Suppression of H3K27-MT, EZH2, but not of H3-K9 MTs, induced cell cycle arrest in immortalized and transformed cells. A.B. BrdU incorporation assay reveals DNA synthesis reduction by interfering with EZH2, a H3K27MT in both immortalized (A) and Ras transformed human bronchoepithelial cells (B). Suppression of H3K9 MTs, SETDB1, G9A or SUV39H did not affect the DNA synthesis level in either of these cells. The experiments are done in triplicates and repeated twice. Columns, averages; bars, SD. C.D. Cell cycle analyses show total S phase reduction only after the treatment of siRNA for H3K27 MT, EZH2 suppression, compared to the cells treated with siRandom non-targeting control both in immortalized (C) and Ras transformed bronchoepithelial cells (D), consistent with the finding on BrdU incorporation assays. None of the other cells interfered with other HKMTs shows total S phase reduction, again consistent with BrdU incorporation assays. (E) Representative cell cycle analysis for the Ras transformed cells treated with siRandom negative control (left panel) and the cells treated with siEZH2 (right panel).