Sequence-specific Methyltransferase-Induced Labelling (SMILing) of plasmid DNA for studying cell transfection

Plasmid DNA (pUC19 and pBR322) was sequence-specifically, covalently labelled with Cy3 fluorophores using a newly synthesised N-adenosylaziridine cofactor and the DNA methyltransferase M.TaqI. The fluorescently labelled plasmids were used for transfection of mammalian cells and their intracellular distribution was visualised by epifluorescence and confocal fluorescence microscopy. Although these prokaryotic plasmids do not contain nuclear import sequences, translocation into the nuclei was observed.

SMILing of plasmid pUC19 DNA with a fluorescent aziridine cofactor and a DNA methyltransferase (MTase) (A), transfection (B) and translocation into the nucleus (C). Cy3 fluorescence of labelled pUC19 inside the nucleus (right).Figure optionsDownload as PowerPoint slide