Fig. 4

Visualization of DNA methylation changes using BiAD sensor 2. a Representative fluorescence microscopy images documenting that strong BiFC signals are formed upon transfection of the BiAD sensor 2 into HCT116 WT cells (top). In contrast, very low fluorescence reconstitution was observed in DNMT1 hypomorphic HTC116 cells that have globally reduced methylation levels (bottom). A plasmid encoding for NLS-mRuby2 was used to identify transfected cells. b The BiFC signals were rescued in the DNMT1 hypomorphic HTC116 cells by the exogenous expression of active DNMT1 (top) but not of catalytically inactive DNMT1 (bottom). c Quantification of the experiments representatively shown in panels a, b. d Time course of DNA demethylation by treatment of HEK293 cells with 5-aza-dC and recovery. In each sample, the BiAD sensor was transfected 2 days before the cells were fixed for imaging. e Quantification of the experiments representatively shown in panel d. Error bars in all images represent the s.e.m. for two biological replicates (for details cf. Supplementary Tables 2, 6, and 7). Scale bar for all images is 10 µm. The imaging and display setting of the BiFC images shown in panels a, b, and d are identical. In panel d the contrast of the mRuby2 channel was increased to enhance the visibility of transfected cells. This was done with the same settings for all time points