Improved dual-regulated expression systems for independent control of two different transgenes

Unlike current gene therapy scenarios which focus on single gene replacement or overexpression to substitute for somatic genetic deficiencies, 3rd generation gene therapy strategies will require more complex multiregulated multigene interventions to reprogram or substitute entire regulatory networks and metabolic pathways to cure complex multifactorial human disease. Dual-regulated expression technology enables independent control of two different set(s) of transgenes and represents a first step towards multiregulated molecular interventions in mammalian and human cells. We have designed the dual-regulated expression vector pDuoRex7 which contains divergently oriented streptogramin- (P-PIR) and tetracycline- (PhCMV*-I) responsive promoters. A stuffer fragment of about 600 bp placed between P-PIR and PhCMV*-I prevents any interference between both expression units previously observed with other divergent promoter configurations. pDuoRex7 was engineered to express two marker genes encoding the yellow and cyan fluorescent proteins (pDuoRex8) in response to clinically licensed streptogramin- (PI) and tetracycline (Tet) antibiotics. pDuoRex8 enabled completely independent control of both fluorescent proteins in a variety of mammalian and human cell lines (CHO-K1, NIH/3T3 and K-562 cells) stably expressing a retroviral pTWIN vector (pRetroTwin3) driving constitutive expression of the streptogramin- (PIT) and tetracycline- (tTA) dependent trans activators. The combination of the pRetroTWIN vector series and pDuoRex vector families results in a dual-regulated expression concept with powerful impact on rationale reprogramming of mammalian cells. Here we present the latest generation of the dual-regulated expression technology.