POLY(ADP-RIBOSE) BINDS TO SPECIFIC DOMAINS OF P53 AND ALTERS ITS DNA-BINDING FUNCTIONS

DNA strand breaks are potential interaction sites for the nuclear enzy me poly(ADP ribose) polymerase (PARP; E.C. 2.4.2.30) and the tumor sup pressor protein p53. Both proteins bind and respond to DNA breaks and both play a role in DNA damage signaling. A temporary colocalization a nd complex formation between these proteins has been demonstrated in m ammalian cells. Here we show that free and poly(ADP-ribose) polymerase -bound ADP-ribose polymers target three domains in p53 protein for str ong noncovalent interactions. The polymer binding sites could be mappe d to two amino acid sequences in the sequence-specific core DNA bindin g domain of p53 (amino acid positions 153-178 and 231-253) and another one in the oligomerization domain (amino acids 326-348). In mobility shift experiments, poly(ADP-ribose) effectively prevented and reversed p53 binding to the palindromic p53 consensus sequence. Additionally, poly(ADP-ribose) also interfered with the DNA single strand end bindin g of p53. The results suggest that ADP-ribose polymers could play a ro le in regulating the DNA binding properties of p53.