Fig. 3.

PARP-1 catalytic activity is required for PARP-1 to be modified with ³²P-radiolabel in the presence of HPCF. PARP-1, PARP-1 (H862A), or PARP-1 (E988A) (each at 50 pM) and [³²P-adenylate] NAD (50 μM) were incubated 25 °C in the absence or presence of HPCF (50 μg/ml). After 15 min, the samples were scored for ³²P-incorporation by scintillation counting of TCA-precipitated material. The data are presented as fold-increase in ³²P-radiolabel incorporation versus a control conducted with wild-type PARP-1 and [³²P-adenylate] NAD in the absence of HPCF. Statistical significance was calculated for differences in ³²P-incorporation between samples containing HPCF and the control lacking HPCF.