Streptogramin-based gene regulation systems for mammalian cells

Here we describe repressible (PipOFF) as well as inducible (PipON) systems for regulated gene expression in mammalian cells, based on the repressor Pip (pristinamycin-induced protein), which is encoded by the streptogramin resistance operon of Streptomyces coelicolor. Expression of genes placed under control of these systems was responsive to clinically approved antibiotics belonging to the streptogramin group (pristinamycin, virginiamycin, and Synercid). The versatility of these systems was demonstrated by streptogramin-regulated expression of mouse erythropoietin (EPO), human placental secreted alkaline phosphatase (SEAP), or green fluorescent protein (GFP) in diverse cell lines (BHK, CHO, HeLa, and mouse myoblasts). Analysis of isogenic constructs in CHO cells demonstrated the PipOFF system gave lower background and higher induction ratios than the widely used tetracycline-repressible (TetOFF) expression systems. The streptogramin-based expression technology was functionally compatible with the TetOFF system, thus enabling the selective use of different antibiotics to independently control two different gene activities in the same cell.