Inducible protein expression in Schneider 2 cells using the operator–repressor system

Schneider line 2 cells, derived from , can be used as a highly versatile gene expression system. Two powerful promoters derived from the (Ac5) and metallothionein (Mtn) genes are available. The Mtn promoter can be used for the inducible expression of heterologous proteins unsuitable for constitutive expression. However, to circumvent using CuSO or CdCl as inducers of the Mtn promoter, we created a modified Ac5 promoter, Ac5LacO, in which two short operator sequences are embedded. Expression from the Ac5LacO promoter was regulated with co-expression of the repressor and IPTG. More than 25-fold induction of firefly luciferase expression was achieved in transient transfection experiments. Furthermore, we demonstrated that the operator–repressor regulatory system functioned in chromosomally integrated cell lines.