Diversity in DNA recognition by p53 revealed by crystal structures with Hoogsteen base pairs

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The tumor suppressor protein p53 plays a critical role in cellular responses to DNA damage.
• p53 functions by binding to specific DNA sequences as a tetramer.
• Previous studies showed p53 binding to DNA with standard Watson-Crick base pairing.

Purpose of the Study:

• To elucidate the high-resolution structures of p53 core-domain tetramers bound to DNA targets with contiguous half-sites.
• To investigate the role of noncanonical base-pairing geometry in p53-DNA interactions.
• To understand how DNA structure modulation affects protein-DNA binding affinity.

Main Methods:

• High-resolution crystal structure determination of p53-DNA complexes.
• Structural analysis of protein-DNA interfaces.
• Computational analysis of DNA helix modulation and electrostatic potential.

Main Results:

• Novel crystal structures reveal p53 tetramers bound to DNA with contiguous half-sites.
• Noncanonical Hoogsteen base-pairing geometry was observed at central A-T doublets.
• Hoogsteen geometry significantly altered B-DNA helix shape and electrostatics.
• Contiguous DNA and Hoogsteen pairing enhanced protein-DNA and protein-protein interactions.

Conclusions:

• Hoogsteen base-pairing geometry represents a novel mode of sequence readout for p53.
• The findings provide a mechanism linking DNA spacer length to p53 binding affinity.
• This study expands the understanding of sequence-specific protein-DNA recognition.