Chromatin interaction between CTCF sites around the β-globin locus in TSA treated MEL/ch11 cells. (A) MEL/ch11 cells were treated with 25 ng/ml of TSA for 6 h or 24 h. Histone H3 acetylated at K27 was detected by Western blotting in nuclear extract from control cells (Con) and cells treated with TSA. Histone H3 was used as an experimental control. (B) H3K27ac was determined in CTCF sites around the β-globin locus by ChIP. DNA immunoprecipitated by H3K27ac antibodies were quantitatively compared with DNA immunoprecipitated by H3, and then normalized to value in control cells. Normal IgG (IgG) was used as an experimental negative control. (C) Relative cross-linking frequencies was determined between CTCF sites around the β-globin locus in 3C assay as described in Fig 1E . Fragments containing C5 and C3 were used as anchors. Occupancies of CTCF (D) and Rad21 (E) were determined at the CTCF sites by ChIP. Results are presented as the means ± SEM of four to six independent experiments in ChIP and 3C assay. *P