UV light-damaged DNA and its interaction with human replication protein A: an atomic force microscopy study.

Area of Science:

• Molecular Biology
• Biophysics
• Genetics

Background:

• DNA damage is a critical factor in genomic instability.
• Replication protein A (RPA) is crucial for DNA repair pathways, including nucleotide excision repair.
• Understanding protein-DNA interactions at the molecular level is essential for comprehending DNA repair mechanisms.

Purpose of the Study:

• To visualize and characterize the structural changes in DNA upon UV damage.
• To investigate the conformational changes of DNA when complexed with human replication protein A (RPA).
• To analyze the interaction between UV-damaged DNA and RPA using high-resolution imaging.

Main Methods:

• Tapping mode atomic force microscopy (AFM) was employed for high-resolution imaging.
• Molecules were immobilized on mica surfaces under near-physiological conditions.
• Quantitative sizing and phase image analysis were used to differentiate between DNA and protein components.

Main Results:

• UV irradiation caused a reduction in DNA contour length, persistence length, and mean square end-to-end distance.
• AFM successfully detected complexes of UV-damaged DNA with RPA.
• DNA was observed to wrap around RPA, leading to a significant decrease in its apparent contour length.
• Phase imaging allowed for discrimination between DNA and RPA within the complexes.

Conclusions:

• UV damage induces significant structural alterations in DNA fragments.
• Human RPA interacts with UV-damaged DNA, inducing conformational changes.
• The wrapping of DNA around RPA is a key feature of this interaction, reducing DNA length and potentially facilitating repair processes.