EFFICIENT AND INDUCIBLE PRODUCTION OF HUMAN INTERLEUKIN-6 IN CHINESE-HAMSTER OVARY CELLS USING A NOVEL EXPRESSION SYSTEM

High level and inducible production of human interleukin 6 (hIL-6) was achieved using a novel expression system in Chinese hamster ovary (CH O) cells. In this system, the transcription of hIL-6 gene under the co ntrol 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 VP1 6 protein of herpes simplex virus. The transcription of tTA gene, whic h is also under the control of PhCMV-1 promoter, is activated by itse lf via a positive feedback cycle. The expression of both genes is furt her enhanced by potentiating the VP16 transactivating domain of tTA tr ansactivator with pX protein of hepatitis B virus. In the presence of tetracycline, the tTA transactivators can not bind to PhCMV-1 promote r, therefore, the expression of hIL-6 and tTA gene is suppressed, and the pX will not activate basal transcription. In the absence of tetrac ycline, tTA transactivators bind to PhCMV-1 promoter and activate eff icient transcription of hIL-6 and tTA gene, and the transcription is f urther enhanced by pX via VP16 transactivating domain. Using this stra tegy, we isolated a clone (UX1) producing hIL-6 at a rate about 1425 n g/10(6) cells/day. Furthermore, the hIL-6 production is stringently re gulated by tetracycline. This results suggested a novel strategy to es tablish highly efficient, inducible and cell type independent recombin ant protein production system by using an artificial promoter to recru it transactivators and coactivators which can synergistically activate transcription.