FIG. 4.
Altered chromatin organization of the p21cip1/WAF1 gene locus during HL-60 cell differentiation. Nuclei isolated from control and PMA-treated (2 days) HL-60 cells were incubated with increasing concentrations of MNase or DNase I for 5 min at room temperature. Purified DNA was digested with StyI, and hypersensitive sites were detected by hybridization with a radiolabeled PCR fragment spanning the p21 promoter region (−1500/−1250). The diagram at the left indicates the position of the transcription start site (arrow) and the probe (bar). Numbers at the right indicate positions of nuclease-sensitive sites relative to the transcription start site of the p21 gene.