[27] Assembly of nucleosomes and chromatin in Vitro

Publisher Summary This chapter focuses on the assembly of nucleosomes and chromatin in vitro. A wide range of methodological approaches is available for assembling purified DNA into nucleosome cores or more complex forms of chromatin. This chapter considers their relative merits and advises on the selection of methods. In addition, it describes selected protocols in detail. At present there is still a gap between salt reconstitution methods for nucleosome cores and crude, unfractionated cell-free systems that exploit cellular assembly mechanisms. Although we now know the assembly pathway and the identity of assembly factors for the Xenopus egg, it has not been possible to obtain enough of one of them (N 1) to make practical use of the physiological pathway as an assembly method in vitro. Fractionation of crude cell-free assembly extracts has resulted in the identification of proteins that are involved in the cellular process of nucleosome assembly.