Gene therapy and cell modification for clinical applications using plasmid vectors are considered to be a safe and promising strategy. One of the major problems with plasmid vector-based constructs is a rapid decline of transgene expression in cells in vitro and in vivo. An important role of CpG motifs or bacterial vector backbone in expression silencing has been suggested.

CpG motifs，EGFP，expression persistence，luciferase，mesenchymal stem cells，plasmid vec