Poly(ADP-ribosyl)ation of p53 during apoptosis in human osteosarcoma cells

Spontaneous apoptosis in human osteosarcoma cells was observed to be associ ated with a marked increase in the intracellular abundance of p53, Immunopr ecipitation and immunoblot analysis revealed that, together with a variety of other nuclear proteins, p53 undergoes extensive poly(ADP-ribosyl)ation e arly during the apoptotic program in these cells. Subsequent degradation of poly(ADP-ribose) (PAR), attached to p53 presumably by PAR glycohydrolase, the only reported enzyme to degrade PAR, was apparent concomitant with the onset of proteolytic processing and activation of caspase-3, caspase-3-medi ated cleavage of poly(ADP-ribose) polymerase (PARP), and internucleosomal D NA fragmentation during the later stages of cell death. The decrease in PAR covalently bound to p53 also coincided with the marked induction of expres sion of the p53-responsive genes bar and Fas, These results suggest that po ly(ADP-ribosyl)ation may play a role in the regulation of p53 function and implies a regulatory role for PARP and/or PAR early in apoptosis.