Synthesis and expression of the gene encoding human interleukin-3

To perform structure-function studies of human interleukin-3 (hIL-3) we have synthesized a cDNA encompassing the complete coding region of 484 bp. The strategy we employed involved construction of the cDNA in four sections. Each fragment contained six to ten oligodeoxyribonucleotides. Unique restriction sites were engineered to flank the natural sequence for cloning. Naturally occurring restriction sites were placed internally to these, to allow ligation of the four fragments. The gene was cloned into a modified pJL4 vector and expressed in COS cells. Biological assays of supernatants collected from these cells, for both mature cell function and proliferative activity, showed that synthetic hIL-3 had the same activity as that previously determined for recombinant hIL-3.