Basic components of gene expression plasmids
INTRODUCTION Various plasmid vectors, including expression units for mammalian cells, have been developed for various purposes: to produce valuable proteins, to characterize gene products, to analyze the physiological consequences of overexpressing foreign genes, or to isolate genes of interest by screening recipient cells. Recently, plasmid vectors have also been used for nonviral gene therapy, owing to the development of novel gene delivery methods, such as naked DNA injection, in vivo electroporation, and lipofection. Various modifications have been added to optimize the preexisting plasmid vectors for such in vivo use, although the basic structure of the expression plasmid vectors remains unchanged. In this chapter, an overview of the essential elements of expression plasmid vectors from the viewpoint of their in vivo use will be given.