Peptide-protein interactions suggest that acetylation of lysines 381 and 382 of p53 is important foa positive coactivator 4/p53 interaction

Abstract

The Human transcriptional positive coactivator 4 or PC4 activates several p53 dependent genes. It has been demonstrated that this is a consequence of direct interaction with p53. Previously, we have concluded that PC4 interacts mainly with the C-terminal negative regulatory domain of p53 through its DNA binding C-terminal half. NMR chemical shift perturbation studies with peptide fragments indicated that amino acids 380-386 of p53are crucial for interaction with PC4. This was verified by fluorescence anisotropy and sedimentation velocity studies. A peptide consisting of p53 (380-386) sequence, when attached to a cell penetration tag and nuclear localization signal, localizes to the nucleus and inhibits luciferase gene expression from a transfected plasmid carrying a Luc gene under a p53 dependent promoter. Acetylation of lysine-382/381 enhanced the binding of this peptide to PC4 by about an order of magnitude. NMR and mutagenesis studies indicated that Serine-73 of PC4 is an important residue for recognition of p53. Intermolecular nuclear Overhauser effect placed aspartate-76 in the vicinity of lysine-381, indicating that the region around residues 73-76 of PC4 is important for p53 recognition. We conclude that the 380-386 region of p53 interacts with the region around residues 73-76 of PC4 and acetylation of lysine-382/381 of p53 may play an important role in modulating p53-PC4 interaction and as a consequence PC4 mediated activation of p53 target genes.