One-Dimensional Search Dynamics of Tumor Suppressor p53 Regulated by a Disordered C-Terminal Domain

Area of Science:

• Molecular Biology
• Biophysics
• Genetics

Background:

• The tumor suppressor p53 protein is crucial for cellular responses to DNA damage.
• p53 binds specific DNA sequences to regulate gene expression.
• Cellular conditions, including divalent cation concentrations, can affect protein-DNA interactions.

Purpose of the Study:

• To investigate how p53 maintains efficient DNA target searching under varying divalent cation concentrations, specifically Mg²⁺.
• To elucidate the roles of different p53 domains in DNA binding and search dynamics.

Main Methods:

• Preparation of two p53 mutants: CoreTet (core + tetramerization domains) and TetCT (tetramerization + disordered C-terminal domains).
• Investigation of equilibrium and kinetic DNA dissociation.
• Single-molecule fluorescence measurements to analyze 1D diffusion dynamics along DNA at various Mg²⁺ concentrations.

Main Results:

• CoreTet binding to DNA weakens significantly with increasing [Mg²⁺], while TetCT binding is less affected.
• CoreTet diffusion along DNA exhibits both fast and slow modes, with their ratio highly dependent on [Mg²⁺].
• TetCT diffusion primarily uses the fast mode, and the disordered C-terminal domain associates with DNA independently of [Mg²⁺].

Conclusions:

• The disordered C-terminal domain of p53 is key to maintaining DNA search efficiency across different Mg²⁺ concentrations.
• p53 modulates its quaternary structure to adapt its DNA search mechanism to varying cellular Mg²⁺ levels.
• These findings provide insights into the dynamic regulation of p53's function in DNA binding and target recognition.