Exchange of proteins during immunofractionation of chromatin.

The migration and rearrangement of chromosomal proteins during immunofractionation of chromatin has been investigated. Oligonucleosomes from two different chromatins, chicken erythrocyte or rat liver, were mixed with oligonucleosomes from the other species which had been depleted of histones H1/H5 and high mobility group proteins (HMGs). The mixture was treated with buffers of various ionic strengths and immunofractionated on an anti-H1 degrees/H5 or anti-HMG-17 IgG-Sepharose column. The type of DNA, which was retained as the bound fraction on the column, was determined by slot blot analysis using nick-translated repetitive DNA probes from either chicken or rat. The results indicate that in low ionic strength buffers (i.e., below 40 mM NaCl), there is very little exchange of either histone H5 or HMG-17 among nucleosomes and therefore we suggest that it is possible to fractionate nucleosomes according to their antigenic content.