DNASE I-HYPERSENSITIVE SITES IN THE CHROMATIN STRUCTURE OF THE LYSOZYME GENE IN STEROID-HORMONE TARGET AND NONTARGET CELLS

The pattern of DNase I-hypersensitive sites in the chromatin domain of the lysozyme gene was investigated in several organs and cell-types of the chicken. In the cluster of hypersensitive chromatin sites framing the gene, different classes of sites could be discerned: 1) A subset was common to essentially all cells examined except for erythrocytes. Thus several highly nuclease susceptible structures exist around the gene even in its repressed state. 2) Beside the promoter region a second site 6.1 kb upstream of the transcriptional start site of the gene strictly correlates with the transcriptionally active or potentially active state of the gene in both, oviduct cells and macrophages. 3) A final class of sites is specific for the particular lysozyme expressing tissue and the presence of its members distinguish whether the gene is steroid regulated or in a steroid independent active mode.