Nucleosome mono-, di-, tri-, and tetramers from chicken embryo chromatin

Abstract

The fractionation of gram quantities of nuclease digested chromatin from chicken embryos into nucleosome mono-, di-, tri-, and tetramers is described in detail. Each of these nucleosomal species contains a fraction soluble in 0-1 M KC1 that decreases with increasing repeat number. Less histone H1 is associated with the nucleosome fractions soluble as compared to the respective fractions precipitated in 0.1 M KC1. Thermal denaturation profiles of the four nucleosomal species are monophasic. The same Tm of 78 degrees C has been determined for the KC1-soluble nucleosomes and for the KC1-insoluble monomer. The Tm of the KC1-insoluble oligomers is 79.8 degrees C. Multiphasic melting curves were recorded for nucleosomal material that was concentrated by lyophilisation or stored at 4 degrees C in 0.25 mM EDTA. Total nucleosome mono-, di-, tri-, and tetramers (consisting of both the fraction soluble and insoluble in 0.1 M KC1) have been analyzed concerning their sedimentation, diffusion, partial specific volume, and molecular weight and compared with the sedimentation and molecular weight data of KC1-soluble nucleosome mono- and tetramers.