Three-Way DNA Junction as an End Label for DNA in Atomic Force Microscopy Studies

Area of Science:

• Biophysics
• Molecular Biology
• Nanotechnology

Background:

• Atomic Force Microscopy (AFM) is crucial for imaging DNA and protein-DNA complexes at the nanoscale.
• Identifying protein locations on DNA is a key challenge in AFM studies.
• End-specific DNA labeling is necessary to distinguish DNA ends.

Purpose of the Study:

• To develop and validate a novel end-specific DNA labeling strategy for AFM.
• To visualize the dynamics of protein-DNA complexes and nucleosome arrays.
• To characterize nucleosome dynamics using high-speed AFM (HS-AFM).

Main Methods:

• Assembly of synthetic DNA oligonucleotides into three-way DNA junctions (3WJ).
• Ligation of 3WJ to create a Y-type structure for end-specific DNA labeling.
• Topographic imaging using Atomic Force Microscopy (AFM) and High-Speed AFM (HS-AFM).

Main Results:

• A 69% yield of successful DNA labeling was achieved using the 3WJ method.
• The dynamic orientation of the Y-end structure was visualized in real-time using HS-AFM.
• HS-AFM revealed significant nucleosome dynamics, including spontaneous unraveling and disassembly.

Conclusions:

• The 3WJ labeling method provides a reliable way to identify DNA ends in AFM studies.
• HS-AFM enables direct visualization of dynamic processes in protein-DNA complexes and nucleosome arrays.
• This approach advances the characterization of nucleosome structure and function.