New approaches for the high-level expression of human interleukin-2 cDNA in Escherichia coli

We constructed several expression plasmids of human IL-2 gene, some of which directed high-level synthesis of mature IL-2 protein in E. coli. In all the plasmids reported here, we installed the E. coli trp promoter and SD sequence upstream of the IL-2 cDNA. When DNA sequences containing the rho-independent transcription terminator such as those involved in the trpA and lpp gene were inserted downstream of the IL-2 cDNA sequence, the expression level of the IL-2 gene increased up to 5-fold. Moreover, the deletion of either the whole region including A-T and G-C tails or a part of the 3' non-coding sequence resulted in further increase of the expression of the IL-2 gene up to 500-fold. The mature IL-2 produced in E. coli exhibited biological and immunological activities indistinguishable from those of purified IL-2 from a human T cell line, Jurkat-111. The manipulations described here may be useful for the high-level expression of eukaryotic genes in E. coli.