Figure 7.

Dnmt3b1 does not cause hypermethylation of the tumor relevant genes Mlh1, Mgmt, Cdkn2b, Apc, Rb1, Vhlh, and Brca1. The methylation status of seven tumor relevant target genes (Mlh1, Mgmt, Cdkn2b, Apc, Rb1, Vhlh, and Brca1) was analyzed by MALDI-TOF mass spectrometry, using two previously identified methylation targets (Sfrp2 and Sfrp4) as positive controls. We analyzed DNA from colon epithelial cells and colon tumors derived from Dnmt3b1-overexpressing mice and uninduced control mice (Dnmt3b1⁺ colon, n = 4; control colon, n = 3; Dnmt3b1⁺ tumors, n = 5; control tumors, n = 4). The average CpG methylation rate was calculated for each amplicon (one amplicon per gene) of each experimental group, and these averages are shown in the bar graph. The data demonstrate that none of these seven genes show signs of increased methylation upon overexpression of Dnmt3b1, whereas methylation of Sfrp2 and Sfrp4 is confirmed, further suggesting that Dnmt3b1 only methylates specific genetic loci.