Bidirectional expression units enable streptogramin‐adjustable gene expression in mammalian cells

Abstract Serious initiatives in gene therapy and tissue engineering require a sophisticated molecular toolbox combining DNA transfer technologies, human‐compatible transcription control systems, as well as compact and robust expression configurations. We have designed several versatile bidirectional expression cassettes that enable coadjustable expression of two desired transgenes in response to clinically licensed antibiotics of the streptogramin class (pristinamycin, Pyostacin®, Synercid®). The bidirectional expression modules consist of a central operator (PIR) that is specific for the pristinamycin‐dependent transactivator (PIT). Streptogramin‐adjustable binding of PIT to PIR transactivates two divergently oriented promoters and initiates transcription of the desired transgenes. The bidirectional expression module can be equipped with different minimal promoters and configured for expression of (1) two functional effector genes, (2) one effector gene and a reporter gene, (3) PIT and an effector gene to form a highly compact one‐vector expression arrangement. We have validated the streptogramin‐adjustable bidirectional expression technology in different basic and autoregulated expression configurations in a variety of mammalian and human cell lines. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 618–625, 2003.