Methods for Fractionation and Identification of Nonhistone Proteins of Rat Liver Chromatin

Combinations of methods were devised for fractionation and characterization of proteins obtained from rat liver chromatin. The chromosomal proteins were extracted from DNA by treatment with 3M NaCl, 7M urea, or by heating in 1% sodium dodecyl sulfate. The proteins dissociatdd by sodium dodecyl sulfate were fractionated by gel filtration in the presence of the detergent. A number of discrete components, each containing a population of polypeptides of limited heterogeneity with respect to molecular weight, were isolated by this method. Proteins obtained by urea-salt dissociation were initially subfractionated into histone and nonhistone components. The nonhistone proteins were examined by sodium dodecyl polyacrylamide gel electrophoresis and by analytical and preparative isoelectric focusing methods, in an effort to provide reproducible methods for identification of specific families of proteins