Dynamic interactions of p53 with DNA in solution by time-lapse atomic force microscopy

Area of Science:

• Molecular Biology
• Biophysics
• Atomic Force Microscopy

Background:

• The tumor suppressor protein p53 plays a crucial role in cellular responses to DNA damage.
• Understanding how p53 recognizes specific DNA sequences is vital for comprehending its function.
• Previous methods lacked the resolution to directly observe these dynamic interactions in real-time.

Purpose of the Study:

• To directly visualize the dynamic interactions between the tumor suppressor protein p53 and its specific DNA recognition sequence.
• To elucidate the mechanisms by which p53 locates and binds to its target DNA.
• To investigate the role of divalent cations in facilitating these interactions.

Main Methods:

• Time-lapse tapping mode atomic force microscopy (AFM) was employed to observe interactions in liquid.
• A divalent cation, Mg(2+), was used to immobilize p53 and DNA on a mica surface for AFM imaging.
• AFM allowed for real-time observation of protein-DNA dynamics, including binding, sliding, and diffusion.

Main Results:

• Direct observation of dynamic interactions between p53 and DNA, including dissociation/re-association and sliding.
• Identification of two distinct modes of p53 target DNA recognition.
• Evidence for both direct binding and a two-step process involving non-specific binding followed by 1D diffusion along the DNA.

Conclusions:

• AFM provides unprecedented real-time insights into protein-DNA interactions at the molecular level.
• p53 utilizes multiple strategies, including direct binding and 1D diffusion, to locate its specific DNA binding sites.
• These findings enhance our understanding of tumor suppressor protein function and DNA recognition mechanisms.