FIG. 5.

Differences in the restriction enzyme accessibility at the H4/n gene in proliferating and differentiated HL-60 cells. (A) Nuclei were isolated from proliferating (P) and differentiated (D; 2 days of PMA treatment) HL-60 cells and digested with 75 to 500 U of restriction enzyme/ml. Purified DNA was digested to completion with PstI and BamHI. Products were detected by Southern blotting using the XbaI/PstI probe. (B) The relative nuclease sensitivity of restriction enzyme sites was quantitated, and the intensities of radioactive bands were used to calculate the percentage of DNA digested. The relative positions of the restriction enzyme sites are shown in the diagram. The asterisk indicates statistical significance at the P ≤ 0.015 level using the two-tailed paired t test.