33] pac Gene as efficient dominant marker and reporter gene in mammalian cells

Abstract

This chapter discusses the pac gene as efficient dominant marker and reporter gene in mammalian cells. The usefulness of a new dominant marker, such as pac gene, must be evaluated in the frame of other available ones. In view of its versatility, the only sensible comparison should include other antibiotic resistance markers, such as neo or hyg. Some of the advantages of pac over other available selectable markers derive from its ease of use and low cost. Selection with puromycin is fast, because sensitive cells die in the first few days of treatment, and the development of resistant colonies is easy to follow. The cost of the drug required for the selection is about 10 times less than that for G418 and about the same as that for hygromycin. However, the main advantage of pac is the possibility of using it both as a selectable marker and as a reporter gene. It is possible to predict the efficiency of a given construct for transformation by a fast transient expression assay and determination of pac activity. Likewise, it is possible to test pac activity in the different tissues of animals made transgenic for the pac gene. Moreover, proper optimization of the pac gene should make it useful as a marker for gene targeting.