CELL CYCLE-SPECIFIC PATTERNS OF ADP-RIBOSYLATION AND THE EFFECT OF IONIZING-RADIATION - CYCLIN-A, CYCLIN-B1 AND CYCLIN-D1, CDC2, AND PCNA ARE NOT MODIFIED

The enzyme poly(ADP-ribose)polymerase (PARP) has been implicated in se veral cellular processes by the demonstration of ADP-ribosylation of p roteins which play a role in cellular repair of DNA damage, response t o ionizing radiation and apoptosis. In addition, ADP-ribosylation has been shown to play a role in cell cycle progression. To investigate th e role of ADP-ribosylation in cell cycle progression, we have synchron ized human squamous carcinoma cells (SQ-20B) and examined the changes in the pattern of ADP-ribosylation of proteins through the stages of t he cell cycle. Moreover, synchronized SQ-20B cells were irradiated to determine the effects of irradiation on the patterns of ADP-ribosylati on through the cell cycle phases. These studies showed the ADP-ribosyl ation of 3 specific proteins (70, 68 and 40 kDa) to change through the cell cycle. Furthermore, ionizing radiation altered the ADP-ribosylat ion patterns of these 3 proteins. Using a double antibody method, we d etermined that cyclins A, B1 and D1, cdc2 and PCNA are not modified by ADP-ribosylation.