Nucleoprotein: DNA hybridization as a preparative method to isolate specific eukaryotic genes as chromatin

Abstract

Determining the structure and protein composition of chromatin in different states of genetic activity is critical for understanding eukaryotic gene expression. Very little is known about the dependence of chromatin structure upon the sequence or transcriptional activity of the DNA, except in the 2 cases in which particular genes can be isolated from the remainder of the chromatin. In the first case, active ribosomal RNA genes have been shown by EM to contain structurally altered nucleosomes. EM has also shown that SV40 minichromosomes possess a DNA sequence that is devoid of nucleosomes. Clearly, EM is capable of resolving sequence and activity specific features of chromatin, but is limited by the number of genes that have been purified.We have adapted methods of nucleic acid enzymology and hybridization in order to isolate specific genes as intact chromatin. Our methods are DNA sequence specific and thus are generally applicable to isolating a chosen gene at different points in development, differentiation and growth.