Liver poly(ADP-ribose)polymerase is resistant to cleavage by caspases

In hepatocytes the DNA repair enzyme poly(ADP-ribose)polymerase (PARP) is n ot proteolytically cleaved during apoptosis. The reason for this was invest igated using a cell-free system that consisted of isolated nuclei from hepa tocytes or thymocytes and cytosolic extracts from hepatocytes or thymocytes undergoing apoptosis. It was found that liver PARP is resistant to proteol ytic cleavage by the caspases present in the cytosolic extracts, Furthermor e, liver PARP was not cleaved by recombinant human caspase-3. It is conclud ed that PARP proteolysis cannot be used as a marker for hepatocyte apoptosi s. (C) 1999 Academic Press.