Analysis of DNA-Protein Complexes by Atomic Force Microscopy Imaging: The Case of TRF2-Telomeric DNA Wrapping.

Atomic force microscopy (AFM) is a non-optical microscopy that enables the acquisition at the nanoscale level of a 3D topographical image of the sample. For 30 years, AFM has been a valuable tool in life sciences to study biological samples in the field of tissue, cellular and molecular imaging, mechanical properties, and force spectroscopy. Since the early beginnings of the technique, AFM has been extensively exploited as an imaging tool for structural studies of nucleic acids and nucleoprotein complexes. The morphometric analysis performed on the images can unveil specific structural and functional aspects of the sample, such as the multimerization state of proteins bound to DNA, or DNA conformational changes led by the DNA-binding proteins. Herein, a method for analyzing a complex formed by a telomeric DNA sequence wrapped around the TRF2-binding protein is presented. The described procedure could be applied to the study of any type of DNA-protein complex.