Mononucleosomes can be reconstituted on 197-bp or 147-bp radiolabeled DNA fragments (see Notes 1 and 2) either by salt dialysis using purified core histones or by histone octamer transfer from donor H1-depleted chromatin. Usually, reconstitution yields naked DNA and DNA with mono-, di-, and trinucleosome cores.
The efficiency of reconstitution and the number of nucleosome cores on a labeled DNA fragment can be analyzed by agarose gel electrophoresis.
Reconstituted oligonucleosomes can be separated by sucrose gradient centrifugation on the basis of the number of histone octamers bound to a DNA fragment. We use 5% to 20% (w/v) linear sucrose gradients to isolate dinucleosomes from unreconstituted DNA, free histones, mono- and trinucleosomes.
For a detailed introduction to assays of nucleosome assembly and the inhibition of histone acetyltransferase activity, please go here: "http://www.natureprotocols.com/2007/07/30/assays_of_nucleosome_assembly.php":http://www.natureprotocols.com/2007/07/30/assays_of_nucleosome_assembly.php