PHOSPHORYLATION OF POLY(ADP-RIBOSE)POLYMERASE PROTEIN IN HUMAN PERIPHERAL LYMPHOCYTES STIMULATED WITH PHYTOHEMAGGLUTININ

Intracellular phosphorylation of poly(ADP-ribose)polymerase was assaye d in streptolysin-O-permeabilized human lymphocytes. Whereas P-32 inco rporation from [gamma-P-32]ATP into immunoprecipitated enzyme protein was undetectable in resting cells, significant phosphorylation of this enzyme was observed in lymphocytes treated with phytohemagglutinin. T he phosphorylation of poly(ADP-ribose)polymerase in permeabilized cell s was not stimulated by phorbol ester, while phorbol-induced phosphory lation of other proteins and of a specific oligopeptide substrate of p rotein kinase C was observed. However, the specific inhibitory pseudos ubstrate peptide of protein kinase C blocked the phosphorylation of po ly(PLDP-ribose)polymerase induced by phytohemagglutinin. Therefore, a potential role of a member of the protein kinase C family in the phyto hemagglutinin stimulated intracellular phosphorylation of poly(ADP-rib ose)polymerase is conceivable.