Limited DNase I nicking as a probe of gene conformation.

We have extended the use of pancreatic DNase I as a probe of chromatin structure by exploring the accessibility of an active gene to the introduction of the first single-stranded nick. We show by a target analysis that the beta-globin gene is about 25-fold more sensitive to single-site nicking than is an average sequence in the chicken erythrocyte nucleus or the nontranscribed albumin gene. The sites of initial DNase I nicking are shown to cluster within the transcribed sequence of the beta-globin gene.