Milea Timbergen

103 Figure 3. DNMT1 is not co-precipitated with wild-type or mutant CTNNB1 (β-catenin). HEK293T cells were transfected with plasmids driving the expression of FLAG-tagged wild-type β-catenin (WT) or FLAG- tagged mutant versions of β-catenin (T41A; S45P; Exon 3 deletion mutant; K335I). As a control cells were transfected with the empty vector. At 48 h post-transfection cell lysates were prepared from which the FLAG- tagged β-catenin variants were immunoprecipitated. Western Blot analysis was used to examine DNMT1, β-catenin and β-actin protein expression in the total lysates and immunoprecipitates. Discussion DNA methylation patterns are a good representation and reflection of molecular changes in the early stages of human cancer. The correlation between cancer and aberrant methylation patterns are described by various studies 22, 23, 26 . DNA hypomethylation of gene promoter regions is usually associated with tumour formation, activation of oncogenes and chromosomal instability 33, 34 . In addition, DNA hypermethylation of gene promoter regions may alter gene expression and can cause tumour suppressor silencing and promote cancer progression 35 . Also, gene body methylation is a widespread phenomenon, however, its functional consequences are less clear 36, 37 . There is experimental evidence that gene body methylation is also associated with transcriptional activity and can affect gene expression 3, 38 . Aberrant 4