Figure 2

Pre-existing cytosine methylation does not stimulate Dnmt3a in vitro. Plasmid DNA extracted from a Dcm-negative E. coli strain and a Dcm-positive E. coli strain was used in the in vitro ³H-incorporation methylation assay (CPM). The average Dnmt3a activities on each plasmid are summarized in the table above the histogram. Both Dcm+ and Dcm-DNA with no CpG methylation (Un-Me), CpG methylation at 32 HhaI sites (meHhaI) or 40 HpaII sites (meHpaII), and non-CpG methylation at 51 HaeIII sites (meHaeIII) were tested. Dcm+ DNA with non-CpG methylation at a single BamHI site (meBamHI) and Dcm- DNA with non-CpG methylation at 40 MspI sites (meMspI) were also tested. ND represents data point not determined.