A high-level expression vector for human cells.

We have developed a vector (pSupexp), for high-level expression of genes, that is dependent on transactivation of the human immunodeficiency virus 1 (HIV-1) long terminal repeat (LTR) by the HIV-1 transactivator protein, Tat. The foreign gene, expressed under transcriptional control of the HIV-1 LTR, and the tat gene, expressed under transcriptional control of SV40 early promoter, are expressed from the same plasmid. The vector also has the neomycin resistance-encoding gene (neo), with G418 being used as a dominant selection marker for stable expression. We have cloned the bacterial cat gene into pSupexp and measured transient CAT production in human HeLa and A549 cells. Our results indicate that pSupexpCAT expresses about 25- to 68-fold higher levels of CAT activity as compared to other standard SV40- and Rous sarcoma virus-based vectors, and three- to fivefold more activity than the cytomegalovirus-based vector. Immunoprecipitation of the CAT protein also revealed a high level of production in human cells.