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 Pi p (pristinamycin-induced protein), which is encoded by the streptogramin re sistance operon of Streptomyces coelicolor. Expression of genes placed unde r control of these systems was responsive to clinically approved antibiotic s belonging to the streptogramin group (pristinamycin, virginiamycin, and S ynercid). The versatility of these systems was demonstrated by streptogrami n-regulated expression of mouse erythropoietin (EPO), human placental secre ted alkaline phosphatase (SEAP), or green fluorescent protein (GFP) in dive rse cell lines (BHK, CHO, HeLa, and mouse myoblasts). Analysis of isogenic constructs in CHO cells demonstrated the PipOFF system gave lower backgroun d 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 sele ctive use of different antibiotics to independently control two different g ene activities in the same cell.