Interferon production under the control of heterologous inducible enhancers and promoters.

In a search for a useful enhancer to control expression of interferon (IFN) gene in mammalian cells, mouse IFN-beta cDNA ligated 3' downstream to the enhancer-promoter of either mouse metallothionein-I (MT-I) or Drosophila heat shock protein (HSP) was introduced into various cultured cells by calcium-phosphate precipitation method, and the level of IFN transiently produced was compared. In the case of the MT-I enhancer-promoter, low levels of IFN were produced without induction (0-21 IU/ml) and the level increased 5-50 times by heavy metals. In contrast, the basal level of expression of the HSP enhancer-promoter was very low and its expression was increased several hundred to thousand times by heat shock or arsenite. Thus the HSP enhancer-promoter appears to be a potent inducible element with very low basal level and high inducibility.