A phosphorylation-dependent switch in the disordered p53 transactivation domain regulates DNA binding

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• The tumor suppressor p53 is crucial for cellular response to DNA damage.
• Posttranslational modifications, like phosphorylation, tightly regulate p53 activity.
• Thr55 in the N-terminal transactivation domain acts as a phosphorylation-dependent regulatory switch.

Purpose of the Study:

• To elucidate the molecular mechanism by which Thr55 phosphorylation modulates p53 DNA binding and transcriptional activity.
• To understand how p53 activity is controlled during different stages of the DNA damage response.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Fluorescence spectroscopy

Main Results:

• Thr55 phosphorylation inhibits p53 DNA binding by promoting interactions between the AD2 motif and the DNA-binding domain (DBD).
• Phosphorylation abolishes cooperativity, leading to initial dimer binding and subsequent tetramer dissociation, resulting in a bell-shaped binding curve.
• Additional phosphorylation at Ser46 and the proline-rich domain (PRD) further fine-tune this autoinhibition.

Conclusions:

• The phosphorylation status of Thr55 is a key determinant of p53's DNA-binding affinity and transcriptional output.
• This mechanism allows for dynamic control of p53-mediated transcriptional programs, enabling both activation and termination.
• Understanding Thr55 regulation provides insights into p53's role in DNA damage response and cancer.