While we are all familiar with linear models of DNA and protein-DNA interactions where protein-DNA interactions occur, it would seem, in the absence of any obstruction, such models ignore the fact that most of the DNA is tightly packaged into nucleosomes that involve a close relationship formed by DNA wrapped around a core of histone proteins (Figure 3).87 The actual formation of a nucleosome is 146 bp of DNA with a histone octamer core. The conformation or structure of the histone-DNA configuration regulates gene expression.88
