Our long term goal is to understand how gene expression in higher cells is regulated at the level of chromatin structure, and how this "epigenetic" information is passed on to daughter cells. It may be crucial to know the details of chromatin structure and assembly to understand some aspects of cell biology at the molecular level. One aspect is cell malignancy. There is increasing evidence that normal cells contain genes tha are capable of inducing cell malignancy if these genes are expressed at abnormal levels or at the wrong time. We have found that in solutions rich in the acidic protein, polyglutamic acid, at physiological ionic strength, H1 (or H5) histone (a) induces the sliding apart of closely spaced nucleosomes to give arrays with native-like internucleosome spacing, and (b) significantly increases the supercoiling of DNA in nucleosomes, inducing a topological alteration in chromatin structure. We will use chemical, physical, and biochemical methods to study the origin of the tissue and species specificity of the internucleosome spacing in chromatin and the mechanism by which it arises. We will also study the nature of a strong interaction, we have discovered, between core histones and nucleosomes at physiological ionic strength. Additionally, we will use physical and biochemical methods to measure the superhelical density of DNA in cellular chromatin to a much higher precision than ever before to test my hypothesis that the topology of DNA wrapping in bulk cellular chromatin may be significantly different from that in viral and H1-stripped chromatin.