A transcriptionally enriched chromatin fraction released by a Mg++ -dependent endogenous nuclease from rat liver

When rat liver nuclei are subjected to endogenous nuclease digestion in the presence of 5 mM Mg++, they release a chromatin fraction containing DNA of well defined fragment lengths and DNA-dependent RNA polymerases. The DNA is enriched 4.4-fold for sequences complementary to cDNA prepared to cytoplasmic poly-A-containing RNA when compared with whole cell DNA. This method of obtaining a transcriptionally enriched chromatin fraction is compared with other reported nuclease methods.