Figure 3.

Cell-specific plasmid nuclear import. Certain DNA nuclear targeting sequences have been shown to act in cell-restricted manners. In the case of the smooth muscle γ-actin promoter, which acts as a smooth muscle cell DTS, it has been shown that two key factors that are coexpressed in smooth muscle, SRF and Nkx3, form complexes with the plasmid leading to an importin-recognizable complex that can be localized to the nucleus. By contrast, in nonsmooth muscle cells that do not express one or the other of these factors, an importin-binding complex is not formed leading to greatly reduced nuclear import.