Out of register: How DNA determines the chromatin fiber geometry

Instituut-Lorentz voor de theoretische natuurkunde, Universiteit Leiden - Leiden, NL-2300 RA, The Netherlands, EU

^a gio@lorentz.leidenuniv.nl

Received: 12 October 2011
Accepted: 2 January 2012

Abstract

We present a model that predicts the geometry of chromatin fibers as a function of the DNA repeat length. Chromatin fibers are widely observed in vitro and are typically posited as the second level of the hierarchical organization of chromatin in the nuclei of cells. We postulate that the major driving force for fiber formation is the dense packing of the underlying DNA-protein spools, the nucleosomes, allowing for fibers with four possible diameters. We show that the diameters observed in experiments on reconstituted regular fibers correspond to the geometries that minimize the elastic energy of the DNA linking the nucleosomes.