Effect of 5-FU treatment on histone H3 modifications. (A) Decreased histone H3 modifications by 5-FU in cells are not MMR dependent. Expression of acetyl-histone H3 at lys 9, pan-methyl-histone H3 expression at lys 9 and phospho-histone H3 at ser 10 after 5-FU treatment were greatly decreased compared to each DMSO control regardless of status of MMR deficiency. SW480, HCT116 + chr 3 and HCT116 cells were used as MMR-proficient, hMSH3-/- and hMLH1-/- cells, respectively. (B–D) 5-FU treatment inhibits several histone H3 modifications at various sites in MMR-proficient cells. Expression of acetyl histone H3 at lys 9, 18 and 23 (B), expression of dimethy-histone H3 at lys 4, 9, 27, 36 and 79 (C) and expression of phospho-histone H3 at thr 3 and 11 and ser 10 (D) were determined in SW480 and HT29 cells. Note that 5-FU significantly decreased expression of histone H3 modifications at different sites in both cell lines compared to DMSO except acetyl-histone H3 expression at lys 18 in HT29 cells.