High level and inducible production of human interleukin 6 (hIL-6) was achieved using a novel expression system in Chinese hamster ovary (CHO) cells. In this system, the transcription of hIL-6 gene under the control of PhCMV*-1 promoter composed of tetracycline operator sequences and a minimal promoter is activated by a chimeric transactivator (tTA) composed of tetracycline repressor and transactivating domain of VP16 protein of herpes simplex virus. The transcription of tTA gene, which is also under the control of PhCMV*-1 promoter, is activated by itself via a positive feedback cycle. The expression of both genes is further enhanced by potentiating the VP16 transactivating domain of tTA transactivator with pX protein of hepatitis B virus. In the presence of tetracycline, the tTA transactivators can not bind to PhCMV*-1 promoter, therefore, the expression of hIL-6 and tTA gene is suppressed, and the pX will not activate basal transcription. In the absence of tetracycline, tTA transactivators bind to PhCMV*-1 promoter and activate efficient transcription of hIL-6 and tTA gene, and the transcription is further enhanced by pX via VP16 transactivating domain. Using this strategy, we isolated a clone (UX1) producing hIL-6 at a rate about 1425 ng/106 cells/day. Furthermore, the hIL-6 production is stringently regulated by tetracycline. This results suggested a novel strategy to establish highly efficient, inducible and cell type independent recombinant protein production system by using an artificial promoter to recruit transactivators and coactivators which can synergistically activate transcription.
All Science Journal Classification (ASJC) codes
- Biomedical Engineering
- Clinical Biochemistry
- Cell Biology