DNA-binding n on hist one proteins: DNA site reassociation

The DHA-binding nonhistone proteins (HHP) have been demonstrated to fractionate the rat genome into protein-bound and unbound DNA sequences. Twenty percent of highly sheared rat DNA |>350 base pair (bp)] can be retained on membrane filters as protein complexes. When extracted from the filter and retitrated with the NHP, a 4- to 5-fold enrichment of binding sites is present in the bound DNA with few, if any, sites de-tected in the unbound DNA. Rat DNA restricted by EcoRI endonuclease can be fractionated by its DNA-binding HHP retention characteristics. Re-association kinetics of the bound restricted sequences indicate that 45.6 % is a subset of total single-copy sequence of the rat genome and 26.9 % is repetitive sequences. Cross hybridization studies indicate the repetitive sequences of the bound DHAare not enriched as much as the slow component of the rat genome. Thus a 4-fold enrichment of a subset of the rat genome has been observed via NHP-DNA interactions