Solution structure and binding specificity of the p63 DNA binding domain.

Area of Science:

• Molecular Biology
• Protein Structure and Function
• Transcription Factor Regulation

Background:

• p63 is a homolog of p53 and part of the p53 family of transcription factors.
• p63 plays a role in apoptosis, differentiation, germ line integrity, and development.
• p63 shares high homology with p53, particularly in the DNA-binding domain (DBD), but differs in DNA binding properties and stability.

Purpose of the Study:

• To determine the solution structure of the p63 DNA-binding domain (p63-DBD).
• To investigate the impact of specific structural differences, like salt bridges, on p63-DBD's DNA binding behavior and specificity.
• To explore p63-DBD's interaction with anti-apoptotic proteins, specifically BclxL.

Main Methods:

• Solution structure determination of p63-DBD using biophysical techniques.
• Site-directed mutagenesis to restore salt bridges in p63-DBD.
• DNA binding assays to assess affinity and specificity for various response elements.
• Co-immunoprecipitation or similar assays to investigate protein-protein interactions (p63-DBD with BclxL).

Main Results:

• The solution structure reveals p63-DBD is less dynamic than p53-DBD.
• Restoring salt bridges in p63-DBD enhances binding affinity to p53-specific DNA sites but not p63-specific sites.
• p63-DBD interacts with the anti-apoptotic protein BclxL through its DNA binding interface, a characteristic previously observed only for p53.

Conclusions:

• Structural differences account for p63-DBD's distinct DNA binding properties and increased stability compared to p53-DBD.
• p63 family members, despite variations in DNA binding specificity and affinity, can activate pro-apoptotic pathways in a tissue-specific manner.
• The interaction of p63-DBD with BclxL suggests conserved mechanisms of apoptosis regulation across the p53 family.