p53 Transcriptional activation domain - A molecular chameleon?

The recent structure of human replication protein A (RPA) bound to residues 38 - 58 of tumor suppressor p53 exemplifies several important features of protein-protein interactions involved in transcription and DNA repair. First, the N-terminal transcriptional activation domain (TAD) of p53 is multifunctional and dynamic, showing multiple interactions with partner proteins some of which are modulated by phosphorylation. Second, the binding of partner proteins is coupled with a disorder-to-order transition common to many other transcriptional activation domains. Third, the molecular features of p53 residues 47-58 imitate those of single stranded DNA in their interaction with the oligonucleotide oliogsaccharide-binding (OB) fold of the N-terminal domain of RPA70. This regulated association is implicated in transmitting the DNA damage signal to the p53 pathway of stress response. Here we review the recently reported crystal structure of the p53/RPA70N complex and the mechanism by which ssDNA can provide positive feedback to dissociate p53/RPA complexes. The binding mode and regulatory mechanisms of the p53/RPA70N interaction may represent a general paradigm for regulation of the OB folds involved in DNA repair and metabolism.