Single-stranded DNA mimicry in the p53 transactivation domain interaction with replication protein A

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Protein-protein interactions are critical for cellular responses to DNA damage.
• Replication protein A (RPA) and p53 are key players in DNA damage signaling pathways.
• Understanding the structural basis of RPA-p53 interaction is essential for deciphering DNA damage response mechanisms.

Purpose of the Study:

• To elucidate the crystal structure of the RPA70N/p53N complex.
• To characterize the mechanisms modulating the RPA/p53 interaction using NMR spectroscopy.
• To provide insights into the threshold response of DNA damage signaling.

Main Methods:

• X-ray crystallography was used to determine the structure of RPA70N bound to p53N (residues 37-57).
• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to characterize binding and competition mechanisms.
• Structural analysis of protein domains and their conformational changes upon binding.

Main Results:

• The crystal structure revealed that RPA70N adopts an oligonucleotide/oligosaccharide-binding (OB) fold.
• The p53 N-terminal domain (p53N) forms two amphipathic helices (H1 and H2) upon binding to RPA70N.
• NMR data showed that single-stranded DNA (ssDNA) and a phosphomimetic peptide can compete p53N from the RPA binding site.

Conclusions:

• The H2 helix of p53 structurally mimics ssDNA binding to the RPA OB fold.
• Modulation of the RPA/p53 interaction can occur through competition by ssDNA or phosphorylated RPA32N.
• These findings suggest a mechanism for DNA damage signaling that explains a threshold response.