Purification of recombinant Drosophila NAP1

The goal of chromatin assembly procedures is to prepare extended nucleosomal arrays from cloned DNA templates and purified core and linker histones. The assembled chromatin should be highly defined in its protein content and resemble bulk chromatin isolated from living cell nuclei in terms of periodicity and nucleosome positioning. This protocol describes the preparation of the NAP1 chaperone protein for use in chromatin assembly reactions. In this method, Sf9 cells are infected with an HIS6-DNA-1-expressing baculovirus. The NAP1 is then purified by nickel affinity chromatography, followed by anion-exchange chromatography.