Controlled DNA compaction within chromatin: The tail-bridging effect

¹ Max-Planck-Institut für Polymerforschung, Theory Group PO Box 3148, D-55021 Mainz, Germany
² FIAS, JW Goethe-Universität - Max-von-Laue Strasse 1 D-60438 Frankfurt/Main, Germany
³ Instituut-Lorentz, Universiteit Leiden - Postbus 9506 2300 RA Leiden, The Netherlands

Received: 26 August 2005
Accepted: 27 October 2005

Abstract

We study a mechanism underlying the attraction between nucleosomes, the fundamental packaging units of DNA inside the chromatin complex, by introducing a simple model of the nucleosome: the eight-tail colloid, a negatively charged sphere with eight oppositely charged, flexible, grafted chains that represent the terminal histone tails. We demonstrate that our complexes are attracted via the formation of chain bridges and that this attraction can be tuned by changing the fraction of charged monomers on the tails. This suggests a physical mechanism of chromatin compaction where the degree of DNA condensation can be controlled via biochemical means, namely the acetylation and deacetylation of lysines in the histone tails.