Visualization of Artificial Polynucleosomal Constructs with Atomic Force Microscopy

Genetic material of the cell in interphase nucleus is present in a form of a dense DNA-protein structure named chromatin. Structure and dynamics of the single nucleosome, which is the basic unit of DNA compactization, is currently well-studied, although data about the structural and functional organization of higher-level chromatin folding are still scarce. In the present work, a method for visualizing of polynucleosomal constructs using atomic force microscopy is proposed. Polynucleosome assembly on a plasmid with the use of recombinant histone octamers was demonstrated. It was established that glutaraldehyde treatment of a polynucleosome sample before its immobilization on a surface prevents nucleosome disassembly, and their height and width corresponds well with previously obtained data. Plasmids themselves were predominantly in extended conformation, which may help study DNA-protein interactions.