INTERACTION OF NON-HISTONE PROTEINS WITH DNA AND CHROMATIN FROM DROSOPHILA AND MOUSE CELLS - SPECIFICITY, ISOLATION AND ANALYSIS OF COMPLEXES

The specificity of the binding of purified non‐histone proteins to DNA has been investigated through two types of experiments. Using a nitrocellulose filter assay at a low protein/DNA ratio, the binding of mouse non‐histone proteins to mouse DNA was twice as great as the binding of mouse non histone protein to Drosophila DNA. The reverse experiment using Drosophila non‐histone protein confirmed the interpretation that some protein. DNA complexes were specific. Protein · DNA complexes isolated by gel filtration chromatography indicated that 20% or 10% of the non‐histone protein was bound to homologous or heterologous DNA respectively. Purified non‐histone proteins bound with lower efficiency (15%) than unpurified but with higher specificity to soluble chromatin than to naked DNA. This binding did not result from an exchange between chromatin non‐histone proteins and purified non‐histone proteins added in excess. DNA‐bound and chromatin‐bound proteins were analysed on polyacrylamide gels. Whereas no major qualitative differences were observed with DNA‐bound proteins, some proteins bound to homologous mouse chromatin were different from those bound to heterologous Drosophila chromatin. These results suggest a possible role of DNA‐bound non‐histone proteins in the regulation of gene expression. Copyright © 1979, Wiley Blackwell. All rights reserved