Genome Structure — Function from Nuclei to Chromosomes and Nucleosomes

Abstract

Over the past several years the evaluation of the interphase and metaphase chromosomes organization down to the submicron resolution has awakened a great interest (see also the chapters by Belmont, Bradbury, Razin in this volume resulting from the proceedings of a NATO-Advanced Study Institute). Recently, several papers have reported the existence of different structural domains both in mitotic chromosomes and in interphase chromatin [1-7]. These domains are usually referred to as “large scale chromatin organization” and each of them can exhibit different levels of chromatin folding, from the 10 nm nucleofilament to the 30-35 nm fiber [3 6 8-12] and up to the 120-250 nm one [1 5]. It is well known that the folding/unfolding of chromatin fiber at different levels of organization is strictly related to the cell functioning (see also the chapters by Stein, Wolffe, Beato, Gilmour, Turner in this volume), but large uncertainty still exists on the higher order chromatin-DNA structuresin situ.