FIG. 4.

DNase I-HS mapping in the BeWo, CTB, and STB chromatins. Nuclei from the indicated cells were digested with DNase I, genomic DNA was purified from each sample, and the DNAs were digested with EcoRI and subjected to Southern blot hybridization analysis. The positions corresponding to HSIII, HSIV, and HSV are indicated by arrows at the left. An open arrowhead points to a nonspecific band that was detected before the DNase I treatment (time zero). At the bottom is a diagram of the EcoRI fragment showing the probe position and the sizes of each fragment after DNase I digestion. The results reveal the presence of HSIV and the placenta-specific HS in day 0 and 32 BeWo cells as well as in primary CTBs and STBs. HSIV is absent from the parallel analysis of the human fibroblast line CCDsk-25, which does not express any of the hGH cluster genes. A diagram of the relative fragment sizes is at the bottom.