Fig. 3. Effect of the PWS-SRO on epigenetic features of the AS-SRO. (A) The methylation status of the AS-SRO was determined using DNA from normal tissues and lymphoblasts from the PWS-S family containing either a maternal or paternal deletion of the PWS-SRO. DNA was digested with PstI alone, PstI + HpaII or PstI + BstBI, Southern blotted and probed with the AS-SRO probe (see Figure 1A). Similar results were also obtained for a second family (PWS-U; data not shown). (B) DNase I sensitivity at the AS-SRO region was assayed using nuclei from normal or PWS-S (paternal deletion) lymphoblasts. (C) Histone H4 acetylation and H3(K4) methylation at the AS-SRO region was assayed by ChIP using mononucleosomes from normal lymphoblasts or cells carrying a maternal deletion of the PWS-SRO (PWS-S). No effects of the PW-SRO deletion were observed. See controls in Figure 1D.