ChIP analysis of H3K4 di-methylation before and after treatment of HEp-2 cells with Aza, TSA, or Aza and TSA. Three independent ChIP assays were performed using an antibody that recognizes di-methyl H3K4 at the O6-methylguanine-DNA methyltransferase promoter region. (A) Summary of PCR analyses of ChIP assays. The mean precipitated DNA/input DNA ratios demonstrated on the y-axis represent the relative values of H3K4 di-methylation. Mean H3K4 di-methylation levels are demonstrated by the standard error bars and **P<0.01 vs. control group. (B) PCR assay. Ctrl, prior to treatment; Asa, following treatment with Aza; TSA, following treatment with TSA; Asa + TSA, following treatment with Aza and TSA. ChIP, chromatin immunoprecipitation; H3K4, histone 3 lysine 4; Aza, 5-aza-2′-deoxycytidine; TSA, trichostatin A; PCR, polymerase chain reaction; IP, immunoprecipitated DNA; NAC, no antibody control; IN, input DNA from whole cell lysate.