Effects of DNA damage on the interaction of DNA binding domain in poly (ADP-ribosyl) polymerase with DNA

Abstract

Poly (ADP-ribose) polymerase [PARP; $NAD^+$ ADP-ribosyltransferase; EC 2.4.2.30] is activated by DNA strand breaks. Because DNA breaks are produced by many genotoxic agents, the function of chromatin associated PARP has been implicated to participate in the process of DNA repair. Electrophoretic mobility shift assay was carried out to define the binding properties of PARP to the damaged DNA. Oligonucleotide as short as 10mer was a good substrate to make a shift-up band. Competitive inhibition experiment with single-strand or supercoiled DNA suggested a positive correlation between binding capacity of PARP with DNA and catalytic activity to polymerase ADP-ribose unit. The substrate DNA containing photoadduct showed markedly decreased affinity while a single base pair lesion with $O_6$-Me-dG did not cause any significant decrease in the binding affinity. These results indicate that maintenance of B-form helix conformation at the region of binding site is required for proper function of PARP. Data also suggest that PARP may participate in DNA polymerization and ligation step during celluar repair process