, such as H2O2, beta-lapachone, methyl methane sulfonate and UV radiations, which trigger different repair mechanisms, were used to study PARP response. The results by using Western blot analysis with anti PAR antibodies showed that PAR synthesis was increased in the presence of these agents. However, when the damage induced led to cell death, the amount of PAR detected decreased. In vivo assays by indirect immunofluorescence confirmed the results obtained by Western blot. We also tested the response in trypanosomes over-expressing PARP. These results are in agreement with the previous proposed mechanisms for PARP in DNA strand break signaling.