Preparation of Chromatin from Animal Tissues and Cultured Cells

This chapter describes the procedures for the preparation of chromatin from animal tissues and cultured cells that depend on the principles for purification of chromatin from animal cells, starting from either whole cells (direct methods) or purified nuclei. The rationales, advantages and disadvantages, and appropriate uses of these procedures are discussed. In the direct methods of chromatin isolation, the chromatin is isolated from a cell lysate rather than from purified nuclei. The chapter also outlines the methods for the chromatin isolation from nuclei. Purified chromatin preparations contain fragments associated by intermolecular interactions, or long chromatin molecules; further fragmentation (shearing) may be necessary to obtain material suitable for further manipulations. Conditions for storage of purified chromatin have been determined empirically only for certain specific purposes. There is no absolute criterion of purity for chromatin is at the present time. The absolute criteria of structural preservation cannot yet be proposed. The method of choice for chromatin preparation depends heavily on the problem to be investigated.